Hydraulic Fracturing in a Devonian Age Carbonate Reservoir: A Case Study

Recent technological progress within the petroleum industry has enabled much deeper discoveries than conventionally accepted depths. One example of such exploration success is drilling and stimulating an appraisal well in a Devonian age carbonate reservoir in northwestern Kazakhstan. This paper describes a successful case study of hydraulic fracturing stimulation as a solution to enhance hydrocarbon recovery. A specific workflow developed for stimulation of high pressure and temperature low permeability reservoir is suggested. This workflow includes an adapted study of petrophysical properties, fracture geometry modeling, and completion design selection. Fracture stimulations and pre- and post-completion results are also analyzed and compared. One of the main tasks of the technical staff was designing a production enhancement method which would maintain positive return on investment (ROI) for the project. A reservoir study was conducted during the planning stage of this pilot project. The design workflow included geomechanical analysis to estimate reservoir rock properties. Fracture stimulation modeling was performed to forecast treating pressures and adjust treatment stage sizes to help achieve optimum fracture geometries. Perforation intervals were selected and recommended to provide the best placement of fracturing fluid and proppant into the zone of interest. Previously, the operator had attempted an acid wash, which was unsuccessful because of coiled tubing (CT) capability limitations, making it impossible to inject acid in desired rates into the rock due to low permeabilities and high stresses. Then, based on the final designed stimulation treatment plan, the operator conducted a massive proppant and acid fracturing stimulation operation, where high pressure pumping was performed at the treating pressures above formation breakdown limits. Created hydraulic fractures provided conductive pathways for reservoir fluid inflow. This method has shown an improved recovery of reservoir fluid. This hydraulic fracturing technique provided economically effective field exploration in the previously undeveloped part of the licensed block. Field execution has shown challenges with respect to performing operations in deviated wells. Observations conducted in three stages during the pilot project are described and conclusions presented. This paper also describes operational difficulties with equipment combined with materials logistics.