Maximizing Efficiency in Haynesville Restimulations: A Case Study in Improving Lateral Coverage to Maximize Incremental Gas Recovery

摘要

The interest in restimulating unconventional wells in recent years has been driven by multiple factors—the desire to arrest the steep decline curves of unconventional wells, the depressed prices for both oil and natural gas, and the optimization efforts to fully drain reservoir rock that might have been inefficiently stimulated during original completions. Numerous publications have documented that a restimulation treatment can either add to the estimated ultimate recovery (EUR) of a well or accelerate the recovery rate of that well's EUR. Efforts are now focused on making restimulation treatments more effective with more repeatable results. Early diagnostic methods have shown that in some horizontal restimulation treatments, the majority of the fluid and proppant pumped are delivered only into the first 1,000 to 2,000 ft of the lateral. These diagnostic methods include microseismic monitoring, radioactive proppant tracer, and production logging. In June 2015, one Haynesville shale well was restimulated and evaluated using radioactive proppant tracer to provide insight into the stimulation coverage of the lateral. The restimulation design for the case history well focused on treating the entire lateral with the use of a biodegradable particulate diverter. This was accomplished by increasing the amount of material per diversion cycle and by increasing the number of cycles in the restimulation treatment. Additional consideration was given to delivering an optimized proppant amount per lateral foot, ideal cluster spacing, treatment fluid selection, and appropriate treatment rate. The case history shows that 63 of the 70 clusters identified with the tracer log were stimulated during the restimulation treatment. Additionally, the clusters showing proppant were located throughout the entirety of the lateral. The size and composition of the restimulation design is analyzed with respect to treatment performance, and possible improvements are considered. The economic viability of a restimulation program should be weighed against the entire cost of a restimulation treatment, which includes wellbore preparation, wellbore integrity testing, cost of restimulation services, and other miscellaneous logistical challenges encountered before the treatment begins.