RU2233860C2 - Drilling mud for drilling-in productive stratum - Google Patents

Abstract

FIELD: oil-and-gas producing industry; drilling muds for drilling-in oil and gas wells.

SUBSTANCE: proposed drilling mud contains acryl polymer, colloidal structure-forming agent, colmatage agent and water; rubber crumb updated by oil or its derivatives is used as colmatage agent at the following relationship of components: rubber crumb, 27%; oil or its derivatives, 73% at the following relationship of components, mass-%: acryl polymer, 0.6; colloidal structure-forming agent, 3; rubber crumb, 1; the remainder being water.

EFFECT: enhanced efficiency.

1 tbl

Description

The invention relates to the oil and gas industry, in particular to water-based drilling fluids for drilling wells for oil and gas, and can be used when drilling and opening productive formations of pore-fracture type.

A well-known drilling fluid for opening the strata (A.S. USSR No. 13411834, MKI S 09 K 7/02, 04/29/86), which has the following composition, wt.%:

sodium carbonate 10-20

clay powder 7-15

CMC 0.7-2

aniline 0.3-0.7

sulfur 0.3-0.7

water rest

The content of carbonate in the solution leads to a decrease in the filtration characteristics of the reservoir in the zone of penetration of the filtrate. When the filtrate enters the reservoir, it adsorbs onto the walls of the pore channels with the formation of solvate layers. The presence of CO anion in the filtrate $\genfrac{}{}{0ex}{}{\text{2-}}{\text{3}}$ contributes to the thickening and hardening of these solvate films. In the bottomhole formation zone, a blockade zone with a low permeability coefficient is formed.

The disadvantage of such a solution is that the impenetrable barrier of formation formed by it can cause great difficulties in well development, since it does not dissolve during hydrochloric acid treatment and is not washed out by the oil flow when an inflow from the well is caused.

The closest to the proposed technological essence and the achieved result is drilling fluid for opening the reservoir with abnormally high pressure (RF patent No. 2153518, IPC 7 09 K 7/02, publ. 07.27.2000), which is a bentonite suspension containing acrylic polymer, weighting agent ZhRK-1 and complex reagent - pitch carbolignosulfonate. When opening the reservoir, such a solution ensures the preservation of the filtration characteristics of the drilling fluid by stabilizing the weighted drilling fluid and creating a mud barrier.

The disadvantage of this solution is the difficulty of forming a low-permeability zone of mudding at reservoir pressures close to hydrostatic, and the need to use methods of stimulation during well development.

The objective of the invention is to improve the quality of the opening of productive formations due to the regulated colmatation.

The objective is achieved in that the drilling fluid for opening productive formations containing acrylic polymer, colloidal structure-forming agent, colmatant and water contains rubber crumb modified as oil, modified with oil or its derivatives with rubber crumb content of 27%, oil or its derivatives 73%, in the following ratio of components, wt.%: acrylic polymer 0.6; colloidal structurant 3; the specified rubber crumb 1; water is the rest.

An advantage of the invention is that the particles of colmatant - rubber crumb during oil processing - swell (their volume increases by 36%) and when introduced into the solution form aggregates (clusters of particles) with a diameter of 3-4 mm, capable of changing their volume and shape under pressure . Such aggregates of rubber crumb, encountering cracks (or pore channels) of various openings (diameters), take the shape and size of the corresponding conductive channel of the reservoir and clog it. This property of rubber crumb due to its hydrophobicity. Another important advantage of the proposed solution is that when the productive formation is opened, it forms a hydrophobic zone of mudding, which will be a significant obstacle to the further penetration of the aqueous filtrate of the solution into the formation and, at the same time, is easily destroyed by the oil flow during well development. In this regard, there is no need to use hydrochloric acid treatment.

Examples of drilling fluid compositions are presented in the table.

Claims (1)

Drilling mud for opening productive formations containing acrylic polymer, colloidal structurant, colmatant and water, characterized in that it contains rubber crumb modified with oil or its derivatives as collimant when the rubber crumb content is 27%, oil or its derivatives 73%, the following ratio of components, wt.%: Acrylic polymer 0.6 Colloidal builder 3 Specified rubber crumb 1 Water Else

Images