Self-Degradable Particles Mitigate Communication Between Stages in Multistage Acid Fracturing Completion

Abstract

Abstract Openhole multistage fracturing (OH MSF) completions consisting of openhole packers and ball-activated sleeves have become common to maximize reservoir contact in carbonate formations in Saudi Arabia. However, multiple cases have experienced communication between stages while performing acid fracturing treatments, caused by leaks at the openhole isolation packers. Consequently, sizeable portions of the target reservoir remain unstimulated. The loss of isolation between stages can be detected during ball landing, followed by an injection test in the subsequent zone. When treating pressure remains essentially the same as before, and after landing the stage ball, the treating fluid is likely bypassing the openhole packer into the previously stimulated interval. To solve this problem, a small volume of fluid carrying degradable multimodal particles and fibers have been pumped at a low rate ahead of the acid fracturing treatment to stop fluid flowing behind the packers. Subsequent treating fluids are injected into the intended interval, thus evenly stimulating the entire lateral. It was observed that when the pill arrived at the leak, pressure built rapidly, indicating effective bridging of the concentrated particulate pill. The total pressure increase was evaluated to confirm the performance of the pill material and that stage isolation had been restored. Afterward, pressure behavior during the acid fracturing treatments indicated that a new fracture was created in the target openhole interval. In several cases, the pill sustained more than 5,600-psi pressure buildup to successfully plug the leaks. Also, all materials used to form the pill are fully degradable, and no damage is left in the formation. Therefore, the entire wellbore is effectively stimulated with improved reservoir contact, resulting in higher production rates and enhanced reservoir drainage. Degradable particulate diverters have been widely used in recent years as an effective way to increase stimulated rock volume by diverting at the fracturing face in the near-wellbore region. The cases described in this paper show the first application of this technology as temporary isolation to mitigate interstage communication inside the wellbore.