RU2017947C1 - Compound for treatment of bottom-hole formation zone of gas-condensate field - Google Patents

Abstract

FIELD: oil and gas producing industry. SUBSTANCE: compound contains, mas. %: ammonium hydrocarbonate 14-15; VZhS flotation agent 0.5-1.0; the balance, water. Compound under conditions of formation temperature above 60 C and absence of flooding of bottom-hole zone with waters of calcium and magnesium chloride types features high dissolving properties. EFFECT: higher efficiency. 2 dwg, 5 tbl

Description

 The invention relates to the gas industry, and more specifically to physico-chemical methods of intensifying gas and condensate production of gas condensate fields (HCM) at a late stage of their development.

 A known composition for processing the bottom-hole zone of a well containing gas condensate with oil and surface-active substances (surfactants) (see ed. St. USSR N 269873, class E 21 B 43/20, 1968).

 A known composition for processing the bottom-hole zone of a well containing a hydrocarbon phase, water and an additive - surfactant (see. The use of micellar solutions to increase oil recovery in flooding. "Reviews of foreign literature". M., 1975, S. 13-15).

 However, the scope of these compositions is limited due to insufficient solvent capacity. The disadvantages include the fact that the main components used in the compositions are expensive gas condensate and oil.

The closest technical solution, the prototype of the proposed composition is a composition for processing the bottom hole of the well, the main components of which are the hydrocarbon phase (gas condensate, oil) and water, and rosin is added to increase the dissolving ability, and alkali is added as an additive in the following ratio of components wt. %: Hydrocarbon phase 20-40 Alkali 0.1-0.5 Rosin 0.1-0.5 Water Else
Studies on the restoration of permeability of the bottom-hole zone on bulk models have shown that this composition, intensively mixing and dissolving blocking water, activates and accelerates the dissolution of high molecular weight oil components, reduces the time required for soaking the fluid at the bottom, ensuring well operation immediately after completion process.

 The disadvantage of this composition is its multicomponent, high consumption of the hydrocarbon phase, the use of scarce rosin, and insufficient solvent capacity.

 The aim of the present invention is to increase the solubility of the composition and the efficiency of cleaning the bottom-hole zone of the well from bound water and condensate that has fallen from the formation pressure drop, and, consequently, improved permeability and increased gas condensate production from the formation.

To achieve this, in a known composition for treating the bottom-hole zone of a gas condensate field formation, which includes injecting an aqueous solution of a reagent containing a surfactant, carbon dioxide, alkali and water, according to the invention, into the bottom-hole zone, free from flooding with potassium chloride water magnesium chloride and pumped type chemically bound carbon dioxide and ammonia which, under the effect of formation temperature above 60 ^{° C} during the decomposition of the reactant are precipitated as gaseous dd carbon monoxide and aqueous ammonia.

Another difference is that as the injected aqueous solution of the reagent, an aqueous solution of bicarbonate (bicarbonate) and ammonium carbonate and surfactant is used, for example, VZhS flotoreagent in the following ratio of components, wt.%: Bicarbonate (bicarbonate) and ammonium carbonate 14-45 VZhS flotoreagent 0.5-1.0 Water Else
(85.5-54.0)
An aqueous solution of ammonia is a good alkali that helps to clean the bottom-hole zone of bound water, and gaseous carbon dioxide, dissolving in the condensate, increases its mobility, which generally ensures effective cleaning of the bottom-hole zone of the well. In the presence of flooding with stratal waters of calcium chloride and chloromagnesium type, the proposed method is not applicable due to the possible clogging of productive formations resulting from the reaction of chalk sediment.

(H₄)₂CO₃·H₂O+CO

, где τ - время
(NH₄)₂CO₃·H₂O

(NH₄)₂CO₃+H₂O
(NH₄)₂CO

2NH₃+H₂O+CO

Флотореагент ВЖС - кубовый остаток высших жирных спиртов, попадает в водный раствор гидрокарбоната (бикарбоната) и карбоната аммония в количестве 0,5-1,0 мас.% при их получении при очистке природного газа от двуокиси углерода, где он вводится для достижения большой эффективности очистки газа, и оптимальное содержание флотореагента ВЖС установлено было при этом в пределах 0,5-1,0 мас.%. При обработке призабойной зоны скважин флотореагент ВЖС играет роль ПАВ, снижающего контактное поверхностное натяжение. В нашем примере водный раствор бикарбоната и карбоната аммония не приготовляется специально, а является побочным продуктом очистки природного газа от двуокиси углерода. Но он может быть приготовлен и специально из порошкообразных бикарбоната и карбоната аммония и обработан флотореагентом ВЖС. Сопоставительный анализ предлагаемого технического решения с прототипом показывает, что предлагаемый состав отличается от известного тем, что заканчиваемые в призабойную зону находящиеся в водном растворе гидрокарбонат (бикарбонат) и карбонат аммония разлагаясь в пластовых условиях, выделяют помимо аммиака, являющегося хорошей щелочью и диоксид углерода, который, растворяясь в выпавшем в призабойной зоне конденсате, увеличивает его подвижность.The chemical decomposition reactions are as follows:
2NH ₄ HCO

(H ₄ ) ₂ CO ₃ · H ₂ O + CO

where τ is time
(NH ₄ ) ₂ CO ₃ · H ₂ O

(NH ₄ ) ₂ CO ₃ + H ₂ O
(NH ₄ ) ₂ CO

2NH ₃ + H ₂ O + CO

VZhS flotoreagent - distillation residue of higher fatty alcohols, gets into an aqueous solution of bicarbonate (bicarbonate) and ammonium carbonate in an amount of 0.5-1.0 wt.% When they are obtained when purifying natural gas from carbon dioxide, where it is introduced to achieve great efficiency gas purification, and the optimal content of flotation reagent VZhS was established at the same time in the range of 0.5-1.0 wt.%. When processing the bottom-hole zone of wells, the flotation reagent VZhS plays the role of a surfactant that reduces contact surface tension. In our example, an aqueous solution of bicarbonate and ammonium carbonate is not specially prepared, but is a by-product of the purification of natural gas from carbon dioxide. But it can also be prepared specially from powdered bicarbonate and ammonium carbonate and treated with flotation reagent VZhS. A comparative analysis of the proposed technical solution with the prototype shows that the proposed composition differs from the known one in that the hydrocarbonate (bicarbonate) and ammonium carbonate that end up in the bottomhole zone decompose under formation conditions, in addition to ammonia, which is a good alkali, carbon dioxide, which , dissolving in the condensate deposited in the bottomhole zone, increases its mobility.

 From a comparative analysis of the prototype and the proposed technical solution it follows that the proposed composition meets the criteria of the invention of "novelty."

 A well-known pilot experiment on the injection of liquid carbon dioxide in order to intensify gas condensate production at well No. 1 of the Timofeevsky gas condensate field of the Poltava gas production department (GPU). (See the article "Processing of the bottom-hole zone of a gas condensate well with carbon dioxide", R. M. Ter-Sarkisov, M. A. Peshkin, E. S. Bikman, VNIIgaz, Ukrniigaz in the journal "Oil and Gas Industry" Kiev, publ. Technique N 1, 1989, 33-35 p.).

 Well N 1 of the Timofeevskoye oil and gas condensate field was cased with a column ⌀ 146/140 mm; artificial slaughter - 3886 m, perforation interval 3834-3866 m, tubing ⌀ 73 mm lowered to a depth of 3825 m.

The B-16 formation in the well area has a porosity of 16%, a permeability of 21.4 ppm (21.4 21 10 ^-15 m ² ), gas saturation of 83%, and an effective thickness of 10 m.

For the period of the well’s operation from 1978 to 1987, before the stimulation work was carried out, the reservoir pressure decreased and amounted to R _pl = 16 MPa, and the flow rate at a working pressure of P _slave = 5-6 MPa was 20-25 thousand m ³ / day.

 The injection of liquid carbon dioxide into the well began on September 29, 87, and with interruptions (due to the uneven supply from the Lokhvytsky distillery at a distance of 90 km, it continued until November 13, 1987, i.e. 1.5 months).

 After the injection was completed, carbon dioxide was pumped for 12 hours by gas from a 50-Timofeevka well with a pressure of 16 MPa.

After 10 days, 1-Timofeevka well was put into operation. Well productivity at P _slave = 5-6 MPa was 50-55 thousand m ³ / day, i.e. increased by about 2 times.

 Thus, according to the method performed in the pilot industrial experiment for well No. 1 of the Timofeevskoye gas condensate field, carbon dioxide is used in liquid form, which necessitates the use of isothermal tanks, and in our composition carbon dioxide is used in a chemically bound form and, therefore, can transported by conventional tankers. In addition, in our composition, bicarbonate (bicarbonate) and ammonium carbonate, decomposing under reservoir conditions, in addition to carbon dioxide and ammonia, which is a good alkali, contributes to the removal of bound water and clogging particles, which together allows us to conclude that the proposed technical solution criterion of "significant differences".

 VZhS flotoreagent according to TU-38-107103-76 has the following composition,%: NaOH - not less than 0.5 (0.8-1.6); fatty acids - not less than 40 (in relation to the organic part); unsaponifiable substances 15-24. The qualitative characteristics of the flotation reagent VZhS are given in table 1.

 Physical properties of flotation reagent VZhS.

VZhS flotoreagent is characterized by inconsistency of composition, as can be seen from the data in table 1. Has a high pour point, which depending on the composition ranges of 5-20 ° ^C. At temperatures above the pour point is a dark brown oily liquid density of 1.06 g / cm ^3. The beginning of the boil is 100 ^o C.

 In this technical solution to the problem, the primary reagent is hydrocarbonate (bicarbonate) and ammonium carbonate, and the VZhS flotation reagent is secondary, acting as a surfactant that reduces the surface tension of the solution, and can be replaced by another surfactant, for example, stabilized hydration precipitate (hydrofuse) TU-18- 17 / 70-86 obtained by processing unrefined vegetable oils with steam condensate at oil and fat plants in the country, while maintaining the same% ratios.

 PRI me R. The implementation of the composition in a laboratory setting.

As a model of reservoirs subjected to laboratory research, core material from oil and gas fields of the Dnieper-Donets Depression (DDV) was used. Sandstones of 16 pieces, with a diameter of 30 mm, a length of 30 mm, absolute permeability (51-1326) x 10-15 m ² (51-1326 ppm) and open porosity from 9.5 to 22.7%.

Preparing sandstone samples (cylinders) for the study of the complex was performed on normal laboratory equipment, extraction - in a Soxhlet apparatus, the release of moisture - in the oven (105 ° ^C), saturation of fluids - a vacuum apparatus, weighing - analytical balance type VLA -200. The density of the fluids was determined by the pycnometric method (pycnometers with a volume of 50 ml), and the viscosity was determined by a capillary glass VPK-3 viscometer with an internal diameter of 0.56 mm. At the laboratory installation UIPK, which provides heating of core samples to maintain a certain temperature with a TC thermostat with coolant-water and measuring the temperature with a thermometer, dosing the liquid supply under a certain pressure and measuring pressure with standard pressure gauges, the volume and flow rate of the displaced and suppressed liquid according to the measuring burette and gas drum hours, on core samples by a known method, data were obtained and the coefficients of displacement and residual saturation by kerosene for displacing liquids were determined firs hydrogencarbonate aqueous solution (bicarbonate) and ammonium carbonate and formation water, as well as to gas (air) at temperatures of the heating core 30, 40, 50, 60, 70 ^o C.

 The experimental results are shown in Table 2, which gives the average experimental results for all the studied sandstone samples.

 It can be seen from the data in Table 2 that, over the entire temperature range, the highest displacement coefficient of kerosene is achieved if an aqueous solution of hydrogen carbonate (bicarbonate) and ammonium carbonate is used as a displacing liquid, a lower displacement coefficient for produced water and the lowest displacement coefficient for gas ( air). Correspondingly, the smallest residual saturation of the sample with kerosene when displaced by a solution of hydrogen carbonate (bicarbonate) and ammonium carbonate, more when displaced by formation water, and even more when displaced by gas (air). This proves the feasibility of using an aqueous solution of ammonium bicarbonate in the proposed composition.

 The absolute (gas) permeability of core samples pre-treated with kerosene was also determined before and after processing with an aqueous solution of ammonium bicarbonate. The research results are given in table.3.

 From the data table. Figure 3 shows that after processing core samples with a solution of ammonium bicarbonate, permeability increases.

The boundary content of bicarbonate (bicarbonate) and ammonium carbonate in an aqueous solution is determined, firstly, based on the fact that the higher the concentration of these reagents in the solution, the greater the effect of intensification is expected. Secondly, the content of these reagents in the solution is determined by the dependence of their solubility on the temperature of the solution (see Fig. 1), on which graphs of the temperature dependence of the solubility of bicarbonate (bicarbonate) NH ₄ HCO ₃ and carbonate (NH ₄ ) ₂ CO ₃ ammonium in water). Thirdly, less stable ammonium bicarbonate at a temperature of 39 ^{° C} and above partially decomposed into ammonia (NH _3), water and carbon dioxide (CO _2), which escapes from the solution, which is undesirable, and partially reconverted to carbonate and ammonium carbonate . Then, the boundary and optimal content of bicarbonate (bicarbonate) and ammonium carbonate, based on the usefulness of their possibly highest concentration in solutions, will be determined by the boundary and optimal temperatures for the preparation of these solutions, the intake of these solutions into a tank truck for delivery to the well, and injection of these solutions into the well, which (temperature) should be kept between +10 ^о С - +35 ^о С. And the optimum temperature will be +20 ^о С. The authors also established the dependence of the change in the surface tension of water a solution of flotation reagent VZhS from its concentration in the range of 0.05-2.0 wt.%. With an increase in the concentration of the flotation reagent VZhS, the surface tension of the solution decreases from 70.0 × 10 ³ n / m (dyne) to 42.0 × 10 ³ n / m (dyne). When the concentration of flotation reagent VZhS in the range of 0.5-1.0 wt.% The dependence curve is almost equalized, i.e. a further increase in the content of VZH does not significantly change the surface tension.

 Therefore, 0.5 wt.% Is taken as the lower boundary content of the VZhS flotation reagent, 1.0 wt.% As the upper boundary content, and 0.7 wt.% As the optimum. Then the boundary and optimal content of the main components of hydrocarbonate (bicarbonate), ammonium carbonate and flotation reagent VZhS, providing a technical solution to the problem will be as follows.

 PRI me R 2. Implementation of the composition in the field using the example of well N 58 Timofeevsky gas condensate field of the Poltava gas production department.

 Geological and technical characteristics of the well.

 Production casing ⌀ 168/140 mm - 4270 m, cement lifting height - 362 m from the mouth, tight. Artificial Slaughter - 4246 m.

 Perforation intervals: 3888-3858 m, 3820-3810 m, 3798-3792 m. Productive horizon: B-16-B-17.

The reservoir is highly cemented sandstone, porosity is 7-20%, the total thickness of gas-saturated formations is 21.4 m. Pump-compressor pipes (tubing) ⌀ 73 mm grade R 110x5.51 mm are lowered to a depth of 3844 m, tubing volume is 11.6 m ³ . Fountain fittings: AF6M-50x700. Putting the well into operation - September 1984. Initial parameters of the well (on 18-20.10.84):
P _pl = 32.5 MPa, T _pl = 95 ^about C, P _article = 29.5 MPa,
Q _gas abs.sv. = 576 thousand m ³ / day. Current well parameters (as of July 25, 1990):
R _{pl. Current.} = 10.45 MPa, P _article = 7.6 MPa,
Q _{gas working} = 106.1 thousand m ³ / day., Gas condensate factor (GKF) = 106.1 kg / thousand. m ³ ; gas-water factor (GVF) = 5 l / thousand m ³ . Water is sodium bicarbonate, condensation, ρ = 1.001 g / cm ³ . Prior to stimulation, well N 58 was investigated into a production reservoir for productivity along a research line with gas flow rate measurement by a DSS-736 field flow meter.

 The research results are presented in the following table.5.

Then, 10 m ^{3 of an} aqueous solution of bicarbonate (bicarbonate) and ammonium carbonate treated with 0.5-1.0 wt.% VZhS flotation reagent was calculated at well N 58 at the rate of 0.5 m ^{3 of} solution per 1 meter. effective power of the processed filter interval. Ammonium bicarbonate solution temperature was 20 ^{° C} and the maximum concentration of the reagent in the solution was 18.6 wt. % (see figure 1). The concentration of the reagent in the solution was determined in the chemical laboratory. Made work on intensification. At pressures at the wellhead P _Tr = 6.0 MPa, P _Zat = 5.8 MPa, 10 m ^{3 of an} aqueous solution of hydrogen carbonate (bicarbonate) and ammonium carbonate were pumped into the tubing with the CAA-320 closed annular unit. The maximum injection pressure is 9.5 MPa, the minimum is 1.8 MPa. Then, gas from another well with a pressure of 15.0 MPa was used to inject the solution into the formation for 16 hours and 45 minutes. After that, the production laboratory repulsed the liquid level in the well and measured the temperature at the bottom. Bottomhole temperature was 96 ° ^C. The liquid in the well was not, i.e. the entire solution was forced into the reservoir. We blew the well onto the flare for 1 hour. The well worked with wet gas, then, for 6 minutes, removed a portion of liquid from condensate and degassed water with a total volume of 1 m ³ and then worked with wet gas. The well was put into operation at the GPP. After 20 days, well No. 58 was examined for productivity in the field reservoir along the research line with measuring the gas flow rate with the DSS-736 field flow meter. At a pressure at the inlet to the gas treatment plant R _I = 6.0 MPa, the gas production rate was 122.85 thousand m ³ / day. The initial increase in production amounted to
[122.58- (66.28 + 80.56) / 2] = 49 thousand m ³ / day.

 Technical and economic effectiveness of the proposed technical solution was expressed in the following.

 The initial flow rate after intensification increased compared with the flow rate before intensification by 1.66 times, i.e.

[122.58 thousand m ³ / day: (66.28 + 80.56) / 2) thousand m ³ / day].

Repeated studies of well N 58 for productivity were carried out after 35, 29, and 28 days, respectively. Research data on the determination of flow rates before and after stimulation, the implementation of the intensification and change in the flow rate of gas wells in time are shown in figure 2. This made it possible to determine the duration of the stimulation effect, which for the well N 58 amounted to about 5-6 months. Additional gas and condensate production in the well amounted to: 4998 thousand m ^{3 of} gas and 539.3 tons of condensate.

The advantages of the proposed composition for processing the bottom-hole zone of the gas condensate field (GCM) in comparison with the known following:
increasing the efficiency of cleaning the bottom-hole zone from the precipitated condensate due to carbon dioxide and ammonia released during the decomposition of bicarbonates;
additional increase in gas condensate production due to better cleaning of the bottomhole zone;
the ability to do without the expensive hydrocarbon phase and rosin.

Claims (1)

COMPOSITION FOR TREATING A BOTTOM ZONE OF A GAS-CONDENSATE DEPOSIT LAYER containing a surfactant, alkali and water, characterized in that, in order to increase the efficiency of processing the bottom-hole zone by increasing the solvent capacity of the composition at formation temperatures above 60 ^° C and in the absence of flooding of the bottom-hole zones with calcium and chlorine-magnesium type waters, it contains VZhS flotation reagent as a surfactant, and ammonium bicarbonate (bicarbonate and carbo ammonium nat) in the following ratio of components, wt.%:
Ammonium bicarbonate (bicarbonate and carbonate) 14 - 45
VZhS flotoreagent 0.5 - 1.0
Water Else

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