Abstract

The Mangala field was discovered in 2004 in the sparsely populated, remote, undeveloped Thar Desert of NW India. Mangala is India’s largest onshore producing oilfield and its development was fast-tracked with production start-up in 2009. This paper describes the process of selection, design, testing, and implementation of specific synthetic-based drilling fluids and their advantages (technical and economic) over conventional water-based fluids.

The field development plan includes 109 production (11 horizontal) and 53 water-injection wells, all directionally drilled from wellpads. Newly-designed, mobile drilling rigs predominantly used rotary steerable systems. Synthetic-based fluids were proved appropriate for drilling all main hole sections with a drill-in fluid system custom-designed for horizontal well sections. Strict environmental requirements imposed restrictions on fluid choice, type, handling and disposal in this delicate ecosystem. Over 18 months of continuous drilling, 3 rigs have drilled 130+ wells using and reusing these muds. Rigs are fitted with Hi-G shakers using selected fine screens to ensure tightly controlled Particle Size Distribution (PSD) and drilling fluids are constantly monitored for consistent specifications. Advantages delivered by these muds include very low fluid invasion, excellent return permeability, low filter cake lift-off pressure and high ROPs. This drives drilling performance and has resulted in worldwide top-quartile benchmark ranking in the industry standard database. Planned casing installations, data acquisition and hole sections have been successfully delivered in all wells. Horizontal wells, drilled with 8.5" reservoir sections and completed open-hole with sand screens have delivered record flow rates for onshore India, up to 14,000bopd. The field is currently on production at 125,000bopd.

These custom-designed synthetic-based drilling fluids have been a major contributor to the successful drilling and completion program at Mangala. The top-quartile drilling performance has achieved significant cost savings while still delivering highly productive wells, including the longest, most productive, onshore horizontal wells in India.

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