RU2085712C1 - Method for development of oil and gas deposit and oil fringe - Google Patents

Abstract

FIELD: oil and gas production industry. SUBSTANCE: method allows for higher efficient action of displacing agents injected into reservoir such as water and gas due to prevention of outbursts of gas and water in vertical direction in zone adjacent to well. Maintaining at well head of water-gas injection well of water pressure value determined according to formula given in description ensures delivery of displacing agents in design quantities and in given intervals: water - into upper gas-saturated part, and gas - into lower oil-saturated part of reservoir. Regulation of water and gas injection process is effected with use of pressure gauges installed at head of water-gas injection well. EFFECT: high efficiency. 1 dwg

Description

 The invention relates to the oil and gas industry and can be used in the development of oil and gas deposits and oil rims.

 A well-known technology for the development of an oil reservoir (USSR patent N 1243632, class E 21 B 43/18, 07/07/86), in accordance with which a mixture of hydrocarbon gases is injected into the oil reservoir at the first stage, and water at the second stage; injection of a mixture of hydrocarbon gases is carried out in a volume of up to half the pore volume of the oil reservoir; a mixture of hydrocarbon gases is injected into the water-saturated zone through the edge (or side) injection wells, and water is pumped into the gas-oil zone.

 The disadvantage of this technology is the need to have separate grids of injection gas and water wells located over the entire area, which complicates their operation, while it is significantly more expensive to equip the injection system of displacing agents into the formation.

 A well-known technology for the development of oil and gas fields using gas from a gas reservoir by transferring gas to the oil reservoir according to the downhole scheme or by mixing gas with a stream of water on the surface and pumping a gas-gas mixture through the annulus into overlying oil horizons (Ostrovsky Yu.M. Faniev R .D. Yaniev VE Some issues of technology and techniques of gas-water repression on oil reservoirs, collection of oil fields, Proceedings of the Institute of the Oil Industry, UkrNIIIPND, M. 1973, issue XI X II, p. 212 216).

 The disadvantage of this technology is that the displacing agent (gas, water) is bypassed or injected only at one of the intervals in the formation; however, the analyzed technology does not allow the simultaneous supply of various displacing agents in two isolated intervals, which is required when developing gas-oil deposits and oil rims.

 A known method of developing an oil reservoir (US patent N 4427067, class E 21 B 43/16, 01.24.84) prototype, in accordance with which the injection of water and gas is carried out jointly-separately through the same well (two parallel columns of elevator pipes ), in two different intervals of the formation, with gas being supplied to the lower, flooded part of the formation, and water to the upper, oil-saturated part of the formation; in the near-wellbore zone and at a certain distance from the well in the formation, a zone filled with a water-gas mixture is formed, and when it is advanced through the formation, an increase in the oil recovery coefficient is provided.

 The disadvantage of this method is that the vertical coordinate of the gas-water interface in the wellbore, depending on the pressure ratios of the water and gas flows at the outlet of the elevator pipes, can vary within wide limits (due to the pressure at the wellhead and flow rate of the media to be completed). At the same time, at the bottom (in the wellbore), gas can break into the oil-saturated part of the formation, it is also possible that large quantities of water can enter the water-saturated part. The effectiveness of the impact on the reservoir is therefore reduced, because the width of the two-phase flow zone narrows. In addition, it is possible for gas to slip into the bedside, and water at the bottom intervals of the formation in the bottomhole formation zone directly at the walls of the well.

 All this reduces the efficiency of technology application (according to the prototype) in the development of oil and gas deposits or subgas oil rims.

 The aim of the invention is to increase the efficiency of oil recovery while simultaneously injecting water and gas into the formation due to the more complete use of these agents to displace hydrocarbons from the formation.

где

P_уг давление газа на устье скважины в колонне лифтовых труб, Па;
g ускорение силы тяжести, м/с²;
ρ_г.ст плотность газа при стандартных условиях, кг/м³;
ρ_в плотность воды, кг/м³;
T_ст температура при стандартных условиях, град. К;
P_ст давление при стандартных условиях, Па;
H глубина установки пакера, м;
T средняя температура по стволу скважины, град. К;
Z среднее значение коэффициента сверхсжимаемости по стволу скважины, безразм.According to the invention, while simultaneously injecting gas and water into the formation through an injection well: gas into the lower oil-saturated part of the formation, and water into the upper gas-saturated part of the formation, the pressure of the injected water at the mouth of the injection well (P _uv ) is maintained in accordance with the expression:

Where

P _yr gas pressure at the wellhead in the tubing string, Pa;
g acceleration of gravity, m / s ² ;
ρ _g.st. gas density under standard conditions, kg / m ³ ;
ρ _{in the} density of water, kg / m ³ ;
T _article temperature under standard conditions, deg. TO;
P _article pressure under standard conditions, Pa;
H packer installation depth, m;
T is the average temperature along the wellbore, deg. TO;
Z is the average value of the coefficient of supercompressibility along the wellbore, dimensionless.

λ _g coefficient of hydraulic resistance during gas movement along the column of elevator pipes, dimensionless.

λ _{in the} coefficient of hydraulic resistance of the channel through which water moves, dimensionless.

d _{1 the} inner diameter of the column of elevator pipes through which the gas moves, m;
F _in the living section of the channel along which the water moves, m ² ;
D _{in the} hydraulic diameter of this channel, m;
Q _g gas consumption under standard conditions, m ³ / s;
Q _{in the} flow rate of water, m ³ / s.

 Under the conditions defined by expression (1), breakthroughs of gas up and water down in the near-well zone are excluded. Due to this, the radius of the zone covered by water entering the upper gas saturated interval of the formation and by gas entering the lower oil saturated interval of the formation increases, the gas injected into the oil part of the formation is more fully used to displace oil; at a greater distance from the well, mixing occurs due to the gravitational forces of the injected water and gas. Due to this, the rim of the water-gas mixture of larger sizes is created in the oil part of the reservoir than by the technology described in the prototype, as a result of which the area covered by the displacement of oil by the water-gas mixture increases.

The proposed solution provides the ability to pump gas into the oil-saturated part of the reservoir, and pump water into the gas-saturated part of the reservoir. This is achieved by maintaining pressure at the wellhead in the annulus in accordance with formula (1), ensuring equal pressure at the bottom of the well:
P _hg P _z.v. P _s (2)
where P _zg the pressure at the outlet of the column of elevator pipes through which the gas moves, Pa;
P _z.v. the pressure at the outlet of the channel through which the water moves, Pa.

Сведения, подтверждающие возможность осуществления способа.In this case, the values of P _z.g. entering expression (2) and P _z.v. determined by the formulas:

Information confirming the possibility of implementing the method.

 The scheme of the method is presented in the drawing.

 A column of elevator pipes 2 with a packer 3 installed at the depth of the gas-oil contact (N) was lowered into the injection well 1. At the mouth of the injection well, a fountain valve 4 is mounted on which pressure gauges 5 and 6 are installed. The annulus 7 of the injection well is connected via a pipe 8 to a high pressure water source 9 and a pipe string 2 through a pipe 10 is connected by a pipe 11 to a high pressure gas source ; the production well 12 is equipped with a column of elevator pipes 13 with a packer 14 installed below the gas-oil contact.

 The method is as follows.

где a, b коэффициенты фильтрационного сопротивления при нагнетании газа в нефтенасыщенную часть пласта, (размерность соответственно

);
η коэффициент приемистости при нагнетании воды в газонасыщенную часть пласта, м³/Па;
P_п, P_з соответственно пластовое и забойное давление (на глубине установки пакера), Па;
Q_г, Q_в соответственно расходы газа и воды, м³/с.Industrial water and gas are supplied to the injection well, which has opened the gas cap and the oil-saturated part of the oil and gas reservoir, from high pressure sources (pump and compressor stations), and water is pumped through the annulus 7 into the upper (gas-saturated) part of the formation, and gas through the column of elevator pipes 2 to the lower, oil-saturated part of the reservoir. The pressure at the bottom of the well (P _s ) is set and, with known values of the reservoir pressure (P _p ) and the filtration resistance coefficients in the reservoir (or injectivity coefficient), the gas and water flows are calculated by the formulas:

where a, b are the filtration resistance coefficients when gas is injected into the oil-saturated part of the reservoir, (dimension, respectively

);
η coefficient of injectivity when injecting water into the gas-saturated part of the reservoir, m ³ / Pa;
P _p , P _s, respectively, reservoir and bottomhole pressure (at the depth of installation of the packer), Pa;
Q _g , Q _in, respectively, the costs of gas and water, m ³ / s.

Величина давления воды на устье скважины определяется по формуле (1).The required gas pressure at the wellhead is calculated by the formula:

The magnitude of the water pressure at the wellhead is determined by the formula (1).

The values _in Q, Q _z, P _y and P _uv periodically as P _n values change, the coefficients a, b are adjusted.

Maintaining the ratio between the values P and P _{uv y,} computed according to the formulas (1) and (7) allows to provide injection at predetermined intervals the water reservoir and the gas with minimal their vertical cross-flows downhole in the vicinity.

 Mixing water with gas in the reservoir will occur at some distance from the well (due to gravitational redistribution of phases, gas bubbles acquire a downward velocity vector of filtration). In this case, the rim formed by mixing gas and liquid will consist of: in the upper part of the reservoir from a water-gas mixture (B + G), and in the lower part of the reservoir from a water-gas-oil mixture: some of the gas can be dissolved in oil near the injection well, and further from the well, this gas will be partially released.

 The oil displaced by the water-gas and water-gas-oil mixture moves through the reservoir and enters production wells 12 into which the elevator pipes 13 are lowered with a packer 14 installed below the current gas-oil contact; the annulus in the production wells above the packer is filled with liquid to prevent gas breakthroughs (the production string in the interval above the packer installation site is not perforated).

 The selection of oil through production wells can be performed continuously at a given annular pressure, or periodically.

 An example implementation of the method.

 The productive oil and gas reservoir lies at a depth of 3850 m. The thickness of the reservoir is h 200 m.

Коэффициенты A, B, C в формуле (1) равны:
A 83,8•10^-6м^-1;
B 5,86•10⁸кг²м^-9с^-2;
C 7,54•10⁹кг•м^-7.The water-gas injection well is cased with pipes with an inner diameter of D ₁ 0.15 m; A tubing with an inner diameter of d ₁ 0.073 m and an outer diameter of d ₂ 0.089 m was lowered into the well. A packer was installed on the tubing string at a depth of H 4000 m, separating the upper, gas-saturated interval of the formation from the lower, oil-saturated. Gas is pumped through the tubing string into the lower oil-saturated interval with a flow rate of Q _{g of} 800 thousand m ³ / day, 9.259 m ³ / s, and water is pumped through the annulus into the upper gas-saturated interval of the formation with a flow rate of Q _of 1000 m ³ / day 1,157 • 10 ^{- 2} m ^{3 /} s.2 Formation pressure P _p 50 • 10 ⁶ Pa. The coefficient of water injectivity of the upper (above-packer interval) η 100 m ³ / (days. MPa), the coefficients of filtration resistance during gas movement in the lower (under-packer interval)

The coefficients A, B, C in the formula (1) are equal to:
A 83.8 x 10 ^-6 m ^-1 ;
B 5.86 • 10 ⁸ kg ² m ^-9 s ^-2 ;
C 7.54 • 10 ⁹ kg • m ^-7 .

The gas pressure at the mouth of the injection well P _yr (in the tubing string) is 46.2 • 10 ⁶ Pa.

При работе водо-газовой нагнетательной скважины с технологическими параметрами: Q_г 800 тыс.м³/сут; Q_в 1000 м³/сут; P_уг 46,2 МПа, P_ув 21,76 Мпа, на забое скважины (на глубине H 4000 м) создается давление P_з, равное 60 МПа, и обеспечивается поступление с заданным расходом воды и газа в определенные интервалы, а именно: воды в верхнюю газонасыщенную, а газа в нижнюю, нефтенасыщенную часть пласта, при этом предотвращаются прорывы вблизи от данной скважины газа в верхний, а воды в нижний интервалы.The required value of the water pressure at the mouth of the injection well is calculated by the formula (1):

When operating a water-gas injection well with technological parameters: Q _g 800 thousand m ³ / day; Q _in 1000 m ³ / day; P _ug 46.2 MPa, P _uv 21.76 MPa, at the bottom of the well (at a depth of H 4000 m), a pressure P _s equal to 60 MPa is created, and water is supplied with a given flow rate at certain intervals, namely: water in the upper gas-saturated, and gas in the lower, oil-saturated part of the formation, while breakthroughs in the vicinity of the given gas well to the upper and water to the lower intervals are prevented.

Claims (1)

A method for developing an oil and gas reservoir and an oil rim, comprising simultaneously simultaneously injecting gas and water through a gas and water injection well at different intervals of the producing formation and taking hydrocarbon products through a production well, characterized in that the pressure of the injected water at the mouth of the gas-water injection well R _{u c is} maintained in according to the expression

+ CQ $\genfrac{}{}{0ex}{}{\text{2}}{\text{in}}$ -gρ _in H,
Where

R _{y g} the gas pressure at the wellhead in the column of elevator pipes, Pa;
g acceleration of gravity, m / s ² ;
ρ _g.st - gas density under standard conditions, kg / m ³ ;
T _{c t} temperature under standard conditions, deg. TO;
N depth of installation of the packer, m;
T is the average temperature along the wellbore, deg. TO;
Z is the average value of the coefficient of supercompressibility along the wellbore, dimensionless. λ _in - coefficient of hydraulic resistance of the channel through which water moves, dimensionless. ρ _in - the density of water, kg / m ³ ;
λ _g - coefficient of hydraulic resistance during gas movement along the column of elevator pipes, dimensionless. d _{1 the} inner diameter of the column of elevator pipes through which the gas moves, m;
F _in the living section of the channel along which the water moves, m ² ;
D _{in the} hydraulic diameter of the channel through which the water moves, m;
Q _g gas consumption under standard conditions, m ³ / s;
Q _{in the} flow rate of water, m ³ / s;
π = 3,14.t