Cairn Energy India Private Limited (CEIL) started development in Mangala field with aggressive target of drilling 60-70 wells/year (7days/well). Therefore, the focus was to reach high drilling efficiency which will ultimately reduce the well cost. Some of the challenges faced were placing wells in greatly faulted zones, high uncertainty in shallow TVD reservoir, requirement of tangent for installation of ESP, smooth hole to avoid problem running screen and collision risk due to closely spaced wells. RSS was generally used only in complex, high-cost offshore projects where the savings realized were significant. The industry has been slower to adopt the use of RSS for onshore directional drilling applications however CEIL took a step ahead by deploying RSS for Mangala field development. RSS was utilized in directional wells to optimize drilling performance and deliver smoother hole profile. Advanced LWD services such as bed boundary detection tool along with RSS have brought value in successful landing and placement of horizontal wells in the best reservoir strata. Application of near-bit gamma ray and other LWD measurements to identify the top of reservoir as early as possible has helped to avoid the requirement of drilling pilot holes. This paper discusses such application in detail and presents its benefits.

The result was a noticeable improvement in well delivery time, reduced drilling cost, and improved hole quality. This paper compares the drilling performances with PDM vs RSS in the same field and presents the lessons learnt in the process of field development. RSS delivered less tortuous hole which result in a problem-free liner or screen run. Hole cleaning was improved which allowed to drill at faster ROP without taking risk of well complication. Time versus Depth analysis clearly indicated that RSS was both technically and economically, a sound approach for drilling the wells in Mangala field. This paper showcases a case study where RSS application proven to be cost-effective solution even in low-margin onshore field development.

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