RU2595114C1 - Method for development of carbonate reservoir with horizontal wells - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method for development of carbonate reservoir with horizontal wells involves drilling of horizontal wells, lowering pumps on pipe string to horizontal part of holes, acid treatment of reservoir through filters with different density of perforation, withdrawal of well production. At that, into horizontal hole, which is made open, two pipe strings of 1.5-2 inch diameter are lowered, wherein central borehole pump is installed into one of them, and serially connected filters are installed in another along whole length of string; perforation density N_n of each n-th filter section is performed according to ratio: N_n = N_min·k_max/k_n, where k_max - maximum reservoir permeability along horizontal hole, k_n - permeability of n-th collector section, N_min - density of perforation holes in filter section opposite reservoir with maximum permeability. Into annular space, up to mouth, service water is pumped, hereafter acid is supplied into pipe string with filters, the flushed by process water in volume not less than volume of pipe string, through which acid was injected. After reaction of acid with rock, via same string, reaction products are extracted until oil appears, then pump is set into operation in horizontal shaft. If oil flow rate drops by more than 50 % of oil flow rate after acid treatment, process of acid treatment is repeated, wherein volume of service water for pressing of acid is selected at least 2 volumes of service water compared to used in previous treatment cycle.

EFFECT: increasing oil recovery of inhomogeneous carbonate reservoir.

1 cl, 1 dwg

Description

The method of developing a carbonate reservoir horizontal wells

The invention relates to the oil industry and may find application in the development of heterogeneous carbonate reservoirs by horizontal wells.

There is a method of developing an oil reservoir by horizontal wells, including drilling or selecting already drilled horizontal wells, identifying sections in the form of intervals of the reservoir, lowering the pump into the well, separating the sections with packers, selecting well products from each section. When developing a terrigenous or carbonate formation, the inflow profile is preliminarily determined, areas with an inflow profile different from each other by specific oil production rate of 20% or more are identified, packers are installed in the places where the specific oil production rate changes, a pumping unit is lowered into the center of each section compressor or coiled tubing sleeveless pipes one pump, the distance between the pumps along the horizontal shaft is set to not more than 200 m (RF patent No. 2544204, class Е21В43 / 16, publ. 03/10/2015).

The closest in technical essence to the proposed method is a method of large-volume acid treatment of a carbonate formation, including research and determination of zones of the formation with different permeability, descent into a horizontal well on a string of tubing filters with different perforation densities, pumping acid into an open horizontal well bore selling acid, flushing the well and putting it into operation. Each section with a permeability differing by more than 20% from the neighboring one is isolated by packers installed on the filters, and the filter perforation density of each section is performed based on the ratio

$$\frac{h_1\cdot k_1}{Ln\frac{R_1}{r_c}+{С}_1}=\frac{h_2\cdot k_2}{Ln\frac{R_2}{r_c}+{С}_2}=\mathrm{...}=\frac{h_n\cdot k_n}{Ln\frac{R_n}{r_c}+{С}_n}$$

, $$$$

$$\frac{h_{\mathrm{one}}\cdot k_{\mathrm{one}}}{Ln\frac{R_{\mathrm{one}}}{r_c}+{\mathrm{FROM}}_{\mathrm{one}}}=\frac{{\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="00000004.png"\; state="\{\{state\}\}">h</figure-callout>}}_2\cdot k_2}{Ln\frac{R_2}{r_c}+{\mathrm{<figure-callout\; id="2"\; label="FROM"\; filenames="00000004.png"\; state="\{\{state\}\}">FROM</figure-callout>}}_2}=\mathrm{...}=\frac{h_n\cdot k_n}{Ln\frac{R_n}{r_c}+{\mathrm{FROM}}_n}$$

,

where C ₁ , C ₂ , C _n are the hydrodynamic perfection coefficients of the well according to the nature of opening along the horizontal wellbore;

R ₁ , R ₂ , R _n - the projected depth of acid penetration into the rock, m,
k ₁ , k ₂ , k _n - the permeability of the reservoir, m ² ,

h _n - the thickness of the reservoir, m,

r _c is the radius of the filter, m,

Alkali is pumped into the annulus to the top of the reservoir to neutralize acid or a packer is installed at the top of the reservoir, while the annulus is filled with technical water, the volume V of alkali or water is determined by the formula

V = π · H · (R ² -r ² ), m ³ ,

where H is the depth of the well to the top of the reservoir, m,

R is the inner radius of the production casing, m,

r - the outer radius of the tubing string, m,

hydrochloric acid with a concentration of 10-20% is pumped into tubing at a wellhead pressure P _y = (0.009 ... 0.01) · H, MPa, in a volume of V _k equal to

V _to = (0.007 ... 0.008) · L · h, m ³ ,

where L is the length of the horizontal wellbore, m,

h is the thickness of the reservoir, m,

the acid is pumped into the formation by oil in an amount equal to the volume of the internal space of the tubing with filters (RF patent 2533393, class E21B43 / 27, publ. 11/20/2014 - prototype).

A common disadvantage of the known methods is the low efficiency of developing heterogeneous carbonate reservoirs for each of the methods separately, which leads to low oil recovery.

In the proposed invention solves the problem of increasing oil recovery carbonate reservoir.

The problem is solved in that in a method for developing a carbonate reservoir by horizontal wells, including drilling horizontal wells, lowering a pipe string into the horizontal part of the pump trunks, acidizing the reservoir through filters with different perforation densities, selecting a well production according to the invention to a horizontal wellbore, which open, lower two columns of pipes with a diameter of 1.5-2 inches, on one of which a pump is installed in the center of the barrel, on the other along the entire length of the barrel edovatelno connected filters perforation density _{N n} of each n-th filter section operate according to the relation

N _n = N _min · k _max / k _n ,

where k _max is the maximum permeability of the reservoir along the horizontal trunk,

k _n - permeability of the n-th section of the reservoir,

N _min - the density of the perforation holes of the filter section opposite the collector with maximum permeability,

Technical water is pumped into the annulus to the mouth, after which, when the pump is stopped, acid is supplied to the pipe string with filters, pressed with process water in an amount not less than the volume of the pipe string through which acid is pumped, after the reaction of the acid with the rock, products are taken from the pipe reactions before the appearance of oil, then the pump is put into operation in a horizontal well, when the oil production rate drops by more than 50% of the oil production rate after acid treatment, the acid injection process is repeated, and the volume of process water for the sale of acid, at least 2 volumes of industrial water, which was used in the previous treatment cycle, are selected from the condition.

SUMMARY OF THE INVENTION

The oil recovery of the carbonate reservoir, developed by horizontal wells, is significantly affected by the uniformity and the degree of development of oil reserves. Existing technical solutions do not fully allow to perform this task. In the proposed invention solves the problem of increasing oil recovery carbonate reservoir. The problem is solved as follows.

In FIG. 1 is a schematic illustration of a section of an oil reservoir with a horizontal wellbore. Designations: 1 - oil reservoir, 2 - horizontal production well, 3 - horizontal wellbore, 4 - roof of the productive reservoir, 5 - casing string, 6 - pipe string with pump 7, 7 - pump, 8 - pipe string with filters 9-11 , 9-11 - filters with different density of perforation, 12 - annular space.

The method is implemented as follows.

The section of the oil reservoir, the reservoir 1 (Fig. 1) of which is represented by the carbonate type and the purely oil zone, is opened with a horizontal well 2 with a horizontal wellbore 3. The reservoir 1 is zonal heterogeneous, for example, three sections distinguished by their permeability are distinguished: I, II and III . To the roof 4 of the reservoir, the well is cased with casing 5, and the horizontal shaft 3 is open.

Two columns of pipes with a diameter of 1.5-2 inches each are lowered into a horizontal wellbore 3 wells. On one of the pipe columns 6, a pump 7 is installed (for example, type 2SP45 / 24) and placed in the center of the horizontal barrel 3. On another pipe pipe 8 along the entire length of the barrel are placed series-connected filters 9-11. The perforation density N _{n of} each n-th filter section 9-11 is performed in proportion to the ratio of the maximum and calculated permeabilities of sections I, II and III according to the formula:

N _n = N _min · k _max / k _n , (1)

where k _max is the maximum permeability of the reservoir along the horizontal trunk,

k _n - permeability of the n-th section of the reservoir,

N _min - the density of the perforation holes of the filter section 9-11 opposite the collector with maximum permeability,

Technical water is pumped into the annulus 12 to the mouth, after which, when the pump 7 is stopped, acid is supplied to the pipe string 8 with filters 9-11. Water in the annulus 12 does not allow acid to act on the casing 5. The acid is pressed with process water in an amount not less than the volume of the pipe string 8, through which the acid is pumped. After the reaction of the acid with the rock, reaction products are taken through the same pipe 8 until oil appears.

According to calculations, the diameter of pipes 6 and 8 of more than 2 inches does not allow unimpeded parallel descent of two pipes with equipment into the most common casing diameters 5. The diameter of pipes 6 and 8 of less than 1.5 inches leads to low flow rates and flow rates. The pump 7 in the central part of the horizontal wellbore 3 allows, according to research, to most effectively select oil reserves along the entire horizontal wellbore 3. The density of the perforation holes of the filters 9-11, depending on the permeability of the reservoir, allows the injection of acid evenly into the formation along the entire horizontal wellbore 3 of the well 2 .

After selection of the reaction products, the pipe string 8 with filters 9-11 is stopped, and pump 7 is put into operation on another pipe string 6 located in the horizontal barrel 3. When the oil production rate drops by more than 50% of the oil production rate after acid treatment, the injection process acids repeat. The volume of process water for selling acid is defined as at least 2 volumes of process water used in the previous treatment cycle.

According to calculations, such a periodic cycle of work: acid injection - product extraction - acid injection - product extraction, etc., allows you to select the largest amount of reserves due to acid treatment with each cycle of more and more distant collector zones 1, and the variable density of the perforation of the filters is 9- 11 and the pump 7 in the Central part of the barrel allow you to select stocks most evenly. If the flow rate drops by less than 50%, repeated acid treatment is not economically feasible. Selling process water with increasing volumes allows acid to penetrate deeper into the reservoir. Moreover, according to calculations, the volume of less than 2 volumes of industrial water used for sales in the previous cycle does not allow to increase oil recovery.

Similar operations are carried out on other horizontal wells of the reservoir. Development is carried out until the complete economically viable development of the reservoir.

The result of the implementation of this method is to increase the oil recovery of the carbonate reservoir.

An example of a specific implementation of the method

The section of the oil reservoir, the reservoir 1 (Fig. 1) of which is represented by the carbonate type and a purely oil zone of 10 m thick, lying at a depth of 850 m, is opened with a horizontal well 2 with a horizontal well 3 of 300 m length. The reservoir 1 is zonal heterogeneous, three sections I are distinguished , II and III with the corresponding permeabilities k _I = 50 mD, k _II = 30 mD and k _III = 100 mD. To the roof 4 of the reservoir, the well is cased with casing 5 with a diameter of 168 mm, and the horizontal shaft 3 is open.

Two columns of pipes are lowered into the horizontal shaft 3 of well 2: one 6 with a diameter of 1.5 inches, the other 8 with a diameter of 2 inches. On the pipe string 6, a pump 7 of the 2SP45 / 24 brand is installed and placed in the center of the horizontal barrel 3. On the pipe string 8 along the entire length of the barrel are placed series-connected filters 9-11.

Conversely portion III with a maximum permeability of filters 11 mounted with minimum perforation density N _min = N _III = 6 holes. / M. Then the perforation density N _I and N _{II of the} filters 9 and 10, respectively, are calculated and performed according to the formula (1):

N _I = N _III · k _III / k _I = 6 · 100/50 = 12 holes / m,

N _II = N _III · k _III / k _II = 6 · 100/30 = 20 holes / m.

The annular space 12 to the mouth of the process water is pumped in a volume of 17 m ^3, whereupon the pump 7 is stopped when fed 24% hydrochloric acid to the pipe column 8. The acid process water is forced in a volume of 1.8 m ^3, equal to the volume of the pipe string 8 After the reaction of the acid with the rock, reaction products are taken through the same pipe 8 until oil appears.

Next, the pipe string 8 is stopped, while the pump 7 is put into operation on the pipe string 6. The oil production rate after acid treatment was 12 tons / day. After 1 year of operation, the oil production rate decreased by 50% of the oil production rate after acid treatment, i.e. up to 6 t / day. The acid injection process is repeated as described above. The acid is sold with industrial water in a volume exceeding 2 times the volume of industrial water that was used in the previous treatment cycle, i.e. 3.6 m ³ . After the second acid treatment, the oil production rate was 10 tons / day. Acid injection cycles are repeated five times.

Similar operations are carried out on other horizontal wells of the reservoir. Development is carried out until the complete economically viable development of the reservoir.

As a result of the development of section 1, which was limited by watering the production well to 98%, 174.3 thousand tons of oil were produced from one horizontal well, the oil recovery factor (CIN) of the section was 0.395 units. According to the prototype, ceteris paribus, it was produced 146.5 thousand tons of oil, oil recovery factor amounted to 0.332 units The increase in recovery factor by the proposed method is 0,063 units

The proposed method allows to increase the oil recovery factor of a zonal heterogeneous carbonate reservoir due to a more uniform and deep periodic acid treatment and efficient production of products along the entire horizontal wellbore.

The application of the proposed method will solve the problem of increasing oil recovery carbonate reservoir.

Claims (1)

A method for developing a carbonate reservoir by horizontal wells, including drilling horizontal wells, running on a pipe string into the horizontal part of the pump shafts, acidizing the reservoir through filters with different perforation densities, selecting well products, characterized in that they are lowered into the horizontal wellbore that is open two columns of pipes with a diameter of 1.5-2 inches, on one of which a pump is installed in the center of the barrel, on the other along the entire length of the barrel are placed series-connected ltry, perforation density _{N n} of each n-th filter section operate according to the relation:
N _n = N _min ∙ k _max / k _n ,
where k _max is the maximum permeability of the reservoir along the horizontal trunk,
k _n - n-th permeability reservoir area,
N _min - the density of the perforation holes of the filter section opposite the collector with maximum permeability,
Technical water is pumped into the annulus to the mouth, after which, when the pump is stopped, acid is supplied to the pipe string with filters, pressed with process water in an amount not less than the volume of the pipe string through which acid is pumped, after the reaction of the acid with the rock, products are taken from the pipe reactions before the appearance of oil, then the pump is put into operation in a horizontal well, when the oil production rate drops by more than 50% of the oil production rate after acid treatment, the acid injection process is repeated, and the volume of process water for the sale of acid, at least 2 volumes of industrial water, which was used in the previous treatment cycle, are selected from the condition.

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