During the past three years, Marathon has utilized a variety of "high energy" stimulation techniques on approximately 150 wells to enhance near-wellbore conductivity. The majority of these high energy stimulation treatments have been conducted in naturally fractured limestone and sandstone intervals. A number of specialized tools to improve field operations have also been developed. The high energy stimulations utilize pressurized gas (usually nitrogen), to inject various fluid systems into the formation. These fluid systems have included clear liquids (such as acids and alcohols) and fluids containing proppants to scour and prop the created fractures. High viscosity fluids containing proppants were overbalance surged into the formation in some applications. A tubing conveyed perforating (TCP)/ proppant carrier system was developed, allowing release of proppant into the fluid stream at the instant of detonation. Typical overbalance surge pressure gradients are 1.5 – 2.0 psi/foot; however, some wells have been stimulated at pressure gradients in excess of six psi/foot.

The paper will also discuss the results of directional radioactive tracer logs that were run to determine the number of fracture planes created with these high energy stimulations. A listing of some recommended types of data acquisition and key operational recommendations are included in this paper.

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