Abstract
A field development located offshore Peninsular Malaysia targets the northern Malay Basin oil-bearing sandstone reservoir. However, the reservoir shows reduced pore pressure due to hydrocarbon depletion, which is naturally coupled with a decreased fracture gradient. In addition to geomechanics constraints, the well design involves highly deviated and Extended Reach Drilling (ERD) wells aimed at reaching untapped hydrocarbon reserves. The abnormal pressure regime and the typical constraints of highly deviated and ERD wells demand an innovative well design that incorporates a two-pronged approach to control Equivalent Circulating Density (ECD) as well as hole stability issues due to severe depletion. One of the strategies adopted was the design of a Low ECD Non-Aqueous Drilling Fluid (Low ECD NADF) aimed at reducing ECD while drilling without sacrificing optimal hole cleaning ability. Additionally, the specially designed Low ECD NADF was treated with Wellbore Strengthening Material (WBSM) to penetrate the severely depleted reservoir section. This specially-designed drilling fluid proved successful in both controlling ECD and increasing wellbore hoop stress across the depleted sands, preventing losses during drilling, casing running, and cement operations. The paper outlines the geomechanical data analysis guiding the WBSM design, computer-assisted predictions of hydraulically induced rock fractures using dedicated software for dynamically induced fracture size prediction, and laboratory testing iterations refining the WBSM package. Field application of the Low ECD NADF system included the use of Permeability Plugging Test (PPT) and Particle Size Distribution (PSD) analyses. Additionally, surface solids control equipment manipulation, including strategic shale shaker control, allowed the maintenance of WBSM treatment at optimal fracture pluggability at a minimum cost throughout the drilling of the depleted zone.