Thirty Years of Gas-Shale Fracturing: What Have We Learned?

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 133456, ’Thirty Years of Gas-Shale Fracturing: What Have We Learned?’ by George E. King, SPE, Apache Corporation, prepared for the 2010 SPE Annual Technical Conference and Exhibition, Florence, Italy, 19-22 September. The paper has not been peer reviewed. Although high gas-flow rates from shales are a relatively recent phenomenon, the knowledge bases of shale-specific well completions and fracturing and shale-well operations have been growing for more than 3 decades, and shale-gas has been produced for more than 190 years. During the last decade, projected recovery of shale gas in place (GIP) has increased from approximately 2% to estimates of 50%, mainly through development and adaptation of technologies to fit shale-gas developments. This work surveyed more than 350 shale completion, fracturing, and operations publications, linking geosciences and engineering information together to relay learnings that will identify both intriguing information on selective opening and stabilizing of microfracture systems within the shales and new fields of endeavor needed to achieve the next level of shale-development advancement.    Introduction The first lessons from this study were: No two shales are alike. Shales vary areally and vertically within a trend, even along the wellbore. Shale “fabric” differences, combined with in-situ stresses and geologic changes, often are sufficient to require stimulation changes within a single well to obtain best recovery. Understanding and predicting shale-well performance require identification of a critical data set that must be collected to enable optimization of the completion and stimulation design. There are no optimum, one-size-fits-all completion or stimulation designs for shale wells. Although gas-shale-completions literature is developing rapidly, the history of gas-shale research offers a starting point that can help explain many phenomena seen in shales worldwide. Of the more than 350 references reviewed for this report and the 250 included, more than 60% date from 2007 or later, and learnings are increasing rapidly. The full-length paper seeks to define many of these advances and associates the references. This work is not about any single shale; rather, it focuses on characteristics within shale that can be addressed with completion, stimulation, and production technology to create opportunities for increasing gas recovery. The objective of this paper was to compile, explain, and link as much usable information as possible on the topics of completion, fracturing, and production behaviors.