An Integrated Reservoir Model for Unconventional Resources, Coupling Pressure Dependent Phenomena

Abstract

An integrated unconventional reservoir model that accounts for known mechanisms and nonlinearities affecting modeling of hydraulically fractured wells is developed. In general, modeling and simulation of multi-fractured reservoirs are highly challenging due to the complexity attributed to the flow in this very low permeability and dense structured rock. Pressure-dependent phenomena in reservoir modeling are considered as combined hydraulic and natural fracture conductivity losses, desorption, Klinkenberg gas slippage effect and non-Darcy flow. Integrating these phenomena and analyzing the importance of each parameter in a reservoir model are essential.The proposed model includes three zones, Rock Matrix (I), Induced-Fracture (II) and Hydraulic Fracture (III) that are defined with different characteristics. Pressure dependent permeability is considered for zone II and III, with an exponential relationship between permeability and reservoir pressure. Governing equations of gas flow are non-linear partial differential equations, for all three zones, due to incorporated pressure-dependent phenomena that are solved using the finite difference method. A synthetic case is defined in order to investigate the effect of each individual phenomenon on long-term production. Moreover, a history matching process with Marcellus Shale field production data is performed in order to obtain the most uncertain parameters in the model.Results showed that combined effect of permeability losses of hydraulic and induced-fracture zones results in 15 percent gas production drop in 30 years. Also, it is observed that Klinkenberg effect and non-Darcy flow have insignificant effect on the modeling of shale gas reservoirs, whereas desorption has great contribution on long-term production. It is concluded that the minimum ingredients for an accurate shale reservoir modeling are considering gas desorption phenomena alongside with pressure-dependent permeability for the hydraulic and induced-fractures network. Our simple reservoir modeling approach helps in understanding complex behavior of flow mechanisms in shale plays. Also, this integrated model can be used during optimization of key factors in hydraulic fracturing process and fracture characterization by history matching of production.

Discrete fracture networks modeling of shale gas production and revisit rate transient analysis in heterogeneous fractured reservoirs

“…In this section, we present a production history match for the Marcellus Shale gas well using our fully coupled model. This dataset has been previously studied by Eshkalak et al (2014). Similar to our presented model, Eshkalak et al (2014) modeled the non-Darcy flow effects in the matrix with an exponential decline for the change in propped-hydraulic-fracture and induced-fracture permeability as a function of confining pressure.…”

“…This dataset has been previously studied by Eshkalak et al (2014). Similar to our presented model, Eshkalak et al (2014) modeled the non-Darcy flow effects in the matrix with an exponential decline for the change in propped-hydraulic-fracture and induced-fracture permeability as a function of confining pressure. The choosing of matching parameters and fracture permeability estimation are discussed by Mirani et al (2018).…”

Coupled Thermo-Hydro-Mechanical-Chemical Modeling of Water Leak-Off Process during Hydraulic Fracturing in Shale Gas Reservoirs

“…We assume the hydraulic fractures are evenly spaced. The inputs of the reservoir, fracture, fluid and heat properties [35,36,[55][56][57][58] are given in Table 1.…”

“…Specifically, once the low-temperature, high-pressure and low-salinity water contacts the shale matrix through the hydraulic fractures, both mass and energy transfer occur due to the significant temperature, pressure, saturation and salinity gradients. Although many leak-off models have been published based on laboratory experiments and numerical simulation [3,[5][6][7][8][11][12][13][14]16,32,36,37], none of the models coupled the transient fluid flow modeling with natural fracture dilation, heat transfer and chemical-potential equilibrium phenomena. To investigate all of the above-mentioned mechanisms, a coupled thermo-hydro-mechanical-chemical (THMC) model, which is based on our previous multi-mechanistic multi-porosity multi-permeability (MMM) model [37] without considering heat transfer and rock deformation, is developed to simulate the fluid/heat flow during the leak-off process of hydraulic fracturing in this study.…”

An Economic Evaluation on the Re-fracturing Treatment of the U.S. Shale Gas Resources

“…Many studies are conducted from the shale pore scale up to reservoir scales to improve the understanding of flow behavior in complex shale formations. Among them, researchers such as Ozkan et al (2009), Cipolla (2010), Moghanloo and Javadpour (2013), Yu and Sepehrnoori (2013), Haddad and Sepehrnoori (2014), Sanaei et al (2014), Aybar et al (2014), and Eshkalak et al (2013; have developed and discussed numerical, quasi-static, analytical and semi-analytical reservoir models for unconventional reservoirs.…”