Heavy Fluid and Method of Making It

Abstract

Heavy fluids are made from calcium bromide and at least one hydrogen bond donor such as a low molecular weight polyol or an organic acid. The combination of a hydrogen bond donor and calcium bromide as a hydrogen bond acceptor in an appropriate molar ratio forms a higher density clear completion fluid at a low temperature not otherwise obtainable with heavy aqueous solutions of calcium bromide such as are used in oilfield wells. A method of making the fluid comprises mixing calcium bromide with the polyol(s) in the presence of water and then reducing the water content, thus forming a heavy fluid. A crystallization inhibitor such as nitrilitriacetamide or a particulate silicate is included in the formulation. When the heavy fluid “freezes,” its physical form is somewhat amorphous and pumpable rather than crystalline. The heavy fluid is useful as a drilling fluid as well as a completion fluid and for other purposes in oil recovery processes where extreme density is beneficial.

Description

RELATED APPLICATION[0001]This application claims the full benefit of Provisional Application 62 / 580,813 filed Nov. 2, 2017.TECHNICAL FIELD[0002]Heavy fluids are made from calcium bromide and at least one low molecular weight polyol which acts as a hydrogen bond donor. The combination of a hydrogen bond donor and calcium bromide as a hydrogen bond acceptor in an appropriate molar ratio forms a higher density clear completion fluid at a low temperature not otherwise obtainable with heavy aqueous solutions of calcium bromide such as are used in oilfield wells. A method of making the fluid comprises mixing calcium bromide with the polyol(s) in the presence of water and then reducing the water content, thus forming a heavy fluid. When the heavy fluid “freezes,” its physical form is somewhat amorphous and pumpable rather than crystalline. The heavy fluid is useful as a drilling fluid as well as a completion fluid and for other purposes in oil recovery processes.BACKGROUND OF THE INVENTION...

AI Technical Summary

Benefits of technology

This patent describes a method for making a heavy fluid by using high amounts of calcium bromide and eliminating water as a solvent. The process involves dissolving the calcium bromide in water and mixing it with ethylene glycol. A small amount of NTA is added to prevent crystal formation. The resulting fluid has a high density and a low freeze point. The technical effect is that the method allows for the production of a stable and pumpable heavy fluid without the need for water.

Problems solved by technology

Aqueous calcium bromide solutions are commonly used because of their weight, but simply increasing the concentration of CaBr2 to obtain more weight elevates the crystallization point—the temperature at which a solid is formed, rendering the material unpumpable, thus frustrating the fluid's usefulness.

Zinc bromide can be mixed with calcium bromide to yield higher density, but zinc bromide is a marine pollutant and highly corrosive.

Fluids containing zinc bromide are highly corrosive both to skin and to metal.

In offshore wells, particularly in deep water, a completion fluid is likely to be exposed to temperatures in the range of 30° to 40° F. for extended periods of time at the mud line; thus a True Crystallization Temperature (TCT) in the completion fluid higher than 30 degrees F. is not useful in that situation.