RU2464414C1 - Method of developing multi-bed massive oil deposit - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: proposed method comprises defining oil deposit geological and physical conditions and ranging oil bands to decrease in bed permeability, primary exposure of oil beds by drilling, completing and setting up to lift bed fluid and injecting displacement fluid to maintain bed pressure. In compliance with this invention, at least one well is drilled to expose every bed in dome and bottom sections by vertical and horizontal sections of the well. Well horizontal section is arranged parallel with and above oil-water contact. In completing the well, simultaneous secondary exposure of oil beds in horizontal and vertical bottomhole sections is carried out starting from oil bed with maximum water permeability. Every next oil bed is exposed another time as previous bed is depleted to residual reserves equal to initial reserves of the next oil bed with due allowance for the difference in their water permeability. Well is set up to inject displacement fluid into borehole horizontal section with simultaneous lift of bed fluid from well vertical section.

EFFECT: higher efficiency.

1 ex, 1 dwg

Description

The proposed method relates to the oil industry, in particular to the field of development of multilayer oil deposits of massive type.

A known method of developing an oil field of massive type, comprising drilling a field with a system of wells with vertical and horizontal wells (patent RU No. 2095551, IPC EV 43/20, publ. 10.11.1997). Initially, a vertical well is drilled with the opening of the oil-saturated and water-saturated parts of the reservoir. In the case of a favorable characteristic of the geological structure of the reservoir, a horizontal well is drilled in the oil-saturated part in the same well. Then cyclically pump the displacing agent into the water-saturated part of the vertical wellbore formation and select products from the horizontal wellbore.

The disadvantage of this method is that the injected displacing agent along the subvertical cracks is filtered under the oil reservoir, and part of the oil is forced out under the reservoir into the aquifer of the reservoir. This reduces the coverage of formations by water flooding, oil recovery from them and rapid flooding.

A known method of operating a well of a multilayer oil field, including the separation in the well of the upper powerful formation and lower low-power formations (patent RU No. 2334084, IPC ЕВВ 43/14, published on September 20, 2008, Bull. 26). First, the upper powerful formation is developed to a water cut of 75-90%, then they switch to simultaneous and separate well operation, for which the upper of the low-power formations is perforated, the upper powerful formation and the perforated upper low-power formation are separated. Formation fluids are selected simultaneously-separately with preferential selection from a low-power reservoir with a well water cut of less than 75-90% being established. After reaching a water cut of well production of 75-90%, the next shallow low-thickness formation is perforated, the perforated formation and upper layers are uncoupled, reservoir fluids are taken simultaneously and separately with preferential selection from the perforated low-power formation with a well water cut of less than 75-90% being established, after reaching the water cut 75-90% of the well’s production is perforated by the next low-power formation in depth and the operations are repeated until the lowest low-grade formation is developed and water cut is reached well production 75-90%, determine the inflow and water cut of each formation, isolate completely watered formations, and the remaining formations produce a common filter.

The closest in technical essence to the proposed one is a method for simultaneously and separately operating objects of an injection or production well, according to which the lower object is used as the injection well, and the upper object of the well is used as the production well, or the packer is installed either only between objects or one packer is installed above and the other between the objects, while the projected flow of the working agent into the lower object is pumped from the wellhead through the passage cavity formed between the column and pipes of larger and smaller diameter, and the fluid flow rate is measured and controlled at the wellhead, selecting it from the upper chamber through the checkpoint object column of smaller diameter tubes (2006137251/03 application, publ. 27.04.2008. Bull. 12).

The known method does not allow for unambiguous use of each formation for its intended purpose due to the lack of information about the tightness of the packers and possible messages of the layers inside the well.

The technical task of the proposed method is to increase the efficiency of developing a multilayer oil reservoir of massive type, to increase the volume of oil production by increasing the efficiency of injection of the displacing agent.

The technical problem is solved by the method of developing a multilayer oil reservoir of a massive type, including determining the geological and physical conditions for the occurrence of the reservoir and ranking the oil reservoirs in decreasing hydraulic conductivity, initial drilling of the oil reservoirs, completion and completion of wells for raising the reservoir fluid and injecting displacing fluid to maintain reservoir pressure.

It is new that at least one well is drilled with primary opening of each oil reservoir in the dome and lower parts of the reservoir by vertical and horizontal sections of its trunk, the horizontal section of the wellbore is placed parallel to and above the oil-water contact, while completing the well, a simultaneous secondary opening of the oil layers in the vertical and horizontal sections of the wellbore sequentially, starting with the oil reservoir with the highest hydraulic conductivity, each of which the next oil reservoir is re-opened as the previous oil reservoir is developed to residual reserves equal to the initial reserves of the subsequent oil reservoir, taking into account the difference in their hydraulic conductivity, equip the well with the possibility of pumping displacing fluid into a horizontal section of the wellbore while lifting the formation fluid from a vertical section of the wellbore .

In FIG. a section of a massive multi-layer oil reservoir with a horizontal well in the oil-water zone and producing vertical wells in the proposed method is presented.

The inventive method is carried out in the following sequence.

Massive multi-layer oil reservoir of massive type 1 with water-oil zones is drilled by vertical wells 2 along the design grid. Clarify the geological structure of the reservoir, build a structural map, maps of the total and effective oil-saturated thicknesses, conduct core laboratory tests, determine the oil viscosity, porosity, permeability of the reservoirs, the distribution of oil-saturated thicknesses of the reservoir by the area of the reservoir, conduct hydrodynamic studies with the obligatory determination of reservoir pressure and process simulation development. Choose a deposit with a total oil-saturated thickness of more than 15 m.

Strata with different hydroconductivity 3, 4 are isolated. Initial recoverable reserves of these strata in the considered area are calculated.

At least one well 5 is drilled with primary opening of each oil reservoir in the dome and lower zones of the reservoir by vertical and horizontal sections of its trunk.

The horizontal section of the wellbore is placed parallel to and above the oil-water contact (WOC) 6 at a distance of at least one meter in the direction from the dome to the oil contour of the reservoir.

When completing the well, simultaneous secondary opening of oil reservoirs is carried out in vertical 7 and horizontal 8 sections of the wellbore.

Secondary autopsy is carried out sequentially, starting from the oil reservoir 3 with the highest hydroconductivity, and each subsequent oil reservoir 4 is re-opened as the previous oil reservoir 3 is developed to residual reserves equal to the initial reserves of the subsequent oil reservoir 4, taking into account the difference in their hydraulic conductivity.

The vertical part of the horizontal well is separated from the horizontal well by packers 9.

Equip the well with the possibility of pumping water into a horizontal section of the bore 8 of the well 5 while raising the formation fluid from the vertical section of the borehole 7.

The trajectory of the horizontal wellbore 5 intersects twice the same age according to the underlying oil-bearing strata 3, 4. Since carbonate rocks have a fracture, the likelihood of a more intense effect of the injected displacing agent on the strata increases.

The mechanism of oil displacement by a displacing agent is to spread the zone of influence of the displacing liquid 10 up and down the section and over the area of the reservoir with increasing injection pressure. The displacing fluid 10 tends to the upper part of the reservoir along the most permeable formations 3, 4, moving the oil to the intervals of perforation 7.

The selection of products is carried out using a pump from the vertical part of the well 7 simultaneously with the injection of displacing fluid into the horizontal wellbore 8.

The injection mode is selected depending on the hydraulic conductivity of the reservoirs, the distribution of oil-saturated thickness of the reservoirs over the area of the reservoir.

The distance from the lower interval of perforation of the vertical part to the horizontal wellbore is specified by geohydrodynamic modeling.

In order to obtain the maximum effect of the displacing agent on oil reservoirs 3, 4, the injection of the displacing agent is carried out with an increase in reservoir pressure by 10-20% compared with the selection zone. As a result, a stable and continuous effect on oil-bearing strata, the effective use of displacing fluid, and an increase in the flow rate and volumes of produced products are ensured.

Periodically measure the flow rate of the well, reservoir pressure, reservoir temperature, water cut and regulate the mode of operation of the well.

Practical example

The implementation of this method, consider the example of a multilayer oil reservoir of massive type 1 of the Bashkir tier. A massive multi-layer oil reservoir of massive type 1 with water-oil zones is drilled with vertical wells 2 along a 300 × 300 m grid. According to deep hole drilling and 2D seismic studies in the field, the geological structure of the reservoir is refined, a structural map, maps of general and effective oil-saturated are constructed thicknesses.

Carry out laboratory core studies, geophysical studies of wells and determine reservoir properties of the formation: porosity is 15.2%, oil saturation is 79.7%. Then conduct hydrodynamic studies in wells 2 and determine the reservoir pressure, which is 12.1 MPa, permeability - 0.0848 μm ² and carry out modeling of the development process.

Choose a site of deposits with total oil-saturated thicknesses of more than 20 meters. Two oil-bearing strata 3, 4 with different hydroconductivity are distinguished. Calculate the initial recoverable reserves of these layers in the considered area. Formation 3 has higher reservoir properties than the underlying formation 4. The reserves of the upper oil-bearing formation 3 exceed the reserves of the lower 4 by 1.6 times.

One horizontal well 5 is drilled in the direction from the dome to the oil profile of the reservoir. A horizontal section of the wellbore 300 m long is placed parallel to and above the oil-water contact (WOC) 6 at a distance of two meters.

When completing the well, a simultaneous secondary opening of the oil reservoir 3 at the vertical 7th section of the wellbore and the oil reservoir 3 at the horizontal 8th section of the wellbore is performed.

Secondary autopsy is carried out sequentially, starting with the oil reservoir 5, characterized by the greatest hydraulic conductivity. The development of oil reserves from oil reservoir 5 was carried out for two years. With a decrease in reserves in reservoir 5 to the initial reserves of oil reservoir 6, a second opening of the oil reservoir 6 was carried out and put into operation.

The vertical part of the horizontal well is separated from the horizontal well by packers 9.

Equip the well. The injection of the displacing fluid into the horizontal section of the bore 8 of the well 5 is carried out while the formation fluid 10 is taken from the vertical section of the borehole 7. The products are selected using a pump.

The distance from the lower interval of perforation of the vertical part to the horizontal wellbore is 6 m.

In order to maximize the effect of the displacing agent on the oil reservoirs 3, 4, the injection of the displacing fluid 10 is carried out with a reservoir pressure of 14.0 MPa.

The development of a massive multi-layer oil reservoir with water-oil zones by the proposed method allows to increase the volume of oil production, provides uniform oil displacement across all oil reservoirs, which is achieved by increasing the efficiency of injection of the displacing agent.

Claims (1)

The method of developing a multilayer oil reservoir of massive type, including determining the geological and physical conditions of occurrence of the reservoir and ranking the oil reservoirs in decreasing hydraulic conductivity, initial drilling of the oil reservoirs, completion and arrangement of wells for raising the reservoir fluid and injecting the displacing fluid to maintain reservoir pressure, characterized in that at least one well is drilled with the primary opening of each oil reservoir in the dome and lower parts of the reservoir In the horizontal and horizontal sections of its trunk, the horizontal section of the wellbore is placed parallel to and above the oil-water contact, when the well is completed, the oil reservoirs are simultaneously re-opened in the vertical and horizontal sections of the wellbore sequentially, starting from the oil reservoir with the highest hydraulic conductivity, each subsequent oil reservoir being secondary open as the previous oil reservoir develops to residual reserves equal to the initial reserves of the subsequent oil the reservoir, taking into account the difference in their hydraulic conductivity, equip the well with the possibility of pumping the displacing fluid into a horizontal section of the wellbore while lifting the formation fluid from the vertical section of the wellbore.

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