Sensitivity and application of pseudo-steady-state constant for refracturing horizontal wells with fracture reorientation in anisotropic tight oil reservoirs

Abstract

Fetkovich or Blasingame type rate decline analysis is a common and practical method to obtain reservoir parameters and evaluate well productivity. Pseudo-steady-state constant is an indispensable parameter for establishing these new type rate decline curves and works as a bridge linking conventional productivity and new type productivity. Refracturing is widely used to enhance tight oil wells’ productivity and improve their economic benefits, the pseudo-steady-state constant of refracturing horizontal wells has been presented in our previous research, but an in-depth discussion on the definition, accuracy, sensitivity, and application of this constant has not been conducted. It results in the insufficient understanding of the physical meaning, characteristics, and functions of pseudo-steady-state constant at present. In this study, taking the derived pseudo-steady-state constant for refracturing horizontal wells with fracture reorientation as an example, its accuracy was verified by an equivalent model presented in the literature, and the sensitivity of relevant key parameters on this constant was investigated. For the refracturing horizontal well defined in this study, pseudo-steady-state constant is independent of time, and related to fracture conductivity, fracture face damage, reorientation fracture number and permeability anisotropy. Results show that this constant decreases with the increase of fracture conductivity, but tends to remain unchanged when fracture conductivity increases to a certain extent. Meanwhile, this constant shows a positive correlation with fracture face damage and permeability anisotropy, but an inverse correlation with reorientation fracture number. Blasingame type rate decline curves of refracturing horizontal wells with fracture reorientation were also established, regarding as a practical application of this pseudo-steady-state constant and a concrete manifestation of its bridge-linking function. These type curves are directly conducive to the inversion of reservoir properties and fracturing parameters and the prediction of future productivity for refracturing horizontal wells. More importantly, this study is helpful to understand and strengthen the role and importance of pseudo-steady-state constant, and also beneficial to the establishment of new type rate decline curves of other similar models.