RU2357075C1 - Method of development of hydrocarbon field - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention refers to oil producing industry, particularly to methods of development of hydrocarbon fields. The essence of the invention is as follows: the method consists in boring out the field with vertical producing and pressure wells through the whole drill core, in pumping water via pressure and in withdrawing oil via producing wells. According to the invention the field is additionally bored out with the horizontal well stretched between the producing and pressure wells; this horizontal well is located in the low permeable interlayer closer to an upper boundary. Development of the field is carried out in stages. At the first stage only lower high permeable part of the horizon is struck in water pressurising wells; then water is pumped into this part, while the upper low permeable part of the horizon is struck in producing wells through which oil is withdrawn. Pumping-withdrawing is carried out till complete water flood of high permeable part of the continuous water surface. Further the second stage of development is commenced, whereat the horizontal wells are subject to oil withdrawing; while pumping water into high permeable part of the horizon is continued. Also producing wells are shut down for oil withdrawing and are struck in the lower high permeable part for pumping water through it.

EFFECT: increased efficiency of the method when it is implemented at layered non-uniform horizons with low permeable interlayer in an upper part and high permeable interlayer in a lower part owing to intensified oil extraction from high permeable interlayer.

3 cl, 1 dwg

Description

The invention relates to the oil and gas industry, in particular to methods for developing hydrocarbon deposits.

A known method of developing a hydrocarbon reservoir, including drilling the reservoir by injection and producing wells, pumping water through injection and oil production through the producing / 1 /.

The disadvantage of this method is the low coefficient of oil recovery, since the method does not provide measures to reduce residual cohesion.

Closest to the proposed is the selected as a prototype method for developing a hydrocarbon reservoir, including drilling the reservoir with injection and producing wells, pumping water through injection and oil production through producing / 2 /.

The disadvantage of this method is that in a layered heterogeneous formation, when the upper part of the formation has the worst filtration-capacitive characteristics compared to the lower one, the residual pillar of oil remains in it, the production of which occurs extremely slowly and at high water cut of the produced products. This is confirmed by the experiment results set earlier / 3, 4 / and given in the application materials.

The aim of the invention is to increase the efficiency of the method when it is implemented on layered heterogeneous formations with a low permeability layer in the upper part and highly permeable in the lower. The goal is achieved through the intensification of oil production from the low permeability layer.

The implementation of the method is clarified in the drawing. The deposit is drilled with injection 1 and producing 2 and horizontal 3 wells. Injection wells 1 are opened by perforation 4 in the highly permeable part 5 of the formation, and production wells 2 with perforation 6 in the low-permeability part 7 of the formation. Thus, water is pumped at intervals of 4, and oil is taken at intervals of 6. This technology ensures, as can be seen from the observations in / 3, 4 /, which are given in the application materials, the formation of a continuous water mirror 8 along the horizontal oil contact -water "by bedding.

In turn, the formation of a continuous water mirror along the horizontal oil-water contact in the future, with subvertical displacement of oil by water, ensures the achievement of the maximum coverage coefficient. To realize this positive dynamics, at the second stage of development, horizontal wells 3 are put into operation for oil, and in the production wells 2, the highly permeable part 5 of the formation is opened by perforation 9 and water is pumped through it, and oil withdrawal at intervals 6 is stopped. Moreover, through injection wells 1, water is continued to be pumped into the highly permeable part 5 of the formation through the perforation interval 4.

The amount of depression on a horizontal well is determined from the expression:

P _PL -P _c ≤γ _n · h _N ,

where (R _pl -R _s ) - depression, Pa,

P _PL - reservoir pressure, PA,

P _s - pressure on a horizontal well, Pa,

γ _n - specific gravity of oil, n / m ³ ,

h _N - average thickness of the oil-saturated zone, m

Setting the magnitude of depression from this expression allows you to exclude local breakthroughs of water to the opening interval of the producing horizontal well 3.

The result is a stable subvertical displacement of oil by water. The advanced flooding of the low-permeability part with injection and withdrawal through vertical wells eliminates the need to drill additional horizontal wells to flood the lower highly permeable part of the reservoir.

A common oil and gas production practice is to drill horizontal wells in both the lower and upper parts of the reservoir, flooding the lower part and taking oil from the top. In the proposed technical solution, advanced flooding is carried out through vertical wells in the lower highly permeable part of the reservoir, which will reduce the energy costs of equipping the reservoir by eliminating the cost of capital construction of additional horizontal wells.

Water injection through injection wells 1 into the lower highly permeable part of the reservoir and oil extraction through wells 2 - from the upper one provides advanced flooding of the first, accelerates the transition to the stage of vertical oil displacement and thereby reduces the development time of the reservoir. The placement of the opening intervals 6 of producing wells 2 initially in the low-permeable part 7 in addition to the above ensures the prevention of the formation of an inverse oil-to-water cone on the production line, rather than if oil were taken through the wells 2 (in order to accelerate the formation of continuous water mirror) would be produced from the lower highly permeable part of the reservoir.

Two-sided flooding of the lower highly permeable part of the formation through wells 1 and 2 in the second stage with simultaneous selection of formation fluids along the entire length of the horizontal well ensures uniform raising of the water-oil contact and reduces the possibility of local breakthroughs of water to the sampling interval. This also contributes to the direction of displacement vertically upward along the entire length of the formation.

The above allows us to conclude that the claimed technical solution meets the criterion of "significant differences".

Equally important is the moment of transition from the first stage of development to the second, which is determined as follows.

Obviously, to ensure stable operational performance of a horizontal well, it is necessary to have the characteristics of the drained zone that would not change during the development of the reservoir. In the case of the implementation of the proposed method, when crossing the oil-water contact, the boundaries of the interbeds of various permeabilities might necessitate a change in the operational mode of the horizontal well. To eliminate such a need, horizontal wells are put into operation after the oil-water contact passes through the boundaries of different layers.

As an example of the implementation of the method, a development element with the following initial data is given:

element length (distance between injection and producing wells = 500 m;

width a = 300 m;

the thickness of the low permeability part h ₁ = 10 m;

highly permeable h ₂ = 10 m;

porosity of the first m ₁ = 0.10;

the second m ₂ = 0.30;

injectivity of the injection well Q = 100 t / day;

the density of oil and water, respectively, ρ _n = 0.8 g / cm ² and ρ _in = 1.0 g / cm ² ;

oil recovery factor CIN = 0.5.

Then recoverable reserves from the low permeability part

Q ₁ = ρ _n · a · in · m ₁ · h ₁ · CIN = 300 · 500 · 0.1 · 10 · 0.5 · 0.8 = 0.6 · 10 ⁵ m

From highly permeable part

Q ₂ = ρ · a · in · m _{2 •} h ₂ · CIN = 300 · 500 · 0.3 · 10 · 0.5 · 10 · 0.8 = 1.8 · 10 ⁵ m, and

Flooding of the bottom will occur in time

After this time, the second stage of development begins.

The pick-up of production wells 2, which are opened in the second stage in the lower highly permeable part, is taken as for wells 1 Q _ng = 100 t / day, then the development time of the low-permeability upper interlayer:

Depression on a horizontal production well:

(P _pl -P _c ) ≤0.8 · 10 ⁴ n / m ³ · 10 m = 0.8 · 10 ⁵ Pa.

LITERATURE

1. Korshak A.A. et al. Fundamentals of Oil and Gas Business, Ufa, Designpolygraphgraphis, 2002, p. 155.

2. Pavlenko V.P. Exploitation of oil deposits. M., 2003, p.28 (prototype).

3. Umariev TM Study of the structure of reservoir oil losses in a stratified inhomogeneous reservoir. Collection "Oilfield business." M., VNIIOENT, 1992

4. Enikeev V.R. Analysis of the development of Devonian deposits of the Tuymazinsky field. Overview information. Series: “Oilfield Business”, issue 18 (107), M., 1985, p. 53.

Claims (3)

1. A method of developing a hydrocarbon reservoir with an upper low permeable and lower highly permeable layers, comprising drilling a reservoir throughout the section with vertical production and injection wells, pumping water through injection wells and taking oil through production wells, characterized in that the reservoir is additionally drilled with a horizontal well extended between the production and injection wells, which are placed in a low-permeability interlayer closer to the roof, and the development of the deposit is carried out in stages, while at the first only in the water injection wells open the lower highly permeable part of the formation, into which water is pumped, and in the production wells - the upper low-permeability, through which oil is sampled, and the selection is made until the highly permeable part of the solid water mirror is completely flooded, after which they proceed to the second stage development, in which horizontal wells are put into operation for oil and continue to pump water into the highly permeable part of the reservoir, while production wells cease to operate rub on oil and open them in the lower highly permeable part, through which water injection begins. 2. The method of developing a hydrocarbon deposit according to claim 1, characterized in that the time section between the first and second stages with the formation of a water mirror is considered to be the moment of movement of the continuous oil-water contact above the interface between the low and high permeability layers. 3. The method of developing a hydrocarbon reservoir according to claim 1, characterized in that the amount of depression in a horizontal well is set from the expression
P _pl -P _with ≤γ _n · h _H
where (R _PL -R _s ) - the value of depression, PA;
P _PL - reservoir pressure, Pa;
P _with - pressure on a horizontal well, Pa;
γ _n - specific gravity of oil, n / m;
h _H is the average oil-saturated layer thickness, m