RU2322472C1 - Technological liquid for damping oil and gas hole and method for its preparing - Google Patents

Abstract

FIELD: oil and gas extracting industry.

SUBSTANCE: invention relates to damping holes in their overhaul repair. Proposed technological liquid used in damping oil and gas holes comprises the following components, wt.-%: microbial xanthane biopolymer, 0.5-2.0; modified starch, 0.2-2.5; surfactant (surface-active substance), 0.01-0.2; sodium carbonate, 0.1-1.0; aluminum power, 0.005-0.08, and water, the balance. Method for preparing indicated aphron-containing technological liquid used in damping oil and gas holes involves mixing its components to obtain two solution wherein one solution contains sodium carbonate and surface-active substance obligatory, and other solution contains aluminum powder. Mixing these solution is carried out at temperature from 50^°C to 90^°C. Invention provides preparing aphron-containing liquid for damping under static conditions without using special gas-dispersing equipment and based on available reagents.

EFFECT: improved and valuable technical properties of liquid.

2 cl, 3 tbl, 3 ex

Description

The invention relates to the oil and gas industry, in particular to killing wells during their overhaul.

Muffling liquids during repair work must meet certain requirements regarding their optimal filtration and viscosity characteristics, the ability to control structural and mechanical properties, preserve the reservoir properties of the bottomhole formation zone, the availability of composite components, etc.

The main types of process fluids used in modern practice of killing wells are the following:

1) calcium chloride solutions [1-3], the main disadvantages of which are coagulation of clay particles and precipitation of insoluble sediments of mineral salts in the formation filtration channels, increased water saturation in the bottom-hole zone of the well and a decrease in the flow rate of wells, which is confirmed by the technical and economic analysis [4];

2) technological liquids on an oil (hydrocarbon) basis [5–9], the general disadvantages of which include the non-standard physical and chemical properties of oil, the need to use a complex of reagents to regulate and stabilize the technological properties of hydrophobic-emulsion solutions, the fulfillment of a number of environmental and fire safety when using petroleum-based solutions;

3) compositions of polysaccharide gels for killing wells, as well as foaming compositions using a mixture of surfactants, modified starches or biopolymers, as well as various fillers as colmatants - aluminum hydrosol, CaCO ₃ , etc. [10-12]. These fluids are of limited use, in particular, they cannot be used for killing wells in fields that have entered the late stage of development and are characterized by abnormally low reservoir pressures (ANPD), due to the fact that the component composition of these fluids does not provide foaming sufficient to form a stable foam system with a low density, which is necessary for killing wells in the conditions of the API. The addition of chalk suppression (CaCO ₃ ), salts, and other solid-phase particles to the killing fluid as colmatants enhancing the blocking properties makes the well development process even more difficult. This is due to the fact that during well development, the extraction of such a fluid, which has stained the formation, is possible only with high depressions, i.e. high release pressure, which is completely unacceptable for fields with an API. In such cases, to dissolve the chalk that has caked the formation, one has to resort to acid treatment, which leads to a significant increase in the well development time and a decrease in the recovery coefficient of the permeability of the productive formation.

To prevent the above complications, technological fluids have been developed that have an abnormally high viscosity at low shear rates and have high pseudoplasticity. Usually they are colloidal solutions of biopolymers, in particular microbial polysaccharides, in a concentration of from 0.5 wt.% To 2 wt.% [13]. A distinctive feature of pseudoplastic solutions is that they have an exceptionally high shear stress at rest, which can decrease tens of times with active stirring. Suspensions of solid particles prepared on the basis of colloidal biopolymers are extremely stable, which helps to prevent the formation of sediment, for example, when the drilling tool stops, as well as in horizontal or inclined sections of the wells. Another distinctive feature of pseudoplastic solutions is that they have low penetrating properties when filtered into the reservoir zone.

In recent years, drilling fluids and process fluids have been developed that do not contain solid-phase mechanical filtration reducers, and which include aphrons - microscopic gas bubbles with a diameter of 20-100 microns, protected by a complex two-layer shell consisting of thickened water and surface-active substances (surfactants) [fourteen]. For the first time, their description, like the term “aphrons,” was given by F. Sebboy [15].

The main difference between aphrons and ordinary foams is that they are surrounded by two-layer shells with an intermediate layer of water, while the shell of an air bubble in ordinary foam consists of a single monomolecular surfactant layer. Due to the small size and specific structure, aphrons have (compared to foam bubbles) high mechanical strength and stability.

The American patent [14], which should be considered as a prototype of the proposed process fluid and a prototype of the proposed method for its preparation, describes the composition and method of preparation of the technological solution based on polymer additives and specially selected surface-active components, which are a group of empirically selected synthetic surfactants. As an active principle, it is proposed to use, in particular, sodium dioctyl sulfosuccinate, the proprietary surfactant Chubb National Foam-High Expansion, which is part of the Blue-Streak reagent, manufactured by M-I Drilling Fluids, and some other expensive and inaccessible components. The described synthetic surfactants make it possible to obtain stable microbubble gas inclusions that reduce the total density of solutions. The advantage of the latter, in comparison with conventional foams, is that aphrons easily pass even through small cells of a vibrosieve, and under the influence of centrifugal forces in hydrocyclones and a centrifuge they float and separate together with a clean solution. Due to its small size and high strength, aphrons do not affect the operation of mud and centrifugal pumps compared to foams and are fully compatible with telemetry systems using a hydraulic data transmission channel. Due to the elasticity, hydrophobic nature of the outer surface of microbubbles and their conglomerates (from tens of microns to several millimeters), aphrons are capable of reversibly clogging a wide range of permeable media - from low permeable sandstones to fractured limestones with permeability of tens of Darcy, forming a kind of protective shell on their surface. The prototype composition has neutral or alkaline pH values achieved by the introduction of various components and, in particular, sodium carbonate.

The main advantage of aphrons over other colmatizing agents is that they do not form irreversible crusts and a blocking screen on the surface and in the collector itself and easily dissociate into the solution when stress is removed. In well-known compositions of drilling fluids, aphrons are generated under the influence of high mechanical stresses and cavitation, for example, in centrifugal pumps, hydraulic nozzle bits, hydraulic mixers, hydrocyclones, during compression and decompression of a fluid at the moment of movement in a wellbore, etc.

The use of well-known afron-containing process fluids in the practice of killing wells, although it seems promising, is complicated by the fact that the process of incorporating air bubbles into the liquid phase occurs only with its active dispersion and simultaneous capture of air. Such processes are natural if an afron-containing fluid is used as a drilling fluid, i.e., it continuously circulates in the wellbore through a gradient of hydrostatic pressure, through vibrating screens, centrifugal pumps, and at the same time mixes, trapping air in open technological tanks. The static use of the process fluid, for example, to kill the well, does not create conditions for autogeneration of aphrons and requires the installation of additional gas dispersing equipment, which significantly increases the cost of well repair.

Solved by the proposed group of inventions, the task and the expected technical result are to develop a composition and method for preparing an afron-containing killing fluid in static conditions without the use of special gas dispersing equipment based on available reagents.

The problem is solved in that the afron-containing technological fluid for killing oil and gas wells, including water, a surface-active component - surfactant, sodium carbonate and stabilizing and regulating additives in the form of microbial xanthan biopolymer, modified starch, is characterized in that it additionally contains aluminum powder, the following ratio of components, wt.%:

Microbial Xanthan Biopolymer 0.5-2.0 Modified Starch 0.2-2.5 Surfactant 0.01-0.2 Sodium carbonate 0.1-1.0 Aluminum powder 0.005-0.08 Water Rest

The problem is also solved by the fact that the method of preparation of the aforementioned afron-containing technological fluid for killing oil and gas wells involves mixing its components to obtain two solutions, one of which necessarily contains sodium carbonate and surfactant, and the other contains aluminum powder, and mixing these solutions at temperatures from 50 ° C to 90 ° C.

Under alkaline conditions created by the presence of soda ash, aluminum powder reacts with water under appropriate temperature conditions, possibly directly in the formation, with the formation of hydrogen microbubbles protected by a complex two-layer shell consisting of thickened polysaccharide components of water and surfactants, etc. e. aphrons.

The proposed method for preparing such an aphron-containing technological fluid for killing wells consists in separately preparing two solutions, one of which (an “activator”) necessarily contains an alkaline ingredient and a surface-active component, and the other (“processor”) includes aluminum powder.

The afron-containing process fluid itself is prepared by simply mixing the two indicated solutions - “activator” and “processor” - in one tank before feeding it into the well with preheating to a temperature of plus 50 ° C - plus 90 ° C or directly in the well due to geothermal heating .

The proposed aluminum-alkaline blowing agent is cheap, affordable and environmentally friendly product, while the solutions of the "activator" and "processor" separately can be stored for a long time in a stable state, and the generation of aphrons will occur only after mixing inactive components and after heating the activated solution or in the tank, or in the wellbore at a temperature above 30 ° C. The use of aluminum-alkaline gas formation is known and widely used, in particular, in the manufacture of cellular concrete [16]. At the same time, there is no information in the specialized literature on the formation of aphrons in thickened polysaccharide solutions containing aluminum and soda and not subjected to mechanical dispersion. Therefore, the claimed solution, according to the authors, meets the criterion of "inventive step".

The possibilities of the invention can be illustrated by the examples below.

Example 1. Illustrates the formation of aphrons after adding aluminum powder and sodium carbonate to the stock solution.

A stock solution was prepared containing microbial xanthan biopolymer of the Rodopol brand 1.0 wt.%, Modified Fito-RK starch (TU-2483-002-4166845222-97) - 2.0 wt.%, Surfactant - sodium lauryl sulfate - 0.025 wt. .% (TU 6-09-64-75) and tap water - 96.975%.

Anhydrous sodium carbonate additives (TU 2131-002-44267537-2001) in the concentration range of 0.1-1.0 wt.%, As well as aluminum powder additives (GOST 5494-95) in the concentration range of 0.005 - 0 were added to the portion of the base solution. , 08 wt.%. The resulting liquids were subjected to thorough mixing and heating at 80 ° C for 40 minutes.

The formation of aphrons (microbubbles of hydrogen) was evaluated by the density of the obtained solutions, measured by standard methods in 25 ml pycnometers at 20 ° C and atmospheric pressure. The measurement results are summarized in table 1.

Table 1. The formation of gas-dispersed systems in solutions after adding aluminum powder and sodium carbonate No. The concentration of additives, wt.% The increase in fluid volume due to the formation of a gas phase (vol.% Under normal conditions) The density of the solution at 20 ° C, g / cm ³ Anhydrous Sodium Carbonate Aluminum powder one 0 0 0 1,0301 2 0.1 0.005 5D 0.9800 3 0.2 0.01 9.7 0.9389 four 0.3 0,03 25,2 0.8227 5 0.4 0.05 40.1 0.7352 6 1,0 0.08 69.7 0.6069

Example 2. Illustrates the stability of a microbubble solution obtained by classical technology using mechanical dispersion of air (similar to the prototype), and aphron solution obtained by the method of generating hydrogen bubbles from aluminum powder.

Prepared stock solution according to the recipe shown in example 1.

To generate aphrons by dispersing the solution, a portion of it was placed in a closed metal glass of an MPW-302 blender and subjected to three mechanical stirring. The time of one treatment was 3 minutes, the rotation speed of the blender was 18000 min ^-1 , the interval between operations was 15-20 minutes. Dispersion of gas (air) occurred due to the capture of large air bubbles from the surface of the liquid under the influence of a knife of a high-speed blender.

To generate aphrons using aluminum powder and soda, an additive of anhydrous sodium carbonate (TU 2131-002-44267537-2001) at a concentration of 0.4 wt.%, As well as an addition of aluminum powder of 0.05 wt.% Were added to a portion of the base solution (GOST 5494-95). The resulting liquid was subjected to thorough mixing and heating at 80 ° C for 40 minutes.

The resulting solutions, containing microbubble dispersions of gas (air and hydrogen) in a mixture of basic reagents, were transferred to glass containers equipped with ground lids, and thermostated at various temperatures for a long time. To prevent evaporation of water from the aqueous layer of liquid, liquid hexadecane (5-10 mm) was layered on top. At fixed time intervals determined by the experimental conditions, liquid samples were removed from under the hexadecane layer using a pipette, dosed into graduated piconometers, thermostated at 20 ° C, and the density was measured by the gravimetric method. The results of measurements of the densities of the experimental samples obtained during the 10-day experiment and presented in table 2 indicate a higher stability of gas-dispersed systems obtained as a result of the reaction of aluminum powder with sodium carbonate.

Table 2. Temperature stability of gas dispersed. systems in solutions obtained mechanically (M) and chemically using aluminum powder (A) No. Exposure conditions Aphron Generation Method The density of the solution (g / cm ³ ), measured at 20 ° C after exposure of the mixture for, h 0 12 24 72 144 240 one Control solution T = 22-25 ° C - 1,026 1,026 1,026 1,026 1,026 1,026 2 Temperature 12-15 ° С M 0.6056 0.7916 0.8825 0.9714 1,0050 1,0154 3 Temperature 22-25 ° С M 0.6056 0.8084 0.9106 0,9914 1,0081 1,0116 four Temperature 32 ° С M 0.6056 0.8566 0.9701 0,9952 1,0141 1,0172 5 Temperature 43 ° С M 0.6056 0.8993 0,9916 0.9591 1,0012 1,0151 6 Temperature 12-15 ° С BUT 0.7312 0.7332 0.7336 0.7330 0.7342 0.7339 7 Temperature 22-25 ° С BUT 0.7312 0.7340 0.7340 0.7340 0.7340 0.7331 8 Temperature 32 ° С BUT 0.7312 0.7339 0.8712 0.9845 0,9956 1.009 9 Temperature 43 ° С BUT 0.7312 0.7465 0.9815 0,9981 1,0015 1.018

Example 3. Illustrates possible variations in the composition of two solutions - “activator and“ processor ”. Microbubble systems are generated by mixing equal volumes of two solutions - an “activator and a“ processor ", prepared separately for each of the options.

Table 3. Variants of mixtures for generating microbubble systems prepared by mixing equal volumes of two solutions - “activator and“ processor ”. Component Name Variants of solution No. 1 (“activator”) Variants of the solution ("processor") No. 2 one 2 3 four one 2 3 four Microbial xanthan biopolymer, wt.% 0.85 1.25 1.7 0.65 0.85 1.25 0.65 1.7 Modified starch, wt.% 0.1 0.3 0.5 1,0 0.1 0.3 0.5 1,0, Sodium carbonate, wt.% 0.2 0.6 0.6 2.0 0 0 0 0 Aluminum powder wt.% 0 0 0 0 0.001 0.01 0.08 0.16 Surfactant, wt.% 0.01 0,025 0.1 0.2 0 0 0 0 Water, wt.% 48.84 47,825 47.1 46.15 49,049 48.44 48.77 47.14

Information sources

1. RF application No. 2003121616.

2. RF application No. 2003126134.

3. RF patent No. 2250360.

4. Pop G.S., Kucherovsky V.M., Geresh P.A. Technical and economic analysis of the effects of technological fluids on the bottomhole zone of productive formations of gas condensate fields // Overview. Ser. Development and operation of gas and gas condensate fields. - M: IRC Gazprom, 1995 .-- 101 p.

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7. RF patent No. 2264531.

8. RF patent No. 2258802.

9. RF application No. 2005108303.

10. RF patent №2246609.7.

11. RF application No. 2005108303.

12. RF patent No. 2266394.

13. Andreson B.A., Gibadullin N.Z., Gilyazov P.M., Kondrashev O.F. Physico-chemical principles of the use of polysaccharide drilling fluids for well completion - Ufa: Monograph, 2004. - 247 p.

14. US patent No. 5881826.

15. Felix Sebba, "Foams and Biliquid Foams-Aphrons," Virginia Polytechnic Institute and State University, pp 62-69, 1987.

16. F.Vavrzhin, R. Krchma. Chemical additives in construction. M .: Stroyizdat, 1964, 287 p.

Claims (2)

1. Afron-containing technological fluid for killing oil and gas wells, including water, a surface-active component - surfactant, sodium carbonate and stabilizing and regulating additives in the form of microbial xanthan biopolymer, modified starch, characterized in that it additionally contains aluminum powder in the following ratio of components, wt .%: Microbial Xanthan Biopolymer 0.5-2.0 Modified Starch 0.2-2.5 Surfactant 0.01-0.2 Sodium carbonate 0.1-1.0 Aluminum powder 0.005-0.08 Water Rest 2. The method of preparing an afron-containing technological fluid for killing oil and gas wells according to claim 1, comprising mixing its components to obtain two solutions, one of which necessarily contains sodium carbonate and surfactant, and the other contains aluminum powder, and mixing these solutions at a temperature of from 50 to 90 ° C.