Experimental Study of Proppant Transport in Complex Fractures with Horizontal Bedding Planes for Slickwater Fracturing

Abstract

Summary The use of hydraulic fracturing has taken off over the past decade, and the importance of efficient proppant placement in fractures has increased accordingly. Connection with weak-formation bedding planes brings about distinctive fracture propagation and development. This might hinder hydraulic fractures from extending in a vertical direction, yet they might instead propagate in a horizontal direction after the existing bedding planes. The bedding plane introduces additional hydrocarbon flow path during the recovery process. This naturally leads to proppants traveling in the horizontal section of the fractures. Optimal proppant delivery and conductivity in bedding planes directly relate with effective fracture height and well performance. This paper focuses on understanding horizontal movement and delivery of proppants and their distribution in vertical and horizontal fractures on the basis of experimental work. The size of proppants is one of the key determining parameters when calculating uplift and settling velocity. They travel farther into the fracture because they settle slower with less gravitational effect. Fine mesh is highly recommended to effectively deliver proppant to the horizontal bedding plane. Large proppants have to rely on the critical bed height to move into the bedding plane sitting on top of the vertical fracture. A higher injection rate promoted bedding-plane proppant delivery in the inverted T-shape case because it opened up a longer and larger area for particles to settle. Excessively strong turbulent flow generated by two inlet cases prevented proppants from settling and seeping into the bedding plane. Continuous mixing and agitation disturb proppants from settling. They limited additional coverage area expansion in the bedding plane. Moreover, inlet design shows little effect in the T-shape, yet having more injection points improves proppant placement in the bedding plane. Direct injection to the bedding plane surprisingly did not affect much in the T-shape case. Overall, only a small percentage of proppant can travel into the bedding plane for both T-shape and inverted T-shape-fracture geometries.