Lightweight proppant and method of making same

Abstract

A method of forming lightweight, high-strength proppants is disclosed, comprising the steps of: homogeneously blending at least one ceramic precursor and at least one pore former; pelletizing the blend to form microspheres; heating the microspheres to less than sintering temperatures, to evaporate volatile components and pyrolyze fugitive components; further heating the microspheres to temperatures sufficient to sinter the continuous phase of the ceramic precursor, to form sintered particles; and then forming the sintered particles into generally spheroid proppants. The generally spheroid proppants, which have preferably been sintered to near theoretical density, may then be coated. Heating of the microspheres may comprise a series of heating stages.

Description

FIELD OF INVENTION [0001] Lightweight particles, commonly referred to as proppants, are provided for use in oil and gas wells. The particles are useful to prop open subterranean formation fractures. BACKGROUND OF THE INVENTION [0002] Hydraulic fracturing is a process of injecting fluids into an oil or gas bearing formation at sufficiently high rates and pressures such that the formation fails in tension and fractures to accept the fluid. In order to hold the fracture open once the fracturing pressure is released, a propping agent (proppant) is mixed with the fluid and injected into the formation. Hydraulic fracturing increases the flow of oil or gas from a reservoir to the well bore in at least three ways: (1) the overall reservoir area connected to the well bore is increased, (2) the proppant in the fracture has significantly higher permeability than the formation itself, and (3) highly conductive (propped) channels create a large pressure gradient in the reservoir past the tip of ...

AI Technical Summary

Benefits of technology

The present invention provides a composition and method for making high-strength, lightweight proppants with repeatable accuracy. The proppants are made of ceramic materials with a high degree of porosity achieved through the use of pore formers. The ceramic precursors used can be selected from a variety of sources such as alumina, aluminum hydroxide, boehmite, and silica. The pore formers used can have a high thermal reactivity or be inert at elevated temperatures. The ceramic precursors and pore formers are blended and then microspheres are formed by heating them to low temperatures to evaporate volatile components and pyrolyze fugitive pore formers. The microspheres are then heated to sinter the ceramic precursors to near theoretical density. The resulting proppants have a high degree of porosity and compressive strength. The method allows for the economical manufacture of proppants with repeatable accuracy.

Problems solved by technology

If proppants fail to withstand the closure stresses of the formation, they disintegrate, producing fines or fragments, which reduce the permeability of the propped fracture.

Its use, however, is limited to depth with closure stresses of 41 MPa.

Proppants manufactured according to this invention are not much stronger than the core particle itself and are, due to the cost of the resin and hollow glass spheres, quite expensive to manufacture.

The main disadvantage of this invention is that the proppants still have a relative high apparent specific gravity.

The use of the proppants, therefore, is limited to shallow wells.