RU2385894C1 - METHOD OF PREPARATION OF LIGHT GROUTING MORTAR OF DENSITY 1450-1500 kg/m3 - Google Patents

Abstract

FIELD: oil-and-gas production.

SUBSTANCE: in method including preparation of dry mixture from grouting Portland cement and microspheres and following introduction into received dry mixture of tempering fluid, in the capacity of microspheres it is used mixture of silica-alumina and glass microspheres in mass ratio 1:0.05÷0.33, correspondingly, in the capacity of tempering fluid - water or 0.4 - 10% water solution of accelerators of time-of-setting - calcium chloride or sodium chloride, or chemical agent "ЭКСЦЕМ СА" in amount providing water-to-cement ratio 0.5-0.6, herewith before introduction of microspheres it is additionally introduced fluid loss reducing agent - reagent "ГИДРОЦЕМ" of grades C and B, plasticiser - lignosulphonates or reagent "ЦЕМПЛАСТ МФ" and defoaming agent - "ПОЛИЦЕМ ДФ", at following ratio of components, wt h: oil-well portland cement 75-84, microspheres 16-25, mentioned fluid loss reducing agent 0.2-0.5, mentioned plasticiser 0.1-0.5, mentioned defoaming agent 0.1-0.2, received dry mixture is intimated.

EFFECT: reduction of process life of preparation ad cementing, providing of achievement of regulated concentrations of components in grouting mortar, improvement of rheological characteristics of cement stone, increasing of stability of density of cement mortar.

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Description

The invention relates to the field of construction of oil and gas wells, in particular to methods for producing lightweight cement slurries intended for fastening casing strings under normal and abnormally low formation pressure.

A known method of preparing a lightweight grouting mortar, including the preparation of a dry mixture of grouting Portland cement and an expanding component of a carboaluminate additive and gypsum, the introduction of aluminosilicate microspheres into this mixture, followed by mixing of the obtained dry mixture with a mixing liquid, which is used as water or a 4% solution calcium chloride (RF patent No. 2151271, class E21B 33/138, publ. 06/20/2000).

The result achieved in a known manner is that with an estimated density of the prepared lightweight cement slurry 1400 kg / m ³ and a spreadability of 240 mm, the cement stone formed has high flexural strength during 2-day storage (2.1 MPa), and the expansion of cement stone after 2 days is 0.22%, which improves the quality of fastening and prevents gas and oil manifestations due to the expansion effect and the strength of the cement stone.

The disadvantage of this cement slurry, prepared in a known manner, is the impossibility of ensuring the calculated values of the concentration of the introduced reagents in the dry mixture under existing cementing conditions. This applies primarily to the introduction of carboaluminate additives and gypsum. Based on the characteristics of the physicochemical and fractional composition of these components (in particular, hygroscopicity and different sizes), their uneven distribution in the bunkers of cement mixing machines is possible, which can lead to a loss of mobility of the cement mortar when they increase (more than 2.67 wt.%), And if reduced below the calculated values - to reduce the expansion of cement stone.

In addition, obtained in a known manner grouting mortar is characterized by high rates of water loss at a pressure drop of 0.7 MPa. As a result of this, a large amount of water is filtered out from the cement slurry located in the well, especially in the context of highly permeable rocks, which leads to under-raising of cement to the design height and to shrinkage of the cement stone (formation of cracks and channels in it).

Closest to the technical nature of the present invention is a method of preparing a lightweight grouting mortar according to patent No. 2215124, class. ЕВВ 33/138, publ. 10/27/2003

According to this method, a lightweight cement slurry is prepared by mixing cement Portland cement with aluminosilicate microspheres in a ratio of 80-90 ÷ 10-20, followed by introducing a mixing liquid into the resulting dry mixture, containing: hydroxyethyl cellulose or hydroxyethyl cellulose, lignosulfonates or melamine based scramocamine and accelerator reagent, water in the following ratio to the mass of the specified dry mixture, parts by weight:

Setting accelerator 0.2-3.0 Hydroxyethyl cellulose or hydroxyethyl cellulose 0.3-0.5 Lignosulfonates or melamine reagent 0.1-0.4 Water 44-50

After the introduction of the mixing liquid, stirring is carried out for 0.5 hours.

The technical problem, which was solved in a known manner, consisted in reducing the load on the formations, ensuring the rise of the grouting mortar to the mouth by reducing the specific gravity of the grouting mortar (to 1450-1650 kg / m ³ ), low filtrate recovery to 20-30 cm ³ in 30 min on the Baroid filter press at ΔР = 0.7 MPa and to prevent the shrinkage of cement stone when added to cement mortar as a facilitating additive of aluminosilicate microspheres. In addition, when using this method, stable technological parameters of the prepared cement slurry are ensured: high sedimentation stability, good pumpability, low filtrate recovery, adjustable setting time and thickening time and, as a result, the formation of a high-strength cement stone with improved adhesive properties and low permeability.

The disadvantages of this method is that in the preparation of the mixing fluid there are difficulties in dissolving the components, namely: for the complete dissolution of the polymer requires significant time - up to 3-4 hours (in the cold season, the dissolution time increases, in addition, the required heating of certain temperature); the melamine-based reagent crumbles during dissolution, which creates difficulties and errors in determining the concentration of this reagent during control in the cementing process.

The technical result achieved by the proposed method is to reduce the technological time of the preparation process, and hence cementing, and to ensure the achievement of strictly regulated concentrations of components in the grouting fluid injected into the well to obtain the required technological properties, while improving the rheological characteristics of the cement and reducing permeability of cement stone due to the introduction of antifoam and increasing the stability of the density of the cement when it is used at elevated pressures for depths greater than 2000 m without changing the density of the mortar during the injection and forcing and the strength of the cement stone by introducing glass microspheres into the grouting mortar.

The specified technical result is achieved by the proposed method for preparing a lightweight cement slurry with a density of 1450-1500 kg / m ³ , including the preparation of a dry mixture of cement Portland cement and microspheres and the subsequent introduction of a mixing liquid into the resulting dry mixture, characterized in that a mixture of aluminosilicate and glass is used as microspheres microspheres in a mass ratio of 1: 0.05 ÷ 0.33, respectively, as a mixing liquid - water or a 0.4-10% aqueous solution of the accelerator setting time - chlo calcium id or sodium chloride or EXCEM CA reagent, and the mixing liquid is used in an amount providing a water-cement ratio of 0.5-0.6, and before the introduction of the microspheres, a filtration reducer is additionally introduced - HYDROCEM reagent grades C and B, plasticizer - lignosulfonates or CEMPLAST reagent MF, and antifoam - POLICE DF, in the following ratio of components, parts by weight:

Grouting Portland cement 75-84 Microspheres 16-25 Specified Filter Reducer 0.2-0.5 The specified plasticizer 0.1-0.5 Specified Antifoam 0.1-0.2

the resulting dry mixture is thoroughly mixed.

The specified technical result is achieved due to the following.

Thanks to the preparation of a dry mixture of their specified components, the speed of its preparation and the uniform distribution of the components is ensured. The introduction of microspheres after all components is due to the prevention of their possible interaction with the reagents introduced into the dry mixture and to reduce the likelihood of changes in the properties of the reagents.

In addition, to expand the range of application of lightweight grouting composition, it is proposed to introduce glass microspheres in their grouting composition together with aluminosilicate in a mass ratio of 1: (0.05 ÷ 0.33). Unlike aluminosilicate microspheres, the compressive strength of which is in the range of 5-12 MPa, glass microspheres do not collapse at elevated pressures that arise during the cementing process when cement is grouted. Imported glass microspheres have increased compressive strengths (up to 50 MPa). However, the high cost of imported glass microspheres (up to 8.5 thousand $ / t), domestic (40-60 thousand rubles / t) limits their widespread use. Domestic glass microspheres of various types are available with compressive strengths of up to 10-20 MPa. The consumption of glass microspheres in comparison with aluminosilicate microspheres is much lower due to the initial density of the microspheres themselves, and as it turned out, the use of the aluminosilicate and glass microspheres in their implementation with a mass ratio of 1: (0.05 ÷ 0.33) will allow using the prepared solution at the casing string descent depth is more than 2000 m, and without changing the density of this solution during pumping and squeezing, because glass microspheres without destruction withstand elevated pressures and do not collapse, thereby ensuring a stable density of the cement mortar, and under conditions of abnormally low reservoir pressures, preventing the possibility of absorption of grouting composition.

Introduction to the composition of the antifoam POLICE DF provides the necessary density of the cement mortar during mixing and maintaining stable values during its pumping and selling.

To prepare a lightweight grouting mortar of the proposed method in laboratory conditions, the following substances and equipment were used.

Substances:

- Grouting Portland cement in accordance with GOST 1581-96 of the Sukholozhsky cement plant of the following grades: PTsT P-50; PCT 1-100; PCT 1G-CC-1;

- Aluminosilicate microspheres (KM) of Uralight LLC TU 21-22-37-94;

- Glass microspheres, JSC NPO Stekloplastik TU 6-48-91-92;

- Filtration reducer - modified hydroxyethyl cellulose HYDROCEM grades C and B (TU 2231-016-53501222-2001);

- Plasticizer: LST lignosulfonates (TU 13-0281036-05-89) or CEMPLAST MF modified melamine formaldehyde resin (TU 2223-011-40912231-2003);

- Antifoam - a modified silicone polymer POLITSEM DF (TU 2228-010-40912231-2003);

- Setting time accelerator: calcium chloride (TU 48-10-59-79) or sodium chloride (TU 2152-097-00209527-2004) or modified aluminum oxide EXCEM SA (TU 2123-020-53501222-2001);

- Industrial water with a hardness of 5 mEq / l (GOST 2874-82).

Equipment:

- cone of AzNII;

- a device for measuring the permeability of cement stone (OFITE);

- an automated device for testing compressive strength (OFITE);

- 12-speed viscometer (CHANDLER);

- constant speed mixer (OFITE);

- sealed solidification chamber (OFITE);

- table sealed high pressure and high temperature consistometer (CHANDLER);

- filter press of high pressure and high temperature (OFITE);

- dynamic filter press of high pressure and temperature (OFITE).

Example.

To prepare the dry mixture, 800 g of PTZT P-50 cement Portland cement, 2 g of grade B HYDROCEM, 2 g of CEMPLAST MF, 2 g of POLITSEM DF cement slurry were taken, then lastly 160 g of aluminosilicate microspheres manufactured by Uralight LLC were introduced into the mixture, 40 g glass microspheres of JSC NPO Stekloplastik (the ratio of aluminosilicate microspheres to glass was 1: 0.25). Got a dry mixture with the following components, parts by weight:

Grouting Portland cement 80.0

Microspheres twenty Filtration Reducer 0.2 Plasticizer 0.2 Antifoam agent 0.2

In a separate beaker, 500 ml of mixing liquid was prepared in the form of an aqueous solution of calcium chloride of 4% concentration. Then, on the obtained mixing liquid, the previously prepared dry mixture of cement with microspheres and reagents was mixed by gradual injection with constant stirring on a laboratory mixer. While mixing the shut-in cement slurry was carried out continuously for at least 0.5 hours at a speed of 100-120 rpm The result was a cement slurry prepared by the claimed method with a water / cement ratio B / C = 0.5.

In the same way, the proposed method for the preparation of cement slurries with other component compositions was carried out.

The implementation of the method of preparation of lightweight cement slurry in the field is as follows:

1. The mixers are charged with a dry mixture containing the following materials and reagents, parts by weight:

Grouting Portland cement 75-84 Microspheres 16-25 Filtration Reducer 0.2-0.5 Plasticizer 0.1-0.5 Antifoam agent 0.1-0.2

After packing, the faucets are twice re-cooked in order to obtain a homogeneous mixture.

2. A mixing fluid is prepared in the measuring units of the cementing units - process water with an accelerator of setting time. The flow rate of the accelerator is from 0 to 110 kg / m ³ depending on the choice of type of accelerator, the required density of the cement slurry and the water-cement ratio.

3. At the next stage, the cement slurry is mixed with the required density and pumped into a mixing-averaging tank, where it is mixed for at least half an hour in order to equalize and stabilize the technological properties of the cement mortar.

4. Then, the resulting cement slurry is pumped into the well and installed in an annular space.

In the process of laboratory research by the methods of GOST 26798.1,2-96, the properties of cement slurries prepared by the proposed and known by the prototype methods were established: density, spreadability, thickening time up to 30 Bc; filtrate recovery at Δ = 0.7 MPa in 30 min; setting time, water separation; bending strength at 2-day storage in fresh water; shrinkage of the resulting cement stone.

Data on the ingredient content of the investigated cement slurries prepared by the proposed and known methods are shown in table 1.

Data on the properties of these grouting mortars obtained during the studies are shown in table 2.

The data shown in table 2 show that a lightweight cementing composition with low filtration is able to form only when it is prepared by the claimed method (with the specified sequence of operations and the specified ratio of components).

Cement slurries obtained by the proposed method are characterized by the following stable technological parameters:

Lightweight grouting mortars obtained by the proposed method are characterized by the following indicators:

Density, kg / m ³ 1450-1500 Spreadability, mm 220-250 Thickening time, h-min 4-30 - 6-10 Water separation, ml 0 2-day bending strength storage in fresh water, MPa 1.1-1.6 pushing force, MPa 0.36-0.72 shrinkage of cement stone after 2 days,% 0

The use of cement slurry obtained by the proposed method provides, in comparison with cement slurries prepared by known methods:

- high quality fastening due to:

- optimal technological properties of the cement slurry prepared by the proposed method;

- ensuring the rise of the cement slurry to the design height by reducing the density;

- reducing the load on the formations, especially under conditions of abnormal formation pressures and design pressures in the cementing process due to low density and optimal rheological properties;

- the formation of a uniform in strength non-shrink cement stone.

In addition, when using cementing cement slurry prepared by the proposed method, the likelihood of behind-the-casing flows and violations of the lining is reduced due to:

- high sedimentation stability of prepared cement slurries;

- improved characteristics of the formed cement stone due to strength, adhesive properties, and low permeability

of this stone.

Claims (1)

A method of preparing a lightweight cement slurry with a density of 1450-1500 kg / m ³ , comprising preparing a dry mixture of cement Portland cement and microspheres and then introducing a mixing liquid into the resulting dry mixture, characterized in that a mixture of aluminosilicate and glass microspheres in a mass ratio of 1 is used : 0.05 ÷ 0.33, respectively, as a mixing liquid - water or a 0.4-10% aqueous solution of the setting accelerator - calcium chloride or sodium chloride, or EXTsEM CA reagent, exc m the mixing liquid is used in an amount that provides a water-cement ratio of 0.5-0.6, and before the introduction of the microspheres, a filtration reducer - HYDROCEM reagent grade C and B, plasticizer - lignosulfonates or CEMPLAST MF reagent and antifoam - POLIT TEM DF are additionally introduced in the following ratio components, parts by weight:
Grouting Portland cement 75-84 Microspheres 16-25 Specified Filter Reducer 0.2-0.5 The specified plasticizer 0.1-0.5 Specified Antifoam 0.1-0.2
the resulting dry mixture is thoroughly mixed.