Success of the stimulation treatments in low-permeability, gas-producing formations largely depends on the fracture-face damage mitigation and cleanup of stimulation fluids from the propped fracture and formation matrix. These factors become even more critical in deep, conventional gas reservoirs, unconventional coalbed-methane reservoirs, shale, and ultralow-permeability tight-gas sands. Traditionally, in the industry, the focus for the success of the stimulation-fluid cleanup had been placed on conductivity damage of the proppant pack. It has more recently been realized that gas recovery and post-fracturing treatment results can be strongly dependent on other factors like wettability issues, phase trappings, water/gas relative permeability, and saturation states. The efficiency with which the fluids get extruded from the matrix or from the hydraulic fractures to the wellbore gets greatly diminished if conventional stimulation fluids are used without appropriate surfactant systems, leading to longer ROI times. Many microemulsion-surfactant systems have and are currently being developed based on the study of factors affecting the dynamicdisplacement behavior through the application of surfactants. Many so-called optimized treatments are not designed to adequately deal with all the issues within a particular well or reservoir and might actually create or cause more damage than originally existed.This paper describes laboratory test methods, comparisons, and results used for evaluating and selecting surfactants for deep, gas-bearing formations, such as shales and tight sandstones. Data presented here will aid operators in choosing the best surfactant/microemulsion package for optimizing hydrocarbon production.

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Almost three decades have passed since the early exploration of the north Texas, Barnett Shale. The Barnett serves as an example study for the shale lifecycle. Operators in North America have used the Barnett-shale development as a roadmap for the exploration of new shale plays like the Marcellus, Haynesville, and Eagleford. Each new shale play is unique in nature with respect to geologic setting, lithology, and production mechanism. It is useful to have a defined strategy for the discovery, development, and decline phases of each individual shale play. The roadmap to shale well-completion designs should include the following key factors: Fracability: capability of the reservoir to be fracture stimulated effectivelyProducibility: capability of the completion plan to sustain commercial productionSustainability: capability of the field development to meet both economic and environmental constraints This paper reviews the evolution and development of completion practices of the major USA shale reservoirs in the last two decades and presents a roadmap for effective completion practices for shale stimulation. The completion roadmap uses the history of 16,000 shale frac stages in the Barnett, Woodford, Haynesville, Antrim, and Marcellus shales. Following the map through specific decision points will alter the path for individual shales. These decision points will be influenced by geologic, geochemical, and geomechanical information gathered along the way. The path toward a commercially viable shale play from the early asset-evaluation phase to late asset maintenance-and-remediation phase evolves from a series of decision trees throughout the process. Information presented in this paper provides a completion engineer with better understanding of the factors involved in shale-play stimulation and provides a methodical approach to select appropriate and optimum solutions that have evolved during the last two decades.

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