CO2 Storage Capacity for Multi-Well Pads Scheme in Depleted Shale Gas Reservoirs

Abstract

As a promising technology to improve shale gas (SG) recovery and CO 2 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 CO 2 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 CO 2 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 CO 2 storage capacity. Both can be approximately related to the CO 2 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 CO 2 storage capacity, thus extending the injection period would improve CO 2 storage capacity. This work gains some insights into the CO 2 storage capacity of the MWPs scheme in depleted SG reservoirs, and provides considerable guidance on injection strategies to maximize CO 2 storage capacity in depleted SG reservoirs.

Effect of Stress-Sensitive Fracture Conductivity on Transient Pressure Behavior for a Multi-Well Pad With Multistage Fractures in a Naturally Fractured Tight Reservoir

“…Owing to the advancement of drilling horizontal wells with multistage hydraulic fractures (HFs), tight oil reservoirs have been exploited commercially though the flow behavior is quite different from those of the conventional reservoirs due to the extremely low permeability (Miller et al, 2008;Meyer and Bazan, 2011;Liu et al, 2018b;Liu et al, 2020a;Liu et al, 2020b. To reduce operational costs and mitigate the negative environmental impact, multi-well pad schemes have proven to be more effective for exploiting tight oil/gas reservoirs with and without natural fractures (NFs) (Manchanda and Sharma, 2013;Meng et al, 2017;Xiao et al, 2018;Jiang et al, 2020b;Jiang et al, 2020c); however, multi-well pressure interference under multiwell pad schemes severely distorts the flow patterns. In addition to greatly affecting well production, such a distortion inevitably makes the transient pressure analysis more challenging while the stresssensitivity effect and contribution of NFs are usually excluded (Liu et al, 2018a).…”