RU2304606C1 - Grouting mix - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: invention relates to building wells and major repairs thereof, namely involving supporting casing strings and creating fluid-proofing isolation covers within chemical deposit interval as well as to exploitation of deposits and well abandonment. Grouting mix contains 50.00-53.95% calcium sulfate (gypsum semihydrate), 2.00-8.50% hardening additive constituted by fine mineral substance "Mikrodur-26RX", 0.05-0.08% nitrilotrimethylphosphoric acid, 41.42-44.00% sodium chloride solution having density 1.18 g/cc.

EFFECT: expanded technological possibilities of grouting mix due to proper pumpability and setting times, enhanced fluid-proofness and durability of grouting stone under complicated water-exchange conditions.

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Description

The invention relates to the oil and gas industry, in particular to the construction of wells and their overhaul, namely, when attaching casing strings and creating fluid-resistant insulating covers in the range of chemogenic deposits, as well as to the process of operating fields and eliminating wells. Will find the greatest application in the isolation of subsalt fluid-containing formations of multi-tiered deposits, liquidation of wells, as well as in the burial of toxic and radioactive waste.

Known cement mixture by Auth. St. SU No. 692982 (IPC Е21В 33/138 dated 10.25.79, Bull. No. 39) for isolating absorbing layers containing a binder, an aqueous solution of calcium chloride and a polymer additive, which contains gypsum-alumina cement as a binder and hydrolyzed as a polymer additive polyacrylogonitrile (hypane) in the following ratio of components, wt.%:

Gypsum-alumina cement 41-51 Gipan 38-23 Calcium Chloride Aqueous Solution (density 1.06-1.10 g / cm ³ ) 21-26

This grouting mixture has the following disadvantages:

- a narrow scope, associated with the low technological quality of this mixture, due to the instant coagulation of hypane in contact with an aqueous solution of calcium chloride, often leading to emergency situations due to clogging of pumping units and blockage of pressure pipes with a rubber-like coagulant;

- low efficiency of insulation work, due to the lack of fluidity, filterability (into voids, channels, cracks, pores of the formation, etc.), after mixing the components according to the technology of work and the fragility of the fluid-resistant screen created from it, since in a short time (1-5 months ) after coagulation of gypsum, the stone acquires a porous structure and becomes permeable to reservoir fluids. In addition, in contact with weakly mineralized or formation waters, where the content of polyvalent metal ions (Ca ⁺⁺ , Mg ⁺⁺ , Al ⁺⁺ , Fe ⁺⁺ , etc.) is less than 8-10 g / l, a rapid dissolution of hypane occurs, and accordingly destruction of cement stone.

The closest known analogues is the "Grouting material" by Auth. St. SU No. 1046479 (IPC Е21В 33/138 dated 10.10.83, Bull. No. 37), which is a mixture containing gypsum, hydroxy succinic malic acid and additionally containing phosphoric acid or alkali metal orthophosphates in the following ratio of components, wt.%:

Gypsum (CaSO ₄ · ₂ H ₂ O) 99.895-99.94 Hydroxy succinic malic acid 0.001-0.005 Phosphoric acid or alkali metal orthophosphates 0.05-0.1

This grouting mixture has the following disadvantages:

- a narrow scope due to the low technological use due to short pumping times of less than 0.2 hours and setting 0.5-2 hours, which makes it impossible to use it for fastening oil and gas wells, installing insulating bridges and fluid resistant screens, so how the time required to deliver the grouting mixture in place, in these cases, is longer than the pumping time, and this will lead to emergency setting of the stone already in the pressure pipes;

- low efficiency of insulating work due to the fragility of the resulting stone, due to its water resistance. As you know, gypsum hardening occurs as a result of hydration of semi-aquatic gypsum (alabaster) - CaSO ₄ · 0.5N ₂ O to _two -water gypsum - CaSO ₄ · 2Н ₂ О, the crystals of which form a gypsum stone. The solubility of gypsum gypsum is much higher than that of hydrated cement compounds - 2.5 g / l calculated on CaSO ₄ , therefore, when contacting with free (unbound) water, cement stone is destroyed faster.

The technical result of the invention is the expansion of the technological capabilities of the grouting mixture and its scope.

This technical result is achieved by solving a technical problem aimed at increasing fluid resistance and durability of cement stone in conditions of difficult water exchange.

The technical problem is solved due to the fact that in the grouting mixture containing calcium sulfate and water, the water is in a brine of sodium chloride, and additionally contains an additive - a hardener in the form of a finely divided mineral substance of the Microdur-26RX type and nitrilotrimethylphosphonic acid (NTF) in the following ratio of components:

CaSO ₄ · 0.5 N ₂ O 53.95-50.00 Microdur 2.00-8.50 NaCl brine (j = 118 g / cm ³ ) 44.00-41.42 NTF 0.05-0.08

The essence of the invention lies in the fact that the best option for attaching the casing, installing insulating bridges, fluid-resistant tires and screens in the intervals of salt deposits is the use of grouting mixtures, similar or identical in chemical composition to salts, which are mainly represented by halite (NaCl), sylvin ( KCl), bischofite (MgCl ₂ · 6Н ₂ О), carnalite (KCl · MgCl ₂ · 6Н ₂ О), anhydrite (CaSO ₄ ) and gypsum (CaSO ₄ · 2Н ₂ O). It can be seen from the chemical composition of minerals that all of them are formed by mono- or bivalent metals and acid residues of “strong” (active) acids (hydrochloric and sulfuric), which under conditions of hydrogen sulfide and salt aggression are absolutely stable when exposed to “weak” hydrogen sulfide acid.

When developing the proposed grouting mixture, the most common materials were used, such as sodium chloride and gypsum (alabaster). However, it is extremely difficult to obtain a cement stone from a saline solution of gypsum and sodium chloride at a temperature above 20 ° C due to an increase in the solubility of the latter. Introduced additive - hardener allows you to expand the temperature range of its application. This is due to the fact that during the hydration of the hardener, the concentration of salts (NaCl and CaSO ₄ ) in the solution sharply increases due to the binding of part of the water component to the dehydrated additive, and this leads to curing and crystallization of the mixture even at high temperatures up to 75 ° C and above.

As a hardener additive, a finely dispersed binder of the Microdur-261R-X type is used.

"Mikrodur" is a particularly finely dispersed mineral binder with a guaranteed smooth change in particle size distribution. Mikrodur is produced by air separation of dust by grinding cement clinker. The manufacturing technology of OTDV “Mikrodur” was developed and mastered by the specialists of the company “INTRA-BAVGmbH” together with the specialists of the concern “Dyckerhoff” (Wiesbaden, Germany) 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 and alabaster itself.

Due to the small size (grain diameter ≤6-10 μm) of the particles and the smoothly selected particle size distribution, the Mikrodur suspension has a fluidity comparable to the fluidity of the water, even with a minimum W / C. The expiration time (conditional viscosity) of a suspension under the age of 3 hours ranges from 28 to 30 seconds.

The penetrating ability of the suspension "Mikrodura" is comparable to disperse binders. Suspension "Mikrodura" penetrates into loess soils, dense concrete and rock with a distribution radius similar to disperse-free solutions.

Mikrodur is a powder with a specially selected mineral and particle size distribution. This provides a high water holding capacity (W / C up to 6.0) and rheological characteristics commensurate with the rheology of ordinary water.

Mikrodur-261R-X is resistant to chemical influences, including the effects of sulfates, hydrogen sulfide and chlorine. Thus, it can be considered as an alternative to liquid glass and polymer compositions (epoxy, carbide, phenol formaldehyde, etc.) with the following advantages: durability, simple and convenient technology for preparing a suspension and injection, environmental cleanliness, uniformity with conventional cements in composition, compatibility with cement, concrete and reinforced concrete, the ability to perform work in conditions of flooded and water-saturated structures and formations.

The inclusion of "Mikrodur" in the grouting mixture allows you to bind the "free" water in the structure of salt stone and thereby ensure its durability. In addition, filling the intergranular space of gypsum, it increases the fluid resistance of the resulting cement stone, reducing its permeability to 0.

The choice of calcium sulfate (CaSO ₄ ) as a binder is due to the fact that it has the lowest solubility of the available inexpensive and widely used salts, thereby providing a greater yield of solid material from the mixed solution during crystallization. In addition, it forms with the clinker “Mikrodura” difficultly soluble complex salt hydrates, which ensures the long life of the cement stone.

The addition of NTF (nitrilotrimethylphosphonic acid) to the grouting mixture allows us to provide the pumpability and setting time necessary for the work technology. The results of laboratory experiments are shown in table 1. The content of NTF less than 0.05% will drastically reduce the pumpability of the mixture under surface conditions, which can lead to premature formation of cement stone already in the column of pressure pipes.

The content of NTF more than 0.08% will increase the setting time in reservoir conditions to more than 18-20 hours, which is not technologically necessary.

When the content of calcium sulfate (CaSO ₄ ) is less than 50% and brine of sodium chloride (NaCl) is more than 44%, a cement stone is not formed. The introduction of more than 54% calcium sulfate into the grouting mixture with a sodium chloride brine content of less than 41% makes it not pumpable and unsuitable for technological work, especially in surface conditions.

When the hardener-Mikrodur content in the grouting mixture is less than 2.0%, it is not possible to obtain stone at elevated temperatures, and its content of more than 8.5% reduces the pumpability and setting time.

The characteristics of grouting mixtures prepared according to the recommended ratios of the components are given in table 2. As can be seen from table 2, pumpability at a preparation temperature (22 ° C) is in the range 1.7-2.0 hours, and at a bottom temperature (75 ° C) ) - 10-12 hours, which ensures the manufacturability of the proposed mixture.

Example 1 preparation of the cement mixture.

In 70 cm ^{3 of} brine (NaCl) sodium chloride, a specific gravity of 1.18 g / cm ^{3 was} introduced sequentially 100 g (CaSO ₄ · 0.5N ₂ O) calcium sulfate (alabaster), 15 g of "Microdur 261R-X", 0 12 g of NTF and mixed thoroughly. The result was a grouting mixture, which had the following indicators:

- density - 1.735 g / cm ³ - spreadability - 19 cm - pumpability at t = 22 ° С - 1 hour 40 minutes - setting start at t = 22 ° С - 2 hours 05 minutes - end of setting at t = 22 ° C - 2 hours 45 minutes - volume expansion - up to 2% - gas permeability - 0.03 10 ^-3 microns

Thus, the above recipe allows for 1 hour to prepare the grouting salt composition on the surface, pump it into the face, and then at the bottom at a temperature of 75 ° C for 3 days to get a strong salt grouting stone.

The use of the proposed cement mixture gives the following advantages:

- the field of using salt-based cement slurry is expanding, since it has sufficient pumpability and setting time, which ensures its adaptability when working in oil and gas wells, including when: attaching casing strings, installing insulating bridges, creating fluid-resistant tires and screens ;

- the efficiency of the insulation works is increased due to the increased fluid resistance and durability of the resulting cement stone, especially in conditions of difficult water exchange, due to its composition close to the chemogenic deposits of rocks in the work interval, which is stable under conditions of hydrogen sulfide and salt aggression.

All this ultimately will increase the reliability of reservoir separation during well construction and reduce the likelihood of vertical fluid filtration from saline productive horizons.

The technical and economic effect, depending on the type of work being carried out, the lithological section of the rocks and the depth of the well will be added (determined) from the absence of the need for repeated isolation procedures.

Table 1 №№ The composition of the mixture, in wt.% Density, g / cm ³ Spreadability, cm Test temperature, T = ° C Thickening, h-min, P _m = 100 Setting time, h-min p / p CaSO ₄ NaCl brine Microdur NTF Start end one 2 3 four 5 6 7 8 9 10 eleven one 54.73 45.21 - 0.06 1,615 24.5 22 after 24 hours did not seize, the experiment was terminated 75 after 24 hours did not seize, the experiment was terminated 2 54.75 45.22 - 0,03 1,62 24.5 22 0-55 1-00 1-25 75 after 24 hours did not seize, the experiment was terminated 3 54.76 45.23 0 0.01 1,615 22.5 22 0-25 0-45 1-00 75 after 24 hours did not seize, the experiment was terminated four 51.91 42.88 5.19 0.02 1.71 18.0 22 0-30 0-45 1-00 75 4-20 4-50 5-45 5 51.90 42.87 5.19 0.04 1.71 18.0 22 0-45 1-00 1-10 75 > 8-00 > 8-00 > 8-00 after 24 hours the stone 6 51.89 42.87 5.19 0.05 1.71 18.5 22 1-00 1-10 1-25 75 > 8-00 > 8-00 > 8-00 after 24 hours the stone

Continuation of table 1. one 2 3 four 5 6 7 8 9 10 eleven 7 51.35 42,42 6.16 0,07 1,725 19.0 22 2-20 2-40 3-05 after 3 days, σ _compress. = 13.73 kg / cm ² 75 > 8-00 > 8-00 > 8-00 after 24 hours the stone Three samples were installed in the bath to form a stone at T = 75 ° C: the first immediately after mixing, the second 30 minutes after mixing and the third 60 minutes after mixing. The compressive strength after 1 day is 1-σ _cr = 2.20 kg / cm ² , 2-σ _cr = 2.64 kg / cm ² , 3-σ _cr = 2.05 kg / cm ² After 3 days, the compressive strength is 1-σ _cr = 11.67 kg / cm ² 2-σ _cr = 10.98 kg / cm ² , 3-O _cr = 10.98 kg / cm ² one 2 3 four 5 6 7 8 9 10 eleven 8. 50.58 41.78 7.59 0.05 1,735 19.0 22 1-40 2-05 2-45 75 > 8-00 > 8-00 > 8-00 after 24 hours the stone Three samples were installed in the bath to form a stone at T = 75 ° C: the first immediately after mixing, the second 30 minutes after mixing and the third 60 minutes after mixing. After 3 days, the compressive strength is 1-σ _SJ = 21.28 kg / cm ^2, _SJ-σ 2 = 24.03 kg / cm ^2, 3-σ _SJ = 24.03 kg / cm ² 9. 60.0 39.88 - 0.12 1.83 <10 22 mixture not pumped 10. 55.0 34.88 10.0 0.12 1.85 <10 22 mixture not pumped eleven. 50.58 41.78 7.59 0.06 1,735 19 22 1-40 2-05 2-45

Claims (1)

Grouting mixture containing calcium sulfate and water, characterized in that the water is in a brine of sodium chloride with a specific gravity of 1.18 g / cm ³ , as calcium sulfate grouting mixture contains semi-aquatic gypsum and additionally a hardener additive in the form of a finely divided mineral substance " Microdur-26RC "and nitrilotrimethylphosphonic acid NTF in the following ratio of components, wt.%: Semi-aquatic gypsum 50.00-53.95 Mikrodur-26RС 2.00-8.50 Indicated pickle 41.42-44.00 NTF 0.05-0.08