The Sand Intensifier---Its Development And Application To Fracturing

Abstract

Introduction A major deficiency in fracturing with foam or methanol carbon dioxide systems has been the limitations on sand concentration imposed by surface equipment. A Sand Intensifier has been developed to facilitate ultra-high sand concentrations. The development and field application of an initial prototype machine are discussed. Refinements and later developments have broadened the range of treating pressures and rates substantially, and thereby increased the number of wells that could be stimulated using intensified foam frac, Details of treatments and corresponding results described later indicate better performance than other fracturing techniques. Introduction The properties of foam have resulted in its widespread use as a fracturing fluid. Low fluid loss, low friction and excellent load fluid recovery are characteristics of foam documented in the literature(1.2.3). It has also been noted that foam has excellent sand-carrying capabilities(1.2.3). However, surface mechanical limitations have largely prevented utilizing this capability(3,4) and maximum concentrations to date have been 300 kilograms per cubic metre (2,5 ppg) of foam, At these concentrations, partial monolayers of proppant are usually deposited. In formations where crushing or embedment makes partial monolayer propping unsuitable, foam fracturing has not been successfully applied, Several techniques have been developed to overcome low concentrations in the fracture. One that has been widely used is combination foam liquid fracturing(4). Another is to gradually increase liquid rate near the end of the job. This decreases foam quality, increases sand concentration in the foam and provides a packed fracture near the wellbore. Alcohol mixed with carbon dioxide has been used to treat fluid-sensitive formations for many years(5). As with foam, a primary disadvantage of this type of treatment is low concentrations at the formation face and in the fracture. Work began three years ago on the process that would increase sand concentrations to facilitate packed fractures in foam and other fluids. The following discusses the development and field testing of a prototype Sand Intensifier, the application of such a tool to well stimulation and the results of treatments utilizing higher concentrations. Development Once the basic requirements of an intensifier were established namely to discharge 0.5 m3/min (3.1 BPM) outlet and to increase sand concentrations two or threefold, a low-pressure (1000 kPa or 145 psi) laboratory model was fabricated. Various configurations of rotor, seals and bearings, inlets and outlets were tested. Rotor speed and size were also varied. Tests such as that described in Table 1 provided enough encouragement to proceed with a high-pressure field prototype. By February 1978, adequate information had been accumulated to begin design of the high-pressure model. The machine was fabricated and laboratory tested in the spring of 1978, The first job was conducted on June 28, 1978, on the well CDC Retlaw 6-20-13-18-W4M, Field hookup was basically as described in Figure 2, with the exception that reflux water was piped to a separate tank, This meant that exact balances of water and sand could be made and the flowmeters double checked.