Integrating Latest Logging-While-Drilling and Geomechanics Technologies to Deliver the First Ratawi Shale Horizontal Well in North Kuwait: A Case History

摘要

Integration of logging-while-drilling (LWD), nuclear magnetic resonance (NMR), and azimuthal acoustic tools with a geomechanical study resulted in successful drilling of the first horizontal Ratawi Shale well in Kuwait. This tool combination was used for the first time in Kuwait as a part of the bottom hole assembly (BHA), in addition to conventional formation evaluation tools, to acquire porosity without using radioactive sources. A deviated 8.5-in. borehole section of a well was planned through unconsolidated sand-shale sequences by kicking off from vertical and landing at an inclination of 90°. This geological section is typically crucial from a borehole stability point of view. Borehole deterioration and significant variations in pore pressure can create a high risk of becoming stuck-in-hole. The use of conventional porosity tools in a LWD BHA with installed radioactive sources would significantly elevate the risks to an environmental-hazard level. Additionally, even retrievable-based sources become problematic for successful extraction in high angle wells. Use of sourceless porosity was the perceived solution. LWD NMR and azimuthal acoustic tools, free of radioactive sources, were run for the first time in a LWD tool combination, with the primary objective to measure porosity, pressure prediction, and possible anisotropy using a centralized four-axis acoustic caliper. Previous experiences in the same geological setting encountered borehole enlargements by approximately 5 in. after only 15 to 16 hours. LWD helped bypass this issue and acquired high-quality data before borehole enlargement occurred. Additionally, indications of the presence of possible rock anisotropy were observed. The results were then correlated and matched to offset well data and existing field geomechanics knowledge. Well placement within a sweet spot of 6-to 8-ft thickness in the 6.125-in. lateral section was challenging and required the integration of at-bit measurements as well as distance-to-boundary geosteer-ing tools to reach this objective. This paper discusses the planning, design, and execution using LWD, NMR, and azimuthal acoustic tools in this well. It also discusses the viability, integrity, and robustness of logged data as well as interpreted results. Optimization of real-time drilling operations and petrophysical data acquisition requirements are also investigated to improve future field development and overall reservoir management strategies.