Optimization Of Volumetric Fracturing Cluster Spacing In Horizontal Wells Of Lucaogou Tight Oil Reservoir

In recent years, with the development of China's tight oil exploration and development technology, we have obtained industrial oil flow breakthrough in Lucaogou tight oil formation of Junggar basin, which shows a good development foreground. The volume fracturing of horizontal wells is the key technology for the development of tight oil reservoir. Due to the limitation of the development level of tight oil fracturing theory, the optimization design method of volume fracturing in tight oil reservoirs is seriously lagged behind. Especially, the understanding of crack propagation and stress interference mechanism is not enough, which leads to the blindness of the design of cluster spacing parameter, to a certain extent, it has restricted the effective implementation of the volume fracturing technology of tight oil reservoir. In this paper, based on the interference mechanics mechanism of hydraulic fracture, we did a systematic study on the design of cluster spacing optimization. And the hydraulic fracture stress interference model is established by using constant displacement discontinuity method, combined with the mechanical conditions of SRV formation, influence factors of crack interference and cluster spacing to optimize the design, the following important conclusions were obtained:(1)The young's modulus of rock has a great influence on the geometry of the fracture, the potential reform area of the reservoir is restricted by the horizontal stress difference and the net pressure inside the seam, high net pressure can help to increase the SRV, for a particular reservoir, there is an optimal value of cluster spacing;(2) Based on stress interference model, the principle of Stepwise fracturing, Two step fracturing, Synchronous fracturing, Zipper fracture and Modified zipper fracturing in tight oil field were revealed;(3) Based on the cluster spacing optimization criterion, the optimum design of cluster spacing in the case of field volume fracturing is carried out, considering the influence of the horizontal stress difference and the net pressure of the construction, the cluster spacing of well HWX is optimized as 17-33m.The research results of this paper have important theoretical value and practical significance to improve the efficiency of tight oil exploration and development and to guide the optimal design of tight oil reservoir.