Using a Land Rig in an Offshore Location: Some Lessons from a Niger-Delta Experience

Abstract

Abstract In line with national aspiration to increase hydrocarbon reserves and production rate, the last 18 years have witnessed the award of licenses for the development of about 30 marginal fields in the Niger Delta. However, only nine of these green fields have come on-stream to date, while others are at different stages of development, including inactivity. Among multiple reasons, this disappointing performance has been attributed to the combination of high development costs and paucity of funds. With rig rate as the main culprit, drilling/completion typically accounts for 60-70% of development costs. One strategy to lower the commerciality barrier of marginal fields is to address rig costs, without compromising safety and other performance indicators. This paper presents a case study on the unusual, but successful, deployment of a land rig in a swamp-located marginal field (5-ft water depth) in the Niger Delta. To save about 70% on rig rate, a land rig was evaluated and used in preference to a swamp rig to develop this oil field, which was hitherto stranded. Employing rigorous multidisciplinary technical evaluations, this feat was accomplished by constructing a fit-for-purpose platform using a reinforced 18-5/8″ casing, thick metallic sheets and 20mm H-beams. The design and execution entailed several considerations, including rig positioning, corrosion risks, and drilling dynamics to total depth (9400ft MD). To enable this first successful use of a land rig in a Niger-Delta swamp, subsequent hydrocarbon production, evacuation and storage were considered. The planning and execution of the drilling and completions aspect of this project are described, focusing on the success, challenges, and lessons learnt. Among other lessons, the engineering and operational tactics behind the rig placement are highlighted. These insights should be of significant value to other operators of marginal fields in the Niger Delta, and elsewhere.