Greater Effective Propped Areas Derived From Proppant/Partial Monolayer Combination

Abstract

Optimization of slickwater-fracturing treatments using recently developed ultralightweight (ULW) proppants to facilitate proppant placement throughout the entire fracture area has found success. Wells treated with newly developed ULW proppants and refined placement techniques are experiencing stimulation increases (as much as 700%). The observed stimulation increases in wells stimulated by BJ Services with these ULW proppants have yielded payouts in a few weeks or months compared to years under previous methods. The resurgence of low-cost slickwater-fracturing treatments in wells that have been uneconomical to fracture with conventional methods has led to implementing new technologies to maximize the effective propped-fracture area. The reduced settling tendencies afforded by the ULW proppants have proved beneficial in that endeavor. A desire to maximize the conductivity of the fracture within that effective area has led to rekindled interest in the decades-old theory of partial proppant monolayers. Before the use of ULW proppants, fracturing-mechanics and -design experts tried to achieve desired fracture conductivity through the creation of fractures with partial monolayers of prop-pant but had been unsuccessful because of an inability to obtain uniform and complete coverage of the fracture; loss of fracture width as a result of proppant embedment; potentially deleterious non-Darcy flow effects; and, in the case of untreated walnut hulls, insufficient proppant strength to support the load. In 1959, SPE paper 1291-G authors S.R. Darin and J.L. Huitt discussed the results of a study on the factors affecting fracture conductivity, demonstrating that there is an areal proppant concentration less than that of a full proppant monolayer in which the resulting conductivity is much higher than that of a full monolayer. In 1970, an SPE Monograph titled Hydraulic Fracturing, Volume 2, by G.C. Howard and C.R. Fast examined the conductivity benefits associated with partial monolayers but noted that, when using conventional methodologies, a partial monolayer had been very difficult to achieve in the field, particularly in a vertical fracture. The authors suggested that monolayers could be attained in the field by placement of a full monolayer consisting of a blend of proppant particles and oil-soluble resin particles, subsequently dissolving the resin particles to leave only a partial proppant monolayer. Contemporary experts have treated partial proppant monolayers as a technical curiosity but dis-miss the concept as having not been proved to be widely successful. The advent and early success of ULW proppants in slickwater fracturing applications have provided evidence of longer effective propped fractures where the partial-monolayer technique was employed. Evaluation of these results indicates that the use of ULW proppants overcomes previous limitations for obtaining partial proppant monolayers.