Sandeep Ramakrishna

Comparison of Magnetic Resonance Bin Distribution Permeability to Observed Production

The Granite Wash formation in Oklahoma is made up of arkosic detrital material resting on older Precambrian rocks. It can range in age from Precambrian to Middle Pennsylvanian. Formed by erosion of uplifted segments, it is generally granitic in nature and it may also include large areas of reworked carbonate. This wash presents a very difficult log interpretation problem since reservoir consistency varies greatly from well to well.

Drilling Process Creates Data Issues Requiring Innovative Data-Gathering and -Interpretation Techniques

The Lower Pennsylvanian Morrow sands and the Lower Pennsylvanian/Upper Mississippian Springer Group are the primary objectives of the recent directional drilling in the Cement Field of Caddo and Grady counties of southern Oklahoma. These marine sands were deposited in the Anadarko Basin and then were subsequently deformed by multiple stages of Pennsylvanian wrench and compressional tectonics. The resulting formations are often found to be steeply dipping to overturned and highly faulted. These reservoirs are deep and generally not extensive in nature. High energy deposition has created discontinuous flow paths, causing compartmentalization (Figure 1) and inconsistent productive capacities. The compartmentalization creates the need to target relatively small reservoir targets and requires precise bottom-hole locations to accomplish economic production. Directional drilling with down-hole motors, bent subs, stabilizers and diamond bits is the only technique that could consistently achieve these precise bottom-hole locations. In addition, there is another complication created by the almost vertical nature of the reservoir. Figure 2 is a surface outcrop that allows some visualization of the reservoir down hole. The drilling process, in many situations, was required to drill almost directly down these horizontal striations that have become vertical through subsequent earth movement. Operational Challenge The complex nature of the reservoir and subsequent deformation required directional drilling. In general, these bottom-hole assemblies required a rotary motor at the end of the drill string with a configuration similar to that exhibited in Figure 3. This assembly has a stationary reference stabilizer with hardware between the stabilizer and bit to minimize the range of movement of the bit. Even in the best conditions, this range of movement provides an area of movement that always drills a well bore larger than the bit size. This drilling process also created Copyright