Invert emulsion based completion and displacement fluid and method of use

Abstract

A method of cleaning a wellbore prior to the production of oil or gas, wherein the wellbore has been drilled with an invert emulsion drilling mud that forms an invert emulsion filter cake is disclosed. The method may include circulating a breaker fluid into the wellbore, where the breaker fluid includes a non-oleaginous internal phase and an oleaginous external phase, where the non-oleaginous phase includes a water soluble polar organic solvent, a hydrolysable ester of a carboxylic acid, and a weighting agent, and the oleaginous external phase includes an oleaginous fluid and an emulsifier, and where the hydrolysable ester is selected so that upon hydrolysis an organic acid is released and the invert emulsion of the filter cake breaks.

Description

[0001] This application claims the priority under 35 U.S.C. §119 to U.S. application Ser. No. 60 / 668,485 filed Apr. 5, 2005. That application is incorporated by reference in its entirety.BACKGROUND OF INVENTION [0002] 1. Field of the Invention [0003] Embodiments relate generally to wellbore fluids. More specifically, embodiments relate to displacement and chemical breaker fluids. [0004] 2. Background Art [0005] During the drilling of a wellbore, various fluids are typically used in the well for a variety of functions. The fluids may be circulated through a drill pipe and drill bit into the wellbore, and then may subsequently flow upward through wellbore to the surface. [0006] During this circulation, the drilling fluid may act to remove drill cuttings from the bottom of the hole to the surface, to suspend cuttings and weighting material when circulation is interrupted, to control subsurface pressures, to maintain the integrity of the wellbore until the well section is cased and ceme...

AI Technical Summary

Benefits of technology

[0082] Further, while reference has been made to particular applications for the displacement and completion fluids of the present invention, it is expressly within the scope of the present invention that these fluids may be in used in a variety of well applications. Specifically, the fluids of the present invention may be used in both producing and injection wells, and may have further application in remedial clean-up of wells.

[0084] Displacement and completion fluids according to the present invention may exhibit high-viscosity indices such that they may behave as a high viscosity pill in the well completion process. Furthermore, a delay in the dissolution of the filter cake may be achieved by controlling the effectiveness and reactivity of the chemical breakers. The chemical properties of the displacement and breaker fluids disclosed herein may allow for the degradation of the emulsion of the invert emulsion filter cake and the dissolution of acid soluble bridging materials in the filter cake. Additionally, displacement and breaker fluids disclosed herein may be effectively used with either conventional invert emulsion or reversible invert emulsion drilling fluid filter cakes.

[0085] While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

Problems solved by technology

In such highly deviated holes, torque and drag on the drill string are a significant problem because the drill pipe lies against the low side of the hole, and the risk of pipe sticking is high when water-based muds are used.

Despite the many benefits of using oil-based muds, they have disadvantages.

In general, the use of oil-based drilling fluids and muds have high initial and operational costs.

These costs can be significant depending on the depth of the hole to be drilled.

However, the higher costs can often be justified if the oil-based drilling fluid prevents the caving in or hole enlargement that can greatly increase drilling time and costs.

Although filter cake formation is essential to drilling operations, the filter cake can be a significant impediment to the production of hydrocarbon or other fluids from the well if, for example, the rock formation is plugged by the filter cake.

Because filter cake is compact, it often adheres strongly to the formation and may not be readily or completely flushed out of the formation by fluid action alone.

Generally, oxidizers and enzymes are ineffective in breaking up the carbonate portion, and acid are ineffective on the polymer portions.

One of the most problematic issues facing filter cake removal involves the placement of the clean-up solutions.

The use of traditional emulsifiers and surfactants in the invert drilling fluid systems that formed the filter cake can further complicate the clean-up process in open-hole completion operations.

The problems of efficient well clean-up, stimulation, and completion are a significant issue in all wells, and especially in open-hole horizontal well completions.