Parameter optimization and field test of nano variable-viscosity slick water fracturing in Changqing shale reservoir

Abstract

After the development of the directional and horizontal wells of Chang 7 shale reservoir in Ordos Basin, the formation pressure decreases rapidly and the production decreases naturally. There is an urgent need for fracturing fluid with oil displacement and enhancing oil recovery (EOR) function, and the on-site fracturing process parameters are optimized. Through laboratory experimental research, nano variable-viscosity slick water has the advantages of high drag reduction, strong sand-carrying, and imbibition oil displacement capacity, which significantly improves the deficiency of sand-carrying and oil displacement performance of conventional slick water. At the same time, the numerical simulation shows that when the injection displacement is 18 m3/min, the cluster spacing is 5 m, the number of perforation clusters is 7 and the sand addition intensity is 3 t/m, the fracturing reconstruction volume can be maximized, which is the optimal parameter for fracturing construction of Chang 7 reservoir. Combined with nano variable-viscosity slick water and optimal construction parameters, field fracturing tests were carried out in 13 wells, including 9 directional wells and 4 horizontal wells; The average daily oil production of horizontal wells is 17.77 t, the cumulative oil production is 377.33 t, and the production is increased by 10∼15 times. It is a new and effective method for the development of Changqing shale reservoir to combine the nano variable-viscosity slick water system of strong oil displacement and sand-carrying capacity with high displacement construction technology.