Surface Cementing Success on 18-5/8" Casing in Shallow Loss Zones Using Thixotropic Cement and Gel via Dual Units: Wafra Field Trial

Abstract Achieving cement-to-surface on large-diameter surface casing strings in mature, depleted formations remains one of the most persistent well-construction challenges. In the Wafra Oil Field (Partitioned Zone), an 18-5/8″ surface casing exhibited severe shallow losses, preventing durable isolation despite 51 prior top-up campaigns using conventional and unconventional materials. To overcome the low-pressure window and minimize static invasion into loss-conduit areas, a thixotropic cement system was engineered in conjunction with a 10 ppg gel solution and deployed via synchronized dual cementing units. The approach delivered full returns to surface during the final simultaneous pumping stage, stabilized annular pressure response, and post-job CBL confirmed cement at surface with improved near-surface bond. This paper documents the diagnostics, rheological design basis, stage-by-stage execution (including Cure Loss Plus and Quick Set Technology sequences), verification, and operational learnings. It also presents a replication checklist and discusses applicability boundaries, risk controls, and economic impact for shallow-loss wells in Wafra and comparable mature assets.