Optimizing in Four Steps Composite Lost-Circulation Pills Without Knowing Loss Zone Width

Abstract

Abstract A composite blend for controlling lost circulation has been developed on the base of a new four-step methodology. This blend exhibits superior performance over conventional treatments and eliminates missing loss-zone diagnosis and characterization. Fighting lost circulation is a costly and time-consuming process. Conventional lost-circulation treatments try minimizing excess costs from rig time and fluid loss. In addition, they try avoiding the need for additional casing. However, these treatments are often based on trial and error without any practical technique to properly diagnose and characterize the loss- zone. The new methodology addresses these shortcomings. The methodology proceeds in four steps: Dispersing a composite lost circulation material in a base fluid, Bridging the loss zone with fibers, Plugging the fiber networks, and Sustaining the plugs. Each step is parameterized by criteria, which can be optimized to meet the performance requirements. The fibers must possess certain form factor and exhibit specific physical properties to bridge open fractures after deploying through bottomhole assembly and drill bits. The composite plug also must endure pressure fluctuation during drilling or cementing and must tolerate erosion forces exerted by the fluid flow and downhole hardware. The four-step methodology provides an engineered combination of sized granules, stiff and flexible fibers. This new composite system was validated in several field trials in South America and Europe. In addition to the field trial results, this paper also describes the laboratory-scale and yard-scale tests, which were used for developing the new system. These tests helped establish guidelines for deployment through bottomhole assembly and drill bit. These examples demonstrate that the novel composite blend system improves performance and robustness in curing losses compared with conventional single-fiber systems.