Assessment of temporal scales for the flow of fluid in stimulated reservoir volume of a tight reservoir

Key words:  tight reservoir  inhomogeneity  temporal scales  time lag  unsteady coupling

Abstract:

On the basis of the low permeability and porosity, inhomogeneity and anisotropy, a flow model in the stimulated reservoir volume (SRV) of a tight reservoir was established in the present work. Due to the variation in flow regime and the tortuous flow region, the fluid remains within the pore and the fracture for a longer time. Therefore, the flow pressure affects the fluid flow afterwards. This is explained by the time lag effect. The finite element method in Laplace domain was used to obtain the solution of the proposed model, through which the analysis of temporal scales for the wellbore pressure was conducted. And the impacts of the shapes of pore and fracture, the permeability and the porosity on the wellbore flow pressure were characterized. The results show that the strong reservoir heterogeneity was the reason for the co-existence of multiple temporal scales. And the scales of the micro-geometry of pores and fractures were updated through the time lag of the fluid flow. It is found that the wellbore flow pressure is reduced due to the time lag initially. Consequently, the pressure propagation is slowed down due to the tortuous flow region and the bifurcate artificial fracture, resulting in the exploitation of more fluid in the SRV. While the impact of unsteady coupling was evident for the fluid flowed afterwards, the impact of the region far from the wellbore on the wellbore flow pressure was weakened. In addition, the difference in flow velocities of different media is also described in more details. Also, the impact of the region far from the wellbore on the bottom hole pressure is also found to be weakened by the constant well rate.