s IP Press Bulletin Series Kor the Oil and Gas Industry STATE OF ILLINOIS DWIGHT H. GREEN, Governor DEPARTMENT OF REGISTRATION AND EDUCATION FRANK G. THOMPSON, Director DIVISION OF THE STATE GEOLOGICAL SURVEY M. M. LEIGHTON, Chief URBANA No. 39 ILLINOIS PETROLEUM September 13, 1941 "TRENTON" PRODUCTION IN ILLINOIS By George V. Cohee "Trenton" Producing Areas Soon after the discovery of oil in the Devonian limestone in some of the new pools in Illinois during 1940, interest was centered on the possibilities of the "Tren- ton" limestone. This formation has pro- duced oil for a number of years in the Westfield pool, Clark County, in south- eastern Illinois, and in the Dupo and Waterloo pools, St. Clair and Monroe counties, in southwestern Illinois. The "Trenton" was successfully tested in the Centralia pool in two wells during 1940. Early in 1941 development of this forma- tion in the Salem pool was started. As of April 22, twenty-one "Trenton" wells have been completed in this pool. These wells were deepened from the Devonian limestone. The "Trenton" limestone has been tested in a number of small pools in the State and found to be unproductive fig. 1). Production from this formation in Illinois so far has been limited to struc- tures that have considerable closure. The principle "Trenton" producing area east of Mississippi River is the Lima- Indiana field which has produced oil and gas in considerable quantities from rocks of Ordovician age. Other than in Illinois small amounts of gas have been produced from the "Trenton" in the Cumberland saddle, southern Kentucky, and in Os- wego and Oneida counties, New York. 1 The Lima-Indiana district extends through an area of about 12,000 square miles, only a small part of which produced oil and gas. 2 In Indiana the "Trenton" has produced both oil and gas since 1886. The total area of crude oil production is 127,000 acres and that of natural gas 650,000 acres. Crude oil production in this area from the "Trenton" to the end of 1939 was 107,000,000 barrels, a recovery of 840 barrels per acre. Natural gas pro- duction to the end of 1939 was 800 billion cubic feet. 3 The producing zone was large- ly restricted to the upper 50 feet of the "Trenton" limestone. A. F. Melcher held that the "Trenton" in this area had suf- ficient primary porosity to permit move- ment of fluids. He did not believe that the cavities were sufficiently intercon- nected to permit the movement of fluids for any great distances. 4 Stratigraphic Position Trenton limestone was first defined by L. Vanuxem in 1838 as the light gray or sparry limestone which forms the upper mass of Trenton Falls, Oneida County, New York. It is underlain by dark or black, almost compact limestone and overlain by the black Ltica shale. The thickness of Trenton as first described was from 10 to 125 feet. In 1842 Vanuxem de- fined Trenton limestone as to 300 feet thick, practically repeated his 1838 de- scription of its lithology, and called the 1 L?y, Henry A., Lima-Indiana District, Indiana and Ohio, in The Geology of Natural Gas: Am. Assdc. Petroleum Geologists, p. 852. 1935. 2 Idem. 3 Esarey, R. E. and Fix. G. F., Oil and gas developments in Indiana during 1939: Trans. A.I.M.E. vol. 136, p. 282, 1940. 1 Ley, Henry A., op. cit. [1] TRENTON" PRODUCTION IN ILLINOIS LEGEND 10 OIL AND GAS FIELDS ABANDONED FIELDS # "TRENTON" LIMESTONE PRODUCTION T "TRENTON" LIMESTONE TESTED SP ST. PETER SANDSTONE TESTED POOL AND COUNTY 1. WESTFIELD ; CLARK 2. MARTINSVILLE \ CLARK 3. SALEM ; MARION 4. CENTRALIA ; CLINTON, MARION 5. DUPO; ST. CLAIR 6. WATERLOO; MONROE 7. HERSCHER*; KANKAKEE * NOT COMMERCIAL PRODUCTION APRIL 15, 1941 Fig. 1. — Oil and gas fields in Illinois. Areas of "Trenton" production are shown in black, and fields in which "Trenton" or St. Peter strata were tested are indicated. Wildcat tests to "Trenton" or St. Peter are not shown. ILLINOIS STATE GEOLOGICAL SURVEY 3 3051 00005 0892 EARLY PRODUCTION i WATERLOO POOL 2 DUPO POOL 4 SALEM POOL 5 6 WESTFIELD MARTINSVILLE POOL POOL CENTRALlA POOL CLINTON, MONROE ST CLAIR MARION MARION CLARK CLARK DEPTH COUNTY DEPTH COUNTY DEPTH COUNTIES DEPTH COUNTY DEPTH COUNTY DEPTH COUNTY 260 l^~-1 45Fp?F^] 3807 tr _— J 4280 |~ — ^1 2015 I^F H 2412 trZr-5 KIMMSWICK LEGEND I PRODUCING ZONE • UPPERMOST LIMIT OF OIL SHOWS AND SATURATION [=D SHALE ^3 SHALE, SILTY r^l SILTSTONE P^ LIMESTONE E3 LIMESTONE, DOLOMITIC E53 DOLOMITE f£pl DOLOMITE, CHERTY APRIL 15,194 Fig. 2. — Columnar sections of upper Ordovician strata in pools producing from the "Trenton" limestone in Illinois. underlying formation Black River lime- stone in which he included the Lowville of present nomenclature. This is the present commonly accepted definition, although for many years most writers used Trenton limestone to include not only the Trenton proper but also all of the underlying Black River group, whereas some writers used Trenton group, also Trenton formation and Trenton limestone, to include the Trenton proper, all of the Black River group, and in some cases Chazy limestone also. 5 The name "Trenton" as used in Illinois includes all of the strata below the Ma- quoketa shale to the top of the Glenwood- St. Peter sandstone. Production to date has been found only in the Kimmswick limestone, the upper member of the Mo- hawkian series that also includes the Plat- tin formation. The Mohawkian series is correlated with Trenton and Black River strata of the New York section. 6 Early Production The first "Trenton" production in Illinois, although non-commercial, was in sec. 32, T. 30 N., R. 10 E., Kankakee County, at the south edge of Herscher, Illinois (fig. 1, no. 7). A number of wells were drilled to the "Trenton" in this area in 1900. Of these, nine were pumped for eight months and then abandoned. The largest well produced less than one barrel daily, some gas was produced with the oil. 7 The "Trenton" was reached at a depth of 140 feet. Available subsurface data are not enough to determine the de- tailed structural conditions in this area, although contours based on elevations of the top of bedrock suggest an anticlinal nose extending in a southwesterly direc- tion from the Kankakee arch. Several areas in northwestern Indiana along the Kankakee arch produced small amounts of oil from the "Trenton." 8 5 Lexicon of Geologic N'ames of the United States: U. S. Geol. Survey Bull. 896. pt. 2, p. 2179. 19J8. 6 Ekblaw. G. E., Personal communication. 7 Athey. L. F., Geology and mineral resources of the Herscher quadrangle: Illinois Gaol. Survey Bull. 55, pp. 109-110. 1928. 8 Logan. W. N., Handbook of Indiana Geology, pt. 5, chap. 10, 1922. "TRENTON" PRODUCTION IN ILLINOIS 100 Ul rr a. < £D50 25 I o I 2 3 4 5 6 7 8 9 10 M 12 13 14 15 16 17 18 19 20 21 YEARS Fig. 3. — Daily production at end of yearly intervals for a "Trenton" well in the Westfield pool, Clark County. Westfield Pool The first commercial production from the "Trenton" limestone in Illinois was in the Westfield pool, Clark County, near the north end of the southeastern Illinois fields (fig. 1, no. 1). The first well, drilled in 1910, was a small producer. The initial production of the well was 65 barrels and the production for the second 24 hours was 20 barrels. The depth of the produc- ing zone was from 2,395 to 2,445 feet. The well, which was abandoned ten years later, produced an estimated total of 10,000 barrels during that time. The Westfield pool is located on a dome on the axis of the LaSalle anticline. The principal producing formation is the Westfield limestone, correlated as the St. Louis-Salem limestones. The St. Louis limestone, which thins over the top of the dome, averages 60 feet in thickness on top. The "Trenton" closure, which amounts to at least 160 feet, conforms closely to that of the overlying Mississippian strata. 9 Production is limited structurally to the upper 50 feet at the top of the structure. Thirteen wells in the pool have pro- duced an estimated total of 171,000 bar- rels of oil from the "Trenton." Two wells are still producing with an average daily production of approximately 3 barrels. 9 Mylius, L. A., Oil and gas in east-central Illinois: Illinois Geol. Survey Bull. 54. pi. 26. 1927. The wells are usually pumped only once a week. One well has produced for 20 years, the other for 22 years. The average life of the "Trenton" wells at Westfield has been 11 years. The average produc- tion per well per day throughout the life of each well was approximately 4 barrels. The recovery of crude oil from the "Tren- ton" limestone at Westfield is approxi- mately 800 barrels per acre. Production is obtained from the Kimm- swick formation in the Westfield pool at various depths throughout a zone aver- aging 90 feet in thickness (fig. 2). The zone consists of coarse dolomitic lime- stone, fossiliferous, with clear calcite crys- tals. The average depth to the top of the "Trenton" is 2250 feet and to the top of the "pay" 2340 feet. The "pay" is usually encountered from 90 to 100 feet below the top of the limestone. Where the formation contained oil in commercial quantity the wells had little or no water. The rate of the production suggests low porosity and permeability of the producing zone. The initial production averaged about 100 barrels per well and declined an average of 72 per cent the second 24 hours. Within 2 or 3 months the daily average produc- tion per well was 10 or 12 barrels. One well completed in the field with an initial production of 125 barrels was producing 6 barrels daily 14 years later and after 21 years was producing 3 barrels daily (fig. 3). MARTINSVILLE AND WATERLOO POOLS Martinsville Pool Four wells have tested the "Trenton" in the Martinsville pool, Clark County (No. 2, fig. 1), and two of the wells ob- tained production. The first well, Trenton Rock Oil Co.— -McFarland No. 1 in the SE. H SE. % NW. M sec. 19, T. 10 N., R. 13 W., was drilled in 1921 on the side of the Martinsville dome, according to contours on top of the Devonian lime- stone, 10 and had an initial production of 125 barrels which declined to 10 barrels within a short time. The well was pumped for a number of months and then stood idle approximately three years before be- ing abandoned; during this time it flowed at intervals. The total production of the well was approximately 6,000 barrels. 11 During 1940 the Strickler-Jackson No. 1, N\Y. M NE. % SW. M sec. 19, T. 10 N., R. 13 W., was drilled a short distance from the McFarland well and tested the "Trenton." The initial production was 4 barrels of oil and 15 barrels of water. The well was later plugged back to produce from the Carper sand encountered at a depth of from 1,302 to 1,364 feet. A study of the drill-cuttings from the well showed the Kimmswick to be at a depth of 2675 feet, and the top of the saturated zone was at 2729 feet (fig. 2). The well was drilled 104 feet below the top of the " pay" to a total depth of 2833 feet and was shot with nitroglycerine from 2772 to 2794 feet. The St. Peter sandstone was tested on top of the Martinsville dome in the Tren- ton Rock Oil and Gas Co. — Carper No. 13, NW. \i NE. M sec. 30, T. 10 N., R. 13 W. This well had a show of gas in the "Trenton" at a depth of from 2732 to 2742 feet, and a show of oil from 2800 to 2868 feet. The well was shot with 200 quarts of nitroglycerine, and it then pumped 29 barrels of oil and 10 barrels of water. It was later deepened to the St. Peter sandstone, and several shows of oil were reported in the strata penetrated above the sandstone. As this well was favorably located on structure, and in view of the results of the other tests, the 10 Moulton. G. F.. Prospecting near the Martinsville pool: Illinois Geol. Survey Illinois Petroleum No. 4, fig. 1, page 3, 1926. 11 Personal communication from Mr. Harry Werts. President, Trenton Rock Oil and Gas Company, Casey, Illinois. "Trenton" does not appear very promis- ing for further testing in this area. Waterloo Anticline The Waterloo anticline is a long narrow structure extending north of west from Waterloo, through Dupo, Illinois, to St. Louis, Missouri. Lower Mississippian strata are at the surface along the struc- ture. On this structure crude oil has been produced only from the "Trenton" in the Waterloo pool (fig. 1, No. 6) and the Dupo pool (fig. 1, No. 5). WATERLOO POOL In the fall of 1920 oil was encountered in the Kimmswick limestone in a well drilled for water by the Waterloo Con- densed Milk Company. Exploration and development along the anticline in the vicinity of Waterloo, as recommended by the State Geological Survey in two press bulletins, 12 resulted in the discovery of the Waterloo pool. The principal area of production is a long narrow strip extend- ing through sec. 2, T. 2 S., R. 10 W., and south into the NW. Y± sec. 11. Early in 1922, some 33 producing wells had been drilled in the pool. Wells located high on structure had initial productions from 75 to 125 barrels but soon declined to 25 or 50 barrels a day. 13 The last producing well in the field was abandoned in 1930. The new development in oil and gas in Illinois revived the interest in obtaining further shallow production in this area. In 1939 and 1940 new wells extended the productive area along the crest of the anticline and west of the old producing area. Initial production of the new wells ranged from 15 to 60 barrels of oil and from 1 to 500 barrels of salt water. The total productive area of the pool is 230 acres, and the total crude-oil production to the end of 1940 was 197,000 barrels. The recovery to the end of 1940 has been 857 barrels per acre. Contours representing the top of the Kimmswick limestone 14 in the Waterloo pool show more than 100 feet of closure 12 Culver, H. E.. Geology and oil and gas possibilities in the vicinity of Waterloo, Monroe County. Illinois: Illinois Geol. Survey Press Bulletin, 1920. Mylius. L. A.. Oil and gas in Monroe County, Illinois: Illinois Geol. Survey Press Bulletin, 1921. 13 Lamar, J. E., Notes on the Waterloo Anticline: Illinois Acad. Sci. Trans., vol. IS. p. 398-404, 1922. " Bell, Alfred H., The Dupo oil field: Illinois Geol. Survey Illinois Petroleum No. 17, fig. 2, pp. 10-11, 1929. "TRENTON" PRODUCTION IN ILLINOIS on the anticline. Production is limited to the uppermost part of the structure. The depth to the top of the Kimmswick limestone averages 410 feet, and the best saturated zone averages about 30 feet in thickness with shows of saturation throughout a thickness of 50 feet or more. Saturation is encountered near the top of the Kimmswick limestone which is over- lain by a white dense crystalline limestone averaging 12 feet in thickness in the pool. This limestone has been correlated with Fernvale limestone which crops out in southwestern Illinois. 15 A study of the samples of a recent well drilled in the pool showed 7 feet of a light gray to buff fine- to medium-grained fossiliferous lime- stone immediately underlying the Ma- quoketa formation. Because this limestone is lithologically similar to the upper part of the Kimmswick as correlated in nearby wells recently drilled, it is included in the Kimmswick for the purpose of this report. Early in the life of the pool, water was encountered in the lower part of the" pay" high on structure but at shallower depths lower on structure. The producing zone consists of buff to brown crystalline lime- stone, fine- to coarse-grained (fig. 2). The St. Peter sandstone was tested in the pool by the Remington-Kolmer No. 2, N W. y A NE. \i NW. M sec. 2, T. 2 S., R. 10 W.j which was drilled to a depth of 1802 feet. The well was plugged back to the "Trenton" from which production was obtained. DUPO POOL The Dupo pool, located on the northern extension of the Waterloo anticline, was discovered in 1928. During 1929, a total of 224 oil wells was completed in the field which was extended into the village of Dupo. Production from the town-lot wells declined rapidly because of their close spacing and many of the wells were soon abandoned. By the end of 1933 only 57 producing wells remained in the pool. Initial productions of the wells ranged from 50 to 350 barrels and the decline in production the second 24 hours ranged from 14 to 75 per cent, averaging 46 per cent for those wells for which production figures are available. One well which had an initial production of 200 barrels was producing 50 barrels daily one week later. Contours representing the top of the Kimmswick limestone 16 show at least 100 feet of closure in the pool, and production was limited almost entirely to the area of closure. Water encroached rapidly in the pay, and by 1934 it was found throughout the field. The amount of water produced with the oil increased so much that many wells were abandoned for this reason. The top of the producing zone is usually about 5 feet below the top of the Kimm- swick limestone (fig. 2) and extends throughout a zone averaging 50 feet in thickness. It is light brown to buff" lime- stone, coarsely granular, compact, fossi- liferous, and the drill cuttings show much clear calcite. Solution cavities and crev- ices have been encountered in the upper part of the producing zone in a few wells near the top of the structure. The initial production of these wells was larger than that of nearby wells. The total oil production for the pool to the end of 1940 was 1,275,000 barrels and the productive area was 670 acres. The recovery to the end of 1940 was 1900 barrels per acre. At the end of 1940 there were 64 producing wells in the pool. During the recent oil development in Illinois additional wells have been drilled in the pool. Initial production of these later wells ranged from 5 to 200 barrels of oil and from to 6,000 barrels of water. Centrifugal pumps were installed in some of the wells to handle large volumes of fluid which could not be produced with the customary pump-jack as lifting power. Such a pump was installed in one well drilled in a part of the pool where water had encroached in the pay causing near- by old wells to be abandoned. During 8 months operation of the centrifugal pump, the well produced approximately 47,000 barrels of oil and 903,000 barrels of water. The cost of the pumping equipment and power for operation of the pump during that period was approximately $11,000. The first day the well produced 6,000 barrels of water and no oil, the second day it produced 25 barrels of oil and 6,000 barrels of water, and with further opera- tion of the well there was an increase in oil and a decrease in water production. " Lamar, J. E., op. cit. '« Bell, A. H., op. cit. DUPO POOL The peak oil production of 400 barrels was obtained one month after the well was put in operation, at which time it still produced 5400 barrels of water with the oil. At the end of 8 months the well was producing 40 barrels of oil and 1800 barrels of water a day. It is believed that this method of hand- ling large fluid volumes may make it pos- sible to recover a considerable amount of oil in certain old pools in the State where water-encroachment has greatly reduced oil production. By removing large amounts of fluid from the reservoir, oil which has been trapped with the chan- neling and by-passing of water would be drawn to the well and recovered. The producing zone was cored by the Survey in four wells in the Dupo pool. The study of the cores showed the porosi- ty to vary from 2.6 to 19.0 per cent with an average of 14 per cent; permeability ranged from to 61 millidarcys with an average of 7.7 millidarcys; the average total fluid saturation of the pore space was 54.3 per cent. It is believed that where the "Trenton" is productive in Illinois the physical character of the pro- ducing zone is comparable to that in the Dupo pool. A study of one of the cores is as follows: 17 Ohio Oil Co.—M. Dyrqff well No. 27, SW. \i NW . )4 SE. H sec. 28, T. 'l N., R. 10 W., St. Clair County. Surface elevation 405.5 feet. Formation Thickness Ft. In. Beginning ot core Kimmswick limestone Limstone, light brownish- gray, very fine, some coarse areas, containing oil along stylolites and in more coarse-grained areas; sample 1 Limestone, light brownish- gray to gray, very fine to very coarse, crinoidal, oil in tubular areas in lowest 9 inches; samples 2-4. ... 2 Limestone, brownish - gray, coarsely crystalline, po- rous with tossil impressions, containing oil Limestone, grayish - brown, very fine to coarse, crys- talline, compact; samples 5 and 6 2 Depth Ft. In. 401 401 9 404 404 9 406 9 "Piersol, R. J.. Workman. L. E.. Watson. M. C. Porosity, total liquid saturation, and permeability of Illinois oil sands: Illinois Geol. Survey Rept. Inv. Xo. 67, pp. 48, 49. 51, 1940. Thickness Depth Ft. In. Ft. In. Limestone, grayish - brown, coarse, crystalline, some- what porous; samples 7 and 8 19 408 6 Limestone, brown, very coarse, crystalline, porous; samples 9 and 10 16 410 Limestone, grayish - brown, coarse, crystalline, com- pact; samples 11-13 3 6 413 6 Limestone, brown to grayish- brown, very coarse, more or less porous; samples 14- 18 4 6 418 Limestone, brown with dark brown bituminous specks, coarse, crystalline, com- pact 2 418 2 Limestone, speckled brown- ish-gray and gray, medium to coarse, crystalline, thin layer of phosphatic nodules at base; sample 19 10 419 Limestone, speckled light brownish -gray and gray, verv fine to coarse, crys- talline 4 419 4 Limestone, brown, coarse, crystalline, somewhat po- rous, containing oil; sam- ples 20-22 2 8 422 Limestone, light gray and brown speckled, coarse, crystalline, compact ex- except near base; samples 23-25 3 425 Limestone, light gray and brown speckled, very coarse, porous; samples 26-28 3 9 428 9 Limestone, brown, coarse, crystalline, more or less porous, containing oil; samples 29-40 12 3 441 Limestone, brownish - gray, coarse, crystalline, some- what porous; samples 41- 42 2 443 Limestone, grayish - brown, medium to coarse, fairly compact; sample 43 1 1 444 1 Limestone, buff with brown specks, very fine, cono- donts 1 444 2 Limestone, speckled light brownish-gray and brown, coarse, porous 5 444 7 Limestone, light brownish- gray, brown specks, very fine, compact, conodonts . 1 444 8 Limestone, light to medium brown, coarse, crystalline, porous; sample 44 8 445 4 Limestone, brown, fine to coarse, crystalline, com- pact, areas of clear crystal- line calcite filling former cavities, show of oil 8 446 "TRENTON" PRODUCTION IN ILLINOIS Porosity and Permeability of Kimmswick Lime Dyroff well No. 27 Sample Depth Porosity Permeability No. (ft.-in.) (per cent) (millidarcys) 1 401-0 5.0 0.30 2 402-0 1.9 0.00 3 403-0 10.0 0.00 4 404-0 13.0 60.9 5 405-0 6.7 4.4 6 406-0 2.6 0.00 7 407-0 13.0 12.9 8 408-0 14.6 16.8 9 409-0 13.5 9.5 10 410-0 10.4 3.4 11 411-0 7.8 0.80 12 412-0 9.6 1.8 13 413-0 9.8 7.7 14 414-0 14.2 12.3 15 415-0 14.7 11.1 16 416-0 11.9 6.2 17 417-0 17.0 11.5 18 418-0 7.6 0.90 19 419-0 4.3 0.00 20 420-0 8.3 0.40 21 421-0 10.1 3.3 22 422-0 6.1 0.00 23 423-0 9.5 4.9 24 424-0 4.4 0.00 25 425-0 9.8 4.9 26 426-0 7.3 1.0 27 427-0 6.3 0.0 28 428-0 14.0 1.8 29 430-0 15.3 10.9 30 431-0 16.6 9.0 31 432-0 15.9 12.1 32 433-0 16.0 17.9 33 434-0 16.3 19.4 34 435-0 10.5 1.4 35 436-0 16.5 13.9 36 437-0 15.0 13.9 37 348-0 15.9 21.5 38 439-0 16.6 24.5 39 440-0 11.1 3.3 40 441-0 11.4 1.1 41 442-0 5.8 0.40 42 443-0 12.5 9.9 43 444-0 8.5 1.6 44 445-0 8.1 1.7 Vertical and Horizontal Permeability of Kimmswick Lime, Dyroff Well No. 27 Centraua Pool In the Centralia pool, Clinton and Marion counties (fig. 1, No. 4), two wells are producing from the "Trenton" lime- stone. Both wells were drilled in 1940 near the center of the structure. The top of the Trenton was reached at a depth of 4018 feet in the Ames — Hicks No. 2 well located in the SW. M NE. M SE. M sec. 12, T. 1 N., R. 1 W., Clinton County. The well was first drilled to a depth of 4068 feet, and the producing zone was acidized. The initial production was 120 barrels. Later the well was deepened to 4123 feet Permea bilitv (millidarcvs) Depth (ft.-in.) Vertical Horizontal 1X1X1 cm. 1X1X1 cm. lXlX2cm. 401-0 0.0 0.30 403-0 0.0 161 00 405-0 0.464 0.220 4.4 407-0 18.1 16.8 12.9 409-0 11.4 11.92 9.5 411-0 0.678 1 083 80 413-0 7.7 415-0 12.93 17.2 11.1 416-0 2.88 3.675 6.2 418-0 720 0.833 0.90 420-0 0.648 1.648 0.40 422-0 0.354 0.456 00 424-0 136 0.289 00 426-0 0.258 568 1.0 428-0 0.887 1 003 1.8 431-0 2.02 5.20 9.0 433-0 8.17 9 43 17.9 435-0 1.315 1.013 1.4 437-0 12.43 13.45 13.9 438-0 9.07 8.42 21.5 440-0 0.770 1 004 3.3 442-0 503 11.0 40 444-0 1.198 829 16 445-0 2.89 4.27 1.7 and plugged back to 4121 feet. Water was encountered near the base of the produc- ing zone. The well was shot from 4066 to 4121 feet, and the initial production was 74 barrels of oil and 16 barrels of water. The second well drilled to the "Tren- ton" was the Borton-Storer No. 1, NYV. M NE. \i NE. \i sec. 13, T. 1 N., R. 1 W., Clinton County. The well was com- pleted December 3 with an initial pro- duction of 100 barrels. The top of the "Trenton" was at a depth of 4010 feet, and saturation was reported at depths 4016 to 4024 feet and at 4032 to 4056 feet. The well was drilled to a depth of 4120 and was plugged back to 4070 feet. Water was encountered from 4115 to 4120 feet. Production from both wells has been small. The total production from one of the wells, which flows and pumps by "heads", for a three-months period was estimated to be slightly more than 3000 barrels. Production declined to 30 barrels daily within 13 days after being com- pleted, but further decline in daily pro- duction almost three months later was only 5 barrels. The producing zone consists of light gray to buff crystalline limestone, slightly SALEM POOL dolomitic and cherty, and stylolitic in the lower part (rig. 2). Drill-cuttings from the producing zone showed only slight porosity. Salem Pool The first well to be drilled to the "Tren- ton" limestone in the Salem pool, Marion County, (fig. 1, No. 3), was completed early in 1941. Up to April 22, some 20 additional wells had been completed and 13 others were nearing completion. These wells formerly produced from the Devo- nian limestone but were deepened to the "Trenton." The average depth to the top of" the Kimmswick limestone is 4500 feet, and the total depth of the wells averaged 4625 feet. The largest reported initial production of any well to the above date was 343 barrels, and the average for all wells was 155 barrels. The physical character of the reservoir is such that most of the wells flow by heads, and the amount of oil pro- duced daily is no greater when the wells are pumped. One of the early wells pro- duced approximately 10,000 barrels of oil during 50 days of operation, a more re- cent well, which was drilled as an offset to other producing wells, produced a total of 4300 barrels in 36 days of operation. Although the initial productions are small as compared to wells completed in more porous and permeable formations, production from these wells has been fairly stable. From the available data the decline in daily production for the first month's operation has been in the order of 40 per cent. It appears that the rate of decline of "Trenton" production in the Salem pool will be less than in any other area of "Trenton" production in Illinois. No water has been reported in the wells drilled within the 50 feet of structure be- tween the structurally highest and lowest wells completed to date. It is expected that the area of "Trenton" production will be somewhat smaller than the over- lying Devonian limestone which has a productive area of 5000 acres. Saturation is usually encountered about 25 feet below the top of the Kimmswick limestone and is reported at various in- tervals to an average depth of 105 feet below the top of the limestone. The aver- age thickness of the "pay" is 50 feet. It has been reported that the best saturation is near the base of the Kimmswick which is slightly more than 100 feet thick in the Salem pool. The producing zone consists of buff slightly dolomitic limestone which is fine- to coarse-grained and partly crystalline and is stylolitic in the lower part (fig. 2). A study by a commercial laboratory of a core taken near the base of the producing zone, which is also near the base of the Kimmswick, showed a variation in per- meability of from to 195 millidarcys and an average porosity of 7 per cent. The total water content varied from 8.8 to 34.5 per cent of the pore space, and resid- ual oil averaged 7 per cent of the pore space. Although the amount of core re- covered was small, it appears to be fairly representative of the remainder of the pay when compared with the results of the studies of cores from the Dupo pool. As the available data regarding the character of the producing zones on the Kimmswick limestone are not abundant it is difficult to estimate the ultimate re- covery from that formation in the Salem pool. It is certainly one of the most prom- ising structures for "Trenton" production yet discovered in Illinois. However, the increased costs of drilling, equipment, and operation as a result of the greater depth may cause the abandonment of "Tren- ton" wells in the Salem pool earlier than in pools where the Trenton is shallower, thus resulting in lower ultimate recovery. The other areas of "Trenton" production in Illinois, with the exception of the Cen- tralia pool, are at much shallower depths. In two of these areas the recovery has been to date approximately 800 barrels per acre, and this amount compares with the "Trenton" in Indiana. The Dupo field, however, which offers the best record for "Trenton" production in Illinois, has produced 1900 barrels per acre. In consid- eration of the size of the Salem structure, the nature of the"pay," and the character of the wells completed, it seems within reason to expect an ultimate recovery at least comparable to that in the Dupo pool. Since development of the "Trenton" in the Salem pool began, a well was drilled on structure to a depth 400 feet below the top of the St. Peter sandstone which was encountered at a depth of 5250 feet. No shows were reported below the Kimm- swick limestone. 10 "TRENTON" PRODUCTION IN ILLINOIS LEGEND PRODUCING AREA OF MISSISSIPPIAN STRATA (9,000 ACRES ) PRODUCING AREA OF DEVONIAN STRATA (5,000 ACRES ) PRODUCING AREA OF "TRENTON" AS OF JULY 15, 1941 (900 ACRES ) i ESTIMATED EXTENT OF f "TRENTON" PRODUCTION (2,500 ACRES) KEY TO LOCATION ILLINOIS GEOLOGICAL SURVEY JULY IS, 1941 R I E R 2E Fig. 4.— Area of "Trenton" production in the Salem pool, Marion County, Illinois The available subsurface data to date in the Salem pool indicate that on top of the anticline and on the uppermost part of the east flank the structure conforms fairly well with that of the overlying Devonian limestone. Subsurface data are insufficient to determine the structural relationship on the west flank. ADDENDA Additional data regarding "Trenton" development in the Salem pool have been obtained since the manuscript was pre- pared. As of July 15, 1941, 74 wells were producing from the "Trenton" in the Salem pool, and the productive area proved by drilling was 900 acres. The total productive area of the "Trenton" in the pool is estimated to be 2500 acres (fig. 4). The average initial production of the first 13 wells completed in the pool was 175 barrels and of the wells drilled during June and July 72 barrels. One of the early wells produced approximately 22,000 barrels of oil during six months operation. A decline curve of this well is shown in figure 5. The available subsurface data in the Salem pool indicate that on top of the anticline and on the uppermost part of the east and west flanks the structure con- SALEM POOL II °\ \4 O """8 A O i ) o 10 12 14 NUMBER OF WEEKS 22 24 Fig. 5. — Decline curve of a "Trenton" well in the Salem pool, Marion County, Illinois. forms with that of the overlying Devonian limestone. The "Trenton" limestone has slightly steeper dip than the Devonian, shown in the variation in interval between the tops of the two formations. The interval at the crest of the fold is 1 180 feet. From this point there is an increase of 16 feet in % mile southeast, 18 feet in l}4 miles north- east, and 33 feet in \ x /i miles south. No increase in interval was noted in the short distance west of the crest of the told where the "Trenton" has been tested. Summary Crude-oil production from the "Tren- ton" in Illinois to date represents less than one per cent of the State's total pro- duction. Production has been limited to the upper part of structures with consider- able closure. Shows of oil have been re- ported in the "Trenton" on other struc- tures where it has been tested but com- mercial production was not obtained. As the producing zone has had low porosity and permeability in the known productive areas, initial productions of wells have been small. In the absence of earlv water encroachment the wells should be fairly long lived. The recovery per acre-foot has been much less than that for other pro- ducing formations. The increased depth of the"Trenton," which results in greater drilling and operation costs, makes the testing and development of this formation in the new pools less attractive. However, it is believed that in areas where the "Trenton" is sufficiently porous and per- meable for commercial production and where the structure has sufficient closure, such testing and development is war- ranted although the financial return is slower and smaller than it has been with other formations. Acknowledgments The writer is grateful to the oil com- panies who kindly furnished data used in the report and to Dr. A. H. Bell, head of the Oil and Gas Division, for helpful sug- gestions and criticisms in the preparation of the manuscript. The summary well logs have been pre- pared by L. E. Workman, Head of the Subsurface Division, from sample studies made bv members of that Division. 12 "TRENTON' 1 PRODUCTION IN ILLINOIS SUMMARY LOGS Based on studies of the drill-cuttings from repre- sentative wells in areas of "Trenton" production. 1. Westfield pool, Clark County W. R. Miller— Booth No. 1, SE.H NE. \i NW. M sec. 17, T. 11 N., R. 14 W., Clark County. Surface elevation 665 feet. Drilled 1939. Thick- Formation ness Depth Ft. Ft. Pleistocene system 40 40 Pennsylvanian system Shale, sandstone, lime- stone and coal 270 310 Mississippian system Iowa series Meramec group St. Louis limestone 41 351 Salem limestone 171 522 Osage group Siltstone and sandstone. 556 1078 Kinderhook group Rockford limestone 14 1092 Mississippian-Devonian systems Kinderhook — New Albany shale 106 1198 Devonian and Silurian systems Limestone and dolomite, sandy 77 1375 Limestone and dolomite 505 1880 Limestone and dolomite, pink and gray 170 2050 Ordovician system Cincinnatian series Maquoketa formation Shale, gray 60 2110 Limestone, some shale. 74 2184 Shale, brownish 110 2294 Mohawkian series Kimmswick limestone . . 150 2444 Plattin limestone 18 2462T.D. Associated Producers and Tidewater — Spellbring No. 34, 404 feet from N. line, 926 feet from E. line, NW. y± NW. \i sec. 8, T. 11 N., R. 14 IV., Clark County. Surface elevation 659 feet. Drilled 1924 to 245 feet; deepened in 1936 to 3009 feet. Pleistocene, Pennsylvanian, and Mississippian systems 1165 1165 Devonian and Silurian systems Limestone 825 1990 Ordovician system Cincinnatian series Maquoketa shale and limestone 255 2245 Thick- Formation ness Ft. Mohawkian series Kimmswick limestone, pet- roliferous 163 Plattin limestone, partly pet- roliferous 337 Chazyan series Joachim formation Dolomite, partly petrolif- erous 166 Sandstone, shale and dolo- mite 73 St. Peter sandstone 25 Depth Ft. 2408 2745 2911 2984 3009 2. Martinsville pool, Clark County Trenton Rock Oil and Gas Co. — J. S. Carper No. 13, 330 feet N. of S. line, 330 feet E. of W. line of NE. M sec. 30, T. 10 N, R. 13 W., Clark County. Surface elevation 599 feet. Drilled 1928-29. Pleistocene and Pennsylvanian systems 477 477 Mississippian system Iowa series Meramec and Osage groups No record, except lime- stone at top 808 1285 Osage group First Carper sand 45 1330 Shale? 11 1341 Second Carper sand 55 1396 Kinderhook group Shale? 19 1415 Rockford limestone 11 1426 Mississippian-Devonian systems Kinderhook — New Albany shale '. 124 1550 Devonian and Silurian systems Limestone 131 1681 Limestone, sandy 59 1740 Limestone 511 225 1 Limestone, pink to gray 184 2435 Ordovician system Cincinnatian system Maquoketa formation Shale and siltstone, gray 45 2480 Limestone, some shale. 120 2600 Shale, brown 95 2695 Mohawkian series Kimmswick limestone . . 165 2860 Mohawkian — Chazyan series Plattin and Joachim for- mations 540 3400 Chazyan series St. Peter sandstone 11 3411 SUMMARY LOGS 13 F. D. Strickler-Minnie Jackson No. 1, 350 feet from N. line, 225 feet from IV. line, NE. %, SW. \i sec. 19, T. 10 A"., R. 13 W., Clark County. Surface elevation 555 feet. Drilled 1939. Thick- Formation ness Depth Ft. Ft. Pleistocene and Pennsylvanian systems 410 410 Mississippian system Chester series Limestone, sandstone, and shale 19 429 Iowa series Meramec group Ste. Genevieve limestone . 66 496 St. Louis limestone 160 656 Salem limestone 122 778 Osage group Limestone 132 910 No record 200 1110 Shale, siltstone, and sandstone 291 1401 Kinderhook group Shale, green 9 1410 Rockford limestone 10 1420 Mississippian-Devonian systems Kinderhook — New Albany shale 120 1540 Devonian and Silurian systems Limestone 105 1645 Dolomite, oil shows . . . 37 1682 Sandstone and dolomite, oil shows 23 1705 Dolomite, oil show at top 565 2270 Dolomite, pink to gray . 144 2414 Ordovician system Cincinnatian series Maquoketa formation Shale, gray 23 2437 Limestone and shale ... 30 2467 Dolomite 97 2564 Shale, brownish; some limestone Ill 2675 Mohawkian series Kimmswick limestone, oil show 158 2833 3. Salem pool, Marion County Kingwood Oil Co.—Shanafelt No. 18 A, 614 feet from N. line, 1212 feet from IV. line, NE. \i sec. 20, T. 2 N., R. 2 E., Marion County. Surface elevation 533 feet. Drilled 1939. Pleistocene and Pennsylvanian systems 1200 1200 Mississippian system Chester series Menard limestone and shale 76 1276 Vienna limestone and shale 56 1332 Tar Springs sandstone 103 1435 Glen Dean limestone and shale 42 1477 Hardinsburg sandstone 41 1518 Golconda limestone and shale 137 1655 Cypress sandstone 45 1700 Paint Creek limestone and shale 64 1764 Thick- Formation ness Depth Ft. Ft. Bethel sandstone . 40 1804 Renault formation 51 1855 Aux Vases sandstone 42 1897 Iowa series Meramec group Ste. Genevieve formation Levias limestone mem- ber 9 1906 Rosiclare sandstone and sandv limestone mem- ber 34 1940 Fredonia limestone member 130 2070 St. Louis limestone 180 2250 Salem limestone 276 2526 Osage group Limestone 104 2630 Shale and siltstone 525 3205 Kinderhook group Shale, green 30 3235 Rockford limestone 7 3242 Mississippian-Devonian systems Kinderhook — New Albany Shale 108 3350 Devonian system Limestone and dolomite, petroliferous zones . . . 152 3502 Magnolia Petroleum Co. — Sam Shanafelt No. 32, 334 feet from N. line, 380 feet from W. line of SE. \L SW. Y± sec. 29, T. 2 N, R. 2 E., Marion County. Surface elevation 536 feet. Drilled 1940. Pleistocene, Pennsylvanian and Mississippian systems 3320 3320 Devonian and Silurian systems Limestone and dolomite 960 4280 Ordovician system Cincinnatian series Maquoketa formation Siltstone 19 4299 Shale, grav; siltstone at top ' 46 4345 Shale, gray and brown . . . 35 4380 Shale and dolomite, grav and brown '. 125 4505 Mohawkian series Kimmswick limestone 104 4609 4. Centralia pool, Clinton County Algona Oil Co.—E. B. Marshall No. /, 200 feet from S. line, 221 feet from E. line of SW. l /i sec. 12, T. 1 N., R. 1 ll\, Clinton County. Surface elevation 493 feet. Drilled 1940. Pleistocene system 92 92 Pennsylvanian system 948 1040 Mississippian system Chester series Glen Dean — Golconda for- mations 160 1200 Cypress sandstone 95 1295 Paint Creek shale and limestone 63 1358 Bethel sandstone 52 1410 Renault — Aux Vases for- mations 100 1510 14 "TRENTON" PRODUCTION IN ILLINOIS Thick- Formation ness Depth Ft. Ft. Iowa series Meramec group Ste. Genevieve formation Levias limestone mem- ber 25 1535 Rosiclare sandstone member 25 1560 Fredonia limestone member, and St. Louis and Salem limestones 780? 2340? Osage and Kinderhook groups, Miss. ■ — Dev. shale Shale, siltstone, and lime- stone 532? 2872 Devonian svstem Limestone 65J/£ 2937K Pray and Reynolds, and Borton — Storer No. 1, 196 feet from N. line, 126 feet from IV. line, NE. l /i NE. \i sec. 13, T. 1 N., R. 1 W., Clinton County. Surface elevation 493 feet. Drilled to 2915 by Pray and Reynolds, deepened to 4120 by Borton, 1940; samples below 2909 feet. Pleistocene and Pennsvlvanian systems ' 1085 1085 Mississippian system 1782 2867 Devonian system Dolomite and limestone. . 593 3460 Silurian system Dolomite and limestone, pink and gray 347 3807 Ordovician system Cincinnatian series Maquoketa formation Siltstone 36 3843 Shale, grav; some lime- stone...' 87 3930 Dolomite, brownish 80 4010 Mohawkian series Kimmswick limestone 105 4115 Plattin limestone 4 4119 5. Dupo pool, St. Clair County Ohio Oil Co.—Tarlton No. 7, SW. \i NE. % NE. 14 sec. 33, T. 1 N., R. 10 W., St. Clair County. Surface elevation 580 feet. Drilled 1936. No record 10 10 Mississippian system Iowa series Meramec group Salem limestone 43 53 Osage group Warsaw shale and lime- stone 102 155 Keokuk and Burlington limestones 130 285 Fern Glen limestone and shale Ill 396 Kinderhook group Shale, green 2 398 Chouteau limestone 12 410 Silurian system Limestone 45 455 Thick- Formation ness Depth Ft. Ft. Ordovician system Cincinnatian series Maquoketa formation Shale, gray 55 510 Shale, brown; limestone, sandy 5 515 Limestone, gray; shale at top and bottom. . . 76 591 Mohawkian series Kimmswick limestone, pet- roliferous 46 637 S. G. Lockwood—Dvrof No. 1, N.W cor. NE. M sec. 26, T. 1 N., R. 10 IV., St. Clair County. Surface elevation 590 feet. Drilled 1925. Pleistocene system 26 26 Mississippian system Iowa series Meramec group St. Louis limestone 247 273 Salem limestone 152 425 Osage group Warsaw shale and dolo- mite 75 500 Keokuk and Burlington limestones 181 681 Fern Glen shale and lime- stone 74 755 Kinderhook group Chouteau limestone 30 785 Grassy Creek shale 13 798 Silurian svstem Dolomite 70 868 Ordovician system Cincinnatian series Maquoketa formation Shale, gray 57 925 Shale, brown 10 935 Siltstone; and dolomite, silty 15 950 Shale and limestone, brownish 65 1015 Mohawkian series Kimmswick limestone . .. . 98 1113 Plattin limestone and dolo- mite 212 1325 Chazyan series Joachim dolomite 148 1473 St. Peter (and Joachim?) sandstone 159 1632 Prairie du Chien series Powell and Cotter dolo- mites 263 1895 Jefferson City dolomite 260 2155 Roubidoux formation Dolomite, sandy 85 2240 Sandstone and sandy dolomite 45 2285 Gasconade and Van Buren dolomites 210 2495 Gunter sandstone and sandy dolomite 35 2530 Cambrian system St. Croixan series Eminence dolomite 234 2764 Potosi dolomite 140 2904 SUMMARY LOGS 15 6. Waterloo pool, Monroe County Hughes Petro/eum Corp.— Urn. Myer No. 1, 295 feet from N. line, 358 feet from E. line of SIV. x /i SE. \i sec. 88, T. 2 $.,R. 10 IF., Monroe County. Surface elevation 575 feet. Drilled 1939. Thick- Formation ness Depth Ft. Ft. Pleistocene svstem Glacial drift 28 28 Mississippian system Iowa series Meramec group St. Louis limestone 162 190 Salem limestone 170 360 Osage group Warsaw shale and lime- stone 115 475 Keokuk and Burlington limestones 103 578 Fern Glen limestone 107 685 Silurian system Limestone 27 712 Ordovician system Cincinnatian series Maquoketa formation Shale, gray 83 795 Sandstone 25 820 Limestone and shale . . . 35 855 Mohawkian-Chazyan series Kimmswick-Plattin lime- stones and Joachim dolomite 485 1340 Chazyan series St. Peter (and Joachim?) sandstones 147 1487 Prairie du Chien series Powell and Cotter dolo- mites 88 1575 Eugene Hoffer—J. H. Bover No. 2, 329 feet from S. line, 1262 feet from IF. line, SE. % sec. 19, T. 1 S., R. W IF., Monroe County. Surface elevation 405 feet. Drilled 1940. Thick- Formation ness Depth Ft. Ft. No record 155 155 Mississippian system Iowa series Meramec group Salem limestone 83 238 Osage group Warsaw limestone, dolo- mite, and some shale 128 366 Keokuk and Burlington limestones 189 555 Fern Glen limestone 69 624 Silurian system Limestone 29 653 Ordovician system Cincinnatian series Maquoketa shale Shale, gray 75 728 Limestone and shale . . 65 793 Mohawkian series Kimmswick limestone. ... 86 879 Plattin limestone 221 1100 Chazyan series Joachim dolomite 145 1245 St. Peter (and Joachim?) formation Sandstone, incoherent. . 98 1343 Dolomite, sandy; sand- stone, partly dolomitic 47 1390 Sandstone, incoherent . 17 1407 Prairie du Chien series Powell and Cotter dolo- mites 286 1693 Jefferson City dolomite ... 202 1895 Roubidoux sandstone and sandy dolomite 170 2065 Gasconade and Van Buren dolomites 155 2220 Illinois State Geological Survey Illinois Petroleum No. 39 1941