RU2239050C1 - Method for preparing a lightened cementing solution - Google Patents

Abstract

FIELD: oil and gas extractive industry.

SUBSTANCE: method includes mixing of cementing cement with micro-spheres and mixing with liquid, previously a dry powder-like polymer water output reducer is mixed with micro-spheres with following relation to weight of cementing cement in percents of mass: micro-spheres 10-45, water output reducer - 0.15-0.45, mixture of these admixtures is mixed with said cement and then mixed with liquid - previously prepared 0.02-0.08% solution of foam suppressant tributylphosphate with water-hard relation 0.6-0.85. As dry powder like polymer water output reducers sulphocell, camcell, oxyethylcellulose, polyvinyl spirits, polyacrylamide are used.

EFFECT: low density - up to 1200 kg/m³, low density oscillations during mixing - ±20 kg/m³, lower bed repression, prevented absorption of cementing solution, assured rise of cement to projected height.

1 ex, 2 cl

Description

The invention relates to the oil and gas industry, to methods for preparing cement slurries.

For cementing oil and gas wells with abnormally low reservoir pressures, lightweight grouting mortars are used, which are prepared by grouting cement grouting mixture with a lightweight additive (bentonite, perlite, vermiculite, gas-filled microspheres). So, for example, there is a known method for preparing two-component mixtures by mixing cement and microspheres, followed by mixing in a liquid and mixing in an averaging tank [1].

The disadvantage of this method of preparation is the need for prolonged mixing in an averaging vessel until a homogeneous solution is obtained with limited periods of thickening of the solution, as a result of which the risk of cement setting in the cementing process and the occurrence of complications increases.

Closest to the intended composition of the components is the method of preparing a lightweight cement slurry [2], which we adopted as a prototype when an aqueous solution of sulfocell, calcium chloride and C-3 superplasticizer is preliminarily prepared, into which microspheres are added, after which the cement slurry is closed cement.

The disadvantage of this method is the insufficiently low and uneven density of the prepared solution due to the fact that the microspheres float, with the dissolved sulfocell, an abundant stable foam forms, and prolonged mixing in the averaging tank can lead to thickening and setting of the solution during cementation.

The claimed invention solves the problem of obtaining cement slurry of a lower density, when the fluctuation of the density of the solution during mixing does not exceed ± 20 kg / m ³ due to the increase in the content of microspheres, the use of antifoam, and the preliminary preparation of a homogeneous cement grout mixture of dry components.

The aim of the invention is to obtain a homogeneous lightweight cement slurry of lower density.

This goal is achieved by pre-mixing with the microspheres a dry powdery polymer fluid loss reducer in relation to the weight of cement, wt.%: Microspheres 10-45, water loss reducer 0.15-0.45, the mixture of these additives is mixed with cement, then mixed onto pre-prepared 0.02-0.08% solution of antifoam tributyl phosphate with a water-solid ratio of 0.6-0.85.

Sulfocell, camcell, hydroxyethyl cellulose, polyvinyl alcohol, polyacrylamide are used as a dry powdery polymer fluid loss reducer.

From the patent and scientific and technical literature, we do not know how to prepare lightweight cement slurries, including the combination of the above actions and the quantitative ratio of the components, which allows us to conclude that the claimed technical solution is new.

The achievement of the objective of the invention is provided by:

- the possibility of introducing into the grouting mixture a large number of microspheres and, accordingly, to a greater extent, lowering the density of the grouting mortar;

- prevention of pricing, since sulfocell and other polymeric fluid loss reducers do not have time to bloom and do not serve as an air-entraining additive, and antifoam extinguishes unstable foam, which is formed due to air adsorbed on microspheres;

- preliminary preparation of a mixture of microspheres and sulfocell (other fluid loss reducers), its subsequent mixing with cement allow you to evenly distribute a relatively small amount of sulfocell (camcell, hydroxyethyl cellulose, polyvinyl alcohol, polyacrylamide) in a large number of microspheres and cement.

The main advantage of this method is that it reduces the preparation time of a lightweight cement slurry and reduces the likelihood of thickening of the cement slurry during its preparation and during cementing of the column.

From the existing level of technology, we do not know a method for preparing a lightweight grouting mortar, when it is prepared in 3 stages: on the first, a mixture of dry additives (microspheres, fluid loss reducer), on the second, mixing a mixture of dry additives and grouting cement, on the third, mixing grouting on antifoam solution, which allows us to conclude that the proposed technical solution meets the criterion of inventive step.

The method is as follows.

For cementing a specific well, the necessary density and properties are determined, the amount of lightweight cement slurry, and the mass content of the components.

In the preparation of the grouting mixture, two multi-tonnage mixing containers are used, to which the pneumatic conveying lines between the containers, the supply of components and the selection of mixtures are connected.

Such tanks are usually available on the basis of workshops for fixing wells.

The required amount of dry powdered polymer fluid loss reducer (sulfocell, or camcell, or hydroxyethyl cellulose, polyvinyl alcohol, polyacrylamide) is mixed with microspheres in an air stream in a first container. After mixing, grouting cement is supplied to the same container in a predetermined ratio, where the entire mixture of dry additives is mixed with cement in an air stream. The resulting dry cement slurry mixture containing cement, a dry powdery polymer fluid loss reducer and microspheres is pumped and mixed in a second container. At least 3 samples of the mixture are taken from this container, the samples are closed at a given water-solid ratio, the density and spreadability of the solution from each sample are determined. In the event that the density of all samples with a spreadability of 20-23 cm differs from the set value by no more than ± 20 kg / m ³ , the dry mixture is considered homogeneous and ready for use. In case of heterogeneity, the mixture is additionally mixed, pumping from one tank to another and vice versa. By mixing samples, the uniformity of the mixture is determined by density. The finished grouting mixture is transported to the place of use by cement trucks or cement mixing machines. The grouting mixture is mixed during well cementing using a pre-prepared tributyl phosphate antifoam solution in the usual way. At the same time, the density of the cement slurry varies from the set one by no more than ± 20 kg / m ³ , i.e. the solution is obtained homogeneous.

This method of preparing lightweight cement slurry was tested during cementing of five wells of the Tevlinsko-Russkinskoye field in Western Siberia. In this way, grouting mortars with a density of 1200-1250 kg / m ³ were prepared, while mixing density fluctuations did not exceed ± 20 kg / m. All wells with abnormally low reservoir pressures were successfully cemented with the rise of cement to the design height without absorption.

An example of the preparation of lightweight cement slurry.

To cement a well with an abnormally low reservoir pressure of the Tevlinsko-Russkinskoye field, a lightweight cement slurry with a density of 1200 kg in an amount of 59 m ^{3 is} required. According to preliminary analysis and calculations, to prepare a solution of such a density and in such an amount 24.9 tons of cement PTsT1-50 are needed, which facilitates the addition of aluminosilicate microspheres MS-400-11.2 tons (45% by weight of cement), sulfocell 112 kg (0.45% by weight of cement). The mixing of the dry cement mixture is carried out on a liquid - a 0.08% solution of antifoam tributyl phosphate with a water-solid ratio of 0.85.

Cement slurry is prepared as follows. Sulfocell was loaded into a mixing tank with a given number of microspheres, everything was mixed in the air stream, cement slurry was also loaded here, the whole mixture was mixed. We pumped it into another container, re-mixed and returned to the first container, again mixed. 3 samples of the mixture were taken, closed at W / T = 0.85. With a spreadability of 21-23 cm, the density of the solutions was 1220, 1200, and 1180 kg / m ³ and differed from the required one by no more than ± 20 kg / m ³ , i.e. was fairly uniform. According to laboratory studies, when grouting the grout on a defoamer solution, grouting grout - stone had the following properties:

Density 1200 kg / m ³

Spreadability 22 cm

Thickening time 120 min

Stone strength

for bending-compression after 2 days, 0.8 and 2.6 MPa

and met the requirements.

The finished grouting mixture at the drilling site was shut in a 0.08% tributyl phosphate (TBP) solution, supplied to the cement tank and pumped into the well by cementing units.

The measurements showed that the density of the lightweight cement slurry during mixing and pumping was 1200 ± 20 kg / m ³ , therefore the solution was quite homogeneous, the cementing of the well went without complications, the cement was raised to the calculated height, the cement contact with the column and rock is tight.

The preparation of lightweight cement slurries with a density of more than 1200 kg / m ³ with a lower content of microspheres, water loss reducer and antifoam within the indicated concentrations does not fundamentally differ from the method described above.

Instead of sulfocell, other fluid loss reducers — camcell, hydroxyethyl cellulose, polyvinyl alcohol, and polyacrylamide — can be used at the same concentrations.

If necessary, grouting agents (retarders, accelerators) and plasticizers can be introduced into the grouting mortar with mixing water.

A comparative analysis shows that the proposed method in comparison with the known allows you to get a homogeneous lightweight cement slurry with a density of up to 1200 kg / m ³ , whereas by the known method it is not possible to obtain a solution with a density of below 1500 kg / m ³ .

The proposed method for the preparation of grouting mortar allows to obtain a high-quality solution of low density, due to this, raise the cement behind the casing to the design height without absorption, to form a groutstone in the annulus of uniform density and strength in height.

Sources of information

1. Rogov A.A., Shipitsa V.F., Logvinenko S.V. A new technology for the preparation of two-component cement slurries // Gas industry, 1977, No. 1, p.23.

2. Patent No. 2172812, publ. 06/10/2000, the Method of preparation of lightweight cement slurry. Tsytsymushkin P.F., Goronovich and others.

Claims (2)

1. A method of preparing a lightweight grouting mortar by mixing grouting cement with microspheres and mixing with liquids, characterized in that the dry powder polymer fluid loss reducer is pre-mixed with microspheres in relation to the weight of cement cement, wt.%: Microspheres 10-45, fluid loss reducer 0, 15-0.45, a mixture of these additives is mixed with the specified cement, then shut on a liquid - a previously prepared 0.02-0.08% solution of antifoam tributyl phosphate with a water-solid ratio of 0.6-0.8 5. 2. The method according to claim 1, characterized in that sulfocell, camcell, hydroxyethyl cellulose, polyvinyl alcohol, polyacrylamide are used as dry powdery polymer fluid loss reducers.