A numerical model for fractured horizontal well and production characteristics: Comprehensive consideration of the fracturing fluid injection and flowback

Currently, many investigations on fractured well productivity are conducted. However, all this productivity studies are conducted based on the initial pressure and fluid distribution. In this work, taking the reservoir damage caused by fracturing fluid and the effect of fracturing fluid injection on pressure and saturation into consideration, a flow model of multistage fractured horizontal well is built, which is composed of fracturing fluid injection model and fracturing fluid flowback and production model. Numerical solving method is utilized to solve the model and model verification are presented through comparing with the test results of 12 fractured well. The effects of fracture fluid injection rate and fracturing fluid viscosity on pressure and saturation at the end of fracturing fluid injection are analyzed. And the effects of the reservoir oil viscosity, porosity, permeability, heterogeneous and reservoir damage on flowback and production characteristic are analyzed. The results show: (1) The distances of saturation and pressure variation area from the fracture are respectively 10 m and 20 m after the fracturing fluid injection is finished. When the fracturing fluid viscosity increases from 10 mPa s to 30 mPa s, the distance of pressure variation area from the fracture decrease. But the pressure and saturation near the hydraulic fracture increases. When the injection rate increases from 0.28 m(3)/min to 28 m(3)/min, the fracture length increases and the distances of pressure and saturation variation area from the fracture increase. The pressure near the fracture with a high injection rate is larger than that with a small injection rate. (2) With the development of reservoir, the water flow rate and water cut decreases, and the oil flow rate increases firstly and then decreases. When the reservoir oil viscosity increases from 1.5 mPa s to 2.5 mPa s, water cut increases. The maximum oil flow rate decreases from 16.4 to 6.2 m(3)/d. With the increase of reservoir permeability, the water cut decrease. When the reservoir porosity increases, the oil flow rate, water flow rate and cumulative fluid volume increase. While, the water cut decreases with the increase of reservoir porosity. When the residual resistance factor (RRF) increases from 1 to 1.08, the oil flow rate of when the RRF equals 1 is slight larger than that of when the RRF equals 1.08. The reservoir damage has slight effect on the water flow rate and water cut. (3) The development of heterogeneous reservoir is poorer than that of homogeneous reservoir when the development conditions are the same. This work provides a more accurate method to investigate the flowback and production characteristics of fractured well.