Abstract: Rock-Mechanical Model of Thin-Bedded Sands and Shales for Improved Hydraulic Fracture Prediction

PANTOJA, DAVID, Colorado School of Mines, Dept. of Petroleum Engineering and Dept. of Geology, Golden, CO

Models which predict hydrofracture heights generally use bulk rock properties produced from conventional, low-resolution formation evaluation tools. Because of this, hydrofracture heights are commonly overestimated in thin-bedded units because they do not take into account the ability of thin shales to stop fracture propagation.

This project is an attempt to overcome that problem by using detailed core measurements from North LaBarge field, Green River Basin, Wyoming. In this field, rocks of the Cretaceous Mesaverde Formation produce oil and gas from low permeability, thin-bedded (1-25 cm) fluvial-deltaic sands and shales.

Shear and compressional velocities and probe permeabilities have been measured on roughly 100 ft of core at very high resolution, every 0.5 inches. Pressurized core plugs have been measured for p and s wave velocities to help calibrate data to subsurface conditions. Laboratory results have been calibrated to a full-waveform sonic log and borehole images, resulting in a corebased rock-mechanical model. This model provides in-situ rock-strength information in a thin-bed context. The plan is to use this enhanced model in a computer simulator to better design and predict the fracture propagation within the formation. It should be possible to extrapolate the method to uncored wells.

AAPG Search and Discovery Article #90931©1998 AAPG Foundation Grants-in-Aid