RU2539445C1 - Method for determining formation pressure in oil producer equipped with submerged electric-driven pump - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention refers to the oil-extracting industry and can be used on oil deposits for measuring formation pressure for controlling and managing the oil extraction process. The method involves measuring the formation pressure in an oil producer equipped with a submerged electric-driven pump. A calculation process involves using a fluid influx point from the formation to the well via a known uniform-density damping fluid when commissioning the well after the damping procedure by formula.

EFFECT: reducing a surveyed well downtime, increasing the accuracy and reliability of determining the foundation pressure, and facilitating the implementation when commissioning the well after damping.

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Description

The invention relates to the oil industry and can be used in oil fields to measure reservoir pressure for monitoring and controlling the process of oil production.

The well-known "Method for determining reservoir pressure in an oil well", which consists in stopping the well, taking a pressure recovery curve using a depth gauge, measuring the bottomhole pressure before stopping the well, followed by interpreting the pressure recovery curve. (RF patent No. 2167289 of 01/19/1999, IPC E21B 47/06).

The disadvantage of this method is that it is necessary to stop the well, also this method is intended for fountain and compressor wells.

The well-known "Method for determining the reservoir pressure of oil-saturated formations", including determining the balance of oil reserves for the well in which the reservoir pressure is determined. The accumulated production of fluid from the well, the accumulated injection volume of the displacing agent, and the accumulated value of its selection from the production well are also determined. The reservoir pressure is determined from the calculation formula. (See Patent No. 2107161 of July 29, 1996, IPC E21B 47/06).

The disadvantage of this method is the complication of the task due to the additional costs and the collection of a large amount of information for each well.

The well-known "Method of hydrodynamic research in a well equipped with an electric centrifugal pump installation" with a frequency-controlled drive made on a mobile vehicle. For monitoring and automatic registration in digital form of wellhead parameters of the well, a hardware-software complex is used. (See Patent No. 2370635 of September 18, 2007, IPC E21B 43/00).

The disadvantage of this method is the complexity of the task by attracting additional transport and material means.

The reservoir pressure is established during its recovery when the well is shut off until complete stabilization. This time is from 6 hours to several days, and oil is not produced.

The need for periodic pressure measurements in a large number of wells leads to noticeable damage in oil production. In addition, technical operations are required to lower the instruments into the formation pressure well.

Well-known studies on the measurement of reservoir pressures in wells equipped with submersible pumps have shown that the practical calculation of reservoir pressure gives large errors. This is due to the uncertainty in determining the average specific gravity of a fluid mixture in a well.

The objective of the invention is to reduce the downtime of wells during the study, increase the accuracy and reliability of determining the results of reservoir pressure and simplify its implementation when the well is put into operation after jamming.

The technical result of the invention is achieved by using the start point of fluid flow from the formation to the well, according to a well-known, uniform in density, killing fluid, when the well is put into operation after killing according to the formula:

$$P_{Pl}={\rho }_{\mathrm{well}.gl.}\cdot g\cdot \left(H_{PeRf.}-H_{n.PR\mathrm{and}t\mathrm{about}\mathrm{to}\mathrm{but}}\right),(\mathrm{one})$$

where ρ _f. - the density of the kill fluid, kg / m ³ ;

g is the acceleration of gravity, m / s ² ;

H _perf. - the depth of the upper perforation holes, m;

H _{N. inflow} - the value of the dynamic level in the well when entering the mode after killing, corresponding to the transition from the rectilinear section of the change to the curvilinear, which characterizes the beginning of the inflow from the reservoir, m

Figure 1 shows the curve of the output of the well to the mode and the curve of the change in fluid density in the annulus.

Figure 2 - determination of the dynamic level graphical method.

During the conclusion of the well to the mode, when the submersible electric pump lowered almost to the bottom, the level changes in the annulus are recorded. From the beginning of the conclusion, the dynamic level begins to decrease, initially (before the influx from the reservoir) the law of change in the dynamic level is straightforward. The transition point from the rectilinear law of change to curvilinear corresponds to the flow of fluid from the reservoir. Inflow from the reservoir is possible provided that the bottomhole pressure is less than or equal to the reservoir pressure. The density of the fluid in the annulus to a dynamic level corresponding to the beginning of the inflow from the reservoir does not change and is equal to the density of the kill fluid. The pressure in the annulus is 0 or close to 0. The formation pressure can be determined by the formula (1).

The density of the kill fluid, the depth of the perforations and the acceleration of gravity are known values. Therefore, the definition of reservoir pressure is reduced to finding the value of the dynamic level in the well when entering the mode after killing, corresponding to the transition from the straight-line section of the change to the curved, which characterizes the beginning of the inflow from the formation. Determine the point H _{N. inflow} can be an approximate method.

The method of determination consists in finding the intersection point between two lines, the first line is the extension of the rectilinear section of the dynamic level change and the first two points with a curvilinear change in the dynamic level (second straight line). At the intersection, we obtain the value of the dynamic level in the well when entering the mode after killing, corresponding to the transition from the straight-line section of the change to the curvilinear, which characterizes the beginning of the inflow from the reservoir. This method can be graphical and analytical. A graphical determination method is presented in figure 2.

The analytical method consists in compiling two linear equations and finding their common point (intersection point). In the first case, we get points 1 (H ₁ ; t ₁ ) and 2 (H ₂ ; t ₂ ), in the second - 3 (H ₃ ; t ₃ ) and 4 (H ₄ ; t ₄ ). The equations of lines take the form:

Where

H ₁ , H ₂ , H ₃ , H ₄ - dynamic level at points 1, 2, 3, 4, respectively, m,

t ₁ , t ₂ , t ₃ , t ₄ - time corresponding to the dynamic levels of H ₁ , H ₂ , H ₃ , H ₄ , h,

H ₁ (t), H ₂ (t) - equations of lines connecting points 1-2 and 3-4, respectively.

Having made mathematical transformations, we obtain the system of equations:

Where

H ₁ , H ₂ , H ₃ , H ₄ - dynamic level at points 1, 2, 3, 4, respectively, m,

t ₁ , t ₂ , t ₃ , t ₄ - time corresponding to the dynamic levels of H ₁ , H ₂ , H ₃ , H ₄ , h,

H ₁ (t), H ₂ (t) - equations of lines connecting points 1-2 and 3-4, respectively.

To find a common point, you need to equate the equations and find the time. Time t _{N. of flow} is equal to:

Where

H ₁ , H ₂ , H ₃ , H ₄ - dynamic level at points 1, 2, 3, 4, respectively, m

t ₁ , t ₂ , t ₃ , t ₄ - time corresponding to dynamic levels of H ₁ , H ₂ , H ₃ , H ₄ , hour

H ₁ (t), H ₂ (t) - equations of lines connecting points 1-2 and 3-4, respectively.

We substitute the obtained values of t by formula (5) into any equation of system (4) and obtain H _inflow . After finding the H _inflow , the reservoir pressure is calculated by the known density of the killing fluid according to formula (1).

Claims (1)

A method for determining reservoir pressure in an oil well equipped with a submersible electric pump, characterized in that the calculation uses the starting point of fluid inflow from the formation to the well, according to a well-known, uniform in density, killing fluid, when the well is put into operation after it is shut off according to the formula
P _pl = ρ _zh.gl. · G · (H _perf. -H _{N. inflow} ),
where ρ _f. - the density of the kill fluid, kg / m ³ ;
g is the acceleration of gravity, m / s ² ;
H _perf. - the depth of the upper perforation holes, m;
H _{N. inflow} - the value of the dynamic level in the well when entering the mode after killing, corresponding to the transition from the rectilinear section of the change to the curvilinear, which characterizes the beginning of the inflow from the reservoir, m

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