RU2645058C1 - Method for development of high-viscous oil deposit with cyclic steam soaking - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: invention relates to oil deposits development. Method for developing a high viscosity oil reservoir by steam cycling involves drilling a vertical well into high viscosity oil pools, fastening a vertical well with a casing string, casing perforating in the production formation interval, pumping through the well into the productive reservoir of the combined-cycle heat transfer medium, launching the tubing string with the pump into the well, and selecting the heated products from the well. Perforation in the interval of the productive formation, folded by carbonate rocks, is produced by a hydro-sandblast perforator with the formation of perforations with a diameter of 20 mm. After that, a proppant foam acid fracturing of the formation is carried out with the formation of a fracture by injecting a gelled fracturing fluid, followed by its development and fastening in five stages alternating batches of foam acid in equal volumes and foam acid with the addition of a proppant mixture of 2 tons each in each stage consisting of 12/18 mesh coarse proppant and 12/16 mesh cylindrical proppant in a percentage ratio of 60/40, at each subsequent stage, the concentration of the proppant mixture is increased stepwise from 200 to 600 kg/m³ in increments of 100 kg/m³, and the concentration of acid in the foam is not less than 16 %. To reduce heat losses at the beginning of the steam cyclic action, the well is warmed by circulating the steam until the condensate is removed from the return line, a pipe string with a bottom-up non-return valve, a locking support of the plug-in rod-type pump, a by-pass valve, a packer is lowered into the borehole, a pipe string is placed in the well, so that the packer is in front of the roof of the upper part of the productive formation, then the rod-type plug-in pump is lowered into the column of pipes on the rod column and fixed in the lock support. After that, the well is pumped in a volume of 40 tons per day for 14 days, after which the well is closed and kept for 14 days for impregnation, then the heated high-viscosity oil is withdrawn. After lowering the production rate to a cost-effective level for a given well, the steam injection cycles and the selection of the heated high-viscosity oil are repeated.

EFFECT: technical effect: increase in the coverage of the deposit, increase in the efficiency of the steam-thermal effect on the reservoir, increase in the selection of the heated high-viscosity oil after the steam cyclic action, elimination of overheating of the upper part of the reservoir, and reduction of heat losses along the well bore.

1 cl, 3 dwg, 1 tbl

Description

The invention relates to the field of development of oil fields and can be used for the production of highly viscous oil with a parocyclic effect on the reservoir, composed of carbonate rocks.

There is a method of developing deposits of high viscosity oils by heat and steam (patent RU No. 2361074, IPC EV 43/24, publ. 07/10/2009, bull. No. 19), including the injection of alternating rims of the reagent solution, under the influence of temperature decomposing with the release of carbon dioxide , and a couple. Urea is used as the indicated reagent, the solution is injected through a steam-cyclic production well with at least two rims, after the last rim of the steam is injected, the oil rim is injected, the indicated well is kept for impregnation, and then it is put into operation, while the specified solution additionally contains ammonium nitrate , ammonium thiocyanate, complex surface-active substance (surfactant) Neftenol VVD, or a mixture of non-ionic surfactant - AF9-12, or NP-40, or NP-50 and anionic PA - volgonata or sulfonol, or NPS-6.

The disadvantages of the method:

- firstly, the low efficiency of the steam and thermal effects on the reservoir, since the implementation of the method does not determine the permissible pressure of steam injection into the well depending on the carbonate or terrigenous rocks. The permissible steam injection pressure, depending on the type of rock, is of the utmost importance when developing a highly viscous oil deposit by means of steam pressure, therefore, when implementing this method, the formation (roof) of the formation is likely to break through the pressure of the vapor injection, and, as a result, the vapor leaves the other horizon , on the other hand, with insufficient steam pressure, the formation will not be completely covered by the steam-thermal effect, which also reduces the volume of the steam chamber;

- secondly, the low quality of the steam-thermal effect on the formation with a highly viscous oil with a reagent solution, which is used as carbamide, which has a corrosive effect in the well, in addition, its dissolution in water (steam condensate) is an endothermic reaction, which is accompanied by a decrease in temperature in the formation . In addition, chemicals are injected into the formation separately without mixing at the wellhead, which can lead to an uncontrolled chemical reaction in the formation of highly viscous oil;

- thirdly, a decrease in the reservoir properties of the formation, since together with the injection of steam, a large number of chemicals are simultaneously pumped: urea, ammonium nitrate, rhodanum ammonium, a complex surfactant, etc .;

- fourthly, high heat loss, since the coolant (steam with chemical reagents) is pumped into the reservoir with highly viscous oil through the annulus and the heated reservoir cools quickly due to the lack of sealing during the implementation of the method. As a result, the temperature in the reservoir rapidly decreases to the initial one, and the viscosity of the oil increases.

The closest in technical essence and the achieved result is a method of cyclic exposure to a bottom-hole zone of a formation with viscous oil by steam-gas coolant (patent RU No. 2164289, IPC ЕВВ 43/24, published March 20, 2001, bull. No. 8), including vertical drilling wells in a highly viscous oil reservoir with an opening of the reservoir, vertical wells being fixed with casing strings, perforation of casing strings in the interval of the reservoir, injection of the estimated amount of combined-cycle coolant containing water through the well steam, oil-soluble gas, and non-condensable gas, descent of a pipe string with a pump into a vertical well and the selection of heated products from the well.

The disadvantages of the method:

- firstly, the low coverage of the steam and thermal effects of the reservoir with high viscosity oil. This is due to the fact that heating (shallow penetration of steam from the wellbore deep into the reservoir) of the reservoir is not ensured horizontally, as a result of which the selection of heated oil after steam impregnation of the reservoir is reduced;

- secondly, the low efficiency of the steam-thermal effect on the formation with high-viscosity oil, due to the high consumption of steam and the lack of horizontal hydrodynamic connection across the thickness of the reservoir;

- thirdly, low volumes of selection of preheated highly viscous oil after a steam cycle effect on the reservoir due to inefficient heating of the reservoir;

- fourthly, overheating of the upper part of the reservoir to temperatures that are dangerous for the casing of the well, due to the fact that free oxygen enters into the reaction of liquid-phase oxidation with the reservoir oil with the release of additional heat directly in the reservoir;

- fifthly, high energy costs along the wellbore, due to high heat losses, since steam is pumped through the well, and not through the pipe string, so the bulk of the heat is spent on heating the casing string.

The technical objectives of the invention are to increase the coverage of the reservoir, increase the efficiency of the steam and thermal treatment, increase the selection of heated high-viscosity oil after the steam cycle, prevent overheating of the upper part of the reservoir and reduce heat loss along the wellbore.

The tasks are solved by the method of developing a highly viscous oil deposit by paracyclic action, including drilling a vertical well in a highly viscous oil deposit, attaching a vertical well to a casing string, perforating a casing string in the interval of a productive formation, injecting a vapor-gas coolant through a well into a producing formation, and lowering a pipe string with a pump into the well and selection of heated products from the well.

New is that the perforation in the interval of the reservoir, composed of carbonate rocks, is carried out by a sandblasting perforator with the formation of perforation holes with a diameter of 20 mm, after which proppant foam-acid hydraulic fracturing is carried out with the formation of a fracture gap by injection of gelled fracturing fluid with its subsequent development and fixing in five stages alternating portions of foam acid in equal volumes and foam acid with the addition of a proppant mixture weighing 2 tons in each stage, consisting of roppanta coarse fraction 12/18 mesh proppant and a cylindrical mesh fraction 12/16 percentage ratio of 60/40, and at each subsequent stage the concentration of proppant mixture was raised stepwise from 200 to 600 kg / m ³ with a pitch of 100 kg / m ^3, the concentration acid in the foam is at least 16%, while to reduce heat loss at the beginning of the steam cycle, the well is heated by circulating steam until the condensate leaves the return line, and the pipe string is equipped with a check valve, bottom-up, with a check valve Using a plug-in sucker rod pump, an overflow valve, a packer, place the pipe string in the well so that the packer is opposite the roof of the upper part of the reservoir, then insert the sucker-rod pump into the pipe string on the boom string and fix it in the castle support, and then into the well in for 14 days steam is pumped in a volume of 40 tons / day, after which the well is closed and kept for 14 days for impregnation, then the heated, highly viscous oil is selected, after the flow rate is reduced to a cost-effective value for this wells cycles of steam injection and selection of heated high-viscosity oil are repeated.

In FIG. 1 schematically shows the proposed method in the process of hydraulic fracturing.

In FIG. 2 and 3 schematically depict the proposed method in the process of a steam cycle through a fracture.

The proposed method is implemented as follows.

Drilling and fastening of the vertical well 1 (see Fig. 1) by casing 1 'is carried out. In the well 1, the casing 1 'is perforated in the interval of the reservoir 2, composed of carbonate rocks. Perforation is carried out by a sandblasting punch (not shown) with the formation of perforations 3 (see Fig. 1) with a diameter of 20 mm

The diameter of the perforation holes 3, equal to 20 mm, is necessary for the passage of the proppant of large fractions of 12/18 mesh size. This size of the holes eliminates the premature termination of proppant injection into the fracture due to a sharp pressure jump, i.e. getting "STOP".

After perforation, proppant foam acid fracturing is carried out 2. For this, a production pipe string 4 with a production packer 5 is lowered into the well 1. The production packer 5 is planted above the roof 5 ′ of the productive formation 2, for example, by 5 m. The packer 5 seals the annular space 6 and protects the casing the column 1 'of the well 1 from the effects of high pressures arising during hydraulic fracturing.

Carry out proppant foam acid fracturing 2.

On the technological string of pipes 4 through the perforations 3 into the reservoir 2, a gel-like fracturing fluid is injected to form and direct the fracture of the fracture 7.

The required volume of gelled fracturing fluid (V _cw) prepared at the rate of 1.5 m ³ per 1 m thickness of the producing formation 2. For example, when the thickness of the productive stratum H = 10 m will be equal to V _cw:

The gel-like fracturing fluid is pumped at a flow rate of 0.4 m ³ .

As a gel-like rupture liquid, for example, a cross-linked gel is used, which is prepared by any known method.

Then, fracture gap 7 is developed and fixed in five stages by alternating portions of foam acid in equal volumes and foam acid with the addition of a proppant mixture weighing 2 tons in each stage, consisting of a proppant of a large fraction of 12/18 mesh and a cylindrical proppant of a fraction of 12/16 mesh in a percentage ratio 60/40.

At each subsequent stage, the concentration of the proppant mixture is increased stepwise from 200 to 600 kg / m ³ in increments of 100 kg / m ³ .

To do this, first determine the volume of hydrochloric acid HCl (V _to-you ) for hydraulic fracturing at the rate of 5 m ³ per 1 m of the thickness of the reservoir 2 (determined experimentally):

For example, as indicated above, formation 2 has a thickness of H = 10 m, which means that the required volume of acid is:

V _to-you = 10 m ⋅ 5 m ³ / m = 50 m ³ .

For the effective conduct of foam acid fracturing 2, the concentration of acid in the foam (Spen) should be at least 16%, i.e. Sleep> 16%. It is known that in the foam the concentration of acid decreases, so it is necessary to use acid with a higher concentration. Based on the concentration of acid, determine its concentration in the foam. The mass concentration of HCl in the commercial acid Stov, in Spen foam and the quality of Q foam are related by the ratio:

For example, HCl with a maximum concentration of 35% is available, the quality of the foam (Q) at the bottom of the well is 45 ÷ 50%, we take Q = 47%.

Then, substituting in the formula (3), we calculate the concentration of acid in Spen foam:

47 = (1 - Sleep / 35%) ⋅100,

(1 - Spen / 35%) = 47/100,

Sleep / 35% = (1- (47/100)),

Spen = (1- (47/100)) ⋅35%,

Spen = (1- (47/100)) ⋅35% = 18.55%.

Since the concentration of acid in Spen foam must be at least 16% for the effective implementation of the foam acid fracturing 2, the above condition is fulfilled (18.55%> 16%).

Further, according to the injection plan shown in the table, 50 m ^{3 of} foam acid is prepared. To prepare foam acid at the wellhead, components in the following proportions are poured into a container (not shown):

35% concentrated HCl 98.8% - 49.4 m ³ Foaming agent Neftonol VVD 1% - 0.5 m ³ reagent FA-1 0.2% - 0.1 m ³

Then, a pump unit, for example, CA-320, feeds a mixture of components from the tank into the pipe process string 4 and simultaneously starts the compressor (not shown in Fig. 1), which through a tee (not shown in Fig. 1), also pumps nitrogen gas into the process pipe string 4 to form a foam acid. The fracture 7 (see Fig. 1) is developed and fixed (proppant wedging) in five stages, and at each subsequent stage, the proppant mixture concentration is increased stepwise from 200 to 600 kg / m ³ in increments of 100 kg / m ³ . Gaseous nitrogen is supplied with a flow rate of 60 m ³ / min at each stage.

First stage:

- for the development of a fracture gap 7 injected foam acid 8 'in a volume of 4 m ³ with a flow rate of 0.3 m ³ / min;

- for fastening discontinuity cracks 7 pumped penokislotu 8 'in a volume of 10 m ³ at a flow rate of 0.3 m ³ / min with a mixture of proppants 9' at a concentration of 200 kg / m ^3, wherein the proppant is 12/18 mesh coarse fraction - 1200 kg and cylindrical proppant fraction 12/16 mesh - 800 kg (total 2000 kg).

Second stage:

- for the development of a fracture gap 7 injected foam acid 8 '' in a volume of 4 m ³ with a flow rate of 0.3 m ³ / min;

- to fix the fracture gap 7, 8 '' foam acid is injected in a volume of 6.7 m ³ with a flow rate of 0.3 m ³ / min with a 9 '' proppant mixture at a concentration of 300 kg / m ³ , while the large fraction proppant is 12/18 mesh - 1200 kg and a cylindrical proppant fraction of 12/16 mesh - 800 kg (total 2000 kg).

Third stage:

- for the development of a fracture gap 7 injected foam acid 8 "in a volume of 4 m ³ with a flow rate of 0.3 m ³ / min;

- to fix the fracture gap 7, 8 '''foam acid is injected in a volume of 5 m ³ with a flow rate of 0.3 m ³ / min with a 9''proppant mixture at a concentration of 400 kg / m ³ , while the proppant is a large fraction of 12/18 mesh - 1200 kg and a cylindrical proppant fraction of 12/16 mesh -800 kg (total 2000 kg).

Fourth stage:

- for the development of a fracture gap 7 injected foam acid 8 '''' in a volume of 4 m ³ with a flow rate of 0.3 m ³ / min;

- to fix the fracture gap 7, 8 "8" foam acid is injected in a volume of 4 m ³ with a flow rate of 0.3 m ³ / min with a mixture of 9 '' ”proppants in a concentration of 500 kg / m ³ , while the proppant is a large fraction of 12 / 18 mesh - 1200 kg and cylindrical proppant fraction 12/16 mesh - 800 kg (total 2000 kg).

Fifth stage:

- for the development of a fracture gap 7, the foam acid 8 ″ ″ ″ is injected in a volume of 4 m ³ with a flow rate of 0.3 m ³ / min;

- to fix the fracture gap 7, the foam acid 8 '''''is injected in a volume of 3.3 m ³ with a flow rate of 0.3 m ³ / min with a mixture of proppants 9''''' at a concentration of 600 kg / m ³ , while the proppant coarse fraction 12/18 mesh - 1200 kg and a cylindrical proppant fraction 12/16 mesh - 800 kg (total 2000 kg).

At the end of the fifth stage, the foam acid and the proppant mixture 9 ’’ ’are pumped with technical water, for example, with a density of 1100 kg / m ³ in a volume equal to the volume of the process pipe string 4, for example, V _Tr = 5 m ³ with a flow rate of 0.5 ³ m / min into the fracture gap 10, formed as a result of stepwise and fixing the initial fracture gap 7.

The sequence of the foam acid fracturing is tabulated.

At the end of the hydraulic fracturing, the well 1 is closed and technological exposure is carried out for 30 minutes, after which the pressure is released from the well 1. The process packer 5 is unpacked, i.e. the annular space 6 of the well 1 is depressurized and the process string of pipes 4 with the packer 5 is removed from the well 1. The hydraulic fracturing process is completed.

The essence of the foam acid fracturing is that it does not use ordinary acid, but an aerated surfactant solution in HCl in the form of foam, which develops a fracture fracture in the formation during hydraulic fracturing, which facilitates the penetration of HC1 together with the foam into the unreacted state deep into the formation, which increases the coverage of the reservoir by steam with further steam and thermal exposure.

By 2–3 times in comparison with the prototype, the coverage of the productive carbonate formation with high viscosity oil with the steam-thermal effect increases, since the use of foam acid for hydraulic fracturing slows down the dissolution of carbonate material in acid, which contributes to a deeper penetration of the active acid into the formation. As a result of this, sections of the productive formation 2 remote from the well 1, previously insufficiently or completely not covered by the filtration process, are attached to the drainage. In addition, the low density of hydrochloric acid foam (400-800 kg / m ³ ) and its increased viscosity make it possible to significantly increase coverage by the effect of acid on the crack while it is developing and wedging.

Cylindrical proppant in the fracture fracture 10 increases the porosity of the proppant mixture, which improves the permeability and the degree of purification from the decomposition products of the fracture fluid, and the presence of a dispersed gas phase with a large specific surface in the foam facilitates the effective removal of solid muds from the bottomhole formation zone, which further creates conditions deeper penetration of steam into the formation by forming a horizontal hydrodynamic connection across the thickness of the reservoir, which increases the efficiency of steam and heat impact as a whole.

The efficiency of the steam-thermal effect on the formation 2 is increased due to the creation of a highly conductive fracture gap 10, fixed with a proppant mixture, thereby reducing the consumption of steam spent on heating the reservoir.

To reduce heat loss at the beginning of the cyclic effect, a pipe string (not shown) is lowered into the well 1 to the perforation holes 3, through which steam is injected. The well 1 is heated by circulating steam through a pipe string with an exit through the annular space (not shown), tied to a return line with a groove capacity (1-3 not shown) until the condensate leaves the return line (visually observed) into the groove capacity. The pipe string is removed.

Then, by the forces of the underground repair shop for oil and gas production control, a pipe string 11 is lowered into the well 1 (see FIG. 2), equipped with a bottom-up check valve 12, a lock support 13, an overflow valve 14, a packer 15. The pipe string 11 is placed in the well 1 so that the packer 15 was opposite the roof of the reservoir 2. Into the string of pipes 11 on the string of rods 16 the plug-in sucker rod pump 17 is lowered, it is fixed in the castle support 13.

Next, into the reservoir 2 along the pipe string 11 through the bypass valve 14, the under-packer space 18 and the perforated holes 3, with the check valve 12 closed, steam is injected for 14 days at a temperature of 235-239 ° C in a volume of 40 t / day, for example, injection steam is conducted under pressure P _n = 3.1-3.3 MPa, i.e. opening pressure of the bypass valves 14 R _p = 3.1 MPa.

After steam injection, well 1 is closed and soaked for 14 days for impregnation. In the process of impregnation, the process of heat and mass transfer, the capillary flow of oil, starts, the viscosity of the oil decreases.

Steam injection allows warming up formation 2, improving the quality of the HCl reaction with the carbonate formation rock and the conditions for cleaning the bottom-hole zone of the formation from reaction products: the presence of a surfactant reduces the surface tension of both active and reacted acid at the interface with oil, and the presence of compressed gas in the reacted solution expanding many times during well development (with a decrease in bottomhole pressure), creates the conditions for increasing the selection of heated high-viscosity oil after a steam cycle.

Due to the horizontal hydrodynamic connection between the rocks of the reservoir 2 by means of a fracture fracture 10, overheating of the upper part of the reservoir 2 to temperatures hazardous to the casing 1 'of the well 1 is excluded.

Energy costs are reduced for casing 1 'of well 1, since heat losses are reduced, since steam is pumped through pipe string 9 isolated from casing 1' of well 1 by packer 15, so heat losses at the casing are minimal (only in perforation intervals).

Before the descent rod pump 17 is lowered into the pipe string 11, the pressure of the hydrostatic column of liquid in the pipe string 11 is determined, which is formed due to steam condensation, created on the bypass valve 14:

where P _article - the pressure of the hydrostatic column of liquid on the bypass valve 14, MPa;

ρ is the density of the liquid, kg / m ³ . Take ρ = 950 kg / m ³ ;

N is the height of the hydrostatic column of liquid from the mouth to the bypass valve 14, m. Take H = 285 m.

Substituting the numerical values in the formula 4, we get:

P _st = 950 kg / m ³ ⋅ 9.8 m / s ² ⋅ 285 m = 2.65 MPa.

In order for the bypass valve 14 to not open when the high-viscosity oil is selected by the plug-in sucker-rod pump 17, the following conditions must be met:

Substituting the numerical values in condition (5), we obtain:

3.1 MPa> 2.65 MPa.

Condition (5) is satisfied. Thus, the pressure of the hydrostatic column of liquid in the pipe string 11 does not exceed the vapor injection pressure, which allows the selection of heated high-viscosity oil and eliminates the backflow of high-viscosity oil from the pipe string 11.

At the end of the well treatment, after 14 days it is opened. After that, the plug-in sucker rod pump 17 (see Fig. 3) is launched into operation, which selects high viscosity oil through the pipe string 11 at the wellhead 1 through the perforation holes 3 and the open check valve 12. Thus, the well 1 is operated to a cost-effective value high viscosity oil production.

The selection of heated oil is continued until the well production rate decreases to a cost-effective amount. Profitability is a relative indicator of the economic efficiency of a well. With a decrease in flow rate below a cost-effective value, well operation becomes unprofitable, for example, below 1 m ³ / day.

After the formation is heated by steam, the flow rate of well 1, for example, is 20 m ³ / day; as the heated oil is taken, the formation cools and the flow rate decreases, for example, to 0.8 m ³ / day, i.e. the flow rate drops below a cost-effective amount.

Then repeat the injection of steam through the pipe string 11 (see Fig. 3). Next, as described above, the cyclic effect on the well 1 is repeated.

The proposed method for the development of a highly viscous oil deposit with a steam cycle allows:

- increase the coverage of the reservoir;

- to increase the efficiency of steam and thermal effects on the reservoir;

- increase the selection of preheated highly viscous oil after a steam cycle;

- eliminate overheating of the upper part of the reservoir;

- reduce heat loss along the wellbore.

Claims (1)

A method for developing a high-viscosity oil reservoir by paracyclic treatment, including drilling a vertical well in a high-viscosity oil reservoir, attaching a vertical well to a casing string, perforating a casing string in the interval of a productive formation, injecting a vapor-gas coolant through a well into a producing formation, lowering a pipe string with a pump into the well and selecting products from the well, characterized in that the perforation in the interval of the reservoir, composed of carbonate rocks, produce sandblast with a perforating gun with the formation of perforation holes with a diameter of 20 mm, followed by proppant foam acid fracturing with formation of a fracture fracture by injection of gelled fracturing fluid with its subsequent development and fixing in five stages with alternating portions of foam acid in equal volumes and foam acid with the addition of a proppant mixture weighing 2 tons in each stage, consisting of a proppant of a coarse fraction of 12/18 mesh and a cylindrical proppant of a fraction of 12/16 mesh in a percentage of 60/40, with each pos In the next stage, the proppant mixture concentration is increased stepwise from 200 to 600 kg / m ³ in increments of 100 kg / m ³ , the acid concentration in the foam being at least 16%, and to reduce heat loss at the beginning of the steam cycle, the well is heated by steam circulation until condensate outlet from the return line, and a pipe string is lowered into the well, equipped with a check valve from bottom to top, a lock support of the plug-in sucker rod pump, a bypass valve, a packer, the pipe string is placed in the well so that the packer is opposite the roof of the upper part of the reservoir, then an insert rod pump is lowered into the pipe string on the rod string and fixed in the castle support, after which the well is injected with steam in a volume of 40 t / day for 14 days, after which the well is closed and kept for 14 day for impregnation, then the heated high-viscosity oil is selected, after the flow rate is reduced to a cost-effective value for a given well, the steam injection and selection of the heated high-viscosity oil are repeated.

Images