Shale gas reservoir modeling and production evaluation considering complex gas transport mechanisms and dispersed distri
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ORIGINAL PAPER
Shale gas reservoir modeling and production evaluation considering complex gas transport mechanisms and dispersed distribution of kerogen Jie Zeng1 · Jishan Liu1 · Wai Li1 · Yee‑Kwong Leong1 · Derek Elsworth2 · Jianchun Guo3 Received: 13 March 2020 © The Author(s) 2020
Abstract Stimulated shale reservoirs consist of kerogen, inorganic matter, secondary and hydraulic fractures. The dispersed distribution of kerogen within matrices and complex gas flow mechanisms make production evaluation challenging. Here we establish an analytical method that addresses kerogen-inorganic matter gas transfer, dispersed kerogen distribution, and complex gas flow mechanisms to facilitate evaluating gas production. The matrix element is defined as a kerogen core with an exterior inorganic sphere. Unlike most previous models, we merely use boundary conditions to describe kerogen-inorganic matter gas transfer without the instantaneous kerogen gas source term. It is closer to real inter-porosity flow conditions between kerogen and inorganic matter. Knudsen diffusion, surface diffusion, adsorption/desorption, and slip corrected flow are involved in matrix gas flow. Matrix-fracture coupling is realized by using a seven-region linear flow model. The model is verified against a published model and field data. Results reveal that inorganic matrices serve as a major gas source especially at early times. Kerogen provides limited contributions to production even under a pseudo-steady state. Kerogen properties’ influence starts from the late matrix-fracture inter-porosity flow regime, while inorganic matter properties control almost all flow regimes except the early-mid time fracture linear flow regime. The contribution of different linear flow regions is also documented. Keywords Analytical solution · Shale gas reservoir · Well performance · Kerogen and inorganic matter
1 Introduction Recent years have seen a dramatic increase in shale gas production as shale reservoir development using multistage fractured horizontal wells (MFHWs) has achieved great success and is one of the main focuses in the petroleum industry (Li et al. 2017; Wang et al. 2017). A stimulated shale reservoir can be classified into four sub-systems, including Edited by Yan-Hua Sun * Jie Zeng [email protected] 1
School of Engineering, The University of Western Australia, 35 Stirling Highway, Perth, WA 6009, Australia
2
Department of Energy and Mineral Engineering, G3 Center and Energy Institute, The Pennsylvania State University, University Park, PA 16802, USA
3
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
kerogen, inorganic matrix, secondary and hydraulic fracture systems. Due to different spatial structures of these sub-systems, their properties control well performance at different timescales. Generally, gas production first comes from fractures. At that time, the matrix gas inflow is negligible (Wasaki and Akkutlu 2015). In a later stage that occupies
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