Pressure Analysis of Vertical-Wells with the Hydraulic Fracturing Assisted Water Injection in Low-Permeability Hydrogen and Carbon Reservoirs

Enhancing the energy of hydrogen and carbon reservoirs is crucial for the extraction of these resources. Currently, the conventional water-flooding technology faces challenges in replenishing the energy of hydrogen and carbon reservoirs due to the low injection rates caused by their low-permeability properties. To address this, hydraulic fracturing-assisted water injection technology has been employed to enhance the energy of these reservoirs. However, there has been a lack of research on pressure analysis for vertical wells using this technology. Existing studies on pressure analysis are not applicable to this scenario due to the unique behavior of dynamic fracture propagation. In this article, we present a pressure analysis model for vertical wells with hydraulic fracturing-assisted water injection in low-permeability hydrogen and carbon reservoirs, considering dynamic fracture propagation. The model examines the effects of key parameters on the pressure and fluid flow fronts, and it is applied to field wells for validation. Our findings include the following: the typical pressure response curve for vertical wells with hydraulic fracturing-assisted water injection in low-permeability hydrogen and carbon reservoirs can be divided into six stages: dynamic fracture propagation region, linear flow region in hydrogen and carbon reservoirs, bilinear flow region, radial flow region, transition flow region, and boundary control flow region. The production rate affects the pressure and pressure derivatives in the later stages of the process. However, reservoir permeability influences all flow regions, causing the pressure and pressure derivative curves to shift left with increasing permeability. Increases in both the injection rate and production rate result in a rise in the position of fluid fronts. The impact of permeability on fluid fronts is more significant in the early stages than in later stages. This work is of great significance for the development of low-permeability hydrogen and carbon reservoirs, providing a deeper understanding of the pressure dynamics involved in hydraulic fracturing-assisted water injection.