RU2225941C1 - Method for exploiting oil deposits - Google Patents

Abstract

FIELD: oil extracting industry. SUBSTANCE: method includes drilling deposit with extracting and force-pump wells and perforation of productive layer in extracting wells during two main steps. First step is pumping water through force-pump wells, second step is extracting oil from through extracting wells. In accordance with a table of extracting wells locations location of extracting wells pit-faces is determined in the area of local domical rise or local valley. During first step in case of extracting well pit-face located in local valley area perforation of extracting well is performed in range of sole portion of productive layer. In case of extracting well pit-face located in local valley area perforation of extracting well is performed at whole range of productive layer thickness. During second step, perforation of roof portion of productive layer is performed in extracting wells in the area of local valley in case of water amount of 50% and higher. In extracting wells located in the area of local domical rise, sole portion of productive layer is isolated. EFFECT: increased period of waterless oil extraction and increased current coefficient of oil extraction. 1 ex, 1 dwg

Description

The invention relates to the oil industry, and in particular to methods for developing oil fields, developed with maintaining reservoir pressure by pumping water into the reservoir through injection wells. It can be used in linear, block-closed and areal systems.

There is a method of developing an oil reservoir with bottom water and deteriorating permeability to the roof, which involves conducting geophysical surveys, identifying all interbeds of impermeable rocks in sections of wells, constructing distribution maps for each of them, performing perforation of wells, while in producing wells, perforation is performed above the initial position of the oil-water contact (WOC), injection of water through injection wells, selection of formation fluids through production. In the process of developing the deposit, they control the movement of the oil and gas complex and, upon reaching the design degree of development of reserves in the flooded part of the reservoir, conduct insulation work in production wells [1].

The disadvantages of the method include:

- limited method area of use of deposits with bottom water;

the method does not include measures that ensure premature breakthrough of injected water in the most permeable layers, which can be located both in the upper part of the reservoir, and in the middle or lower, which leads to unpredictability of the nature of the flooding of the productive thickness of the reservoir (uneven coverage of the reservoir by flooding), as a result Why in the flooded part of the reservoir oil pillars (stagnant zones) are formed.

This leads to a decrease in the anhydrous period of oil production, the values of the current and marginal oil recovery coefficients due to the fact that oil in local domed uplifts cannot be extracted except by drilling additional production wells.

There is a method of developing an oil reservoir, which involves drilling the reservoir with producing and injection wells, developing the reservoir in two stages, injecting water through the injection wells and selecting fluids through the producing wells, and at the first stage, the cover of the producing reservoir is opened with a perforation interval equal to half the thickness of the reservoir, at the second stage, when bottom water reaches the producing wells in them, the formation is opened at full thickness [2].

The disadvantages of the method include:

- the limited use of the method for the development of oil fields with bottom water;

- conducting at the first stage of the development of deposits with bottom water perforation in production wells in the roofing of the formation in the range of 0.5 h, where h is the oil-saturated thickness of the formation, contributes to the formation of stagnant zones in the flooded part of the formation, which reduces the current oil recovery coefficient and the efficiency of the method development;

- anhydrous period insignificant in time due to the breakthrough of injected water in the most permeable interlayers, and the subsequent opening of the formation to the full thickness in the second stage leads to an increase in the rate of water cut in well production and thereby reduces the current and final oil recovery coefficients and reduces the development efficiency.

The objective of the invention is to expand the field of use of the method for the development of both pure oil fields and fields with bottom water using linear, block-closed and areal systems, increasing the anhydrous period of oil production, increasing the current oil recovery coefficient.

The solution to this problem is achieved by the fact that in the method of developing an oil reservoir, including drilling the reservoir with producing and injection wells, performing two stages of perforation of the reservoir in the producing wells, pumping water through the injection wells and taking oil through the producing wells, according to the invention in accordance with the grid placement of production wells determine the position of the bottom faces of production wells in the zone of local domed uplift or in the zone of the local depression if the bottom of the producing well falls into the zone of the local depression, the perforation of the producing well in the interval of the plantar of the productive layer is perforated, and when the bottom of the production of the well in the zone of the local domed rise is perforated of the producing well in the entire thickness range of the reservoir, the roofing part is perforated in the second stage reservoir in producing wells located in the zone of the local basin, when their water cut reaches 50% and higher, while in the producing x wells located in the local area of the dome lifting produce insulation of the bottom portion of the producing formation.

The essence of the method lies in the fact that the choice of perforation intervals in the producing wells during the formation of the water flooding system is carried out depending on the position of the faces of the producing wells on the structure so that the direction of the filtration flows of the injected water and the selected oil to the bottom of the producing wells helps optimize the effect of the gravitational component on the front of the injected water in the direction of filtration. This is achieved by accelerating the filling of the local cavity with injected water and the intensification of oil recovery by producing wells in the zone of dome uplift.

During the joint filtration of oil and injected water, the latter moves not only in the direction of filtration from the injection well to the producing one, but also falls down under the action of gravity. The front of displacement of the injected water is homogeneous and has a tendency to advance ahead to the bottom of the formation, which corresponds to the actually observed facts of the leading flooding of the bottom of the producing wells [3]. This feature of the filtration of injected water contributes to the creation of stagnant zones in the process of oil displacement by water. It follows that the injected water must be pulled from the sole of the producing well to its roofing part by directionally changing the filter flow, which is achieved by the appropriate choice of the perforation interval of the producing well.

At the same time, wells are placed on the structural map of the formation, which is platform-type deposits, either contact deposits with bottom water, or a combination of local dome rises and local depressions, which impose additional conditions on the filtering process of immiscible liquids of various densities.

The drawing shows a reservoir 1, represented by the alternation of zones of local dome raising 2 and local basin 3 with placed production wells 4 and injection wells 5, perforation intervals in the wells, isolation of the intervals acting by the forces of the filtration process: hydrodynamic force F in the direction of filtration from the injection wells to production and downward, gravitational force G. Injected water from the bottom of the injection well 5 and selected reservoir oil under the action of the resultant forces F and G are filtered in the space of the productive formation 1 as two immiscible liquids to the faces of the producing wells 4. In this case, due to the difference in the densities of the filtered phases, the injected water under the influence of gravitational force G drops down the section of the reservoir, contributing to phase separation along the section, due to which the flooding of producing wells goes from below. In this regard, the injected water should be pulled to the top of the reservoir as it is filtered. This is achieved by changing the direction of the filtration flows by selecting the intervals of perforation of the producing wells, taking into account their location at the bottom depth marks, which corresponds to the position of the producing well in the zone of the local dome uplift or local basin. In addition, as a result of the action of forces F and G, stagnant zones are formed near the faces of production wells due to the fact that their resulting filtration force is directed to the bottom of the formation.

The method is implemented as follows. In accordance with the grid location of production and injection wells determine the position of the bottom faces of production wells in the area of the local dome uplift or in the area of the local cavity. Then, at the first stage, perforation of production wells 4 located in the zone of local depressions 3 in the bottom of the formation is perforated, and perforation of production wells 4 in the zone of local domed rise 2 is performed over the entire thickness of the formation. In this case, the stagnant zone of the producing well is developed in the zone of the local depression, its bottom part and the partially stagnant zone near the injection well.

Thus, the first step of the method contributes to the pulling of the injected water to the sole of the producing wells located in the zone of the local depression, and thereby has an additional displacing effect by preventing the formation of a stagnant zone, and the filtration of the injected water to the producing wells in the zone of the dome uplift is inhibited and thereby creates conditions for leveling the front of the displacement of injected water in the bottom of the production well of the local dome uplift.

At the second stage, when the water cut of production reaches 50% or more in production wells located in the zone of the local basin, the roofing part of the reservoir is perforated, i.e. a full opening (extension) of the productive thickness of the formation is carried out, and in the producing wells in the zone of local domed rise, the sole part of the formation is isolated in a known manner.

At this stage, perforation throughout the entire thickness of the production well in the local cavity zone and isolation of the bottom of the production well in the local domed uplift create additional conditions for pulling the injected water upward, aligning the displacement front of the injected water as a whole along the reservoir section in the waterflood area.

Perforation of injection wells is carried out in accordance with the decisions of the project document during the formation of the water flooding system.

To develop stagnant zones of platform-type oil formations, steps 1 and 2 are alternated through one production well. In contact oil deposits with bottom water, before steps 1 and 2, the bottom water is isolated by the inverse cone of the reservoir oil. When using the method in the fields at the final stage of development, in order to increase the oil recovery coefficient, steps 1 and 2 are implemented in combination with the isolation measures of the waterflood intervals using forced fluid withdrawal.

A specific example of execution.

The method is implemented in the Severo-Pyamaliyakhskoye field, located in the Purovsky district of the Yamalo-Nenets Autonomous District of the Tyumen Region. The field is characterized by the presence of local depressions concentrated to the center of the reservoir and local dome rises located towards the boundaries of the reservoir. Industrial oil related to EC strata $\genfrac{}{}{0ex}{}{\text{1}}{\text{10}}$ and BS ₁₁ .

Drilling of BS operating facilities $\genfrac{}{}{0ex}{}{\text{1}}{\text{10}}$ and BS _{11 is} carried out on triangular grids offset from each other, with a distance between the wells of 500 × 500 m, all wells are drilled with the opening of the BS ₁₁ formation.

In accordance with the drilling pattern at the BS ₁₁ and BS development sites $\genfrac{}{}{0ex}{}{\text{1}}{\text{10}}$ Six wells were identified, including four production wells No. 533, 157, 514, 140 located in the zone of local domed lifting with roof depth marks ranging from 2672-2691 m, and two production wells No. 522, 536, located in the zone of the local depression with depth marks on the roof ranging from 2658-2662 m.The perforation of the four production wells was made over the entire productive thickness of the reservoir, and two production wells located in the zone of the local cavity were perforated in the bottom of the formation. Wells put into operation. Upon reaching 50% water cut in production wells Nos. 522, 536 located in the local cavity, extension was completed (perforation of the roofing of the productive formation was carried out), and isolation was carried out in production wells No. 533, 157, 514, 140 of the bottom of the productive formation . Wells have been operating for more than two years. During this time, the period of waterless operation in wells located in the zone of local dome rises, taking into account the isolation, increased by 85-115 days. For wells located in the zone of the local depression, the additional anhydrous period averaged 45 days. At the same time, when drilling through wells No. 522, 536, a decrease in water cut was observed from 60% to 15% with a subsequent increase in the water cut rate of no more than 7% per year. Over the observed period of well operation, the additional oil production per well averaged 3,777 tons, and the additional production in six wells as a whole amounted to 22,663 tons, which made it possible to increase the current oil recovery coefficient in comparison with the average current oil recovery coefficient by 0.12%.

The effect of the application of the proposed method is achieved by increasing the anhydrous period of oil production and increasing the current coefficient of oil recovery.

Sources of information

1. A.S. USSR No. 1719621, E 21 B 43/20, 1992.

2. A.S. USSR No. 1811244, Е 21 В 43/20, 1990 - prototype.

3. Mulyavin S.F., Medvedsky R.I. and others. A method for predicting oil and water production, taking into account their gravitational separation when moving along the reservoir. // Oil and gas No. 3, Tyumen, 1999, p. 30-36.

Claims (1)

The method of developing an oil reservoir, including drilling a reservoir with producing and injection wells, performing perforation of the reservoir in producing wells in two stages, pumping water through injection wells and taking oil through production wells, characterized in that according to the grid of the location of the producing wells, the bottom position is determined production wells in the zone of the local dome uplift or in the zone of the local depression, and at the first stage when the bottom of the production well falls into the perforation of the production well in the interval of the bottom of the productive formation, and when the bottom of the production well falls into the zone of local domed lifting, perforation of the production well is made in the entire interval of the thickness of the productive layer, at the second stage, perforation of the roofing of the productive formation is performed in production wells located in zone of the local basin, when their water cut reaches 50% and higher, while in producing wells located in the zone of the local dome th raising produce insulation of the bottom portion of the producing formation.

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