The Use Of Fluid-Loss Additives In Hydraulic Fracturing Of Oil And Gas Wells

Abstract

Abstract The theory of low fluid-loss hydraulic fracturing as a means of stimulation to oil and gas wells is presented. The fluid-loss properties of current fracturing fluids are shown by a demonstration of the API testing method. Fluid-loss test results are interpreted in comparing fracturing fluids. Introduction The method of fracturing to be discussed is not new. It is a process introduced to the oil industry in 1955 and was used sparingly at the outset, but has experienced tremendous growth in the past three years. The discussion will be divided into three parts. 1. Presentation of the theory of low fluid-loss fracturing. 2. Demonstration of the fluid-loss properties of current fracturing fluids. 3. Interpretation of fluid-loss test results in comparing fracturing fluids. HISTORY OF FRACTURING FLUIDS First, a brief discussion of the history of fracturing fluids. Fracturing began in 1949 with the initial fracturing fluids consisting of viscous fuel oils, gelled kerosene or napalm. During the next five years, little change took place in the nature of fracturing fluids. The first major change occurred in 1954 with the advent of low fluid-loss additives. Prior to this time, it was believed that viscosity was necessary to prevent sand outs; however, this was soon disproved by the use of fluid-loss additives in lease crude. Fracturing methods changed tremendously during the years following 1954, and in 1957 Howard and Fast presented a paper covering the mathematical treatment of the factors controlling fracture extension. Present-day fracture calculations are based largely on this work. Today, with economical and efficient fracturing fluids, many jobs utilizing an excess of 100,000 gal of fracturing fluids are being performed. In fact, a major oil company in 1959 fractured a well in South Texas in one stage using 180,000 gal of lease crude and put away 270,000 lb of sand with the aid of a low fluid-loss additive. The use of low fluid-loss additives has more than quadrupled in the last six years, and in 1960 over 125 million gal of fluid with low fluid-loss additives were pumped. THEORY OF LOB FLUID-LOSS FRACTURING First, the mechanics of fracture extension as illustrated in Fig. 1 should be investigated. The left portion of this figure shows the result of using high fluid-loss fracturing fluids.