ABSTRACT

The paper describes a case study utilizing a logging-while-drilling (LWD) acoustic imaging device to collect wellbore data and to achieve geoscience and drilling engineering objectives in lateral development wells in a tight oil play in Central US. A memory based LWD ultrasonic logging tool was chosen for its compact size and low impact on bottom-hole-assembly (BHA) configuration and versatility in water-based and oil-based drilling mud systems. The technology fits a critical cost structure aspect of key performance indicators in unconventional asset development and provides wireline equivalent borehole images for geoscience applications including detection and characterization of sedimentary bedding planes, structural features, and fractures as well as for drilling engineering applications including BHA performance evaluation and hole quality analysis. A pilot data collection program was planned and successfully executed in appraisal wells across the basin. Data analytics was carried out by an integrated team of geoscientists and drilling engineers leveraging knowledge from regional environments of deposition, seismic data, and historical drilling performance.

Effective acquisition strategies of acoustic image datasets were devised based on optimized ratios of drill pipe rotation speed (RPM) and rate of penetration (ROP) to maximize image resolution using either mud motors or rotary steerable systems in lateral wellbores. Ultrasonic amplitudes and travel times were binned azimuthally to produce high resolution image logs. Acoustic amplitude images were interpreted to map structural features such as folds, faults, and sedimentary bed boundaries which were not seismically resolvable. Fractures and drilling induced artifacts were also interpreted. Analysis of travel time image data enables thorough hole quality evaluation to identify key seating, spiral holes, and other drilling artifacts which provide crucial insights to understanding drilling dynamic and drilling system performance. From an operator's point of view, this technology is proved to be desirable for its excellent data quality at competitive cost comparing with existing LWD ultrasonic tools.

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