RU2238399C1 - Method for extracting of oil deposit - Google Patents

Abstract

FIELD: oil extractive industry.

SUBSTANCE: method includes drilling product and force wells, extracting oil from product wells and pumping displacing agent into force wells, which agent consists of two portions - gas and water. Pumping of gas is performed with face pressure of force wells equal to or higher than pressure of mixing of gas and oil, but lower than pressure of hydraulic disruption of beds, and face pressure of force wells is kept equal or higher than pressure needed for saturation of oil with gas, and gas for pumping into oil deposit is taken from adjacent gas deposit, additionally increasing its pressure in 4-5 times by means of 1-2 step compressor, while within oil area bed pressure is formed to be higher than firsthand, and said oil area is screened from surrounding area by horizontal extracting wells, said surrounding area having bed pressure lower or equal to firsthand pressure. Deposit is screened from surrounding area with low bed pressure by horizontal extracting wells. Within deposit bed pressure is higher than firsthand pressure. Pumping of gas is performed with pit pressure of force wells equal to or higher than pressure needed for mixing of gas and oil, but lower than pressure needed for hydraulic disruption of beds. Pit pressure of extracting wells is kept equal to or greater than pressure needed for saturation of oil with gas.

EFFECT: higher oil yield.

2 cl, 1 ex

Description

The invention relates to the oil industry, specifically to the development of oil deposits with in-line injection of a displacing agent, especially with low and low initial oil saturation of the reservoirs, respectively, with a low coefficient of oil displacement by pumped water.

A known method of developing an oil field, including drilling production and injection wells, oil selection from production wells and pumping water into injection wells. The disadvantage of this method is that the displacement coefficient is significantly lower than the potential, equal to 100%, and with low and low initial oil saturation of the formations less than 50%. Note that in Western Siberia there are a lot of such deposits with low and low oil saturation.

There is another method for developing an oil reservoir using high pressure gas as a displacing agent. The disadvantage of this method is the high mobility of the gas, which in reservoir conditions is 100 or more times higher than the mobility of oil. For this reason, production wells have to be shut down shortly after a gas breakthrough, and the coefficient of reservoir coverage by displacement is low, for example, equal to 20-30%. Therefore, even with a high displacement ratio of 100%, oil recovery is low, at the level of 20-30%.

There is a known desire to combine the advantages of gas and water injection and eliminate their disadvantages: first, high pressure gas is pumped into oil reservoirs and a high displacement coefficient is provided; and then pump water and provide a sufficiently high coefficient of coverage of formations by displacement; as a result, compared with the two previous methods, significantly increase oil recovery.

This idea was implemented in a known method for the development of oil deposits [1]. But this method requires too much high-pressure gas to create a wide gas rim that does not allow direct contact of the injected water and the displaced oil. In this case, the injected water instead of oil buries gas, gradually reducing the width of the gas rim. Therefore, so that, despite the reduction, the separating gas rim remains until the end of the oil extraction, a lot of gas must be pumped before the water is pumped.

The same idea is implemented in the known method of developing an oil reservoir [2]. But in this method, in order to reduce the idle pumping of high-pressure gas, after reaching a predetermined limit gas factor, for example 1000 n.m ^{3 of} gas per 1 ton of oil through the surrounding production wells, injection wells are transferred to water injection and the subsequent alternation of water and gas injection. The advantage of this known method [2] compared with the previous known method [1] is a significant reduction in the total flow rate of high pressure gas. Accordingly, in increasing the possibility of wider application of the idea of sequential injection of gas and water.

The known method [2] adopted by us as a prototype. The disadvantage of the prototype is a possible insufficient or excessive increase in bottomhole pressure of injection wells, insufficient or excessive decrease in bottomhole pressure of production wells.

Excessive increase in bottomhole pressure of injection wells leads to hydraulic fracturing and premature breakthrough of high pressure gas into the surrounding production wells.

An excessive decrease in the bottomhole pressure of producing wells leads to a noticeable or significant decrease in their oil productivity coefficient.

Something like this and another leads to a noticeable or significant decrease in oil production and oil recovery.

The objective of the invention is to increase oil recovery.

This problem is solved by the fact that gas is injected at bottomhole pressure of injection wells equal to or higher than the gas and oil miscibility, but lower than the hydraulic fracturing pressure, while the bottomhole pressure of production wells is kept equal to or higher than the gas saturation pressure of oil. Gas for injection into an oil reservoir is taken from a neighboring gas reservoir, further increasing its pressure by 4-5 times with a 1-2-stage compressor, while reservoir pressure is created above the initial one within the oil area, and this oil area is shielded by horizontal producing wells from the surrounding area with reservoir pressure equal to or lower than the original. This removes the technically and economically difficult problem of increasing the pressure of the injected gas from 1 atm to 300-400 atm and above with the help of expensive multi-stage compressors. Requirement for used 1-2-stage compressors: they must withstand high gas pressure of 300-400 atm and more. The gas injection pressure is higher than the gas-oil miscibility pressure, but lower than the hydraulic fracturing pressure of the oil reservoirs. The bottomhole pressure of the producing wells is as low as possible, but higher than the pressure of oil saturation with gas, so that there is no degassing of oil, precipitation of solid asphalt-resin-paraffin particles from the oil, their accumulation in the near-well zones of oil reservoirs and, as a result, a decrease in the productivity of oil wells. A significant increase in reservoir pressure against the initial value can dramatically increase the depression in oil reservoirs and, accordingly, increase the oil production rate of producing wells, but it is necessary that there is no outflow of oil and loss of part of the oil reserves in the aquifer. To do this, horizontal wells with a strong shielding property are located on the border of the considered part (separate area) of the oil reservoir, which shield the oil area with high reservoir pressure from neighboring oil and water areas with an initial and lower reservoir pressure.

Here is an example of the implementation of this method of developing oil deposits.

The productivity of oil reservoirs is characterized by the average coefficient of well productivity equal to η = 0.3 t / (day at.) Or in volume units of 0.4 m ³ / (day at.). The ratio of the displacements of the displacing water and oil under reservoir conditions is μ * = 2. The depth of oil reservoirs is 2500 m. The initial reservoir pressure is equal to hydrostatic, i.e. equal to 250 at. The pressure of oil saturation with gas is 100 at. Bottom-hole pressure of producing wells is equal to the saturation pressure P _c = 100 at. The miscibility pressure of gas and oil is 400 at. The hydraulic fracturing pressure of oil reservoirs is 600 at. Accepted bottomhole pressure of injection wells is equal to R _sn = 500 at. The density of the gas used in the adjacent gas deposits is 0.7 kg / m ³ . The gas pressure at the inlet to the compressor is 100 at. The gas pressure at the outlet should be 400 bar. The number of producing wells surrounding the injection is m = 4.

When water is pumped into oil reservoirs, the oil production rate per 1 production well is

while reservoir pressure is

which is less than the initial reservoir pressure equal to 250 atm; therefore there is no threat of outflow and loss of part of the recoverable oil reserves.

т.е. по обычной технологии дебит нефти добывающей скважины равен

при этом пластовое давление равно

что тоже меньше начального пластового давления 217 ат <250 ат.With conventional standard technology, the bottomhole pressures of injection and production wells are 350 at and 150 at. According to this method of developing an oil reservoir, compared with conventional technology, the production rate of oil from a producing well is

those. according to conventional technology, the oil production rate of an producing well is

while reservoir pressure is

which is also less than the initial reservoir pressure of 217 at <250 at.

During gas injection and subsequent gas and water injection, the oil production rate per 1 production well will be

moreover, in the last formula in the numerator 75 at represents the increase in bottomhole pressure of the injection well due to the weight of the gas column minus the loss of friction pressure.

In this case, the reservoir pressure is equal to

which is significantly greater than the initial reservoir pressure equal to 250 at.

Next, we replace the vertical production wells with horizontal production wells, so that the reservoir pressure is equal to the initial value

раза, что достигается за счет горизонтальной длины скважины.this yields z = 4.167, i.e. the productivity coefficient of a horizontal well should be higher than that of a vertical well, in

times, which is achieved due to the horizontal length of the well.

Then the oil flow rate per 1 horizontal production well will be

раза.which further increased oil production in

times.

раза увеличивает дебит нефти добывающих скважин, в 2 раза увеличивает коэффициент вытеснения с 50% до 100%, соответственно в 2 раза увеличивает коэффициент нефтеотдачи пластов и извлекаемые запасы нефти.Thus, the implementation of this method of developing an oil reservoir in

times increases the oil production rate of producing wells, 2 times increases the displacement factor from 50% to 100%, respectively, 2 times increases the oil recovery coefficient and recoverable oil reserves.

Sources of information

1. Baturin Yu.E., Efremov EP, Lysenko V.D., Righteous N.K. The way to develop oil deposits. - Invention, copyright certificate No. 495927.

2. Lysenko V.D., Graifer V.I. A method of developing an oil reservoir. - Patent of the Russian Federation No. 2142045.

Claims (2)

1. A method of developing an oil deposit, including drilling production and injection wells, taking oil from production wells and injecting into the injection wells a displacing agent consisting of two parts - gas and water, characterized in that the oil reservoir is screened from the surrounding area with low reservoir pressure horizontal production wells, within the reservoir create a reservoir pressure above the original, and gas is injected at bottomhole pressure of injection wells equal to or higher than the pressure oil and gas, but below the fracturing pressure, while the bottomhole pressure producing wells kept equal to or higher than the saturation pressure of the gas oil. 2. The method according to p. 1, characterized in that the gas for injection into the oil reservoir is taken from a neighboring gas reservoir, further increasing its pressure by 4-5 times using a 1-2-stage compressor.