General Field Information |
| Produces Oil: Yes Produces Gas: Yes |
| Geologic Province: |
Hugoton Embayment |
| Exploration Method: |
Swope reservoir discovered from astute "uphole" sample examination by wellsite geologist (Hugh Caughey) on deep wildcat test. |
| Surface Formation: |
Pleistocene alluvium underlain by Upper Permian red beds (White Horse Formation). |
| Oldest Formation Penetrated: |
Arbuckle (one well in Comanche County has penetrated through the Arbuckle, west of the field, in 17-33S-20W). |
| Drilling Casing Practices: |
Most wells are drilled through the Swope Limestone and pipe set through the pay zone. The wells are completed through perforations with an acid stimulation. The acid treatments commonly use 2,000 to 5,000 gallons of 15% HCI acid.
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| Electric Logging Practices: |
Logs were run on almost every well. The most common log suite consists of a Gamma-ray, Self Potential, Dual Induction/ Gamma-ray, Compensated Neutron Density. |
| Comments: |
Red Book author: Bob Slamal, GeoStrata Exploration, Wichita, KS. General Field data is as of 12-31-1984.
More than a dozen of the wells in this field are dual completion.
Other Shows: Considering only the available geologist's reports and DST's, the 'Elgin' sandstone appears to be the only other zone with any significant shows (and it appears to be water bearing). Secondary shows seem to be quite rare compared to the subregional significance of the large anticline this field is located on.
Because of the spirit of cooperation and sharing of knowledge the author ahs experienced with many Kansas geologists, this additional subsurface information is added. The down-dip portion of this "isolated" body of reservoir rock is in hydraulic communication with an area of sub-regional faulting/flexure to the immediate south of the field in southwest Comanche County. This flexure zone exhibits over 500 feet of vertical displacement on top of the Ordovician rocks. The exploration importance of this fact is eloquently debated in John Rich's insightful A.A.P.G. Bulletin articles (1930) and further elaborated upon by Davis (1984).
Authors Note on Correlation: Much confusion has arisen concerning correlation of the lower KC Group zones east to west across the broad Pratt Anticline area. Most of these problems stem from the fact that the Stark Shale member of the Dennis Limestone Formation looses its characteristic hot gamma ray log kick over western Pratt County and the NW portion of Barber County. The Pratt and Kiowa County KGS type logs (1966 ed.) have the Stark Shale picked one cycle too low (on the Hushpuckney Shale, which has a more consistent hot gamma ray log response). The Comanche County log also has the Stark Shale picked too low, on a locally occurring black shale, 20 feet above the Hushpuckney Shale. The author has done extensive well-to-well correlation work along the southern edge of Kansas (away from the influence of the C.K.U. and Pratt Anticline) and agrees that the Swope Limestone of Collier Flats field is the stratigraphic equivalent of the Swope Limestone if the Sedgwick Basin area (Stribling, 1984), and the named and described outcrops in eastern Kansas (Watney, 1985, personal communication). |
| Discussion: |
The Collier Flats field, producing primarily from the Swope Limestone Formation of the Kansas City Group, was discovered in 1970 and consisted of only five wells until 1978 when a significant additional discovery was made about four miles south. This southern find was named Lemon Ranch field and eventually development drilling (mostly during 1980-1982) of the Lemon Ranch and Collier Flats South fields resulted in combination of the pools under one name by the Kansas Geological Society Nomenclature Committee: Collier Flats.
Additional pay zones will only be mentioned briefly. The Toronto Limestone produces from about a dozen wells (often comingled with Swope production). Some geologists have referred to this zone as Amazonia Limestone of the Douglas Group because of the thickness (about 50 feet) of this limestone beneath the excellent subsurface marker couplet; Heebner Shale/Leavenworth Limestone. Perforations are usually about 25 to 30 feet below the base of the Heebner Shale. The pay zone often has a relatively high gamma ray emission for a producing limestone.
The Drum Limestone Formation produces in only 3 wells. Probably because of neglect to recognize the regional southwest thickening of the Kansas City Group this zone has been miscorrelated and named Iola Limestone on much of the field information. This zone has a distinct log signature over much of this area and is found 155 feet above the Stark Shale radioactive marker in the producing wells in Section 35, Township 33 South, Range 20 West.
The Mississippi Limestone produces primarily gas from discontinuous porosity developments along the Collier Flats anticline. These wells produce from the St. Louis and St. Genevieve subcrops and are low initial production wells. The poor economic return from these wells is attested to by the fact that most wells within the field stop just below the Swope Limestone pay zone.
The structure of this field consists of a slightly asymmetrical south plunging anticline with a steeper dip along the west flank. There is approximately 90 feet of dip across the field north to south, mapped on top of the Swope pay zone, from the highest producer to the lowest "good" well. This southward dip on top of the Swope Limestone along the crest of the anticline within the field area is 19 feet/mile (equivalent to one-fifth of one degree of dip). The regional southward dip of the Swope in Range 20 West in Comanche County averages 28 feet/mile. The slight flattening of regional dip and lack of significant structural closure along the Collier Flats anticline clearly directs one to look closely at the stratigraphic component of this Swope production.
Abundant core and log data show this production to be from an oolite shoal developed at the top of the regressive Bethany Falls Member of the Swope Limestone Formation. The pay zone is absent or has no effective porosity in the dry and out-of-field wells in the southwest corner of Comanche County. The present day structure of the field is important in that it evidently represents an expression of an ancient positive element that localized the development of the oolite shoal. The positive nature of this area after Swope deposition is evident from straightforward interpretation of root casts, subaerial crust, caliche, and extensive solution cavities and fissures from core examination. In summary the pay zone is an oolite shoal that has greatly enhanced reservoir qualities because of subaerial exposure. It is essentially an isolated porosity pod localized on an anticline, surrounded by stratigraphic equivalent rock that is impermeable.
The down-dip portion of this isolated body of reservoir rock is in hydraulic communication with an area of sub-regional faulting/flexure due south of the field in SW Comanche County, which exhibits over 500 feet of vertical displacement on top of the Ordovician rocks. |
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| Geological Age: |
Pennsylvanian, Missourian
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| Depositional Environment: |
An oolite shoal representing the culmination of the Swope Limestone Formation marine cycle. The reservoir is found in the top of the regressive marine limestone member; the Bethany Falls Limestone. |
| Formation Lithology: |
61 wells; Limestone, packstone-grainstone, tan-brown, medium crystalline, fossiliferous, highly oolitic, fair to good oomoldio-intercrystalline-vuggy pososity. See log of Swope interval. |
| Formation Geometry: |
All formations produce from discontinuous porosity developments along a south plunging anticline that is one to one-and-a-half miles wide. The Swope Limestone production is primarily along the crest and west flank of the anticline. |
| Trap Type: |
Combination |
