Quantitative Analysis of the Effect of Perforation Interaction on Perforation Stability Using the Finite Element Method

Abstract

Summary Oil and gas reservoirs are normally completed as either openhole or perforated wells. Although a perforated well has hundreds of perforations, a single perforation is normally used for perforation interaction analysis, assuming the perforations are shot symmetrically and the stress state around a perforation is symmetric in both vertical and horizontal directions. However, for the single/double spiral perforations shot in inclined wells, no vertical and horizontal symmetry surfaces exist. The required elements for a multiperforation model are more than 10,000, which results in complex mesh generation and long computation time. In this study, we investigate perforation interaction to find the optimal perforation design that yields the highest productivity while maintaining mechanical stability. The practical implications of this work to the field are (1) the drawdown to cause perforation instability for gas flow is significantly less than oil flow. Therefore, when the gas flow becomes dominant either by enhanced oil recovery with CO2 or by low bottomhole flowing pressure below bubblepoint, the drawdown should be reduced to avoid sand production. (2) For inclined wells, the X-shaped staggered orientation perforations are the best pattern to delay onset of sand production without significantly reducing the well productivity. (3) For near-vertical wells, the conventional nonstaggered perforation pattern delays the onset of sand production due to the stress reduction in the vertical direction compared with the commonly used staggered perforation patterns.