RU2515651C1 - Method for multiple hydraulic fracturing of formation in horizontal shaft of well - Google Patents

Abstract

FIELD: oil and gas industry.SUBSTANCE: method includes identification of natural fracturing of rocks and its maximum primary stress, isolation of the burst interval in a horizontal well bore, performance of hydraulic fracturing in the isolated interval, fixing of the fracturing. A horizontal well with a bore length equal to at least 200 m is either selected or drilled in the direction being the bisector of the least angle between the vector of natural fracturing and the vector of the maximum primary stress. When length Ln of each interval is exceeded along the well borehole per more than 50 m, at this section N=Ln/100 steps of hydraulic fracturing is performed where N is rounded off to an integer number. Initially hydraulic fracturing step is made within the interval with the lowest permeability, the breaking fluid is injected at the flow rate of 1-3 m/min and crosslinked gel and linear gel is used in the ratio of 2:1 respectively, flushing of fluid with a proppant is made by the process fluid with density equal to the density of stratal water in this stratum. At that fractures in each interval are fixed by fractions of the proppant which are selected on the condition that equality is ensured for processing duration of the stratum intervals with different permeability as per the theoretical dependency.EFFECT: improving efficiency of hydraulic fracturing for zonal and non-uniform reservoirs.2 dwg

Description

The invention relates to the oil industry and may find application in conducting multiple hydraulic fracturing (hydraulic fracturing) in zoned heterogeneous carbonate and terrigenous formations.

A known method of multiple hydraulic fracturing of a horizontal wellbore, including the formation of cracks successively at different intervals of the reservoir, opened by a horizontal wellbore, by installing a packer, supplying hydraulic fracturing fluid through a filter installed in each of the intervals of the horizontal wellbore with isolation of the remaining parts of it parts. The packer is installed in a vertical wellbore, initially hydraulic fracturing is carried out in the interval of the formation with the highest permeability by supplying a proppant-bearing fluid with the installation of a “head” of a proppant plug that overlaps the corresponding section of the horizontal wellbore between the filters, with the specified insulation by forming a polymer crust on the corresponding filters , repeat the specified operation at each of the remaining intervals sequentially according to the degree of decrease in their permeability with preliminary impact pouring a crust from a filter corresponding to this interval, moreover, a polymer crust is formed by supplying a biopolymer composition to the well, and its removal is carried out with a solvent liquid containing a gel breaker of 0.6-1.2 kg / m ^{3 of} water (RF patent No. 2362010, cl. ЕВВ 43/267, published on July 20, 2009).

The disadvantage of this method is that in the development of oil deposits by horizontal wells with multiple hydraulic fracturing, zonal heterogeneity is not taken into account, which leads to low oil recovery.

Closest to the proposed invention in technical essence is a method of multiple hydraulic fracturing in a horizontal wellbore, including lowering the packer into the well on a pipe string, followed by its landing in the well, the formation of cracks opposite the filters sequentially at different intervals of the reservoir, opened by a horizontal wellbore hydraulic fracturing fluid through a filter installed in each of the parts of the horizontal wellbore corresponding to each of these intervals olation of the rest of its parts. The direction of the horizontal trunk relative to the direction of the minimum main stress is determined, then the interval subject to hydraulic fracturing (Fracturing) from the remaining sections of the horizontal trunk by isolating the twin packers is isolated, then the valve located inside the pipe string between the twin packers opposite the filter is opened if the direction of the horizontal trunk is parallel to the direction minimum main stress, the hydraulic fracturing is carried out by injection of a fracturing fluid with the formation iem transverse cracks a relatively horizontal wellbore, followed by fastening the transverse cracks by pumping fluid with proppant aluminosilicate, with a gradual increase of its fraction of 20/40 mesh. up to 16/30 mesh., if the direction of the horizontal wellbore is perpendicular to the direction of the minimum principal stress, then hydraulic fracturing is carried out by pumping a fracturing fluid with the formation of horizontal cracks relative to the horizontal wellbore, followed by horizontal cracking by pumping the fluid with lightweight proppant with a 20/40 mesh fraction. , at the end of the hydraulic fracturing, the well is closed for a technological pause for 0.5 h, after which, at the wellhead, an adjustable fitting is installed on the pipe string and producing spilling the spent proppant fluid from the formation along the pipe string at the wellhead until the valve is closed, while during the spout by adjusting the fitting, the pressure in the pipe string is 2-3 MPa less than the pressure when opening the well after a technological break, and then unpack packer and move the pipe string to another part of the horizontal wellbore, and the above hydraulic fracturing process in the horizontal wellbore is repeated depending on the number of horizontal wellbore intervals, equipped with filters in its various parts (RF patent No. 2472926, cl. ЕВВ 43/267, publ. 01/20/2013 - prototype).

The disadvantage of this method is the low efficiency of hydraulic fracturing, which is manifested in the low oil recovery of a reservoir with a zone-heterogeneous reservoir developed after hydraulic fracturing.

In the proposed invention solves the problem of increasing the efficiency of fracking, expressed in increasing oil recovery deposits with a zonal heterogeneous reservoir.

The problem is solved in that in the method of multiple hydraulic fracturing in a horizontal wellbore, including determining the direction of natural fracture of the rock and its maximum principal stress, in the horizontal wellbore isolating the fracture interval, conducting hydraulic fracturing in an isolated interval, fixing the fracture according to the invention, a horizontal well with a length of the horizontal part of at least 200 m, choose, or drill in the direction that is the bisector of a smaller angle between the eyelids Hur natural fractures and the vector maximum principal rock stress, exceeding the length L _n of each interval along the borehole more than 50 m it is carried N = L _n / 100 steps fracturing, where N is rounded up to an integer number initially fracturing step is performed in the interval with the lowest permeability fracturing fluid is pumped at a rate of 3.1 m ³ / min, which is used as a crosslinked gel in series and a linear gel in the ratio 2: 1 respectively and with a fluid with proppant prodavku osuschest lyayut process fluid with a density equal to the density of the formation water reservoir, wherein the crack multiple fracturing at each of the intervals is attached proppant such fractions which are selected from the condition of equality of duration of individual production intervals of the formation with a permeability varying by the formula:

, $$\frac{k_{\mathrm{one}}}{Ln\frac{r_k}{r_c}+S_{\mathrm{one}}}=\frac{k_2}{Ln\frac{r_k}{r_c}+{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="00000018.png"\; state="\{\{state\}\}">S</figure-callout>}}_2}=...=\frac{k_n}{Ln\frac{r_k}{r_c}+S_n}$$

,

where k _n - the permeability of the reservoir of the n-th interval, m ² ,

r _c - well radius, m,

Sn is the skin factor of the nth interval of the bottomhole formation zone, fractions of units,

r _k is the radius of the power circuit, m

SUMMARY OF THE INVENTION

The oil recovery of a zonal heterogeneous oil field is significantly affected by the time the wells run until they are completely flooded and the oil reserves are evenly depleted. Existing technical solutions do not fully allow to perform this task. The proposed invention solves the problem of increasing oil recovery of a zone-heterogeneous oil reservoir by means of as long as possible well operation until complete flooding, equalization of production rates and uniform production of oil reserves. The problem is solved as follows.

Figure 1 shows the plan layout of a horizontal well with multiple hydraulic fracturing. Accepted designations: HW is a horizontal well, S _tr is the direction of natural fracturing, S _fracturing is the direction of multiple fracturing fractures, δ _max is the direction of the maximum main stress of the rocks, δ _min is the direction of the minimum main stress of the rocks.

Figure 2 presents a diagram of a section of a reservoir with a horizontal well and multiple hydraulic fracturing. Accepted designations: 1 - productive formation, 2 - horizontal well, 3-6 - reservoir intervals with different permeabilities, 3'-6 '- hydraulic fractures, 7 - non-reservoir, 8 - liner, 9 - filters, 10 - water swellable packers, 11 - tubing, 12 - twin packers, 13 - radial holes of the hydraulic valve, 14 - hydraulic valve, 15 - piston and spring mechanism.

The method is implemented as follows.

In the area of reservoir 1 (Fig. 1), the reservoir of which is represented by zonal heterogeneous carbonate or terrigenous deposits, determine the direction of the minimum main stress of the rock δ _min and, accordingly, perpendicular to it the direction of the maximum main stress of the rock δ _max . One of the methods of determination is the conduct of geophysical surveys (GIS), using the method of wave acoustic logging (for example, using the VAK-8 device) in neighboring wells. 3D seismic studies are also carried out and the preferred direction of natural cracks S _{tr is} determined.

A horizontal well (HW) HW with a horizontal part of the wellbore of at least 200 m is selected for multiple hydraulic fracturing, or drilled in a direction that is a bisector of a smaller angle between the natural fracture vector S _tr and the maximum principal rock stress vector δ _max . From the experience of conducting multiple hydraulic fracturing, it is known that cracks form perpendicular to the direction of the minimum principal rock stress δ _min , i.e. parallel to the direction of the maximum principal stress of the rocks δ _max . Calculations of multiple hydraulic fracturing showed that for different geological and physical characteristics of the reservoir, when the horizontal wellbore is positioned in this way, i.e. between a smaller angle of direction of natural cracks and cracks resulting from multiple hydraulic fracturing, the duration of the operation of the wells to complete flooding increases, because water through cracks goes the maximum way. Also, according to calculations, when the horizontal trunk length is less than 200 m, the efficiency of multiple hydraulic fracturing is reduced, because the effect of interference of cracks begins to be present, which leads to the need for conventional hydraulic fracturing instead of multiple.

In a productive zone-heterogeneous formation 1 (Fig. 2), according to the above conditions, a horizontal well 2 is drilled. Next, a well logging is carried out in an open wellbore, the results of which determine the reservoir and non-reservoir sections, their permeability and saturation.

For example, as a result of the studies, we obtained 4 intervals (3, 4, 5, 6) of the productive part of reservoir 1 along well 2. Between intervals 3 and 4, 4 and 5 there are sections of non-reservoir 7. As a result of the interpretation of the well logs, it was also established that the average the permeability of the intervals 3, 4, 5, 6, respectively, k ₃ , k ₄ , k ₅ , k ₆ . It is also possible to determine permeability on a selected core; in this case, when drilling a horizontal well, it is necessary to lay a core sampler in the design of the drill string.

If the length L _{n of} each interval along the wellbore is exceeded more than 50 m, N = L _n / 100 fracturing stages are performed on it, where N is rounded to the nearest whole number. So, for example, if the interval length is 250 m, then it is necessary to carry out N = 250 / 100≈3 stages of multiple hydraulic fracturing on it.

Based on these data, a shank 8 with filters 9 located in oil-saturated intervals 3, 4, 5, 6 of formation 1 is constructed and lowered into an uncased horizontal shaft. Shank 8 is also equipped with water-swelling packers 10 (for example, TAM) on the intervals of the trunk, which did not open the collector 7, as well as in places where the permeability of the collector is different (decreases or increases). Also, when several stages of hydraulic fracturing are carried out at one of the intervals, they are also separated by water-swellable packers.

Then proceed with hydraulic fracturing in each of the intervals, starting from where the minimum permeability of the reservoir, because it is necessary to select for such a section a proppant with a fraction that provides the necessary maximum permeability of the crack, compared with intervals with a higher permeability of the reservoir. As a result of multiple hydraulic fracturing, cracks 3 ', 4', 5 ', 6' are obtained.

Consider the stage of multiple hydraulic fracturing at one of the intervals, for example, the 5th. For the remaining intervals, the hydraulic fracturing process is similar.

To the interval 5 of the formation, dual packers 12 are lowered on the tubing string 11, which are placed before and after the radial holes 13, the hydraulic valve 14 and the filter 9. The packers must provide a tight cut-off of the horizontal borehole interval 2 with the filter 9.

Together with the radial holes 13, a hydraulic valve 14 is located, which, when the fluid is injected into the tubing from the wellhead, moves forward and backward along the tubing axis 11 by means of the piston and spring mechanism 15 with increasing and decreasing injection pressure. In this case, the radial holes 13 open at an injection pressure of more than a certain value. At lower injection pressures, the hydraulic valve 14 provides a tight seal of the radial holes 13.

The descent of the tubing 11 stops when the dual packers 12 are in front of and behind the filter 9.

Calculate the volume of hydraulic fracturing fluid, which is used as a crosslinked gel and a linear gel in a ratio of 2: 1, respectively. For example, take the volume of crosslinked gel - 40 m ³ , linear gel - 20 m ³ . Hydraulic fracturing fluid (cross-linked gel) is pumped at a flow rate of 1-3 m ³ / min. Such a flow rate, according to calculations, ensures the effective creation of cracks, which is selected depending on the depth of the reservoir. The deeper the collector lies, the greater the flow rate required.

The pressure gauge records the increase in injection pressure. A break in the formation rock and formation of a 5 'crack is indicated by a drop in injection pressure and an increase in injectivity of the formation. So after some time of continuous injection, the pressure drops sharply by 20-30%, and the injectivity of the reservoir increases. In this case, during the formation of a crack 5 ', a gel-like fracturing fluid (cross-linked gel) was pumped into the pipe string 8 of well 2 in a volume of 30 m ³ .

Next, the remaining volume of crosslinked gel 10 m ^{3 is} pumped with the addition of proppant, for example, a 12/20 mesh fraction (the choice of proppant for hydraulic fracturing in the first section is carried out as in case of single hydraulic fracturing in vertical wells, using well-known proppants, for example, sand from the company Borovichevsky Refractory Combine ”) with a flow rate of 1.5 m ³ / min. For better fastening, various proppant densities are injected starting from 200 kg / m ³ , which fills the distant fracture zones, and ending with 1000 kg / m ³ , which fills the near fracture zones from the well.

Without interrupting the hydraulic fracturing process, they switch to the injection of a linear gel with proppant with a flow rate of 2 m ³ / min in a volume of 20 m ³ . For better fastening, the density of the proppant is also increased, as when pumping a crosslinked gel.

After the last stage of the linear gel with a propant concentration of 1000 kg / m ^{3 has} been pumped, it is pumped into the formation with a technological fluid with a density equal to the density of the formation water of the given formation, which, according to studies, is more effective than less or more dense fluids.

Excerpt for 10 minutes, i.e. until the injection pressure drops to 11.0 MPa. Next, the double packers are unpacked and removed with the pipe string 11 from the well.

Next, microseismic studies determine the parameters of the crack (thickness, length, azimuth, asymmetry).

Hydraulic fracturing creates for each interval (3, 4, 5, 6) a certain length and permeability in order to ensure equal inflows for each fracture.

In the general case, for the nth interval of a zone-heterogeneous formation according to the Dupuis formula, taking into account the skin factor, we have:

$$q_n=\frac{2\pi k_{n}h\Delta P}{\mu \left(Ln\frac{r_k}{r_c}+S_n\right)},\left(\mathrm{one}\right)$$

where q _n is the flow rate of fluid (oil) to the n-th interval of the well, m ³ / s,

k _n - the permeability of the reservoir of the n-th interval, m ² ,

h is the thickness of the reservoir, m,

ΔР - depression (between the pressure in the reservoir on the supply circuit and in the well), Pa,

µ - oil viscosity in reservoir conditions, Pa ^· s,

r _k is the radius of the power circuit, m,

r _c - well radius, m,

S _n - skin factor of the n-th interval of the bottom-hole formation zone, fractions of units

An assumption must be noted. For horizontal wells, instead of the Dupuis formula, the formulas of Joshi, Borisov, Griguletsky and others are used, however, when conducting multiple hydraulic fracturing, at each of the intervals, the inflow can be considered as a single vertical well, because fluid moves mainly along the fracture.

Having written equation (1) for each of the intervals and equating their right-hand sides, we obtain a relation determining the equality of inflows to each of the intervals:

$$\frac{k_3}{Ln\frac{r_k}{r_c}+S_3}=...=\frac{k_6}{Ln\frac{r_k}{r_c}+S_6}\left(2\right)$$

The expression for the skin factor of a horizontal well in a homogeneous formation:

$$S=\frac{\beta h}{l}\left(\frac{k}{k_s}-\mathrm{one}\right)Ln\frac{r_s}{r_c},\left(3\right)$$

where l is the length of the HS, m,

- коэффициент анизотропии пласта, доли ед., $$\beta =\sqrt{k_{\mathrm{at}}/k_r}$$

- the coefficient of anisotropy of the reservoir, the share of units,

k _in - vertical permeability of the reservoir, m ² ,

k _r - horizontal permeability of the formation, m ² ,

k _s - permeability of the bottomhole formation zone, m ² ,

r _s is the radius of the bottomhole formation zone, m

Since during hydraulic fracturing, cracks form in the bottom-hole zone, their permeability is much higher than the permeability of the formation and the influx does not occur along the entire length of the filter, but mainly only at the crack site, i.e. point flow, then formula (3) can be rewritten for the skin factor of the nth interval, where inflow to the well in the bottomhole zone occurs only along fractures and the factor βh / l _{n is} neglected:

$$S_n=\left(\frac{k_n}{k_{m{p}_n}}-\mathrm{one}\right)Ln\frac{r_{m{p}_n}}{r_c},\left(\mathrm{four}\right)$$

where k _n - the permeability of the reservoir of the n-th interval, m ² ,

k _{mp n} - hydraulic fracture permeability on the n-th interval, m ² ,

r _{mp n} - half-length of hydraulic fractures in the nth interval, m

Microseismic studies establish the half-length of the hydraulic fracture in the 5th interval r _{mp 5} . For the 12/20 mesh proppant fraction, the permeability at reservoir pressure is k _{mp 5} (they are selected according to well-known graphs of pressure permeability for different fractions, for example, Schlumberger plots). Then by the formula (4) find the value 85.

From the formula (2), knowing the skin factor S ₅ , calculate the skin factor of other intervals:

$$S_n=\frac{k_n\left(Ln\frac{r_k}{r_c}+S_5\right)}{k_5}-Ln\frac{r_k}{r_c}\left(5\right)$$

From formula (4) it can be seen that the variable values in the calculation of the skin factors S _n are the permeability of the fractures and the half-length of the fractures. Three cases are possible:

1) injection into each crack of a proppant of a different fraction when creating cracks of the same length,

2) injection of proppant of the same fraction, while cracks are created of different lengths, based on the proportionality of the volumes and speed of injection of hydraulic fracturing fluid with proppant obtained during hydraulic fracturing in the 5th section,

3) a combination of permeability and crack length.

The calculations showed that in real conditions it is rather difficult to create and control the system according to items 1 and 2. Therefore, they are set with the same length and width of cracks, which can be obtained with the same volumes and speed of injection of hydraulic fracturing fluid with proppant. Then from proportionality we can write:

$$\frac{k_{m{p}_n}}{k_{m{p}_{n+\mathrm{one}}}}=\frac{S_n}{S_{n+\mathrm{one}}}\left(6\right)$$

Indeed, for a more negative skin factor, i.e. To “improve” the bottom-hole formation zone, it is necessary to create fractures with greater permeability during hydraulic fracturing, which is confirmed by formula (6).

The permeability of the cracks of the remaining intervals is calculated from the formula (6):

$$k_{m{p}_n}=\frac{S_n}{S_{n+\mathrm{one}}}\cdot k_{m{p}_{n+\mathrm{one}}}\left(7\right)$$

Next, the proppant fractions are selected according to the obtained permeability values and proceed with hydraulic fracturing in the next interval. The process of creating cracks at 3, 4, 6 intervals is similar to the hydraulic fracturing process at 5 intervals.

During the development of oil reserves, water breaks through to the horizontal production well 2. When the water cut is more than 98% of the production well, it is stopped, geophysical surveys are carried out, and watering intervals on the horizontal well are determined. Then cut off the waterlogged intervals with water swellable packers 10 and again put the well into operation.

The development is carried out until the full economically viable development of the site.

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

An example of a specific implementation of the method

In the area of reservoir 1 (Fig. 1) of a massive reservoir, the productive strata of which are represented by pore-fissure zone-heterogeneous carbonate deposits (reservoir depth 1100 m, initial reservoir pressure 12 MPa, purely oil saturated reservoir, 20 m thick), determine the direction of the minimum principal stress rocks δ _min device VAK-8 in neighboring wells, and also conduct 3D seismic and determine the preferred direction of natural fractures S _Tr . As a result of the studies, we obtained the direction δ _min and, accordingly, perpendicular to it, δ _max - north-east, and the direction S _tr - north-west. The angle between S _Tr and δ _max was 60 ° or 120 °. Choose a smaller angle and drill in the direction that is the bisector of this angle, a horizontal well HW with a horizontal part length of 300 m. Perform well logging in an open wellbore, using which the intervals of the reservoir and non-reservoir, their permeability and saturation are determined.

So, as a result of the studies, we received 4 intervals (3, 4, 5, 6) (Fig. 2) of the productive part of the formation 1 along HS 2. Between intervals 3 and 4, as well as 4 and 5, there are sections of non-collector 7.

The lengths of each of the intervals 3, 4, 5, 6 are not more than 150 m, therefore, each of them is planned for one stage of hydraulic fracturing.

As a result of the GIS interpretation, it was also established that the average permeability of the intervals 3, 4, 5, 6, respectively, is k ₃ = 55 mD, k ₄ = 34 mD, k ₅ = 27 mD, k ₆ = 48 mD.

Based on these data, a shank 8 with filters 9 located in oil-saturated intervals 3, 4, 5, 6 of formation 1 is constructed and lowered into an open-cased horizontal shaft. , as well as in places where the permeability of the reservoir is different (decreases or increases).

Then proceed with hydraulic fracturing in each of the intervals, resulting in cracks 3 ', 4', 5 ', 6'.

The process of multiple hydraulic fracturing begins at interval 5 with the lowest permeability. For the remaining sections, the hydraulic fracturing process is similar.

To the interval 5 of the reservoir 1, dual packers 12 are lowered on a tubing string 11 with a diameter of 89 mm, which are placed before and after the radial holes 13, the hydraulic valve 14 and the filter 9. The packers must provide a tight cut-off of the horizontal borehole interval 2 s filter 9.

In the place with the radial holes 13, a hydraulic valve 14 is located, which when injecting fluid into the tubing from the wellhead moves through the piston and spring mechanism 15 back and forth along the axis of the tubing 11 with increasing and decreasing injection pressure. In this case, the radial holes 13 open at an injection pressure of more than 12 MPa. When the injection pressure is less than 12 MPa, the hydraulic valve 14 provides a tight seal of the radial holes 13.

The descent of the tubing 11 stops when the dual packers 12 are in front of and behind the filter 9.

Calculate the volume of hydraulic fracturing fluid, which is used as a crosslinked gel and a linear gel in a ratio of 2: 1, respectively. Take the volume of crosslinked gel - 40 m ³ linear gel - 20 m ³ . Hydraulic fracturing fluid (cross-linked gel) is pumped at a flow rate of 1.5 m ³ / min. The pressure gauge records the increase in injection pressure. The formation rock fracture and the formation of a 5 'crack are evidenced by a drop in injection pressure and an increase in the injectivity of the formation. So, after 20 minutes of continuous injection, upon reaching 35 MPa, the pressure drops sharply by 25% to 26 MPa, and the injectivity of the formation increases by 30% to 2.6 m ³ / min. In this case, during the formation of a crack 5 ', a gel-like fracturing fluid (cross-linked gel) was pumped into the pipe string 8 of well 2 in a volume of 30 m ³ .

Next, the remaining volume of the crosslinked gel 10 m ^{3 is} pumped with the addition of the proppant fraction 12/20 with a flow rate of 1.5 m ³ / min. For better fastening, various proppant densities are injected, starting from 200 kg / m ³ , which fills the distant fracture zones, and ending with 1000 kg / m ³ , which fills the near fracture zones from the well.

Without interrupting the hydraulic fracturing process, they switch to the injection of a linear gel with proppant with a flow rate of 2 m ³ / min in a volume of 20 m ³ . For better fastening, the density of the proppant is also increased, as when pumping a crosslinked gel.

After pumping the last stage of a linear gel with a proppant concentration of 1000 kg / m ³ , it is forced into the reservoir with a process fluid with a density of 1130 kg / m ³ equal to the density of the formation water of this reservoir.

Excerpt for 10 minutes, i.e. until the injection pressure drops to 11.0 MPa. Next, the double packers are unpacked and removed with the pipe string 11 from the well.

Microseismic studies determine the crack parameters (thickness, length, azimuth, asymmetry). It was found that the half-length of the hydraulic fracture in the interval 5 is r _{mp 5} = 8 m. For the 12/20 mesh proppant fraction, the permeability at reservoir pressure is k _{mp 5} = 1000 D. Then, according to formula (4), the radius wells r _c = 0.168 m:

$${\mathrm{<figure-callout\; id="5"\; label="S"\; filenames="00000018.png"\; state="\{\{state\}\}">S</figure-callout>}}_5=\left(\frac{\mathrm{0,027}}{1000}-\mathrm{one}\right)\mathrm{<figure-callout\; id="8"\; label="L\; n"\; filenames="00000018.png"\; state="\{\{state\}\}">L\; </figure-callout>}n\frac{8}{0.168}=-3.86$$

Further, knowing the skin factor S ₅ , we can calculate the skin factor of other intervals by the formula (5), taking into account the fact that the radius of the power circuit r _k = 150 m:

$$S_3=\frac{55\left(Ln\frac{150}{0.168}-3.86\right)}{27}-Ln\frac{150}{0.168}=-0.82$$

$$S_{\mathrm{four}}=\frac{34\left(Ln\frac{150}{0.168}-3.86\right)}{27}-Ln\frac{150}{0.168}=-3.10$$

$${\mathrm{<figure-callout\; id="6"\; label="S"\; filenames="00000018.png"\; state="\{\{state\}\}">S</figure-callout>}}_6=\frac{48\left(Ln\frac{150}{0.168}-3.86\right)}{27}-Ln\frac{150}{0.168}=-\mathrm{1,58}$$

The permeability of cracks of intervals 3, 4, 6 is determined by the formula (7):

$$k_{m{p}_3}=\frac{S_3}{{\mathrm{<figure-callout\; id="5"\; label="S"\; filenames="00000018.png"\; state="\{\{state\}\}">S</figure-callout>}}_5}\cdot k_{m{p}_3}=\frac{-0.82}{-3.86}\cdot 1000=212D$$

$$k_{m{p}_{\mathrm{four}}}=\frac{S_{\mathrm{four}}}{{\mathrm{<figure-callout\; id="5"\; label="S"\; filenames="00000018.png"\; state="\{\{state\}\}">S</figure-callout>}}_5}\cdot {\mathrm{<figure-callout\; id="5"\; label="k\; m\; p"\; filenames="00000018.png"\; state="\{\{state\}\}">k\; </figure-callout>}}_{m{p}_{}}=\frac{-3.10}{-3.86}\cdot 1000=803D$$

$${\mathrm{<figure-callout\; id="6"\; label="k\; m\; p"\; filenames="00000018.png"\; state="\{\{state\}\}">k\; </figure-callout>}}_{m{p}_{}}=\frac{S_6}{{\mathrm{<figure-callout\; id="5"\; label="S"\; filenames="00000018.png"\; state="\{\{state\}\}">S</figure-callout>}}_5}\cdot {\mathrm{<figure-callout\; id="5"\; label="k\; m\; p"\; filenames="00000018.png"\; state="\{\{state\}\}">k\; </figure-callout>}}_{m{p}_{}}=\frac{-\mathrm{1,58}}{-3.86}\cdot 1000=409D$$

Next, the proppant fractions are selected according to the obtained permeability values, sand is selected as in the 5th interval:

- for the 3rd interval of permeability 212 D corresponds to a fraction of 30/40 mesh,

- for the 4th interval of permeability 803 D corresponds to a fraction of 16/30 mesh,

- for the 6th interval of permeability 409 D corresponds to a fraction of 20/40 mesh.

The process of creating cracks in the 3rd, 4th, 6th interval is similar to the hydraulic fracturing process on the 5th interval.

In the process of developing oil reserves, water breaks through to a horizontal production well 2. When the water content of a production well exceeds 98%, it is stopped, geophysical surveys are carried out, and watering intervals on a horizontal well are determined. Then cut off the waterlogged intervals with water swellable packers 10 and again put the well into operation.

The development is carried out until the full economically viable development of the site. As a result, during the development period, which was limited by watering the production well to 98%, or by achieving a minimum profitable oil flow rate of 0.5 t / day per well, 104.4 thousand m ^{3 of} oil was produced from the site, the oil recovery ratio was 0.320. According to the variant without taking into account the different permeabilities in the fractures created during multiple hydraulic fracturing, ceteris paribus, 88.7 thousand m ^{3 of} oil was produced, the oil recovery coefficient was 0.272, the main cause of the less accumulated production was the earlier flooding of the well. The growth rate of oil recovery by the proposed method amounted to 0.048 or 17.6%.

The proposed method, due to the maximum long-term operation of the well until complete flooding and due to the equalization of production rates and uniform production of oil reserves in zone-heterogeneous formations when developed by horizontal wells with multiple hydraulic fracturing, allows to increase oil recovery of the productive formation and, as a result, oil production by 15-20%.

Claims (1)

The method of multiple hydraulic fracturing in a horizontal wellbore, including determining the direction of natural fracture of the rock and its maximum principal stress, isolating the fracture interval in a horizontal wellbore, conducting hydraulic fracturing in an isolated interval, attaching a fracture fracture, characterized in that a horizontal well with a horizontal part length at least 200 m is chosen, or drilled in the direction that is the bisector of a smaller angle between the natural crack vector atosti vector and the maximum principal stress breed, exceeding the length L _n of each interval along the borehole more than 50 m it is carried N = L _n / 100 steps fracturing, where N is rounded up to an integer number initially stage fracturing is performed on the range with the lowest permeability fracturing fluid is pumped at a rate of 3.1 m ³ / min, which is used as a crosslinked gel in series and a linear gel in the ratio 2: 1 respectively and with a fluid with proppant prodavku process performed liq Stu with a density equal to the density of the formation water reservoir, wherein the crack multiple fracturing at each of the intervals is attached proppant such fractions which are selected from the condition of equality of duration of individual production intervals of the formation with a permeability varying by the formula:
$$\frac{k_{\mathrm{one}}}{Ln\frac{r_k}{r_c}+S_{\mathrm{one}}}=\frac{k_2}{Ln\frac{r_k}{r_c}+S_2}=...=\frac{k_n}{Ln\frac{r_k}{r_c}+S_n}$$

,
where k _n - the permeability of the reservoir of the n-th interval, m ² ,
r _c - well radius, m,
S _n - skin factor of the n-th interval of the bottom-hole formation zone, fractions of units,
r _k is the radius of the power circuit, m

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