Gravel Packing Sand Quality-A Quantitative Study
Authors: Zwolle Simon , Davies David R. 
Published: December 2007

This paper discusses the results of a study of gravel packing sand quality. It shows that the amount of fines packing sand quality. It shows that the amount of fines generated in a gravel crush-resistance test, a method proposed to the API, depends on roundness, sphericity, proposed to the API, depends on roundness, sphericity, average grain diameter, and grain multicrystallinity. A straightforward technique to determine these properties accurately is also described.

Introduction

The use of high-quality gravel packing sand has been recognized as an important factor for placing unimpaired gravel-pack completions. For example, Ottawa gravel is well known for its excellent properties for this purpose. However, it has not always proved possible to purpose. However, it has not always proved possible to obtain an adequate supply of high-quality gravel packing sand because of the remoteness of some international operations. Therefore, a study was initiated to screen alternative, more readily available gravel packing sand supplies. This paper discusses some of the methods used in the study; it complements the valuable work being performed by the API subcommittee on the evaluation of performed by the API subcommittee on the evaluation of well-completion materials. During this study, it was found that a more pertinent method of characterizing the gravels was required in addition to the conventional tests-sieve analysis, mud acid solubility, etc. A technique has been developed based on preparing thin-sections and representative photomicrographs preparing thin-sections and representative photomicrographs of the gravels. It allows the determination of the presence of fractures and grain multicrystallinity; grain presence of fractures and grain multicrystallinity; grain roundness and sphericity may be determined at the same time. In addition, two tests were examined to rank gravels from different sources for their resistance to fines generation. Minimal fines generation during gravel-pack placement is a basic requirement for unimpaired placement is a basic requirement for unimpaired completions. Finally, an attempt has been made to develop a basic understanding of the fines-generation process. This has resulted in a general correlation equation, which is used to explore the characteristics required for a high-quality gravel.

Use of Thin-Sections and Photomicrographs

Thin-sections and photomicrographs were introduced to determine roundness and sphericity and to detect the presence of fractured and multicrystalline grains in the presence of fractured and multicrystalline grains in the sample. This involves the preparation of standard geological thin-sections from the gravel grains. Thin-sections are prepared by embedding the grains in blue epoxy resin, followed by grinding the sample until a layer approximately 30 m thick remains. These thin-sections are then examined under a microscope in transmitted normal and polarized light, and representative photomicrographs are taken. photomicrographs are taken. Fractures present in the grains will be revealed clearly in transmitted normal light. Some of the fractures may have been induced during the grinding of the sample. If this occurs, a large fraction of the sand grains is usually damaged and remnants of the grinding material are found embedded in the fractures. Illumination of the samples with polarized light reveals the mono- or multi-crystallinity of the gravel grains. The color of a monocrystalline grain viewed with crossed nicols is uniform. By contrast, multicrystalline grains are not uniform in color; the different crystals within the grain will appear to have different colors, as their crystalline axes have different orientations relative to that of the polarized light. Determination of the roundness and sphericity may be made at the same time. This is conveniently done with visual comparators.

JPT

p. 1042