RU2204710C1 - Method of water inflow shutoff in gas well - Google Patents

Abstract

FIELD: gas producing industry. SUBSTANCE: in known method of water inflow shutoff in gas well including injection, into well after its shut-in at rated rate, of liquid hydrocarbons with additives of surfactant with their delivery to preset zone of well perforation interval and putting the well into operation after definite period of time, preliminarily injected into well is double-soluble surfactants in the form of modifiers and forced into formation by gas, then liquid hydrocarbons with additives of surfactants-emulsifiers and again forced by gas. Modifiers are used in the form of substances of alcohol-acetone or glycol series. Coltubings are used for delivery of reagents and provision of rated rate of reagent injection. Technical result of invention application consists in higher efficiency of shutoff by increase of adhesion of hydrocarbons (used for water inflow shutoff) to walls of pore channels of reservoir, increase of waterless phase of well operation without repair-and-shutoff worn. EFFECT: higher efficiency. 3 cl

Description

 The invention relates to the gas industry, in particular to isolate water inflow in a gas well.

 A known method of isolating water inflows in gas wells, including the injection of cement slurry through tubing while maintaining the liquid level in the annulus of the well at a certain depth (see SU 1758219 A2, 1992).

 The difficulty in continuously monitoring the liquid level in the annulus of the well and the lack of control over the process of pumping cement in the presence of a packer in the well limit the application of this method in many gas and gas condensate fields.

 There is a method of isolating bottom water in a gas well, in which after stopping the well with a liquid pump, a certain volume of oil with a high content of asphalt-resinous substances is pumped into the bottomhole zone, and then it is pressed for a long time deep into the reservoir. Then the well is put into operation (see Khatmullin F.G. et al. The use of oils for drying and hydrophobizing the bottom-hole zone of gas wells. Gas Industry, 2, 1974, pp. 29-31).

 Using the known method extend the anhydrous period of operation of gas wells in gas storages created in aquifers.

 The disadvantage of this method is that when watering a small part of the exposed hole in gas wells, the injected oil penetrates all gas-saturated interlayers, since the depth of oil penetration into each permeable interlayers depends on the total volume of oil injected into the well and the ratio of the permeability coefficients of the interlayers in the perforation interval. To treat wells with long perforation intervals, large volumes of oil must be pumped, the sale of which over long distances must be carried out for a long time using compressor stations.

 Also known is a grouting composition for isolating permeable formations containing polymer, acetone and a nonionic surface-active substance (surfactant), the so-called A-formation, used in gas wells (see US Pat. RF 2046180, E 21 B 33/138, 1995) .

 However, this method also has a number of drawbacks consisting in technological complexity and requiring significant costs, and in most cases cement bridges are installed to consolidate the effect.

 Of the known methods, the closest in our opinion is the method of isolating bottom water in a gas well according to the patent of the Russian Federation 2136877, Е 21 В 43/32, 33/143, 1999, which includes pumping into the tubing after stopping the liquid hydrocarbon well and putting it into operation wells after a certain time, while the calculated amount of liquid hydrocarbons is injected in portions, at certain intervals, and spent oil products with surfactant additives that promote hydrophobization are used as liquid hydrocarbons reservoir rocks in the bottomhole zone. In addition, liquid hydrocarbons are injected when traces of produced water appear in the production of a gas well.

 However, this method gives a short-term effect of water isolation due to the low adhesion of the used water-repellent hydrocarbons to the walls of the pore channels of the reservoir, it does not provide selectivity and control over the absorption of hydrocarbons by the selected layer in the case of the location of the “shoe” of tubing in the roof of the perforation interval.

 To eliminate this drawback in the method of isolating water inflow in a gas well, which includes injecting liquid hydrocarbons into the well after stopping it at the estimated speed of liquid hydrocarbons with surfactant additives, delivering the well to the specified perforation interval and putting the well into operation after a certain time, bi-soluble surfactants are preliminarily injected into the well - modifiers, push them into the formation with gas, then pump liquid hydrocarbons with additives of surfactant emulsifiers and again push them with gas.

 As modifiers, substances of the alcohol-acetone or glycol series are used.

 At the same time, for the delivery of reagents and ensuring the estimated speed of injection, count-tubing is used.

 As a bi-soluble surfactant, for example, technical acetone according to GOST 2768-84, technical methanol according to GOST 2222-84, ethylene glycol, diethylene glycol can be used.

 Synthetic fatty acids (FFA) of fractions C 16 - C 22 according to TU 38.507-63-285-92 can be used as surfactant emulsifiers.

To expand the scope and increase the efficiency of work after stopping the well and gaining static pressure in the number of tubing, the “shoe” of which is installed in the bottom of the interval selected for processing the formation, with continuous supply at a speed that provides a given dynamic level, the calculated amount of bi-soluble surfactants is pumped -modifiers and displace them with gas in a remote zone of the reservoir. In the process of interaction of the surface of the pore channels with the pumped liquid, the wettability character changes, i.e. surface modification, which subsequently provides a sufficient level of adhesion of hydrocarbons to minerals that make up the reservoir. Liquid hydrocarbons are injected according to a similar scheme, and oil products with the addition of surfactant emulsifiers are used as liquid hydrocarbons, which contribute to the formation of second-type emulsions at the formation water-hydrocarbons contact. The hydrocarbons used to ensure the necessary injection into the well are brought to a certain consistency by dilution with lighter fractions and heated, and the density of the prepared hydrocarbons is in the range of 0.78-0.82 g / cm ³ at 20 ^o C.

 This goal is achieved in that the limitation of water inflow in the treated formation occurs under the influence of two factors: a change in the phase permeability of the reservoir (deterioration in water and improvement in gas) and the formation of emulsion screens as water is introduced.

 In large floating Cenomanian gas deposits, perforation intervals in active wells reach 40-60 m. The productive gas-saturated stratum in these deposits is represented by heterogeneous rocks with highly permeable layers in different parts of the productive section. Significant removal of produced water from existing gas wells, at which their operation is practically impossible, occurs when the planting water is introduced to the lowest highly permeable layer, regardless of its thickness.

To ensure selectivity, according to the proposed method, the flow rate of liquids is determined by selecting the injection mode, in which the pressure in the annular space remains equal to static, and the steady-state dynamic level does not overlap the upper superconducting layer, the interval of which is determined by the injectivity profile or geological model. The dynamic level is controlled by the injection pressure; for this, the absorption pressure is determined experimentally with a minimum flow rate, and by calculation, the permissible excess over this pressure is determined by the formula
R _p = (N _about -N _p ) • p, where N _about - the depth of the roof of the treated layer, m; N _p - the depth of the sole of the upper superconducting layer, m; p is the density of the liquid, kg / m ³ ; P _p - permissible excess pressure, MPa.

So, when processing the interlayer, the roof of which is at a depth of 1260 m, and the sole of the upper superconducting interlayer is 1200 m, with hydrocarbons with a density of 800 kg / m ^{3, the} permissible excess pressure will be
P _n = (1260-1200) • 800 = 0.48 MPa.

 Due to the small cross-section of the count-tubing, the injection process is precisely controlled to prevent overflow of the perforation interval with a working fluid, and when using adjustable bypass devices to a given pressure, they are fully automated, which allows us to conclude that the criteria of "inventive step" and "novelty" are met.

 Further, the hydrocarbon mixture for uniform distribution along the walls of the pore channels is displaced by gas to the periphery of the formation for 3-5 days, after which the well is launched into the production pipeline with periodic sampling of the liquid phase and, in the absence of hydrocarbons, gas-dynamic studies are carried out.

 In the Urengoy field, in order to limit the inflow of bottom water in production Cenomanian wells, work was carried out using a mixture of oil and gas condensate with the addition of a surfactant emulsifier with the following results.

 PIP conclusion for the well 174.

In comparison with the PIP data obtained during the study, before treatment, an increase in the total gas production rate from 271.98 to 471.6 tm ³ / day is observed, with a decrease in the depression on the formation σР = 1.8 atm.

The inflow of water into the well from the bottom due to the rise of the GWC, which was previously observed, is not currently observed. As a result of the work, the mineralization of water from 2331.93 mg / dm ³ before treatment decreased to 710 mg / dm ³ .

PIP conclusion for well 1111
According to PIP data, when compared with previous studies, there is a change in the boundaries of the intervals of inflow and flow rate entering the gas well. With the same depression on the formation (dP-1.23 atm.) From the bottom of the perforated interval, which previously worked with a maximum flow rate (Q-146.77 tm ³ / day), the gas production rate is insignificant. The gas flow rate coming from the top of the perforated interval increased without changing the total flow rate of the well. As a result of the work, the mineralization of water from 2200 mg / dm ³ before treatment decreased to 760 mg / dm ³ .

Claims (3)

 1. A method of isolating water inflow in a gas well, including pumping into the well after stopping it at an estimated rate of liquid hydrocarbons with the addition of surfactants with delivery to the specified zone of the perforation interval of the well and putting the well into operation after a certain time, characterized in that bi-soluble surfactants - modifiers are injected into the well, they are pushed into the formation by gas, then liquid hydrocarbons with surfactant-emulsion additives are pumped Hur and again forced gas.  2. The method according to p. 1, characterized in that as the modifiers use substances of alcohol-acetone or glycol series.  3. The method according to p. 1, characterized in that for the delivery of reagents and ensure the estimated speed of injection using count-tubing.