NORTH DAKOTA GEOLOGICAL SURVEY

Wilson M. laird, Stote Geologist Report of Investigation Number 22

NORTH DAKOTA'S NESSON ANTICLINE

by Wilson M. laird and Clarence B. Folsom, Jr.

Reprinted from World Oil, March, 1956, and June, 1956

GRAND FORKS, NORTH DAKOTA, 1956 A 2 J-year search for oil ended in J95J• Now additional important fields are focusing at­

FIGURE I-Location of the Nesson anticline tention on ... in the Williston Basin.

North Dakota's Nesson Anticline

Here is a discussion of the geologic and production characteristics of the area and a detailed description of operating problems.

By W. M. LAIRD and C. B. FOLSOM North Dakota Geological Survey, Grand Forks, N. D.

THE NESSON ANTICLINE is a geo­ ~issouri River. The only crossing of the present Capa field. The earlier logic freak subdividing the vast Willis­ available to vehicles are the bridges at well did not penetrate deep enough ton Basin. Exploratory effort seeking Sanish and 50 miles to the west at to test the Madison formation which petroleum reserves has combed the Williston. is now the principal producing surface and subsurface secrets of this The Missouri river cuts through the horizon. structure for the past three decades. Nesson anticline about 30 miles east The Kamp well of the California Yet, production in commercial quanti­ of Williston. The river being the prin­ Company was drilled in 1938 to 10,­ ties was not uncovered until 1952. cipal route of trappers and explorers, 281 feet before finally being aban­ The structure extends roughly in a it is probable that the gentle arching doned due to stuck drill pipe. The north-south direction from the Cana­ of the sedimentary beds along the geologists, at that time, were unable dian border to the Little Missouri north bank was noticed in the early to correlate the forma tions in the River, although the northern part of 1800's. It was not until 1920 that a lower half of the hole and it was not the structure is not known from sur­ well was drilled in the Williston area, until several years later that these face indications. seeking oil and/or gas. This early well formations were identified positively. From the Canadian border to the was drilled by the Pioneer Oil and It is possible that the well could have Missouri River, the area is a typical Gas Company about two miles south­ yielded commercial production from glaciated plain on which dry land east of Williston. It was completed the Madison had not an unfortunate agriculture is the principal industry. in 1920 as a dry hole and little else is chain of circums tances occurred. In the immediate vicinity of the Mis­ known about it. When the well reached the depth at souri River and the Little Missouri In 1935 and 1938 two more wells which it is possible that oil might have River, the topography becomes more were drilled within a half mile of been encountered, the crew was en­ rugged with sharp ravines cutting into each other about 1Y2 miles northeast gaged in changing from rock bit to the plateau surface. In this region, of the town of Hofflund. The first core bit and jetting pits. The samples numerous buttes stand out promi­ well was the Big Viking Kamp I, and from this interval are noted as "badly nently above the general level of the the second was the California, Kamp contaminated." terrain and grazing is the primary I. Although both wells were aban­ On the third of September, 1950, industry. doned as dry holes, they are only a the Amerada Petroleum Corporation The producing area of the Nesson mile from present production and are spudded its Number 1 Clarence Iver­ anticline extends to both sides of the direct offsets to the field boundaries son, five miles north and 2)12 miles east R96W R95W R94W son well totaled 3092 barrels of oil from the Silurian. After plugging back, the well produced 17,408 bar­ , rels of oil from the Duperow (De­ , " vonian). In December, 1951, the Iver­ son well was plugged back and re­ completed in the Mission Canyon for­ mation of the Madison group for initial production of 677 barrels of oil per day. The Amerada Bakken 1 was spud­ ded in June, 1951, about 12 miles north of the Iverson and drilled to 13,709 feet. Casing was run and sev­ ',I eral intervals were tested. The well ...... was completed as a producer through " ... perforations in the Mission Canyon from 8312 to 8350 feet on April 14, 1952. -P The field discovered by the Clar­ ~ enCe Iverson was named the Beaver Lodge, although the first production from the Beaver Lodge-Madison pool was obtained from the Palmer Dil­ J... land 1. The Bakken well is considered the discovery well for the Tioga field. ,~..,.-+--+-~=I--I--I~f __-L+~__. >~ , "~-----f---+--A------b-~r-~_ I : ~/:.t-l-:1/ Development continued rapidly in .._I;/( these new fields and new discoveries I ( /1, ~,/: / I I -L,-----j T 156N were made during 1952, when the Charlson and Croff fields were opened south of the Missouri river. The Croff field was at the southern end of the anticline about eight miles north of the Little Missouri river. In 1953, the East Tioga field found production on ~ the east flank of the anticline and \~f~ TI55N the Hofflund field was opened south­ c'. east of Beaver Lodge. The McGregor ',1 1 t-· field on the west flank was opened in ~L_I [\, 1954, and the Capa field was dis­ covered in 1953 to the south of the 1,1--:-LJ--H·····'rr-rTYTT/f I': Beaver Lodge, and west of the Hoff­ lund field. " At the present time and under cur­ " Tl54N rent orders of the North Dakota State Industrial Commission, the oil and gas regulatory authority for the state, the Beaver Lodge and Tioga-Madison pools are almost completely developed.

Regional Geology. The Nesson anti­ cline is a structure which has been known for many years. From the be­ FIGURE 2--Structure on top of the main porl/sity, north half. ginning of history probably many of the early travellers crossing this terri­ of the 1938 well. The well was drilled Drilling was reswned and the well tory looked at this area without know­ to 11,744 feet and casing was set. Sev­ was deepened to 11,955 feet. It was ing the exact meaning of this large eral intervals were perforated, tested, plugged back and perforated in the fold. It was first mapped geologically and plugged before oil was recovered Devonian from 10,490 to 10,530 feet by Collier in 1918 and his report was from perforations at 11,630 to 11,660 and the rig was released July 22, 1951. published as one of the Bulletins of feet in the Silurian. The well flowed Initial production from the Devonian the U. S. Geological Survey. 307 barrels of oil and 25 barrels of was 290 barrels of oil during the first It will be noted by looking at the water in 17 hours ending at 5 a.m. 24 hours. index map of the area (Figure 1) April 5, 1951. The first production from the Iver­ that the Nesson anticline is located in the approximate center of the Willis­ R96W R95W R94W ton Basin. The structure is more or "t I I 1--, r.. II« • ::':"-4"DD~ I\ 1/ less isolated and not apparently re­ / lated to any other fold in the basin. l-n Its structural trend diverges from the b /, :;jJ " ~ TI54N nearest large structure in the general area, namely the Cedar Creek anti­ cline. It will be noted that the Cedar Creek anticline trend is in a north­ west-sou theast direction whereas the '" ' ' .... 17' trend of the Nesson anticline is almost i due north and south. Undoubtedly, there is some genetic relationship be­ /1 il I tween this fold and other folds in and on the margins of this basin but as yet evidence is not sufficient to make a . . I positive statement as to this relation­ \ / f7 ship. As more geophysical work is " , , =tIl done and more wells are drilled bring­ 0 f\ :1 \1\ I #0.,0 ' ing more information to light, more \, ~'i--- JI I 1/ accurate hypotheses as to the relation­ '. T152N ship of the various folds in the basin can be made. ~ I I /

The Nesson anticline is a rather f"\ '0 low, broad regional type of structure ~ with a closure of probably less than 100 feet. On this structure, however, rtf are smaller domes which are some­ ,./ what higher structurally. (See Fig­ \ 1 i ' Tf51N F\" ... " I I ,/ ure 2.) f\-. v "'T-::T. '8£8/. When the structure contours are "­ / drawn on various horiwns in the area ----r 1\ ,l' / of the Nesson anticline, it has been '" 1/ found that there is a migration of the ~_L.T' ~ 1/ axis of the fold with depth. The struc­ - ture on the Greenhorn formation in ". ," the Cretaceous section is approxi­ ,­ TI50N n "- .~ mately a mile east of the structure on fili~ top of the pay horizon in the Mission /"'1/' .. :/' /, , Canyon formation. Insufficient evi­ =k\ " \ ...... :... - dence is at hand to indicate whether ~' the axes on the lower formations par­ ,,/ I ticularly in the Devonian and Silurian '" '\ l/ diverge from the position of the Mis­ llllJ-j ~T149N sion Canyon axis. However, from the m few wells which had been drilled in "D/=tH++-+ ± the area, it is suggested that the top 1--+..··1 I I 1 1 I I I I I I I I of the structure on the Devonian and D Silurian may even be farther west than that of the top of the Madison. R96W R95W R94W Unpublished geophysical work done FIGURE 2a-Structure on top of the moin porosity, south holf. by the North Dakota Geological Sur­ vey would suggest that there is con­ magnetic axis then trends eastward various formations in the area suggest siderable rclationship between the and the magnetic high more or less that this movement started probably magnetic highs and the actual struc­ coincides with the structural high in sometime in the latter part of Ordo­ tural highs on the top of the pay the Tioga field. vician time and became more active horizon. There is a marked corres­ The origin of the folds must be con­ as time progressed. Probably, it was pondence between the magnetic high sidered in any structural picture of most active at the end of the Paleozoic. and the Charlson field as well as a this area. It has been suggested that It is felt that this is not a simple correspondence between the magnetic the Nesson anticline is due to vertical fault arching the beds above it, al­ high and the Capa field. However, in movements in the basement rock. The lowing the beds to be draped over in the case of the Beaver Lodge field, movements have been apparently in­ a normal plains type fold. Very likely the magnetic high is somewhat to the termittent over much of Paleozoic and as the structure was uplifted inter­ west of the structural high, but the subsequent time, Isopach maps of the mittently, other faults, particularly ment of all the iormations found in "ECUT AU.U.V~ I"I.IIITOCIM: IUCIAL DR'" this particular area. In general, at­ P\.1Oe:t:Nl PMoI"LfJSTOCEN£ 6RAVELS tention will be paid more to the II\ocDUE Madison group of fonnations than any OUtOClNIt: tntITIt: RIVER T["TIARY other since these are the oil produc­ EOCOlIt: __If VAU.E:Y UNT1NEL IIUTTE J ing rocks in fields under discussion. "AU:OCENE TONIUf RIVER FORT UNIOfl GROUP (See Figure 3.) ~ LUDLOW CMNONSALL The rocks below the Madison group tC1.L CREEK QIiiBl FOX Jm.LS of fOlmations are not too well known MONTANA GROUP MRM: in this area because relatively few ~ wells have penetrated them. However, CARLILE COLORADO OflOU.. it is known that rocks of Ordovician, "'([NHORN Silurian, and Devonian age are found CRETACEOUS KLLE FOURCHE IIOWIlY on the Nesson anticline. Beds repre­ \IIl1JCASTLE "\llUOOY" senting the Cambrian may also be S«ULL CREEK DAKOTA GROUP present. The Silurian and Devonian "ALL "'VEl' are both known to be productive in fU~ the Beaver Lodge pool and also pos­ LMOTA sibly the Tioga pool. Rocks of Ordo­ I I I I I I I I I I vician age have had some shows of IIICIlUQON I oil in the Tioga pool, but it is not ~URASSIC SUNDoIHct known if they are commercial. PtPOl The Ordovician through the Si­ I I I I I 1 lurian is rather largely a carbonate TftIASSIC SPEAftI'18H sequence with the exception of some T T I I I I clastic sequences at the base and the PER"'LAN MINNEKAHTA top of the Ordovician. The most OPECH[ prominent clastic zone in the section PENNSYLVANIAN MINNELUSA ~------"AMSoa;"-- -­----­--­ above the Devonian is the Englewood HEATH formation of Mississippian age where OTT[R 811 SHOWY GROUP shales and some small amounts of KIB8[Y sandstone are found. Evaporitic sec­ MISSISSIP..IAN CHARLl:e tions are known in the rocks of all MISSION CANYON MADISON GROUP three of these geologic ages, but the LOOG£POLf: thickest section of the evaporites be­ EHGL£WOOD T I I I I I low the Charles formation of the LYLETOH QU'Arl"£LLE GAOUP Madison group occurs in the De­ "NISKU" vonian. Apparently, tltis portion of SASKATCHEWAN 6Po DUPEROW the basin became extensively evapo­ SOUfttS RIV!" BEAVERHILL LAKE DEVONIAN ritic in nature toward the end of mid­ DAWSON BAY I"OUP dle Devonian time. This evaporitic PRAiRIe EVAP./ condition recurred more frequently WINNIP(10lna ELK PO..T "'OUf" from Devonian time onward culmi­ ASHDtII T T I I I I I I I I nating in the Charles formation in all.UIIIAN INT!"LM[ MOUP upper Mississippian time. STONY MOUNTAIN UP1>t:" Definite unconformities do exist in '--­ LOWER the whole stratigraphic section indi­ OftDO.VIClAN "ED "'VEl' cated here. The unconformity at the WINNlPlI base of the Ordovician is well known T 1 I I I I c...... particularly on the east side of the call1llt'AN 1 I I I I I Williston Basin. Here in most cases, the Ordovician rests unconformably FIGURE 3-Preliminary correlation chart of the Williston Basin. on the Pre-Cambrian granite. There is some thought that rocks of the cross faults, were developed. This is anticline is due to vertical uplift prob­ Cambrian age may be present, but suggested from the rather sharp dips ably due to a faulting in the basement this has not been definitely proved. If in the pay formation as it passes from rock. This uplift has been intermittent such is the case, then the greatest un­ field to field particularly between over much of geologic time causing conformity, of course, exists at the Beaver Lodge and Tioga as well as by not only structural but also sedimen­ base of the Cambrian. the irregular behavior of certain wells tological irregularities adjacent to the The sedimentation between Ordo­ as to water production and pressure site of this particular fold. vician and Silurian time was almost histories. It is impossible in the space allotted continuous and no great evidence of Therefore it is felt that the Nesson to give a detailed stratigraphic state­ a break does exist. However, there is some suggestion of a break in sedi­ Slsslppian age. The Amsden in North where it is both intergranular and mentation between the Ordovician Dakota is for the most part, regarded vuggy. This porosity is the main pay and Silurian in the outcrop areas in as being Mississippian. From the south wne of the fonnation in the Nesson Manitoba. However, this is definitely to the north in the Nesson anticline anticline pools. a minor break if it did exist at all. area, there is a very considerable l In the H. O. Bakken well in the W. S. McCabe indicates that there unconformity at the top of the Ams­ Tioga field, the fonnation is 450 feet is an unconformity on the top of the den formation making a marked thin­ thick. A contact with the underlying Silurian. This is very difficult to as­ ning of this formation northward. Lodgepole is conformable and the certain in the subsurface. McCabe upper contact of the formation is also places another unconformity at Madison Group. The Madison definitely gradational with the the top of the Devonian at the base group of North Dakota consists of the Charles. The top of the Mission of the Englewood. This also is some­ Lodgepole, Mission Canyon, and Canyon in most cases is drawn at the what difficult to see in the subsurface. Charles formations reading from bot­ base of the last large salt of the A greater amount of evidence exists tom upward. The group as a whole Charles formation. This, however, is for it than the one between the Si­ is rather widespread throughout North a purely arbitrary boundaly in view lurian and Devonian. Dakota, but the distribution of the of the facl that it is the opinion of Some discussion of the rocks over­ Charles forma lioll is more limited the writers that the Charles formation lying the Madison group also is per­ than the other two. It is largely a is simply a result of the continuation tinent. Remarks, however, will be con­ carbonate and evaporitic sequence. of Mission Canyon conditions of sedi­ fined to discussions of the rocks which The Lodgepole formation is a gray mentation and therefore no actual are of Mississippian age. Immediately to brownish limestone with a dense to break between the two actually exists. overlying the Madison group is the finely crystalline to medium crystal­ The Charles formation in the Big Snowy group of formations. The line texture. Sometimes, the texture Beaver Lodge and Tioga field con­ basal member of this is the Kibbey may be medium fragmental to sists of pale brown to light gray, sandstone. Sloss2 suggests that the coarsely fragmental. It may also con­ shaly, fine fragmental limestone with sands of the basal part of the Kibbey tain some chert, shaley limestone and some brown shale. It is characterized indicate an unconformity. This is cer­ some shale. The color of the Lodge­ by some dolomite and several rather tainly true in the ~ontana portion of pole may vary from white to a pale large anhydrites. The salt section of the basin whcre they are exposed on orange and pink in color. In the the Charles disappears to the east the flank of the Big Snowy moun­ Tioga pool, the fonnation is 1030 feet 3 rather rapidly, apparently due to tains. McCabe has recently reiterated thiclc The Lodgepole is normally the facies change. It is also possible that this conclusion. These unconformities thickest of the three formations of the the salt, as such, is not deposited in are not obvious in the subsurface and Madison group and rests with ap­ the other parts of the state and that sO the contact between the Kibbey and parent conformity on the Englewood there is an unconformable relation­ the underlying Charles is not always or Bakken formation. The age of the easily drawn. Overlying the Kibbey Lodgepole is Kinderhookian. The ship with the underlying Mission are the Otter and Heath formations, presence of chert and other argil­ Canyon. However, facies changes are respectively, which are largely shale laceous limestones suggest that the for­ apparently the most likely explana­ formations. They do, however, in some mation may have been deposited in tion. In the Tioga field, the Charles instances, contail) small arnouncs of deeper water, but the fragmental part formation is 630 feet thick. The rela­ black and other colored limestones. of the limestone suggests shelf-like tionship of this formation to the for­ Overlying the Rig Snowy group is conditions. mations above and below has already the Amsden formation. The Amsden The Mission Canyon fonnation is been discussed. formation is of controversial age, geo­ generally a light gray to bright gray logically speaking. Recently, it has limestone with some oolitic to frag­ REFERENCES been regarded by many as being mental as well as dense to finely crys­ 1 McCabe, W. S., Williston Basin Paleozoic Un­ coroIormili." Amer. AssD. 01 Pet. Geologis19 Bulle­ largely Pennsylvanian in age. How­ talline texture. The porosity of the tiD, Vol. 38, Page, 1197·2010. 1954-. Z Sloss, L. L' l Paleozoic sedimentation DC Moo. ever, there is some evidence that sug­ formations is most marked about 200 lana area: Amer. Assn. of Pet. Geologists, Bulletin. Vol. 3'!< Pages 442-553. 1950. gests that the basal portion is of Mis- feet from the top of the fonnation 3 MCLabe, W. S" op cit. North Dakotals Nesson Anticline

Madison Problems Are Unusual

• Average permeabilities from core analyses figure of 7.82 percent can be used for the porosity of the Madison pay in­ give a distorted picture. terval in calculations of reservoir volume, without inducing serious dis­ • Total production interval 200 feet ... but crepancies in the results. net productive thickness is but 60-70 feet. In using electric logs for reservoir calculations a formation factor of • Pressure declines below bubble-point are 23.746 is suggested for fluid having 150 ohms per cubic centimeter and found in some fields. 5000 ppm NaCI or 79.296 for fluid of 4.8 omns per cc. Although the total interval in which By W. M. LAIRD and C. B. FOLSOM production may be encountered totals North Dakota Geological Survey, Grand Forks, N.D. 200 feet, more or less, the net produc­ tive thickness for the pools is about

THE PAY INTERVAL in the Beaver vugular porosity, or fracturing. 60 to 70 feet. Lodge and Tioga-Madison pools oc­ Coring times in the pay generally The proven area for the Beaver curs about 200 fcet below the base of drop La 10 minutes or less per foot Lodge and Tioga-Madison pools is the last Charles salt. The porosity is from the normal drilling rate of 20 or considered to total 41,200 acres wi th indistinguishable to the naked eye ex­ more minutes per foot. 25,000 of this within the prescribed cept where vugs occur. A 30x lens is The average permeabilities taken limits of the Tioga-Madison pool as required to see the individual pores. from core analysis give a distorted presently defined. The Beaver Lodge­ Cores of the formation exhibit both picture of the existing conditions since Madison pool is well outlined by dry horizontal and vertical fractures which the majority of the pay interval has holes and the Tioga-Madison pool is are frequently secondarily filled. horizontal permeability less than 0.01 well defined except for the eastern There is some doubt as to whether of a millidarcy. The isolated intervals boundary where some possibilities for the fractures seen in cores are natural of high permeability result in averages step-out production may exist. or induced in the coring operation. It over the length of the core, ranging Although the "pay" interval ap­ would seem logical, however, that a from 0,6 millidarcys to 34.8 milli­ pears to be continuous between thick limestone such as this would ex­ darcys. Beaver Lodge and Tioga Pools, they are presently divided into separate hibit fracturing, particularly where In testimony before the North units on the basis of a dry hole and folding or other structural movement Dakota State Industrial Commission, two marginal producers which have has occurred. a consultant from Houston computed been abandoned. In the same area, The problem of the cross faulting in permeabilities from 5.7 to 58.4 milli­ there are still a number of producing these fields has been mentioned pre­ darcys in Beaver Lodge and from wells which are considered marginal. viously, Evidence for it at best is in­ 116.1 to 168.9 millidarcys for Tioga, Water production from these wells has direct and it is not implied that the from production data. In view of the been noticeably greater than in the faults if present, have completely dis­ fact that actual laboratory tests indi­ developed areas to the north and rupted the continuity of the pay hori­ cate low permeability, the producing south. zon but it would account for some of characteristics of the fields would sug­ In this area, there is also a struc­ the problems that arise such as local gest, rather strongly, that drainage in tural difference of 50 feet over the areas of high water production, varia­ the reservoirs is due to fractures. mile and a haU which separates pro­ tions in water level between pools, and Oil saturation varies from 0 to 87.5 occurrence of dry holes where adja­ duction. A similar condition prevails percent of pore space and water satu­ at the southeast extremity of the cent development would indicate ration varies from 0 to 99.5 percent of proven locations. Beaver Lodge field where 5 producing pore space. The averages of wells wells are separated from the main Core analyses on individual wells cored indicated saturations of the producing area by a dry hole and a show porosities ranging from 22.5 to order of 9 percent for oil and 42 per­ structural difference of 40 feet in % 0.8 percent with averages of the order cent for water. of a mile. Faulting has been suggested of 7 percent. Routine laboratory tests The bulk density of the pay is 2.5 for these two areas and would account for permeability show horizontal per­ with a matrix density of 2.7. Calcula­ at least partially, for the excessive meabilities from 0 to 150 millidarcys tions of porosity based on these meas­ water production and generally poor with isolated measurements of urements give results very close to the quality of the wells nearby. 5000 +. The higher permeabilities ap­ averages of the laboratory analysis. The possible productive area for the pear to coincide with intervals of From this it is concluded that the Charlson-Madison pool is estimated H-l--Ft=r:R=r-n=t-n­ OIlIGl~A( -~ES~8 'Pll£htin;.._~; _EIJB±

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FIGURE 4-Performance c;urve for Beaver Lodge-Madison Pool. to be 13,000 acres; for the Capa­ feet in the Tioga-Madison with a at 100° F. Podbielniak analysis showed Madison pool, 5500; and for the maximum oil column of 239 feet. In 92.4, liquid volume percent, Hexanes Hofflund-Madison pool 6000 acres_ each case the maximum oil column or heavier with a specific gravity of No estimates have been made of the exceeds the closure. 0.8309 and a viscosity, at 100 0 F. of productive area in the Blue Buttes, The oil from the Madison reservoir 2.641 centistokes. Croff, and Keene fields due to the at Tioga is undersaturated, of low The characteristics of the reservoir lack of development. molecular weight, containing 1585 fluid from the other Madison pools In the Charlson-Madison pool, the cubic feet of solution gas per barrel of on the anticline are similar. Solution "pay" interval, as identified by ge­ residual oil. The gravity is 44° at gas-oil ratios are 1598, 1651, and 1952 ologists of the North Dakota Geologi­ 60° F. Reservoir temperature is 212 0 in Charlson, Hofflund, and Capa cal Survey, reaches a thickness of F. in Tioga and the viscosity was fields, respectively. about 130 feet over the top of the 0.169 centipoises at saturation pres­ It is interesting to note the increase structure. This "pay" interval is an sure of 3049 psig. The Beaver Lodge­ in the API gravity of the oil which identifiable interval on the mechanical Madison reservoir had a solution gas­ occurs up dip to the north. Readings logs and includes both porous and oil ratio of 1773 and viscosity of 0.147 for the fields, beginning with the fur­ non-porous intervals. From core analy. centipoises at saturation pressure of thest south, are Croff· -41.9, Blue sis, the net productive thickness, in 3205 psig. The gravity of the oil is Buttes--40.7, Keene--41.5, Charlson the well cored, is probably limited to 43° API at 60° and the reservoir --41.6, Hofflund--42.8, Capa--43.4, 35 feet with the total "pay" thinning temperature is 2240 F. The relative Beaver Lodge--43.0, and Tioga--44. on the flanks of the structure. volume factors for the Beaver Lodge Reservoir temperatures are Croff­ The oil water contact is placed at and Tioga-Madison reservoirs were 231 0, Blue Buttes-238°, Charlson­ 6500 feet below the sea level in the 2.135 and 1.983, respectively, at Satu­ 224°, Hofflund-228°, and Capa Charlson-Madison pool, which results ration pressure. 226° F. The viscosity of the oil is in a maximum oil column of 122 feet Evaluation data on the produced oil 0.132 cps. at Capa_ Relative volume for this pool. The water contact is from these fields showed a total sulfur factors are 2.064 for Charlson, 2.083 placed at -6260 in the Capa-Madi­ content of 0.34 percent and a Reid for Hofflund, and 2.261 for the Capa son pool with a maximum oil column vapor pressure of 7.4 pounds. The field, at saturation pressure of 3211 of 70 feet; -6155 feet in the Beaver pour point is 35 0 F. with 3.5 pounds psi, 3085 psi, and 3302 psi respectively. Lodge-Madison pool with a maximum of salt per 1000 barrels_ The Kine­ The reported GOR for the Clar­ oil column of 138 feet; and -5925 matic viscosity was 2.135 centistokes ence Iverson well in the Madison pool 'ORIGINAL RESERVOIR PRESSURE - ~69$ PSt9 "QI~JO:' rHlllllllllllrn I·::p:j (HE Rlnrvl)l' p,..is'u;~:.·~ TIOGA - MADISON POOL LLUG IITIll£U 1I1I1111111111 P~rfQrm(]nce Curves

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.'

19_ I 1a_ I la_ 11~ I 19~ I '9~ I u~ I 19~ I 19_ lli'_

FIGURE 5-l'erformance curve for the Tioga-Madison Pool. in Beaver Lodge was 1211 cubic feet dropped below saturation pressure. are corrected to the datums for each per barrel, initially, The average gas­ This break coincides with the increase pool:-6100 for Beaver Lodge and oil ratio for the field was varied, in production, from 355,000 barrels -5850 for Tioga. If the pressures for reaching a low of 1062 in the first per month to 800,000 barrels per the Beaver Lodge curve are corrected quarter of 1954. Since that time, it month, that occurred when the mar­ to the Tioga datum, there remains a has increased steadily to its present ket demand increased at the end of difference of about 50 psi between average value of 1374 cubic per bar­ 1954, the curves. rel. (See Figure 4) . Some consideration has been given This would indicate that the two In the Tioga field, the initial GaR to the possibility that this interrela­ pools are not connected, although for the discovery well was 1094 cubic tion between production rate and their performance is similar, and that feet per barrel. The lowest ratio, 1001 pressure reaction indicates the ap­ the drainage mechanism is the same cubic feet per barrel was reached dur­ proximate MER in each case. On this for both pools. This, together with ing early 1954 and the present average basis it would appear that produc­ the GaR behavior, would suggest the value of 1273 cubic feet per barrel tion should be stabilized at about the presence of depletion-type drainage. represents a steady rise. (See Figure rate prevailing during 1953. How­ When the actual pressure decline is 5) . ever, a different idea is suggested plotted against the mathematically Both pools have now declined in when actual declines are compared determined curve, it can be seen that pressure below bubble point. Satura­ to the theoretical curves for the fields. both pools have followed the theo­ tion pressure was passed during the Simple mathematical equations retical curve closely. In the case of first half of 1955 for both fields, Pres­ which would represent the natural the Tioga-Madison pool, the actual ent average bottom-hole pressures are relationship between reservoir pres­ decline is still above the theoretical 3079 psig and 3015 psig for the Bea­ sure and time are as follows: curve and the actual curve for the ver Lodge and Tioga pools, represent­ • Beaver Lodge-Madison pool Beaver Lodge-Madison pool has been ing declines of 616 and 646 psi, re­ coincident for practical purposes. On Log P = 3.58218--0.00240 t spectively. the basis of these curves, it appears The pressures in the two pools have • Tioga-Madison pool that the MER for the two pools is declined similarly. The decline had Log P = 3.56761--0.00226 t about equal to the current withdraw­ been following a uniform curve until Where P is reservoir pressure in psig als at this writing. January, 1955. Since that time, both and theis time in months, At the beginning of the second decline curves have broken sharply, It can be seen that the two curves quarter of 1955, the average of the still moving parallel, and have are very similar. The pressures used productivity indices of individual Ot!90~: l:F.!0RIOINAL RESERVOIR PRESSURE ­ 38&8 I+F ,.,,'I=l=I=+. =,T­ -'..!-J~R=JCI..J.,H-!" .• i I I I I rr'-I ii' I i i±tHf ftWl'­ Pr'"'II,.f":'t~_f~:·~- 5700 RHerTOlr ':tCAPA - MADISON POOL: . T··'·' 1""+""+"+=~:lhrJ Iii L iii ! , ii, I I j 1::J..J::w:t: ~~riQ.l'm~nCe Curve.s -'.. ..=:f:t·~· IiI' c .,. I SATURATION PRESSURE 3302 P.ttI or f'rodaolnt OOi/OllTifl 'ilil~:'~ ~HH ··i· u iilmSil·~ ~ ., ·r -' '"..~ _(...en.. ~ .., <>z.. 1+ '0 ..u I ~ 1l % 0 :l: 2 _~ Cumulative -olf PrOduction -' (5 >­ ~tiOl~ ..li :> §±t . 1001 /:1100-'::' ~ I Go."Ift Wa,tir-..rodiooll•• Him

FIGURE 6---Performonce CUrie for the Capo-Madison Pool. wells in the Beaver Lodge and Tioga­ of oil per psi for the Tioga-Madison MER of these pools since the produc­ Madison pools were 122.27 barrels of pool. tion of oil will be regulated by these oil/psi, pressure drop, and 90.95 bar­ The original gas-oil ratios for the two factors. rels of oil/psi respectively. The dis­ other Madison pools were: Croff 1501 In a conflict of interest between the tribution of the indices is shown in cubic feet per barrel, Blue Buttes 1020 consumers of the natural gas and the Table 1. cubic feet per barrel, Keene 1296 responsibility of the state to prevent TABLE 1 cubic feet per barrel, Charlson 949 cu­ waste of oil, the state will exercise its Productivity Index-Rbis/psi bic feet per barrel, Hofflund 1570 police power to regulate the oil pro­ Number of Wells In Each Group cubic feet per barrel, and Capa 1167 duction. cubic feet per barrel. (See Figures In attempting to compare these PI 6, 7, and 8). Although some varia­ estimates of reserves with earlier, sim­ ()- 50. 14--1 13 50-)0<1. 5\ I )05 tions have occurred between succes­ ilar, estimates, it should be remem­ )()()-150.. 71 I 26 150-Z00...... 18 ~ sive measurements, the present gas­ bered that the boundaries of the two 200...... 4 I oil ratios are between 1150 and 1350 pools were changed by the State In­ Tol.ll!... 158 1-~5- cubic feet per barrel, in these fields. L dustrial Commission in its orders of Estimated recoverable reserves of October 29, 1955. From the table it can be seen that crude oil for the Beaver Lodge and Reserves have been estimated for Tioga appears to be the more uni­ Tioga-Madison pools are 95 and 150 the Charlson, Hofflund, and Capa­ form of the two pools. Whereas more million barrels, respectively, as of Oc­ Madison pools at 45 million, 20 mil­ than % of the wells checked in the tober 1, 1955. lion, and 35 million barrels respec­ Tioga-Madison pool had indices be­ Total recoverable wet gas, avail­ tively. tween 50 and 100, only Y3 of the able, for sale, after processing at the Operators seeking to establish pro­ wells in the Beaver Lodge-Madison Signal Oil & Gas Company's Tioga duction in the fields of the Nesson pool fell within this range with an ad­ plant is estimated to be 265 billion anticline are faced with a number of ditional 45 percent having indices be­ cubic feet from the two reservoirs. unusual problems not ordinarily en­ tween 100 and 150 barrels of oil per The deliverability of these reserves is countered elsewhere. Since the Madi­ psi. The ranges of productivity index important and it should be recognized son limestone reservoir lies directly encountered were from 15 to 536 bar­ that the amount of gas available on beneath the Charles formation, all rels of oil per psi for Beaver Lodge­ any day will be dependent upon the wells must penetrate 200 to 400 feet Madison and from 16 to 388 barrels market demand for crude oil and the of crystalline salt section. The early "" ;:OJ' -It.! _~c:-l1~ffa -!.::-~~1~~~~~~m~m~liw~mitmjmlmjmMlmlmi~'" " .. '~~' ,-' 51JH~3011: fUfffm:fp:.:w:tUJj~H++ j:j:_ . i-ttl .t: ~ ~ -.1::' H,-' J:tf+l-".~(: -,- -::EE.=r-' cf:~E:hl H=[LLlH-tc.-i:r..;. t-I~ :L-,-~-'c.: -. . ~ Fq:E 'oofe ~ ---'~: , .. T fl_ ;=J:IF: !t._-:~lc!~!e_::-J~~R""'O~P,~ ...r':+:'_:1.:.:HOFFLUND~L~891~~:,-~~9J-,,- EJ - g.~' -~+~+,2.-~:~ ~:niJ1~ 1~Ir ,!e~?rmance, r .:.1:1:-' .i-,~ -I .. ;. '.-J ~'. ~. ~ Curves,~I- ' ,'!# ..•r+=FFFFi­I-+-l-+~ ~.: h- i' I' t, -·H·!-i-~ -~.: h= -I± -.~.~t.t ., -, ' tic. _;::.. tt[:j::t '1. .. ­ ,:rE ~- : . .: • r_ .- .. ! 1 I ,.:. r- 1--- ,+ H--·-t= • Hf-H--' t:t: H 11--.-. -©9oJ ,"131'6~0~-_f--lfJt- __ 1_1=1 i·'r _ G~FtJ ~_. t3C... ~,,;,_·c :1--1:'::- i'\ i_ I :::-:t J.-1.+I---:-. R:I-;:JL--= ~l:I±:.f :t:-i~'...., JI_; ~ tl-c1';~ -et._ltf~ ~l+ljri" +.--:r-=~--,,-j . ;t ,tJ:+::t13 _ _1< ,_ ~ ! -t! 1-1.1 . --l - j' -1:r. qJ.:!:J= .11-1£ . -:::- ,:J I-H .+ H -l: R· :r. t r I::Ht ':': ·".~I~~~~~ ~Fl; .I:t. : ~-:~ ! Tet. t ;(thJ~ I'D: 1 .:!;-~' !:l!~: J ,1#. 1 ~ :'-~,:i:rt l~': =',;: t:± i:·ft~, r:~'1 ~- ~1=!=.!-i .., --- .lJ - ,_H_,_c.:xcr:r:-...L:_I~__I-l--:,r::.'I'll~ i i"--'i-I-' ' 1:-t:j:+J:, j- .• ~ .- -' j ... l -1 .- :L ...... l,..•• h , II --I - •. - t:t::: --rr-l- 1- ...... '"'I~r~ 140'O~_ -. - -:::. 1- 'F.I. - __. '_~ If:dt~d''li!lE,'·{!?;1 r'j~i~_ i:t~+ 1-+ '~T, __ .: ~u~_ tHlt =.. .:.;.~; - -;- I--I--I--I--~ -: j I- f+ ~ ..;. _'~ 'r-U1=-::H u: ~:~I:W-';+ ';:; ; 1_ -h~j:: rtErSATURAT'ON PRESSURE '085 •• iQ, ::t -r:;:i::b'i Ii H- hH+tr Sf tE U -Ii ,- ­ ,".AO_' , ~ -&~~b 'f, "~I: ~'::-ii Ii::.; I--t e-;'H ., ,i. -- "=- !:~: _ II·r.c~ ~±: :rtn~-, :_-+J::~ ,.,-,rr··!,- 1..- ' I:-i:,. -' . : tj-, 1 ,I_~- . 1,-1 H . ,I :J±, : , '. - ":;-1-,.. -I -- -i ...]1.... ' -m- . ..,. t± f-'.H_+.. ++-HITt--H--...±_·~ ,~ ~ +- -;- I~ i::;:.W~LID1: ::t ~= :f:I-i-~ 11 .,.1 j I i-±-H+ ~ ~ ~~ t't4 : ~T -~t 1+~ :--1:: l(*:b -' .- I I- JIlII'"'_otT' --+ I 1"- 1:++ -"r-:-

et __~ _--f iiIOOO:~- -=M:J. 1: '. 11 :-' :':tJ- ,H:. li~ t -_~·ft~~ft:;'Hj-.- l±!~ .~~"' ~Tr~-...;r,b1' Oli "r.d";i~~ -1"+-' , '+if:U1Uhl: tth:: - :!:triJ±:::ttt .j-+=l+ 40 fiB cn g 0 :H~' 0 R§;:~ :"4...... ::He ~ tI) ~~ 0. o .a., ...· t::!~l_lf . ....1 ..'" ..I I Z z £ lUi o .. ..- :>u b: u . 0 ""I)j~-t~1~ -•• i-I -4 OC - oJ I ~--:-. ~ 0 =t -'+. o L~ .ERi. w--t·=n ,_.. -j 200> I:l:::±b ...... ,. ,,•',•,• , .• , ~ t= .. ~ .. : ~.CumuI4fiv. Oil Produc'iCl'! j!: :l --+- -H --t -:_ - _ + .::;=t+-t-+t;-+.,..,....,..,., ! :> --l :a a -+- .: _J -;- tj±l-t .., I I; (I~ ~ ~ j i ~ i llg J. i~ ~ ~ ~ i ! ~ ; i &l ! ~ ~ ~ : i 1! .13 ~ 1~ ~ ~ ~ ~ i i ~ '1.i i ~ ~ ~ ~ : i ~ i : l ~ 1i~ ~ i ~ i ~ ~ Ii ~ I ! ~ ~ i ~ I 1! t i i l !f: ~ ;. iii ~ ~ & ~.~ lL~ ~ ~ : I : ~ j i ~ {ii ~ :iIi ~ fi ~: jll) I ,,- I 19_ ,,_ 19~ 19-'_~ I ,,_~_L ",~_ T ,,~.L I " " FIGURE 7-Performance curve for the HoHlund-Modison Pool.

drilling programs called for a produc­ posal was not a problem. With devel­ is the possibility of fire when taking tion string of 5Y2-inch aD casing, opment nearly completed, thought is drill stem lests, due to the enclosure made up of 15.5 and 17 pound seam­ being given to the establishment of of the rig floor, such as occurred on less casing. a down-hole disposal system. One of a Penrod rig in Tioga field during the Casing was set at 10,823 feet in the the larger operators has already laid winter of 1954-55_ Palmer Dilland well in April, 1952. a system of concrete pipe for the gath­ It is estimated that the annual cost In June, 1954, it was necessary to kill ering and transportation of this water of maintaining production in these the well, and move in a workover rig to disposal wells_ It will be injected fields is about $10,000 per well; most due to loss of production. It was into the Lakota formation of Cretace­ of it as a result of the rigorous cli­ found that the casing had collapsed ous age through dry holes and pre­ mate. opposite the salt section and had viously abandoned producers on the North Dakota is now faced with a partially flattened the tubing_ Similar edges of the fields. rather unusual problem for an inland circumstances were found in other The weather constitutes another state, namely offshore drilling. The wells throughout the fields_ Although difficulty of considerable proportions_ completion of the Garrlson reservoir the exact reason for this failure has The heavy snowfall and the drifting will result in the flooding of much, not been clearly established, it is which occurs require a great deal of possibly productive land. Three meth­ thought that plastic defoTIIlation and maintenance work on roads, lease ods of developing the flooded area subsequent movement of the salt is equipment, and vehicles. Since the were considered. These were drilling responsible. pour point is only a little above the barges, earthen mounds, and direc­ tional drilling. The use of drilling In an attempl to eliminate this normal winter temperatures, diffi­ platforms or barges was discarded be­ trouble, salt base mud is now used cuhy is experienced in the mainte­ cause of expense and the danger of when drilling this section. The use nance of piping and valves. severe damage from ice. of this type mud should result in holes Drilling operations are continued One well already completed in the of uniform gage. Recent wells have through the winter at a somewhat flood-plain was raised on an earthen been cased with 7-inch OD 23 pound­ reduced rate. Rigs are winterized and mound to bring the wellhead above 32 pound-35 pound N-80 casing as a steam generating equipment is used the hig-h water level. The mound is further precautionary measure. for heating the rig and thawing lines, approximately 41 feN high with a Due to the increased use of salt pits, etc. Some hazards exist, due to 600-foot causeway to the shoreline. base mud, most of the salt water from the weather, which would not ordi­ The mound measures 60 x 80 feet at production was utilized and its dis­ narily be encountered. One of these the water line and the roadway is 30 ORIGINAL RESERVOIR PRESSURE - 4100 pOlo "r'.'0 R...,..olr P'"un '''' '-~--H-++++···'·_'·· I~~~~ CHARLSON -MADISON POOL -l-W-I-+;H I ! I I I I I I II I III -fE-­ Performance Curves

GOI/OIl Rotlo:

SATURATION PRtrsURE -nil"

..~ '11 c'" 3 ~:I: .. oirt''fY-O.~rOd,otlon ., <> lI: ..C "o <:_11... ~ -0""'''10''''

CUlIlulotiv. Wa,.,-Prodllcstlon

'0.....­

FIGURE 8-Perlormance Curve for the Chorlson-MCldison Pool. feet wide. Side slopes are 2 to 1, the directional surveys were not ac­ demand is allocated among the pools, covered with a 12-inch gravel filter curate and the well was plugged back and the wells in the pools, so as to and 18 inches of riprap. The top of from 7768 to 3555 feet where drilling distribute the market on an equitable the structure is finished with 3 inches was resumed. It is thought that the basis. A proration unit is a 40-acre of gravel and native 'scoria.' In the difficulty arose from the use of a tract of land and a normal unit allow­ causeway fill is buried a 4-inch, single, 18 foot, K-monel drilling col­ able is set each month for a proration welded, gathering line. The cost of lar. After plugging back, two collars, unit. This normal unit allowable is the structure was approximately $65,­ totaling about 30 feet, were run and then adjusted for depth and gas-oil 000. the source of the difficulty appears to ratio in setting the final daily allow­ Directional drilling was deemed to have been eliminated. able. When more than one proration be the most satisfactory method of To date, the directional drilling has unit is incorporated in a drilling unit reaching the underwater area and on been limited to locations within 2000 the allowable for the well on that drill­ 24 June 1954, Amerada Petroleum feet of the drilling site. In this distance ing unit is increased proportionately. Corporation spudded its J. G. Viall drift angles are kept at less than 25°. In setting spacing patterns for the Tract 1 No. 1 on the north bank of To reach more distant locations, much development of these fields, the In­ the reservoir. The well was deviated lower angles would be necessary. dustrial Commission has followed the 1893 feet to the southeast and was Paraffin in the production becomes principle of setting wide spacing for completed in 63 days at a cost of a serious problem when withdrawal initial development, in order to es­ about $215,000. The drilling pro­ rates are curtailed. In order to reduce tablish more quickly the limits of the ceeded without incident and the well maintenance costs, the operators are pool and obtain data on the reservoir. was completed in the prescribed loca­ allowed to produce their monthly al­ A final proper spacing is determined tion. Although directional drilling is lowable in as little as 5 days. The rule when sufficient data has accumulated not a new technique in the oil indus­ limits production rates to 600 percent to form a basis for a sound determina­ try, this was the first attempt to carry of the daily allowable, but the total tion. out such an operation in an area of allowahle for any month shall not be By tying the proration to tracts of well indurated rocks. exceeded. land rather than wells, and thus in­ On July 7, 1955, a second direc­ Proration to market demand is in creasing the allowable for wide spac­ tional well was spudded on the south effect by virtue of a statute enacted ing, the effect of spacing changes on bluff. It soon became apparent that by the 1953 legislature. The market the' income of land owners and royalty 1955 ~ <> MAY JUNE JULY AUG. -s-n.-., OC1. 2 I II Zl , I ZI I, II I C" ...... '" ! .,h. @) i '---.... D" 3Z00 "-- 8000 III ~~ - IYEF SON No. :3 rio Z~ Z 1>v-r 0 ,,; , , .J , .... t= Q ffiv. .J'" , : - ~l(- <.> > I~:! , , :::> W 3100 ~OOO 0 , 0 '":::> >-" II: '" "'","'" if'-h! :r-- ~ Q. W oJ '"II: Of'FS T WEl S PRO OCING 0 Q. ) lj 3000 I II' t 0 BEAVER LODGE PRESSURE INTERFERENCE

FIGURE 9--Results of interference test in Beoyer Lodge-Madison Pool. Note how form of the production curve is reflected in the pressure curve. owners is nil. Under such conditions, Amerada Petroleum Corporation con­ Company refinery at Williston and the decision on spacing can be based ducted extensive tests in the Beaver the amount used by the operators in on technical evidence. Lodge-Madison and Tioga-Madison drilling and lease operations. For De­ In the hearings held this year to pools. For the purpose of these tests, cember, 1955, this market totaled 36,­ determine the proper spacing for the nine selected wells were shut in on the 300 barrels per day and this approxi­ Beaver Lodge-Madison, Tioga-Madi­ first of June and pressures were ob­ mates the MER for present fields. (A son, Homund-Madison, and Charlson­ served until mid-October. During the small amount of this crude goes to the Madison pools, evidence was offered last week of July, offset wells to four Queen City refinery) . to show that the pay interval, in these of these test wells, two in each pool, The oil is purchased by Stanolind pools, is reasonably uniform; that were placed on production and two Oil Purchasing Company at a posted there is communication between wells months allowable was taken over a field prire of $2.90 per barrel. The in the pools; and that wells, in these two week period. These offset wells oil is transported from Tioga to Man­ pools, are draining areas as great as were shut in about 40 days prior to dan by Service Pipe Line Company 1000 acres. the production test. The drop in pres­ through its crude oil line. Service Pipe Four principle forms of evidence sure, at the observation well, was re­ Line Company also maintains the have been introduced: corded, and charted, and the result­ gathering lines in the fields. • Electric Jogs have been used to ant graphs showed clearly the com­ A small refinery was built at Willis­ trace the pay interval from well to munication between the test wells and ton in 1954 but was later sold to the well and demonstrate its uniform their offsetting wells, dr.illed on the Westland Oil Company. Operation character. 80-acre pattern. The test was repeated was resumed in November, 1955. The again during the last week of Sep­ rated capacity of the refinery was 1500 • Graphs have been introduced to tember and the first week of October barrels per day. show that wells drilled in recent and the same results noted. (See Fig­ Signal Oil & Gas Company com­ months have recorded initial reservoir ure 9). pleted its Tioga gasoline plant in Oc­ pressures close to the prevailing pres­ The remaining five observation weIls, tober, 1954. This is a very modern sure, for that portion of the field, as two in Tioga and three in Beaver plant and was designed particularly shown by regular measurements in Lodge remained shut-in during the for the climatic conditions in the area. adjacent, earlier wells. entire four-month test period. The No water cooling was used and the • Mathematical calculations have pressures recorded on these wells in­ cooling system is equipped 'with heat­ been made on the basis of production dicated a regular decline although the ers for winter use. All water used in data to show the pressure distribution wells were not producing, showing the plant is confined to enclosed areas. at various distances from wells. The that the reservoir was reacting to In addition to the usual products, calculation involves a modified form withdrawals from wells as much as this plant produces over 20 tons of of the Darcy Law equation and the J980 feet away. The witness at the elemental sulfur per day. The opera­ resulting pressures are plotted against October hearing of the State Indus­ tion of this plant has practically elimi­ drainage radius. From these graphs, trial Commission who introduced the nated the flaring of gas in the fields. it can be shown that we]]s draining an results of the tests stated that the oil Residue gas equalling about 65 per­ area of low permeability cause greater saturation of the reservoir was being cent of the wet gas intake will be pressure drops, and therefore fluid reduced a the rate of one-fourth of 1 taken by Montana-Dakota Utilities movement toward them, than wells percent per 100 psi. for their Tioga-Minot pipe line. This completed in areas of greater perme­ The market for crude oil produced line is also connected to their other ability. The slope of the pressure dis­ from the Nesson anticline is, at this distribu tion system at Williston in tribution curve at any point indicates time, limited to the amount that can order that excess gas from the Tioga the direction, and rate, of fluid flux be processed by the Standard Oil plant, during the off-peak season may at that point. Company of Indiana refinery at Man­ be sent to und{~rground storage in • During the summer of 1955, the dan, N. D., and the Westland Oil eastern Montana. -The End