Evaluation and Early Performance of Fishbones Drilling and Completion Technology in a Layered Heavy-Oil Sandstone Reservoir: A Case Study from the Bikaner–Nagaur Basin, India

Abstract

This paper evaluates the impact of Fishbones drilling and completion technology on reservoir contact and early production performance in a thin, vertically compartmentalized heavy-oil sandstone reservoir. The scope includes technology selection, execution considerations, and quantitative assessment of cold-production response relative to conventional horizontal wells, providing a benchmark for evaluating incremental gains from future thermal stimulation. A horizontal well (D3) was drilled and completed with Fishbones drilling and completion technology in the Infracambrian Jodhpur Formation containing heavy oil (17.6°API) in the Bikaner-Nagaur Basin, India. A structured evaluation workflow was implemented, including formation drillability testing on representative core samples, single-well 3D numerical simulation to optimize subassemblies spacing and completion length, pressure-drop estimation, and full-wellbore hydraulic modelling to define deployment parameters. Laboratory testing of magnesium-based dissolvable turbine materials was conducted to ensure post-installation wellbore access. The completion incorporated twelve Fishbones subassemblies, followed by controlled activation, turbine dissolution, fishbones laterals cleanout and initiation of cold production. Early performance was evaluated over a 120-day cold-production period and compared with three offset horizontal wells (A, B and C) completed without Fishbones technology. To enable consistent comparison, production rates were normalized by effective reservoir contact length, accounting for differences in horizontal drain length and exclusion of non-reservoir intervals. The Fishbones-completed well exhibited approximately two- to three-fold higher normalized oil production relative to offset wells, despite partial cleanout of the laterals and absence of thermal stimulation. Operational results showed that lateral extension and cleanout efficiency were affected by how close the wellbore was to basement rocks, highlighting the need for careful trajectory placement and drillability checks in thin reservoirs. The results demonstrate that enhanced reservoir connectivity alone can deliver measurable productivity gains in low-mobility, layered heavy-oil reservoirs. Establishing this cold-production baseline provides a sound reference for subsequent evaluation of thermal recovery performance and supports broader application of reservoir-contact-enhancement completions in similar reservoir settings. This paper presents a documented field case history of Fishbones drilling and completion technology applied in a vertically compartmentalized heavy-oil sandstone reservoir prior to thermal stimulation, an area with limited published case histories. The work provides practical insights into completion design, performance normalization, and operational risks, offering transferable guidance for engineers developing heterogeneous heavy-oil reservoirs where conventional horizontal wells provide limited drainage.