Method of examining wells. RU patent 2244105.

FIELD: mining industry.

SUBSTANCE: invention can be used in case of gas-lift operation of wells equipped by free piston-type installations. Invention envisages stopping well, connecting tube space and annular space in wellhead, recording bottom zone and wellhead pressures in tube and annular spaces, and computing well operation parameters using inflow curve plotted according to differences of bottom zone and wellhead pressures. Volume of produced fluid is found from potential output of formation and from condition of output of free piston. When comparing these volumes, parameters of well are computed in the base of minimum volume value.

EFFECT: optimized well operation.

2 dwg

The present invention relates to mining, in particular to the study of drilling wells, and can be used in gas-lift well operation, equipped with a plunger lift installations.

The known method for wells to be converted for operation of plunger lift, which stopped at the mouth of the well record the difference of the pressures in the annulus and Elevator pipes. Taking into account the density of the formation fluid to determine the volume of the liquid and the height of her post in the lift pipe. The equation of the balance of pressures in the receipt of fluid and plunger head count of the working gas pressure in the annulus, and the assumption that the plunger is constantly in motion, set the number of cycles plunger lift (see “Plunger Lift: Introduction, Applications, Equipment, Equations, Operations”, the company's catalog Production Control Services, copyright, 1996, p.5-6).

The disadvantage of this method is that the design works well lead without taking into account the real characteristics of the reservoir, working in conditions of variable depression. In addition, the location of the anchor Shoe lift pipes justified for depleted wells and may not be applicable to wells with relatively high formation pressure, where there are restrictions on the amount of depression on the formation.

There is a method of research oil wells copyright certificate №653385, E 21 In 47/00, 1979, including the recovery of downhole pressure to the reservoir with the dimension in the process of further short-term selection of fluid falling downhole pressure, closing wells on the mouth and termination of the selection of the fluid by measuring the change of pressure with time at the bottom, in the annulus and on the buffer. While the magnitude of the flow are calculated according to equation depending on the sectional area of the borehole, the increment in time pressure recovery at the pit's mouth, in the annulus and on the buffer, and the density of the oil at reservoir conditions.

The disadvantages of the above method include the uncertainty in time of sampling fluid, without which it is impossible to predict a decrease in bottomhole pressure and, consequently, the depression on the layer. The working value of the depression defines the performance of the well and in General is in the range between the maximum and minimum values, due to the requirements of sustainable exploitation.

Closest to the proposed method is a method of research wells equipped with a plunger lift installations, RF patent No. 2165519, E 21 In 43/12, 47/00, 2001, including the well shutdown, reducing the liquid to a valid value, the registration bottomhole and wellhead pressures in reported on the mouth of the pipe and the annular spaces and calculation of parameters of the wells, which use the curve flow of the liquid from the difference graphs bottomhole and wellhead pressures, and on it, asking the depression on the layer, calculate the depth of the location of the working holes and the volume of liquid raised for the cycle of operation of plunger lift.

The disadvantages of the prototype should include the inability to design a technological regime of the well based on a comparative analysis of the performance of the reservoir at a variable depression and performance of the lift.

The aim of the invention is to optimize the life of the well.

This is achieved by the fact that in the proposed method of research is well equipped with installing plunger lift, including a stop well, the message pipe and annular spaces on the mouth, registration bottomhole and wellhead pressures in the pipe and annulus spaces and calculation of the parameters of the well along the curve of inflow, based on the difference between the graphs bottomhole and wellhead pressures, calculate the volume of the produced fluid in the potential productivity of the reservoir and the performance condition plunger lift, compare the volume and the lower volume calculate the parameters of a well.

The proposed method is as follows:

- well prepared for the descent of underlying instruments, if necessary, conduct a heat treatment (FACT) and sweeping-up;

- reduce the liquid level in the well to the depth permitted by condition for the establishment of maximum depression of the reservoir;

- lower depth gauge on the bottom of a well; the preferred type of device is nanothermometer AMT, account settings, which is carried out in real time;

- set the second recording gauge buffer wells;

- report on the mouth between the ring and tube space;

simultaneously hermetically isolated from commercial communications and atmospheric pressure;

- conduct simultaneous registration of change of pressure at the bottom hole and wellhead within 24-36 hours with periodic control by measuring the gas pressure in the buffer according to an exemplary gauge every 4-6 hours;

- write down the gradient curve pressure gas-liquid mixture in the tubing when lifting pressure gauge with bottom-hole with periodic stops (step 250 m), or with a uniform continuous movement gauge to check the depth of the device and the time from the beginning of the ascent.

The method is illustrated in the drawings. Figure 1 shows a synchronous changes of pressure in the study wells with a closed mouth, figure 2 - graphs of pressure changes in the research process well # 24226.

For the interpretation of research results in the coordinate system p=f(t) synchronize readings downhole and wellhead pressure gauges and build time dependency downhole R Zab (line I) and wellhead R u (line II) pressure, and graph the difference between these two pressures (line III), which represents a curve of flow of fluid R W back-pressure at the mouth (figure 1). In the right part of the graph mark the formation pressure (point 1), which lay down the minimum depression in the reservoir (point 2). From the obtained point spend a horizontal line to the intersection with the line R Zab (point 3) and drop the perpendicular line which intersects the line R W at the point 4 and the x-axis at point 5. Segment between points 3-4 determines the gas pressure p g on the mouth in the annulus in the research process and during operation of plunger lift. Cut between 4-5 points is determined by the pressure of the liquid column p W on the bottom. A similar construction is performed in the left part of the graph (point 1’-5’), while the segment 1’-2’ corresponds to the maximum depression of the reservoir.

The depth of the arrangement of the working openings are calculated according to equation:

where L p.o - depth location of a work entry opening of the gas, m;

N the middle of the perforation interval, m;

R W - fluid pressure downhole in the annulus is determined by the value of the segment 4-5 (figure 1), PA;

ρ W is the density of the fluid in the downhole conditions, kg/m;

g - free fall acceleration, m/2 .

The density of the fluid with regard to water in wells expect:

p W =(1-k )· R n +k in · ρ;

where k is the moisture content, the proportion of the units;

ρ n and ρ accordingly, the density of oil and water, kg/m 3 .

Time (in minutes) work well when lifting fluid (plunger) with an average speed of 5 m/s and given a ten-minute purge wells to determine:

and stop time well:

Θ =(3,7-5,5)· t

The number of produced fluid expect:

a) the potential productivity of the reservoir

where Q’ C - volume of fluid flow at a variable depression, m 3 ;

the current differential pressure at the well bottom, MPa;

k is the permeability, cm 2 ;

h is the effective thickness of the reservoir, cm;

μ - viscosity, SP;

In the volume ratio of the reservoir fluid;

b) the performance condition plunger lift:

where Q C is the volume of liquid raised to the surface for one cycle when the pressure p ZM , m 3 ;

p sm - pressure gas in the annulus, doing the work of lifting the liquid to the surface, MPa, is determined by the value of the segment 3-4, (1);

R b - pressure buffer well (in the train), MPa;

0,3 - constant characterizing the total loss of pressure on the lifting of the plunger, MPa;

K - coefficient taking into account the pressure losses by friction gas;

p q is the pressure required for lifting to the surface of a unit volume of fluid, MPa/m 3 ;

R m W - pressure drop on the fluid friction when raising the volume units MPa/m 3 .

Comparing volumes of liquids Q’ q u Q C , for the project taking the minimum value, which denote Q C .

The maximum pressure p ZM . max gas in the annulus with the amount of filling of the production string when lifting the plunger to the surface is determined by the ratio:

where F KP and F m, respectively, the area of the ring and the tube space, m 2 .

The increase in pressure of the liquid column in the well bottom, corresponding to the volume Q” C , the assumption that fills all available space well, is equal to:

where Δ R W is the increase in pressure of the liquid column, MPa.

The amount of gas necessary to perform a single operation by lifting the plunger to the surface, calculated according to equation:

V g =16,5·· L po · p SSR ;

where V g is the quantity of gas per cycle, thousand m 3 /cycle;

With - empirical constant;

P SMS - arithmetic mean value of the gas pressure in the annulus, MPa.

Specific gas consumption:

The number of cycles of operation per day:

As an example, consider an updated calculation of the mode of operation of well No. 20226 Urengoy field in the periodic plunger of the gas lift. Figure 2 shows a synchronous time-based downhole (line I) and wellhead (line II) pressures, as well as schedule their difference (line III). Initial data for calculation:

- static reservoir pressure of 17.5 MPa;

- downhole pressure: maximum of 10.5 MPa; minimum of 7.5 MPa;

average 9 MPa;

the flow rate of formation fluids 7.2 m 3 /day (by 115.7 cm 3 /s);

- permeability of 5 MD (5· 10-11 cm 2 );

the dynamic viscosity of the reservoir oil 0,5 SP (0,5· 10 2 kgf· s/cm);

is the density of the oil at reservoir conditions, 640 kg/m 3 ;

- the volume ratio of oil to 1.2;

is the effective thickness of the reservoir 5 m (5· 10 2 cm);

- depth of descent of the tubing (the middle of the perforated interval) 2978 m;

- the area of the annular space -130· 10 -4 m 2 ;

- the area of the inner channel tubing 30· 10 -4 m 2 ;

- pressure gas-lift gas in the annular space of 5.0-7.5 MPa;

- pressure on the buffer (the train) 2.5 MPa;

- gas factor oil formation conditions 185 m 3 /m 3 ;

- empirical constant for pipes 73 mm tubing

- (pν +p MF )=102, K=45000,=0,2904· 10 -5

By construction, we find that the pressure of liquid and gas in the annulus at a minimum depression are respectively equal to: p W =6,1 MPa (cut 4-5), p ZM =4,4 MPa (cut 3-4). The ordinates of the points 4 and 4’ are of 6.1 and 4.7 MPa, and the time points 5 and 5’ - 1225 and 570 min, respectively.

The depth of the location of the working hole:

Open period:

The time of the open period of the curved accept t=15 minutes

The stop time well:

Θ =(3,7-5,5)· t=(3,7-5,5)· 15=55-83 minutes;

accept Θ =75 minutes (4500 s).

The volume of formation fluid per cycle by the condition of the fluid flowing from the reservoir:

The volume of liquid raised by the installation of one cycle for the performance of a plunger lift:

Q” p =0,23 m 3

From the comparison it is seen that Q’ C >Q” C , but at well # 20226 possible supply of gas-lift gas with an operating pressure up to 7.5 MPa, the conversion result for p ZM =5.0 MPa obtained Q” C =0.35 m 3 . For this case, the volume of liquid is practically equal to the volume of inflow and in the further calculation, Q p =0,41 m 3 .

The maximum required operating pressure of the gas in the annulus:

The increase in pressure of the liquid column in the tubing of the working hole (pressure difference across the mouth between the annular space and the buffer in the layout without starting clutch):

The required amount of gas for the cycle:

Specific gas consumption:

less gas the oil factor in the formation conditions, therefore, require additional supply of the working gas;

the number of cycles of operation per day

A method of testing and interpretation of results are implemented in commercial practice in the translation of twenty-three wells Urengoi oil and gas work gas lift plunger. Implementation of the proposed method provided reliable data for the design of modes of operation of the plunger lift installations in Novy Urengoy. The effectiveness of the method is confirmed by comparing the actual and estimated production rate of the well, with the relative difference does not exceed 7%.

The method of research wells equipped with installing plunger lift, including a stop well, the message pipe and annular spaces on the mouth, registration bottomhole and wellhead pressures in the pipe and annulus spaces and calculation of the parameters of the well along the curve of inflow, based on the difference between the graphs bottomhole and wellhead pressures, characterized in that the calculated volume of the produced fluid in the potential productivity of the reservoir and the performance condition plunger lift, compare the volume and the lower volume calculate the parameters of a well.