Reservoir simulation of primary production in the Zenith Field, Stafford and Reno Counties in Kansas

Abstract

The Zenith Field is a large reservoir with production coming from four formations, namely 1) Misener Limestone, 2) Misener Sandstone, 3) Maquoketa Dolomite, and 4) Viola Limestone. Initial oil in place was estimated to be 100 million barrels. Recovery from primary production was approximately 20 million barrels, with an additional one million barrels recovered through waterflooding. A large quantity of mobile oil is believed to still exist in the field.

The purpose of this project was to simulate primary recovery in the Zenith Field using a mathematical reservoir model. Limited data were available for the simulation and included formation thicknesses, porosity measurements, a single PVT analysis, four core reports, and production history of the field. The complex geology and fluid flow in the field involved communication between formations, the presence of an aquifer, and indications of natural fractures in the carbonate formations. The long production history and the lack of data also added to the challenge of simulating the behavior of this field.

Grids for each formation were input into the model along with available rock and fluid properties. Where no data were available, correlations were used. The best data were available for the Misener formations, and a match of actual field pressures, water cuts, and field gas-oil ratio was obtained for the initial two years of production from the Misener formations. It was discovered through the simulation that the Maquoketa and Viola contributed to production during these first two years, even though these formations had not been discovered at the time.

A history match of the remaining primary production was not achieved due to the limited amount of data available. Data not available that would have helped in the simulation were more core reports, additional field tests, and production data (pressures, oil, gas, and water) on individual wells. It is recommended from this work that if an attempt to simulate a field as large as the Zenith Field is made in the future, there should be much more data than that which was available for the Zenith Field.