An Integrated Completion Technology for Perforation, Stimulation and Production in Low Permeability Carbonate Reservoir in Central Iraq

Abstract Running in hole (RIH) strings with different bottom hole assembly separately for perforation, stimulation and production is necessary for casing well in low permeability carbonate reservoir. Given the time-consuming and potential formation damage caused by multi trip RIH, the integrated completion technology is urgently needed. The stability of packer is the key consideration for the implementation of integrated completion technology. In this paper, an integrated completion string was proposed, and the corresponding three-dimensional solid model was established based on real size and structure. The finite element method was utilized to analyze the stress and sealing condition of packer during the packer setting and perforation. Considering the fluid injection process and temperature change during acid fracturing treatment, the stress distribution of the pipeline under different pumping condition was simulated, and the corresponding packer stability was also evaluated. The simulation results indicate that the maximum axial stress of packer is located at the upper central tube in the setting process, with a value of 224MPa, and it is increased to 613MPa under the instantaneous impact of perforation. This axial stress value is always lower than the yield stress, demonstrating a safe packer condition. For the sealing performance of packer rubber, the contact stress between rubber and casing fluctuates with the respond time of perforation impact load, and the sealing index is always higher than the critical value, maintaining sealed condition. During the acid fracturing, with an injection rate of 3~5 cubic meters per minute, the pressure difference between the upper and lower annulus of the packer is acceptable. Meanwhile, an additional axial force of 188~306kN is generated by the temperature difference along the pipe string, and the packer can withstand the working condition according to the envelope curve. Moreover, a pilot trial of the proposed integrated completion string has been accomplished successfully in central Iraq. The perforation, acid fracturing and well testing were completed with only one trip of RIH, significantly enhancing the completion efficiency. Different from well completion with at least two trips of RIH, the approach proposed in this paper achieves safe implementation of perforation, stimulation, and production with only one trip. This study provides a novel strategy for cost saving and formation damage minimization in well completion.