RU2806757C1 - Composition for preventing the occurrence of highly mineralized fluids in the well - Google Patents

Abstract

FIELD: oil and gas production industry.

SUBSTANCE: invention can be used to limit the influx of brine when drilling oil and gas wells under conditions of polymineral aggression and abnormally high formation pressures. The composition for preventing the occurrence of highly mineralized fluids in a well includes, wt.%: sodium silicate with a silicate module of 2.1 and a density of 1.34 g/cm³ - 25-27; high viscosity hydroxyethylcellulose - 2; technical water - the rest.

EFFECT: increasing the penetrating ability of the composition to prevent the manifestation of highly mineralized fluids in the well, immobilizing the brine in salt deposits after drilling and opening the brine-bearing horizon before cementing the well due to the formation of insoluble salts in the rock.

1 cl, 2 tbl, 3 ex

Description

The invention relates to the oil and gas industry, in particular to working fluids designed to limit the influx of brine during the construction of oil and gas wells under conditions of polymineral aggression and abnormally high reservoir pressures (AHRP).

An organosilicon composition for isolating water inflows into a well is known (RF patent No. 2495074, published on October 10, 2013), containing liquid glass, titanium salts: triethanolamine titanate - TEAT-1 and a solvent - industrial water in the following ratio of ingredients, wt. %:

Liquid glass 30-37 TEAT-1 4-8 Process water rest

The mechanism of action of the composition is based on the phase transition of the sol to the gel, as a result of which a three-dimensional frame mesh is formed, while ensuring the formation of an insulating screen.

The disadvantage of the composition is its low viscosity and high rate of hardening reaction, which leads to the formation of a cake at the well-rock boundary and does not allow the wellbore to be secured due to the limited penetration of the composition into the formation, which limits its use in the process of well construction under high pressure pressure conditions.

A known composition for isolating formation waters (RF patent No. 2213214, published on September 27, 2003), including an alkali metal silicate, an alkaline earth metal salt, an alkali metal salt and water, additionally containing the organosilicon compound polymethylsiloxane in the following ratio of components, wt. %:

Alkali metal silicate 0.3-4.0 Alkaline earth metal salt 0.01-0.08 Alkali metal salt 0.2-0.4 Said polymethylsiloxane 0.2-0.6 Water Rest

The mechanism of formation of the composition is based on a chemical reaction between sodium silicate and the hydrolysis product of polymethylsiloxane in an alkaline environment, resulting in the formation of an insoluble composition for isolation of formation waters.

The disadvantage of this waterproofing composition is its low shear strength under conditions of high mineralization of Ca ²⁺ and Mg ²⁺ salts, which is caused by the absence of nonionic polymers in the composition as a structure-forming component and the impossibility of uniform distribution of the blocking composition into the brine-bearing layer.

A known composition for isolating water inflow in oil wells (RF patent No. 2490295, published on August 20, 2013), consisting of an organosilicon compound, a polar solvent, a catalyst, a filler in the following ratio of ingredients, wt. h:

Silicon organic compound 100-150 Polar solvent 10-20 Catalyst (aqueous solution of hydrochloric acid) 5-20 Filler (aqueous dispersion of CMC or PVA) 100-150

The principle of operation of the proposed composition is the hydrolysis reaction of derivatives of substituted orthosilicic acid esters in the presence of acid to produce silicon polymers.

The disadvantage of the insulating composition under consideration is the presence as a carrier of anionic carboxymethylcellulose, which, due to the presence of carboxylate groups in the composition under conditions of polymineral aggression, cannot act as a thickener, which reduces the shear strength of the composition.

A gel-forming composition for limiting water inflow is known (RF patent No. 2706149, published on November 14, 2019), including a dispersion of polyacrylamide and guar in water, a complex cross-linker consisting of chromium acetate and magnesium oxide in the following component ratio, wt. %:

Polyacrylamide 0.2-0.49 Guar 0.51-0.8 Chromium acetate 0.02-0.039 Magnesium oxide 0.0167-0.0199 Process water Rest

The principle of operation is that the gel-forming composition penetrates into the permeable part of the bottom-hole zone of the well over a short distance and is structured due to the intermolecular complex formation reaction, in which acrylamide and guar gum serve as the cross-linked macromolecules, and chromium acetate serves as the cross-agent.

The disadvantage of this composition is its low stability in conditions of high mineralization of brine and high pressure conditions. Polyacrylamide-based polymers do not dissolve in a mineralized environment, despite the fact that they are salt-resistant materials.

There is a known composition for isolating water inflow in a well (RF patent No. 2569125, published on November 20, 2015), adopted as a prototype, which includes sodium silicate, sodium methyl siliconate, acrylamide polymer with sodium acrylate and a gelling agent, which can be 10-20 % aqueous solution of technical calcium chloride, polyaluminum chloride or mineralized water with a density of 1150-200 kg/m ³ , as well as filler - wood flour in the following ratio of components, parts by weight:

Aqueous sodium silicate solution 100 Sodium methyl siliconate 10-50 Gelling agent 10-50 Acrylamide with sodium acrylate 0.05-0.5 Wood flour 1-5

The mechanism of action of the composition is based on a chemical reaction between sodium silicate and a 10-20% solution of technical calcium chloride, as a result of which insoluble salts of sodium metasilicate are formed.

The disadvantage of the composition is its low shear strength with high mineralization in conditions of Ca ²⁺ , Mg ²⁺ salts due to the fact that polymers like acrylamide with acrylate are dissolved in fresh water, and then inorganic salts are added to the fresh solutions. In fresh water, the polymer macromolecule is initially in an unfolded state, which consumes a lot of dissolution energy, after which the salinity of the aqueous solution reduces the rheological characteristics of the solution.

The technical result is the creation of a composition with increased penetrating ability into the brine-bearing horizon.

Composition for preventing the occurrence of highly mineralized fluids in a well, including sodium silicate with a silicate module of 2.1 and a density of 1.34 g/cm ³ and additionally high-viscosity hydroxyethylcellulose and technical water in the following ratio of components, wt. %:

specified sodium silicate 25-27; high viscosity hydroxyethylcellulose 2; industrial water rest.

The inventive crosslinker composition for eliminating the occurrence of highly mineralized fluids during well drilling includes the following reagents and commercial products containing them:

- sodium silicate from 25 to 27%, produced in accordance with GOST 13079-2021;

- high-viscosity hydroxyethylcellulose 2%, meeting the standards of GOST R 56946-2016;

- industrial water according to GOST 23732-79.

Sodium silicate is a white, finely crystalline substance without visible inclusions, which is liquid glass in powder form with the following physical and chemical parameters: silicate module from 1.8 to 3.4. Dissolves in water in proportions 1:1.

High-viscosity hydroxyethylcellulose is a cellulose ether containing nonionic hydroxyethyl groups. It is a fibrous mass, powder or granules of white, pale yellow or grayish color. Solubility in water is at least 98%. Resistant to polymineral aggressive environments. Maintains stability at temperatures up to 120°C over a wide range of environmental changes. It is used as a reagent to limit water inflows, as well as a reagent to reduce filtration and regulate the rheological properties of drilling fluids and cement mixtures.

Process water serves as the basis and dispersion medium for preparing the composition, characterized by such quality indicators as hardness and degree of mineralization.

To develop the composition, samples of brine were analyzed; the analysis showed a high content of calcium chlorides. The solidification mechanism is based on the reaction between sodium silicate and calcium salts to produce an insoluble precipitate. As a result, a blocking, impenetrable screen is formed, which makes it possible to separate the developing formation from the well and prevent the entry of highly mineralized formation water.

To slow down the reaction time and prevent the formation of insoluble calcium and magnesium silicates at the boundary of the rock and the well, and to form an insulating channel along the depth, the composition includes high-viscosity hydroxyethylcellulose at a concentration of 2%, which is combined with brine due to a more flexible macromolecule and the nonionic nature of the functional groups in hydroxyethylcellulose.

The crosslinker composition is pumped into the well and pressed until the installation interval in the well of the calculated volume of insulating solution. Process water can be used as water.

The composition is illustrated by the following examples.

Example 1. 75 g of sodium silicate is mixed with 223.5 g of technical water with a density of 1.00 g/cm ³ to obtain a solution of liquid glass, then slowly add 1.5 g of high-viscosity hydroxyethylcellulose with stirring for 45-60 minutes, then measure rheological properties for composition 1 (Table 1).

Example 2. 75 g of sodium silicate is mixed with 222 g of technical water with a density of 1.00 g/cm ³ to obtain a solution of liquid glass, then 3 g of high-viscosity hydroxyethylcellulose is added slowly with stirring for 45-60 minutes, then the rheological properties of the composition are measured 2 (Table 1).

Example 3. 75 g of sodium silicate is mixed with 219 g of technical water with a density of 1.00 g/cm ³ to obtain a solution of liquid glass, then 6 g of high-viscosity hydroxyethylcellulose is added slowly with stirring for 45-60 minutes, then the rheological properties of the composition are measured 3 (Table 1).

Next, studies were carried out on the composition of the crosslinker on filtration properties through a bulk model of a salt core saturated with brine and the effect of polymer concentration on the liquid glass solution. To give a more even distribution front of liquid glass through the bulk model, the liquid glass solution was treated with high-viscosity hydroxyethylcellulose in concentrations from 0.5 to 2%. The proposed composition uses a technical solution of sodium silicate with a silicate modulus of 2.1 as the main component for binding highly mineralized formation fluid.

In order to get as close as possible to geological conditions, the determination of the hardening ability was carried out through a bulk model of crushed salt core taken from the field using a dynamic filter press of high temperature and pressure. 250 cm ³ of different fractions of halite crumbs are poured into the cell of the filter press and compacted with a press. A perforated stainless steel disk pre-made along the inner diameter is placed on the compacted layer of salt. 250 ml of filtered brine is poured into the cell and the cell is placed in a dynamic filter press of high pressure and temperature. After filtering the brine at a pressure drop of 1 atm. a salt layer saturated with brine remains in the cell.

Stitching brine in a filter press is carried out in the following sequence. The hardener composition is poured into the prepared cell, filled with a layer of halite on top of the separating disk. The cell is placed in a chamber and under a pressure of 35 atm. pump the composition through the salt layer until liquid flows out completely from the opposite edge or until constant filtration is established for 150 minutes (Table 2).

The use of only sodium silicate with a silicate modulus of 2.1 quickly sets and hardens the salt sample, which reduces its blocking ability when interacting with mineralized waters. To give a more even distribution front of liquid glass through a bulk model, a polymer of high-viscosity hydroxyethylcellulose is additionally introduced into the liquid glass solution, while the strongest sample is formed when up to 2% of the polymer is introduced. The optimal thickener concentration in the amount of 2% high-viscosity hydroxyethylcellulose was confirmed by studying the rheological properties, filtration characteristics and assessing the curing time of the crosslinker composition for eliminating the occurrence of highly mineralized fluids during well drilling.

Claims (2)

Composition for preventing the occurrence of highly mineralized fluids in a well, including sodium silicate, characterized in that it contains sodium silicate with a silicate module of 2.1 and a density of 1.34 g/cm ³ and additionally high-viscosity hydroxyethylcellulose and technical water in the following ratio of components, wt.% : specified sodium silicate 25-27 high viscosity hydroxyethylcellulose 2 industrial water rest