Compiled and edited by Thomas C. Chidsey, Jr., 173 p., 11 appendices
The Pennsylvanian Paradox Formation is the major producer of oil and gas in the Paradox Basin of southeastern Utah and southwestern Colorado. The Paradox Formation was deposited in a warm, shallow-shelf marine environment and contains a wide variety of carbonate lithofacies. Traps are stratigraphic formed by carbonate buildups consisting principally of phylloid-algal deposits sealed by organic-rich shale. Diagenesis is dominated by dolomitization, which produced extensive “micro-boxwork” porosity and microporosity. The resulting complex reservoir heterogeneity has created multiple intervals that represent untested targets for horizontal drilling, which has only been extensively used in the giant Greater Aneth field, Utah’s largest, but not in the more typical small fields of the Paradox Basin.
This 173-page Utah Geological Survey Bulletin covers research and results of a Utah Geological Survey study to (1) increase recovery and reserve base by identifying untapped compartments created by reservoir heterogeneity, (2) prevent abandonment of numerous small fields, (3) increase deliverability by horizontal drilling, (4) identify reservoir trends for field extension drilling and stimulating exploration in Paradox Basin fairways, (5) reduce development costs, (6) minimize surface disturbance when drilling, (7) use energy investment dollars more productively, and (8) increase royalty income to the various stakeholders. This Bulletin consists of three components: (1) regional lithofacies evaluation of the Ismay and Desert Creek zones of the Paradox Formation in the Blanding sub-basin, (2) case studies of Bug and Cherokee fields, and (3) horizontal drilling opportunities. Appendices include detailed maps, cross sections, core and thin section descriptions and photographs, porosity/permeability crossplots, scanning electron microscopy, epifluorescence and cathodoluminescence petrography, and capillary pressure/mercury injection analysis.
The research, data, conclusions, and recommendations contained in this Bulletin are anticipated to be a valuable resource for hydrocarbon production and exploration in the Paradox Basin and similar shallow-shelf marine regions worldwide, as well as for students and researchers studying carbonate rocks for years to come.