Abstract Gas production from shale reservoirs has led to an era with a new source for energy. Like many other exploration and production activities, uncertainty and risk in developing shale gas reservoirs are quite significant. Although many reservoir characterization efforts have been made to help understand shale gas reservoirs, a systematic reservoir modeling–based approach appears lacking in the literature. This chapter presents a methodology to integrate various sources of data for characterization and modeling of shale gas reservoirs, including seismic, geologic, borehole image, conventional well-log, hydraulic fracturing treatment, and microseismic data. An integrated reservoir characterization workflow enables uncertainty analysis and quantification, including multidisciplinary integration for better characterization of reservoir properties, experimental design to rank most critical parameters and dynamic reservoir simulation for probabilistic production forecasting. Such an integrated workflow is efficient in capturing main characteristics of shale gas reservoirs and offers a quantitative means for optimizing developments of these fields. Driven by the gas demand in the last several years, shale gas production has continued to increase. Some of the characteristics of shale gas reservoirs include extremely low permeability, relatively low porosity, and moderate gas adsorption. For example, the Barnett Shale typically has permeability in the range of 100 to 600 nanodarcys, porosity in the range of 2 to 8%, and gas content in the range of 50 to 150 SCF/ton (Frantz et al., 2005 ; Gale et al., 2007 ; Loucks and Ruppel, 2007). To date, a large number of horizontal wells have been drilled, and massive multi-stages of hydraulic fracturing treatments (HFTs) have been commonly applied to achieve economic production and enhance productivity. The complex nature of the shale gas reservoirs is multifaceted, including total organic carbon (TOC), mineralogy and lithology, pore and throat geometry, texture, anisotropy and heterogeneity, natural fracture network, rock mechanical property heterogeneities and in-situ stress distributions, faults/karsts and structure impact, and production operation interaction with the reservoir. The latter itself included horizontal well pattern, well completion, hydraulic fracturing process (such as different fracturing operation schemes), the number of stages, perforation clusters, pumping rate, total volumes, and so on. Therefore, the development of shale gas reservoirs is quite different from that of conventional or other types of unconventional reservoirs. It is commonly difficult to obtain a clear understanding and an accurate description of the post-HFT reservoirs. To quickly acquire knowledge and guide well placements, various well-spacing pilots are commonly used, and various hydraulic fracturing operation schemes, such as “zipper-frac” and “simul-frac,” have been tested (Waters et al., 2009).

Abstract This study presents a reservoir simulation model to analyze the impact of reservoir and hydraulic fracture parameters on gas production from a shale gas reservoir. The model was constructed as a multiporosity system with matrix subgrids to account for transient gas flow from the matrix to the fractures. The extended Langmuir isotherm was applied to control the desorption process of multiple components during the production. Primary hydraulic fractures perpendicular to the horizontal wellbore were modeled explicitly with thin grid cells that preserved the conductivity. The hydraulically induced fracture network around the horizontal well was characterized by the matrix-fracture coupling factor and permeability of the fracture system. The linear experimental design technique of the Plackett-Burman type was used to screen influential parameters including porosity and permeability of the reservoir matrix and fractures, matrix-fracture σ factor, matrix subdivisions, primary hydraulic fracture half-length, height, spacing, and conductivity, rock compaction, non-Darcy flow coefficient, and gas content. A quadratic response surface model was constructed with three-level uncertainty parameters selected from the initial linear screening process. The model was verified by confirmation runs. Sensitivity studies provided important insights into the impact of reservoir and fracture parameters on shale gas production forecasts, which can be critical for fracture treatment design and production scheme optimization. During the past few years, natural gas production from shale gas reservoirs has been a key source of energy in North America and will likely become an increasingly important component of the world's energy supply. A shale gas reservoir is characterized by organic-rich sediments with extremely low matrix permeabilities in the order of nanodarcys, and clusters of mineral-filled natural fractures that are not open to flow. Shale gas storage capacity is represented by the gas adsorbed onto the organic material and free gas in the pore space of the shale rocks. Horizontal drilling and hydraulic fracturing have proven to be the most effective technologies to stimulate the reservoirs and open natural fractures for economic production.