Value of Cement Bond Logs for Evaluation and Improvement of Cementing Practices in Extended Reach Drilling ERD Wells

Abstract

This paper discusses the value of cement logs as the core input to analyze the cement quality and validate the improvements made to cementing designs and practices of the intermediate casing string in Extended-Reach Drilling (ERD) wells. The ERD wells are being drilled from artificial islands in a field offshore in the UAE. The primary cementing objectives are isolating the reservoirs from their sublayers and protecting the casing against possible future corrosion across an upper formation. Cementing challenges include higher angle deviation, higher mud weight requirements resulting from an anisotropic, unstable shale formation present above the reservoir section. Effective reservoir management requires sound zonal isolation to eliminate crossflow between different reservoir units. In combination with standard cement bond logs (CBL), ultrasonic technology has provided detailed information about cement quality and a qualitative indication of casing position in the borehole. These have also led to valuable insight into how continued cementing designs and practices improved zonal isolation. Improvements in cement quality seen as a result of enhanced casing centralization, optimized hydraulic model, modified cement rheology, displacement rate impact, among others, were confirmed with the cement log evaluation program. The paper will present the ultrasonic and standard CBL responses, which support the enhancements made to the cementing design and practices that yield the desired results. The cement quality has been improved in the ERD wells intermediate section through strategic modification in cementing practices. Cement evaluation logs have played a significant role in validating the cementing methods’ development. Consistently improved zonal isolation results have opened up the opportunity for future efficiency gains by eliminating routine CBL.