First Successful Channel Fracturing Job, in the Middle East, Across Darcy-Permeability Sandstone Formation in Challenging Preperforated Liner Disposal Well Proves to be the Optimum Solution for Enhancing Injectivity

Abstract

Produced water is a byproduct of the production cycle that often creates problems for handling and disposal. In Khafji Joint Operation (KJO), thousands of BWPD were being produced every day and disposed of by pumping the water back into the A formation. This formation is sandstone and has a permeability range over one Darcy. To improve the economics of this project, KJO set an injection target rate of 30,000 B/D per well at a maximum of 1,500-psi wellhead injection pressure due to surface facility constraints. Several completion and stimulation methods were selected to enhance the injectivity rate of these disposal wells. A pilot project was conducted to understand the best methods for injector well development. The well was drilled slanted across the reservoir to increase the reservoir contact area. Openhole and preperforated liners with different upper completion tubing sizes (i.e., 5-in. and 7-in. tubing) were compared to set the baseline of injectivity. Coiled tubing matrix acidizing and hydraulic fracturing were performed in this pilot well to enhance the injectivity. In each different methodology, a series of injection and surveillance tools was deployed to quantify the results. Upon completion with the 5-in. tubing, the pilot well could not achieve the target injectivity rate without well stimulation. An improvement after acid stimulation via coiled tubing was observed, although it was not able to achieve the injectivity target. Completing the well with 7-in tubing improved the injectivity rate slightly, but the injection pressure was still relatively high. Finally, and despite the combination of all challenges in this well, the first channel fracturing in a preperforated injector well in the Middle East was successfully performed. The post-fracturing evaluation shows that channel fracturing is the optimal stimulation method, increasing the injectivity index in this well ninefold compared to matrix acidizing. These results suggest that the implementation of effective fracturing design and operations improves the economics of the project. The results also demonstrate the importance of surveillance activities and their analysis to guide the technical decision and technology deployment. To overcome the challenges, a clear and robust workflow and solution execution and surveillance methods were developed. The pilot project illustrates the importance of having the right data to guide decisions and a rigorous QA/QC approach before, during, and after fracturing to achieve successful delivery.