Abstract

A new method has been developed to prevent proppant flowback from a propped hydraulic fracture. The method consists of mixing the proppant with fiber elements before pumping the proppant into the fracture. The results of an experimental program, in which the goal was to better understand the mechanics of the reinforcing fiber on the proppant pack, are presented. The effects of fiber and sand properties on sandpack strength have been studied for an optimal use of the fiber. A macroscopic model has also been developed based on fiber and proppant properties. Laboratory tests on proppant with a low fiber content indicate a favorable agreement between the model prediction and the flowback tests

Introduction

Backproduction of proppant from propped hydraulic fractures can be a continuing operational problem throughout the life of the well. Recently a new method has been developed to reduce proppant flowback during well production. The method consists of mixing the sand with glass fiber elements (typically 12 mm long and 20 m in diameter) before pumping the proppant into the fracture. The proppant pack reinforced by this method is much more stable to fluid flow without significant pack permeability reduction.

Reinforcement of soils with tensile-resisting fibers is a common technique in civil engineering. Several methods, e.g., continuous filament or mesh element inclusion, have been successfully used for soil reinforcement. The principle of this type of reinforcement is based on the interaction between fibers and soil providing an additional cohesion to the soil. However, a very limited use of short fiber inclusions has been made for soil reinforcement.

For hydraulic fracturing, short fiber reinforcements were found to be the most effective because of compatibility with the fracture geometry. A description of a fiber-reinforced failure criterion is presented in this paper. In particular, experimental results are shown to demonstrate the effect of fiber properties on proppant pack stability. Experimental Tests The laboratory model was set up to study the stability of a reinforced proppant pack at the perforations with a given fracture geometry. It consisted of a set of polycarbonate glass plates with a steel cylinder at the outlet simulating the perforation tunnel. The cell was filled with reinforced sand, and then fluid was forced to flow through the sandpack with no confining stress applied to the proppant pack.

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