SU1559122A1 - Method of developing an oil deposit - Google Patents

Abstract

The invention relates to the oil industry. The goal is to increase the productivity of producing wells. For this, a displacing agent is pumped through the injection wells. Production is taken through the production wells with maintaining the bottomhole pressure below the saturation pressure, stopped when the gas content in the gasification zone is in the amount of 1.5-2% of the pore space. Selection and stopping periods alternate between each other. Using the method allows periodically dissolving the released gas in the reservoir, which in turn allows the well to be operated with a maximum phase permeability for oil. 1 tab.

Description

The invention relates to the oil industry, in particular, to a method for developing oil deposits at bottomhole pressures below saturation pressure.

The purpose of the invention is to increase the productivity of production wells.

The method is carried out as follows.

The oil reservoir is developed to maintain reservoir pressure by marginal or in-circuit waterflooding. Production wells are operated at bottomhole pressures below saturation pressure (at the optimal level). For each production well, the time required for the formation of 1.5-2.0% of gas saturation in the near-well zone of the formation is determined by calculation.

After this time has elapsed, the operation of the wells is stopped for the time required to increase the bottomhole pressure above the saturation pressure, which causes the gas evolved in the formation. Then, the well operation mode is resumed at optimum downhole pressures, i.e. the cycles are repeated until they reach a reservoir. The time required for accumulation of 1.5-2.0% of gas saturation is determined by the following method.

When operating wells with bottomhole pressure below saturation pressure, gas saturation is zero at the level of saturation pressure, and maximum at the level of bottomhole pressure. From here, to calculate the volume of gas released in the reservoir, the average of

between saturation pressures and downhole MS).

The dimensionless pressure is determined as the ratio of P to the saturation pressure PH with:

GSR

Ј.ЈЈ. Rnaas

HO

From the values of (1), the fraction of gas released in the reservoir is determined.

G Ј- (2)

t Determine the volume of hectares j-j

for in situ conditions for one day

W,

 3 / day, (3)

T. T GSR X Cf

de QH - oil flow rate, m / day; 2Q

3 - volume coefficient; Gf - gas factor, m3 / m3; G - dale of the released gas in

seam; TCP average layer temperature - 25

tour, K;

P is the average value between the saturation pressure and the downhole pressure;

RS, T atmospheric pressure, MPa; G is the specific volume of gas released when the bottomhole pressure is lower than the saturation pressure, me / m3; TST- 273 K.

Determine the value of the radius of

R.

I.sJx

(four)

where ae is the piezoelectric conductivity, cma / s, determined from the pressure recovery curve (HPC); tr is the time determined from the HPC corresponding to the de-aeration radius.

The volume of gas in the gasification zone is determined from the condition of 1.5-2.0% gas saturation.

W «-Niyh-ra-0,015, (5) 50

where b is the effective thickness of the reservoir, m; m is the effective porosity of the reservoir. The time required for the formation of equilibrium gas saturation is determined.

T.N ..

1 W0

(6)

The time required for the dissolution of the released gas is governed by the time it takes for the reservoir pressure to recover or is determined experimentally.

The effect of gas saturation in the reservoir on the oil phase permeability is determined by calculation using the formula

fH 1.06 (l-Sr) 3-0.006, (7)

where f H - phase permeability

oil, in shares; Sr average gas saturation in

seam

The dependence of the phase permeability of oil gas saturation in the reservoir is given in the table.

As can be seen from the table, with gas saturation in the range of 1.5-2.0%, the phase permeability does not decrease, and therefore the indicated content of free gas should be considered optimal. With gas saturation of 1%, the phase permeability does not decrease, however, the time period of well operation decreases therefore it is not recommended.

Example (well 1). The well in the first period is operated with a bottomhole pressure above the saturation pressure with the following data of Pc 9.7 KPa; P PA 14.4 Iffla; liquid flow rate 32 me / day; water content is anhydrous; productivity coefficient of 6.8 m3 / day-NPA. It is then transferred to an operating mode with a bottomhole pressure below the saturation pressure. The technological indicators are the following: RS - 6.8 MPa; PffA- 14.4Sa; a flow rate of 52 m / day.

In this mode, the well was operated for 7 months. During this period, the bottomhole and reservoir pressure changes slightly and are respectively 6.8 and 14.1 Sha, and the average flow rate (averaged over 7 months) due to the accumulation of gas in the reservoir drops to a critical value to 47 m3 / day, t. e. a reduction in flow rate is 5 m3 / day. After that, the well is stopped for 1 day to dissolve the gas released in the formation. It also removes the pressure recovery curve. Subsequently, the well is put into operation without changing the mode of operation. As a result, the well production rate is restored almost completely and is 51 m3 / day. After 20 days of operation in this mode, the well is re-examined. The research results show that the well productivity during this period has not decreased and amounts to 51.5 m3 / day, i.e. the accumulation of gas released in the reservoir does not exceed 1.5-2.0% of the volume of the threshold space, limited by the degassing radius, and the phase permeability to oil remains at a high level.

Calculations of the length of time during which the gas saturation reaches 1.5-2.0% of the volume of the first space, are made by formulas (1-6). In this case, the calculations use data on well operation with a bottomhole pressure below the saturation pressure and filtration parameters obtained from the pressure recovery curve, which are: Pc - 6.7 Sh; PH "from 9.0 Sha; G - 05 me / me; Q „42 m3 / day; B - 1.16, h - 5 m; m - 0.24; x 330 cm2 / s; tr- 6200 s; TST 273 K; Ter- 293 K.

Determine the average value between downhole pressure Pc and saturation PHqc cf 7.85 Sha, the dimensionless average pressure Ptp

- 0.07.

i

According to the formula (3), the volume of gas released in the reservoir in 1 day is determined:

W0 - 2.63 m3 / day.

The value of the radius of degassing is determined by (4)

Rr - 35 m.

According to (5), the volume of the released gas in the degassing zone is determined from the condition of 1.5% gas saturation W in - 69.2 m.

From (6), the time required for the formation of 1.5% gas saturation is determined: T - 26.3 days.

"about

Similarly, it takes 35 days to form 2.0% gas saturation.

Thus, the periodic dissolution of the evolved gas field (in this case every 26–35 days) allows the well to be operated with maximum oil phase permeability, which provides an increase in well productivity.

five

0

Claims (1)

Invention Formula A method of developing an oil reservoir, which involves injecting a displacing agent through injection wells and selecting products through production wells, maintaining bottomhole pressure below the saturation pressure with subsequent shutdown of production wells to dissolve released gas in the oil, characterized in that, in order to increase the production wells , the production wells are stopped at a gas content in the degassing zone in the amount of 1.5-2% of the first space, and the periods of extraction and shutdown after do alternately alternate.