RU2239049C1 - Lightened cementing solution - Google Patents

Abstract

FIELD: oil and gas extractive industry.

SUBSTANCE: solution has cementing Portland cement, expanding admixture - furnace dust from production of cement clinker, puzzolana component, metal salt and water, as puzzolana component tripoli is used, as metal salt - copper sulfate and additionally a special plasticizer, with following ratio of components in percents of mass: cementing Portland cement - 33-42, tripoli - 8.9-21.3, furnace dust from production of cement clinker - 0.8-1.6, copper sulfate - 0.11-0.39, plasticizer - 0.006-0.063, water - the rest.

EFFECT: better technological characteristics.

3 ex, 1 tbl

Description

The invention relates to the oil and gas industry, in particular to cement slurries for cementing casing strings and installing liquidation cement bridges.

A known composition of cement slurry for attaching oil and gas wells, including mixing binder with water, in which the hydrol is preliminarily dissolved in an amount of 0.1-2.0% and copper sulfate pentahydrate in an amount of 0.05-1.0% by weight of the binder [ 1].

A disadvantage of the known solution are high rheological parameters and high filtration characteristics.

Known composition of the grouting mortar containing grouting Portland cement, the additive and water, as an additive contains dust-entrainment of expanded clay production in the amount of 16.7-21.0% and NTF plasticizer in the amount of 0.02-0.022% by weight of the binder [2].

The disadvantage of this solution is that cement-expanded clay systems have high water demand and require a significant water content to obtain the necessary mobility, which leads to the formation of a less strong structure of cement stone with high porosity. Due to the significant water content, grouting mortar is subject to sedimentation precipitation and filtration disruption of the structure, which contributes to low plugging ability, and grouting cement stone is subject to contraction reduction in volume during hardening.

The closest technical solution is a lightweight cement slurry, including cement slurry, an expanding component — baked dust of cement clinker production, a pozzolanic component — fly ash, metal salt and water [3] in the following ratio, wt.%:

cement cement 15.8-27.5

sodium chloride 3.8-6.1

fly ash 13.2-19.3

cement dust from electrostatic precipitators

from exhaust gases rotating

cement plant kilns 13.2-19.3

The disadvantage of the above technical solution is that cement-ash solutions during hardening undergo contraction shrinkage and are characterized by low plugging ability. This composition also has low heat resistance up to 100 ° C.

The proposed technical solution provides the necessary rheological indicators and low filtration characteristics, allows you to get the optimal structure of cement stone of low permeability and sufficient strength, and also increases the stability of the solution at high temperatures up to 140 ° C.

This object is achieved in that a lightweight grouting mortar containing grouting Portland cement, an expanding additive - baking dust of cement clinker production, a pozzolanic component, a metal salt and water, contains tripoli as a pozzolanic component, copper sulfate and an additional NTF plasticizer as a metal salt, in the following ratio of components, wt.%:

Grouting Portland cement 33-42

Tripoli 8.9-21.3

Cement clinker production dust 0.8-1.6

Copper Sulfate 0.11-0.39

NTF 0.006-0.063

Water rest

To prepare the grouting mortar, we used grouting Portland cement, a complex additive (NTF and copper sulfate), baking dust from cement clinker production as an expanding additive, and tripoli as a pozzolanic component.

Grouting Portland cement is produced in accordance with GOST 1581-96.

Tripoli is a pozzolanic component, an active mineral additive of sedimentary origin, capable of chemically binding calcium hydroxide released during the hydration of Portland cement into sparingly soluble compounds - low-basic calcium hydrosilicates.

The expanding additive is cement clinker baking dust, it contains up to 15% of calcined CaO (firing t = 1300-1400 ° С).

CuSO ₄ copper sulfate (technical copper sulfate complies with GOST 19347-99) - is a blue color crystals that are readily soluble in water. Copper sulfate is used as a salt of a polyvalent metal.

NTF (nitrilotrimethylphosphonic acid) is a white fine crystalline powder, readily soluble in water, not combustible, not explosive, is produced according to TU 6-82-11-71-79.

The expediency and efficiency of controlling the filtration, rheological characteristics and dynamics of hardening by the formation in the pore space of lightweight cement slurries of insoluble polyvalent metal gels, obtained on the basis of the exchange reaction between cement hydration products and a polyvalent metal salt, has been established.

The polyvalent metal salt (hereinafter referred to as SPM) - copper sulfate, forming the second structure-forming phase in the form of insoluble gels - polyvalent metal hydroxides, clogs the pore space of the cement slurry and the resulting cement stone and thereby increases the water-holding capacity of the cement slurry. These gel hydroxide systems retain water around the metal hydroxide core in two of its varieties - structural (bound) and adsorbed (unbound) on the surface of the particles.

The gelation process occurs as a result of an exchange reaction between calcium hydroxide and copper sulfate with the formation of sparingly soluble colloidal dispersed metal hydroxides with a gypsum solgel, for example, by the reaction:

CuSO ₄ + Ca (OH) ₂ + 2H ₂ O → (Cu (OH) ₂ ↓ + CaSO ₄ · 2H ₂ O

A feature of these metabolic reactions is the gradual formation of new gel compounds during the hydrolysis of salts and hydration of clinker cement minerals.

It has been experimentally established that polyvalent metal salts are complex reactants for grouting solutions, which form insoluble metal hydro- and salt gels in the pores of grouting slurry with the products of hydrolysis and hydration of grouting material, bind cement particles located at significant distances from each other due to additional spatial gel structure. Gel finely dispersed neoplasms change the kinetics of structure formation and hardening of cement, being in the pore space of a grouting mortar, have a water-immobilizing and colding effect. Copper sulfate (CuSO ₄ ) forms an additional structure-forming phase in the form of a sulfate gel - gypsum salt gel (see reaction), which contributes to an increase in static shear stress and plastic strength.

NTF has active functional groups that interact with transition metal cations with the formation of complex compounds that significantly improve filtration characteristics (sedimentation and suffusion resistance), effectively control rheological parameters, thickening and setting time of cement slurry at significantly lower concentrations of SPM and phosphonic complexone ( NTF) than their separate use. The action of NTF at the first stage of hardening of the cement slurry leads to its plasticization by blocking the action of SPM and the formation of metal hydroxides. This stage is typical for the process of pumping cement slurry. Subsequently, with continued pumping (stirring) and the action of temperature, the process of formation of polyvalent metal hydroxides begins, which leads to a decrease in filtration characteristics and to hardening the structure of the cement slurry, which is most preferable for displacement in annular space under the structural (cork) displacement mode.

The effect of improving filtration properties, controlling the thickening and hardening periods is based on the joint use of a polyvalent metal salt - copper sulfate and NTF, which synergistically improve the technological properties of lightweight grouting mortar.

The preparation of cement slurry is as follows.

The technological process for producing grouting mortar is carried out on existing production equipment.

The calculated amount of water is distributed in equal volumes in two prepared containers. A predetermined amount of NTF (nitrilotrimethylphosphonic acid) is poured into the first container with water with continuous stirring, stirring is carried out at t = 20 ° C until it is completely dissolved. In the second tank, observing the same requirements, the calculated amount of copper sulfate (hereinafter referred to as CuSO ₄ ) is dissolved, the resulting solution is pumped into the first tank in a solution of water and NTF. The mixture of aqueous solutions of NTP and CuSO ₄ continue to mix for another 10-15 minutes. After that, the whole mixture is pumped to a container where the mixture of cement Portland cement with tripoli and expanding additive is found in dry form, while mixing continues at t = 20 ° C until a homogeneous mixture is obtained. The end of the process is controlled visually by the uniformity of the grout.

Testing of samples was carried out on laboratory equipment in accordance with GOST 1581-96.

Example (Composition 1)

The estimated amount of water 224 g (44.78%) is distributed in two prepared containers in equal volumes.

In the first container, 112 g (22.39%) of water is dissolved with continuous stirring 0.03 g (0.006%) of NTF, mixing is carried out until it is completely dissolved. In another container - 112 g (22.39%) of water was dissolved 0.55 g (0.11%) of CuS04. The aqueous mixture is poured into the second container or vice versa, the resulting aqueous solution is pumped into a container in which there is a dry mixture of cement Portland cement with tripoli and an expanding additive (165 + 106.5 + 4) g (33 + 21.3 + 0 , 8)% and mixing of the solution continues until a homogeneous cement slurry is obtained.

Example (Composition 2)

The estimated amount of water 235 g (47%) is distributed in two prepared containers in equal volumes.

In the first container - 117.5 g (23.5%) of water, with continuous stirring, 0.315 g (0.063%) of NTF is dissolved, mixing is performed until it is completely dissolved. In another container - 117.5 g (23.5%) of water, 1.95 g (0.39%) of CuSO _{4 was} dissolved. The aqueous mixture is poured into the second container or vice versa, the resulting aqueous solution is pumped into a container in which there is a dry mixture of cement Portland cement with tripoli and an expanding additive (210 + 44.5 + 8) g (42 + 8.9 + 1 , 6)% and mixing of the solution continues until a homogeneous cement slurry is obtained.

Example (Composition 3)

The estimated amount of water 228 g (45.6%) is distributed in two prepared containers in equal volumes.

In the first container, 114 g (22.8%) of water is dissolved with continuous stirring 0.27 g (0.054%) of NTF, mixing is carried out until it is completely dissolved. In another container - 114 g (22.8%) of water was dissolved 1.8 g (0.32%) of CuSO ₄ . The aqueous mixture is poured into the second container or vice versa, the resulting aqueous solution is pumped into a container in which there is a dry mixture of cement Portland cement with tripoli and an expanding additive (170 + 94.5 + 5.5) g (34 + 18.9 +1.1)% and mixing of the solution continues until a homogeneous cement slurry is obtained.

Table 1 shows the various compositions of the cement slurry, the test results of the solution are given in table 2.

As can be seen from the tables, the combination of a complex additive (NTF and CuSO ₄ ) with an expanding additive - caking dust of cement clinker production (compounds No. 1, 2, 3), contributes to:

- increase the stability of the solution;

- improving filtration properties, allows you to adjust the time of thickening and hardening using complex multifunctional chemical compounds obtained by the interaction of phosphonic reagents with salts of polyvalent metals;

- characterized by an increased magnitude of expansion up to 4% in the well at temperatures up to 140 ° C. Such an expansion provides pressure on the walls of the wells and casing up to 1-2 MPa, which increases the contact of cement stone with the wall of the well, a significant increase in its strength and decrease gas and water permeability;

- contributes to high sedimentation stability, the formation of low-permeable stone structure, the manifestation of the expansion effect, a high rate of plugging ability.

With an increase in tripoli content of more than 22% and a decrease in the amount of complex additives (NTF and CuSO ₄ ) (example No. 4), the spreadability decreases to 15 cm and the strength of the cement stone to 0.7 MPa. With the introduction of an expanding additive of more than 1.7% (example No. 5), a cement stone with a low strength of 0.7 MPa is formed and cracks appear.

Evaluation of the effectiveness of the developed grouting mortar produced by testing in the field. Pilot tests of the grouting material were carried out when cementing 324 mm technical casing at the Yen-Yakhinskaya super-deep well SG-7.

According to the results of pressure testing of the string, the well was recognized as tight. ACC test results showed a hard contact (cementing quality according to ACC: 64% good, 32% satisfactory).

Sources of information

1. Copyright certificate No. 580308 for M.cl. E 21 B 33/138, 1974

2. Patent of the Russian Federation No. 2103476 for M.cl. E 21 B 33/138, 1995

3. Patent of the Russian Federation No. 2026959 for M.cl. E 21 B 33/138, 1995 - prototype.

Claims (1)

A lightweight grouting mortar containing grouting Portland cement, an expanding additive - baking dust of cement clinker production, a pozzolanic component, a metal salt and water, characterized in that it contains tripoli as a pozzolanic component, copper sulfate and an additional NTF plasticizer as a metal salt in the following the ratio of components, wt.%: Grouting Portland cement 33-42 Tripoli 8.9-21.3 Cement clinker production dust 0.8-1.6 Copper Sulfate 0.11-0.39 NTF 0.006-0.063 Water Else