ABSTRACT: Hydraulic fracturing treatments can efficiently enhance the well production performance in low-permeability reservoirs because of the improvement of communication between the formation and wellbores through created hydraulic fractures. In fact, not only the in-situ stress underground but also the pre-existed offset wells will influence the fracture propagation process. In this work, both experimental and numerical studies are carried out to investigate the hydraulic fracture propagation behavior under the effects of adjacent production and injection wells. First, laboratory tests were conducted to measure the rock mechanical properties. Based on the experimental results, we developed a new numerical model to simulate the growth of hydraulic fracture with production and injection wells located nearby. Furthermore, validation of the numerical model was verified by comparing the calculated fracture geometry with the experimental observation. The study shows that (1) the stress value and orientation will be gradually altered around the production and injection wells; (2) fracture prefers to propagate towards injection wells when production and injection wells co-exist, and the fracture propagation trajectory will not be affected in the cases that only production or injection wells exist; (3) the fracture will be shorter and wider when production and injection wells co-exist or only injection wells exist, and the effects on fracture geometry can be neglected when only production wells exist. The obtained results provide new insights for understanding the fracture propagation problem in the field scale.
1. INTRODUCTION
Hydraulic fracturing technique has been widely used in the globe to stimulate low-porosity and low-permeability reservoirs with the aim of enhancing oil recovery. Thus, investigation of hydraulic fracture propagation behavior should be carried out with the objective of increasing the success rate during field operation. At present, a lot of researchers (Haddad and Sepehrnoori 2015; Kumar and Ghassemi 2016; Sobhaniaragh et al. 2016; Wu Kan et al. 2016; Gao Qi et al. 2017; Li Yang et al. 2017) are focusing on the simulation of fracture configuration during fracturing treatment. However, most of the work are completed under the assumption that pore pressure distribution is uniform and the direction of maximum and minimum horizontal stress are constant and orthogonal in the whole domain before fracturing the target well. In fact, the stress and pore pressure distribution in the formation could be much more complex as a result of the injection or production of fluid through pre-existed offset wells, which can affect the propagation path and size of fractures to some extent.
