RU2536891C1 - Development of oil deposit by multihole horizontal wells - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: proposed method comprises extraction of oil via production wells, injection of formation water via injection wells. In compliance with this invention, watered interval of horizontal borehole is defined. Developed borehole core sample is subjected to lab analysis. Core sample is pre-watered to define swelling capacity of clay components in sweet water. Filter is lowered on flow string into watered interval, filter length being equal to that of watered interval. Packers are fitted and packed at the filter inlet and outlet. Then, sweet water is injected with mineralization not over 1.5 g/l and content of solid suspended particles of 70-200 mg/l taken from well products to decrease the capacity twofold of initial value. Holding if performed for time interval sufficient for swelling of clay components of the pod.

EFFECT: decreased watering, higher oil yield.

3 ex

Description

The invention relates to the oil industry and may find application in the development of flooded heterogeneous clay productive formations.

A known method for the development of oil reservoirs with layer-by-layer heterogeneous permeability, including introducing clay suspension rims into the formation, depending on the pore volume, allowing clay suspension to move around the well with mud blocking the pore channels with dispersed clay particles and converting the introduced clay suspension rim into a flow-deflecting barrier, according to the invention, a production well watered with water injected into the formation is selected with a ratio of permeability of reservoirs in perforated parts of the formation 1.5 and more, in a radius of 25 m around the well in the interval of the formation with a permeability exceeding the average value of the parameter for the perforated part, a clay suspension with a clay concentration of 30-60 kg / m ³ is introduced in an amount of 0.5 pore volume with the assumption its uniform radial movement in the formation, and for converting the introduced rim of the clay slurry into a flow-deflecting barrier, the production well is closed, while the flow-deflecting barrier is deformed and compacted under the pressure of a moving from the interacting supercharger nnoy wells of the front of the injected water (RF patent 2157884, class E21B 43/20, publ. 10/20/2000).

Closest to the technical nature of the proposed method is a method of developing an oil reservoir, including the selection of produced products through production wells, pumping a working agent at operating pressure and flow rate through injection wells. As a working agent, produced water is used, purified to the presence of suspended solids of not more than 60 mg / l and an oil emulsion of not more than 50 mg / l. An increase in injection pressure is carried out with a loss of injectivity due to the clogging of the borehole zone of the injection well with solid suspended particles and an oil emulsion. Water is injected into the injection well without collimating substances at an elevated pressure, at which the well receives in a volume sufficient to distribute the clogging substances in the formation and increase the injectivity of the injection well. With continuous injection, they proceed to the injection of the working agent at the newly set operating pressure and flow rate (p + RF patent No. 2394980, publ. 07.20.2010 - prototype).

A common disadvantage of the known methods is the rapid water cut of the produced products.

The proposed invention solves the problem of reducing the water content of the produced products and, as a result, increasing the oil recovery of the reservoir.

The problem is solved in that in the method of developing an oil field by horizontal wells, including selecting produced products through production wells, injecting produced water through injection wells, according to the invention, the horizontal cut-off interval of the horizontal well is determined in a horizontal producing well, laboratory tests are conducted on the core of the reservoir being developed, core pre-flooded, determine the swelling of clay components in fresh water, on a string of tubing in the horizontal horizontal barrel interval, a filter equal to the length of the flooded interval is lowered, packers are installed at the beginning and end of the filter, packers are packed, fresh water is pumped along the tubing string with a salinity of not more than 1.5 g / l and suspended solids content 70- 200 mg / l, which is taken from the production of wells extracted from this formation, before the injection rate drops at least two times from the original, hold for a time sufficient for the clay components to swell lecturer, and put the well into operation.

SUMMARY OF THE INVENTION

The oil recovery of the terrigenous oil reservoir, developed by horizontal wells, is significantly affected by the time the wells run until they are completely flooded. Existing technical solutions do not fully allow to perform this task. The reservoirs are almost always heterogeneous, which leads to watering the wells. Water in more permeable sections of the reservoir is filtered towards the bottom of the wells and, due to the difference in the viscosity of oil and water, water occupies a significant portion in the fluid flow from the well. As is known, terrigenous reservoirs are mainly represented by sandstones, siltstones and clays. The well-known property of clay particles swelling under the influence of fresh water does not always completely limit water inflow from the irrigated area, which is associated with heterogeneity of the formation. Therefore, the combined use of water injection with solid suspended particles to clog the pores of the formation (“contamination” of the formation) significantly increases the efficiency of limiting water inflow. The proposed invention solves the problem of increasing oil recovery of oil deposits by means of as long as possible well operation until complete flooding. The problem is solved as follows.

The method is implemented as follows.

The section of the oil reservoir, represented by the terrigenous type of reservoir and the purely oil zone, was opened by a horizontal well with an open horizontal wellbore. During the development of the reservoir, a breakthrough of water from neighboring injection wells into the horizontal well occurs, as a result, the well is flooded.

A complex of geophysical studies is carried out, according to the results of which it is established that a section of a layer of length L is watered along a horizontal well

When drilling a well, a core of the formation was selected. Prior to the measures to limit water inflow, laboratory studies on the core are carried out.

In one of the cores, a piece of clay material is isolated. The time t of the swelling of the clay particles is determined by the contact of this clay material with fresh water with a salinity of not more than 1.5 g / l.

Next, laboratory tests are carried out on the core to flood it with fresh water with a total mineralization of not more than 1.5 g / l. The core has a length l = 4 cm and a diameter d = 3 cm. It is pre-flooded. Determine the optimal concentration of suspended solids (HD) in the injected water, which leads to clogging of the pores of the formation, i.e. its pollution. Moreover, HDTV is taken from the production of wells extracted from this formation.

Studies have found that for the vast majority of terrigenous reservoirs, the concentration of HDTV should be in the range of 70-200 mg / l. Also, according to studies, water salinity of more than 1.5 g / l reduces the efficiency of clay particles swelling. To effectively limit water inflow, clay particles should increase in volume by at least 2 times.

. При этом наблюдали падение приемистости керна не менее чем в 2 раза от первоначальной, после чего закачку прекратили. Согласно исследованиям падение приемистости менее чем в 2 раза не приводит к достаточному забиванию пор пласта для ограничения водопритока.As a result of laboratory tests, a volume of water was pumped through a core. $$Q_s^{\mathrm{to}}$$

. In this case, a drop in core injectivity of at least 2 times from the initial one was observed, after which the injection was stopped. According to studies, a drop in injectivity of less than 2 times does not lead to sufficient clogging of the pores of the formation to limit water inflow.

Next, the required volume of water injection is recounted to limit water inflow into the reservoir through the irrigated area. Assuming the fact that the pumping of water on the core and in a real reservoir is proportional to their size, we can write the ratio:

where Q ₃ - the required volume of water injection to limit water inflow from the flooded section of the reservoir, m ³ ,

- объем прокаченной воды для ограничения водопритока при лабораторных исследованиях на керне, м³,

- the volume of pumped water to limit water inflow during laboratory tests on the core, m ³ ,

V is the pore volume of the flooded section of the reservoir, m ³ ,

V _to - the pore volume of the core, m ³ .

The pore volume of the irrigated area and core can be calculated by the corresponding formulas:

where h is the thickness of the reservoir, m,

S is the distance between the wells, m,

L is the length of the irrigated area, m,

m - formation porosity, fractions of units

where d is the core diameter, m,

l - core length, m

Substituting expressions (2) and (3) in the formula (1), we obtain:

Formula (4) shows the theoretical volume of water injected to limit water inflow into the formation, which clogs the pores of the formation. However, the calculations showed that the time of pumping water on the core is much less than the swelling time of clay particles t. Therefore, formula (4) is valid in the complete absence of clay in the reservoir.

Studies have shown that clay in most terrigenous formations contains from 1% and above. Therefore, according to the experiments, to limit water inflow from the reservoir, it is enough to pump less than 1% of the water calculated by the formula (4). Then it is necessary to wait for a time t until the clay swelling process passes. Then finally we have:

Further, the well is jammed. On the string of tubing, a filter is lowered with a length equal to the length of the flooded interval L. Packers are installed at the beginning and end of the filter. After the filter is lowered, the packers are sealed opposite the waterlogged area. Water is injected for water limitation in the volume Q _З calculated according to formula (5) with such a flow rate that the injection time is much less than the clay swelling time t.

After injecting the volume Q _3, hold for a time t and then 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 due to the longest possible operation of the well until complete flooding.

Examples of specific performance of the method

Example 1. The section of the oil reservoir, represented by the terrigenous type of reservoir and a purely oil zone with a thickness of h = 10 m, was opened by a horizontal well with an open horizontal well of 320 m in length.

The reservoir lies at a depth of 1090 m, the permeability of the reservoir is 0.7 D, the porosity is m = 28%, the initial reservoir pressure is 11 MPa, the viscosity of the water in the reservoir is 1.6 MPa · s, the viscosity of the oil in the reservoir is 58.3 MPa · s .

The layer is being developed by water flooding. Formation water is pumped through injection wells and produced products are taken through production wells.

During the development of the reservoir, water breaks out from neighboring injection wells located at a distance of S = 250 m into the horizontal well of the producing well. As a result, the well is flooded to 99%.

A complex of geophysical surveys is carried out, according to the results of which it is established that a section of the formation with a length of L = 12 m was irrigated along the horizontal wellbore.

When drilling a well, a core of the formation was selected. Prior to the measures to limit water inflow, laboratory studies on the core are carried out.

In one of the cores, a piece of clay material is isolated. Determine the time t of swelling of clay particles in 2 times by contact of this clay material with fresh water with a salinity of 0.95 g / L. Time t was 2 days.

Next, laboratory tests are carried out on the core to flood it with fresh water with a total salinity of 0.95 g / l. The core has a length l = 4 cm and a diameter d = 3 cm. It is pre-flooded. The optimal concentration of HDTV in the injected water is determined, which leads to clogging of the pores of the formation, i.e. his colmatization. The optimal concentration of HDTV was 80 mg / L. Moreover, HDTV is taken from the production of wells extracted from this formation.

м³. Прокачку осуществляли до падения приемистости керна в 2 раза от первоначальной.As a result of laboratory tests, a volume of water was pumped through a core. $$Q_s^{\mathrm{to}}=0,05\cdot {10}^{-3}$$

m ³ . Pumping was carried out until the core injectivity dropped by 2 times from the initial one.

Next, the required volume of water injection is recounted to limit water inflow into the reservoir through the irrigated area according to the formula (5):

Take O ₃ = 500 m ³ .

Further, the well is jammed. On the tubing string, a filter is lowered with a length equal to the length of the waterlogged interval L = 12. At the beginning and end of the filter, packers are installed. After the filter is lowered, the packers are sealed opposite the waterlogged area. Water is injected for water limitation in a volume of Q ₃ = 500 m ³ for a time less than time t. Thus, the injection is carried out with a flow rate of q _s less than 500/3 = 166.6 m ³ / day. Take q ₃ = 150 m ³ / day. In addition, according to the results of previous hydrodynamic studies, injectivity q ₃ = 150 m ³ / day is provided at an injection pressure at the bottom of the well equal to 16 MPa. The injection is carried out until the injection rate drops at least twice, i.e. up to 75 m ³ / day from the original, while recording an increase in discharge pressure from 16 to 21 MPa.

After injecting a volume of Q ₃ = 500 m ³ , exposure is carried out for a time t = 3 days and then the well is put into production.

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

Example 2. Perform, as example 1. The concentration of HDTV is applied equal to 70 mg / L.

Example 3. Perform, as example 1. The concentration of the HDTV is used equal to 200 mg / L.

As a result of development, which was limited by watering the production well from 2 to 98%, 123.2 thousand tons of oil were produced from the site over 32 years of development, the oil recovery ratio (CIN) was 0.421. According to the prototype, ceteris paribus, the well was watered earlier, 83.6 thousand tons of oil was produced in 23 years of development, oil recovery factor was 0.286. The increase in recovery factor by the proposed method is 0.135.

The proposed method allows to reduce the water content of the extracted products and increase oil recovery of the reservoir.

The application of the proposed method will allow to solve the problem of increasing oil recovery of the terrigenous reservoir due to the maximum long-term operation of the well until complete flooding during the development of the reservoir by horizontal wells.

Claims (1)

A method of developing an oil reservoir by horizontal wells, including selecting produced products through production wells, injecting produced water through injection wells, characterized in that a horizontal borehole water cut is determined in a horizontal production well, laboratory tests are conducted on a core of a developed formation, the core is pre-flooded, and swelling is determined clay components in fresh water on a tubing string in a waterlogged interval horizon filter the length of the flooded interval, the packers are installed at the beginning and end of the filter, the packers are packaged, fresh water is pumped through the tubing string with a salinity of not more than 1.5 g / l and a suspended solids content of 70-200 mg / l, which are taken from the production of wells extracted from a given formation, before the injection rate drops at least two times from the initial, hold for a time sufficient to swell the clay components of the reservoir, and start the wells have commissioned.