RU2536895C1 - 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, technologies are used at drilling that allow opening and closing of every borehole. This allows definition of watered horizontal borehole. Developed borehole core sample is subjected to lab analysis. Said core sample is, first, dewatered to define swelling capacity of clay components in sweet water and plugging of seam pores with solid suspended particles. At open watered borehole and other closed boreholes, sweet water in injected to the well at mineralization of 1.5 g/l and content of solid suspended particles of not over 40 mg/l in amount equal to 1-10% of threshold space of well bottom zone of said borehole. Holding if performed for time interval sufficient for swelling of clay components of the pod. Then, water is injected with content of solid suspended particles of 70-200 mg/l taken from well products to decrease the capacity twofold of initial value. Injection is terminated to start operation of the well.

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 suspension 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 pump noy front well injection water (RF Patent 2157884, cl. 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 proceed to the injection of the working agent at the newly set operating pressure and flow rate (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 and, accordingly, the low oil recovery of the oil reservoir.

In the proposed invention solves the problem of reducing the water content of the extracted products and increase oil recovery of oil deposits.

The problem is solved in that in the method of developing an oil field by multilateral horizontal wells, including selecting produced products through production wells, injecting produced water through injection wells, according to the invention, in multilateral horizontal production wells during drilling, the design includes technical solutions that ensure the opening and closing of each the trunk, with the help of which the horizontal watered trunk is determined, laboratory tests are carried out on the core about the formation, the core is pre-flooded, the swelling of clay components in fresh water and clogging of the pores of the formation with solid suspended particles with an open flooded well and closed others are separately determined, fresh water is pumped into the well with a salinity of not more than 1.5 g / l and the content of suspended solids not more than 40 mg / l in a volume equal to 1-10% of the pore space volume of the bottomhole formation zone of the considered horizontal wellbore, hold for a time sufficient for the clay component to swell collectors, after which water with a content of suspended solids of 70-200 mg / l, which is taken from the products of wells extracted from a given formation, is injected until the injectivity drops at least twice from the initial one, then the injection is stopped and the well is put into operation .

SUMMARY OF THE INVENTION

The oil recovery of a terrigenous oil reservoir developed by multilateral horizontal wells is significantly affected by the operating time of the wells 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 significantly larger part 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, after using injection technology, in which clay swells, it is advisable to pump water with solid suspended particles (HDTV) to clog the pores of the formation (formation contamination). This greatly increases the efficiency of water restriction. It should also be noted that conducting studies to determine the waterlogged interval in each barrel is a rather complicated technical and technological process, which is not always possible to implement.

The proposed technical solution for the consistent use of fresh and "contaminated" water injection can simplify the process and increase the efficiency of reducing water cut. 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.

A section of the oil reservoir, represented by the terrigenous type of reservoir and a purely oil zone of thickness, was opened by a multilateral horizontal well with open horizontal trunks. When drilling such a well in the design, technical solutions are provided that provide for the opening and closing of each well, individually, or all together, or several — the so-called “shutters”. Management of these "shutters" is carried out from the wellhead.

In the process of developing the formation, a breakthrough of water from neighboring injection wells into the horizontal well occurs, as a result, the well is flooded.

By alternately opening one trunk and closing the others while the well is running, a horizontal horizontal waterlogged well is determined.

During the drilling of the considered well, the 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 for water flooding with a concentration of HDTV in the range of 70-200 mg / l. It is pre-flooded. HDTVs added to the injected water are taken from the same reservoir, selected during the production of the well and its cleaning. The optimal concentration of HDTV in the injected water is determined, which leads to clogging of the pores of the formation, i.e. its pollution within the specified limits.

Studies have found that for the vast majority of terrigenous reservoirs, 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 studies of water injection with HDTV, a volume of water was pumped through a core $$Q_{t\mathrm{at}h}^{\mathrm{to}}$$

. 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 pores in the formation to limit water inflow.

Further, the well is jammed. They cover all the trunks with “blinds”, except for the flooded one. Fresh water is pumped into the well with a salinity of not more than 1.5 g / l and a concentration of HDTV of not more than 40 mg / l in a volume of Q _ol equal to 1-10% of the pore volume of the bottomhole formation zone of the horizontal wellbore. The radius of the bottomhole zone can be estimated from the results of previously conducted hydrodynamic studies. According to calculations, it is enough to pump fresh water in a volume of 1 to 10% of the pore volume of the bottomhole zone, because The waterlogged interval, according to research, corresponds to the specified limits of the total length of the horizontal trunk. Also, a concentration of HDTV of less than 40 mg / l does not clog the pores of the formation, which facilitates the penetration of fresh water deeper into the formation.

After injection of the volume Q _pr , an exposure is carried out for a time t determined by laboratory tests. During this time, the clay components of the reservoir swell at least 2 times.

Then, water with HDTV is pumped into the well. The required volume of water injection with HDTV can be determined by conversion from the core to the real reservoir in proportion to their size. However, since the length of the flooded interval in the horizontal trunk is not known, this approach will not be accurate. Therefore, the volume of water _injected with HDTV _QHTV is determined by the drop in injectivity not less than 2 times from the original, as was observed in laboratory studies on the core.

Next, the injection is stopped and the well is put 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 multilateral horizontal well (MZGS) with three open horizontal shafts 210 m, 260 m and 305 m long.

The formation lies at a depth of 1050 m, the permeability of the formation is 830 mD, the porosity is m = 21%, 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 55.1 MPa · s.

The radius of the bottomhole zone of the MZGS trunks was estimated by the results of hydrodynamic studies, the radius was r = 15 m.

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

In the process of developing the formation, a breakthrough of water from neighboring injection wells into the horizontal trunk of the producing MZGS occurs. As a result, the well is flooded to 99%.

By alternately opening one trunk and closing the others while the well is running, a horizontal horizontal waterlogged well is determined. It was found that this is a trunk with a length of L = 260 m.

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 the swelling of clay particles in 2 times by contact of the clay material with fresh water with a salinity of 0.98 g / L. Time t was 2 days.

=0,055-10^-3 м³.Next, laboratory tests are carried out on the core for water flooding with a concentration of HDTV in the range of 70-200 mg / l. Moreover, in this case, commercial or produced water is used. The core has a length of 4 cm and a diameter of 3 cm. It is pre-flooded. HDTVs added to the injected water are taken from the same reservoir, selected during the production of the well and its cleaning. The optimal concentration of HDTV in the injected water is determined, which leads to clogging of the pores of the formation, i.e. its pollution within the specified limits. During the injection, a drop in core injectivity of 2 times from the initial one is observed, after which the injection is stopped. The optimal concentration of HDTV, according to studies, was 100 mg / L. As a result of laboratory studies of water injection with HDTV, a volume of water was pumped through a core $$Q_{t\mathrm{at}h}^{\mathrm{to}}$$

= 0,055-10 ^-3 m ³ .

Further MZGS jam. They cover all the trunks with “blinds”, except for the flooded one. Fresh water is pumped into the well with a mineralization of not more than 1.5 g / l and a concentration of HDTV of 20 mg / l in a volume equal to 1-10% of the pore volume of the bottom-hole formation zone Q _pr = (0.01 ... 0.1) · L · h · 2r · m = 260 · 10 · 2 · 15 · 0.21 = (0.01 ... 0.1) · 16380 m ³ . Take Q _pr = 0.02 · 16380 = 328 m ³ . This volume is pumped in a time not exceeding the time t of the swelling of clay particles. Thus, the injectivity during the injection of fresh water is 328/2 = 164 m ³ / day. Download lead within 2 days.

After injection of the volume Q _pr, hold is carried out for a time t = 2 days. During this time, the clay components of the reservoir swell at least 2 times.

Then water with HDTV is pumped into the well, which is taken from the same reservoir, selected during the production of the well and its cleaning. The concentration of HDTV in the injected water is 100 mg / l, as determined by laboratory tests. The volume of water _injected with HDTV _QHTV is determined by the drop in injectivity 2 times from the original, as was observed in laboratory tests on the core.

According to the results of previous hydrodynamic studies, the injectivity q ₃ = 100 m ³ / day is provided at an injection pressure at the bottom of the well equal to 15 MPa. Thus, the injection is carried out with an injectivity of q ³ = 100 m ³ / day. After 4 days. injectivity drops to 50 m ³ / day, which indicates the process of "pollution" of the reservoir. Next, the injection is stopped and the well is put into operation.

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

Example 2. Perform, as example 1. The concentration of the 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 the development, which was limited by watering the production well to 98%, 231.8 thousand tons of oil was extracted from the site over 34 years of development, the oil recovery ratio (CIN) was 0.436. According to the prototype, ceteris paribus, the well was watered earlier, 181.3 thousand tons of oil was produced over 27 years of development, the recovery factor was 0.341. The increase in recovery factor by the proposed method is 0.095.

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 with multilateral horizontal wells.

Claims (1)

A method of developing an oil field by multilateral horizontal wells, including selecting produced products through production wells, injecting produced water through injection wells, characterized in that in multilateral horizontal production wells during drilling, the design includes technical solutions for opening and closing each well, whereby determine the watered horizontal trunk, conduct laboratory tests on the core of the reservoir being developed, core pre but they are flooded, the swelling of clay components in fresh water and clogging of the pores of the formation with solid suspended particles with an open flooded well and closed others are separately determined, fresh water is pumped into the well with a salinity of not more than 1.5 g / l and a suspended solids content of not more than 40 mg / l in a volume equal to 1-10% of the pore space volume of the bottomhole formation zone of the considered horizontal wellbore, hold for a time sufficient for the clay components of the reservoir to swell, after which pump water with a suspended solids content of 70-200 mg / l, which is taken from the production of wells extracted from this formation until the injection rate drops at least twice from the initial one, then the injection is stopped and the well is put into operation.