RU2471845C1 - Informative grouting mortar - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: informative grouting mortar contains binding agent, liquid for pre-mixing and indicator additive; in addition, it contains regulating agent of process properties- superplasticising agent C-3, and retarding agent - nitrilotrimethylenephosphonic acid - NTP, binding agent - fine ground cement - Mikrodur or INTRATSEM, and indicator additive - water-soluble cadmium salt - cadmium chloride, sulphate, nitrate, bromide, iodide or their water-soluble mixture at the following component ratios, wt %: fine ground cement Mikrodur or INTRATSEM 100, water-soluble cadmium salt 10-120, liquid for pre-mixing 50-150, superplasticising agent C-3, 0.3-1, nitrilotrimethylenephosphonic acid - NTP 0.02-0.5.

EFFECT: enlarging the scope of application and increasing efficiency of grouting operations owing to enhancing informativity, improving manufacturing capabilities of grouting mortar, simplifying its preparation under field conditions and improved filtering capacity to low-permeable headers, microgaps and microcracks.

1 ex, 1 tbl

Description

The invention relates to the oil and gas industry, in particular to the field of cementing of casing strings, overhaul of wells, isolation of formation water, elimination of cross-flow flows, and is used as an indicator to obtain a solution with informative properties about the quality of cementing, determining filling intervals and injectivity during grouting injection and distributing it vertically behind the column.

A well-known grouting mixture containing cement, water and an indicator additive in the form of a radioactive gas isotope-radon [MS Makarov "Application of the indicator method for radon in well cementing". VNIIOENG, NTS, ser. Oil and gas geology, geophysics and drilling ”, issue 5, 1985], with the following ratio of components, weight. including: cement - 100, water - 50, an aqueous solution of radon with an activity of 1,500 microns (microroentgen) - 2.

A known method of using krypton-85 gas with a half-life of 10.3 years as an indicator in a cement slurry solution [Practical Guide to the Use of the Indicator Method for Long-Term Assessment of the Tightness of the Annulus ”, RD-05-10-03, Volgograd, 2003 g, LLC Lukoil-Nizhnevolzhskneft, LLC Lukoil-Volgograd NIPImorneft].

The location and placement of grouting mortars with indicators along the trunk and behind the column in these cases is determined by the anomalies of radioactivity with respect to the natural background of the rocks.

The disadvantages of using the above radioactive gases as indicators are:

- narrow scope due to the increased cost of technology, difficulties with the supply of isotopes and radioactive hazards to the environment and human health;

- insufficient reliability of the information obtained in time about the location and distribution of cement slurry over rock layers in the annulus due to the migration (ascent) of gaseous radioactive indicators upward;

- significant distortion of background gamma activity in the range of 100-300 m

Closest to the claimed grouting mixture is grouting mortar according to Av.St. USSR No. 1065581 in the following ratio of components, parts by weight: cement - 100, water - 45-50, indicator additive - sodium octoborate Na ₂ B ₈ O ₁₃ - 1.2-5, soda ash - 4-6, caustic soda - 1-3.

In this mixture, the use of sodium octoborate as an indicator is based on the ability of boron to absorb neutrons emitted by downhole geophysical instrument sources.

The disadvantages of this grouting mortar are:

- narrow scope, due to the difficulties of organizing the process of preparing the mixture in the field.

This is due to the fact that sodium octoborate, hydrolyzed in a mixing fluid, has a strong action that hardens cement mortar. To neutralize this effect, it is necessary to introduce an alkaline accelerator reagent — soda ash — into the mixing liquid. But the too narrow limits of the additive of this accelerator, which has a low solubility, below which it does not affect the acceleration of setting, above which the solution becomes non-pumpable, create additional difficulties when mixing the composition and reduce the reliability and safety of cementing operations. These difficulties can be eliminated by adding an additional alkaline accelerator, such as caustic soda, to the grouting mortar. In general, the addition of two alkaline accelerators causes certain practical difficulties in the process of preparation, regulation of pumpability and injection of cement mortar. Moreover, the use of caustic soda requires the use of special chemical protective equipment. In addition, sodium octoborate is a non-common reagent and practically insoluble in water;

- low efficiency of grouting due to poor filterability of the cement-based mixture, especially in low-permeability reservoirs, micro-gaps and microcracks.

This is due to the particle sizes of cement and sodium octoborate 30-50 microns, which cannot penetrate into smaller channels, cracks and microcracks;

- insufficient informational content (sensitivity), which in some cases makes it difficult to interpret well logging: neutron gamma-ray logging (NTC), pulsed neutron gamma-ray logging (INGK) and similar ones, by definition of injectivity intervals and placement of grouting mixture behind the column.

This is due to the use of sodium octoborate (Na ₂ B ₈ O ₁₃ ) as an indicator, which has an insufficient capture cross section for neutron absorption, so for boron this value is 755 barn.

The technical result of the proposed invention is to expand the scope and increase the efficiency of grouting operations by increasing the information content, improving the technological capabilities of the grouting mixture, simplifying its preparation in field conditions, increased filtering ability in low-permeability reservoirs, micro-gaps and microcracks.

This technical result is achieved by solving the problem aimed at creating an informative grouting mixture deeply penetrating into the rocks, including a binder, mixing fluid and indicator additive, additionally containing S-3 superplasticizer and NTF. A fine binder “Microdur” and “INTRACEM” are used as a structure-forming agent, water-soluble cadmium-containing salts are used as an indicator, which can be effectively used in wide ranges of temperatures, pressures, including in collectors with intergranular space less than 30 microns, as well as in the presence of cracks and microcracks with smaller sizes, in addition, for an unlimited time to carry out an indication of the distribution of cement behind the casing using neutron pulsed logging.

The technical problem is solved in that the informative grouting mixture (ITS) includes a binder, a mixing fluid, an indicator additive, while it additionally contains a rheological properties regulator - C-3 superplasticizer and setting retarder - nitrilotrimethylene phosphonic acid - NTF, as a binder - finely ground cement Microdur or INTRACEM and as an indicator additive - water-soluble cadmium salt in the following ratios of ingredients, parts by weight:

Fine cement Microdur or INTRACEM one hundred Water soluble cadmium salt 10-120 Mixing fluid 100-150 Superplasticizer S-3 0.3-1 Nitrilotrimethylene Phosphonic Acid - NTP 0.02-0.5

The essence of the invention lies in the fact that the informative cement mixture as an indicator additive contains a water-soluble cadmium salt: chloride, sulfate, nitrate, bromide, cadmium iodide or any mixture thereof, and additionally C-3 superplasticizer and nitrilotrimethylene phosphonic acid - NTF, and as fining agents use a finely dispersed binder "Microdur" or "INTRACEM".

In the proposed informative grouting mixture, the introduction of a cadmium-containing substance allows for virtually unlimited time using neutron types of geophysical logging to indicate the location and distribution of cement behind the casing and in the rock.

In natural cements and rocks, the cadmium content is insignificant and amounts to thousandths of a percent, while cadmium salts in their composition contain 50-65% cadmium, which is about 15-20% of the total weight of the grouting mixture. Such a significant difference in the cadmium content in the earth's crust allows cadmium salts to be a reliable indicator of the location of the cement slurry incorporating it.

It should be noted that, in contrast to the prototype, the proposed informative grouting mixture contains 10-50 times or more neutron-interacting substances, since the neutron capture cross section for cadmium (Cd) is 3.3 times larger than for boron (B ) and is 2500 bar. Also, unlike the prototype, the good (75-162 g / 100 g) solubility of cadmium bromide and cadmium sulfate (CdBr ₂ ; CdSO ₄ ) and very good solubility (287-327 or more g / 100 g) of cadmium chloride and CdCl ₂ ; Cd (NO ₃ ) ₂ ) in water allows you to select and adjust the required information content of the indicator mixture necessary for different downhole conditions without affecting its filtration ability to penetrate deeply into micro-gaps, microcracks and rocks.

The absence of intrinsic gamma radiation, as in the known radioactive indicator isotopes, does not require special precautions when using cadmium salts.

Of the known finely ground binders, the most effective are Microdur or INTRACEM, obtained on the basis of Portland cement.

In the proposed informative grouting mixture, highly finely ground cements, for example, Mikrodur or INTRACEM, are used as a highly demanding finely dispersed binder. The binder “Mikrodur” is produced by air separation of dust generated by grinding cement clinker, the technology of its manufacture was developed and mastered by the specialists of the company “INTRA - BAVGmbH” together with the specialists of the concern “Dyckerhoff” and is protected by the European patent. The diameter of the Mikrodur grains is 6-10 times or more smaller than the particles of the cement clinker itself. Due to the small particle size (grain diameter ≤2-6 μm), high specific surface (20000-25000 cm ² / g) and smoothly selected particle size distribution, Mikrodur solutions have a fluidity comparable to that of water, even with a minimum amount of mixing liquid, which allows the suspension "Mikrodur" to penetrate deep into low permeable rock. The expiration time (conditional viscosity) of a suspension under the age of 3 hours ranges from 28 to 30 seconds.

The manufacturing technology of specially ground cement "INTRACEM", which is close in its technological parameters to "Mikrodur", was developed by the Russian Chemical and Technical University named after D.I. Mendeleev. Due to its small particle size (less than 4.5 microns), high specific surface area (> 10000 cm ² / g) and normalized particle size distribution and the introduction of special additives, “INTRACEM” forms stable aqueous dispersions with high penetrating power, which allows the “INTRACEM” solutions to penetrate into pores and cracks less than 0.1 mm in size, reducing the open porosity of materials by 2-15 times and increasing their mechanical strength.

In contrast to the prototype, the use of a finely dispersed binder Mikrodur or INTRACEM allows to more fully bind water and tighten the structure of the stone and thereby ensure its increased fluid resistance and durability. This is also due to the fact that finely dispersed binders are able to bind water many times more, since their water-solid ratio can reach 3.0–5.0 with a specific surface of 20,000–25,000 cm ² / g versus 0.3–0.5 conventional grouting cements having a specific surface area of 3000-3500 cm ² / g.

As the mixing fluid of the proposed informative grouting mixture, usually use water in an amount of 100-150 parts by weight When the content of the mixing liquid is less than 50 parts by weight cement slurry becomes non-pumpable, with more than 150 parts by weight the solution has some sedimentation sediment.

An informative grouting mixture as an informative material contains an indicator additive - water-soluble cadmium salt in an amount of 10-120 parts by weight The addition of cadmium salt to a mixture of less than 10 parts by weight weakly reacts to the time of neutron slowdown, and the increase in the additive is more than 120 does not give a significant increase in the indications of neutron deceleration.

An informative grouting mixture as a moderator contains nitrilotrimethylene phosphonic acid - NTF in an amount of 0.02-0.5 parts by weight The addition of NTF to a mixture of more than 0.5 parts by weight increases the pumpability time of grouting mortar to 1 day, and the decrease in additive is less than 0.02 parts by weight reduces pumping time to values insufficient for carrying out technological operations with grouting mortar.

An informative grouting mixture as a regulator of rheological properties contains superplasticizer C-3 in an amount of 0.3-1 parts by weight The addition of superplasticizer S-3 to a mixture of less than 0.3 parts by weight does not allow to reduce the viscosity of the cement slurry, and the increase in additives is more than 1 wt.h. leads to a dilution of the grouting mortar and some delamination.

The preparation of an informative grouting mixture ITS can be carried out centrally in the workshop of dry grouting compositions using well-known mixing chambers. The prepared homogeneous mixture is fed into cement trucks or into bunkers of cement-mixing machines or packaged in sealed packages weighing 25-40 kg. Then the mixture is delivered to the well by one or another mode of transport.

According to the second option, an informative grouting mixture is prepared in the well in the usual way using a clay mixer or ASM-25, USO-16 aggregate-mixing machines, into which components are sequentially introduced: water, a cadmium-containing substance, a moderator reagent, a plasticizer reagent and a binder.

Determination of the basic properties of the mortar and stone is carried out in accordance with GOST 1581-96 "Cement grouting" and GOST 26798.1-96 "Test methods". Determination of density, spreadability, water separation is carried out at 22 ° C and atmospheric pressure. For conditions of moderate temperatures, tests are carried out at 75-90 ° C and atmospheric pressure. For AHP conditions - at temperatures up to 120 ° C and a pressure of 60 MPa. Spreadability is determined by the cone of AZNII, density - by a pycnometer, water separation - in a graduated cylinder, thickening time - on ZM-1002 and KTs-3 consistometers, compressive strength - on a test stand 4207D - CHANDLER. Neutron moderation was measured using an INK instrument.

When conducting laboratory tests were used:

- Microdur or INTRACEM;

- chloride, sulfate, nitrate, bromide, cadmium iodide (anhydrous);

- NTF (nitrilotrimethylene phosphonic acid);

- superplasticizer C-3;

- water.

Example.

To prepare an informative grouting mixture (composition 4, table. 1), 0.5 g of NTF, 3 g of C-3 superplasticizer, 500 g of cadmium chloride, 1000 g of Mikrodur are added to water by volume 1000 cm ³ . We mix the composition for 3 minutes, after which we determine the spreadability, density, and pumpability. Fill the mold for testing samples for strength after 2 days of hardening.

The test results are shown in table. 1. For composition 4, the density of the solution is 1.75 g / cm ³ , the spreadability is 26 cm, the bending strength is 2.0 MPa.

To measure neutron moderation, composition 4, table. 1, was poured into a stand with an annular space of 225 × 127 mm and a length of 1,500 m. Inside the stand in a pipe with an inner diameter of 108 mm filled with water was a pulsed neutron gamma-ray logging tool.

Measurements of neutron moderation showed a decrease in pulses per minute by 6-10 times compared with a sample prepared from pure Microdur or INTRACEM.

The advantages of the proposed informative grouting mixture ITS:

- expanding the scope and increasing the efficiency of grouting operations by increasing the information content, improving the technological capabilities of grouting mixtures, simplifying its preparation in field conditions, increased filtering ability in low-permeability reservoirs, micro-gaps and microcracks;

- the possibility of indicator monitoring for unlimited time;

- reduction of harmful effects on the environment and people.

The economic effect of the use of the claimed informative grouting mixture will be determined by increasing the efficiency of grouting and the possibility of indicator monitoring for unlimited time without attracting additional funds for the installation of indicator marks.

Claims (1)

An informative grouting mixture including a binder, mixing fluid and indicator additive, characterized in that it additionally contains a technological properties regulator - C-3 superplasticizer and setting retarder - nitrilotrimethylene phosphonic acid - NTF, as a binder - finely ground cement Microdur or INTRAZEM, as an indicator additive is a water-soluble cadmium salt - chloride, sulfate, nitrate, bromide, cadmium iodide or their water-soluble mixture in the following ratios of ingredients, parts by weight:
Fine cement Microdur or INTRACEM one hundred Water soluble cadmium salt 10-120 Mixing fluid 50-150 Superplasticizer S-3 0.3-1 Nitrilotrimethylene Phosphonic Acid - NTP 0.02-0.5