Low-Solids-Shear Dependent Cement System Eliminates Loss Circulation in the Upper Spraberry Formation in the Permian Basin: A Case History

摘要

Lost circulation is a recurring challenge and high-cost event within the oil industry, particularly in depleted or weak fracture-gradient zones. Lost circulation can significantly increase operational costs, nonproductive time (NPT), the possibility of stuck pipe, and, in some cases, can result in well loss. Lost circulation can be defined in a variety of ways, ranging from partial to total losses in a variety of formations, including highly permeable, fractured, or cavernous formations. In cases of total losses, conventional lost circulation material (LCM), such as gel-based and large-particulate-laden fluid, can be ineffective when it is unable to isolate the flow zones. The fluid system discussed in this paper uses a low-solids shear dependent cement (LSSDC) system that will remain fluid until the system begins to lose shear rate to remediate loss circulation. As the fluid system enters the loss zones and the shear rate is reduced, rapid gel strength development occurs. The cement system will become pumpable again, for a few cycles, if shear is reapplied within a specified time frame. After the shear rate has been sufficiently reduced to enable the gel strength to develop, rapid compressive strength development ensues. This development enables the isolation of cavernous or vugular formations that could have partial or total losses. The rapid compressive strength development enables drilling to proceed within a relatively short amount of time as the hydrated cement is capable of withstanding circulation pressure. Drilling through the Upper Spraberry formation, located between 6,500 and 8,500 ft in the Permian basin, represents a drilling challenge because of lost circulation difficulties. Traditional treatments to reduce the lost circulation issues include cement plug operations and mud sweeps with LCM, but none have established a consistent lost circulation resolution. For this case, the producing company prepared 100 bbl of mud sweep containing fibers, mica, and nut fines as LCM. However, total losses continued with no improvement as the LCM sweep was pumped. A total of 42 bbl of the LSSDC was then pumped; operations proceeded successfully, and the well was drilled with no other lost circulation problems. The fluid system presented remediates lost circulation through a mechanism that, unlike any fluid system within the oil industry, develops rapid compressive strengths after it is placed to withstand circulation pressures and to enable drilling to continue.