Shale reservoirs have very low original permeability and no economic productivity under natural conditions. Many filed observations show that large hydraulic fracturing is the most effective ways to develop shale reservoirs efficiently. However, there are few studies on the optimization of fracture cluster number in fractured horizontal wells in shale reservoirs. In view of this problem, the multi-well numerical model of multi-stage fractured horizontal wells is established by using the unstable seepage theory, and a set of optimization method of fracture cluster number of multi-stage fractured horizontal wells in shale reservoir is put forward on the principle of full utilization of reservoir. The results show that when the number of fracture clusters in multi-stage fractured horizontal wells in Changji oil field is more than 80, the cumulative increase trend of oil production tends to be flat. It can be determined that the reasonable cluster spacing range is about 15m∼20m, and the number of fracture clusters is 70∼80. According to the theoretical model with an optimal number of fracture clusters of 75, the cumulative oil production of fractured horizontal wells in shale reservoirs in Changji oilfield was calculated to be 25150 m3. This work can provide theoretical reference for the design of fracture clusters in fractured horizontal wells in shale reservoirs in Changji oilfield, Xinjiang.
Recently, with the great success of shale oil and gas resources exploitation in North America, the goal of global oil and gas exploration and development has shifted the attention to shale reservoirs. As the permeability of shale oil reservoir is in the milli - to micro-Darcy range, there is no economic productivity under natural production conditions. Many field applications and researches have indicated that productivity of unconventional reservoir can be increased by employing the large-scale fracturing technology in horizontal well. Currently, domestic and foreign scholars have carried out some related research work on the seepage theory of multi-stage fracturing horizontal well.
Giger (1985) studied the seepage procedure of fracturing horizontal wells for the first time and pointed out that horizontal wells are a good tool to develop heterogeneous reservoirs. He participated in the study of the seepage model and pressure drop distribution law of fracturing horizontal wells in low permeability reservoirs.
Horne (1995) established a physical and mathematical model for seepage in multi-stage fracturing horizontal wells, solved the model by using the superposition principle, and analyzed the interference effect between multiple fractures, also divided multi-stage fracturing horizontal wells seepage flow stage.
