Influence of Stress Field Evolution on Refracturing of Horizontal Wells

ABSTRACT: After the initial fracturing, the stress field around the wellbore will become more complex, and even stress reversal will occur. The depletion of oil and gas will lead to the reduction of reservoir pore pressure, and then increase the effective stress of the reservoir, leading to the decreases of fracture conductivity and production, thus refracturing is often needed. Most of the studies focus on the initial fracturing of the reservoir, but there are few investigations on refracturing. In this paper, based on the global Cohesive zone model, the finite element method is used to simulate the initial fracturing and oil and gas production and extract the stress field distribution. Then the stress field is introduced into the new model to simulate the initiation and extension of the fracture during refracturing. The results show that under the influence of the initial fracturing, the stress concentration problem exists in the refracturing area, and the uniform repeat reconstruction can be achieved by adjusting the perforation position or combining it with the temporary plugging process. 1. BACKGROUND Tight oil exploration has broad prospects and has become the key object of unconventional oil and gas development, with great exploitation potential(Bing et al. 2016). The large section and multi-cluster hydraulic fracturing technology of horizontal wells is an effective means to develop low permeability oil and gas fields. With the progress of production, the production capacity is gradually reduced, and the refracturing operation needs to be carried out (Zhou et al. 2017). The implementation of refracturing technology measures can effectively expand the reservoir reconstruction volume and supplement formation energy, improve the single well production and extend the stable production period. But different from the initial fracturing, the stress field around the wellbore is disturbed by the initial fracture, and the long-term production has an impact on the formation pressure, which leads to a more complex formation environment for refracturing(Xu et al. 2020).