RU2295554C1 - Plugging material and a method for preparation thereof - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: invention relates to expandable plugging materials and can find use in cementation of drill string-casing annulus in oil and gas wells within temperature range 10-30°C. Plugging material, wt %: caustic magnesite powder 48.61-50.43, magnesium chloride 12.75-13.80, sodium tripolyphosphate 1.00-1.96, double superphosphate 0.25-0.50, starch-containing reagent 0.12-0.37, and water - the balance, wherein magnesium chloride utilized is bischofite and starch-containing reagent is extrusion starch-containing reagent or modified swellable starch-containing reagent. In a plugging material preparation method involving tempering of dry mix based on caustic magnesite powder with tempering liquid, said dry mix is a mix composed of caustic magnesite powder, sodium tripolyphosphate, and starch-containing reagent, while tempering liquid is magnesium chloride solution supplemented by double superphosphate. As a result, plugging material is obtained based on magnesia binder, whose solution is characterized by acceptable thickening time values and setting times, high sedimentation stability combined with processibility of preparation thereof, while cement stone is characterized by high mechanical strength and elevated values of expansion, which, in absence of water and air moisture, ensures formation of strong and fluid-impermeable contact with both casing strings within annulus.

EFFECT: enhanced plugging material preparation efficiency and improved cement stone characteristics.

4 cl, 1 tbl

Description

The invention relates to the oil and gas industry, namely to expanding cementing materials and methods for their preparation, and can be used in well construction, namely, in cementing the annulus and casing strings in the intervals of the anhydrous part of an open section in oil and gas wells in a temperature range of 10 -30 ° C.

Expanding grouting materials based on Portland cement clinker with additives, for example, gypsum-alumina cement, are commercially available according to TU 5734-004-002066492-02 "Expandable cement grouting lightweight for arctic conditions" and TU 5736-002-00282205-98 "Cement cement arbor ".

A disadvantage of the well-known grouting materials is that they form expanding cement stone only under conditions of replenishment with formation water contained in the rocks composing the well walls. In the absence of water access to the grouting mortar placed in the annular annular space, as a rule, a cement stone is formed, characterized by low strength and the absence of volume expansion, and more often - shrinkage. As a result, micro-gaps are formed between the cement stone and the casing, the presence of which eliminates the possibility of ensuring the tightness of the annular support in deep wells. Poor cementing results in numerous accidents and complications due to formation fluids (oil, gas) flowing through the annulus to the mouth of production wells, accelerated casing corrosion, and environmental problems in the area where oil production facilities are located.

Another significant problem arising due to poor-quality cementing of the annular space (the presence of gaps in it between insufficiently strong cement stone and casing pipes) is the impossibility of applying the acoustic cementometry (ACC) method under these conditions, due to which the condition in time of supporting the external casing is estimated the column. As a result, it is impossible to take timely measures to exclude the occurrence of emergency situations.

Grouting material is also known, containing the following ingredients, wt.%: Caustic magnesite 48.54-53.24; magnesium chloride 23.97-27.89; black monosulfite liquor 2.44-4.89; water - the rest (RF Patent No. 2060360, CL E 21 B 33/138, 1994).

However, the specified well-known cementing material has a short time of thickening and setting, is not expandable and therefore cannot be used to form a tight lining in the annular space.

High quality cementing of annular space, protection of casing from corrosion damage and the ability to control the condition of the lining behind the external column in time can be achieved only by the use of grouting materials, the solution of which is sedimentation stable, and cement stone is characterized by increased strength in the absence of access to water and moisture air, and at the same time possesses a volume expansion volume sufficient to create pressure of its skeleton on bounding surfaces (wall i) casing pipes.

Grouting material is also known (USSR Author's Certificate No. 1183660, class E 21 B 33/138, dated 1983), containing the following ingredients, wt.%:

Caustic Magnesite

(caustic magnesite powder) 43-45.9 Magnesium chloride 15.6-17.0 Sodium Tripolyphosphate 0.45-3.0 Water rest

This grouting material can provide a higher quality of well attachment in the annulus compared to grouting materials based on Portland cement.

The disadvantages of this well-known grouting material are short terms of thickening and setting, reduced sedimentation stability of the mortar, as well as insufficiently high values of the volumetric expansion of cement stone formed in the absence of free access to it of water and air moisture. Together, these shortcomings lead to a deterioration in the quality of cementing the annular space in oil and gas wells and impede the effective use of well-known cementing material.

The closest to the claimed invention by technical essence is a grouting material containing caustic magnesite, sodium tripolyphosphate, double superphosphate, starch reagent, sludge from magnesium production and water in the following ratio of ingredients, parts by weight: caustic magnesite - 0.5; sodium tripolyphosphate - 0.06; double superphosphate - 0.02; starch reagent - 0.007; the slurry of magnesium production is 1 and water is 0.67 (RF application No. 2003105775, publ. 12/20/2004, description 11 pp.).

However, this known material is characterized by the following disadvantages:

- the need to provide special safety measures when working with powdered slurry of magnesium production containing anhydrous magnesium chloride, which, when in contact with moistened skin and mucous membranes of the eyes and respiratory tract, causes a thermal burn;

- high hygroscopicity of powdered slurry of magnesium production, which does not allow for the preparation of dry cement material in conditions of high humidity. As a result of the contact of the prepared material with air moisture, it rapidly loses its chemical activity, clumps and sets;

- the complexity of regulating the technological properties of the solution of this material (thickening time, setting time) due to the extremely variable composition of the slurry of magnesium production, as well as the presence of anhydrous magnesium chloride in it, which causes a sharp increase in temperature (up to 100 ° C) of the cement slurry reaction mass , which, in turn, leads to a rapid increase in the rheological values of the solution to technologically unacceptable for the use of the solution for its intended purpose (preparation, filling, pumping and selling into the well). This is explained by the instant “brewing” of starch reagent and the avalanche-like formation of oxychlorides with the participation of caustic magnesite chemically highly active at this temperature. Reducing the amount of caustic magnesite in the system in order to obtain a cement slurry with the required values of rheological parameters in relation to the conditions of the salt section leads to an increase in the setting time of the cement mortar and the formation of cement stone with low strength and adhesive characteristics, as well as with high gas permeability;

- the presence in the cement stone of chemically unrelated readily soluble chlorides of potassium and sodium, as well as periclase, which sharply reduce the corrosion resistance of the cement stone in contact with formation water;

- the slurry of magnesium production is lumpy material, which makes it impossible to use it for the preparation of grouting material without preliminary grinding, which is an environmentally hazardous production process. Given the foregoing, the specified well-known cementing material is almost impossible to use in the field.

A known method of preparing cement material by mixing a dry mixture containing caustic magnesite (caustic magnesite powder) and sodium tripolyphosphate, a mixing liquid, which is an aqueous solution of magnesium chloride (USSR Author's Certificate No. 1183660, class E 21 B 33/138, from 1983 g .).

However, grouting material obtained by the specified known method, is characterized by several disadvantages:

- short terms of thickening and setting,

- reduced sedimentation stability of the solution,

- insufficiently high values of the volume expansion of cement stone, which is formed in the absence of free access to water and moisture in the air.

A single technical result achieved by the proposed inventions is to obtain a magnesia grouting material, the solution of which is characterized by acceptable values of the thickening and setting time, high sedimentation stability, and expanding cement stone formed from it in the absence of access to water and air humidity - the necessary values of volume increase, increased values of mechanical strength and the strength of its adhesion to the walls of the casing, while ensuring the manufacturability of its preparation.

The specified technical result is provided by the proposed grouting material containing caustic magnesite powder, magnesium chloride, sodium tripolyphosphate, double superphosphate, starch-containing reagent and water, while the ratio of ingredients is as follows, wt.%:

caustic magnesite powder 48.61-50.43 magnesium chloride 12.75-13.80 sodium tripolyphosphate 1.00-1.96 superphosphate double 0.25-0.50 starchy reagent 0.12-0.37 water rest

Bischofite is used as magnesium chloride.

As a starch-containing reagent, the material contains an extruded starch-containing reagent of the ECR brand or a modified swelling starch-containing reagent of the RMNK-2 brand.

To achieve a single technical result for the claimed group of inventions, a method for preparing cement slurry by mixing a dry mixture based on a magnesite caustic powder with a mixing fluid is proposed, while for preparing said grouting material, a mixture consisting of caustic magnesite powder, sodium tripolyphosphate and starch-containing powder is used reagent, and as a mixing liquid an aqueous solution of magnesium chloride is prepared followed by by adding double superphosphate to it.

The achievement of the specified technical result is ensured by the following.

When double superphosphate and starch-containing reagent are introduced into the proposed grouting material at their stated quantitative ratio, complex compounds are apparently formed that have high aggregate stability in concentrated solutions of magnesium chloride, which, interacting with the most active grains of caustic magnesia powder, form on their surface slightly soluble complexes that slow down the hydration process.

The increased value of the volume (skeletal) expansion of the cement stone of the proposed material is apparently due to the more effective expanding effect of sodium tripolyphosphate, taken in the proposed quantitative ratio, while slowing down the process of structure formation of cement stone.

A method of preparing the proposed cementing material in the field is as follows:

- preliminary, using a serial cement mixing technique, a dry mixture is prepared containing caustic magnesite powder, sodium tripolyphosphate and starch-containing reagent in the indicated amounts;

- the mixture is thoroughly mixed until a homogeneous mass;

- separately using mixing devices, a mixing liquid is prepared, for which an aqueous solution of magnesium chloride is first prepared and then double superphosphate is introduced into this solution;

- then, on the prepared liquid, the dry mixture is shut according to the usual technology and after averaging is pumped into the well.

To prepare the proposed grouting material intended for cementing the annular space, the following substances are used:

- caustic magnesite powder according to GOST 1216-87;

- technical magnesium chloride according to TU 2152-018-00203944-97 or bischofite solution according to TU 2152-006-00203944-99;

- double superphosphate in accordance with GOST 16306-80E;

- sodium tripolyphosphate according to GOST 13493-86E;

- starch-containing reagent: EKR brand according to TU 2483-002-41686452-97, or a modified swelling starch-containing reagent (RMNK-2) according to TU 9196-010-41686452-2003;

- technical water with a total hardness of up to 12 mEq. / L.

When mixing these substances in the proposed sequence, the inventive grouting material is formed, a sedimentation-stable solution of which can be delivered to the annular space behind the cemented casing within a technologically necessary time. After delivery and placement of grouting mortar in the annular annular space in the absence of free access of water, it sets and hardens with the formation of an expanding cement stone, which forms a tense, impermeable to liquid and gas contact with both columns.

The possibility of carrying out the claimed invention is confirmed by the following example.

Example. To prepare the proposed grouting material, first a dry grouting mixture is prepared, consisting of a powder of magnesite caustic grade PMK-83, sodium tripolyphosphate grade “technical” grade 1 and extrusion starch-containing reagent grade ECR. To do this, 49.51 g of caustic magnesite powder is thoroughly mixed with 1.49 g of sodium tripolyphosphate and 0.25 g of starch-containing reagent. Simultaneously with the preparation of the dry mixture, using an aqueous solution of bischofite (an aqueous solution of magnesium chloride) and adding double superphosphate thereto, a mixing liquid is prepared containing 35.12 g of water, 13.26 g of magnesium chloride and 0.37 g of double superphosphate. The resulting dry grouting mixture of caustic magnesite powder, sodium tripolyphosphate and starch-containing reagent is closed with the prepared mixing liquid, mixed for 3 minutes.

The compositions of the proposed grouting material with a different content of ingredients are prepared in a similar way.

Then determine the values of the properties of the obtained cement material and cement stone, formed within two days at 19-21 ° C in the absence of its contact with water and air moisture.

In the process of testing the obtained grouting material, the values of the indicators of the technological characteristics of its solution were determined - density, initial consistency, thickening time and setting time, sedimentation stability, as well as the properties of cement stone, characterizing its suitability for sealing annular space - ultimate strength in bending, adhesion strength with an envelope metal surface, volumetric (skeletal) expansion.

Data on the content of ingredients and properties of the known and proposed grouting materials are given in the table.

As can be seen from the table, the well-known grouting materials (analog and prototype) have short terms of thickening and setting, low values of sedimentation stability, as well as insufficiently high values of volumetric (skeletal) expansion of the resulting cement stone.

The proposed grouting material is characterized by the necessary values of the basic properties that determine the quality of cementing the annular space, namely, acceptable thickening and setting time, expansion of the cement stone during its formation, a sufficiently high mechanical strength and adhesion to the enveloping metal surface (casing wall) ( examples 4-6 of the table).

Exceeding the lower limit of the content of magnesium chloride, sodium tripolyphosphate, double superphosphate, and starch-containing reagent in the grouting material leads to a loss of its stability, to unacceptable thickening times for the mortar, and also to a decrease in the volumetric expansion of cement stone (table 3).

Exceeding the upper limit of the content of magnesium chloride, sodium tripolyphosphate, double superphosphate, and starch-containing reagent in the grouting material leads to an increase in the initial consistency of the mortar, a decrease in the strength of the formed cement stone and its adhesion to the envelope metal surface (table example 7).

The advantage of the inventive grouting material obtained by the proposed method is that it, due to the increase in volume during the hardening process, ensures the formation of intense contact with envelope surfaces in the absence of access to water and air moisture. This achieves a significant improvement in the quality of cementing the annular space in oil and gas wells and ensures its tightness, which will allow:

- minimize the likelihood of occurrence of intercolumnar manifestations of fluids (oil, gas);

- increase the reliability and durability of the well;

- reduce environmental risk due to intercolumnar manifestations;

In addition to the above, the presence of tight contact of the cement stone with the inner and outer pipes, high strength and uniformity in height of the cement stone will make it possible to assess the state in time of the lining behind the outer casing using geophysical methods, as well as significantly increase the corrosion resistance of the casing pipes in the well.

Claims (4)

1. Grouting material containing caustic magnesite powder, magnesium chloride, sodium tripolyphosphate, double superphosphate, starch-containing reagent and water, characterized in that the ratio of ingredients is the following, wt.%: Caustic Magnesite Powder 48.61-50.43 Magnesium chloride 12.75-13.80 Sodium Tripolyphosphate 1.00-1.96 Superphosphate double 0.25-0.50 Starchy reagent 0.12-0.37 Water Rest 2. The grouting material according to claim 1, characterized in that bischofite is used as magnesium chloride. 3. The grouting material according to claim 1, characterized in that, as a starch-containing reagent, it contains an extruded starch-containing reagent of the ECR brand or a modified swelling starch-containing reagent of the RMNK-2 brand. 4. A method of preparing grouting material by mixing a dry mixture based on a magnesite caustic powder with a mixing liquid, characterized in that for the preparation of grouting material according to claim 1, a mixture consisting of caustic magnesite powder, sodium tripolyphosphate and starch-containing reagent is used as a dry mixture an aqueous solution of magnesium chloride is prepared as a mixing liquid, followed by the introduction of double superphosphate into it.