Experimental study on the evolution characteristics of the conductivity of hydraclic fractures in shale reservoirs

The development of unconventional oil and gas resources such as shale gas and shale oil is highly valued by countries all over the world. However, shale reservoirs have very poor physical properties, and the reservoirs need to be hydraulically fractured to achieve high oil and gas production. At present, there are few studies on the dynamic evolution law of the conductivity characteristics of hydraulic fractures in shale reservoirs. In this paper, taking the conductivity experiment system of unconventional oil and gas reservoirs as an example, the evaluation experiment of fracture conductivity evolution characteristics was conducted. Studies have found that the conductivity of fractures during hydraulic fracturing will first increase and then decrease. The entire experimental phase can be divided into a rapid growth stage, a slow decline stage and a steady change stage. As the particle size of the proppant increases, it will effectively support the fracture avoidance, resulting in a gradual increase in fracture conductivity. When the proppant particle size in the fracture increases from 10 mu m to 40 mu m, the fracture conductivity will increase from 7.05 mu m(2).cm to 18.93 mu m(2).cm. Moreover, as the concentration of sand paving increases, the conductivity of fractures will first increase and then decrease. This is mainly because the increase in sand paving concentration will not only effectively support but also fill up the crack space to a certain extent. Considering the cost and fracturing effect comprehensively, the concentration of sand spread in the fracture is best controlled at 5-10 kg/m(2). Finally, the study also found that the increase in the viscosity of the fracturing fluid will increase its flow resistance, resulting in a decrease in the conductivity of the fracturing fluid. For this reason, it is better to control the viscosity of fracturing fluid to 5-10 mPa.s.