Trailblazing Unconventional Exploration: Out-of-the-Box Solutions Result in Elimination of NPT and Faster Delivery of Challenging Unconventional Horizontal ERD Wells

摘要

Drilling unconventional horizontal extended reach wells has always been challenging; coupled with geological and drilling challenges of an exploratory field, they present the perfect combination for non- productive time (NPT). To maximize production, it is paramount to reach the whole reservoir and extract hydrocarbon resources efficiently. Moreover, to increase profits, the well should be drilled in minimal operating time, which in turn reduces operating expenses. This paper presents a detailed study and outline of neoteric practices used to drill four such wells in an unconventional field that resulted in the elimination of NPT and reduced drilling and completion time to less than one-third. Thirteen wells have been drilled under an unconventional gas exploration project since 2007 with a historical average drilling and completion time of 95 days (and best record of 60 days). Numerous challenges associated with the field (i.e., loss of circulation, hole instability, stuck pipe, bit balling, casing held up) led to an average NPT of 40 days. To eliminate NPT and improve operational efficiency, a detailed study of the offset wells’ drilling and mud programs was conducted with the operator. After an in-depth review and analysis, a revised mud program was adopted containing a holistic approach to encounter the challenges faced in offset wells, as they were all interconnected. The use of a novel rate of penetration (ROP) enhancer and proprietary software for precise hydraulics management resulted in improved ROP, elimination of bit balling, and excellent hole cleaning. A modified bridging strategy, using software simulations validated by lab testing and changes in sweeping procedures to avoid wash out and removal of filter cake, cured losses successfully and improved overall hole condition. A totally new composition for mud mixed on location in the event of total losses and use of innovative polyamine inhibitor for reactive formations eliminated hole instability and stuck-pipe incidents. Implementing these customized solutions, combined with precise operating strategy, led to zero NPT and a reduction of average drilling and completion time to 29 days; this saved a total 245 days and an overwhelming cost savings in drilling fluid services cost for the four wells drilled to date. This paper discusses the outstanding performance achieved while using the existing setup by modifications in operational procedures and inventive techniques. It also describes cost effectiveness, overall performance-based results, and challenges while implementing the strategies. A detailed comparison of all the challenges that occurred while drilling and the proper troubleshooting steps are also discussed. Finally, the paper compares the existing results with previous drilling techniques, which may help operators with the future development of their respective fields.