RU2813421C1 - Method for development of low-permeability oil deposit - Google Patents

Abstract

FIELD: oil, gas and coke-chemical industry.

SUBSTANCE: method for development of low-permeability oil deposit includes oil production with norm of fluid withdrawal from production well. Preliminary on production wells depth samples are taken; formation pressure, pressure of oil saturation with dissolved gas, content of dissolved gas and amount of released gas at differential degassing at each pressure stage are determined. Further, a linear graph of the dependence of the amount of released gas on the degassing pressure is plotted; the point of the fracture pressure value with a sharp increase in the release of dissolved gas is determined. After that, hydrodynamic investigations are performed in production wells, dynamic level of liquid and bottomhole pressure are determined. Production well is stopped with bottomhole pressure equal to or lower than oil saturation pressure with dissolved gas, liquid level recovery in the production well shaft is measured in real time, a liquid level recovery curve is plotted, the skin factor and productivity factor are determined. A production well with a skin factor less than zero is selected, the well flow rate is determined and brought into operation, oil production is carried out with a liquid withdrawal rate.

EFFECT: high efficiency of developing low-permeability reservoirs and maintaining high rates of extraction of oil reserves.

1 cl, 1 tbl

Description

The invention relates to the field of development of oil fields with low-permeability reservoirs and helps to increase the efficiency of oil production from productive deposits with hard-to-recover reserves.

There is a known method for increasing the productivity of wells equipped with sucker rod pumps (Umetbaev V.G. Geological and technical measures during the operation of wells: A worker’s handbook. - M.: Nedra, 1989. - 215 pp.).

The method makes it possible to increase the filling factor, pump flow and ensure the maximum well flow rate for a given well productivity, but does not provide a significant increase in the productivity of the well itself due to the presence of a direct connection between the pump productivity and the productivity of the well. To increase the productivity of a well, it is necessary to use additional methods of formation processing (treatment of the bottom-hole zone) and development methods.

There is a known method for increasing the productivity of wells equipped with rod pumps (patent RU No. 2153063, IPC E21B 43/00, 43/25, published on July 20, 2000 in Bulletin No. 20), including changing the operating parameters of the pumping unit, characterized in that After assessing the magnitude of the decrease in productivity of the near-wellbore zone of the formation in comparison with the remote zone and determining the degree of clogging of the near-wellbore zone, a pump with a nominal capacity greater than that required for a given productivity of the well is lowered into the well, development and research are carried out in modes that ensure maximum pump productivity, a depression is created on the formation and removed from the near-wellbore zone of the colmatant, then reduce the operating parameters of the alluvial installation until a minimum supply value is obtained, monitor the dynamics of restoration of the dynamic level, after which the operating parameters of the pumping installation are adjusted to the optimal ones for maximum well productivity.

The method is used in wells with deteriorated productivity indicators of the near-wellbore zone during operation to restore production, but does not take into account the physical and chemical properties of oils and the hydrodynamic characteristics of the formation for the possibility of increasing production above the potential for low-permeability reservoirs with a skin factor less than zero.

The technical essence that is closest to the invention is a method for ensuring the most effective rate of oil withdrawal from a producing well (patent RU No. 2379479, IPC E21B 43/00, published on January 20, 2010 in Bulletin No. 2), including oil production with a rate of liquid withdrawal from a well equal to the flow rate according to the selection limitation criterion, when the flow rate is ensured by the productive characteristics of the formation with the rational use of reservoir energy during long-term trouble-free operation of the well, characterized in that the current daily volume of oil production is adjusted taking into account the average rate of change in the productivity coefficient for the period from the start of operation wells and acceleration of changes in productivity coefficient for the period from the beginning of the current year or another reporting period and are determined according to the following relationship:

,

where Qtek is the current flow rate, m ³ /day;

Qmax - maximum flow rate, m ³ /day;

ΔPopt - optimal value of drawdown on the reservoir, MPa;

Kpr max - initial productivity coefficient, m ³ /(day MPa);

T - total operating time of the well, days;

Ωav - average rate of change in productivity coefficient over time T, m ³ /((day) ² MPa):

,

where Kpr flow is the current value of the productivity coefficient, m ³ /(day MPa);

α - acceleration of change in productivity coefficient for a certain last period of well operation m ³ /((day) ³ MPa)):

,

where Δω is the increment in the rate of change in the productivity coefficient for a certain last period of well operation, m ³ /((day) ² MPa);

t is a certain last period of well operation, for example, from the beginning of the current year or another reporting period, days.

The method is used to regulate production rates taking into account changes in the productivity coefficient over time, but does not take into account the physico-chemical properties of oils and the hydrodynamic characteristics of the formation for the possibility of increasing the flow rate for low-permeability reservoirs with a skin factor less than zero.

The technical result is to increase the efficiency of development of low-permeability reservoirs, maintain high rates of extraction of oil reserves from low-permeability reservoirs by reducing the risk of the release of large amounts of dissolved gas from oil in the wellbore, determine the optimal well for influencing a low-permeability formation by taking into account the skin factor, and accurately determine the optimal flow rate wells by taking into account the maximum possible drawdown on the low-permeability formation.

The technical result is achieved by a method of developing a low-permeability reservoir, including oil production with a rate of fluid withdrawal from a production well.

What is new is that in-depth samples are first taken from production wells, the formation pressure Ppl, the saturation pressure of oil with dissolved gas, the content of dissolved gas and the amount of gas released during differential degassing at each pressure stage are determined, then a linear graph of the dependence of the amount of gas released on the degassing pressure is constructed , determine the Rizl fracture pressure point with a sharp increase in the release of dissolved gas, perform hydrodynamic studies in production wells, determine the dynamic fluid level and bottomhole pressure, shut down a production well with a bottomhole pressure equal to or lower than the saturation pressure of oil with dissolved gas, and take real-time indicators recovery of the fluid level in the production wellbore, construct a fluid level recovery curve, determine the skin factor and well productivity coefficient kpr, select wells with a skin factor less than zero, then determine the well flow rate using the formula:

Q=kpr*(Rpl-Rizl), m ³ /day,

where kpr is the well productivity coefficient, m ³ /(day*MPa),

Rpl-reservoir pressure, MPa,

Rizl fracture pressure, MPa,

Next, the production well is put into operation and oil production is carried out with a fluid withdrawal rate from the well equal to a certain flow rate Q.

The method is carried out as follows.

First, deep samples are taken from production wells.

The reservoir pressure Ppl, the saturation pressure of oil with dissolved gas, the content of dissolved gas and the amount of gas released during differential degassing at each pressure stage are determined.

Next, construct a linear graph of the dependence of the amount of gas released on the degassing pressure.

Using a linear graph, the Rizl pressure point with a sharp increase in the release of dissolved gas is determined. Determining the Rizl fracture pressure point reveals the maximum possible drawdown on a low-permeability formation.

Perform hydrodynamic studies in production wells.

Determine the dynamic fluid level and bottomhole pressure.

The production well is stopped with a bottomhole pressure equal to or lower than the saturation pressure of oil with dissolved gas. In this way, a well is determined that operates in the optimal depression mode.

Indicators of fluid level recovery in the production wellbore are taken in real time.

A liquid level recovery curve is constructed.

The skin factor and well productivity coefficient kpr are determined. Determining the skin factor allows one to characterize the filtration characteristics of the near-wellbore zone and drainage zone of a well to identify wells with improved conductivity of the near-wellbore zone of a low-permeability reservoir.

Select a production well with a skin factor less than zero.

Next, the production well flow rate is determined using the formula:

Q=kpr*(Rpl-Rizl), m ³ /day,

where kpr is the well productivity coefficient, m ³ /(day*MPa),

Rpl-reservoir pressure, MPa,

Rizle-fracture pressure, MPa.

Taking into account the pressure of the Rizl fracture when determining the production rate reduces the risk of releasing a large amount of dissolved gas from the oil in the wellbore, which increases the efficiency of developing a low-permeability formation and operating downhole pumping equipment.

Next, the production well is put into operation and oil production is carried out with a fluid withdrawal rate from the well equal to a certain flow rate Q.

Hard-to-recover oil reserves in low-permeability reservoirs are mainly developed using natural regimes, without maintaining reservoir pressure and limited inflow stimulation technologies. The method makes it possible to determine the maximum possible depression to increase the fluid flow rate of their low-permeability reservoir and eliminate the negative impact of the released dissolved gas on the bottom-hole zone and downhole pumping equipment in the production well when developing an oil deposit below the saturation pressure of oil with gas.

Example of practical application.

Previously, deep samples were taken from production wells.

The formation pressure was determined to be 11 MPa, the saturation pressure of oil with dissolved gas was 3.5 MPa, the content of dissolved gas was 17 m ³ /t and the amount of gas released during differential degassing at each pressure stage is shown in the table.

Table 1. Amount of gas released during differential degassing at each pressure stage

Degassing stage Degassing pressure, MPa Released gas, m ³ /t 1st stage 3.0 0.41 2nd stage 2.5 1.24 3rd stage 2 2.34 4th stage 1.5 3.71 5th stage 1 6.47 6th stage 0.5 17

Next, we constructed a linear graph of the dependence of the amount of gas released on the degassing pressure.

Using a linear graph, the Rizl pressure point was determined to be equal to 1 MPa with a sharp increase in the release of dissolved gas

Performed hydrodynamic studies in production wells.

A dynamic fluid level of 900 m and a bottomhole pressure of 3 MPa were determined.

A production well with a bottomhole pressure of 3 MPa and a fluid flow rate of 4.5 m ³ /day was stopped.

We took real-time indicators of fluid level recovery in the production wellbore.

We constructed a liquid level recovery curve.

The skin factor was determined to be 0.1 and the well productivity coefficient kpr = 0.6 m ³ /(day*MPa).

We selected a production well with a skin factor less than zero.

Next, we determined the production well flow rate Q = 0.6 * (11-1) = 6 m ³ / day,

Next, the production well was put into operation and oil production was carried out with a fluid withdrawal rate from the well equal to a certain flow rate Q = 6 m ³ /day.

The increase in flow rate was 1.5 m ³ /day.

Thus, the proposed method increases the efficiency of developing low-permeability reservoirs, maintaining high rates of extraction of oil reserves from low-permeability reservoirs by reducing the risk of the release of a large amount of dissolved gas from oil in the wellbore, determining the optimal well for influencing a low-permeability formation by taking into account the skin factor, accuracy of determination optimal well production by taking into account the maximum possible drawdown on the low-permeability formation.

Claims (6)

A method for developing a low-permeability oil reservoir, including oil production with a rate of fluid withdrawal from a production well, characterized in that deep samples are taken from production wells, the reservoir pressure Ppl, the saturation pressure of oil with dissolved gas, the content of dissolved gas and the amount of gas released during differential degassing are determined. each pressure stage, then build a linear graph of the dependence of the amount of released gas on the degassing pressure, determine the Rizl break pressure point with a sharp increase in the release of dissolved gas, perform hydrodynamic studies in production wells, determine the dynamic liquid level and bottomhole pressure, shut down the production well with bottomhole pressure , equal to or lower than the saturation pressure of oil with dissolved gas, take real-time indicators of liquid level recovery in the producing wellbore, build a liquid level restoration curve, determine skin factors and productivity coefficients of producing wells kpr, select a well with a skin factor less than zero, Next, the well flow rate is determined using the formula: Q=kpr*(Rpl-Rizl), m ³ /day, where kpr is the well productivity coefficient, m ³ /(day*MPa), Rpl - reservoir pressure, MPa, Rizl - fracture pressure, MPa, Next, the production well is put into operation and oil production is carried out with a fluid withdrawal rate from the well equal to a certain flow rate Q.