General Field Information |
| Produces Oil: Yes Produces Gas: Yes |
| Geologic Province: |
Hugoton Embayment, Anadarko Basin |
| Exploration Method: |
Mapping of Krider high associated with regional geological information |
| Surface Formation: |
Carlile shale |
| Oldest Formation Penetrated: |
St. Louis |
| Drilling Casing Practices: |
St. Louis and Morrow: Drilled with mud, geologist on site to correlate drilling time and to describe sample cuttings.
St. Louis Completion: Perforations through pipe; acid to stimulate; two of four successful St. Louis completions required fracture treatment.
Morrow Completion: Perforations through pipe; of seven successful Morrow wells, two were completed natural, four required acid and one required fracture treatment. |
| Electric Logging Practices: |
Compensated Density / Compensated Neutron, Dual Induction Laterolog |
| Discussion: |
The Congdon Field is located in the north central portion of the Hugoton Embayment. Oil production is found in the Mississippian St. Louis as wells as in the Pennsylvanian Morrow formations. The oil field is overlain by shallow gas production of Permian age that is part of the great Hugoton gas field and shall not be discussed here.
Basement rock in the northern Hugoton Embayment is believed to be fractured and resulted in a series of deep-seated horst and graben structures. The developing fault planes remain active as younger sediments were deposited with the majority of the movement occurring prior to the end of Mississippian time.
As the warm, shallow epicontinental seas of Mermecian age mildly advanced and retreated throughout the Hugoton Embayment localized oolictic shoals developed on pre-existing highs on the seafloor. In the Congdon Field, a St. Louis oolitic shoal deposit holds commercial amounts of oil on the upthrown side of a steeply dipping fault that strikes NE-SW. This bank deposit enhanced the development of a north-south trending anticline that is bisected on the southern end by the fault. Productive shoal facies rocks persist south of the fault but are much thinner and of poorer reservoir quality.
Significant fault displacement had probably stopped by the end of Mississippian time. Subaerial exposure allowed a drainage pattern to develop on the downthrown block in close proximity and parallel to the fault plane. Morrow sandstones were later deposited in stream channels that formed in the drainage system. The geometry of the sandstone deposit was heavily influenced by the pre-existing fault system. The end result is a long and narrow deposit that has significant variability in thickness and reservoir quality.
The mapping of a Permian structural closure combined with regional geology lead to the discovery at depth of the Congdon Oil Field. This structural concept led to the discovery of oil in the St. Louis oolictic shoal deposit. Extension and development drilling led to the establishment of additional reserves found in stratigraphically controlled traps of the Morrow Formation. |
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