Abstract
As a promising technology to improve shale gas (SG) recovery and CO2 storage capacity, the multi-well pads (MWPs) scheme has gained more and more attention. The semi-analytical pressure-buildup method has been used to estimate CO2 storage capacity. It focuses on single multi-fractured horizontal wells (SMFHWs) and does not consider multi-well pressure interference (MWPI) induced by the MWPs scheme. This severely limits the application of this method as incidences of multi-well pressure interference have been widely reported. This paper proposed a new methodology to optimize the injection strategy of the MWPs scheme and maximize CO2 storage capacity. The new method implements numerical discretization, the superposition theory, Gauss elimination, and the Stehfest numerical algorithm to obtain pressure-buildup solutions for the MWPs scheme. The solution by the new method was validated with numerical simulation and pressure-buildup curves were generated to identify MWPI. Using the new method, we observed that the fracture number and fracture half-length have a positive influence on CO2 storage capacity. Both can be approximately related to the CO2 storage capacity by a linear correlation. For a given injection pressure, there is an optimal fracture number; the bigger the limited injection pressure, the smaller the optimal fracture number. Stress sensitivity has positive influences on CO2 storage capacity, thus extending the injection period would improve CO2 storage capacity. This work gains some insights into the CO2 storage capacity of the MWPs scheme in depleted SG reservoirs, and provides considerable guidance on injection strategies to maximize CO2 storage capacity in depleted SG reservoirs.
Highlights
Greenhouse gas control has been a focus of research attention due to climate change induced by the emission of greenhouse gases such as carbon dioxide [1,2]
The computation performance presented is not significantly improved. We suggest that this comparison for the computation performance should be a rough evaluation due to the simple fracture configuration, the relatively small total length of the fracture, and the implementation
To gain quick and reasonable estimations of CO2 storage capacity for the multi-well pads (MWPs) scheme in a depleted shale gas (SG) reservoir, in this paper we develop a semi-analytical pressure-buildup model with consideration of multi-well pressure interference (MWPI)
Summary
Greenhouse gas control has been a focus of research attention due to climate change induced by the emission of greenhouse gases such as carbon dioxide [1,2]. The production-based method was introduced by Tao et al [10] to evaluate the CO2 sequestration capacity of the Marcellus Shale. They estimated the CO2 storage capacity based on historical and projected shale gas production data. Numerical simulation methods were established to evaluate the storage capacity of CO2 injection [11], which can be used to simulate CO2 flow behavior in shale. This method requires grid discretion, which is time-consuming in a field-scale application [12,13]
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