High Permeability Fracturing With A Unique Proppant Flowback Prevention Technique

Abstract

High Permeability Fracturing With A Unique Proppant Flowback Prevention Technique Greg V. Cudney, SPE and Hossam El-Moniem, SPE; Schlumberger Dowell, and Mohammad Redha Mostafa, SPE, Kuwait Oil Company Copyright 1997, Society of Petroleum Engineers, Inc. Abstract Hydraulic fracturing of high permeability formations is an acceptable production enhancement method in damaged wells. Hydraulic fractures can be achieved that extend beyond the damage zone and provide a highly conductive flow path for productivity enhancement. As formation permeability increases, creating and propagating fractures become more difficult and economically less necessary. The creation of fractures that are less than 100 feet long and up to 1 inches wide after formation closure are achievable. Proppant flowback has been a concern as fractures have become wider and higher proppant concentrations have become more prominent. Recently a new method has been developed to reduce proppant flowback during well production. The technology uses a mixture of fibers and proppant to form a pack that is resistant to proppant flowback. This paper reviews the technical basis for high permeability fracturing and a proppant flowback prevention technique. A case history from Kuwait is presented. Introduction Kuwait Oil Company well A is located in the northern part of Kuwait (Fig. 1). Production is from a 800 millidarcy sandstone formation. A traditional 12 % HCl acid: 3 % HF acid treatment had been pumped in the well following a workover. The well productivity was reduced to uneconomic levels due to HF acid precipitates. A candidate recognition program indicated the well to be a potential candidate for hydraulic fracturing. However, several challenges are encountered when attempting to execute a hydraulic fracture in a high permeability reservoir. These challenges include obtaining effective fracture conductivity, and preventing the proppant in the fracture from back producing into the wellbore Hydraulic Fracturing Technology A classic fracture stimulation creates narrow conduits that reach deep into a formation — typically about 0.1 inches wide and up to 1000 feet long. Historically the emphasis for propped fracturing was on low permeability formations, less than 20 millidarcies (md), to provide productivity increases. However, as formation permeability increases, creating and propagating fractures become more difficult and economically less necessary. In high permeability reservoirs, formation damage is usually diagnosed as the major restraint on productivity and matrix acidization techniques are prescribed as the solution to productivity enhancement. But matrix acidizing cannot solve every problem. The volume of damaged rock may require uneconomical quantities of acid, the damage may be beyond the reach of a matrix treatment (1–3 feet), diverting acid to allow for complete coverage may be difficult, or the integrity of the reservoir may be damaged by dissolving the reservoir rock cementaceous minerals. An alternative strategy for stimulating high permeability wells has emerged: the creation of fractures that are less than 100 feet long and up to 1 inch wide after formation closure. Fracture Conductivity Numerous authors have discussed the application of hydraulic fracturing in high permeability wells. McGuire and Sikora describe how the increase in fracture length improves productivity in low permeability reservoirs. In high permeability wells, increasing the length of the fracture offers minimal improvement in productivity. Cinco-Ley described how productivity is determined by the dimentionless fracture conductivity. (1) Where kp = permeability of the proppant w = fracture width following closure, ke = effective permeability of the reservoir and xf = fracture half-length. P. 463^