Experimental Study on the Proppant Transport and Flowback in Hydraulic Fractures Considering Closure Pressure

ABSTRACT: Proppant flowback after hydraulic fracturing reduce fracture conductivity and damage equipment. Currently, the proppant flowback mechanisms are not well understood, and there is a lack of theoretical basis for selecting effective control methods. An integrated simulation device for proppant transport and flowback that can apply closure pressure has been developed. The macroscopic and microscopic processes of proppant flowback have been investigated, and the effects of perforation location and the matching relationship between fracture width and proppant size on proppant flowback have been clarified. The experimental results show that when particles within the fracture are stably bridged, the bridged particles form an irregular shape that blocks the flowback of particles from the deeper part of the fracture. The proppant above the perforation is more likely to flowback. In the non-bridging case, the flowback ratio of larger particle size proppant is higher. In the bridging case, stable bridging of near-wellbore particles can mitigate or terminate proppant flowback. During field operations, it is advisable to choose perforations in the upper part of the reservoir or avoid excessive sand dune height near-wellbore. When tailing with large particle size proppant, attention should be paid to the matching of proppant size and fracture width to achieve the effect of flowback control.