Experimental study on the effect of fracture surface morphology on plugging efficiency during temporary plugging and diverting fracturing

Abstract

Temporary-plugging-and-diverting fracturing (TPD fracturing) is widely used to enhance hydrocarbon recovery from unconventional reservoirs. During TPD fracturing, diverters are injected to prevent the propagation of the previously formed fractures, then divert the fracturing fluid into the unstimulated zones. However, the influence of the fracture morphology on the diversion remains unknown. This study examined the characteristics of diversion under the influence of fracture undulation and roughness. The fracture surface was represented through the application of the 3D scanning and printing method. The digitized scan data is used to characterize the roughness and undulation of the fracture surface. Moreover, the width in the normal direction (normal width) of the fracture surface is used to measure the width of the flow channel in the fracture. A new method for describing the characteristics of fracture plugging location based on the normal width of the fracture is established. Besides, we chose a combination of particles with a diameter of 1 mm and fibers and studied its plugging behavior in a fracture with a width of 2 mm under the carrying of cross-linked guar fracturing fluid. Parallel experimental results suggest the presence of the characteristic plugging position, which is the narrow area inside the fracture. A fracture shape parameter quantitatively describing the characteristics of the region was established. It can be used to predict the inflection point in the pressure response of the diversion process. The research results show that the shape and distribution of the narrow areas in the fracture have a great impact on the plugging behavior. Even with similar average fracture width or the degree of normal width variation, there are significant differences in plugging efficiency. This study deepens the understanding of the plugging behavior of diverters in rough fractures.