RU2717854C1 - Weighted grouting mortar - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: invention relates to cementing of casing strings in oil, gas and gas condensate wells, which open reservoirs with abnormally high pressures and high temperatures. Weighted backfill solution contains 37.43–39.02 wt% of Portland cement of plugging, 24.17–27.29 wt% of galenite concentrate from lead ores, 0.02–0.05 wt% nitrilotrimethylphosphonic acid, 0.08–0.23 wt% of Natrosol 250 EXR, 10.74–14.04 wt% of ground dust quartz of grade B, 2.30–4.68 wt% of condensed microsilica MK-85, and water – balance.

EFFECT: high strength of the stone in the initial period of hardening of the weighted grouting mortar and formation of a stone which is resistant to the corrosive effect of high temperatures.

1 cl, 1 tbl, 1 ex

Description

The invention relates to the field of cementing casing strings in oil, gas and gas condensate wells, revealing formations with abnormally high pressures and elevated temperatures.

Known weighted grouting solution, including Portland cement grouting, weighting additive iron ore concentrate, ferrochrome lignosulfonate and water [RU 2109924 C1, EV 33/138, publ. 04/27/1998].

The disadvantages of the well-known cement slurry are premature thickening, which leads to a decrease in pumpability, sedimentation instability and low density, which makes it impossible to use it at intervals with abnormally high reservoir pressures and elevated temperatures.

The closest in composition and purpose is a heavy cement slurry, including Portland cement, cement, galena concentrate from lead ores, nitrilotrimethylphosphonic acid and Natrosol 250 EXR and water [RU 2591058 C1, C09K 8/48 E21B 33/138, publ. 07/10/2016].

The disadvantages of the known composition are the low strength of the stone in the initial period of hardening of the solution and the low heat resistance of the formed stone at elevated temperatures. The totality of these disadvantages does not allow for reliable and long-term separation of productive formations with abnormally high pressures and elevated temperatures.

During the development of the invention, the solution to the technical problem - improving the quality of cementing of casing strings in wells that open reservoirs with abnormally high pressures and elevated temperatures is provided by creating a weighted grouting solution, while achieving a technical result consisting in increasing the strength of the stone in the initial period of hardening of a heavily grouted solution and the formation of a stone resistant to the corrosive effect of elevated temperatures.

The essence of the invention as a technical solution is expressed in the following set of essential features, sufficient to solve the specified technical problem and obtain the technical result provided by using the invention. Weighted grouting mortar contains Portland cement grouting, weighting additive concentrate galena from lead ores, retarder nitrilotrimethylphosphonic acid, water loss reducer Natrosol 250 EXR, powdered silica grade B, condensed silica fume MK-85 and water in the following ratio. %: Portland cement grouting - 37.43-39.02, galena concentrate from lead ores - 24.17-27.29, nitrilotrimethylphosphonic acid - 0.02-0.05, Natrosol 250 EXR - 0.08-0.23, powdered silica grade B grade - 10.74-14.04, condensed silica fume MK-85 - 2.30-4.68, water - the rest.

Condensed silica fume MK-85 is a highly dispersed material containing silica in an amorphous form and is an active mineral component in solution. Reacting with calcium hydroxide already at the initial stage of hydration of cement Portland cement, MK-85 provides the formation of calcium hydrosilicates and the rapid formation of a crystallization structure in the initial period of hardening.

Powdered quartz powdered grade B contains silica in crystalline form and, due to slower dissolution at elevated temperatures, reacts with calcium hydroxide to form low-basic calcium hydrosilicates at a later stage of hardening. It is the main component providing a high final strength of the stone and its long-term heat resistance.

Due to the mutual influence of MK-85 and quartz B, there is a rapid increase in the strength of the stone in the initial period of hardening, followed by a less intensive, but more continuous increase in strength over time. The indicated staged nature of the interaction of silica-containing components with the products of hydration of cement Portland cement allows the formation of a more ordered crystallization structure of stone, characterized by high early strength and the ability to withstand the corrosive effect of elevated temperatures.

Nitrilotrimethylphosphonic acid is a moderator reagent and allows you to provide the necessary induction period before the start of hydration of cement Portland cement and the regulation of the interaction of MK-85 with calcium hydroxide.

Natrosol 250 EXR, in addition to the main function of the fluid loss reducer, enhances the clogging effect of MK-85 and promotes the formation of a low-permeable stone structure by additional clogging of the pores between the finely dispersed particles of MK-85 and the coarser particles of galena and quartz B. concentrate.

The following components were used to prepare the proposed weighted grouting mortar:

- Portland cement grouting type ПЦТ I-G-CC-1 in accordance with GOST 1581-96;

- galena concentrate from lead ores (KG-2) according to TU 1725-011-56864391-2008 (weighting compound);

- powdered silica grade B grade according to GOST 9077-82;

- condensed silica fume MK-85 according to TU 5734-048-02495332-96;

- nitrilotrimethylphosphonic acid according to TU 2439-347-05763441-2001;

- Natrosol 250 EXR according to TU 2231-001-21095737-2005;

- tap water in accordance with GOST R 51232-98.

The main technological properties of mortar and stone were determined in accordance with GOST 26798.1-96 “Cement grouting. Test methods ”and GOST 26798.2-96“ Cement grouting types I-G and I-H. Test Methods. "

To determine the intensity of increasing the strength of a stone of a heavier grouting mortar in the initial period of hardening and to evaluate the resistance of a stone to elevated temperatures, cubed samples were placed in water and stored in an autoclave at a temperature of (120 ± 2) ° С and a pressure of 85 MPa for 12 h. 24 hours and 168 hours. After the indicated time intervals, the compressive strength of the stone was determined for the cubic samples and the obtained values were compared to assess the intensity of the increase in the strength of the stone over time (data after 12 hours and 24 hours rhenium) and its heat resistance (data comparison after 24 hours and 168 hours of hardening).

Weighted grouting solution was prepared as follows.

Initially, Portland cement grouting, galena concentrate from lead ores, grade B powdered silica, condensed silica fume MK-85, Natrosol 250 EXR are mixed in predetermined proportions, the resulting material is thoroughly mixed for homogenization. Separately, the calculated amount of NTFC is dissolved in tap water. Then the material is mixed with a solution of NTFC in a laboratory mixer SL-1 according to GOST 26798.1-96 and the technological properties of the resulting solution and the formed stone are determined.

Example. For the preparation of the proposed weighted cement slurry with a density of 2.30 g / cm ³ (table, composition 7), 37.92 wt. % Portland cement grouting PCT IG-CC-1, 25.54 wt. % galena concentrate from lead ores, 11.61 wt. % quartz powder dust grade B, 2.32 wt. % condensed silica fume MK-85, 0.15 wt. % Natrosol 250 EXR mix until homogeneous. Then, a weighted grouting solution is prepared from the resulting mixture by mixing with tap water (22.44 wt.%) With the addition of NTFC (0.02 wt.%). After mixing for three minutes, determine the density (g / cm ³ ), spreadability (mm), water separation (ml) and the thickening time of the resulting weighted grouting mortar.

The remainder of the solution is poured into cubes, which are placed in the chamber of a high pressure autoclave and stored at a temperature of (120 ± 2) ° С and a pressure of 85 MPa for 12 hours, 24 hours and 168 hours. After the indicated time intervals for samples, cubes determine the compressive strength of the stone.

The prepared solution has a density of 2.30 g / cm ³ , a spreadability of 206 mm, zero water separation and a thickening time of 5 hours and 15 minutes. The compressive strength of the stone after 12 hours, 24 hours and 168 hours of hardening of the solution is 16.9 MPa, 21.5 MPa and 40.2 MPa, respectively. Thus, the proposed weighted grouting mortar, in contrast to the prototype, is characterized by a more intensive set of strength of the stone in the initial period of hardening (after 12 hours) and a further increase in strength over time, indicating the absence of thermal corrosion.

Examples of preparation and testing of the remaining compositions shown in the table are similar to the above.

To identify the distinguishing features and the claimed technical result, the mass ratios of the components were changed. As can be seen from table 2, in the specified range of the ratio of the components of the inventive weighted grouting mortar, at a density comparable with the prototype, allows you to form a stone with higher values of compressive strength after 12 hours and 24 hours of hardening. Unlike the prototype, with prolonged hardening (within 168 hours) for the inventive solution there is no decrease in the tensile strength of the stone under conditions of elevated temperature and pressure, which indicates its heat resistance.

In the case of transcendental proportions of the components, the prepared solutions are characterized by a deterioration in physical and mechanical properties. In particular, when the MK-85 content is less than 2.30%, the rate of curing in the initial period is significantly reduced, and when the content is more than 4.68%, the heavy grouting mortar is characterized by low spreadability and a short thickening time.

Putting ground pulverized silica into the solution of less than 10.74% leads to a decrease in the heat resistance of the stone, and a dosage increase of more than 14.04% is impractical, since there is no significant increase in the final strength of the stone and its heat resistance.

In the case of transcendental concentrations of Natrosol 250 EXR, there is a violation of the stability of the weighted solution (composition 20) or a decrease in its spreadability to unacceptable values (composition 21).

In the specified concentration range of NTFC, the required thickening time of the solution and the activity of the interaction of MK-85 with calcium hydroxide hydrated grouting Portland cement are provided. In the case of a decrease in the concentration of NTFCs less than 0.02%, the interaction of MK-85 with calcium hydroxide is accelerated and the thickening time of the solution decreases, and with an increase in the concentration of NTFCs more than 0.05%, an undesirable slowdown of crystallization structure formation processes and an excessive increase in the thickening time occur.

As can be seen from the table, the inventive weighted grouting mortar, including Portland cement grouting, galena concentrate from lead ores, nitrolotrimethylphosphonic acid, Natrosol 250 EXR, powdered silica grade B, condensed silica fume MK-85 and water, with the indicated ratio of components in the specified stone ratio is characterized by high strength stone the initial period of hardening of the solution, and the formed stone is resistant to the corrosive effect of elevated temperatures.

Thus, the claimed weighted cement slurry will improve the quality of cementing of casing strings and the durability of wells in the presence of formations with abnormally high pressures and elevated temperatures.

Claims (2)

Weighted grouting mortar, characterized in that it contains Portland cement grouting, galena concentrate from lead ores, nitrilotrimethylphosphonic acid, 250 EXR natrosol, powdered silica grade B, condensed silica fume MK-85 and water, in the following ratio of components, wt. %: Portland cement grouting 37.43-39.02 Lead Ore Galenite Concentrate 24.17-27.29 Nitrilotrimethylphosphonic acid 0.02-0.05 Natrosol 250 EXR 0.08-0.23 Dust quartz powder grade B 10.74-14.04 Condensed silica fume MK-85 2,30-4,68 Water rest