Eastern Section Meeting

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Implementing Discriminative Water Saturation Criteria to Determine Prime Production Remnants in Morrow County

Abstract

The Morrow Consolidated Oil Field was analyzed as a part of a project examining the technical and economic feasibility of CO2 utilization and storage in Ohio. The Morrow Field produces from the Copper Ridge Dolomite, also known as the Trempealeau Formation. After deposition of the Trempealeau, the area underwent large scale erosion, leaving behind remnants that become encased in the Wells Creek Shale. These remnants are irregular in size and distribution and serve as the primary reservoir for the field. Historically, these remnants have been difficult to identify. We present a method for identifying remnants including those with high production potential.

In total, 74 wells from the northeast portion of the field were analyzed for net to gross, porosity and water saturation using Gamma Ray, Resistivity, Neutron Porosity and Bulk Density wireline logs. Many of the wells in the study area did not penetrate the entire Trempealeau Formation; instead drilling was terminated between 50 and 100 feet from

the top. As such, a water saturation (Sw) cutoff criterion was identified to establish the bottom of the reservoir for uniform calculation purposes. When applied to the cross sections created for the field, the Sw cutoff helped distinguish between “elevated” remnants and non-remnants in study area. Additionally, good correlation exists between remnants identified with the water saturation cutoff and production data. Mapping the wells that met the water saturation cut off yielded a remnant map for the study area without the use of field wide seismic data.