RU2260674C1 - Sealing composition to prevent gas and/or liquid migration inside channels of cemented support cavities in gas, gas condensate and gas-oil wells and method for using the same - Google Patents

Abstract

FIELD: oil and gas industry, particularly to prevent fluid migration in channels of the support in working, nonworking or conserved state.

SUBSTANCE: composition includes saponified tall oil pitch, condensed spent sulfite-alcohol liquor and water preheated up to 85-96°C. The components are taken with the following amounts (by weight): saponified tall oil pitch - 35-40;, condensed spent sulfite-alcohol liquor 15-25; and preheated water - remainder. Composition may additionally include dispersed mineral or organic filler taken in amount of 5-80% by weight counting on composition mass. The composition may be used to isolate crack-porous beds during well drilling or as buffer solution during casing pipe cementation.

EFFECT: prevention of gas migration due to forming sealing screens and prevention of fresh headwater and atmosphere pollution, as well as elimination of fire and explosion hazard in neighboring territories.

4 cl, 2 ex, 2 tbl

Description

The invention relates to the oil and gas industry and can be used to eliminate the migration of fluids in the channels of the cemented spaces of the lining of wells in operation, idle time and conservation, as well as cementing casing while drilling.

From the patent SU 1661360 dated 07/07/1991 a method is known for eliminating casing leakage by pumping into the annulus a suspension containing a gelling agent - saponified tall pitch (15-25 wt.%), Gel precipitator - aqueous solutions of calcium chloride with the addition of acetic acid (2 -3 wt.% By weight of a solution of calcium chloride), the filler is bentonite clay powder (1.5 wt.%). According to this method, the mixture (suspension) is pumped into the gas medium between the specified column and the column of elevator pipes. The mixture flows freely along the inner walls of the production string; the films of this mixture by the pressure drop of the gas from the annulus to the annulus are pressed into the labyrinth of the leaky thread, sealing it to a gas-tight state. This composition is not intended to eliminate leaks due to the presence of channels in the cemented space.

From patent SU 911017 dated 03/07/1982, a viscoelastic composition for siege column grouting is known containing condensed sulphite-alcohol stillage (16-17 wt.%), Sodium dichromate (6.5-8.0 wt.%), Caustic soda (1 -1.5 wt.%) And water (the rest). This composition is used only to separate the cement from the drilling fluid and to displace mud residues from the cemented spaces, i.e. as a cleaner, it cannot perform the functions of shielding (sealing) migration channels in already cemented well supports.

From SU 1773092 dated 02.20.1996, a composition is known for the selective isolation of water inflow into a well containing saponified tall pitch (15-35 wt.%), Sulfanol (0.5-2.0 wt.%), Sodium hydroxide (0.5- 2.0 wt.%) And water (the rest). The composition is used only for the isolation of formations with mineralized waters.

Known cementless cement grout containing saponified tall pitch (0.3-7.2 wt.%), Salt solution (0.03-2.9 wt.%), Water (the rest) (SU 1232783, 1983), not creating volumetric structures (precipitated). Well-known grouting solutions containing sulphite-alcohol stillage, cement and water, as well as various target additives (bentonite, iron nitrate) (SU 492646, 11/25/1975; 881229, 11/15/1981).

Well-known grouting solutions are used for cementing oil and gas wells or for isolating absorbing layers of Portland cement and are not suitable for eliminating migration channels in cemented spaces, because the cause of the migration channels is cement itself, which during the hardening process forms permeable vertical channels in the surrounding medium.

A powdery drilling fluid reagent obtained from tall oil pitch, lignosulfonates, sulphate liquor, caustic soda, carboxymethyl cellulose is known from RU 2012770. This reagent is used to process drilling fluid while drilling for oil and gas.

The closest in technical essence to the claimed group of the invention is a known sealing composition comprising saponified tall pitch (18-25 wt.%), Powdered condensed sulphite-alcohol stillage (2-4 wt.%), Water (the rest).

Additionally, it may contain dispersed fillers (chalk, bentonite, asbestos, barite, etc.) (SU 1504331, 08/30/1989).

However, this composition is used as a sealing composition for absorbing formations with mineralized waters; at the same time, in order to obtain insulation, formation water (calcium chloride type) with a density of 1200-1300 kg / m ^{3 is} pre-pumped into the absorbing layer. Such injection into a depressurized well support is contraindicated from the point of view of contamination of the upper fresh (drinking) water, in addition, the used ratios between saponified talc pitch and condensed sulphite-alcohol stillage in the first 20 minutes do not create (even with a maximum content of 25 wt.% And 4 wt.%, Respectively) of the required strength of the structure, and therefore cannot provide a reliable gas-tight screen.

The technical task of the claimed invention is to eliminate the migration of fluids (gas and liquid) in the channels of the cemented space of the support gas, oil wells by the formation of sealing screens that prevent gas filtration in the cemented intercolumn spaces of gas, gas condensate and gas-oil wells, which creates excessive pressure (RMS) in the mouth these spaces, as well as the release of gas to the surface beyond the outer casing, which leads to contamination of the upper fresh water , The atmosphere, and also poses a threat of explosions and fires in the surrounding areas.

The stated technical problem is achieved by the fact that the sealing (screen-forming) composition for eliminating the migration of gas and liquid in the channels of the cemented spaces of the well supports includes saponified tall tar pitch, condensed sulphite-alcohol stillage and water preheated to 85-95 ° C in the following ratio of components , wt.%:

saponified tall oil pitch (OTP) 35-40 condensed sulphite-alcohol bard (KSSB) 15-25 water preheated to 85-95 ° C rest

The group of the claimed invention includes the use of this sealing composition for the following purposes:

- when cementing casing strings, how to divide (buffer) the medium in order to improve the replacement of the drilling fluid (its crust) with the grout and to prevent (reduce) the channel formation in the cemented space;

- for the quick passage of drilling drained porous-fractured formations and formations with water-gas manifestations (regardless of the type of mineralization and its magnitude) without large losses of time to overcome the complications that arise;

- when stopping wells for overhaul without the usual loss of productivity during subsequent commissioning.

The essence of the claimed invention is as follows.

Near the well, a necessary volume of water (taking into account condensed steam) with a temperature of 85-95 ° С is prepared using a mobile steam unit (PPU), into which OTP is gradually loaded (filled) from the bag, while dispersed KSSB is introduced at the same time (if it arrived separately). After homogenization, the mixture with or without filler is immediately pumped into the open annular spaces of the well by an aggregate connected to a pressurized injection line. Upon reaching the pressure on the unit 30-50 kgf / cm ² annular spaces are closed, the unit is turned off.

Typically, the injection process takes 10-15 minutes. Therefore, the recipe provides for obtaining a screen-forming composition with maximum structural, mechanical and sealing properties by a given time (see Tables 1 and 2).

When using the sealing screen-forming composition according to the invention with a different ratio of components, first of all, attention is drawn to the influence of the temperature effect on the screen-forming properties of the OTP. With its 25% aqueous solution, cooling from 80 to 20 ° C makes it possible to increase the viscosity from 7 to 75 · 10 ^-4 Pa · s, and at a similar temperature difference in a 40% solution, the viscosity jump reaches from 10 to 600 · 10 ^-4 Pa · from.

In the formed screen (cooling is accelerated in most wells due to insignificant volumes of micro- and macro-channels in the cemented space), the strength of the structure with the proposed increased ratio of 35-40% OTP (instead of 25%) and 15-20% KSSB (instead 2-4%) after 12-30 minutes of its formation, it increases by measurements on the device of static shear stress (SSS) by an order of magnitude higher than 2.2566 instead of 0.0-0.1158 (see table. 1). Such strength of the screen structure allows avoiding the development of migration channels for gas to penetrate in the screen itself, i.e. in the newly created in the channels of the cemented space of the well (see table. 2) and thereby maintain the integrity of the screen at the very beginning of its creation. And by seven days, the strength of the structure according to the SNA with the addition of a weighting agent reaches ~ 5.4 Pa, chalk ~ 4.5 Pa, bentonite ~ 3.4 Pa.

It is known that the larger the diameter of the technical casing strings, the more probable the leakage of their threads and the cement sheath behind these strings and the migration of formation fluids through them. This circumstance determines the use of mixtures 3a and 3b for reconstructing the tightness of the indicated elements behind the production casing by simultaneous injection or sequential injection of the first 3a, followed by 3b or single-port injection of mixture 2 (see Table 1). To eliminate migration (in threads and cement shells) behind the second or first intermediate technical columns, mixture 1 is used without filler (or with the addition of bentonite, gypsum, vermiculite, asbestos, sawdust). In the event that the source of gas and liquid migration has an abnormal pressure, weighting agents (chalk, dispersed limestone, barite, hematite) are added to the composition (mixture 1 or 2).

The following tables 1 and 2 show examples of compositions of the invention and their properties.

The great advantage of the composition according to the invention is that in order to avoid contamination of fresh water in a geological section, preliminary injection into the annular spaces of solutions of calcium chloride, magnesium or titanium chlorates with a density of up to 1300 kg / m ³ or formation water of calcium chloride type with a density of up to 1200 kg / m ^{3 is} not produced. Coagulation of the mixture of components in order to create a strong structure of the sealing screen in the loose threads of the casing strings, in the channels of the cement ring (sheath) behind the casing strings occurs during the interaction of the colloidal part of the OTP with the sodium salt formed by sodium sulfate, resulting from the chemical reaction of sulfuric acid with alkali:

H ₂ SO ₄ + 2NaOH → Na ₂ SO ₄ + 2H ₂ O,

contained in the components of the mixture (in the OTP residual alkalinity of up to 10.5%; as part of KSSB contains up to 42% alkali and up to 15% sulfuric acid).

For the same purposes, if necessary, the screen-forming composition may contain dispersed filler: bentonite swelling in an alkaline medium, finely divided chalk and weighting agents, which allows a sealing screen column in the gas migration channels (with an anomaly coefficient of 1.1-1.3 at Rpl 150- 500 kgf / cm ² ) eliminate Rmk reaching 100-120 kgf / cm ² . Thus, the claimed sealing composition helps to eliminate the migration of gas (and liquid) in the channels of the cemented spaces of the lining of the wells when interacting in them sequentially or parallel to the injected components or their mixture, provides sealing of the permeable channels formed on the path of the migration flows by gas-tight screens with rapidly increasing structural strength.

Examples of the preparation of the composition during the construction of the well for the isolation of porous-fractured formations and as a buffer solution for cementing casing strings at the rate of 1 m ^{3 of the} finished mixture.

Example 1. Preparation according to the scheme 40-15-45 (mixture 1).

200 l of fresh water is taken into the hopper of the unit, which is brought to 90 ° C with the help of PPU, and 400 kg of OTP and KSSB are poured into it; in the process of their homogenization and dissolution at the indicated temperature, the amount of water due to condensate increases by another 250 liters. After injection into the column and delivery to the zone of porous-fractured formations, the mixture is crushed in them. If necessary, the resulting screen is supplemented with a cement-carbonate swab with 70% chalk (or ground limestone) by a.s. 199057, which is especially important when shielding incoming water into reservoirs to maintain their productivity.

Example 2. Preparation according to the scheme 35-20-45 (mixture 2).

The sequence of operations is preserved, only OTP and KSSB fall asleep 350 and 200 kg, respectively. After pumping the prepared mixture into the cemented casing, they begin to pump the grout, at the time of the release of the buffer solution, i.e. It acquires the maximum elastic-structural properties in the annular space, which allows, due to the increased displacement ability, to clean the drilling fluid with a relatively small height of the cleaning ring from the mixture (150-50 m) in the annular and annular spaces. The wetting of the cement-wall contacts of the cemented space with the ion-active mixture filter filter causes the swelling of the ion-exchange complex in clinker minerals during hardening, which largely compensates for the shrinkage in the cement stone due to surface ion-exchange processes.

Table 1
Examples and properties of the composition according to the invention. Mixture Properties The composition recipe, wt.% Dispersion additive Density Static shear stress, SNA 1/10 0.2 hours after preparation No. OTP KSSB Water -% of the mixture kg / m ³ Pa 1 40 fifteen 45 - 1035 2.2566 / 4.9441 2 35 twenty 45 - 1030 1,9901 / 4,8132 3a 40 - 60 - 1015 0/0 3b - twenty 80 - 1010 0/0 3 40 twenty 140 - 1005 0.9920 / 3.8432 4 40 fifteen 45 Hematite-80 1350 3.0726 / 3.2416 5 35 twenty 45 Mel-30 1050 1.7021 / 1.8030 6 40 fifteen 45 Bentonite-5 1045 2,3124 / 2,976 Prototype I 25 2-4 73-71 - 1020 0.0-0.1158 / 0.4052 * II 25 2-4 73-71 Barite-60 1250 0.0-0.3278 / 0.3576 * III 25 2-4 73-71 chalk 20 1025 0.0-0.1192 / 0.1490 * IV 25 2-4 73-71 Bentonite-10 1030 0.0-0.0363 / 0.1258 * * - SNA 1/10 0.5 hours after preparation

table 2
The effect of composition on the permeability of migration channels after their 10-minute treatment. The composition of the mixture, which processed the channels with a permeability of 20 · 10 ^-10 m ² The change in the permeability of the migration channels treated with the mixture, 1 · 10 ^-13 m ² in time after injection of the screening composition, through Mix No. additive to the mixture of dispersed filler -% Day 7 days 1 - 1.55 0.00 2 - 1.38 0.00 3 - 1.97 0.09 4 Hematite - 80 0.10 0.06 5 Chalk - 30 0,03 0.00 6 Bentonite - 5 0.00 0.00 The rate of decrease in permeability after treatment at a temperature of 65 ° C was 2 times higher than at a temperature of 18 ° C Prototype** I - 1.76 - II Barite - 60 0.28 *** - III chalk - 20 0.05 *** - IV Bentonite - 10 0.00 *** - ** - data after 2 treatments of the reservoir model for 5 minutes, before each treatment it was saturated with calcium chloride with a density of 1300 kg / m ³ *** - when heated to 70 ° C, the formation of channels in the screen, i.e. it is depressurized

Claims (4)

     1. The sealing composition to eliminate the migration of gas, liquid in the channels of the cemented spaces of the lining of the wells, including saponified tall oil pitch, condensed sulphite-alcohol stillage and water pre-heated to 85-95 ° C, in the following ratio, wt.%: Saponified Tall Peak-OTP 35-40 Condensed sulphite-alcohol barda-KSSB 15-25 Water, pre heated to 85-95 ° C Rest 2. The sealing composition according to claim 1, characterized in that it further comprises a dispersed mineral or organic filler in an amount of 5-80 wt%. based on the weight of the composition. 3. The use of the sealing composition according to claim 1 for the isolation of porous-fractured formations in the process of drilling wells. 4. The use of the sealing composition according to claim 1 as a buffer solution for cementing casing strings.