SU1476112A1 - Method of isolating water inflow in wells - Google Patents

Abstract

The invention relates to the oil industry and can be used to isolate the flow of formation water in oil wells. The goal is to increase the efficiency of the insulation by preventing the erosion of the compositions during their structuring. Two isolating compounds with adjustable setting time are injected into the well. Compositions that are autonomously cured in volume are used as insulating compounds. The setting time of the first composition is not less than the time of injection into the reservoir of both compositions. The setting time of the second composition is not less than the setting time of the first composition. The setting time of the compositions is controlled by the mass ratio of the components and is adjusted in accordance with the time of injection and displacement into the formation. The composition of the compositions with a given setting time (structuring) is selected experimentally, taking into account the influence of the reservoir temperature. The preparation of the compositions is carried out before carrying out the isolation works. 2 tab.

Description

measures of partially hydrolyzed polycate acid (PMAC) - Flocul nt Comet with a hardener - aliphatic epoxy resin type TEG-1 and other compositions

For the preparation of the second composition, time-thickened mg materials can also be used: polymer solutions, for example, CMC, clay suspensions, etc.

The setting and structuring time of the compositions is regulated by the weight ratio of the components and is selected in accordance with the time of their injection and injection into the reservoir. The composition of the compositions with a given setting time (structuring) is selected experimentally, taking into account the influence of the reservoir temperature. The preparation of the compositions is carried out before carrying out the insulation works.

The first composition is selected with a setting time (structuring) sufficient for injection into the formation of the planned volume of the two insulating compositions. After injection into the reservoir of the second composition, the first composition sets and prevents destruction and erosion by the formation waters of the first composition and the entire backfill screen. The second composition has a time of structuring (setting) equal to or greater than the time of injection of the entire planned amount of plugging materials, which ensures safe conditions for pumping plugging compounds into the reservoir and prevents them from setting in the wellbore during movement in the bottomhole formation zone. In addition, this allows for final work in the well (flushing, lowering pumping equipment, etc.) immediately after pushing a second train into the reservoir, which minimizes the loss of time to repair the well and simple equipment. Thus, after the injection and structuring of materials, a hydro-screen is formed in the reservoir, the peripheral part of which forms the first composition and the central one - the second. This ensures reliable isolation of the reservoir in the entire volume of the grouting screen.

The minimum volume (V) of isolating compositions is selected depending on the required radius of the hydraulic screen, which is able to withstand the pressure drop (depression) during the operation of the well.

The volume of the first insulating composition is chosen on the basis that in the period before the complete structuring of the second composition does not occur, destruction in the erosion of the hydraulic screen, i.e. so that its peripheral part, formed by the first composition, maintains an overpressure (P - Ppl) after the end of injection and displacement of reagents.

Taking the radial nature of the filtration of injected fluids (insulating compositions), the volume of materials is calculated as follows:

V

v + va,

(one)

V is the minimum volume of insulating compositions, m3; V (is the volume of the first insulating

composition, m3; V. - the minimum volume of the second

insulating composition, m3

V2 1H (K2) p - rc-J,

(2)

de h - thickness of the isolated formation, m;

R2 is the required radius of the central part of the hydraulic screen formed by the second insulating composition, m;

p - porosity (steam) or fracture coefficient (fracture) layer, units;

g - well radius, m

- R.

grad P

- L.

(3)

Where

Рпл - formation pressure, MPa;

P is the pressure at the bottom of the operating well, MPa;

L - width of the first rim

 plugging composition, m; grad P is the pressure gradient of the shear of the second insulating composition after setting (structure formation), which is determined according to laboratory data on reservoir models, MPa / m,

L

P - P

c Јn

grad P,

- pressure at the bottom of the well after its treatment (injection of insulating compositions), MPa; - reservoir pressure, MPa;

- the shear pressure gradient 1 of the first insulating composition after structure formation, which is determined according to laboratory data on reservoir models, MPa / m.

V (| hn (2R) 2 - (2R2) S (5)

where R is the radius of the entire hydraulic screen, m, equal to:

R N „+ L

Taking into account that when the injected material reaches a reservoir, having a viscosity close to that of reservoir fluids, it mixes up to 7% of its volume at the interface with the reservoir fluid, in this case the volume of the first insulating composition calculated by the formula (5) should be increased 7% of the total volume of the first and second

The volume of the second insulating composition V2 may be larger than the minimum volume calculated by formula (2) and is determined according to the data of experimental treatments, which allow to take into account the nature of the fracture of the formation to prevent the water-screen from bending around.

The results of evaluating the effectiveness of the method of isolating water inflow are presented in Table. one.

Tests were carried out on models

reservoir.

i

The models were cylinders (tubes) with a length of 600 mm and a diameter of 25 mm filled with carbonate rock (limestone) with a granule diameter of 1.0-2.5 mm. The total volume of injection of the compositions corresponded to the pore volume of the model - 600 cm3.

Based on the presented in table. 1 data can be done

one -

20

25

, 35

40

50

gg

45

26

The fact that the effectiveness of the method in the initial period (immediately after the injection of the compositions) is determined by the stability (strength) of the hydraulic screen at high pressure drops (0.6-1.2 MPa), due to the structuring and high pressure gradient of the compositions after injection into the reservoir.

During the complete structuring of the compositions, the efficiency of the method is determined by the fact that the gel formation of the compositions occurs in the entire threshold volume of the model and is autonomous, i.e. regardless of their interaction with each other. This is confirmed by the large values of pressure gradient, material shear, and model plugging.

Example. It is necessary to isolate water inflow in a well that has exposed a fractured layer 5 m thick. The depth of the roof of the reservoir is 2500 m, the reservoir temperature is 40 ° C, the fracture coefficient of the formation rocks is 0.01, the reservoir pressure is 32 MPa, the planned bottomhole pressure after injection of insulating compositions 36 MPa, well radius 0.07 m

As an insulating material, a composition based on a copolymer — flocculant Comet with a hardener — alfatic epoxy resin TEG-1 and a bentonite solution on fresh water of 10% concentration are used. The shear pressure gradient for the cracks of the first and second compositions is 1.5 and 0.25 MPa / m, respectively. The total volume of insulating compounds, calculated by formulas (1), (2) and (5), is 160 m3, including the first composition 25 m3 and the second 135 m3. Since the viscosity of the first composition (floc nt Comet + TEG-1 resin) is 10-15 MPa-s (i.e., 15 times more than the produced water), it will not be significantly diluted with water during injection, which means , the increase in the volume of the first composition is impractical. The volume of flow liquid is 25 m3.

For injection of compositions it uses with the TsA-320 unit “When the TsA-320 unit operates on the IV transmission with a sleeve diameter of 100 mm and a flow rate of 9 l / s for pumping 185 m3 of working solutions

714

(25 me of the first formulation, 135 m3 of the second formulation, and 25 m3 of propellant) will take 5 hours and 50 minutes. Therefore, according to the method that involves setting the first composition after pumping and pushing into the reservoir the entire planned volume of the first and second compositions, the setting time of the first composition should be 5 h 50 min, and the second setting time should be no less than the setting time of the first.

Laboratory experiments carried out the selection of formulations to ensure the implementation of the method. In tab. Table 2 shows the results of laboratory studies of the gel formation of the first plugging composition (based on flocculant Comet and TEG-1 resin) and the time of thickening (swelling) of a 10% aqueous solution of bentonite clay in fresh water at 40 C.

From tab. 2 it follows that the specified conditions correspond to the first composition with a flocculant Kometa content of 8%, TEG-1 resin 5% and water 87% (gelation time 6 h) and the second composition 10% bentonite solution on fresh water ( thickening time 24 h).

The sequence of the method is as follows.

The CA-320 unit and the process tanks for the insulating compositions are connected to the wellhead. Preparing with fresh water a 135 m3 bentonite solution of 10% concentration. Then, an insulating composition 1 is prepared. To prepare a 25 m 3 insulating composition having a density of 1050 kg / m 3

eight

2100 kg of Shock Nta Comet should be mixed with 21.8 m3 of fresh water until a homogeneous solution is obtained, then 1320 kg of TEG-1 resin are introduced into the solution and mixed for 10 minutes. Then 25 m3 of composition 1 and 135 m3 of composition 2 and 25 m3 of pumping fluid (oil, water) are pumped into the well in succession. “After 10-15 min. You can begin the final work in the well (flushing, raising the filling pipes, lowering the pumping equipment, etc. .), without fear of erosion and destruction of the plugging screen.

Thus, this method of isolating water inflows in oil wells allows increasing the efficiency of the formation plugging.

Claims (1)

Invention Formula A method of isolating water inflows in oil wells, including sequential injection into the well of two insulating compositions with adjustable setting time, characterized in that, in order to increase the isolation efficiency by preventing erosion of the compositions during their structuring, the following are used as insulating compositions autonomously cured in volume, the setting time of the first composition is not less than the time of injection of both compositions into the formation, and the setting time of the second composition is not less than the setting time neither the first part table 2 Induction period (time from preparation to gelation) of a composition based on flocculta Kometa, TEG-1 resin and water with different content of components and thickening (swelling) time of a 10% aqueous solution of bentonite clay in fresh water Editor AO Lezhnina Compiled by L. Bestuzheva Tehred M. Didyk Order 2138/31 Circulation 515 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 Production and publishing plant Patent, Uzhgorod, st. Gagarin, 101 Corrector Girn to Subscription