Leveraging LWD Ultrasonic Imaging for Enhanced Fracture Identification in Water-Injection Wells

Carbonate formations are known to be highly fractured. Water injection plays an important role in enhancing oil recovery, and accurate identification and characterization of fractures in the reservoir are crucial for optimizing injection strategies and ensuring efficient fluid displacement. This study investigates the application of logging-while-drilling (LWD) ultrasonic imaging technology as a tool for fracture detection and characterization in water-injection wells. Carbonate reservoirs are usually characterized by the presence of natural fractures. High-resolution ultrasonic imaging sensors acquire amplitude and travel-time images for identifying open fractures and measuring hole size. The integration of formation evaluation data and high-resolution images provides important information for reservoir characterization. The data in this study was acquired across a reservoir section for optimizing well injectivity. The study presents results from field trials where LWD ultrasonic imaging was employed for fracture identification in water-injection wells for the first time in the Upper Shuaiba formation, with no other water-injection wells nearby. The analysis focuses on the tool's ability to detect fractures, including their orientation, size, and distribution. Lost-circulation intervals associated with open fractures were resolved by the high-resolution image. The upper section of the drilled interval appeared to be highly fractured with some cemented fractures. Five faults were identified, most of them associated with multiple fractures and loss of circulation. The shallow resistivity log across the highly fractured zone showed clear variations due to the presence of fractures. The general fracture direction was NW-SE with some less frequent fractures with different fracture orientations aligned in the NE-SW direction. Bed dips picked from the borehole image showed a consistent SE dip direction with average dip of 7 degrees. The deployment of the ultrasonic imaging sensor in an injector provided important information for understanding fractures connectivity and its influence on injectivity. This knowledge can be used to improve reservoir performance.