High-resolution images from a Logging While Drilling (LWD) ultrasonic imaging tool were used to identify induced fractures, map offset well communication and optimize hydraulic fracturing practices in a series of infill horizontal wells drilled with oil-based mud. Previous mineback studies were able to characterize the existence and impacts of bi-linear fractures when drilling with water-based systems (Ambrose, 2011).
This newly developed LWD ultrasonic imager was used to acquire wellbore images while drilling infill wells in an unconventional shale in the US where oil-based systems are utilized. In a joint effort between the service company and the operator, design engineers and the drilling/reservoir teams optimized logging operations to acquire high-quality images used to identify and characterize fractures immediately after the well reached TD.
Operators are interested in this primarily because it allows detection of zones that could be, for instance, affected by offset well interference, which enables optimization of the hydraulic fracturing operations. Additionally, the fracture-to-wellbore connections may also be mapped by integrating the image interpretations into robust, history-matched reservoir and geomechanical models for fieldwide development strategies and improvements. Extensive compositional and geomechanical numerical modeling was performed and improved with this data, and this data was successfully used to enhance imaging interpretations, completions development strategies, and ongoing EOR applications in critical areas of the field (Fiallos, 2019).
The ultrasonic imager was run in different areas of the operator's unconventional shale acreage that captured variability in black oil, volatile, and retrograde condensate fluid systems, providing high-quality images that allowed identification of different formation features such as bedding planes, natural fractures, and induced fractures. The presence of fractures induced by nearby wells suggested the communication between parent-child wells in areas of the lateral. These zones were identified, mapped and isolated to mitigate the fracture interference. The child wells where this technique was used showed a more efficient use of capital expenditures and a reduction in the negative impact in parent-well production. The operator also established how the reservoir and geomechanical models in the area were fractured, enhancing predictiveness by identifying detailed hydraulic fracture interference. This allowed for better assessment of primary recovery and EOR optimization.
This case study shows one of the first proven cases where an LWD ultrasonic imaging tool was used for completion optimization and improvement of child-well production to mitigate well intercommunication and field characterization for ongoing and future studies.