Pressure transient responses study on the hydraulic volume fracturing vertical well in stress-sensitive tight hydrocarbon reservoirs

Based on the characteristics of stimulated zone and un-stimulated zone after hydraulic volume fracturing of vertical well, as well as considering the stress-sensitive characteristic of the tight oil reservoir, the two-zone composite pressure transient responses model is built. The inner zone represents the stimulated reservoir volume region and is modeled as a dual-porosity radial reservoir, while the outer zone represents the un-stimulated reservoir volume region and is modeled as a single porosity reservoir. The model is solved by the method of superposition, Laplace integral transformation, Stehfest numerical inverse algorithm, and the perturbation technique. Thus the analytical solutions to the model are obtained. On the basis of the field example verification of the model, the flow regimes of the hydraulic volume fracturing vertical well are analyzed. The results of the study show that the new model can provide the reliable pressure transient responses model for hydraulic volume fracturing vertical well, and the flow regimes can be divided into five stages, including the wellbore storage stage, transition flow from matrix system to fracture system, radial flow of SRV zone, transition flow from UN-SRV zone to SRV zone, and radial flow of whole reservoir system. The new model and study are conducive to the well test interpretation of hydraulic volume fracturing vertical well in stress-sensitive tight oil reservoir.