Lessons Learned from the First Cement-In Fiber of Carbonate Gas Formation in Ordos Basin During Hydraulic Fracturing

Abstract With the help of horizontal drilling and multistage hydraulic fracturing, carbonate gas proved to be another valuable unconventional resource in Ordos basin. This paper was to introduce the lessons learned from the pilot project that mapping frac with permanent cemented fiber, try to help decision maker to evaluate the capability of distributed acoustic sensing and distributed temperature sensing (DAS/DTS) for carbonate gas wells, gain immediate subsurface insights from real time deliverables and eventually guide the direction to optimize completion strategy for further development. From planning to execution, we reviewed the key factors to assure the success of the project. In conjunction with treatment data, real time fiber optical based DAS/DTS results were used for cluster level fluid and proppant allocation, inter-stage communication identification, and effectiveness evaluation of on-the-fly intervention measures. Dynamic calculation of uniformity index was also applied and investigated to compare different kind of perforation distribution. According to the robust results from fiber, abnormalities during frac treatment were identified timely, some field trials were conducted onsite, and main direction of further work were settled aiming to improve current situation. The dedicated planning from drilling to completion contributed to the success of the whole project. DAS/DTS proved to be an effective diagnostic tool to visualize in-well subsurface activities for carbonate gas wells, not only can help to determine real time fluid and proppant flow distribution, but also can assist to identify inter-stage communication events sensitively. Also, several trials to improve isolation were conducted onsite and the effectiveness were assessed in real time. According to the clear real time results from fiber, current completion design especially perforation strategy deserves reconsideration and further optimization. Different from developing other resources, the pre-treatment acid was critical to hydraulic fracturing of carbonate rocks in Ordos basin, but from the DAS/DTS results of this project, consequences of this necessary step could be detrimental to target better uniformity if without proper design, heel-ward fracture prone to be dominant to propagate despite location where fracture initiated at the beginning. With the help of in-well fiber, pumping schedule were successfully optimized on the fly and achieved better outcomes compared to original design. Several follow-up actions were settled for further development based on the comprehensive study in this project. This paper reviewed the lessons learned from the first trial well of carbonate formation to mapping hydraulic fracturing with cemented fiber in Ordos basin, real time deliverables from DAS/DTS broadened the toolbox of decision maker to gain immediate subsurface insights and comprehensively evaluate current completion designs. The rich results and unique fracture propagation feature discovered may trigger better top-level design for future project and drive development of carbonate gas formation in Ordos basin to higher level.