Previous Talks

Wednesday, April 13th, 2011

Fracturing Horizontal Wells and Refracturing: The Role of Stress Reorientation

Mukul Sharma, University of Texas at Austin

Abstract

Horizontal wells with multiple fractures are now commonly used in unconventional (low permeability) gas reservoirs. The spacing between perforations and the number and orientation of transverse fractures all have a major impact on well production.

Our results demonstrate that a transverse fracture initiated from a horizontal well may deviate away from the previous fracture. The effect of the reservoir’s mechanical properties on the spatial extent of stress reorientation caused by an opened crack has been quantified. It is shown that stress interference, or reorientation, increases with the number of fractures created and also depends on the sequence of fracturing. Three fracturing sequences are investigated for a typical field case in the Barnett shale: (a) consecutive fracturing, (b) alternate fracturing and (c) simultaneous fracturing of adjacent wells. The numerical calculation of the fracture spacing required to avoid fracture deviation during propagation, for all three fracturing techniques, demonstrate the potential advantages of alternate fracture sequencing and zipper-fracs to improve the performance of stimulation treatments in horizontal wells.

The production or injection of fluids in reservoirs results in a redistribution of stresses. The extent of stress reorientation has been calculated for fractured production and injection wells and the results have been analyzed for their impact on refracturing operations. Rules of thumb and charts have been provided to help candidate well selection for refracturing based on the study.

Speaker Biography

Mukul M. Sharma is Professor and holds the “Tex” Moncrief Chair in the Department of Petroleum and Geosystems Engineering at the University of Texas at Austin where he has been for the past 26 years. He served as Chairman of the Department from 2001 to 2005. His current research interests include injection water management, hydraulic fracturing, formation damage and improved oil recovery. He has published more than 250 journal articles and conference proceedings and has 12 patents. Sharma has a bachelor of technology in chemical engineering from the Indian Institute of Technology and an MS and PhD in chemical and petroleum engineering from the University of Southern California.

Among his many awards, Dr. Sharma is the recipient of the 2009 Lucas Gold Medal, the 2004 SPE Faculty Distinguished Achievement Award, the 2002 Lester C. Uren Award and the 1998 SPE Formation Evaluation Award. He served as an SPE Distinguished Lecturer in 2002, has served on the Editorial Boards of many journals, and taught and consulted for industry worldwide.