Tackling Well Productivity and Sustainability in a Jurassic Horizontal HPHT Well with the First Multistage Unconventional Hydraulic Fracturing in MFS Formation: A Case Study of an Exploration Well

Abstract

Abstract The unconventional Lower Najmah Limestone MFS fractured reservoir is a nanodarcy rock located below the Najmah Kerogen source rock. The first horizontal well drilled across the MFS is in North Kuwait and was drilled to explore the hydrocarbon potential. The 3D seismic interpretation and several seismic attributes indicate that the well location is likely to encounter a high fracture corridor area to support production after multistage hydraulic fracturing. The lateral length is approximately 1,900 ft placed in the MFS after reaching the planned total depth (TD), 18,900 ft. The well was completed using a 15,000-psi-rated openhole multistage completion (MSC) system to place six hydraulic proppant fractures and access most of the nearby natural fractures in the reservoir. Over 20 well interventions were conducted by coiled tubing (CT) to shift the MSC frac ports, log the well by caliper and spinners, perforate stages, attempt milling out the inner completion seats, and, finally, perform nitrogen lifting of the hydraulic fracturing treatment fluids to the surface. Due to the high-pressure nature of the reservoir and multiple additional completion challenges, it was difficult to initiate hydraulic fractures into the formation below the maximum allowable working pressure of completion. Therefore, 20 ft of 12 shots per foot (SPF) perforations were added per stage for four stages, which significantly lowered the fracture initiation pressures. Complete data fracturing analysis was conducted in each stage to redesign stimulation treatments. Four unconventional hydraulic proppant fracturing stages were successfully completed, sequencing high-viscosity slickwater and a crosslinked fluid system placing 110,000 lbm of proppant per stage into the formation. Multiple milling attempts were conducted with CT to reach TD but were unsuccessful due to uncertain obstructions. However, an unconventional method was applied and finally succeeded in accessing the full lateral and flowing back the well. This work highlights the operational and technical challenges and solutions to design, execute, and evaluate the first horizontal well in the MFS reservoir, Kuwait. The developed workflow presents solutions for future horizontal wells drilled through the unconventional Najmah and similar formations across Kuwait. The work provides valuable lessons learned, insights, and perspectives for the complexity of the MFS to optimize production from challenging reservoirs.