Schaben field, Kansas: Improving performance in a Mississippian shallow-shelf carbonate

Schaben field (Kansas), located along the northeastern shelf of the Hugoton embayment, produces from Mississippian carbonates in erosional highs immed iately beneath a regional unconformity. Production comes from depths of aro und 4400 ft (1342 m) in partially dolomitized shelf deposits. A detailed re servoir characterization/simulation study, recently performed as part of a Department of Energy Reservoir Class Oil Field Demonstration Project, has l ed to important revision in explanations for observed patterns of productio n. Cores recovered from three new data wells identify three main facies: sp icule-rich wackestone-packstone, echinoderm wackestone/packstone/grainstone , and dolomitic mudstone-wackestone. Reservoir quality is highest in spicul e-rich wackestone/packstones but is subject to a very high degree of vertic al heterogeneity due to facies interbedding, silicification, and variable n atural fracturing. The oil reservoir is underlain by an active aquifer, whi ch helps maintain reservoir pressure but supports significant water product ion. Reservoir simulation, using public-domain, PC-based software, suggests that infill drilling is an efficient approach to enhanced recovery. Recent drilling directed by simulation results has shown considerable success in improving field production rates. Results from the Schaben field demonstrat ion project are likely to have wide application for independent oil and exp loration companies in western Kansas.