Micro-Fracturing in Depleted and High Permeability Reservoir

Abstract Understanding in-situ stress conditions is essential for the safe and efficient drilling and completion of wells, particularly in depleted and high-permeability reservoirs where wellbore stability becomes a significant concern. This paper presents a field case study involving the successful application of wireline-conveyed micro-fracturing in such a challenging environment. The primary objective was to accurately determine breakdown pressures and minimum principal stress to calibrate and refine geomechanical models used for well planning. The outcomes of this work directly contributed to the optimization of drilling parameters and led to substantial cost savings in the development of subsequent wells. Micro-fracturing on wireline comprises of straddling the zone of interest between packers and creating small-scale hydraulic fractures to obtain information about stresses in the reservoir rock. Once the injection stops, the built-up pressure dissipates into the formation causing the fracture to close, yielding the minimum principal stress. Micro-fracturing operations were performed using a formation testing tool string equipped to isolate four target reservoir zones between inflatable packers. Small-scale hydraulic fractures were induced, and real-time pressure data was monitored for breakdown and closure signatures. The pressure fall-off after injection cessation was analyzed using G-function and square-root time methods to determine minimum principal stress. The paper details the design and execution of these operations, emphasizing the integration of reservoir-specific properties and geomechanical understanding into test planning. Of the four zones tested, three yielded successful fracture events, while one did not experience breakdown within the tool’s operational limits. Nonetheless, even the unsuccessful attempt provided valuable lower-bound estimates for fracturing pressure. The minimum principal stress measured in two of the zones aligned well with pre-test model predictions, while the other two showed significant deviation. These discrepancies underscored the importance of direct measurements in reducing model uncertainties. Based on the findings, geomechanical models were recalibrated and applied to future wells in the field. The study demonstrates the technical viability and advantages of micro-fracturing in depleted, high-permeability formations. Compared to conventional stress estimation methods, this approach allows for precise fracture placement, lower fluid volumes, and reduced environmental footprint. Importantly, the recalibrated models informed decisions that led to reduced reliance on Managed Pressure Drilling (MPD) techniques. As a result, the operator avoided significant operational complexities and realized an estimated cost saving of approximately USD 4.5 million. While micro-fracturing is an established technique, its deployment in depleted reservoirs has been limited due to concerns over well control and formation damage. This study highlights a successful execution under such conditions, providing valuable insights into risk mitigation, model enhancement, and cost-effective well construction. The outcomes offer meaningful guidance for engineers and decision-makers working in similarly challenging reservoir environments.