ABSTRACT: Cypress Reservoir and its Recovery Potential at Xenia East Oil Field, Illinois Basin

XU, JIANZHONG, Illinois State Geological Survey, Champaign, IL

Xenia East field, located in Clay County, Illinois, was discovered in 1951. This field has produced about one million bbl of oil from five pay zones. About half of the total comes from the Cypress Formation (Mississippian), which stopped producing in 1978 due to exhaustion of primary energy drive.

Log correlations and geological analysis show that the Cypress pool is predominantly a structural trap; the reservoirs are interpreted as marine bar sandstones. Thin section petrography and SEMIEDX study show that the major porosity is intergranular and pores created by feldspar dissolution have enhanced the permeability. Silica as quartz overgrowths is the most common type of cement. The clay mineralogy, determined by XRD analyses, consists of kaolinite, chlorite, illite, and mixed-layered clay. Clay content reduces reservoir permeability. The oil saturation, as determined from E-log interpretation, ranges from 40 to 72%. Original oil in place (OOIP) is estimated to be two million bbl by volumetric and the Monte Carlo methods. There is good potential for improved oil recovery from th Cypress pool because about 75% of OOIP remains and the reservoir has not undergone waterflooding.

AAPG Search and Discovery Article #91013©1992 AAPG Eastern Section Meeting, Champaign, Illinois, September 20-22, 1992 (2009)