& 
 
 14GS . C3UM SuJU)tU 
 
 STATE OF ILLINOIS 
 
 ADLAI E. STEVENSON, Governor 
 
 DEPARTMENT OF REGISTRATION AND EDUCATION 
 
 NOBLE J. PUFFER, Director 
 
 DIVISION OF THE 
 
 STATE GEOLOGICAL SURVEY 
 
 M. M. LEIGHTON, Chief 
 URBANA 
 
 CIRCULAR NO. 150 
 
 PROSPECTS FOR OIL DISCOVERIES IN ILLINOIS BEYOND 
 PROVEN AREAS AND FROM DEEPER HORIZONS 
 
 By 
 ALFRED H. BELL and M. M. LEIGHTON 
 
 Preprint of paper presented at the 
 Spring Meeting of the Eastern District, Division of Production, 
 American Petroleum Institute, Pittsburgh, Pa., April 29, 1949 
 
 ^ ',°<c> 
 
 PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS 
 
 URBANA, ILLINOIS 
 1949 
 
■ ".: I ' '!<".!< l:\ -.IIIIVI ,' 
 
 3 3051 00004 6163 
 
Paper 82o-20-G (1) 
 
 PROSPECTS FOR OIL DISCOVERIES IN ILLINOIS BEYOND 
 PROVEN AREAS AND FROM DEEPER HORIZONS 
 
 Alfred H. Bell 1 
 M. M. Leighton 2 
 
 Introduction 
 
 In this discussion of prospects for oil discoveries beyond proven 
 areas we have reference mainly to new pools that are five miles or more f rom l 
 previous productive areas. Therefore it omits a large area in the Illinois 
 basin where oil pools are already closely spaced, except for considering the 
 possibility of deeper production. 
 
 Based on developments in recent years, it is believed that the best 
 possibilities for important new discoveries in Illinois are as follows: 
 
 (1) Silurian coral reef production, like that in the Marine pool in 
 Madison County, in a belt extending northeastward from Marine to the LaSalle 
 anticlinal belt in Champaign and Douglas counties. 
 
 (2) Rosiclare sandstone production on favorable structures in the 
 general region around the newly discovered Assumption and Assumption North 
 pools, Christian County. This includes Christian, Shelby, and parts of Moul- 
 trie, Macon, Sangamon, and Montgomery counties. 
 
 (3) Devonian limestone production on favorable structures in the north- 
 ern part of the Illinois basin (encouraged by the recent discovery of Devonian 
 production in Assumption and Assumption North pools, Christian County, Illinois 
 and the Wilfred pool, Sullivan County, and Springhill pool, Vigo County, in 
 Indiana) „ 
 
 (4) Fault zone production, like that in the Slaughters pool, Kentucky, 
 in an east-west belt along the Cottage Grove Shawneet own-Rough Creek fault 
 system across parts of Gallatin, Saline, Williamson and Jackson counties. 
 
 (5) Strati graphic traps on the west flank of the LaSalle anticlinal 
 belt in Coles, Cumberland, Jasper, Crawford, and Lawrence counties. 
 
 (6) Pre-St. Peter formations in the basin. These are almost wholly 
 untested and their possibilities are unknown. They will be more expensive to 
 test but might contain large oil accumulations. 
 
 Historical 
 
 Illinois has had two noteworthy periods of oil development, the first, 
 beginning in I905, resulted in a production peak of 33>^86,000 barrels in the 
 year 1908. The second, beginning in 1937* resulted in a production peak of 
 
 (1) Geologist and Head, Oil and Gas Division, 
 Illinois State Geol. Survey, Urbana, 111. 
 
 (2) Chief, Illinois State Geol. Survey 
 Urbana, Illinois 
 
Page 2 
 
 Paper 826-20-G (l) 
 
 147,647*000 barrels in 1940 (see fig. 1). Since 1940* annual production has 
 declined to 64,639,000 barrels in 194^ ov approximately 45 percent of the 
 1940 rate. The present production rate may be maintained or raised by two 
 means: (l) secondary recovery, and (2) new discoveries. It is with the second 
 of these that this paper is concerned. 
 
 Except for methane gas produced from the Pleistocene glacial deposits, 
 Illinois oil and gas comes from Paleozoic rocks. Of the six Paleozoic sys- 
 tems present in the area, one - the Mississippian - has produced about three 
 fourths of the total oil. The Pennsylvanian system has produced about one- 
 fifth of the total, and nearly all of this was from the old Southeastern 
 Illinois field, mainly in Clark, Crawford, and Lawrence counties. The De- 
 vonian system has produced about five percent of the total, the Silurian 3/l0 
 percent and the Orodvician 6/l0 percent. Up to 1949> tiie Cambrian has pro- 
 duced no oil in Illinois. 
 
 A geologic column for the southern Illinois oil producing region is 
 shown in figure 2, on which oil producing formations are shown by symbols. 
 
 A simplified geologic map of the Eastern Interior basin and surround- 
 ing region is shown in figure 3 which also shows the location of the Marine 
 pool and major structural features. 
 
 Marine pool Madison County 
 and its significance 
 
 The Marine pool, Madison County, Illinois, located on the west side of 
 the basin about 25 miles northeast of St. Louis, was discovered in July 1943 
 following seismograph and gravity surveys. The oil reservoir is a Silurian 
 coral reef and is the first one of its kind to produce oil in Illinois. 
 
 Figure 4 is a diagrammatic cross-section of the Marine pool reef. '3) 
 
 Up to the end of 194^> "the Marine pool had produced 4,683,000 barrels 
 of oil. During December 194$ it produced at the average daily rate of 2899 
 barrels from 142 wells, an average of yQ barrels per well per day. Published 
 reports describe the geology and development of the Marine pool.* 3 > '4' 
 
 In the earlier report (1946), Lowenstam and DuBois stated, "The dis- 
 covery of a Niagaran reef at Marine, far removed from the reef belt which 
 fringes the Michigan basin and the reef cluster in northwestern Illinois and 
 Iowa, appears to be significant. The size of the Marine reef, at least as 
 large as that of any other known Niagaran reef, suggests that the Niagaran 
 deposits adjacent to the Ozark upland are potentially sites of other reefs, 
 and as such have additional oil potentialities. It is not known at present 
 whether the Marine reef is isolated or is part of a reef belt. It seems at 
 least possible that it may be connected by a series of reefs to the known 
 area of reef development in the north." 
 
 (3) Lowenstam, H. A., and DuBois, E. P., Marine Pool, Madison County; Illinois 
 Geol. Survey Rept. Inv, 114, fig. 10, p. 23, 1946. 
 
 (4) Lowenstam, H. A., Marine Pool, Madison County, Illinois, Silurian Reef 
 Producer: Illinois Geol. Survey Rept, Inv. 131, 1948. 
 
Page 3 
 
 Paper 826-20-G (1) 
 
 In the report published in 194^ Lowenstam said, "Niagaran reef rock 
 has been cored near Arthur, Moultrie County, Illinois, and near Covington, 
 Fountain County, Indiana. These previously unknown reef occurrences suggest 
 a reef belt lying south of the Michigan basin belt or linking that belt to 
 the Ozark border." 
 
 Since the publication of Report of Investigations 131, in 1948, a new 
 oil producing Silurian coral reef has been discovered in the McKinley pool 
 in Washington County, Illinois, which formerly produced only from the Benoist 
 sandstone in the Chester series. There is also evidence that the Sandoval 
 oil pool, Marion County, Illinois, overlies a Silurian coral reef which was 
 responsible for the oil accumulation in the Devonian limestone and perhaps 
 also in the Benoist sand through upward migration. 
 
 The area considered to have the best possibilities for oil in Niagaran 
 reefs is shown in figure 5. 
 
 A regional study of the occurrence of Silurian coral reefs with special 
 reference to oil prospecting has been made by Dr. Lowenstam and a report is 
 being prepared for early publication. 
 
 Assumption and Assumption North pools, 
 Christian County, and their significance 
 
 As one goes north from the deep basin area, the oil producing sands 
 become fewer and thinner. Thus in the Mattoon pool in Coles County there 
 are good pay sands in the Cypress (15 feet average thickness) and Rosiclare 
 (10 feet average thickness), but 10 miles north in the Cooks Mills pool the 
 sands have become thin and tight, and although some oil is present there is 
 only small production. The discovery of excellent Rosiclare sandstone pro- 
 duction in the Assumption North pool about 35 miles west of Cooks Mills makes 
 the prospects for additional Rosiclare production on favorable structures in 
 the general region seem much better than it did. There is also some production 
 from the Bethel sandstone and Devonian limestone in the Assumption area. 
 
 The area considered to have good prospects for Rosiclare sandstone 
 production on favorable structures is outlined in figure 6. 
 
 The discovery of oil production from Devonian limestone in the Assump- 
 tion and Assumption North pools, Christian County, is a northward extension 
 of the region in which Devonian limestone oil has been produced commercially 
 in Illinois. Some oil was found in about G or 8 wells that were drilled be- 
 tween 1922 and I924 just north of Decatur in Macon County, but it was not 
 commercial. The recent discoveries suggest the possibility of other oil pools 
 in the Devonian limestone in the vicinity (western stippled area in figure r f). 
 
 Two oil discoveries in Devonian limestone in western Indiana in 194^ - 
 Springhill in Vigo County and Wilfred in Sullivan County - have revived in- 
 terest in Devonian possibilities in an area extending into Illinois (eastern 
 stippled area in figure 7). 
 
Digitized by the Internet Archive 
 
 in 2012 with funding from 
 
 University of Illinois Urbana-Champaign 
 
 http://archive.org/details/prospectsforoild150bell 
 
Page 4 
 
 Paper 82o-20-G (l) 
 
 Fault zone possibilities along 
 Shawneetown and Cottage Grove faulted belt 
 
 A major fault zone called the Shawnee town-Rough Creek fault zone ex- 
 tends about l^O miles in an approximate east-west direction in the southern 
 part of the Eastern Interior basin in southern Illinois and Kentucky. West- 
 ward from the end of the Shawneetown fault in Illinois, tht Cottage Grove 
 fault and related faults constitute a fault zone which approximately lines 
 up with the Shawnee town- Rough Creek fault zone and extends west as far as 
 Duquoin. The northern edge of the highly faulted zone has in the past been 
 considered the approximate southern boundary of the area of best oil possi- 
 bilities in Illinois, and up to date all of the oil pools in Illinois are 
 north of it. 
 
 The discovery in 1%7 of the Slaughters oil pool in Webster County, 
 Kentucky, located just south of the Shawnee town- Rough Creek fault zone and 
 about 30 miles from the Illinois-Kentucky boundary, suggests that oil pools 
 similarly located with respect to structure should be sought in Illinois. 
 The territory considered to have possibilities for this type of oil occur- 
 rence is shown in figure 8. 
 
 West flank of LaSalle anticlinal belt 
 
 On the steeply dipping west flank of the LaSalle anticlinal belt in a 
 strip about five miles wide and 100 miles long (see figure 9)> there are 
 possibilities for oil production from porous lenses of sandstone or limestone 
 wedging out eastward against the anticline. Some small areas of production 
 from Ste. Genevieve limestone in Lawrence County, for example, the Ruark and 
 Sumner pools are of this type. Some exploratory drilling has been done but 
 much more will be necessary to determine whether or not such stratigraphic 
 traps are present. 
 
 Oil possibilities of strata 
 below St. Peter sandstone 
 
 The sedimentary strata from the St. Peter sandstone down to the pre- 
 Cambrian, which are estimated to have a maximum thickness of 4- 000 to 5 000 
 feet, have not yet been tested in the greater part of the Illinois basin. A 
 line on the map in figure 10 divides Illinois into two parts ; in the northern 
 part pre-St. Peter oil prospects are considered improbable, the southern part 
 they are considered possible. In northeastern Illinois hundreds of wells - 
 mostly water wells but also some oil tests - have been drilled into the Lower 
 Ordovician and Cambrian strata without finding oil except for rare oil shows 
 reported by drillers. Many porous strata in this area contain fresh or slight- 
 ly brackish waters. Although fewer wells have been drilled in northwestern 
 and west central Illinois the same results have been obtained. 
 
 In the southern area only about 25 wells have been drilled as deep as 
 the St. Peter sandstone, and only l6 go below the St. Peter. The fact that 
 oil is produced from strata of equivalent age both to the west (Arbuckle 
 limestone production in Oklahoma) and to the east (Knox dolomite production 
 in Kentucky) suggests that the pre-St. Peter strata have oil possibilities in 
 Illinois. However the greater expense of drilling to test the whole of the 
 
Page 5 
 
 Paper 82o-20-G (1) 
 
 sedimentary series in the Illinois basin, resulting from depths of as much as 
 if oSo or I 2 ,000 feet, has deterred such prospecting up to date, especially 
 while new discoveries 'continue to be made at depths of less than 4 000 feet. 
 
 List of Illustrations 
 
 Fig. 1. Bar chart of annual oil production in Illinois 1936-I948 incl. 
 
 FiS 2. Generalized geologic column for southern Illinois oil region 
 showing principal oil producing formations. 
 
 Fig. 3. Simplified geologic map of Eastern Interior basin and surround- 
 ing region (Illinois State Geol. Survey, R. I. I3I, fl S- x » 
 P. 154). 
 
 Fig A. Diagrammatic cross-section of Marine pool reef (Illinois State 
 Geol. Survey, R. I. 114. fi e- 10 » *• 2 3 ] '• 
 
 Fig. 5. Area of best possibilities for oil in Niagaran reefs. 
 
 Fig. 6. Prospective area for Rosiclare sandstone production on fav-' 
 orable structure. 
 
 Fig 7 Prospective areas for Devonian limestone production on fav- 
 orable structures as suggested by recent discoveries. 
 
 Fig 8 Area of possible fault-zone pools along Cottage Grove and 
 ' Shawneetown fault zones, based on recent discovery of 
 
 Slaughters pool, Webster County, Kentucky, in Rough Creek 
 fault zone. 
 
 Fig. 3. Area of possible stratigraphic-trap pools on west flank of 
 LaSalle anticlinal belt. 
 
 Fig. 10. Area having oil possibilities in OrdovIciMf J^f^f ' 
 Peter and Cambrian system The northern part of the State 
 has many wells (not shown) that penetrate pre-St Peter strata, 
 but all known pre-St. Peter wells that are in and near the 
 possible oil area are included. 
 
MILLIONS OF 
 BBLS. 
 160,— 
 
 ILLINOIS OIL PRODUCTION 
 1936-1948 
 
 in.. 
 
 1936 1938 1940 1942 1944 1946 1948 
 
 FIGURE-I 
 
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 FIGURE-3 
 
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ILLINOIS STATE GEOLOGICAL SURVEY 
 
 FIGURE-5 
 
ILLINOIS STATE GEOLOGICAL SURVEY 
 
 FIGURE-6 
 
SPRINGHILL 
 
 lO°° CONTOUR ON TOP 
 
 OF DEVONIAN-SILURIAN 
 
 LIMESTONE 
 
 DATUM SEA LEVEL 
 
 20 40 60 MILES 
 
 ILLINOIS STATE GEOLOGICAL SURVEY 
 
 FIGURE — 7 
 
SLAUGHTERS 
 POOL 
 
 20 40 60 MILES 
 
 ILLINOIS STATE GEOLOGICAL SURVEY 
 
 FIGURE — 8 
 
ILLINOIS STATE GEOLOGICAL SURVEY 
 
 FIGURE-9 
 
KEY 
 
 WELLS TO LOWER ORDOVICIAN 
 AND CAMBRIAN 
 
 ®TO PRE-CAMBRIAN 
 •BELOW ST. PETER 
 
 LOWEST FORMATIONS TESTED 
 
 ORDOVICIAN SYSTEM 
 
 S SHAKOPEE 
 
 N NEW RICHMOND 
 
 ONEOTA 
 
 CAMBRIAN SYSTEM 
 
 T TREMPEALEAU 
 
 F FRANCONIA 
 
 E EAU CLAIRE 
 
 M MT SIMON 
 
 20 40 60 MILES 
 
 ILLINOIS STATE GEOLOGICAL SURVEY 
 
 FIGURE-IO