• Abstract and Figures
• Public Full-text

t STATE Ift'f'O'Sj GEOLOGICAL SURVEY 3 3051 00003 5240 Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/undiscoveredoilr106leig STATE OF ILLINOIS DWIGHT H. GREEN, Governor DEPARTMENT OF REGISTRATION AND EDUCATION FRANK G. THOMPSON, Director DIVISION OF THE STATE GEOLOGICAL SURVEY \l. \L LEIGHTON, Chief CIRCULAR—No. 106 UNDISCOVERED OIL RESERVES IN ILLINOIS By M. M. LEIGHTON Reprinted from The Oil Weekly, March 13, 1944 LOWER ORDOVICIAN AND CAMBRIAN OIL POSSIBILITIES IN ILLINOIS By STEWART FOLK Reprinted from The Oil Weekly, March 20, 1944 PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS 1944 Undiscovered Oil Heserves In Illinois Chances for finding substantial amounts of new oil by no means exhausted, especially in stratigraphic type traps By M. M. LEIGHTON I LLINOIS has had two great periods good geological reason to believe that of oil development, one beginning in oil accumulations in stratigraphic traps 1905, the other in 1937. Of the total of exist in Illinois. The discovery of oil 1,022,000,000 barrels produced, 566,000,- pools of this type will depend upon 000 barrels, or half, came from fields geologic studies combined with large- discovered since 1936. scale systematic drilling programs. All but a fraction of one percent of Very probably more oil remains to this latter quantity came from fields be discovered in additional producing located in the area of "best possibili- formations, both above and below those ties," as recommended by the Illinois now productive. There have been sev- State Geological Survey in a map classi- eral instances where pay zones have fying oil and gas possibilities in Illinois been passed up and later brought in. which was prepared and exhibited in Also there are many pools producing 1930. This classification was based on a in the McClosky or shallower forma- review by Dr. A. H. Bell of the many tions in which no tests have been drilled well logs and other geologic data which below the Mississippian strata. the survey had accumulated over a In January, 1942, under a special ap- period of 25 years. The discovery of propriation for work connected with oil in the central part of the Michigan the war effort, the Illinois State Geologi- Basin in 1928 led to recognition of the cal Survey undertook studies of Penn- oil possibilities of the Illinois Basin, sylvanian strata encountered in drilling and accordingly the deep basin area oil wells, for the dual purpose of ob- was included with the area of "best taining information on the oil and coal possibilities" in the 1930 classification resources of the Pennsylvanian system. map. The old fields of Illinois produced some The same organization that prepared hundreds of millions of barrels of oil the classification map has been studying from Pennsylvanian sandstones, but the and aiding in the oil developments and amount so far produced from Pennsyl- has recently taken stock of the Illinois vanian strata in the new fields has been situation. It is convinced that the comparatively small, in spite of the fact chances for finding substantial amounts that nearly all the wells were drilled of new oil are by no means exhausted. completely through the Pennsylvanian Although no major pools have been system. For several years following the discovered for several years, many small new discoveries in 1937 most wells were pools have been found and continue to drilled rapidly through the Pennsyl- be found every month. In the past, vanian without saving samples or ob- major attention has been given to the taining an adequate log of the forma- finding of structural traps. When the tions drilled, and it is probable that reflection seismograph method began pay zones were sometimes passed up. to be used, it was natural that the Electric logs have proved to be of con- largest structures should be prospected siderable help in stratigraphic studies first. That is why large pools like Clay but alone they are inadequate to detect City, Salem, and Louden were brought oil zones or to determine thicknesses in early during the play. It may be that of coal beds not previously known. To no large pools of the structural-trap remedy this situation the survey has type remain to be discovered. However, obtained a portable laboratory which some of the world's largest oil accumu- makes it possible for staff geologists to lations, such as East Texas, are of the sit on key wells during the drilling of stratigraphic type, and these are not the Pennsylvanian strata in order to discoverable by the reflection seismo- make detailed drilling-time logs, to graph method now in use. There is collect and examine samples taken at - e> o frequent intervals and then to correlate obtained from older Ordovician and in the laboratory all the information Cambrian strata in the Mid-Continent from a well, including: the electric log. area raises the question as to the oil Up to date some 180 wells have been possibilities of rocks of the same age in logged in this manner, and the results Illinois. are being studied for the benefit of both In view of the present need for oil the oil and coal industries. and especially for supplies geograph- The new data from the key wells are ically near areas of large consumption, being assembled in structure maps and there is now a strong incentive to ex- cross-sections. It is planned that sub- plore these deeper strata in Illinois. surface studies of pre - Pennsylvanian Detailed studies of reservoir condi- strata will be made in the areas of the tions and production conditions in in- new Pennsylvanian structure maps. dividual pools are in progress. These These will be based on sample studies, have a two-fold use, first to help solve electric logs, and drilling-time logs production problems, especially in con- where available. The relation of pre- nection with secondary recovery by re- Pennsylvanian to Pennsylvanian struc- pressuring or water-flooding, and second ture will be given special atention. to aid in the interpretation of regional geology. This work involves the collec- Deeper Possibilities tion and testing of cores, the collection Because the oldest formation that has and analysis of oil, gas, and brine yielded commercial production of oil in samples, the measurement of reservoir Illinois is the Kimmswick ("Trenton") pressures, and the measurement of the limestone of Ordovician age it has been rates of withdrawal of the reservoir customary in much of the past test- fluids. drilling in Illinois to stop with the first The planning and execution of a porous zone in the "Trenton." A few program to explore for oil in strati- test wells have reached the St. Peter graphic traps, in the deeper formations, sandstone. There remains, however, a and in undeveloped shallow pay zones sedimentary section estimated to be should make use of all available scien- about 4000 feet thick below the St. tific data, both geological and geophysi- Peter which has not been tested in the cal. The Illinois State Geological Survey Illinois Basin. The lithologic character with its staff of technical experts, its and the structure of the pre-St. Peter laboratories, and its extensive files of strata in the basin is therefore unknown. data, is contributing its resources in The fact that large oil production is research to such a program. Lower Ordovician and Cambrian Oil Possibilities in Illinois Production of large volumes from these formations in other states suggest commercial possibilities in southern two-thirds of state, where they constitute almost unexplored geological "layer" By STEWART FOLK B1 ELOW the St. Peter formation in Cambrian age. Equivalent strata in Illinois are many hundreds of feet of Southwestern Illinois are designated by Lower Ordovician and Cambrian sedi- names used in the Ozark region (see mentary rocks—dolomites, shales, and Figure 2). Oil shows have been re- sandstones—of marine origin. The fold- ported in beds of Prairie du Chien and ing and partial erosion of these older Trempealeau age in tests drilled in strata before the St. Peter sands were West-Central and Southwestern Illinois deposited produced the most marked (see Table 1). No oil shows have been unconformity in the Lower Paleozoic reported in them in the Illinois Basin, succession of Illinois and adjoining but only four tests in the basin have states (see Figure 1). Some of the sub- been drilled into pre-St. Peter strata, surface dolomites and sandstones are and of these none has gone deep enough porous and permeable. Traces of oil to test even all of the Prairie du Chien. have been reported in them in Illinois, The Cambrian formations below the and oil is produced from equivalent Trempealeau are the Franconia, Gales- strata in Texas (Ellenburger limestone), ville, Eau Claire, and Mt. Simon, in Oklahoma and Kansas (Arbuckle or descending order. They have been cor- "Siliceous" lime and the Reagan or related with the Wilberns, Cap Moun- Lamotte or "Basal" sand), and in Ten- tain, and Hickory formations of Texas, nessee (the Knox dolomite). Such con- with the basal portion of the Arbuckle ditions suggest that commercially valu- and the Honey Creek, Cap Mountain, able quantities of oil may occur in the and Reagan formations of Oklahoma, Lower Ordovician and Cambrian for- and the Doe Run, Derby, Davis, Bon- mations in the southern two thirds of neterre, and Lamotte formations of Mis- Illinois, where they constitute an al- souri. They are not known to have been most unexplored geological "layer." penetrated in Southern Illinois, but a Only a few tests have been drilled to well in St. Louis, Missouri, was drilled them and none has been drilled through through them and into the pre-Cam- them in this area.

Load more

  20

Copy Link