RU2215124C1 - Method of preparation of light-weight grouting mortar - Google Patents

Abstract

FIELD: well construction. SUBSTANCE: method includes mixing of oil-well Portland cement with aluminosilicate microspheres and subsequent introduction into produced dry mix of mixing fluid containing cement setting accelerator and water, and their mixing. Mixing of oil-well Portland cement and aluminosilicate microspheres is effected in weight ratio of (80:90)-(10:20). Mixing fluid additionally contains oxyethylcellulose or hydrooxyethylcellulose and lignosulfonates or reagent based on melanine with the following their relation to weight of said dry mix, wt.p.p.: cement setting accelerator 0.2-3.0; oxyethylcellulose or hydrooxyethylcellulose 0.3-0.5; lignosulfonate or reagent based on melanine 0.1- 0.4; water 44-50. After introduction of mixing fluid, mixing is carried out for 0.5h. EFFECT: provided imparting to prepared mortar of high sedimentation stability, good pumpability, lower filtrate loss, controlled terms of setting and time of thickening, higher strength to cement stone with thickening, higher strength to cement stone with improved adhesion properties and low permeability. 2 tbl

Description

 The invention relates to the 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 reservoir pressures.

 There is a method of preparing a lightweight grouting mortar, according to which a mixing liquid is prepared by dissolving a distiller liquid in water - a waste product of soda ash, a mixture of cement with microspheres is prepared in a mass ratio (75-90): (10-25), which is then closed on a previously prepared mixing liquids (see RF Patent 2136845, class E 21 B 33/138, publ. 10.09.99, bull. 25). The water-solid ratio of the cement slurry obtained by this method is 0.46.

The grouting mortar obtained by the specified known method has a density of 1470-1510 kg / m ³ , the flexural strength of cement stone after 2 days of hardening is 2.2-2.8 MPa.

 However, it is characterized by insufficient spreadability (up to 174-180 mm), which complicates the subsequent technology of its injection into the well, because there is an increase in pressure during injection. In addition, the grouting composition prepared in this way is characterized by high filtration, which can lead to early setting of cement mortar and emergency situations.

Also known is a method of preparing a lightweight cement slurry for attaching casing strings under conditions of abnormally low formation pressure, according to which a suspension is prepared beforehand including an aqueous solution of sulfacell, calcium chloride and C-3 superplasticizer. Then, glass microspheres are added to this solution, and cement slurry is mixed on the resulting suspension. In this case, all the ingredients are taken in the following ratio, parts by weight: portland cement - 100; Sulfacell - 0.3-0.5; CaCl ₂ - 2.0-5.0, superplasticizer C-3 - 0.3-0.4; glass microspheres AS-9 - 5.0-7.0 and water - 54-68 (RF Patent 2172812, CL E 21 B 33/138, publ. 08/27/2001, Bull. 24).

 However, the preparation of cement slurry in a known manner under field conditions causes difficulties in mixing cement, associated with the thickening of the cement at the time of mixing the cement and a pre-prepared suspension of the specified composition and the impossibility of its subsequent pumping out due to low spreadability.

In addition, with many positive qualities of the cement slurry prepared by the known method in comparison with the above cement slurries obtained by other methods, it has several disadvantages, namely
- the use of Sulfacell brand water-soluble hydroxyethyl cellulose as a filtration reducer is not very reliable, because at present, the quality of this reagent produced in Russia cannot guarantee its stable properties, which, ultimately, affects the performance of grouting mortar;
- the use of a lightweight additive in grouting mortar - glass microspheres MS-A9 in small quantities cannot effectively reduce its density, and if their content is increased during hardening at normal temperatures, it reduces the bending strength of cement stone to 1.0 MPa;
- a decrease in the density of the cement slurry to 1500 kg / m ³ occurs mainly due to the increased water content (the water-solid ratio of the cement slurry prepared in a known manner is W / T = 0.6), which dilutes the solution and helps to reduce the strength of the resulting cement stone;
- reduced (up to 90-95 cm ³ ) filtration of this cement slurry, measured on a VM-6 device with ΔР = 0.1 MPa, at existing elevated pressures in the cementing process (due to low flowability and insufficient degree of lightness of the prepared cement slurry) will lead to filtering out free (unbound) water during the hardening process and to shrink the cement stone with the formation of channels for the flow of formation fluids, as well as lead to reduced strength of the formed cement stone.

 The closest in technical essence to the proposed solution in terms of features is a method for preparing a lightweight grouting mortar, according to which grouting Portland cement is mixed with aluminosilicate microspheres, followed by introducing a mixing liquid containing an accelerator of setting time - calcium chloride and water, and mixing ( RF patent 2151271, CL E 21 B 33/138, publ. 06/20/2000, bull. 17).

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

 The disadvantage of cement slurry prepared by the specified known method is its multicomponent nature.

 In addition, under current cementing conditions, it is impossible to provide the calculated concentration values of the reagents introduced during the implementation of the known method into the dry mixture, this, in particular, relates to the introduction of carboaluminate additives and gypsum.

 Ultimately, the uneven distribution of reagents in the bunkers of cement mixing machines can lead to a loss of mobility of the cement mortar with their increase (more than 2.67 wt.%), And if reduced below the calculated values, to decrease the expansion of cement stone.

 In addition, the cement slurry obtained in a known manner is characterized by high rates of water loss at ΔP = 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-lifting of cement to the design height and shrinkage of the resulting cement stone (formation of cracks and channels in it).

 The technical problem solved by the proposed method is to provide a grout grout prepared according to this method with increased sedimentation stability, good pumpability, low filtrate recovery, adjustable setting time and thickening time, high strength cement stone with improved adhesive properties and low permeability.

This problem is solved by the proposed method for preparing a lightweight grouting mortar by mixing grouting Portland cement with aluminosilicate microspheres, followed by introducing a mixing liquid containing a setting accelerator and water into the resulting dry mixture, and mixing, while grouting Portland cement and these microspheres is carried out in a mass ratio of 80: 90-10: 20, and the mixing liquid further comprises hydroxyethyl cellulose or hydroxyethyl cellulose and lignosulfonates or reagent based on melamine in the following ratio to the weight of the specified dry mixture, parts by weight:
Setting time accelerator - 0.2-3.0
Oxyethyl cellulose or hydroxyethyl cellulose - 0.3-0.5
Lignosulfonates or reagent based on melamine - 0.1-0.4
Water - 44-50
a after the introduction of the mixing liquid carry out stirring for 0.5 hours.

 The solution of the technical problem is provided, apparently, due to the following.

 The reduction in the specific gravity of the grout grout prepared by the proposed method, achieved by introducing a lightweight additive — aluminosilicate microspheres in the stated sequence of their introduction, does not require an increase in water-hard ratio, which positively affects the properties of the grout and the resulting cement stone.

 The presence of silicate and aluminate phases in the composition of the introduced microsphere additive promotes its participation in the formation of the structure of cement stone. The special properties of microspheres include: high fluidity, inertness with respect to many types of additives in cement slurries.

 The filtration reducing agents used in the proposed method for preparing the mixing fluid are hydroxyethyl and hydroxyethyl cellulose, and a melamine-based plasticizer-reagent or lignosulfonate in the optimal amounts indicated effectively reduce the filtrate yield and water separation of the prepared cement slurries, ensuring their stable technological performance.

 The hardening time of the obtained grouting mortar is regulated using the proposed accelerators, and its properties are maintained for the time required for its injection and placement in the well.

 Due to the fact that after mixing the cement slurry is mixed for at least 0.5 hours, a significant reduction in the initial hydration period is ensured, which leads to the possibility of eliminating shrinkage deformation during hardening of the cement slurry in the well.

 All of the above will ultimately lead to the rise of the cement slurry prepared by the proposed method to the design height, to ensure tight contact of the cement stone with the rock and the column and to increase the reliability of the separation of the layers with this solution.

 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; GSHT 1G-CC-1.

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

 - Filtration reducer - cellulose ether polymer: EXCEL grades A and B (TU 2231-016-53501222-2001).

 - Plasticizer: LST lignosulfonates (TU 13-0281036-05-89) or EXTsEM SMF (TU 2223-019-53501222-2001).

 - Setting time accelerator: calcium chloride (TU 48-10-59-79) or aluminum reagent EXTsEBM SA (TU2123-020-535011222-2001).

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

Equipment:
- cone of AzNII;
- Consistometer KTs-5;
- VIKA device;
- MII-100 tensile testing machine;
- filter press "Baroid";
- installation for determining the permeability of cement stone - UIPK-1;
- A modified device for determining soil swelling - PNG-5.

Example. 400 g of cement Portland cement grade PTs P-50 and 100 g of aluminosilicate microspheres manufactured by Uralight LLC. A mixing liquid was prepared in a separate glass by dissolving in 250 ml of water 10 g of calcium chloride, 1.5 g of EXCEL brand A hydroxyethyl cellulose and 0.5 g of lignosulfonates. Then, on the obtained mixing liquid, 500 g of the previously prepared dry mixture of cement with microspheres was mixed by gradual introduction with constant stirring on a laboratory mixer. In this case, the mixing of the closed cement slurry was carried out continuously for 0.5 hours at a speed of 100-120 rpm. The result was a cement slurry prepared by the claimed method and containing the following ingredients, wt. hours: a mixture of Portland cement and microspheres - 100; hydroxyethyl cellulose EXCEL A - 0.3; CaCl ₂ - 2.0, ACT - 0.1 and water - 50, with a cement to microsphere ratio of 80:20, respectively.

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

 In the process of laboratory research, according to GOST 26798.1-2-96, the properties of cement slurries prepared by the proposed and known prototype methods were established: density, spreadability, thickening time up to 30 UEK; filtrate recovery at ΔР = 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 cement slurry with low filtration is able to form only when prepared by the claimed method, (with the indicated sequence of operations, with stirring for at least 0.5 hours at a speed of rotation of the mixers 100-120 rpm ) and the specified ratio of ingredients.

Cement slurries obtained by the proposed method are characterized by the following stable technological parameters:
Density, kg / m ³ - 1450-1650
Spreadability, mm - 200-220
Thickening time, h-min - 3-30 - 5-20
Filtratootdacha, ^cm3 / 30 min at? P = 0.7 MPa - 12-35
Water separation, ml - 0
Setting time, h-min - beginning 6-15 - 9-00
- end 8-10 - 10-00
The bending strength during storage in fresh water, MPa for 2, 5, 8 days, respectively - 1.5-2.2; 3.4-4.2; 3.8-5.2
Ejection force, MPa - 0.83-0.9
Shrinkage of cement stone after 2 days,% - 0
The use of grouting mortar obtained by the proposed method provides, in comparison with grouting mortars 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 mortar 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 good spreadability;
- the formation of a uniform in strength non-shrink cement stone;
in addition, reduces the likelihood of behind-the-casing flows and violations of the support due to:
- high sedimentation stability of prepared cement slurries;
- improved characteristics of the cement stone formed from it as a result of high adhesive properties, strength and low permeability of this stone.

Claims (1)

A method of preparing a lightweight grouting mortar by mixing grouting Portland cement with aluminosilicate microspheres, followed by introducing a mixing liquid containing a setting accelerator and water into the resulting dry mixture, and mixing, wherein the grouting of Portland cement and said microspheres is carried out in a mass ratio of 80: 90 - 10: 20, and the mixing liquid further comprises hydroxyethyl cellulose or hydroxyethyl cellulose and lignosulfonates or chalk based reagent for the next relation to their dry weight of said mixture by weight. hours:
Setting time accelerator - 0.2 - 3.0
Oxyethyl cellulose or hydroxyethyl cellulose - 0.3 - 0.5
Melamine lignosulfonates or reagent - 0.1 - 0.4
Water - 44 - 50
and after the introduction of the mixing liquid carry out stirring for 0.5 hours

Images