Step Change in Logging-While-Drilling Realtime Telemetry: Achieved High-Resolution Data Acquisition and Reduces Well Time, a Case Study in a Multilateral Well, Offshore Abu Dhabi

Abstract

Abstract Mature fields present a variety of subsurface and drilling challenges, including long laterals, multi-layer targets, and uncertainty in geology and reservoir fluids. In addition, it is essential to complete drilling operations in a timely manner to avoid any risk. Hence, the ability of logging-while-drilling (LWD) real-time data gathering for comprehensive formation evaluation has become crucial to identify and meet well objectives. This paper will elaborate the practical use and gains from deploying new LWD telemetry while drilling a multilateral well, where it helped to reduce well time and provided fast yet high-quality real-time downhole data. 6-in. horizontal sections of a multilateral well are the core study of this paper, highlighting the need for reliable downhole data during well placement and reservoir characterization. Two case studies with similar target formations are compared: Target Well-1A (lower drain) utilized the positive-pulse based telemetry, whilst Target Well-1B (sidetrack) utilized the next-generation negative-pulse telemetry. Target Well-1B employed the new technology in tandem mode, with the basic telemetry as backup in case of failure or interference that might occur from mud pump issues or bottomhole assembly (BHA) vibration. The LWD BHA configuration included ultra-deep azimuthal resistivity (UDAR), high-resolution Laterolog resistivity imaging, and triple combo (gamma ray – resistivity – neutron porosity – density), along with a push-the-bit directional RSS (rotary-steerable-system). Real-time high-speed data was provided on Target Well-1B, transferring LWD measurements from downhole to surface at high physical data rates (up to 15 bps) with mud weight up to 14 ppg. Over 5000 ft of lateral was drilled in a single run. Compared to the performance in Target Well-1A, the improvement in telemetry increased ROP by 80%, and reduced AFE days by 20%. High-resolution data was obtained, including ultra-deep resistivity 1D / 3D inversions comparable to recorded data quality, 360° borehole images, bulk density, neutron porosity, directional measurements, gamma ray, and downhole drilling dynamics. The negative-pulse-based telemetry proved its capabilities by providing multiple data types in a long lateral section, while achieving 100% MWD signal detection and significantly improving the ROP, as compared to previous performance utilizing positive-pulse telemetry. This case study shows how deploying tandem telemetry in the same BHA maximized on-bottom time and delivered multiple high-resolution measurements in real time as a complete suite for optimum well placement. Optimization of the completion design was conducted promptly during drilling, by enhancing real-time multilayer mapping and identifying non-uniform water boundaries. Following up this success case, future wells will be optimized to utilize this practice, in support of complex LWD sensor deployment in a challenging field. For both subsurface objectives and drilling operational performance, this high-quality real-time data increased operational reliability and provides an opportunity for more consistent well delivery in future.