RU2595112C1 - Method for development of oil deposit at late stage of development - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: invention relates to oil industry and, in particular, to development of oil deposit at late stage of development. Method comprises determining remaining oil reserves in interwell space. For this purpose, method includes selecting flooded oil deposit, from which are selected ≥ 80 % of extracted oil reserves and oil-saturated strata ≥2 m. Based on results of geophysical investigations of wells and laboratory analysis of core, selecting zones with low-producing rocks, opened by adjacent wells. Drainage area in production wells is determined to determine boundaries of zone with residual profitable oil reserves in interwell space. In direction of said zones of adjacent production wells with least development of reserves, additional production side and lateral horizontal shafts are drilled. Length of side and horizontal shafts does not exceed distance between adjacent wells. In presence in section of adjacent wells of more than one oil-filled formation, in each of which there is a zone with residual profitable oil reserves, side shaft is drilled with exposure of all said zones. Displacement agent is injected through injection wells. Product is extracted through production wells.

EFFECT: technical result is higher efficiency of development due to uniform coverage of formation by water flooding and reduction of costs.

1 cl, 2 dwg, 1 ex

Description

The proposed method relates to the oil industry, in particular to the field of development of oil deposits at a late stage of development.

A known method of developing an oil reservoir with a clay reservoir (patent RU No. 2527949, IPC ЕВВ 43/16, publ. 09/10/2014, bull. No. 25), including the injection of a working agent through injection wells and selection of reservoir products through production wells. For development, choose a reservoir or a plot of reservoir with reservoir pressure not lower than the initial one, water cut of 60% or more, recoverable reserves of at least 40 thousand tons. Then, a retrospective analysis of the change in the dynamics of reservoir and bottomhole pressures is carried out in this section and the least developed section with the content clay fraction from 2.5% or more. After the analysis, several design points for drilling vertical injection wells are replaced with one injection well with a horizontal end. A horizontal wellbore is placed in the formation with a strike width of at least 3 m. The wellbore is wired at the boundary of the transition of the reservoir rock from clayey sandstone to siltstone. After commissioning a horizontal injection well, fluid is injected into the formation with constant monitoring of changes in the operating mode of the surrounding producing wells by measuring bottomhole pressure and water cut of the product. After the increase in bottomhole pressure sufficient to intensify the selection of products, work is carried out to optimize the deep pumping equipment for a larger standard size. After the analysis, several design points for drilling vertical production wells are replaced with one production well with a horizontal end. A horizontal wellbore is placed in the formation with a strike width of at least 3 m. The wellbore is wired at the boundary of the transition of the reservoir rock from clayey sandstone to siltstone. After commissioning a horizontal production well, fluid is taken from the reservoir with constant monitoring of changes in the operating mode of the surrounding production wells by measuring bottomhole pressure and water cut of the product. After lowering the bottomhole pressure by 10% below the saturation pressure, work is carried out to increase injection through the impacting injection wells.

The disadvantage of this method is that they do not determine the drainage areas of production wells, do not distinguish the boundaries of zones with residual oil reserves in the interwell space, the development of the deposit is carried out with the drilling of new horizontal wells of large length, each of which replaces several design points for drilling vertical wells, which leads to to increase material costs for well construction. The method does not provide for the option of simultaneously developing residual reserves from zones located in several layers.

The closest in technical essence to the proposed is a method of developing an oil field (patent RU No. 2208137, IPC ЕВВ 43/16, publ. 07/10/2003), including drilling vertical and horizontal wells according to a certain pattern. They pump water and produce oil. According to the invention, at the late stage of development, with high water cut of the produced oil, the centers of accumulation of residual oil reserves in the near-bed part of the formation are determined. Additional horizontal wells or horizontal lateral shafts are drilled from production wells between vertical production and injection wells in the near-side part of the formation. The horizontal part of the wells or shafts is placed perpendicular to the flow lines of formation fluids and at a distance of 60-80% of the distance from injection to vertical production wells. Residual oil reserves are injected into development during depressions, which allow the exploitation of horizontal wells or horizontal sidetracks without pulling the bottom water cones.

The disadvantage of this method is that they do not determine the drainage area of producing wells and do not distinguish the boundaries of zones with residual oil reserves in the interwell space, which complicates the penetration of horizontal shafts into such zones. According to the method, the horizontal part of the wells or shafts is arranged perpendicular to the flow lines of formation fluids at a fixed distance from the nearest production and injection wells, which also reduces the likelihood of a horizontal well entering a zone with cost-effective residual oil reserves. The method does not provide for the option of simultaneously developing residual reserves from zones located in several layers.

The technical task of the proposed method is to increase oil recovery and development efficiency of oil deposits at a late stage of development by involving in the development of zones with residual oil reserves in low-productivity reservoirs as a result of geophysical studies of wells, laboratory core tests, determining the area of drainage of producing wells, as well as ensuring uniform coverage of the formation by water flooding and reduction of material costs for well construction due to drilling of producing wells fettered, lateral horizontal shafts from a previously drilled well stock.

The technical result is achieved by the development method, including determining the residual oil reserves in the interwell space, drilling additional producing lateral and lateral horizontal shafts, opening the residual oil-saturated intervals, pumping the displacing agent through injection wells and selecting products through production wells.

New is that a waterflood oil reservoir is selected from which ≥80% of recoverable oil reserves with oil-saturated thicknesses ≥2 m are selected, according to the results of geophysical studies of wells, laboratory core tests, zones with low-productive rocks discovered by neighboring wells are identified, the drainage areas of producing wells to determine the boundary of the zone with residual cost-effective oil reserves in the interwell space, in the direction of which from nearby producing wells with the lowest production Additional producing lateral and lateral horizontal shafts are drilled by reserves, and the length of the lateral and lateral horizontal shafts does not exceed the distance between neighboring wells.

Also new is the fact that if there are more than one oil-saturated formation in the section of neighboring wells, in each of which a zone with residual profitable oil reserves is established, a sidetrack is drilled with the opening of all these zones.

In FIG. 1 presents a diagram of the implementation of the proposed method for the development of oil deposits (top view) on the site deposits. In FIG. 2 shows a section AA in FIG. one.

The inventive method is carried out in the following sequence.

Select a water-filled oil reservoir 1 (Fig. 1), from which ≥80% of recoverable oil reserves with oil-saturated thicknesses ≥2 m were selected. Based on the results of geophysical studies of wells and laboratory core tests, the geological structure of reservoir 1 is determined, structural maps are constructed, and maps of effective oil-saturated thicknesses along the strata; laboratory core tests are performed. Determine the porosity, oil saturation, permeability, clay content of the formation rocks, the distribution of oil-saturated thicknesses over the area of the reservoir (not shown).

A section of a water-flooded oil reservoir 1 with low productivity rocks (permeability ≤0.1 μm ² and clay content ≥2.0%), discovered by neighboring wells 2, 3, 4, 5, 6, 7, 8, is distinguished.

The drainage areas of 9 production wells 4, 5, 6, 7, 8 are determined to determine the boundary of zone 10 (Fig. 1, 2) with residual profitable oil reserves in the interwell space, for which an analysis of the operation of wells 4, 5, 6, 7, 8 (Fig. 1).

Using the formula for calculating oil reserves by the volumetric method (1), determine the area (2) of drainage of producing wells 4, 5, 6, 7, 8:

where S is the area;

h is the effective oil saturated formation thickness;

Kp - coefficient of open porosity;

Кн - oil saturation coefficient;

p is the oil density under standard conditions;

- пересчетный коэффициент, учитывающий усадку нефти;

- conversion factor taking into account oil shrinkage;

Kin is the oil recovery factor.

Instead of the recoverable oil reserves, Qizv in the formula (2), the accumulated oil selection Qн is used for each production well 4, 5, 6, 7, 8 in the area of reservoir 1, which revealed low-productivity reservoirs:

Then, using the formula for calculating the area of the circle S, determine the radius R of the drainage of each producing well 4, 5, 6, 7, 8:

where π = 3.14.

On the map of effective oil-saturated thicknesses near each producing well 4, 5, 6, 7, 8, circles 9 are applied, the area of each of which is equal to the area of the drainage zone of this well 4, 5, 6, 7, 8. The boundaries of zone 10 with residual oil reserves are identified in the interwell space, which are located between the drainage zones of 9 wells 4, 5, 6, 7, 8 (Fig. 1). Calculate the residual oil reserves in this zone 10 according to the formula (1).

Then, in the direction of zone 10, with additional residual profitable oil reserves, additional producing lateral 11 (Fig. 2) and horizontal lateral 12 (Fig. 1) wellbores are drilled from the well with the least production of reserves, i.e. from the producing well 7 with a smaller drainage radius, and the length of the lateral 11 and lateral horizontal shafts 12 does not exceed the distance between adjacent wells 4, 5, 6, 7, 8.

If there are more than one oil-saturated formation 14, 15 (Fig. 2) in the section of neighboring wells 4, 5, 6, 7, 8, in each of which a zone 10, 13 (Fig. 2) with residual profitable oil reserves is established, drill lateral barrel 11 with the opening of all these zones 10, 13.

Concrete example

The implementation of this method, we consider the example of a section of water-flooded oil reservoir 1 (Fig. 1), characteristic of reservoir deposits of the Pashian horizon. We chose a water-filled oil reservoir 1 with an effective oil-saturated thickness of 5.5 m. We performed geophysical studies of wells, laboratory tests of the core and determined the reservoir properties: reservoir porosity is 19.2%, permeability is 0.096 μm ² , oil saturation is 86%, clay is 2, 3%

A section of water-flooded oil reservoir 1 with low-productive rocks, discovered by wells 2, 3, 4, 5, 6, 7, 8, was identified. Wells 2, 3, 4, 5, 6, 7, 8 were drilled at a distance of 350 m from each other. For each production well 4, 5, 6, 7, 8, the cumulative oil production Qн was determined from the beginning of the development of reservoir 1: in well 4 it amounted to 84 thousand tons, in the well 5-30 thousand tons, in the well 6-41 thousand tons, in the well 7-17 thousand tons, in the well 8-25 thousand tons. The water cut of the produced products in the deposit area reached 94%.

The drainage radii of 9 wells 4, 5, 6, 7, 8 were calculated using formula (2) and circles were plotted on a map of oil-saturated thicknesses (not shown). The boundaries of zone 10 with the residual oil reserves in the interwell space were identified. Recoverable oil reserves were calculated using formula (1). They amounted to 26 thousand tons. From the well 7, which has the smallest accumulated oil production, we drilled a lateral horizontal well 12 180 m long in the direction of the well 6.

The oil production rate from the lateral horizontal wellbore 12 was 10.4 tons / day, and the initial water cut of the produced products was 32.0%. Additional oil production for the year of operation of the horizontal sidetrack 12 amounted to 3.5 thousand tons.

The proposed method for the development of oil deposits allows to increase oil recovery in flooded formations by involving in the development of zones with residual oil reserves in low-productive reservoirs as a result of geophysical studies of wells, laboratory tests of the core, and determination of the drainage area of producing wells. The method also allows to ensure uniform coverage of the formation by water flooding and reduce material costs for well construction by drilling producing lateral, lateral horizontal shafts from a previously drilled well stock.

Claims (2)

1. A method of developing an oil reservoir at a late stage of development, including determining the residual oil reserves in the inter-well space, drilling additional producing lateral and lateral horizontal shafts, opening the residual oil-saturated intervals, pumping the displacing agent through injection wells and selecting products through production wells, characterized in that choose a water-filled oil reservoir from which ≥80% of recoverable oil reserves with oil-saturated thicknesses ≥2 m are selected, according to the results of geophysical x well studies, laboratory core tests, identify zones with low-productive rocks exposed by neighboring wells, determine the drainage areas of production wells to determine the boundary of the zone with residual cost-effective oil reserves in the interwell space, in the direction of which additional production lateral wells are drilled from nearby production wells with the least production reserves and lateral horizontal trunks, and the length of the lateral and lateral horizontal trunks does not exceed the distance between single wells. 2. A method of developing an oil reservoir at a late stage of development according to claim 1, characterized in that if there are more than one oil-saturated formation in the section of neighboring wells, each of which has a zone with residual profitable oil reserves, drill a sidetrack with the opening of all these zones .

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