Sintered spherical pellets useful for gas and oil well proppants

Abstract

Sintered, spherical composite pellets having high strength and low density, are described, along with processes for their manufacture. One method includes forming a green pellet from a mixture of clay, bauxite or a clay-bauxite mixture with a sacrificial phase such that upon sintering of the pellet, the sacrificial phase is removed from the pellet. The use of such sintered pellets in hydraulic fracturing of subterranean formations is also described.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to oil and gas well proppants and, more particularly, to sintered proppants in a broad range of applications. [0002] Oil and natural gas are produced from wells having porous and permeable subterranean formations. The porosity of the formation permits the formation to store oil and gas, and the permeability of the formation permits the oil or gas fluid to move through the formation. Permeability of the formation is essential to permit oil and gas to flow for production of the well. Sometimes the permeability of the formation holding the gas or oil is insufficient for economic recovery of oil and gas. In other cases, during operation of the well, the permeability of the formation drops to the extent that further recovery becomes uneconomical. In such cases, it is necessary to fracture the formation and prop the fracture in an open condition by means of a proppant material or propping agent. Such fracturing is usually ac...

AI Technical Summary

Benefits of technology

The present invention relates to a new type of proppant for use in oil and gas wells. The proppant is made from natural materials and has a unique structure that allows it to withstand high levels of pressure and crushing. It is made up of spherical pellets or particles that have a specific gravity of about 1.80 to about 2.50. The proppant is strong enough to be used in shallow wells and has a moderate density. It is effective at closure stresses of up to about 5000 psi. The proppant is made from clay, bauxite, or clay-bauxite mixtures and a sacrificial phase material that is removed during the sintering process. The ingredients for forming the proppant have an average particle size of less than about 15 microns. Overall, the new proppant has unique properties that make it a better choice for oil and gas wells.

Problems solved by technology

Sometimes the permeability of the formation holding the gas or oil is insufficient for economic recovery of oil and gas.

In other cases, during operation of the well, the permeability of the formation drops to the extent that further recovery becomes uneconomical.

However, these high strength propping agents have high densities, i.e. apparent specific gravities above 3.4 g / cc, and require high viscosity pumping fluids or high pumping rates to keep them in suspension during the pumping operation.

The use of higher viscosity pumping fluids required to transport the high density proppants can cause more damage to the formation fractured face and the resulting propped fracture as residues from the high viscosity fluids become concentrated along the fracture face during pumping and if not adequately broken remain within the propped fracture, therefore reducing the propped fracture permeability.

Because of the disadvantages associated with the use of high viscosity fracture fluids, the use of high density proppants are limited to use in wells where high strength is the controlling attribute.

However, when the alumina content is reduced too much there is generally a concomitant increase in silica content which leads to a rather significant loss of strength.

Therefore, efforts to develop an even lighter proppant by using lower alumina content materials generally have failed.