RU2191251C1 - Grouting mortar (options) - Google Patents

Abstract

FIELD: oil and gas production. SUBSTANCE: grouting mortar contains, weight parts: cement 100, polysaccharide based on cellulose ether (polycyanine cellulose) 0.1-0.5, ethyl silicate 0.1-1.0, and water 35-50. In another variant of process, mortar also contains 0.2 to 3.9 wt parts of amorphous alumina. EFFECT: lowered filtration within wide temperature range (up to 100 C), increased strength of cement stone, and increased mobility of mortar without increase in water content. 2 cl, 2 tbl, 2 ex

Description

 The invention relates to the construction of oil and gas wells, in particular to cement slurries intended for fastening and isolation of wells, and can be used in enterprises of the oil and gas industry.

Known cement slurry containing in its composition the following ingredients, parts by weight: cement - 60-65,4;
carboxymethyl cellulose (CMC) - 1-5; salt melt - a waste of the karbofos production - 1-5; water - 30-32.6. (see ed. certificate of the USSR 1484917, class E 21 B 33/138, from 1987).

 A disadvantage of the well-known grouting mortar is the increased filtrate recovery.

Known cement slurry, which includes, wt.%:
cement - 62-64; carboxymethyl cellulose (CMC) - 0.19-0.37; sodium sulfate 0.38-0.77; water - the rest (see ed. certificate of the USSR 1637406, class E 21 B 33/138, from 1989).

 However, the well-known cement slurry has a high filtrate recovery. This is due to the fact that when cement is dissolved in water, coagulation of CMC unstable to calcium salts occurs. In addition, the reagents included in the known solution, strongly thicken it, which causes an increase in water content in the grouting mixture by 5 - 25%. As a result of this, the insulating ability and strength of the cement stone are also reduced.

 The addition of CMC to the well-known grouting composition significantly lengthens the setting time and makes them practically uncontrollable known accelerating agents in conditions of low positive and normal temperatures.

 Closest to the proposed solution in technical essence is a cement slurry containing cellulose-based polysaccharide - hydroxyethyl cellulose and water.

 However, the well-known cement slurry also has a high filtrate recovery.

The invention solves the problem of giving grouting mortar low values of the filtrate recovery index in a wide temperature range up to 100 ^o С, giving it structural and rheological parameters that provide its high mobility without increasing water content, while increasing the strength of the resulting grouting stone.

The specified technical problem is solved in two options, namely:
according to the first embodiment, a cement slurry containing cement, a cellulose ether polysaccharide, ethyl silicate (ETS) and water, the solution containing polyanionic cellulose as a polysaccharide based on cellulose ether in the following ratio of ingredients, parts by weight:
Cement - 100
Polyanionic cellulose - 0.1-0.5
Ethyl silicate - 0.1-1.0
Water - 35-50
and in the second embodiment, a cement slurry containing cellulose ether polysaccharide, ethyl silicate and water, the solution additionally containing amorphous alumina, and polyanionic cellulose as a polysaccharide based on cellulose ether in the following ratio of ingredients, parts by weight:
Cement - 100
Polyanionic cellulose - 0.1-0.5
Ethyl silicate - 0.1-1.0
Amorphous Alumina - 0.2-3.0
Water - 35-50
The achievement of the technical task is ensured, in our opinion, due to the following.

 As it turned out unexpectedly, the addition of polyanionic cellulose (PAC) does not thicken the cement slurry, reduces its filtrate recovery, and does not require, in contrast to other polymers (for example, OEC), an increased amount of additive.

 In addition, PAC in combination with ethyl silicate (ETS) also has a plasticizing effect. In combination with ETS, a synergistic effect is observed, due to which the filtrate yield of grouting mortar is further reduced. This is apparently due to the fact that, acting as a plasticizer, ETS does not allow cement particles to form large conglomerates, as a result of which the structure of the pore space changes, the pores become smaller. A decrease in pore size facilitates the stabilization of the liquid phase, and hence reduces the tendency of the solution to filtrate recovery.

 The addition of PAC with ETS to the cement mortar also makes it possible to control the water-cement ratio of the cement slurry depending on the required density. A decrease in the water-cement ratio leads to a decrease in feather space and, consequently, to an increase in strength and a decrease in the permeability of cement stone.

 Along with this, the combination of components in the proposed grouting solution allows to obtain an impermeable high-strength grouting stone.

 In order to expand the temperature range of the use of grouting mortar at low positive temperatures, amorphous alumina is additionally introduced into the grouting mortar according to the second embodiment. In addition, amorphous alumina has an anti-shrink effect on cement slab formed during hardening, and when this reagent is added to the grouting mortar in an amount of more than 0.3%, an expanding effect is observed.

It is known that polysaccharides at temperatures above 50 ^o C lose viscosity and, accordingly, the ability to effectively reduce the filtration of the cement slurry. The addition to the composition of the silicon-containing reagent - ethyl silicate (ETS) allows you to expand the scope of the polysaccharide - PAC in the temperature range up to 100 ^o C.

For the preparation of the inventive cement slurry in laboratory conditions, the following substances were used:
1. Grouting Portland cement, for example, grade ГЩТ Т-50 GOST 1581-96, ПЦТ I-100 GOST 1581-96 С, ГЩТ IG-CC-2 GOST 1581-96 Sukholozhsky cement plant ..

 2. Polyanionic cellulose - PAC: CMC content (in dry matter) - 70%, dry matter concentration of 1%, moisture content of 8%, viscosity, measured by Brookfield viscometer 25-45 MPa.

 3. Silicon-containing additive: Ethyl silicate - condensate TU 6-02-06-67-86, ethyl silicate-40 GOST 26371-84.

 4. Technical water.

 5. Amorphous aluminum oxide - gamma form MRTU 6-09-3200-66, "EXCEM SA" - TU 2123-020-53501222-2001.

The essence of the invention is illustrated by the following examples:
Example 1

To obtain the claimed solution, to 200 ml of technical water was added 1.0 g of PAC, 20 ml of ethyl silicate, and after stirring for 0.5 hours, 500 g of cement was added and a grouting solution was obtained with the following content of ingredients, parts by weight:
Cement - 100
PAC - 0.25
Ethyl silicate - 0.4
Water - 0
Example 2

 To obtain the inventive solution, 250 g of PAC and 2.5 ml of ethyl silicate were added to 250 ml of industrial water, and after stirring for 0.5 hours, 500 g of cement was added and 10 g of amorphous alumina was mixed for 0.5 h and grouting was obtained. a solution with the following ingredients, wt. hours: cement - 100; PAC - 0.4; ethyl silicate - 0.5; amorphous alumina - 2; water - 50.

 Cement slurries with a different ingredient content were prepared in a similar manner.

During laboratory tests, the following properties of the proposed and well-known grouting mortars were determined: density (kg / m ³ )
spreadability (mm); thickening time to a consistency of 30 cu (h-min);
filtrate recovery at P = 0.7 MPa (cm ³ after 30 min); water separation (cm ³ ); setting time (h-min); ultimate flexural strength when stored in fresh water after two days (MPA).

 Data on the composition of the studied grouting solutions are given in table 1.

 Data on the properties of the proposed and well-known grouting solutions are given in table.2.

Research data shows that the proposed cement slurry has the following advantages compared to the known prototype:
- low values of the filtration rate (at t = 22 ^o C Ф = 15-40 cm ³ , at t = 75 ^o С Ф = 18-65 cm ³ ) while the prototype at t = 22 ^o С Ф = 47 cm ³ and at t = 75 ^o С Ф = 95 cm ³ in 10 min;
- high spreadability (230-260 mm) compared with the prototype (210 cm) at a lower water-cement ratio;
higher strength properties of the resulting cement stone (at t = 22 ^o C strength of 4.3-5.6 MPa, at t = 75 ^o C strength of 5.8-8.1 MPa) compared with the prototype (at t = 22 ^o C strength 3.5 MPa, at t = 75 ^o C strength 5.25 MPa).

 Using the proposed solution under field conditions will ensure trouble-free delivery of cement slurry into the well, improve the quality of cementing of oil and gas wells, small diameter wells with small gaps, etc., the design of which involves small diameters and gaps.

 Due to the low water-cement ratio of the proposed cement slurry, the possibility of migration of formation fluids through the hardening cement slurry is eliminated, thereby reducing the water cut of well production.

Claims (1)

1. Grouting mortar, including cement, a polysaccharide based on cellulose ether, ethyl silicate and water, characterized in that as a polysaccharide based on cellulose ether, the solution contains polyanionic cellulose, in the following ratio of ingredients, parts by weight:
Cement - 100
Polyanionic cellulose - 0.1-0.5
Ethyl silicate - 0.1-1.0
Water - 35-50
2. A cement slurry comprising cement, a polysaccharide based on cellulose ether, ethyl silicate and water, characterized in that the solution additionally contains amorphous alumina, as a polysaccharide based on cellulose ether, the solution contains polyanionic cellulose, in the following ratio of ingredients, parts by weight :
Cement - 100
Polyanionic cellulose - 0.1-0.5
Ethyl silicate - 0.1-1.0
Amorphous Alumina - 0.2-3.0
Water - 35-50

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