This paper presents a comprehensive field study of an openhole completion with standalone screens using a unique filtercake breaker treatment, compatibility with reservoir fluids, cost effectiveness, and overall performance-based comparative results to meet the challenges of drilling and completing offshore wells.
In the offshore field of Krishna-Godavari Basin, Bay of Bengal, one of the most prolific hydrocarbon basins of India, synthetic-based reservoir drill-in fluids (SB-RDFs) were used to drill the reservoir section, which was then completed openhole using standalone sand-control screens. In order to control fluid invasion to the formation, a major cause of formation damage, the designed RDF created a filtercake at the sandface. However, high flow initiation pressure caused high skin effect and compromised completion efficiency. The primary challenge during completion was to clean up the SB- RDF filtercake from the reservoir section to remove near-wellbore damage and maximize productivity. Another challenge was to avoid the high potential of filtercake plugging of the screens, which could lead to higher drawdown pressures and possible early screen failure. To address these challenges, a filtercake breaker for the SB-RDF was developed to lower the skin factor thus maximizing production and mitigating the risks of plugging the sand-control screens. After implementing this customized breaker solution, combined with a precise placement program, the wells showed a tremendous reduction in the skin factor and a significant increase in completion efficiency, compared to wells with the same reservoir properties completed in earlier campaigns.
An organic acid pre-cursor enabled filtercake breaker placement and soaking without being chemically spent during circulation. Additional breaker design criteria included the ability to break the RDF emulsion, water-wet the solids in the filtercake, dissolve the calcium carbonate used as bridging material in the SB-RDF, and disperse the non-acid soluble material without plugging the screens.
The paper presents a detailed study of the main challenges while formulating and evaluating the filtercake breaker solution. Additionally, a production results comparison is made between the well using the customized filtercake breaker treatment and previous well completion and breaker treatments. The paper also discusses the comprehensive displacement program and required spacers for precise placement of the breaker in the openhole and offshore pit management.