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Kansas Geological Survey, Subsurface Geology Series 9, originally published in 1987
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Number of producing zones per 1/4 township

Three maps are used to summarize the number of locally producing pay zones in the state; these maps are the number of oil-producing zones (figure 31), the number of gas-producing zones (figure 32), and the total number of producing zones regardless of whether they produce oil or gas (figure 33). About one-half of the 3,900 producing fields in the state are single-pay fields. These fields, account for about one-fifth of the cumulative production in Kansas (Ebanks, 1975). All major fields in Kansas have multiple pay zones; however, one is usually more important than the others (Merriam and Goebel, 1959). Several fields with multiple zones are on the Central Kansas uplift. Other areas with several pay zones, either stacked atop each other in a single field or in close geographic proximity to each other in separate fields, include the Pratt anticline, the Hugoton basin in the vicinity of Seward and Meade counties, and the Nemaha uplift in the vicinity of Butler and Cowley counties. Gas-producing areas are largely limited to the south-central and southwestern part of the state, with minor production also extending up through eastern Kansas. The maximum number of gas pay zones producing in close proximity to each other (figure 32), like the maximum number of oil pay zones (figure 31), are located over the Pratt anticline in south-central Kansas. In areas such as the Pratt anticline, the Sedgwick basin, and Cherokee basin, gas production is generally spatially coincident and associated with oil production. Gas production dominates in the Hugoton embayment while oil production is more prevalent in the central and northern reaches of the Central Kansas uplift.

Figure 31--Number of producing zones per 1/4 township (oil only).

Kansas map; townships with multiple zones are in Central Kansas uplift and south-central Kansas.

Figure 32--Number of producing zones per 1/4 township (gas only).

Kansas map; most townships are single zones; a few multiple zones in south-central Kansas.

Figure 33--Number of producing zones per 1/4 township.

Kansas map; townships with multiple zones are in southern part of Central Kansas uplift and in western part of southeast Kansas.

The maps showing the number of producing zones were produced by a computer search that counted the number of pay zones in each well in the data base and added this total to other zones counted in any wells within a distance of 3 mi (an area approximately equal to 1/4 township). A maximum number of 12 producing zones are possible at any given locality. These zones correspond to the individual pay zones in this report. The Arbuckle and sub-Arbuckle zones were combined as a single zone for this computer search, as were all the Permian zones.

Many factors may influence the pattern on these maps. For example, some fields may have a pay horizon developed as a weathered zone beneath an unconformity. If this unconformity is an angular unconformity such as the sub-Pennsylvanian unconformity, several units may crop out beneath the unconformity. If these units produce oil along the unconformity, each of them would probably be reported as an individual producing zone, even though, in reality, the field consists of only one weathered, porous zone that transects several separate units. The El Dorado field in Butler County is susceptible to this type of counting error in that the Stapleton zone, a major pay horizon in this field, is partly a weathered zone developed underneath the sub-Pennsylvanian unconformity. The Arbuckle, Simpson, and Viola all crop out beneath this unconformity and produce oil and are counted as three separate zones. However, instead of being three separate producing zones, they are in effect only components of a single zone.

Several productive zones could also be counted as only one of the pay zones in this report. The pay-zone categories used in this report may comprise a considerable thickness of strata, and several potential reservoir units could be productive within each of these intervals. For example, the Lansing Group, which is included as a Lansing-Kansas City-Pleasanton pay zone in this report, can contain several separate pay zones within it. However, regardless of how many Lansing pay zones an individual well may pump, the computer search would only recognize them as a single Lansing-Kansas City-Pleasanton pay zone. This situation occurs on the Central Kansas uplift, where numerous fields commonly contain several stacked Lansing-Kansas City pay zones. Similarly, several separate Cherokee shoestring sandstone bodies could produce oil in a given field in eastern Kansas, but in the data base these zones would be categorized only as undifferentiated Cherokee-Marmaton production.

The number of pay zones in a given area is not only a function of the geology and computer-search technique but also of the exploration maturity of an area. A greater number of pay zones would be expected in more densely drilled areas because there would be less chance of minor pay zones being overlooked. Optimistically, several recently discovered fields with only one pay zone will, with time, have new pay zones discovered either by deeper drilling or by outpost, infill, and other nearby exploratory or production drilling. Exploration activities concentrated along trends defined by the number of pay zones may possibly prove fruitful, particularly if a trend appears "underdeveloped" (i.e. with relatively few pay zones) compared to other nearby trends.

Depth of pay zones

Another way to examine oil and gas production in the state is to look at it from the perspective of depth rather than number of producing zones or stratigraphic horizon. Geologic strata can be regionally deformed into basins and uplifts, or locally deformed into anticlines and synclines (figure 34). Therefore, petroleum production from a given pay zone will be found at widely varying depths in different parts of the state.

Figure 34--Geologic map and cross section of Kansas.

Kansas geologic map and cross section.

Both subsurface and subsea depths can be considered when examining petroleum production. Geologists usually map geologic structures using subsea depths, but engineers and investors, who look closely at drilling costs and logistics, are also interested in the depths potential pay zones are below ground level. Conversion between subsea and subsurface depths is simple. A subsea depth for a geologic horizon at a well locality is obtained by subtracting the depth that horizon is below ground level (the subsurface depth) from the elevation of the well (the surface datum). For example, a unit found at a depth of 3,000 ft (915 m) below the surface by a well drilled at a locality 2,000 ft (610 m) above sea level would therefore be at a subsea depth of -1,000 ft (-305 m).

Ground-level elevations in Kansas can be quite variable, but in general, elevations increase westward toward the Rocky Mountains. The highest point in Kansas is Mount Sunflower (4,039 ft; 1,232 m) in Wallace County; the lowest point (approximately 680 ft; 207 m) is along the banks of the Verdigris River where its waters leave the southeast part of the state in Montgomery County. Subsurface depths of a given producing formation will generally increase westward in Kansas due to the general westward tilt of the geologic strata and the general westward increase in surface elevation.

A subsurface map (figure 35) and a subsea depth map (figure 36) are presented in this report. Inasmuch as a well can have commingled production from two or more zones, only the deepest producing zone was considered in generating these maps. The type of production (gas, oil, oil and gas) is not differentiated by color on figures 35 and 36 as they are on the pay-zone maps (figures 13, 15-30). Instead, color is used in the depth maps to correspond to depth intervals, with greater depths corresponding to hotter colors (red, orange, yellow) and cooler colors (purple, blue, green) corresponding to shallower depths.

Figure 35--Depth from surface to deepest pay zone.

From surface, deepest pays are in SW Kansas, shallowest in SE; are additional shallow pays in NW; some mediumn pays in SW near the deepest pays.

Figure 36--Subsea depth of deepest pay zone.

From subsea datum, deepest pays are in SW Kansas, eastern pays move from shallowest to medium; shallowest are in NW counties.

The map with pay zones displayed according to subsea depths (figure 36) has fewer data points than the map showing subsurface depths (figure 35). The reason for this is that several wells in the data base were reported without their surface elevations from which subsea depths could be calculated. Some interesting features are revealed by comparing the subsurface and subsea depth maps. If subsea depths are considered (figure 36), the deepest production in Kansas is in Meade and Clark counties. However, if subsurface depths are considered (figure 35), the deepest production is farthest west, in Seward and Stevens counties. The reason for this is that Seward and Stevens counties generally have a higher elevation than Meade and Clark counties.

Permian gas production in the Hugoton field in southwestern Kansas is found between +500 and -500 ft below sea level (figure 36). This depth interval is comparable to the subsea-depth interval at which Pennsylvanian oil and gas is found in eastern Kansas. However, the Hugoton production is much deeper when subsurface depths are considered (figure 35). Conversely, the Cretaceous shallow-gas production in northwestern Kansas is comparable to the eastern Kansas Pennsylvanian production when considering subsurface depths. With respect to sea level, however, the northwestern Kansas Cretaceous production is 1,500 ft above sea level, considerably higher than the eastern Kansas production.

In order that the distribution of oil and gas production versus drilling (subsurface) depth (figure 35) can be observed, a series of seven depth-slice maps are presented (figures 37a-43a). Each slice represents a 1,000-ft depth interval. Hydrocarbon-producing wells in this series of maps are color-differentiated with respect to type of production (oil, gas, or oil and gas). The distribution of data points on these maps is both a function of the geologic structure and overlying surface topography. The deepest production in the state occurs in southwestern Kansas in the Hugoton basin. The shallowest production is in eastern Kansas in the Cherokee basin. Another series of depth-slice maps (figures 37b-43b) that categorize production according to geologic horizon are also presented with the production depth-slice maps (figures 37a-43a). Comparison of the two series of maps will help the user identify the type of production in a given area, its approximate subsurface depth, and the producing formation. Such comparisons may be useful to those who may want to quickly evaluate the merits of several different exploration plays in terms of production costs and profitability of oil versus gas.

Figure 37a--Kansas petroleum production differentiated by type of production for 1,000-ft depth slices. Depths are subsurface depths.

0 to 1000 feet: Gas in Nemaha uplift, Sedgwick basin, and NW Kansas; oil in eastern counties.

Figure 37b--Kansas petroleum production differentiated by producing zone for 1,000-ft depth slices. Depths are subsurface depths. Producing zones are color coded; abbreviations correspond to various colors as follows: APA, Arbuckle, sub-Arbuckle; VMS, Simpson, Viola, Maquoketa; MCMH, Silurian-Devonian limestones, Misener, Chattanooga, Mississippian limestones; DMA, Morrow, Atoka, Cherokee, Marmaton; MISSOU, Pleasanton, Lansing, Kansas City; V, Douglas, Shawnee, Wabaunsee; P, Permian; and M, Niobrara.

0 to 1000 feet: Niobrara in NW, Permian in Nemaha uplift, Sedgwick basin; Morrow, Atoka, Cherokee, Marmaton in eastern counties.

Figure 38a--Kansas petroleum production differentiated by type of production for 1,000-ft depth slices. Depths are subsurface depths.

1000 to 2000 feet: Gas in Central Kansas uplift, Sedgwick basin, and NW counties; oil and gas in Nemaha uplift, eastern counties.

Figure 38b--Kansas petroleum production differentiated by producing zone for 1,000-ft depth slices. Depths are subsurface depths. Producing zones are color coded; abbreviations correspond to various colors as follows: APA, Arbuckle, sub-Arbuckle; VMS, Simpson, Viola, Maquoketa; MCMH, Silurian-Devonian limestones, Misener, Chattanooga, Mississippian limestones; DMA, Morrow, Atoka, Cherokee, Marmaton; MISSOU, Pleasanton, Lansing, Kansas City; V, Douglas, Shawnee, Wabaunsee; P, Permian; and M, Niobrara.

1000 to 2000 feet: Niobrara in NW, Permian in Nemaha uplift; Viola in Sedgwick basin; Several zones in eastern counties.

Figure 39a--Kansas petroleum production differentiated by type of production for 1,000-ft depth slices. Depths are subsurface depths.

2000 to 3000 feet: Gas in SW and Pratt anticline; oil in Central Kansas uplift uplift, Sedgwick basin, eastern counties.

Figure 39b--Kansas petroleum production differentiated by producing zone for 1,000-ft depth slices. Depths are subsurface depths. Producing zones are color coded; abbreviations correspond to various colors as follows: APA, Arbuckle, sub-Arbuckle; VMS, Simpson, Viola, Maquoketa; MCMH, Silurian-Devonian limestones, Misener, Chattanooga, Mississippian limestones; DMA, Morrow, Atoka, Cherokee, Marmaton; MISSOU, Pleasanton, Lansing, Kansas City; V, Douglas, Shawnee, Wabaunsee; P, Permian; and M, Niobrara.

2000 to 3000 feet: Permian in SW and Pratt anticline; Douglas, Shawnee, Wabaunsee in SW; Several zones in eastern counties and Sedgwick basin; Pleasanton, Lansing, Kansas City in Central Kansas uplift.

Figure 40a--Kansas petroleum production differentiated by type of production for 1,000-ft depth slices. Depths are subsurface depths.

3000 to 4000 feet: Gas in far SW and Pratt anticline; oil in Central Kansas uplift, Sedgwick basin.

Figure 40b--Kansas petroleum production differentiated by producing zone for 1,000-ft depth slices. Depths are subsurface depths. Producing zones are color coded; abbreviations correspond to various colors as follows: APA, Arbuckle, sub-Arbuckle; VMS, Simpson, Viola, Maquoketa; MCMH, Silurian-Devonian limestones, Misener, Chattanooga, Mississippian limestones; DMA, Morrow, Atoka, Cherokee, Marmaton; MISSOU, Pleasanton, Lansing, Kansas City; V, Douglas, Shawnee, Wabaunsee; P, Permian; and M, Niobrara.

3000 to 4000 feet: Arbuckle, sub-Arbuckle, Pleasanton, Lansing, Kansas City in Central Kansas uplift.

Figure 41a--Kansas petroleum production differentiated by type of production for 1,000-ft depth slices. Depths are subsurface depths.

4000 to 5000 feet: Gas in far SW and southern part of Central Kansas Uplift; oil in Central Kansas uplift, SW counties.

Figure 41b--Kansas petroleum production differentiated by producing zone for 1,000-ft depth slices. Depths are subsurface depths. Producing zones are color coded; abbreviations correspond to various colors as follows: APA, Arbuckle, sub-Arbuckle; VMS, Simpson, Viola, Maquoketa; MCMH, Silurian-Devonian limestones, Misener, Chattanooga, Mississippian limestones; DMA, Morrow, Atoka, Cherokee, Marmaton; MISSOU, Pleasanton, Lansing, Kansas City; V, Douglas, Shawnee, Wabaunsee; P, Permian; and M, Niobrara.

4000 to 5000 feet: Silurian-Devonian limestones, Misener, Chattanooga, Mississippian limestones in Central Kansas uplift; Morrow, Atoka, Cherokee, Marmaton in SW counties.

Figure 42a--Kansas petroleum production differentiated by type of production for 1,000-ft depth slices. Depths are subsurface depths.

5000 to 6000 feet: Oil and gas in SW Kansas.

Figure 42b--Kansas petroleum production differentiated by producing zone for 1,000-ft depth slices. Depths are subsurface depths. Producing zones are color coded; abbreviations correspond to various colors as follows: APA, Arbuckle, sub-Arbuckle; VMS, Simpson, Viola, Maquoketa; MCMH, Silurian-Devonian limestones, Misener, Chattanooga, Mississippian limestones; DMA, Morrow, Atoka, Cherokee, Marmaton; MISSOU, Pleasanton, Lansing, Kansas City; V, Douglas, Shawnee, Wabaunsee; P, Permian; and M, Niobrara.

5000 to 6000 feet: Silurian-Devonian limestones, Misener, Chattanooga, Mississippian limestones, Morrow, Atoka, Cherokee, Marmaton in Southwest Kansas.

Figure 43a--Kansas petroleum production differentiated by type of production for 1,000-ft depth slices. Depths are subsurface depths.

Deeper than 6000 feet: Oil and gas in SW Kansas.

Figure 43b--Kansas petroleum production differentiated by producing zone for 1,000-ft depth slices. Depths are subsurface depths. Producing zones are color coded; abbreviations correspond to various colors as follows: APA, Arbuckle, sub-Arbuckle; VMS, Simpson, Viola, Maquoketa; MCMH, Silurian-Devonian limestones, Misener, Chattanooga, Mississippian limestones; DMA, Morrow, Atoka, Cherokee, Marmaton; MISSOU, Pleasanton, Lansing, Kansas City; V, Douglas, Shawnee, Wabaunsee; P, Permian; and M, Niobrara.

Deeper than 6000 feet: Silurian-Devonian limestones, Misener, Chattanooga, Mississippian limestones in Southwest Kansas.


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Kansas Geological Survey, Energy Research
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