Study on Fracture Propagation and Parameter Optimization for Multi-Cluster Fracturing Using Temporary Plugging Technology——A Case Study in the Tight Oil Reservoir, Sichuan Basin

Le résumé fourni par la source

Abstract Multi-cluster staged fracturing is an important measure to exploit unconventional resources. During fracturing process, the fracturing fluid mainly flows into few clusters, resulting in uneven fracture propagation. The temporary plugging technology is generally applied to balance the fluid distribution into each cluster within a stage. However, plugging timing, frequency, and amount of plugging balls have not been clearly revealed. In this paper, a model of three dimensional (3D) fracturing model is established, and this model is verified by the indoor fracturing experiment and traditional analytical solution. The multiple fracture propagation under different perforation parameters and temporary plugging parameters is studied, and the variation coefficient of fracture length is applied to quantitatively evaluate the fracture uniformity. The simulation results show that the inner fractures are more easily suppressed by outer fractures due to stress interference. When the plugging balls are used, the outer fractures will be preferentially blocked, and the fracturing fluid into these clusters begins to decrease. In this case, the subsequent fluid will flow into the inner fractures to enhance their fracture length, finally achieving even stimulation. When the number or diameter of perforation holes is lower, the more uniform fracture geometry can be obtained due to limited-entry effect, and the optimal perforation number is 6 per cluster, and the diameter of perforation hole is recommended to not exceed 8mm. When there are 5 clusters within a stage, only one plugging operation is needed, and for 6 or 7 clusters, two plugging operations are necessary to ensure the uniform fracture propagation. With the increase of number of plugging balls, the variation coefficient of fracture length first decreases and then increases, and the optimal amount of plugging balls is 16-20. It is suggested to pump the plugging balls when 60-70% of fracturing fluid is injected. This method proposed in this paper is applied in Well X1 in the Sichuan Basin, China, and the variation coefficient of fracture length is controlled less than 10%, obtaining good application results.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.