RU2370515C1 - Polymer-cement backfilling solution for low temperature wells - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: invention refers to backfilling materials of temperature range of operation from 0 to 60°C and can be used in oil and gas industry. Polymer-cement backfilling solution of low-temperature wells contains, weight sh.: Portland cement PC-50-1-50 - 90-92; CFL-117 - 0.2-0.3; Concrepol - 1.0; HPC-1M - 8-10; water - 45-50.

EFFECT: creating un-shrinkable composition efficient at low temperature of operation.

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Description

The invention relates to the construction of oil and gas wells, and specifically to grouting materials with a temperature range of operation from 0 to 60 ° C, and can be used in enterprises of the oil and gas industry.

Known cement grouting composition containing the following ingredients (parts by weight): cement - 100; hydroxyethyl cellulose - 0.3-0.5; melamine-containing product - 0.5-1.0; water - 40-50. / V.G. Tataurov, O.G. Kuznetsova et al. “Grouting mortar”, RF patent No. 2149981, 1998 /.

The grouting composition has a number of advantages, which include a low filtration rate and high rheological characteristics.

The disadvantages of the well-known grouting mortar are the presence of shrinkage of the hardened stone, low adhesion to the surface of the casing string and to the walls of the wells, insufficient bending strength and insufficient pressure gradient that withstands the grouting material, preventing breakthrough of formation fluids.

The closest technical solution chosen by the authors for the prototype is a non-shrinking polymer-cement grouting composition containing Portland cement, water, an additive of two water-soluble polymers, which contribute to a decrease in fluid loss of the solution and increase adhesion of cement stone, and a mineral expanding additive operating in the temperature range from 60 to 100 ° C / V.N. Shchukin, V. A. Galustyants, V. A. Kotelnikov, S. M. Putilov, L. E. Davydkina “Polymer-cement grouting mortar for oil and gas wells”, RF patent 2319722, 2006 / .

However, this grouting mortar has several disadvantages:

1. At operating temperatures in the range of 20-55 ° C, the curing of the well-known cement composition occurs with shrinkage reaching 2.5-3.5%. This leads to the formation of fluid-conducting channels between the walls of the wells and the hardened stone, which reduces the insulating ability of the grout.

2. The known grouting composition is effective only when using Portland cement PTC-G-CC-I at operating temperatures above 60 ° C. When using Portland cement grade PTC-50-I-50, this composition within the declared concentrations of CFL-117 is 0.4-0.8 parts by weight. has a set start time of more than 8 hours, which does not meet the requirements of GOST 26798.1-96.

The aim of the present invention is to provide a non-shrinking cement composition devoid of these disadvantages and operating at low operating temperatures. This goal is achieved in that the polymer-cement grouting solution for low-temperature wells containing Portland cement PTTs-50-1-50, fluid loss reducer - CFL-117, adhesive additive - Constolol, expanding the additive and water, characterized in that it contains an expanding additive NRS-1M, in the following ratio of components, parts by weight:

Portland cement PTC-50-1-50 90-92 CFL-117 0.2-0.3 Constolpol 1,0 LDC-1M 8-10 Water 45-50

The specified ratio of the components of the cement slurry allows you to achieve the required GOST 26798.1-96 indicators such as the start and end time of setting, allows you to save declared in the known method low values of water loss and water separation, to eliminate shrinkage and to ensure the formation of expanding cement stone in the optimal range.

The choice of CFL-117 fluid loss reducer is due to both high structure-forming properties, which reduce the filtration rate at a concentration of 0.2-0.3 wt.% (Relative to cement) by more than an order of magnitude, and the fact that this polymer works in cement mixtures as in fresh water and in saline solutions. This is especially important for deposits with highly saline produced water (deposits in Tatarstan, Belarus, Kazakhstan, etc.).

The presence of another Conconstolum polymer (high molecular weight N-polyvinylamide) in the composition resistant to polymineral aggression in an amount of up to 1.0 wt.% Leads to a 3-fold increase in the adhesion of cement stone to the casing metal.

To eliminate the shrinkage resulting from cement hydration, the dispersed lime mixture НРС-1М, used for mining and drilling operations as an expanding additive of grouting materials at low temperatures, was introduced into the composition.

To obtain the inventive cement slurry in laboratory conditions, the following substances were used:

1. Grouting Portland cement PTC-50-1-50 produced by the Sukholozhsky plant, GOST 1581-96.

2. Fluid loss reducer CFL-117 - high molecular weight (5.0 · 10 ⁶ -5.8 · 10 ⁶ ) polyoxyethylene of the American company CLEARWATER Engineered Chemistry. Certificate ISO 9001, Houston, Texas 77027, 2003

3. Adhesive additive "Constolol" manufactured by LLC "Orgpolymersynthesis SPb", TU 9365-001-13803633-03. According to the Certificate of Conformity No.TEK RU, ХП 06. Р00832, Certificate No. РОСС RU.000103Ю00 is a water-polymer system of poly-N-vinylamide.

4. Mineral expansion additive NRS-1M manufactured by NPK "IZON", TU 5744-001-82475767-08, containing 65-95% calcium oxide. An analogue of the mixture of lime for mining and drilling (SIGB TU 5744-002-00782369-00).

5. Expanding additive DR-100 (based on calcium oxide) produced by NPK IZON, TU 5744-002-82475767-08. An analogue of the RD expanding additive (TU 5744-002-59758749-06).

6. Water mixing.

The essence of the invention is illustrated by the following examples.

Examples 1-3

The preparation of cement mortars was carried out according to the standard method, GOST 26798.1-96.

0.2 g of CFL-117 and 1.0 g of Conconstol are introduced into 50 ml of water. In the resulting homogeneous solution, 92 g of Portland cement PTC-50-1-50, pre-mixed with 8 g of the expanding additive NRS-1M, are closed. After thorough mixing, the composition is kept in a thermostat at 28 ° C for 30 minutes, after which its rheological characteristics are determined. The selected mode of preliminary heating of the cement slurry is close to the conditions of coagulation structure formation when it is injected into the well with an average temperature of 28 ° C to a depth of 1600 m. After 7-day hydration, the physicomechanical properties of the cured grouting material are determined.

In parallel, for comparison, a cement slurry was prepared that did not contain polymer and expanding additives (control solution) and cement mortar obtained by the prototype.

Structural and rheological characteristics of cement slurries are shown in table 1.

First of all, attention is drawn to the fact that for controlling the cement slurry (Example 1) is characterized by extremely high fluid loss (> 340 cm ^3/30 min) and increased water separation (GOST 26798.1-96 be not more than 3%). For the prototype (example 2), all rheological characteristics, with the exception of consistency, correspond to the requirements of GOST, but the main indicator of technological properties is the residence time in the liquid state (τ _{beginning capture} ) is overestimated. If the composition is taken 0.2 wt.h. CFL-117 in relation to cement, then the start time of setting of polymer-cement mortar is reduced to 6 hours. However, the shrinkage of cement stone reaches 3.5%.

This is due to the fact that the expansion additive DR-100 selected in the prototype is intended for operating temperatures above 60 ° C. At lower temperatures, the composition does not expand. As the authors of the prototype themselves indicate, the developed grouting mortar is intended for use at temperatures from 60 to 100 ° C.

The use in the composition of the lime mixture NRS-1M in an amount of 8 parts by weight in relation to cement (example 3) leads not only to the elimination of shrinkage, but also to linear expansion in the amount of 2.87%.

As you know, the linear expansion of cement-based cement compositions should not exceed 3%, otherwise, internal stresses arising under reservoir conditions can destroy the cement stone.

Examples 4-6

Table 2 shows the results of changes in the structural characteristics of the grouting composition depending on the composition.

As can be seen from table 2, the increase in the concentration of CFL-117 from 0.2 to 0.3 parts by weight (example 4) leads to some decrease in water loss. However, this increases the start and end time of setting to 6-7 hours, which is undesirable. The increase in the content in the composition of the expanding additive to 10 parts by weight (example 5) does not lead to any noticeable structural changes in the cement slurry. It can be noted that there is a slight decrease in the spreadability in the AzNII, but the mobility of the solution falls within the limits of GOST 26798.1-96.

A decrease in the water-cement ratio to 0.45 (Example 6) leads to a noticeable reduction in the thickening time of the grouting composition, a decrease in the spreadability and an increase in density, which is not always advisable.

Examples 7-9

When studying the physicomechanical characteristics of polymer cement grouting compositions, standard samples were prepared (bars 40 × 40 × 150 cm in size), and after 7-day hydration at 28 ° C, their physicomechanical tests were carried out. The results obtained were compared with the test results of standard samples synthesized by the prototype (table 3).

As can be seen from the above table 3, the cement stone obtained according to the recipe of examples 8-9, in its strength characteristics is practically not inferior to the samples obtained by the prototype (example 7). The inventive grouting composition has high compressive and bending strength, high adhesion (the adhesion of a standard oil / water composition under these conditions is 1.17 MPa). Introduction to the composition of the expanding additive NRS-1M in the amount of 8-10 parts by weight eliminates shrinkage and ensures the expansion of the cement composition of the order of 3%.

An increase in the content of LDC-1M to 12% (cement / LDC-1M ratio as 88/12, example 10) leads to a slight decrease in strength characteristics (cf. Σ _izg and Σ is _{compressed in} examples 9 and 10) and to an increase in linear expansion of more than 3% , which, as mentioned above, is undesirable. With a decrease in the concentration of LDC-1M in the grouting composition to 7 parts by weight (example 11) there is a noticeable decrease in the linear expansion of the cured composition, which is also undesirable.

Thus, the developed non-shrinking polymer-cement grouting mortar meets all the requirements of GOST 26798.1-96 for cement mortars. This solution can find application in various repair and insulation works at low temperature wells and, above all, in primary cementing of the annulus in the interval of the reservoir. Low water loss and zero water separation of the polymer-cement mortar in combination with high adhesion to the casing metal make it a promising grouting material when carrying out such works as:

- isolation of the zones of absorption of the drilling fluid and zones of water in the well;

- elimination of casing leakage;

- clogging of the overflow channels formed in separate sections between the casing and cement stone;

- isolation of aquifer absorbing formations adjacent to the object of exploitation;

- sealing threaded connections of the production string.

Claims (1)

Polymer-cement grouting mortar for low-temperature wells containing Portland cement, fluid loss reducer - CFL-117, adhesive additive - Constolol, an expanding additive and water, characterized in that the solution contains Portland cement PTC-50-1-50 as an expanding additive and as an expanding additive - LDC-1M in the following ratio of components, parts by weight:
Portland cement PTC-50-1-50 90-92 CFL-117 0.2-0.3 Constolpol 1,0 LDC-1M 8-10 Water 45-50