Old Field-New Paradigms-Stranded Gas: Major Findings of the Three-year Hugoton Study

Martin K. Dubois, Alan P. Byrnes, Saibal Bhattacharya, Geoffrey C. Bohling, and John H. Doveton. Kansas Geological Survey, 1930 Constant Avenue, Lawrence, KS 66047  [email protected]

The industry-state-sponsored Hugoton project results have significant implications for management of the mature field. A 108-million cell, 10,000-mi² (26,000-km²), 3-D geomodel of geologic and petrophysical properties provides new understanding of the giant reservoir, which has produced 35-trillion cubic feet (Tcf) of gas in Kansas and Oklahoma from 12,000 wells. Volumetric and flow-simulation analyses, integrated with interval-pressure tests, indicate this tight-gas carbonate system has undergone differential depletion among intervals. Reservoir and hydraulic fracture modeling provides evidence for vertical communication between the Chase and Council Grove reservoirs. Analyses indicate a limited role for natural fractures at the well scale but may indicate regional vertical communication through large-scale fracture systems tied to basement faulting. Reservoir storage and flow units are laterally extensive, a result of broad lithofacies belts migrating across a low-relief shelf in response to rapid sea-level fluctuation. Water-saturation determination from wire-line logs is problematic due to filtrate invasion during drilling. Petrophysical properties, including water saturation, vary among lithofacies and, therefore, an accurate lithofacies model is essential for reservoir modeling and management. Most of the remaining 15Ð19 Tcf gas is in lower-permeability zones of the lower Chase and upper Council Grove Groups. Production may be economically sustained beyond 2050; however, lower-permeability zones are not effectively depleted with present wellbore and hydraulic-fracture geometries. The cellular model is being used by operators to capitalize on project findings and to consider the use of alternative fracture techniques and deviated wells to enhance recovery from low-permeability zones is being investigated.