McLouth Gas and Oil Field, Jefferson and Leavenworth Counties, Kansas

Abstract

This report is an expansion of an earlier report on the McLouth gas and oil field published in 1941 and includes developments to April 1, 1943_ The report discusses the McLouth field and its relations to the Forest City basin and to the structure of the region as a whole.

On April 1, 1943, the McLouth field included three pools, the North McLouth; McLouth, and Ackerland, comprising an area of 4,610 acres yielding oil and gas. The area of oil production comprises 550 acres. The field was discovered in November, 1939, and there were 90 wells yielding gas and 21 wells producing oil on April 1, 1943.

A normal sequence of Pennsylvanian rocks starting with the Lecompton limestone is encountered in wells. The Cherokee shale, which includes the McLouth sand, consists of alternating deposits of shale and impure sandstone. The McLouth sand is composed of sandstone and shale zones of variable character and porosity, and its productivity is controlled by porosity and structural conditions. The McLouth sand immediately overlies the eroded and beveled edges of low-dipping Mississippian limestone formations.

The Mississippian rocks include St. Louis, Spergen, Warsaw, undivided Burlington and Keokuk (which includes the main oil-producing zone of the field), Gilmore City, and Chouteau limestones. Clastic black shale occurs in caverns in the Mississippian at irregular stratigraphic intervals.

The Mississippian limestones are underlain in descending order by the Chattanooga shale, Devonian limestone, Maquoketa (= Sylvan) shale (of local occurrence), Kimmswick (= Viola) limestone, St. Peter sandstone, and Arbuckle limestone, the top of which has been penetrated in two wells in the field.

There are three producing zones in the McLouth field. The first is the McLouth sand, of early Pennsylvanian age, from which all of the gas and minor amounts of oil are produced. This gas and oil are produced from porous erratically spaced sand bodies on anticlines. The second zone consists of porous weathered limestone at the top of the Mississippian which has yielded small amounts of gas and shows of free oil. The third zone consists of porous dolomite approximately 150 feet below the top of the Mississippian. The porosity of the dolomite is seemingly a result of an unconformity during the period of deposition of the undivided Burlington and Keokuk limestones. There are several potential producing zones, as yet unproductive in the McLouth field, which yield oil in other pools in Kansas and in parts of southeastern Nebraska. These zones occur at the top of the Devonian where shows of oil have been encountered in the McLouth field, at the top of the Kimmswick, in the St. Peter sandstone, and at the top of the Arbuckle limestone. None of these zones has been adequately explored in the McLouth field and, in general, in northeastern Kansas.

During pre-St. Peter time, the Ozark region was subsiding and southeastern Kansas was rising. After deposition of the St. Peter sandstone across the eroded edges of the earlier rocks the structural movements were reversed, and until the end of Chattanooga time parts of southeastern Nebraska were subsiding and the general area of the Ozarks was rising.

Unconformities at the base of the Pennsylvanian rocks, at the base of the Chattanooga shale, and at the base of the Devonian rocks are important. Before the deposition of the Devonian rocks, the older strata were tilted to the northwest toward the area of subsidence in southeastern Nebraska and were subjected to erosion and beveling. All the Silurian rocks and most of the Maquoketa shale were eroded in the McLouth field, and the Devonian rocks were deposited upon the beveled edges of the older formations. After deposition of Devonian limestones, a similar tilting of the surface toward the northwest occurred. This was followed by erosion and beveling of the Devonian limestones and older rocks. The Chattanooga shale was deposited upon this beveled surface. There is much variation in porosity of rocks at the top of the Devonian in different areas. The occurrence of impermeable rocks in the upper part of the Devonian in one anticline thus does not mean that similar impermeable conditions prevail elsewhere.

The Mississippian limestones were deposited upon the Chattanooga beds without marked angular unconformity. At the end of Mississippian deposition, the region was re-elevated and the northeasterly trending Nemaha anticline and other subsidiary parallel structures were developed. The surface of the beveled Mississippian formations was reduced to a peneplain; it was then re-elevated ani a fault escarpment on the east side of the Nemaha fold was developed. At the same time, gentle subsidence warped the surface east of the escarpment and produced the Forest City and Cherokee basins which trend south from northeastern Kansas to Arkansas and Oklahoma. These basins probably were at first separated by the Bourbon arch, a broad low structural divide trending northwest from Bourbon county, Kansas. The earliest Pennsylvanian deposition in northeastern Kansas was in the deepest part of the Forest City basin, but as regional subsidence continued the Bourbon arch was submerged. The McLouth sand was deposited approximately at the time the Forest City and Cherokee basins were united.

During deposition of the Pennsylvanian rocks, the Forest City basin continued to subside by differential movements, and structural features that were initiated after deposition of the Mississippian rocks continued to develop. After deposition of the Permian rocks, the surface of Kansas and parts of adjoining states was tilted toward the northwest and the exposed cocks were beveled and ultimately buried by deposits of Cretaceous age. The development of the westerly regional dip in the Pennsylvanian rocks had an important effect on the expression of the structure of the gently dipping surface rocks.

The McLouth sand was deposited upon the beveled and warped surface of the Mississippian which had not previously been submerged in the area of the McLouth field. The gentle structure of the surface rocks overlies steeper structure in the underlying rocks because of continued' differential warping. The regional tilt modified the expression of the weak surface structures and in many places decreased the areas of closure and shifted the positions of the crests of the surface anticlines in the McLouth field. The structural features of the older rocks were steeper than those of the younger rocks, and although the regional dip resulted in alteration of the closure, no perceptible change in the positions of the crests occurred.

The McLouth sand ranges from clay through coarse sand and intraformational conglomerates. It ranges in thickness from 15 to 95 feet. The variations in the thickness of the McLouth sand are due to the topographic relief of the underlying surface and the gentle structural deformation which was active before and during its deposition. Seven lithologic zones have been recognized. Four of these are predominantly sandy, and three are shaly. The zones are extremely variable laterally and almost all contain carbonaceous material. It is believed that this variability is due to deposition upon a slowly subsiding plain of aggradation at or slightly below sea level.

The gas reservoirs are sealed on the flanks of the anticlines by tar and dried oil which fill the interstices of the sand and thus exclude water. The planes of contact between the tar and the gas and between the water and the tar conform to the regional dip. When regional dip is eliminated, the gravitational distribution of the water, tar, and gas in the anticlines is essentially symmetrical with the structure of the anticlines before development of the regional dip. It is concluded, therefore, that oil and tar entered the anticlines in a fluid state before regional tilting and that later desiccation of the oil prevented gravitational readjustment of the oil and gas after regional tilting. The original accumulation of hydrocarbons in the reservoir thus took place at a time when the only areas that could contribute to the pools were adjoining synclinal areas. Therefore, the oil and gas in this case did not migrate long distances up the regional dip. Because the oil is desiccated and because the original closed pressure in the gas fields is lower than might be expected, one is led to speculate as to the possibility that large amounts of gas may have escaped from the anticlines from time to time when structural movements occurred.

The cumulative gas production to April 1, 1943, from the three pools was approximately 7 billion cubic feet. The calculated ultimate production from the developed area is slightly more than 9 billion cubic feet. Declines of pressure in the three pools of the McLouth field indicate a short life for these pools. The cumulative production of oil to April 1, 1943, was approximately 176,000 barrels. The peak of oil production had not been reached at that date. The oil is produced principally from a small area of Mississippian rocks on the crest of a dome underlying a part of the much larger gas-charged area in the McLouth sand. Oil in the McLouth sand comes from several isolated areas in the three pools. The Bankers Life pool with six wells and an area of 120 acres is the largest.

Hempel analyses reveal that oil from the McLouth sand and oil from the Mississippian dolomite are almost identicaL There can be little doubt that oil has migrated upward from Mississippian rocks into the McLouth sand in the Bankers Life pool which is bounded on the north by a fault. Scattered wells in the other gas pools yield oil of the same character as that in the Bankers Life pool. It is believed, therefore, that concealed faults or perhaps only joints and crevices have permitted leakage of oil from below into the McLouth sand at other points than in the Bankers Life pool and that Mississippian oil pools of limited areal extent will be found beneath other structural crests in the McLouth field.

The character of the oil in the McLouth field. is unusual, as indicated by the curves of correlation indices calculated from Hempel analyses. Such curves also reveal that oils from the Devonian and Kimmswick limestones of the Falls City pool of southeastern Nebraska are similar to those in the McLouth field. This suggests that the source beds of both areas were similar, that both had a similar dynamic history, and that the oil in the McLouth field may have been derived from source beds at least as old as the Kimmswick limestone. It seems possible, however, that the tar and dried oil bordering the gas reservoir in the McLouth sand and the original accumulations of gas may have been derived from the McLouth sand but that the undesiccated oil found locally in the McLouth sand came from a deeper source. Part of the gas may also have migrated upward through the same channels.

Conditions in the McLouth field increase the hope that oil and gas will be found in similar relations in extensions of the McLouth field and also in other places in northeastern Kansas, It may be expected that at least some of the anticlinal gas pools of northeastern Kansas, when drilled to Mississippian rocks, may yield oil on the crests of Mississippian anticlines, and that some anticlines now apparently condemned, when tested with due consideration of the shifting of the crests of weak surface structures, may be found to be productive.