Abstract

The success of any unconventional asset development depends heavily on the effectiveness of the design and execution of the stimulation treatments performed on the horizontal wells. Each shale play is different with regards to geology, rock type, and production mechanism. Identification of the geological and reservoir characteristics of the shale play is the first step towards effective development of an asset. Completion design optimization is the next important step that improves the well performance. An optimized completion design can be ineffective if the placement efficiency of the treatment is hampered by high tortuosity or near well bore friction effects. Inability to place optimized proppant mesh size or proppant volume in the formation can adversely affect the well performance and economics.

The South Texas Asset Team implemented a benchmark standard completion during the appraisal and initial development phases. During this time, more detailed geological and reservoir characteristics were obtained by the team members. Next, a road map to an optimized completions plan was developed and implemented. As a result of the optimization tests, bigger mesh size (20/40) of proppant was recommended. In certain areas of the asset, occasional failures were experienced in placing 100% of the designed proppant volume with the 20/40 mesh size. Rate step-down tests were then introduced on every stage, the results were analyzed and remedial measures were implemented. The introduction of the step down analysis and the remedial measures helped improve the placement efficiency with the 20/40 proppant mesh size.

This paper includes the description of the challenges faced during placement of the 20/40 mesh proppant on certain horizontal well completions, detailed procedure of the rate step-down tests, the analysis, and the lessons learned. Based on the analysis of the step-down tests, a baseline values for the near wellbore tortuosity was established. This study also discusses how the comparison of results from rate step-down analysis to the baseline values was used to make real-time decision in preventing low concentration screen-outs and placing 20/40 mesh size effectively. Overall, this paper will provide a completion engineer with a better understanding of the factors to be considered while performing and analyzing the rate step-down tests.

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