Unconventional development of oil and gas shale and tight reservoirs has globally become very active in recent years. Hydraulic fracture operations in horizontal wells have unlocked a vast amount of hydrocarbon resources. Hydraulic fracture treatments enhance the flow of reservoir fluids to the wellbore by increasing the amount of reservoir area in direct contact with the wellbore. Often, optimized hydraulic fracture designs deliver high initial production rates which rapidly decline until stabilizing at a relatively low rate and maintaining that rate for many years. Overcoming these trends to improve recovery is a major challenge. This technology development focuses on increasing recovery by designing and optimizing fluids for stimulation of specific shale formations. This stimulation fluid maintains clean fractures and penetrates deeper into the stimulated area, mobilizing more hydrocarbons, by altering rock wettability and lowering interfacial tension (IFT).

This paper describes the workflow and preliminary results associated with designing and field-testing stimulation fluids with focus on enhancing hydrocarbon recovery in shale and tight reservoirs. Emphasis is placed on having a robust field test program that includes comprehensive surveillance and execution planning. Details of the pilot preparation, execution, surveillance analysis and optimization (SA&O) are noted, including identification of early signposts of key data and analysis to support the conceptual model. Various analysis techniques, including reservoir modeling and analytical methods such as rate transient analysis (RTA), decline curve analysis (DCA) and tracer response, are combined to provide an integrated interpretation of test results.

The paper describes the application of using water and surfactants as a stimulation fluid additive on two existing wells from the Permian Chevron unconventional asset. Computer-based modeling is used to predict pre-test and calibrate post-test well performance, addressing key physical mechanisms potentially impacting the recovery. Lastly, field test execution and implementation of the SA&O plan are discussed, advocating integration of tracer, production, pressure, and productivity index (PI) data, to assess recovery potential and well performance effects. For the results obtained, we can conclude that stimulation with surfactant additives could improve oil recovery by wettability alteration, cleanup and IFT reduction, maximizing well performance after stimulation.

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