The paper presents a case study on adopting an economics driven novel approach to directional well planning and drilling a horizontal well in a single well FDP (field development plan) for a marginal field in onshore India. The paper highlights the successful drilling of 8-1/2″ landing production section with DLS > 7 deg/30m followed by the 8-1/2″ horizontal lateral. The feasibility of achieving high DLS well trajectory using basic directional tools and associated hole problems with their mitigations are addressed in the paper.
Low crude price resulted in marginal economics for the above FDP. To improve economics, the capital expenditure had to be minimized (by utilizing existing well pads and production facilities) and maximize oil production (by drilling horizontal wells). Hence, constrained surface locations and fixed subsurface targets resulted in complex well trajectory (DLS>7). The Trajectory was finalized after multiple iterations to ensure that it is meeting requirements of deep set artificial lift, free of collision threats and also meeting the geological objective of placing the well in a thin reservoir with defined GOC and OWC. The final well design included one 12 ¼″ surface section with 9-5/8″ casing and 8-1/2″ production hole with 7″ casing to TD (~1800m MD). The well was initially planned with special RSS tool which could achieve high DLS, but the cost and lead time were the contra-indicators. Hence, the 8-1/2″ hole was planned with two BHAs. The build and land section was planned with motor (1.6 deg bend and rpm limitations) and tricone bit BHA to build from 9 deg to 90 deg inclination with a DLS of 7 deg/30m in 400m closure. The horizontal lateral was planned with RSS BHA and PDC bit including density image LWD for geosteering. To minimize hole sections for cost reduction, the landing and horizontal section was combined in a single hole which increased risk associated with wellbore stability, hole cleaning and casing running. The risks were suitably addressed through in-house geo-mechanics inputs, application of ERD procedures & real time T&D monitoring
With no offset well data (in onshore India) to substantiate the possibility of achieving high DLS trajectory, the motor and tricone bit BHA successfully achieved the desired trajectory with max DLS ~11deg/30m and without any hole problems. The well was successfully landed and placed in the reservoir. The operator gained significant confidence in understanding of drilling high DLS wells without expensive drilling tools