Oxide Ceramic Proppants For Treatment Of Deep Well Fractures
Authors: Neel E.A. , Parmley J.L. , Colpoys P.J. 
Published: December 2007

To meet the need for proppants that provide high fracture flow capacity in multilayer placement under high closure pressures in low-permeability formations, a new oxide ceramic proppant has been developed. This proppant is characterized by a high degree of sphericity, a uniform composition, and chemical inertness. Its specific gravity is lower than normally obtained with materials of this type.

A laboratory apparatus is described that permits the measurement of permeability and fracture flow capacity of various proppant systems. The laboratory data generated show that the oxide ceramic proppant when placed in a multilayer distribution provides superior fracture flow capacity to similar concentrations of sand and other commercially available proppants. proppants

Introduction

With the continued emphasis on oil and gas production to meet the energy demands, stimulation production to meet the energy demands, stimulation through the use of hydraulic fracturing has proved to be a very important method of increasing productivity. As well depths increase and low-permeability productivity. As well depths increase and low-permeability formations are encountered, the natural production rate of many of these formations is economically unacceptable, and therefore, some method of stimulation must be performed to produce the well at a commercial rate. To achieve long-term productivity from deep, tight formations, hydraulic fracturing is often selected as the best method for obtaining acceptable results.

Hydraulic fracturing as commonly practiced involves pumping a viscous, proppant-laden fluid down the wellbore with sufficient pressure to overcome the tensile strength of the formation and the overburden weight. Once the fracture is initiated, the type and size proppant used and the placement of this proppant is of great importance. The underground environment under which the proppant must perform also considered.

Sand, usually in the particle size on the order of 20 to 40 mesh (0–0331 to 0.0165 in. in diameter), was widely used initially as a propping agent. As the art of hydraulic fracturing underground formation progressed, it became more and more common to use a progressed, it became more and more common to use a propping agent comprised of larger particles to propping agent comprised of larger particles to increase the fluid-carrying capacity of the fracture. Some of the early work, particularly when the formation fractured was hard, taught that the maximum fluid flow capacity of the fracture could be obtained when a partial monolayer of propping agents was deposited in a fracture and larger sizes of propping agents then were considered highly propping agents then were considered highly advantageous in increasing fracture flow capacity.

However, now it generally is held that without very careful consideration to fluid viscosity, particle size, particle density, pump rate, etc., it particle size, particle density, pump rate, etc., it is extremely difficult to perform a fracturing treatment in such a way that a partial monolayer distribution results. Generally, it is accepted that a packed multilayer is formed. A packed multilayered distribution is one in which several layers of particles form between the surfaces of the fracture particles form between the surfaces of the fracture during the injection period.

Although sand is the most widely used commercial propping agent because it is inexpensive, readily propping agent because it is inexpensive, readily available, and chemically inert, its major detriment is its low crush resistance. When the compressive limit of sand is exceeded, the material crushes. Such crushing continues until enough small particles are produced either to support the load or to plug the fracture. If small particles support the load, fracture flow capacity is reduced as the fracture width is reduced. Accordingly, the flow capacity of the fractures propped by sand is low, thereby defeating the initial purpose of the propping agent.

Malleable propping agents such as plastics, walnut hulls, and/or aluminum simply deform in a pack and tend to close the spacing provided for fluid pack and tend to close the spacing provided for fluid flow through the fracture and, therefore, are totally unacceptable in a pack distribution.