Use Of High-Strength Ceramic Beads For Propping Deep Hydraulic Fractures
Authors: Sarda Jean Paul 
Published: December 2007

Abstract
Ceramic beads have been tested to be used as propping agents in a hydraulic fracturing process. propping agents in a hydraulic fracturing process. This material is zirconium oxide based. Its main properties are described. Laboratory tests on properties are described. Laboratory tests on various beads concentrations show a good conductivity of the proppant under compressive stresses of at least 15,000 psi. Good results also have been obtained in permeability tests at high temperature and with corrosive fluids. The influence of mesh size and shape is discussed. These beads have been injected in several deep wells. The post-treatment observations confirm their good strength.

Introduction
The success of a hydraulic fracturing operation is strongly conditioned by the possibility of maintaining a high enough permeability within the created fracture.
In a classical hydraulic fracturing process (without acidification), this permeability is obtained by keeping the fracture open with a granular material. This material, called propping agent, should exhibit the following properties: good mechanical strength, good chemical stability, acceptable density. It also should be pumped easily down wells.
The propping agents mostly used ace siliceous sand and glass beads. They usually are convenient for wells drilled at depths smaller than 3000 m (10,000 ft). However, the necessity of new materials suited to deeper wells has been recognized for several years. New propping agents have been set forth: sintered bauxite particles, "oxide ceramic proppants," and resin coated sand. proppants," and resin coated sand. A new propping agent, different from those cited herein, has been studied and tested in Europe during the last years. This is called hereafter "zirconium oxide beads" although this denomination does not define completely the chemical composition of the constitutive material. Tests have been performed on these ceramic beads by the laboratories of IFP (Institut Francais du Petrole) and SEPR (Societe Europeenne de Produits Refractaires), which together have patented the beads and their use for hydraulic fracturing. These beads are suitable for injection in deep layers producing hydrocarbons.
The beads' main physical geometrical and mechanical properties are first described. Subsequently defined are the two series of tests performed in order to evaluate their specific use in performed in order to evaluate their specific use in hydraulic fracturing: hydraulic conductivity measurements under stresses and at several beads concentrations, permeability measurements in stress corrosion conditions or after chemical treatment. The results obtained on several mesh sizes are shown with reference to variations brought by the sphericity characteristics of the beads.
These zirconium oxide beads have been used on several wells during the last years, and the available information concerning these field tests are presented. presented. PHYSICAL, GEOMETRICAL, AND MECHANICAL PHYSICAL, GEOMETRICAL, AND MECHANICAL PROPERTIES OF ZIRCONIUM OXIDE BEADS PROPERTIES OF ZIRCONIUM OXIDE BEADS The hereafter described properties refer mainly to standard type zirconium oxide beads (Type S). The measurements have been made in the SEPR laboratory.
The structure of the ceramic material is semicrystalline. A well crystallized Baddeleyite skeleton (monoclinic Z O) is embedded in a fused silica matrix (cf photograph on Fig. 1). A chemical analysis expressed in terms of equivalent oxide weight shows that the components axe: Z O + H O (68,7%), S O (31,2%) and T O + Fe O (0,1%). There are also small quantities of calcium, magnesium, and aluminium.
The material conceived for hydraulic fracturing purposes consists of beads. Their mean density is purposes consists of beads. Their mean density is 3.76.