Technology Advancements in Loss Circulation (LC) Spacer Deployment Across a Narrow Pressure Window for Critical Liner Cement Jobs: Case Studies from Saudi Arabia

Abstract

A major challenge that is faced during the well construction phase is to cement the formations holding narrow pressure margins between the pore and fracture gradients without inducing losses that could compromise the integrity of the cement barrier. The paper will review two case studies for deploying an engineered loss circulation (LC) spacer system as an important solution for primary cementing operations in the case study wells with such narrow pressure margins. One of the case studies well is a land well where a high-pressure influx was encountered while drilling an 8-3/8-in hole across a water-bearing formation. A narrow pressure gradient persuaded to utilize a managed pressure drilling (MPD) system. The well was drilled to the target depth using 138 lbm/ft3 oil-based mud drilling fluid while maintaining the equivalent circulation density (ECD) from 146.5 to 149.5 lbm/ft3. A 150 lbm/ft3 slurry was designed to keep the ECD intact. Additionally, the spacer was loaded with optimum amounts of surfactant package to help remove the mud and to water-wet the formation and pipe to achieve better cement bonding. It was observed that the engineered LC spacer provided safe isolation of low fracture gradient zones cost-effectively, even in challenging narrow-pressure window scenarios. The LC Spacer was able to mitigate the loss circulation while cementing due to the utilization of ultra-low invasion technology, which created a barrier across loss circulation zones. It was also observed that the LC spacer formed a shield across formation walls and reduced the loss circulation, ranging from partial to total losses on permeable, fragile, weak formations, naturally fractured reservoirs, and depleted reservoirs. The LC spacer also improved wellbore stability and ECDs along the wellbore and expected loss zones. Ultimately, the paper concludes that LC Spacer can be designed to address the challenge of minimizing losses during the primary cement job by offering superior sealing capabilities. The case studies present an overview of the engineering process used to plan critical liner cement jobs using a specialized LC spacer system. This paper reviews the execution of two successful liner jobs and presents findings and lessons learned. After the successful results on these jobs and subsequent operations, this spacer system is now being adopted to optimize cementing, where losses during cementing operations in the past have forced the modification of well construction.