Influence of gas transport mechanisms on the productivity of multi-stage fractured horizontal wells in shale gas reservoirs

Abstract

In order to investigate the influence on shale gas well productivity caused by gas transport in nanometersize pores, a mathematical model of multi-stage fractured horizontal wells in shale gas reservoirs is built, which considers the influence of viscous flow, Knudsen diffusion, surface diffusion, and adsorption layer thickness. A discrete-fracture model is used to simplify the fracture modeling, and a finite element method is applied to solve the model. The numerical simulation results indicate that with a decrease in the intrinsic matrix permeability, Knudsen diffusion and surface diffusion contributions to production become large and cannot be ignored. The existence of an adsorption layer on the nanopore surfaces reduces the effective pore radius and the effective porosity, resulting in low production from fractured horizontal wells. With a decrease in the pore radius, considering the adsorption layer, the production reduction rate increases. When the pore radius is less than 10 nm, because of the combined impacts of Knudsen diffusion, surface diffusion, and adsorption layers, the production of multi-stage fractured horizontal wells increases with a decrease in the pore pressure. When the pore pressure is lower than 30 MPa, the rate of production increase becomes larger with a decrease in pore pressure.

Optimization of Carbon Sequestration and Carbon Displacement in Fractured Horizontal Wells in Low Permeability Reservoirs

“…Considering the production mode of one production and one injection, that is, gas injection by horizontal wells at the top of the reservoir and oil production by horizontal wells at the bottom of the reservoir, this paper considers fracturing around the horizontal wells because of the low-permeability of the reservoir. To understand the migration law of carbon dioxide in the reservoir and the influencing parameters of enhancing oil recovery, based on the established reservoir numerical simulation model, four injection cases are analyzed to find the best injection model, and economic evaluation is conducted to obtain the best effect [37][38][39]. Figure 1 shows the workflow of this paper.…”

Molecular Structural Characteristics and 3D Model Reconstruction of Organic Matter in Longmaxi Formation Shale

“…3,4 In addition, the study of gas adsorption desorption and diffusion behavior in organic matter nanopores is also important for understanding the effect of organic matter on shale gas storage. 5,6 The type of organic matter has an important effect on shale gas capacity. The type of organic matter is mainly divided into type I, type II, and type III, and different types of kerogen have different oil-and gas-generating capacities.…”

Numerical Modeling of Natural Fracture Distributions in Shale

“…Worldwide, shale gas is being exploited to supplement the shortage of conventional energy in recent years (Gao et al, 2020;Li et al, 2020). Multi-stage hydraulic fracturing in horizontal wells is deemed to be an effective way to increase the production of shale gas (Wang et al, 2015). According to the experience of fracturing, natural fractures can interact strongly with hydraulic fractures and guarantee fracturing efficiency (Julia et al, 2007;Clarkson et al, 2016).…”