Pressure Buildup Test Analysis for Hydraulic Fractured Horizontal Well with Stimulated Reservoir Volume in Tight Oil Reservoirs

Abstract

Regarding hydraulic fractured horizontal well with stimulated reservoir volume well test analysis, most of the current research on pressure drawdown curve, and pressure buildup test is a common test method, so it is necessary to carry out test analysis of transient pressure buildup of multi-fractured horizontal well (MFHW) with seam network. Aiming at the characteristics of the formation after multiple hydraulic fracturing of the tight oil reservoir, the stimulated reservoir volume (SRV) is described as the dual medium system consisting of matrix and micro-fracture, and the unstimulated reservoir volume (USRV) is described as the matrix system with poor permeability. The mathematical model of transient flow in hydraulic fractured horizontal well with SRV is established. The finite element method is used to solve the problem. The typical test curve of pressure buildup for MFHW with seam network is given, the characteristics of typical curve and the sensitivities are analyzed. The results show that the pressure buildup test curve is divided into six flow stages, the linear flow around the hydraulic fracturing, pseudo-steady state in the transient region, the inter-porosity flow stage, the linear flow in USRV, pseudo-radial flow in USRV and boundary effect stage. The storability ratio and inter-porosity flow coefficient mainly affect the inter-porosity flow stage. The smaller the storability ratio is, the deeper the “groove” is; the larger the inter-porosity flow coefficient is, the earlier the “groove” is formed; the number of fracture increases, the volume of the SRV is larger and the radial flow of USRV is formed later; the worse the fluid flow capacity in USRV, the closer the slope of the pressure drawdown derivative curve is to 1 in pseudo-steady state in the transient region, and the slope of the pressure buildup curve deviates from 1. Finally, an example of pressure buildup test interpretation of a well is given. This study can provide a scientific basis for the interpretation of pressure buildup test data for hydraulic fractured horizontal well with stimulated reservoir volume.