Construction of Models that Simulate Oil Reservoirs

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Abstract
WYGAL, R.J., GULF RESEARCH and DEVELOPMENT CO., PITTSBURGH, PA. Introduction Many laboratory studies of porous media are based on experiments using test packs of sand, glass beads and other granular materials. More confidence can be had in the results of such studies if the test packs are known to have uniform properties throughout, to be mechanically stable and to be accurately reproducible. This paper presents a method by which such packs of a variety of shapes and sizes may be constructed using a particle distributor. Some factors which limit the usefulness of unconsolidated packs as a means for simulating reservoir rock are described. A method of overcoming these limitations, which involves artificial cementation of the packs, is presented. DEVELOPMENT Particles packed by the tamping or vibrating techniques are usually either non-uniform or mechanically unstable. An invention by Currie and Gregory overcomes these difficulties to some extent. The invention is based on the use of a stream of falling particles impinging on and passing through a distributor matrix of several layers of closely spaced spheres. The particles are well dispersed by numerous collisions with the spheres. They become homogeneously distributed at some distance below the distributor matrix and at that position are collected in the sample container. This apparatus, however, was found to be ineffective when small particles were used since small particles accumulate on the top surfaces of the spheres. An improved distributor matrix was made, first in the form of a stack of five sieves, and then in the more adaptable form of spaced layers of wire screen. Fig. 1 shows a longitudinal view through a five-layered distributor of eight-mesh wire screen. This device gives excellent results.* Fine particles pass through the distributor with very little hold up. The fine structure of the wire matrix with its many deflecting surfaces ensures good particle distribution. There are no dead areas immediately below the screen as were sometimes observed to occur below a matrix of spheres. Using such a device, 20–30 mesh sands were packed to a porosity of 32.1 per cent at rates varying from 0.17 to 6 lb/min. The lowest porosity achieved by tamping small increments of similar sands into a container was 33 per cent.Motion pictures at 3,000 frames/sec of the surface of a growing pack of 2–3/4 nun glass beads have helped to show the mechanism by which packs of low porosity are obtained. The beads, although packed at the roe of 5 lb/min, were observed to hit the pack surface singly, for the most part, and at well spaced points of impact. SPEJ P. 281^

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