Investigation of Influencing Factors on Reservoir Damage Caused by Polyacrylamide Fracturing Fluids with Different Gel Breaking Degree

Polyacrylamide fracturing fluid is a common working fluid suitable for fracturing development of low permeability oil and gas fields at home and abroad. In the application process, due to incomplete gel breaking, untimely flowback and the reaction between polyacrylamide fracturing fluid and reservoir material, reservoir damage after fracturing is often caused, which is an influencing factor that must be considered in fracturing development of oil and gas fields. In this paper, the reflection relationship between molecular coil size in fracturing fluid solution with different decomposition gel breaking and gel breaker concentration was established by means of rheometer, laser dynamic light scattering and atomic force microscope. The compatibility of different metal cations in the solution with gel breaking solution was investigated by ampoule aging experiment. It was determined that iron ions were the main controlling factor leading to the complexation and precipitation of polyacrylamide molecules under the ion concentration of formation water. Furthermore, the influence of molecular coil morphology and size in gel breaking solution on fracture flow conductivity was investigated by physical simulation experiment of core flow. Finally, by studying the interaction mechanism between polyacrylamide fracturing fluid and reservoir fluid, the influence mechanism of fracturing fluid with different occurrence states on reservoir physical properties and fluid flow is explored, which provides a basis for the development of fracturing fluid and the improvement of gel breaking technology.