Waters of Producing Fields in the Rocky Mountain Region

By JAMES G. CRAWFORD,' MDlBER AHlIE

(Denver ~jeeting, September 1947)

ABSTRACT is tics peculiar to each field, each subsurface zone and each province. Criteria useful in CORRELATION of water with its reservoir zone or formation has been one of the applica postulating the occurrence of oil or gas in tions of oil-field water analysis of greatest direct one province completely fail when applied value to the petroleum engineer. The water in to another, and data carefully prepared and each producing zone tends to have diagnostic analyzed from one field may be actually characteristics by which it can be distinguished misleading when applied to another. from every other water above or below that Correlation of water with its reservoir zone in that immediate vicinity. Representative zone or formation has been one of the Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 analyses of oil-field waters from producing oil applications of oil-field water analysis of and gas fields in the Rocky Mountain region greatest direct value to the engineer. The are included, and the diagnostic characteristics concentrations and characteristics of the are discussed briefly. It is concluded that the generally dilute nature of Rocky Mountain oil waters are essential to the engineers and field waters is a result of dilution by meteoric geologists making interpretations of elec waters, and that there is no relationship be tric logs in this region. The behavior of tween presence or absence of commercial oil water under conditions of reservoir tem and the character of water in a structure. perature and pressure is dependent to a great degree upon its concentration and INTRODUCTION characteristics, and thus important to the The study of waters associated with oil reservoir engineer. With the advent of and gas began more than 50 years ago and secondary recovery methods in the Rocky has been well recognized by operators, Mountain region the characteristics and engineers, and geologists for about 30 treatment of water will become increasingly years. It appears unnecessary at this time important. to recite the history of oil-field water analysis; suffice to say that it has proved PREMISES UPON WHICH CORRELATION Is its worth many times to the production BASED engineer suddenly confronted with water A brief review of the geochemical history problems in producing oil and gas wells. of oil-field waters will suffice to present the Chemists and geologists have studied premises upon which correlations of the the possible origin of these waters and as waters are based. Sedimentary rocks which yet the subject is unsolved in many are now stratified were first sediments in important phases. There are both local and seas, lakes and streams. These sediments regional problems connected with the ex were filled interstitially with connate planation of concentrations and character- water. With burial the sediments were com pressed and consolidated, integrated and Manuscript received by the office of the Institute Sept. I, 1947. Issued as TP 238,3 in indurated into bed rock and much of the PETROLEUM TECHNOLOGY. May 1948. connate water was dispelled. Following the • Chemical Engineer, Chemical Laboratories, Inc., Casper, Wyo. formation of bed rock the strata were sub- 264 JAMES G. CRAWFORD

jected to many changes, such as very deep above or below that zone in that immedi burial at zones of moderately high tem ate vicinity. The soundness of the premise peratures, and tilting and uplifting with is attested by the experience of the author erosion along exposed scarps, valleys and who has not found a violation in more than canyons. Exposed, eroded porous strata I8 years' work of correlating waters in the were invaded by ground water of meteoric Rocky Mountain region. origin whereby connate water has been displaced and diluted. Contiguous to ALTERATIONS SUBSEQUENT TO deeply incised streams under conditions of ENTRAPMENT arid climate the ground water may have It is doubtful if there has been appreci been lowered whereby connate water was able change in chemical characteristics of eliminated from strata several thousand water trapped in structures devoid of feet thick. These geologic and geochemical hydrocarbons. It is assumed that ground changes were slow and gradual over millions waters cannot infiltrate to any extent and of years. As a result the composition of that chemical changes after accumulation Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 water from a given zone appears very are negligible. In structures containing oil nearly constant throughout the economic or gas, though, a different picture is life of an oil or gas field. The amount of presented. Connate water has had the . connate water in a given bed and the opportunity of reacting with hydrocarbons amount of interstitial water subsequently and there is no doubt that alteration has migrated into a given bed provide the con occurred in many instances. The reactions centrations and characteristics peculiar to between hydrocarbons and different types each locality or geological province. of water are not thoroughly understood, The wide range in connate waters can but it is very well established that sulphate be shown by reciting that some brines in oil reduction, under certain conditions, does fields of other regions have concentrations take place. The equation involving this nine times that of normal sea water of reaction is 35,000 ppm total solids. In the Rocky Mountain region the greatest concentra tion in producing fields is IOO,OOO to I50,- It is thought that the reaction is aided or 000 ppm occurring in the Weber sand at initiated by anaerobic bacteria. The Rangely; the most dilute is 200 ppm total products of the reaction are both chemically solids in the Tensleep sand at Dallas, active; the sulphides may be precipitated Derby, Lander and Black Mountain. The from the solution as metallic salts and be concentration and chemical character come part of the strata; the carbon dioxide istics of a connate water may be more may escape as a gas, or become fixed in the nearly its original properties than has often aqueous solution as a bicarbonate. Pre been considered in earlier studies. The sea sumably this reaction would result in a water may have been modified by meteoric water containing little, if any, sulphate and waters at the time deposition was oc an excess of bicarbonate. curring. Thus, variations in oil-field waters The occurrence of hydrogen sulphide in do not always indicate alterations subse the oils and waters of pre-Triassic strata is quent to origin, and low concentration does striking. These waters occur in, or contact, not always indicate hydraulic flushing or limestone beds and are for the most part ground water infiltration. sulphate waters. It is believed that associ The important point is that water con ation with hydrocarbons has resulted in tained in each producing zone tends to have partial reduction of the sulphates in the diagnostic characteristics by which it can water, and the fact that the oil and water be distinguished from every other water both contain hydrogen sulphide gas is some 266 WATERS OF PRODUCING FIELDS IN THE ROCKY MOUNTAIN REGION

evidence that active reduction is occurring the three oil sands, other water-bearing at the present time. It is noticeable that lenticular sand bodies. The operators have waters of these older formations in barren been conscientious about testing every structures often carry small to moderate sand body and obtaining water samples in amounts of hydrogen sulphide, the reduc an effort to correlate these lenticular sands tion being accomplished by carbonaceous from well to well. The analyses of these matter in the stratum. waters are extremely variable. They have The pre-Triassic waters do not contain concentrations ranging from 1500 to much alkalinity and it was difficult to 32,000 ppm total solids and a chloride con accept active reduction in these waters tent varying between 65 and 20,000 ppm. until one could account for the carbon The water is saline, the salinity being dioxide liberated by the reaction. For every caused almost entirely by chloride. The mol of sulphate reduced two mols of carbon erratic nature of these waters points to the dioxide are formed, and one would expect lack of continuity in the sands. Three a high alkalinity in the waters in which this typical analyses of Wasatch water in this Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 reaction occurred. Recent work on the field are given in Table I; No. I is from the natural gases of this region by the author first oil-producing sand. has shown that the older formations quite TABLE I-Typical Analyses oj Wasatch often yield gases containing notable quan Water, Hiawatha Field tities of carbon dioxide, and the source

might well be sulphate reduction. No. I No.2 NO.3

OIL-FIELD WATERS OF COLORADO Na ...... 1.751 5.873 10.594 Ca ...... 94 30 903 Colorado has produced only about 6 pct Mg ...... 40 44 409 S04 ...... 867 18 162 of the total oil in the Rocky Mountain Cl...... 2,009 7.889 18.939 region but with the recent development of CO, ...... o 146 o HCO, ...... 575 2,005 115 T.S ...... 5,044 14.987 3 1 .064 the Weber formation in the Rangely field pH ...... the state is occupying a more important Source ...... DST Bailer Storage tank Depth ...... 2.234-2.287 3.350 2.3 10-2,354 place in oil production. The correlation of oil-field waters in this state is hampered by the lack of analyses, probably due to its Iles Dome former small oil production; most of the The principal oil production at nes analyses are scattered and with the excep comes from the Sundance formation with a tion of two fields in the state no serious few wells producing from the Mancos shale effort has been made to survey thoroughly and the basal sandstone of the Morrison any particular area. formation. The zones which are capable of The following analyses are believed producing water and, therefore, enter into representative for the strata and fields be production problems are the water-bearing low. Only the producing fields are con Dakota sandstone, the Morrison formation sidered. When available, pH, depth and and the Sundance formation. These waters source of sample are given. can be differentiated, one of the important correlation points being the sulphate in the Hiawatha (East and West) Morrison water, the Dakota and Sundance Oil and gas production at Hiawatha waters containing only tl aces or none at comes from three lenticular oil sands be all. The Sundance water I as been sampled tween depths of 2032 to 2512 ft in the and analyzed more than any other water in Wasatch formation of lower Eocene age. the field; it varies, ranging from a low of The formation in this area is more than about 1500 to as high as 4000 ppm total 5000 ft thick and contains, in addition to solids, the higher concentrated water being JAMES G. eRA WFORD associated with oil. A deep test in this field sand conditions similar to Hiawatha. Two in 1947 obtained a sample of Weber water, producing zones have been logged at its dilute nature indicating poor possi Powder Wash, one at 3087 to 3113 ft called bilities for production in this zone. Typical the Stewart and the other at S014 to S023 analyses of these waters are as shown in ft called the Allen sand, \Vater analyses Table 2. from this field bear a striking similarity to M offal Dome analyses from the Hiawatha field and their erratic nature indicates lenticularity and Production at Moffat is from the Dakota discontinuity of the sand bodies. Three sandstone and Sundance formation and typical analyses of 'Nasatch waters from like Iles, there are three waters that enter this field are as shown in Table 4. TABLE 2-Typical A liillyses of IV alers of TABLE 4-Typical A nalyses of Wasatch Iles Dome tvaiel', Power TV ash Field Sun- Dakota Morrison \i\'eber dance AO. I ~o. 2 ~o. 3 Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021

--- I -- -~------Na ... 434 1,382 1,307 741 ~a .... 1,978 6,715 10,823 Ca ...... II 0 0 0 Ca .... 26 549 660 Mg ..... tr 0 0 0 t-.!g .. 0 51 195 SO, ..... tr 424 0 II4 SO .. tr 181 819 CI ...... 38 257 258 337 CI ... 2,341 11,172 17,735 CO, .... 0 121 0 210 CO, .. 57 0 0 HCO,. 1,120 2,440 3,025 815 HCO, ... 1,185 295 160 T.S .. ' 1,034 3,384 3,053 1803 T.S .... 4,98 4 18,813 30.3II pH ..... pH .... Source . . Flow line Stock tank Well· Swab Source DST DST DST head Depth. 5,035-5,075 5,273-5,283 4,191-4.209 Depth .. 2.910-3,050 3-457-3,462 4,572-4,61 9 production problems. Only a few analyses Rangely of these waters are available to the author, This is one of the early Rocky Mountain thus the probable change in concentration fields and oil production has come from the over the structure is not known. The Mancos shale at the relatively shallow waters of this field bear a certain similarity depths of 400 to 1000 ft since discovery. to the \\'aters of the lIes field in that the The development of the Weber formation Morrison water contains sulphate and the of Pennsylvanian age in 1945-1946 has Dakota and Sundance \\'aters are sulphate· made this one of the outstanding oil fields free. Representative analyses of these in the state, if not in the Rocky Mountain waters are given in Table 3. area. Because of the former'lack of deep drilling water analyses from this field have TABLE 3-Reprcsclilalive A llalyscs of IV alers of M o.frat Dome TABLE s-Allalyscs of Waters of Rangely Field Dakota ~1orrison Sundance Frontier Dakota ~1orrison Weber Na ...... 447 3,570 1,074 0 76 6 Ca ...... 1\a.... 5.428 Mg. 0 30 0 873 3,069 37,725 SO •...... 0 560 0 Ca.... 71 8 18 3,509 Mg.... 38 o tr CI. .. 109 5,000 272 568 CO,. 26 0 0 SCk 1,339 279 984 973 CI.. .. 6,400 800 2,092 HCO, .. 945 535 2.400 65,000 CO,... 0 T.S. 1,047 9,486 2.532 tr o o HCO,.. 2,100 610 6 pH. 8.2 7 3 3,350 5 5 Source. Tank Bailer Stock tank 0 2,260 7,810 108,053 4,360-4,395 JI'r. ••• 1 '4,3 9 7.35 Depth ... 3.865 4,504 Source. Bailer Well· Casing DST head head Depth. 3,208-3,396 3,130 3,020-3,1206,510-6.533 Powder Wash This is another field of Wasatch (lower been rather sketchy m the past and the Eocene) oil production with lenticular few analyses available are rather tentative 268 WATERS OF PRODUCING FIELDS IN THE ROCKY MOUNTAIN REGION in correlation. Horizons which may produce to some extent in all the waters, They are water are the Frontier, Dakota, Morrison, erratic in concentration, and to some extent Shinarump and Weber; of these, the in composition, due principally to the Dakota and the Weber waters have been lenticularity of the sands. definitely identified. The Weber water is Soft, alkaline water is the rule in the unusual in that it is the only producing oil Dakota sandstone. Concentrations range field water in the Rocky Mountain region from about 700 to 3000 ppm total solids that can be called a brine, resembling in with an average of less than 1$00 ppm. this respect Mid-Continent and Cali Sulphate usually is absent, or present in fornia oil-field waters. Analyses of four of small quantities only. The Dakota waters these waters are given in Table $, the for the most part exhibit circulating ground Frontier and Morrison waters being water characteristics with little evidence of tentative. stagnancy, An interesting feature of the Dakota waters is the extraordinarily high Wilson Creek alkalinities in a few areas; the South

This is one of the newer and more McCallum carbon dioxide gas field is an Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 important Colorado fields with oil pro example. Comparable to this water is the duction from the Morrison and Sundance Pictured Cliffs sandstone water of the formations of Jurassic age. It is usual, Bondad area, which has a bicarbohate con where both the Morrison and Sundance tent of 9000 to 10,000 ppm, contain oil, to find the Sundance the larger Morrison waters, on the other hand, and more prolific producer; but at Wilson vary from soft, alkaline types to saline Creek, the Morrison exceeds the Sundance. waters containing appreciable hardness. The only waters so far encountered in pro In general, they are more concentrated than duction problems are those of the oil Dakota waters and indicate more stagnant producing zones and there is such a dif conditions of accumulation. They vary in ference in the two waters that definite concentration from about 3000 to 1$,000 correlation has never been difficult. Repre ppm total solids, and usually contain sentative analyses of the two waters are appreciable amounts of sulphate. as follows: Some Sundance waters have character istics similar to Morrison waters, and others Morrison Sundance show characteristics of Dakota waters. Sulphate has been found to be absent in Na .... . 1,416 5,245 most of the Sundance waters and the Ca ...... 26 374 Mg ...... o 79 alkaline and lower-concentrated waters are SO •...... 161 1,044 Cl...... 1,805 8,060 soft. The saline waters of higher concen CO, ...... tr o HCO, ...... 525 195 tration contain appreciable hardness, there T.S ...... 3,666 14,898 pH .... . 6.8 by resembling Morrison waters. Despite Source . . Stock tank Depth. 6,256-6,263 broad, general similarities in the three waters, there are sufficient points of dis tinction to identify them. General Summary

Certain generalities can be observed in OIL-FIELD WATERS OF MONTANA Colorado waters by taking into consider ation both productive and unproductive The oil-field waters of Montana were areas. covered rather thoroughly by the author The Wasatch waters, as pointed out in 1942, and there have been few important above, are saline despite the fluviatile additions since that time. Thus, this dis origin of the beds, and hardness is present cussion of the waters from the more im- JAMES G. CRAWFORD portan t fields of the state has been con pian, Devonian and Ordovician waters den sed from the author's previous paper. * from deep tests drilled in 1947 are on file but have not been released.) Border-Red Coulee Nose The oil and gas sands in the Border-Red TABLE 7-Typical Analyses of Waters of Coulee field are lenticular, complex sands Bowdoin Dome in the lower part of the Kootenai formation. Colorado shale It is postulated that the oil was generated Eagle (Vir. (Quadrant) in the underlying Ellis formation and mi ge11e) (Mar. (Bow. grated to the Kootenai under the influence tin) doin) ------1----- of Ellis water. It will be noted that the Na ...... 553 2,676 3,840 269 Ellis and Kootenai waters are substantially Ca ...... 57 54 89 544 Mg ...... tr 39 54 177 indistinguishable, which tends to confirm SO •...... 0 '42 47 2,180 Cl...... 844 4,000 6,053 200 tne above postulation; further, the Koote RCO, ...... 190 400 255 145 T.S ...... 1,547 7,108 10,208 3,441 nai waters in this field carry hydrogen pR ...... sulphide and in no other field in the state Source ... Siphon Bailer Bailer Plunge inlet Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 Depth ...... 690-780 285 3,175-3,180 has hydrogen sulphide been found in waters of Kootenai or younger. With the exception of these two waters there are Cat Creek Anticline easily distinguishable differences between Prior to 1945 the principal oil-producing all waters in the field, as is shown by the zone was the First Cat Creek sand, a 40 to typical analyses in Table 6. 60 ft sandstone near the base of the Colo rado shale. The Kootenai formation con TABLE 6-Typical Analyses of Waters of tains two sands, the Second and Third Cat Border-Red Coulee Field Creek sands of which the Second Cat Eagle Colorado Kootenai Creek produced a minor amount of oil. (Vir- (Black- (Cosmos- EIlis ge11e) leaf) Vanalta) The Third sand yielded large quantities of --- water under artesian head with a few show· Na ..... 219 6,203 1,285 1,577 ings of oil and gas. Recently oil has been Ca ...... 93 39 90 24 Mg ..... 69 43 52 13 found in the Brindley sandstone of the SO•..... 546 188 0 66 CI...... 10 8,800 619 755 Morrison(?) formation and the Schrock RCO, ... 500 1,415 2,880 2,940 Fifer sandstone of the Ellis formation. T.S ..... 1,183 15,969 3,46 2 3,881 pR ..... All sands yield water. Even on the crests Source . . B1eed- Bailer Lead line Bailer er of the domes the First Cat Creek sand Depth ... 85-II5 I .91 0-2 ,050 2.475-2,512 2,713-2,716 yields water with the oil, and there are very few wells that are entirely free of Bowdoin Dome water. All the Cat Creek waters are under Gas production at Bowdoin is from three artesian head and the water is compara sandy zones in the Colorado shale. The tively fresh, indicating active ground water highest (Martin zone) was the original circulation. The Brindley and Ellis waters source of the gas but produces none now; indicate more stagnant conditions. the second (Bowdoin zone) is the important Typical analyses of Cat Creek waters gas-producing horizon; the lower (Phillips are given in Table 8. zone) is a minor producer of gas. There are no particular water problems in the field, Cedar Creek Anticline typical analyses of the waters so far en This, the only producing district in countered in the dome being as given in eastern Montana, is an asymmetric fold Table 7. (Definitely correlated Mississip- with local highs over 100 miles long, ex * See references at the end of the paper. tending into the southwest corner of North 270 WATERS OF PRODUCING FIELDS IN THE ROCKY MOUNTAIN REGION

Dakota. Gas production is from sands of Bank field. The principal oil-producing the Montana Group, the Judith River zone is the Cut Bank sand, the basal mem sand being the important producer and the ber of the Kootenai formation. Two other Eagle sand a minor producer. Water is no sands, the Upper and Lower Sunburst, lie

TABLE 8-Typical Analyses of Cat Creek Field

Kootenai Colorado. Morrison, First Cat Creek Brindley Ellis Second Cat Creek Third Cat Creek

Na .... 591 564 354 1,191 1,101 Ca...... 0 0 0 17 12 Mg ...... 0 0 0 4 0 SO, ...... 0 39 289 1.309 598 Cl...... 400 57 35 46 2 827 CO, ...... 0 0 0 0 42 HCO, ...... 880 1.350 SIS 775 715 T.S ...... 1.394 1.324 930 3.364 2.932 pH ...... Source ...... Flow tank Lead line Lead line Swab

Depth ... . 1.158-1.177 1.515-1.530 1.690-1.704 1.460- 1.475 Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021

TABLE 9-Typical Analyses of Waters of Cut Bank District

Montana Group Kootenai 1-----,------1 Colorado. 1-----.------;----- Blackleaf Madison Two Upper Lower Medicine Virgelle Sunburst Sunburst Cut Bank

Na ...... 1.073 386 5.706 4.197 3.427 2.835 1.074 Ca ...... 52 0 126 59 68 35 0 Mg ...... 55 0 35 tr 38 tr 0 SO, ...... 1.852 265 0 95 32 28 131 Cl...... 133 '4 8.572 5.867 3.738 1.566 557 HCO, ...... 700 665 950 1,100 3.020 4.900 1.725 T.S ...... 3.509 992 14.906 10.759 8.788 6.874 2.610 pH ...... Source ...... Bailer Bailer Bailer Bailer Bailer Bailer Bailer Depth ...... 224-280 140 2.848-2.860 3.081-3.120 3.150 serious problem at Cedar Creek, none of the above the Cut Bank sand; gas, oil and wells producing more than a few barrels a water have been encountered in these day, and there is much less water in the sands, but commercial production has been southern part of the anticline than in the negligible to date. There are no serious central and northern parts. The water is water problems in the field; many wells comparatively concentrated, as would be drill to the Upper Sunburst sand before any expected in a gas-producing horizon and a water is encountered, and some do not find typical analysis of the Judith River water water until the Cut Bank sand is pene is as follows: trated. In other parts of the field water

Na ...... 4.546 may be encountered in the Montana Group c" ...... II9 Mg ...... 36 sands or in the Blackleaf sandy member of SO, .... . o the Colorado shale. Typical analyses of all Cl...... 7.176 HCO, .. . 260 these waters are shown in Table 9. T.S ...... 12,005 pH ...... Source . . Separator Depth ...... 826-880 Kevin-Sunburst Dome

Cut Bank District Oil production is principally from the re The most prolific field in Montana from worked top of the Madison limestone in this an oil production standpoint is the Cut field and gas production with a little oil is JAMES G. CRAWFORD found in the Sunburst sand of the Kootenai in those areas producing gas from a Mon formation. Waters that may be encoun tana Group sand. tered in drilling and production problems Colorado waters are moderately concen come from the Colorado shale, the gas-pro trated to concentrated saline waters with ducing Sunburst sand, the Ellis formation sulphate either absent or present in small (Ellis-Madison contact) and the Madison quantities only. The Kootenai waters often limestone. Even though the Colorado and resemble Colorado waters in concentration Sunburst waters have a marked resem but are usually more alkaline. Ellis waters blance to each other, the various waters are often resemble the lower-concentrated rather easily identified and correlation is Kootenai waters in chemical character-. not difficult. Representative analyses are istics but contain appreciable quantities of given in Table 10. hydrogen sulphide. The Quadrant and Tensleep formations TABLE 10-Typical Analyses oj Waters oj of central and southern Montana are Kevin-Sunburst Dome notable water reservoirs yitllding artesian

Colo Koo flows of hot, secondary saline water. Their Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 rarlo, tenai, }..1adison Black- Sun Ellis chemical composition is similar to, and leaf burst identical with, waters from pre-Triassic formations of Wyoming. :l\:a .. . 5,635 4/>70 1,370 1.173 Ca. 87 66 30 200 The waters of the Madison limestone Mg .. lIS 60 62 168 contain primary characteristics in the SO" ... 72 44 76 tr Cl. ... 8.476 5.980 775 1,771 Sweetgrass Arch fields. Secondary alkalin HC03 ... ·· 1,120 2,550 2,610 1,515 T.S ... '4,936 12.074 3,596 4,057 ity shows up in the Kevin-Sunburst and pl! ...... Source. Bailer Bailer Bailer Pondera waters. In the southern part of Depth .... 6 1,245 1,508-1,520 4. 75 Montana, Madison waters carry secondary salinity. General Summary The oil-field waters of Montana, as a OIL- FIELD WATERS OF WYOMING whole, are more concentrated than equiv The oil-field waters of Wyoming have alent formation water in Colorado and been surveyed and discussed rather thor less concentrated than the same in \Vyom oughly and a number of excellent papers ing. The average concentration of the have been published on the subject. There waters associated with oil is about 4000 are several reasons for the large number of ppm, with concentrations of 10,000 to analyses of Wyoming waters extant as 15,000 ppm in the gas areas. A noteworthy against the much smaller number from all feature of many formation waters in this other states in the Rocky Mountain region state is the excess magnesium over calcium combined. First, and most important, the even in waters containing less than 200 operating companies have been water ppm total alkaline earths. This excess is conscious and have been in the habit of particularly striking in the dolomitized taking water samples as a source of Madison limestone of the Pondera field, engineering and geological information. the ratio of magnesium to calcium being Too, the natural grouping of the oil and from 4 to 6 (on the basis of parts per gas fields into basins has resulted in regional million). correlations that has increased the value of Montana Group waters are dilute to water analyses. Again, as the early publi moderately dilute solutions of sodium cations on water analyses in the Rocky salts, the sulphate usually predominating. Mountain area dealt with specific Wyom A rather concentrated, saline water occurs ing oil fields, it is probable that interest 272 WATERS OF PRODUCING FIELDS IN THE ROCKY MOUNTAIN REGION was thus centered on Wyoming oil-field field and the first samples were not obtained waters. until 1942. Tentative correlations of the The main structural basins in Wyoming few samples obtained are as follows: are the Big Horn Basin, Wind River Basin, Powder River Basin, Shirley Basin, Hanna Lance Frontier Basin, Laramie Basin and Sweetwater Na ...... 1.789 4.432 Basin (Great Divide Basin). The important Ca ...... o 62 oil and gas producing fields are found in the o o ~& ...... :::::::::::::: 48 44 Big Horn, Wind River, Powder River and Cl...... 2.336 6.384 HCO, ...... 665 910 Sweetwater basins. T.S ...... 4.500 1l.369 pH ...... It lias been noted that waters from a Source ...... Flow tank Gun barrel particular stratum, although variable in Depth ...... 4.303-4.313 8.791 concentration, apparently have definite chemical characteristics in a particular Bailey Dome basin, lending themselves to probable One of the more recent oil fields in the

identification in untested str~ctures in the state is Bailey dome, Carbon County, oil Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 basin. Further, correlations throughout the production being found in the Sundance state, regardless of basin, have shown formation. It is interesting to note that of broad, general characteristics useful for the waters correlated with definite strata identification. This does not mean that the in the field, the Cloverly and Sundance Dakota water at Lance Creek, for example, waters are typical Cretaceous and Jurassic will correlate with equivalent water at Elk waters with high alkalinity; the Tensleep Basin but it does mean that a Cretaceous water is characteristic of the usual Tensleep water in one section of the state will re water in the state, secondary salinity being semble, as regards chemical character present and alkalinity being low. Analyses istics, a Cretaceous water in another of these waters are given in Table II. section of the state. Thus, tentative corre TABLE II-Water Analyses of Bailey Dome lations by age are possible wherever en countered in the state. This is particularly Cloverly striking in the two great age divisions of Sun the strata in the state pre-and post Dakota Lakota dance Tensleep Triassic. The rule, with some exceptions of ----1------Na ...... 2.700 1.437 1.332 572 course, is: primary characteristics in Ca ...... 0 44 20 303 Mg ...... 0 12 tr 56 waters of post-Triassic strata and second SO •...... 125 119 tr 1.656 ary characteristics in waters of pre-Triassic CI...... 1,902 1.060 2,270 240 HCO, ..... 3.735 2.035 2270 240 formations. T.S ...... 6.564 3.673 3.240 2.924 pH ...... The following discussion of the more im Source ... . DST DST DST Swab Depth ..... portant fields of the state will emphasize 4.505 4.652 5.085 6.961-7.320 the new information on oil-field waters obtained by deeper drilling. Baxter Basin (North, Middle, South) The Baxter Basin fields, Sweetwater Badger Basin County, are domes along the axis of the One of the older, deep oil-producing Rock Springs anticline, North Baxter fields in the Rocky Mountain area is that being about 1200 ft lower structurally than of Badger Basin, a dome in Park County. South Baxter. These fields are important Oil production is from sands of the Frontier gas producers, the Dakota and Sundance formation at average depths of 8500 ft. formations yielding gas at North Baxter There has been little water trouble in this and the Frontier and Dakota formations JAMES G. CRAWFORD 273 at Middle and South Baxter. The water In 1946, three wells were completed in the analyses from the Cretaceous sands of Lakota sand for gas production. The these fields show many 'rregularities, following analyses are tentative, positive probably due to the wedge nature of the correlation being possible only with further sandstones, and the Sundance waters vary development: to some extent over the structures and par ticularly with depth. The Tensleep water, Muddy Lakota Table 12, is a tentative correlation only and known Tensleep analyses will have to l\a .. r,228 4,224 Ca. 27 IO await further testing of the sand. Mg .. 13 tr SO .. 501 174 Cr. .. 645 5,247 TABLE 12-Water A nalyses of Baxter Basin CO, ... 96 79 HCO,. I,465 I,830 Field T.S .. 3.230 IO,634 pH ..... 7·75 7.95 ;\ orth Source ... . Depth .. 9,I08 Frontier Dakota I Sundance Tensleep ------

--- Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 Big Hollow, Na ..... IO,879 6,535 5,288 Io,606 Ca ... .. 222 60 23 I.245 Mg .. 125 57 tr 209 This field is a dome in the Laramie Basin, SO •. 0 IOI 151 I,915 Albany County, which has produced oil CI ...... 16,667 ro,ooo 3,900 15,694 HCO, .. 1,490 475 7.200 3.550 from the Muddy sandstone of the Thermo T.S .... 28.626 16,986 12.902 3 ,4'5 pH ... ' polis shale at the relatively shallow depths Source .. DST DST Depth .. I,724 4, I 20--4.290 3,828-3,844 6,339 of 900 ft. Deeper drilling encountered water in the Cloverly formation and Ten Middle sleep sandstone, the Cloverly water being Frontier Dakota dilute and the Tensleep water correlating favorably with equivalent waters through Na. 21,114 6,455 Ca. '70 o out the state, Typical analyses are given in Mg. 93 o Table 13. SO ... . 37 23 Cr. .. . 30,350 5,928 HCO,. 4,750 6,900 TABLE 13-Water Analyses of Big Hollow T.S .. . 54,IOO 15.799 pH .... . 8. I Dome Source .... . DST DST Depth .. . 2,OI2-2,030 2,359-2,367 I Ther- Upper mopolis Cloverly Tensleep South (Muddy)

Frontier Dakota Sundance l\a. I,382 378 785 Ca. 0 0 205 Mg ...... 0 0 II Na ...... 8.790 4,093 3.162 SO •... , ...... 15 184 I.881 Ca ...... o 56 12 Cr...... I,397 171 135 Mg .... , .... . o 33 tr CO, ...... 180 0 0 SO •...... o o 153 HCO,. 880 475 135 Cr...... 8.150 4.032 3.250 T.S ...... 3.40 7 9 6 7 3,083 CO, ...... 1.047 o 64 pH ...... HCO, ... . 7.175 4.260 2,510 Source . . , ..... Lead line DST T,S .. .. 2I.515 IO.309 7,876 Depth ...... 880-925 1,400-1.500 pH ... . Source .. . Bailer Depth ...... 3.685 Big Medicine Bow Medicine Bow, now known as Big Medi Beaver Creek cine Bow, Carbon County, is an asymmetri The Beaver Creek dome, Fremont cal anticline producing oil and gas from the County, is the south dome of the Beaver Sundance formation, Before the discovery Creek anticline and produces distillate and of Sundance production one well flowed a gas from a sand in the Morrison formation. small quantity of oil from the Frontier 274 WATERS OF PRODUCING FIELDS IN THE ROCKY MOUNTAIN REGION formation. There are apparently two Big Sand Draw Sundance sandstones present in the field, A sharply folded, asymmetrical anticline the first, which some include in the Morri in Fremont County, Big Sand Draw, was son formation, being about 50 ft thick and discovered in 1918. It was proved for gas the second about 100 ft thick; a so-ft production from the Frontier and Cloverly shale and limestone unit separates them. formations and was operated as a producing Both sands contain oil, gas and water. gas field until comparatively recently. Representative analyses of waters in this Deeper drilling in 1942 uncovered a large field are given in Table 14. reservoir of oil in the Tcnsleep formation and this sand is now in the process of TABLE 14-Analyses of Waters zn Big development. There have been no water Medicine Bow Field problems to date in the field, most of the

First Second Tensleep samples so far obtained coming from the Sundance Sundance flanks of the structure. A typical analysis of the Frontier water is as follows: Na ...... 752 664 605 Ca ...... 0 0 475 Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 0 0 63 ~a. 2,252 ~cf.'.'.'.:: : 264 422 2,024 Ca .. ,6 Cl...... 41 167 385 Mg .. tr CO, ..... 59 54 0 SO •.. 26 HeO, .... 1.470 825 135 Cl. .. 2,600 T.S ..... 1.839 1.713 3.618 C03 ..... Ir pH ...... HCO,. 1.518 Source ... Flow tank Flow line DST T.S ...... 5.640 Depth ... 5.538-5.596 5.606'-5.69 8 7.003-7.037 pl! .... . Source . . Bailer Depth. 3.625-3.720 Big Muddy Black Mountain This is one of the older fields in the state Black Mountain, Hot Springs County, is and is a slightly faulted dome lying in a long, narrow, basin ward anticline with oil Converse County. Oil production is from production from the Embar, Tensleep and the Shannon sandstone of the Steele shale Madison formations. Water problems are the Wall Creek sands of the Frontie; serious in this field. Only two wells out of formation, and the Dakota and Lakota eight produced oil from the Embar though sands of the Cloverly formation. Serious all wells were located favorably on the water conditions are present in all sands structure; lenticular zones of variable and there are very few, if any, wells that permeability permits the interfingering of produce oil free from water. Typical water, causing wells higher structurally to analyses of the various formation waters produce water while lower wells produce are shown in Table IS. clean, or almost clean, oil. Dilute, artesian water is produced with the oil from the TABLE Is-Water Analyses of Big Muddy Field Tensleep formation. One well produces from the Madison formation and the water Shan- non Frontier Lakota Sundance associated with the oil is dilute and similar ------to the artesian Tensleep water. Typical Na .... 4.989 2.976 1.318 1,492 analyses are given in Table 16. Ca ..... 77 0 0 0 Mg .... 49 0 0 0 SO •.... 0 0 485 1.330 Cl. .... 7.714 1.976 616 686 Byron CO, ... 0 tr 67 37 HCO,.. 450 4.505 1.675 1.015 T.S .... 13.050 7.167 3.310 4.044 The Byron structure is a faulted anticline pH .... in Big Horn County, about two miles north Source. Lead Lead line Sump line east of the Garland field. Gas production Depth. 9 12-944 3.070-3.080 4.353-4.364 4.240-4.260 comes from the Frontier formation and oil JAMES G. eRA WFORD 275

TABLE 16-Typical Water Analyses of TABLE 18-Typical Water Analyses of Cole Black Mountain Field Creek Dome

Embar Tensleep Madison Lance Shannon Lakota

Ka ..... 428 70 5 Ka ...... 345 6.729 1,695 Ca ...... 673 78 75 Ca ...... 57 63 52 Mg ..... 99 20 37 Mg ...... 28 24 tr SO •..... 1,935 92 IS SO •...... 493 0 863 Cr...... 35 12 22 Cr...... 25 9,900 1,671 CO, ...... 34 0 0 HCO, ...... 560 1,135 685 HCO, ...... 1,097 385 370 T.S ...... 1,223 17,274 4,618 T.S ...... 3,743 4 61 336 pH ...... pH ...... 8.0 Source ..... Well head Separator Swab Source .... Bleeder Treater Depth ..... 4,645-4,679 8,002-8,027 Depth ...... 3,176 3,965-3,973

tion is from the Cloverly formation and production from the Embar and Tensleep water analyses to date are too few to make formation; one well found some oil in the definite correlations, However, the analysis Sundance. These formations are similar to below is believed to be Cloverly water: equivalent strata at Garland but lie about Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 2000 ft deeper at Byron. There are no Na ...... 2,864 Ca .. . o water. problems in the field, typical analyses Mg .. o SO •.. 106 of those analyzed is shown in Table 17. CI ...... 3,6I9 HCO, .. . 1,240 T.S ... . 7,199 TABLE 17-Typical Water Analyses of pH .... . Source Byron Field Depth ......

Frontier Embar Tensleep Dallas Dome i'a .... 1,132 3,470 5 I Dallas, Fremont County, is the oldest Ca ..... 0 374 593 oil field in the state, having been discovered Mg ...... 0 94 I54 SO •..... 9 6,807 I,376 in 1884 wr.en oil was located at a depth of Cr...... I29 794 30 CO, .... 145 0 0 300 ft. The field, together with Lander and HCO, ..... 2,475 8I5 975 T.S ...... 2,632 II,940 2,683 Derby fields, is a local dome on the long pH ...... 8·45 6 7 Source .... Lead line Lander anticline and produces oil from the Depth ... 2,000 5,250-5,322 Embar and Tensleep formations. All wells in the field produce water estimated at Cole Creek about 4 bbl of water for each barrel of oil Cole Creek, Katrona and Converse coun produced. The base of the Tensleep forma ties, is a large symmetrical dome with tion contains dilute water under artesian about 500 ft of closure producing oil from head and the similarity between this water the Shannon sandstone of the Steele shale, and some of the Embar waters encountered Oil saturation has been found in the Dakota suggests that artesian Tensleep water has and Lakota sands, of which the Lakota has entered the Embar formation. Typical become a minor producer. Water is pro analyses of these waters are as follows: duced with the oil from edge wells of the Shannon sand and a little water is produced Embar Tensleep by crest wells. Typical analyses of forma ?\a .. 276 4' tion waters are given in Table 18. Ca .. 139 48 Mg. 48 20 SO •. 648 67 Crooks Gap Cr. ... 55 29 HCO, ..... 480 220 Although tested as early as 1925, Crooks T.S .... 1.402 3I4 pH ..... Gap, Fremont County, did not become a Source ..... Flow line Casing head Depth .... 655-698 commercial oil field until 1945, Oil produc- 276 WATERS OF PRODUCING FIELDS IN THE ROCKY MOUNTAIN REGION

Derby Dome cia ted with oil is about 10,000 ppm. Derby Dome, Fremont County, is on the Typical analyses are given in Table 19. same line of folding as Dallas but about Frannie 4H miles southeast. Oil production is from the Embar and Tensleep formations and, The Frannie field, Park County, is an like Dallas, considerable water is produced asymmetrical, elongated dome transversely with the oil. Estimates of 4 bbl of water per cut by two faults. Oil production is from barrel of oil produced have been made and the Tensleep and Madison formations, the it is noted that artesian water occurs in the major production coming from the Tensleep base of the Tensleep formation. Typical sandstone. Typical water analyses from water analyses are: Frannie are shown in Table 20.

TABLE 20-Typical Water Analyses of Embar Tensleep Frannie Field

Na .... 373 4 Greybull Tensleep Madison Ca ... 220 35 Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 Mg ..... 43 22 22 SO •..... 1,178 ~a ...... 4 9 206 II Cl...... 12 3 Ca ...... 'tr 639 207 HCO, ... 355 195 Mg ...... 0 128 69 2,001 182 T.S ...... SO ...... 329 2,230 483 pH ..... Cl...... 28 tr Casing head 43 Source .. . Casing head CO, ...... 59 0 0 Depth ... 1,942-2,055 HCO, ...... 533 255 390 T.S ...... 1,114 3,356 95 1 pH ...... Source ..... Elk Basin Depth ...... 2,650 3,169-3,343 Elk Basin, Park County, is an extremely faulted basin ward dome with several Garland thousand feet of closure. Discovered in The Garland structure, Big Horn County, 191$, oil production was from the Frontier is an extremely faulted basin ward dome sands with some gas production from the producing oil and gas from the Frontier, Cloverly sands. The field came into promi Tensleep and Madison formations, and gas nence in late 1942 with the discovery of oil from the Cloverly Group sandstones. It is in the Tensleep sandstone and has become interesting to note that the water analyses one of the most prolific producers of oil from this field are characteristic and typical from the Pennsylvanian stratum in Wyo of the strata from which sampled. The soft ming. The analyses of Tensleep waters from alkaline Frontier water is typical of the this field are erratic and inconsistent, the usual Frontier water in the state; the sec concentration varying from a minimum of ondary saline Embar and Tensleep waters, about $000 to as high as 20,000 ppm. The with the higher concentration of the Embar average concentration of the waters asso- and the lower chloride of the Tensleep, are

TABLE 19-Typical Water Analyses of Elk Basin Field Eagle Frontier Dakota Embar I Tensleep Madison Na ...... I,303 3,86 7 2,940 2,I26 3,940 I,65 2 Ca ...... 40 24 50 570 222 383 Mg ...... 20 tr tr 86 55 I05 SO ...... ' ... I,963 0 3,560 5,010 6,590 2,855 Cl ...... 80 5,275 I,548 140 992 1,000 HeO •...... 1,049 L257 770 1,205 I,330 730 T.S ...... 3,922 9,784 8,477 8,525 I2,453 6,354 pH ...... 7·35 Source ...... Lead line DST Flow line DST Depth ...... 250 I,845-I,865 4,045-4,075 5,259-5,282 6,099-6,269 6,6I6-6,649 JAMES G. CRAWFORD 277 representative of the average all over the Embar Tensleep state. The Madison waters from Garland, though, are erratic in composition and con Na .. I, I 72 556 Ca. 386 centration, varying from IOOO to 4000 ppm 543 Mg. 197 ISS total solids. Water analyses are given in SO •. 2.58 4 1.880 Cl...... 715 343 Table 2I. HCO, .. 1.240 450 T.S .... . 5.821 3.541 pH .... . Source .. Flow tank Flow tank TABLE 2 I-Water Analyses of Garland Field Depth. 3,919-3.993 4.397-4,5 I 2

Fron- tier Embar Tensleep Madison ----- Hamilton Dome Na ..... 4,575 1,423 232 48 This field is a highly faulted anticline in Ca .. 0 456 549 352 Mg. 0 81 143 70 Hot Springs County producing oil from the SO ... :: : 0 4,084 1,680 971 Cl...... 2,305 44 157 27 Chugwater, Embar and Tensleep forma HCO, ... 8.180 305 525 270 T.S .... 10.901 6,238 3.057 1.601 tions. Typical water analyses are given in pH .. 7·0 8.3 7 65 22. Source: : Flow DST Lead line DST Table Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 tank Depth ... 3,223 3,275-3,356 4,462-4,535 4,779-4,825 TABLE 22-Typical A nalyses of Waters of I!amilton Dome Gebo Chugwater Embar Tensleep Gebo dome, Hot Springs County, is one of the more recent oil fields of the state, Na 15.349 3,913 946 Ca...... 696 II4 444 having been discovered the latter part of Mg,. 81 156 110 I943. Oil production is from the Embar SO •. 12.413 5.420 1.489 Cl. .. 15.810 1.930 SIS limestone, There are at this writing insuf CO, ... 0 0 0 HCO, .. ... 285 1,310 1.035 ficient water analyses to make definite T,S .... 44.48 9 12, I 78 4,309 pH ..... 79 7.3 correlations but tentative analyses of the Source. Well head Well head Sundance and Embar waters are given Depth ...... 2.410-2.680 below: Herrick Dome Sundance Embar Herrick dome, Albany County, is a 1947 discovery. Production was found in the Na ..... , .... . 903 4,261 Tensleep sandstone and the only water Ca, ...... " ... . 59 357 Mg ...... , .. 24 80 analyses available are from the producing SO •. , ...... 1,348 6,518 Cl...... 100 1,778 formation. A typical Tensleep analysis is as HCO, ...... 815 1,460 T,S ...... 2.835 13.712 follows: pH ...... , Source .... . Lead line Depth .. . 3.380 Na .. 2.027 Ca .. 400 Mg, ...... 214 SO •...... 5.27 1 Cl...... 410 Grass Creek HCO, .. , ...... , .. 270 T,S ...... 80455 Grass Creek, Hot Springs County, is an pH ...... 7·85 Source .. . DST elongated basin ward dome with oil produc Depth" . 3.657-3.701 tion from the Frontier, Embar, and Ten sleep formations and some gas from the Hidden Dome Muddy and Greybull sands of the Dakota The oil discovery in Hidden dome, Wa Group. The only water analyses available shakie County, was made in 1932, although from this field are from the Embar and gas had been produced from the field since Tensleep formations, as follows: I9I7. Production was from the upper 278 WATERS OF PRODUCING FIELDS IN THE ROCKY MOUNTAIN REGION

Frontier sandstone. In 1947 oil was found was the first field in the Rocky Mountain in the Tensleep sandstone and the field region to produce oil commercially from the now is in the process of development. The Tertiary. There are at least two, possibly only water analyses from this field available three, distinct divisions of the main pro to the author are from the Tensleep, ducing zone, all containing oil, gas and tabulated below. The dilute nature of the water. Typical water analyses from these water is due to meteoric feed where the fields are given in Table 24. sandstone crops out a few miles from the field: TABLE 24-Typical Water Analyses of the Na ...... 29 La Barge Fields Ca ...... 59 Mg ...... 52 SO •...... 8 La Barge Cl...... 27 North HCO, .... . 460 La Barge T.S ...... 401 Upper Sand Lower Sand pH .... . 8·4 Source ...... DST --- Depth .... . Na. 1.245 3.458 4.504 Ca...... 0 60 33 Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 Mg. ... 20 0 17 Kirby Creek SO •. .. 65 0 29 Cl. 850 3.800 6.413 Kirby Creek, Hot Springs County, is a CO, ... 0 0 120 HCO, .... 1.960 2.640 905 narrow asymmetrical anticline along the T.S ..... 3.177 8.558 II.588 pH axis of the Zimmerman Butte anticline. Source. Tubing head Tubing head Production was originally from the Fron Depth ... 600+ 900+ 2,005-2,030 tier sand, there being by 1938 four small pumping wells with a total daily production Lance Creek of about 7 bbl of oil and 35 bbl of .water. In 1944 oil production was found in the The Lance Creek oil field, Niobrara Embar formation. Pre-Triassic waters have County, is the state's largest oil field from not been definitely correlated as yet, thus standpoint of daily production, having the Embar and Tensleep analyses in Table achieved that honor in 1940. It is a broad 23 are tentative: dome with about 650 ft of closure on the elongated, asymmetrical Lance Creek anti TABLE 23-Water Analyses of Kirby Creek cline. The principal oil-producing zone is

Frontier Embar Tensleep the Minnelusa formation with its four lenticular, intercommunicating Leo sand

Na ...... 477 1.437 195 stone bodies. Some production comes from Ca ...... 0 25 41 Mg ..... 0 tr IS the Sundance formation and oil has been SO •.... 0 2.434 388 Cl...... 9 75 23 found in, and produced from, the Wall CO, ..... 128 0 0 Creek, Newcastle and Fall River sands. HCO, ..... 990 670 185 T.S ..... 1.101 4.300 753 The Basal Sundance water from this field pH ...... Source ..... Lead line DST shows the characteristic chloride and con Depth .... 402-495 3.644-3.652 3.6 77-3.688 centration increase up structure, the waters associated with oil averaging about 10,000 La Barge ppm total solids and 3000 ppm chloride as The La Barge oil field, Lincoln and Sub against 6000 and 500, respectively, for lette counties, is on a long, narrow, asym those down structure. There are no appre metric anticline with two highs, one the ciable differences in chemical composition La Barge field and the other the North or concentration between the waters in the La Barge field. Oil production is from Leo sandstone zones of the Minnelusa formations of Tertiary age and La Barge formation, which indicates intercommuni- JAMES G. CRAWFORD 279

TABLE 25-Typical Water Analyses of Lance Creek Field

Minnelusa Basal Fall River Sundance Converse Leo Bell

Na ...... 834 3.445 1.669 632 765 Ca ...... 0 192 454 307 251 Mg ...... 0 35 53 59 60 SO •...... 0 3.663 3.873 1.322 1.929 CI...... 52 2.761 356 606 250 HCO, ...... 2,125 495 545 185 215 T.S ...... 1.931 10.339 6.673 3.017 3.361 pH Source ... . Flow tank Flow tank DST Depth. 3.405-3.433 4.295-4.345 4.530--4.568 5.512-5.542 5.482-5.517 cation of the zones. Typical water analyses Park County. Gas production comes from from this oil field are given in Table 25. sandstones in the Frontier formation and

oil production from the Embar and Ten Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 Lander (Hudson) sleep formations. Typical water analyses The Lander anticline, Fremont County, are shown in Table 26. is on the same major line of folding as that of Dallas and Derby domes. Oil production TABLE 26-Typical Water Analyses of is from the Embar limestone and Tensleep Little Buffalo Basin sandstone, and almost all the wells produce Fron Ten water with the oil. Typical water analyses tier Dakota Embar sleep are: Na ...... 3.062 2.174 777 710 Ca ..... 24 40 756 373 Embar Tensleep Mg ... tr 16 193 135 SO •.. 58 864 2.631 1.229 CI...... 3.576 2.095 270 343 Na .... . II7 HC03 .••••• 1.977 1,270 1.525 1.545 34 T.S ...... Ca .. .. 109 48 7.692 5.81 4 5.377 3.550 Mg...... 28 12 pH SO •.. 256 60 Source ...... Swab DST CI. ... 38 6 Depth ...... 3.020 5.068-5.078 HCO, ... . 390 190 T.S ...... 740 247 pH Source .... Lead line Lost Soldier Depth .. 1,150 2.148 The Lost Soldier field, also known as Little Lost Soldier, Sweetwater County, is Little Buffalo Basin a highly faulted, elliptical dome en echelon This field occupies two elliptical domes with the west end of the Wertz-Mahoney with a total closure of about 1600 ft in Ferris anticline. Oil production is from

TABLE 27-Typical Water Analyses from Lost Soldier Field

Frontier Muddy Dakota Lakota Sundance Tensleep

Na ...... 5.376 3.909 1.781 2,219 1.649 1.724 Ca ...... 36 0 0 32 IS 470 Mg .... tr 0 0 20 0 68 SO •.... 0 0 0 265 0 1.933 CI...... 5. 1 00 3.202 I.II9 1.300 996 1.954

HCO, .... '" 5.595 4.870 2.800 3.510 2,710 530 T.S ... 13.263 9.506 4.277 5.436 3.992 6.410 pH Source ...... Flow tank Lead line Lead line Flow tank Flow tank Flow tank Depth ...... 225-305 1.930--1.950 1.971-1.985 2.335-2.338 2.150--2.175 5.262-6.473 280 WATERS OF PRODUCING FIELDS IN THE ROCKY MOUNTAIN REGION the Frontier sandstones, Dakota sandstone, Maverick Springs Lakota sandstone, Morrison formation, Maverick Springs, Fremont County, is Sundance formation and Tensleep sand an elongated dome on the Maverick Springs stone. Most of the wells in the post-Triassic anticline producing oil from the Embar and formations produce varying amounts of Tensleep formations. As the wells begin in water but as yet little water is produced either Sundance or Chugwater beds, the from the Tensleep. Typical analyses are waters likely to be encountered are few. given in Table 27. Typical analyses are as follows:

Mahoney Embar Tensleep The Mahoney dome gas field, Carbon Na ...... 657 IS County, is a broad, oval anticline producing Ca ...... 624 224 Mg ...... 136 87 gas from the Dakota and Sundance sands SO •...... 2.599 469 Cl...... 284 36 HCO, ...... and oil from the Tensleep. Water has been 535 457 Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 T.S ...... 4.563 '.05 flooding the Dakota sand but the Sundance pH ...... ' Source ...... Flow tank and Tensleep formations have not been Depth .... . 1.344-1•63 2 troubled to any extent with water prob lems. Typical analyses of waters from this field are given in Table 28. Mule Creek (East and West) The Mule Creek oil field, Niobrara County, is a low, symmetrical dome with TABLE 28-Typical Analyses of Water from about 250 ft of closure. Oil production has Mahoney Field been from the Lakota sandstone with one Frontier Sundance Tensleep well producing a minor amount of oil from the Minnelusa formation. Edge water Na ...... 2.346 2.056 232 encroachment has been gradual in the field Ca ...... 0 0 540 Mg ...... 0 0 125 but most wells produce some water. The SO •...... 0 76 1.835 Cl...... 1.46 7 2.392 172 West Mule Creek oil field is an elongated CO, ..... 370 49 0 HCO, .... 2.950 1.145 260 asymmetrical dome about 3 miles north T.S ..... 5.634 5.136 3.032 pH ...... and west of the Mule Creek field. It has a Source . .. Casing head Lead line Lead line closure of about 600 ft and produces oil Depth ... 1.985-2.025 3.195-3.390 4. 293-4.505 from the Dakota Group sands with one

TABLE 29-Typical Water Analyses of Mule Creek Field

Mule Creek West Mule Creek

Fall River Lakota Fall River Sundance Minnelusa

Na ...... 304 4'3 338 1.397 714 Ca .. . 0 0 0 290 536 Mg .... . 0 0 0 ItO 178 SO •... 233 302 233 3.898 3.362 Cl...... 44 54 44 47 55 CO, .. 59 37 0 0 0 HCO, ... . 315 545 433 ItO 56 T.S ... . 795 1.074 795 5.796 4.873 pH .. . Source. Lead line Lead line Bailer Casing head Bailer Depth. 1.379-1.450 1.357-1.382 780-808 945-970 1.670 JAMES G. eRAWFORD 28I well producing a small amount from the surface or formation, in the area. A typical Minnelusa formation. Typical water analy analysis follows: ses from these two fields are shown in Na .... . 5.990 Ca .... . 33 Table 29. Mg .... . 48 SO •...... 21 CI...... 5.350 Mush Creek CO, ... . 495 HCO, .... . 6.000 T.S ...... 14.88 7 Mush Creek, Weston County, is one of pH ...... 7·75 Source .. . the newer light oil fields of the state, its Depth .. . 3.923-3.946 major development occurring in 1947. The area is a stratigraphic play, production Oregon Basin (North and South) depending on development of the New The Oregon Basin oil and gas field, Park castle sandstone toward the west. Pay is County, consists of two large adjoining erratic and nonpredictable; dry holes domes separated by a narrow saddle. Both often are drilled next to producing wells. domes are cut by two or more lines of The pay ranges in thickness from 8 to 20 faulting. The south dome has a closure of Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 it, 12ft being considered an average for the about 800 ft and the north dome about area. Water analysis from this area have 400 ft. Gas production comes from the been confined to the producing sand. The Frontier, Cloverly and Morrison forma Newcastle water varies in total solids from tions, and oil production from the Embar, 12,000 to 17,000 ppm and is marked by Tensleep and Madison formations. The comparatively high chloride and bicar Frontier waters from both the north and bonate content. It is distinguished easily south domes are dilute, soft and noncor by these features from all other waters, rosive. The Tensleep wells produced clean

TABLE 30-Typical Water Analyses of Oregon Basin Fields North

Frontier Dakota Morrison Embar Tensleep Madison

Na. 619 1.263 46 7 I.9Ir 1.453 406 Ca. 43 0 0 459 174 770 Mg ...... tr 0 0 165 144 208 SO ...... 10 26 0 3.929 3.1 I2 1.848 Cl ..... 130 993 430 490 500 196 CO, ..... 0 54 0 0 0 0 HCO, .. 1.530 1.500 500 1.465 660 1.780 T.S ... 1.564 3.074 1.143 7.674 5.707 4.303 pH .... Source .. . Lead line Flowline Bailer Lead line Dehydrator Bailer Depth ...... 1.375-1.464 2.036--3.801 3.565-3.628 3.801 4.365-4.374

South

Frontier Chugwater Embar Madison Flathead

Na ...... 701 14.280 1.665 273 985 Ca ...... 0 646 529 238 450 Mg...... 0 187 189 139 10 SO •...... 0 10.472 3.669 1.093 1.337 Cl ...... 488 15.850 769 196 1.333 HCO, ...... r,OIS 135 1,000 4 20 44 T.S ...... 1.688 4 1.501 7.313 2.145 4.137 pH ..... Source ...... Bailer Lead line Flow tank Lead Jine Depth ...... 3.840 3.718-3.736 4. 165-4.295 6.341-6.346 282 WATERS OF PRODUCING FIELDS IN THE ROCKY MOUNTAIN REGION

oil except on the edge of the field, thus of these stray sands are rather persistent these waters are not a problem. The Embar over an area and the analyses of these waters have been a problem, though, and waters have proved confusing in the corre most of the Embar wells in the field now lation of waters from this field. Typical are making some water. The average water analyses are given in Table 31. Embar water has a concentration of 7000 to 9000 ppm, but there are a number of Pilot Butte wells in the northern area of the south Pilot Butte, Fremont County, is an dome that yield Embar water with concen irregular, asymmetric faulted dome origi trations of 12,000 to 20,000 ppm. Typical nally producing oil from saturated zones of water analyses, including that of the Flat fractured sandy shale in the Steele shale. head sandstone of Middle Cambrian age, Deeper drilling yielded oil in the Tensleep are given in Table 30. formation but water accompanying the oil indicated that accumulation IS small. Osage Typical water analyses are presented in The Osage oil field, Weston County, is a Table 32. Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 gentle westward dipping monocline on the southwest flank of the Black Hills uplift. Poison Spider Oil accumulation is caused by lensing of Poison Spider, Natrona County, is a the Newcastle sandstone in structural small dome with about 175 ft of closure on terraces and oil production is from this the Pine Mountain-Oil Mountain fold. Oil sandstone and the overlying Belle Fourche production is from a lower Sundance sand shale. Stray water-bearing sands have been stone and considerable water is produced logged by several wells in this field. Some with the oil. Representative water analyses are given in Table 33. TABLE 31-Typical Water Analyses oj TABLE 33-Typical Water Analyses oj Osage Field Poison Spider Field Green- New- horn castle Lakota Minnelusa Dakota Sundance Tensleep ------

Na ...... 5,899 506 257 7 Na ... 349 780 4'9 Ca ..... 4S 0 0 78 Ca ...... 6 0 290 Mg ..... 21 0 0 23 Mg .... 0 0 75 SO •..... 64 65 355 43 SO ...... 325 80 1,237 Cl...... 8,785 340 8 5 Cl. .... IS 213 386 CO, ..... 0 251 0 0 CO, .... 72 I92 0 RCa, ... 700 165 215 307 HCO,. 360 1,208 135 T.S ..... 15.158 1.243 780 307 T.S .... 944 1,859 2,473 pH ...... pR. 7·5 Source. I Bailer Tap Well head Source. Bleeder Lead line Well head Depth. . 639-649 1,727 2.528-2,592 Depth ... 2,706

TABLE 32-Typical Water Analyses oj Pilot Butte Field

Steele Frontier Dakota Embar Tensleep

Na .... 5,894 1,698 2.586 3,462 434 Ca .... 26 24 137 363 306 Mg ... 46 57 28 76 80 SO •...... 0 0 4,2 14 7,437 1,414 Cl...... 7,154 1,395 559 525 220 RCO,...... 3,640 2,472 I,IIO 325 3IO T.S ..... 14,910 4,383 8,070 12.023 2,606 pH .... Source .. . Flow line Tubing Bleeder Treater Depth .. 735-769 3,779-3,791 6,024-6 ,289 6,204-6 ,349 JAMES G. CRAWFORD

Rock Creek Salt Creek The Rock Creek oil field, also known as The Salt Creek oil field, Natrona County, Rock River oil field, Carbon County, is an is an asymmetrical dome near the north asymmetric anticline on the east slope of end of the Salt Creek anticline. Closure is the Medicine Bow Mountain Range; the about 1600 ft and oil production has been structure has about 1600 ft of closure. Oil obtained from the Niobrara-Carlile shale, production is from the Muddy sandstone, three Wall Creek sands of the Frontier the Dakota and Lakota sandstones of the formation, the Muddy sandstones (locally Cloverly Group, and the Sundance forma called Lakota shale), the Lakota sandstone, tion. In this field all Dakota Group wells the Morrison formation, two benches of are bottomed in the basal Cloverly sand the Sundance formation, and the Tensleep and all exposed sands are protected by sandstone. The Salt Creek area has been liners perforated opposite the sands; thus a thoroughly water-surveyed, every well that wattr cannot be definitely correlated with has made, or makes, water having been a particular sand and these waters are sampled, often several times. The water called "Cloverly." Typical analyses of drive in the First Wall Creek sandstone has Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 "Cloverly" and Sundance waters are given been mapped periodically by the use of below: water analyses and abandonment of wells has been expedited by use of water analysis

"Cloverly" Sundance data. Swedenborg. and Ross, Herman Stabler, Claire and Coffin, and the author Na ...... 2,962 924 have published papers concerning the Ca ...... 0 0 Mg ...... 0 0 waters of this area, and without doubt more SO•...... 0 297 C!...... 3.240 245 is known of the characteristics of the CO, ...... 0 120 HCO, ...... 2,290 1,410 waters of this field than any other area in T.S ...... 7.328 2,279 pH ...... the Rocky Mountain region. Twelve typi Source . .... Flow line Flow line cal water analyses from the Salt Creek Depth .... 3.313-3.360 field are given in Table 34.

TABLE 34-Typiwl Water Analyses oj Salt Creek Field Niobrara- First Wall Second Wall Third Wall Lakota Shannon Carlile Creek Creek Creek Shale

Na ...... 407 2.893 1.582 5.456 6.506 3.232 Ca ...... 126 tr tr 8 0 10 301 0 0 0 0 0 ~cf.':::::::::::: . 1.527 937 tr 0 60 82 C!...... 26 2.667 550 5.988 8.500 3.250 CO, ...... 0 24 tr tr tr 4 HCO, ...... 990 1.850 3.250 4.200 2.650 2.920 T.S ...... 2.874 7.431 3.731 13.517 16.369 8.014 pH ...... Source ...... Bailer .Bleeder Flow tank Depth ...... 1,030-1,130 2.845-2.852

Second Third Dakota Lakota Morrison Sundance Sundance Tensleep

Na ...... 5.131 1.252 4.580 3.827 4.009 456 Ca ...... 38 28 36 24 334 378 6 tr 24 12 59 8. rcf.·.·.:::::: . 42 0 334 90 2.662 1.231 Cl...... 6.850 340 6.361 4.850 4.568 604 HCO, .... 1.915 2.700 1.049 1.220 710 170 T.S ...... 13.009 2.948 11.835 9.483 II.981 2.836 pH ...... Source ...... Bailer Bleeder Bailer Flow tank Well head Depth ...... 2,280-2,310 2.410-2.476 2.690 3.803 284 WATERS OF PRODUCING FIELDS IN THE ROCKY MOUNTAIN REGION

Steamboat Butte General Summary

This field was discovered in 1942 and The striking points about Wyoming oil consists of an elongated dome with about field waters is the almost clean-cut separa 250 to 300 ft of closure lying in Fremont tion by age into two distinct types of water, County. Oil production is from the Sun the Triassic beds acting as the dividing dance and Tensleep formations. The Dakota line. Post-Triassic formations most often sand has yielded some oil and the Embar contain waters in which primary charac limestone shows saturation in crest wells. teristics predominate; pre-Triassic forma The Frontier sandstones yield gas which is tions usually contain waters in which used in field operations. The Sundance secondary characteristics are dominant. water in this field shows evaporite charac This same division applies to the crude oils, teristics, ranging in concentration of total black, high-sulphur oils in pre-Triassic solids from 20,000 to 40,000 ppm. It bears a beds and green, low-sulphur oils in post definite resemblance to Triassic waters Triassic beds. Recent investigations by the elsewhere in the state. Typical analyses of author into the occurrences of natural formation waters found at Steamboat gases indicate that this same division Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 Butte are shown in Table 35. exists for the gases, pre-Triassic beds for

TABLE 3S-Typical Water Analyses of Steamboat Butte Field

Frontier Dakota Sundance Embar Tensleep Madison

Na ...... I.706 3.035 10,012 1.496 649 261 Ca ...... 0 0 486 424 340 369 Mg ...... 0 0 103 85 78 77 SO •...... 98 16 10.946 3.600 1,523 966 CI. .. 1,800 3.518 8.316 371 244 183 C03 ...... 72 59 tr tr 0 0 HC03...... 1,160 1.880 355 470 795 660 T.S ...... 4.246 7,553 30,038 6,207 3.225 2,r81 pH ...... 7·95 6.65 Source ...... DST DST Treater Swab DST DST Depth ..... 3,366-3.456 4.06'-4. I 08 5.209-5.279 7.322-7,404 7.583-7.631

Wertz the most part yielding gas with a much The Wertz oil field, Sweetwater County, higher content of inerts. is an elliptical dome on an anticlinal axis It is interesting to note that beds of paralleling the Sweetwater uplift. Principal Jurassic age in one area will yield water of oil production is from the Tensleep sand primary characteristics, and in another stone, younger formations yielding gas. area secondary characteristics will domi There are no serious water problems in this nate. The type of water appears to be field. Representative analyses are as related to the occurrence of limestone in follows: the Jurassic beds, a secondary water similar to post-Triassic water being produced when

Sundance Tcnsleep Amsden limestone predominates. This, of course, leads to the assumption that the charac Na .. 1,657 1.856 4.7 27 teristics of oil, water and gas depend to Ca. .... 0 376 4 61 Mg 0 43 127 some extent at least upon the petrography SO, ...... 0 3.050 3.728 CI. .. 1,078 942 4.21 4 of the rocks . C03 ..... 72 0 0 In most oil fields of the state there are HC03.. 2.395 795 2,600 T.S. 3.985 6.658 14,536 pH sufficient differences in concentration and Sour~~ : Lead line DST Lead line compOSitIOn of the various formation Depth .. 4. 100-4. 150 6,643 6.000-6.336 waters to make identification relatively JAMES G. eRA WFORD easy. In some of the newer fields in which and character of water in a structure. formation tests were made by drill stem Commercial oil and gas fields in this region these differences are not now so marked yield, associated with hydrocarbons, saline because of drilling-water contamination, and alkaline, dilute and concentrated and but analyses after wells have been on pro fresh and stagnant waters such that no duction will eliminate this contamination. particular criteria can be found to distin The most difficult correlations to make guish between productive and nonproduc are those involving Embar and Tensleep tive structures. waters. Usually, but by no means always, The value of water analyses as a means Embar waters carry a greater proportion of of identification of intrusive water in a well sodium sulphate, a higher alkalinity, and bore has been proven by field application of are more concentrated. Both waters usually the data obtained in the laboratory. contain hydrogen sulphide.

CONCLUSIONS BIBLIOGRAPHY OF ROCKY MOUNTAIN

It is evident from the generally dilute WATERS Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 nature of the Rocky Mountain oil field 1. N. H. Darton: Preliminary Report on waters that considerable modification and Artesian Waters of a Portion of the Dakotas. U. S. Geo!. Survey 17th Ann. dilution of the connate waters has taken Rept. (I895-I896) 605-694. place. The characteristics of some of the 2. B. Coleman Renick: Base Exchange in Ground Water by Silicates as Illus waters seem to indicate little change since trated in Montana. U. S. Geo!. Survey deposition so it must be concluded that Water-Supply Paper 520-D(I924) 53-72. 3. B. Coleman Renick: Some Geochemical for these waters deposition occurred in a Relations of Ground Water and Asso modified sea water; some present day ciated Natural Gas in the Lance Forma tion. Montana. Jnl. of CeDI.. (I924) 32, waters point to extensive modification since 668-684. 4. E. L. Estabrook: Analyses of Wyoming deposition, so it must be concluded that for Oil-Field Waters. Bull. Amer. Assn. these ground water circulation has been Petro Geo!. (March-April. 1925) 9. (2) 235-246. active and extensive. 5. E. M. Parks: Water Analyses in Oil Pro In general, oil-field waters in this region duction and Some Analyses from Poison Spider. Wyoming. Bull. Amer. Assn. ha ve been influenced by the petrography of Petro Geo!. (I925) 9 (6) 927-946. the rocks in which they occur. Calcium and 6. Frank Reeves: Geology of the Cat Creek and Devils Basin Oil Fields and Adjacent magnesium are absent or present only in Areas in Montana. U. S. Geo!. Survey small amounts in those sandstones in which Bull. 786. Pt. 2. Mineral Fuels (I926) 39-98. limy breaks are at a minimum, but sec 7. J. S. Ross and E. A. Swedenborg: Analyses of Water in the Salt Creek Field Applied ondary characteristics are prominent in to Underground Problems. Trans. AIME limestone and limy formations. (I928-I929) 82. 207. 8. W. T. Thom. Jr. and E. M. Spieker: The Hydrogen sulphide usually is present in Significance of Geologic Conditions in waters of pre-Triassic formations, and, Naval Reserve NO.3. Wyoming. with a Section on the Waters of the Salt Creek where present in waters of Jurrasic or Teapot Dome Uplift. by Herman Lower Cretaceous age, it is noticeable that Stabler. U. S. Geo!. Survey Prof. Paper I63 (I93I) 64 pp. limestone or sulphate-bearing waters also 9. R. Clare Coffin and Ronald K. De Ford: Waters of the Oil and Gas-Bearing are present. This lends credence to the be Formations of the Rocky Mountains. lief that hydrogen sulphide is a product of Problems of Petroleum Geology (Amer. Assn. Petr. Geo!.. (I934) 927-952. bacterial action in which sulphate, either in 10. James G. Crawford: Oil-Field Waters of the water or in the rock, plays a leading Wyoming and Their Relation to Geologic Formations. Bull. Amer. Assn. Petro role. Geo!.. (1940) 24 (7) 1214-1329. There appears to be no relationship be I1. James G. Crawford: Oil-Field Waters of Montana Plains. Bull. Amer. Assn. tween presence or absence of commercial oil Petro Geo!. (I942) 26 (8) 1317-I374. 286 WATERS OF PRODUCING FIELDS IN THE ROCKY MOUNTAIN REGION

12. James G. Crawford: Characteristics and arisen to establish a basis for mathematical or Significance of Oil-Field Waters of Rocky Mountain Region. Mines Mag., quantitative interpretation of the three curves: Colo. School of Mines, 9th Ann. Petr. the self potential in milli vol ts, the normal and issue. (Sept., 1944) 34 (9) 47 0. the lateral resistivity in ohms per cubic meter. It is not the intent to try to present a technique DISCUSSION in these comments but rather to call attention T. C. HIESTAND*--The author touches on to the important factor of water analysis in the controversial matter in stating premises upon interpretation of electric logs. which correlation of water analyses is based. Progress investigations in these fields indi Geochemically, however, it appears to be defi cate that reservoir formations commonly have nite that characteristics of the producing water low permeability ranges, that the water con do serve the purpose of correlating the analyses centrations are usually less than 12,000 ppm, with respective reservoir zones, and that is and that the subsurface API gravities of the 0 the importan t poin t in engineering. Geologically crudes are seldom in excess of 40 • It is com it appears that water pressure in each reservoir monly found that the closed structural uplifts zone is commonly hydrostatically adjusted to on which fields are developed contain wells present depth, also that oil and gas accumula which produce only water one-third of the Downloaded from http://onepetro.org/TRANS/article-pdf/179/01/264/2178839/spe-949264-g.pdf by guest on 26 September 2021 tion is adjusted to present structural conditions vertical height up from the lowest closing with minor exceptions. In other words equilib contour, towards the structural apex. Above rium exists in the fields, a majority of which are this contour apparently oil-water intermix situated at the flanks of Rocky Mountain zones occur, the penetrated distances of which ranges. Under equilibrium it appears that any range from the order of 10 to 50 ft, or possibly hydraulic action between entry points at ex greater. In this zone the ratio cf producible posures adjacent to mountain uplifts and water in wells diminishes gradually up dip. discharge points at river levels maintains Above this zone the producible oil is com volumetric equalization. Geochemically, analy monly water free. In order to establish factors ses reflect the cumulative complications which which affect maximum efficient rates of daily have occurred subsequent to deposition of production of oil and water, respectively, for reservoir formations as unconsolidated sedi each well in fields, I believe it is economically ments, down to burial in geological basins, then important (1) to obtain water analyses, (2) to recurrent uplift, folding, and erosion during make mathematical or quantitative inter mountain building. Hence, the explanations of pretations of the electric logs of the reservoir variations in concentrations of waters are formations, and (3) to check these results controversial. against the core analyses of the reservoir With the advent of electrical logging in formations. recent years, the necessity for detailed analyses Therefore, I believe, the author has con of reservoir waters in oil and gas fields has tributed valuable background data for the use of the reservoir engineer as well as the develop * Cities Service Oil Co .. Casper, Wyo. ment geologist working in this region.