Historically, the conventional approach to well production has been to produce continuously, minimizing interruptions to flow insofar as possible. Yet some operators have observed improved well flow rates and ultimate recovery after a significant well shut-in periods. These production increases have not been documented. This study investigates the production impact of cyclic production/shut-in on fractured vertical and horizontal gas well performance.
A numerical reservoir model in Stimplan software was used to model production in fracture stimulated vertical and horizontal gas wells. Reservoir permeability is varied over a range of 0.0001 md to 1 md, and the shut-in period was varied from 0 percent to 100 percent. Results of the simulations are presented as normalized recovery versus shut-in time, where normalized recovery is defined as cumulative production from any simulation case divided by the cumulative production of 0 percent shut-in case.
Results of 120 simulation cases showed that there is an improvement in production in fractured horizontal gas well reservoirs. In vertical gas well reservoirs with permeability greater than 0.001 md, the normalized recovery did not decline significantly with increase in shut-in period. This result shows that cyclic production/shut-in strategy is beneficial in horizontal gas wells and it is not detrimental in vertical gas well reservoirs with permeability greater than 0.001 md.
This study helps to identify the optimum shut-in period required to maximize the production in horizontal gas well reservoirs. In a vertical gas well, cyclic production/shut-in strategy can be used in reservoirs above 0.001 md permeability without significant loss in production --Abstract, page iii
