RU2061862C1 - Method for investigation into oil and water saturated strata - Google Patents

Abstract

FIELD: hydrodynamic methods of strata investigation. SUBSTANCE: deep-seated pressure gage is lowered to bottom filled with stratum fluid. The pressure gage is used to measure pressure along well shaft followed with calculation of medium fluid density. Then the well is open and fluid level is decreased. Volume of the extracted fluid is measured. Well is discharged and pressure restoration curve is recorded. On appearing fluid in well mouth the well is closed and recording is proceeded until investigation is over. Hydrodynamic parameters of the stratum is determined on the base of the data obtained. EFFECT: reliable data obtaining. 2 dwg

Description

 The invention relates to methods of hydrodynamic research and can be used in petroleum geology.

 Well-known reservoir research spas (1), including a call inflow of reservoir fluid, registration of pressure recovery curves (KVD) during the entire period of the study and determination of the hydrodynamic parameters from the data obtained.

 The disadvantage of this method is its low efficiency in low-permeability formations and the absence of a stable flow of formation fluid.

 The most sticky to the invention is a method for researching oil and water saturated formations (2), including lowering a deep manometer to the bottom of a working well, measuring its flow rate, recording the bottom-hole pressure change curve in time before and after closing the well, and determining the formation parameters from the data obtained.

 The disadvantage of this method is that the pressure recovery method used in its traditional form does not allow to effectively study low-permeability formations in low-production wells, due to the impossibility of obtaining a stable flow rate, and therefore the hydrodynamic parameters can be determined with significant errors.

где ε гидропроводнoсть пласта, мкм²см/мПа•с;
xr $\genfrac{}{}{0ex}{}{\text{2}}{\text{c.пр}}$ привед нная пьeзопроводность пласта, 1/с;
К_пр коэффициент продуктивности, см³/с•МПа;
Р_пл пластовое давление, МПа;
g ускорение свободного падения, м/с²;
tgβ тангенс угла наклона прямолинейного участка, выделяемого на кривой восстановления давления, зарегистрированной после закрытия скважины (КВД2), преобразованной в координатах [ψ(τ), p(τ)];

p(τ) замеренные значения давлений, снятые с КВД2, МПа;
V объем вытесненной из скважины жидкости при снижении уровня, см³;
Т время от начала подъема уровня жидкости после разрядки скважины до момента ее появления на устье, с;
τ текущее время после закрытия скважины, с;
q_o= K_пр•Δp_o;

N число испoльзованных точек давления на кривой восстановления давления, зарегистрированной в период времени от начала подъема уровня жидкости после разрядки скважины до появления ее на устье (КВД1);
i порядковый номер точки;
P_i замeренные значения давлений, снятые с КВД1, МПа;

Δt интервал времени между точками на КВД1, с.The essence of the invention lies in the fact that in a method for studying oil and water saturated formations, including the descent of a deep manometer to the bottom of an open well, measuring its flow rate, recording the downhole pressure change curve in time before and after closing the well and determining the formation parameters from the received data, descent a deep manometer is produced at the bottom of a closed well filled with formation fluid, with interval measurement of pressures along its wellbore, their average density in the well is determined by their values, I open t the well and lower the fluid level in it, determine the displaced volume of the well, discharge the well, monitor the rise of the liquid level, record the moment the liquid appears at the wellhead and close it, calculate the time from the start of the level rise after the discharge of the well to the indicated moment , and the reservoir parameters are calculated by the following relationships:

where ε is the hydraulic conductivity of the formation, μm ² cm / MPa • s;
xr $\genfrac{}{}{0ex}{}{\text{2}}{\text{c.pr}}$ reduced reservoir conductivity, 1 / s;
To _pr productivity coefficient, cm ³ / s • MPa;
R _pl reservoir pressure, MPa;
g acceleration of gravity, m / s ² ;
tgβ is the slope of the straight section highlighted on the pressure recovery curve recorded after well shut-off (KVD2), transformed in the coordinates [ψ (τ), p (τ)];

p (τ) measured pressure values taken from KVD2, MPa;
V is the volume of fluid displaced from the well when the level is reduced, cm ³ ;
T is the time from the beginning of the rise in the liquid level after the discharge of the well until its appearance at the wellhead, s;
τ current time after well closure, s;
q _o = K _ol • Δp _o ;

N is the number of pressure points used on the pressure recovery curve recorded during the period from the beginning of the rise in the liquid level after the discharge of the well until its appearance at the wellhead (KVD1);
i serial number of the point;
P _i measured pressure values taken from KVD1, MPa;

Δt is the time interval between points on KVD1, s.

The values of the coefficients Δp _o , p _to and α and f (τ) = -Ei (-ατ); f (T + τ) = -Ei [-α (T + τ)]; f (T) = -Ei (-αT); found from the system of equations (1) (3) by the method of successive approximations;
p (τ) ;;
-Ei (-x) integral exponential function;
r _s.pr. reduced well radius, cm;
Into the segment cut off by the rectilinear section of the transformed KVD3 on the ordinate axis ρ;
P _r bottomhole pressure at the time of the appearance of fluid at the wellhead, MPa;
F the cross-sectional area of the pipes, by which the level rises, m ² ;
[ψ (τ), p (τ)] the average density of the fluid in the well, kg / m ³ .

 Achievable technical result when using the invention is to expand the capabilities of the method by examining low-permeability formations in overflowing low-yield wells. At the same time, an increase in the accuracy of determining the hydrodynamic parameters is also achieved.

 The invention is based on the fact that when studying low-permeability formations when it is impossible to stabilize flow rate, registering the KVD in two modes: during the process of raising the level (KVD1) and after closing the well (KVD2) allows you to apply the original methodology for processing the obtained results. This makes it possible to determine with high accuracy the desired parameters of low-permeability reservoirs.

график изменения забойного давления, зарегистрированного после закрытия скважины.The invention is illustrated by drawings, in which Fig. 1 is a graph of the bottomhole pressure change over time during registration of HPC1 and HPC2, and in FIG. 2 shows transformed in coordinates

a graph of changes in bottomhole pressure recorded after well shut-in.

The method is implemented as follows. At the bottom of a closed well prepared for research, i.e. mastered, purified from the flushing fluid and filled with reservoir fluid, lower the depth gauge. It is advisable to use pressure gauges such as "Potok-5" or "Pressure", lowered on a cable to quickly obtain information directly in a mobile laboratory at the wellhead. During descent, the manometer is periodically stopped and pressure is measured along the wellbore at regular intervals, for example, after 100 meters. The obtained pressure values are used to determine the average density of the fluid (reservoir fluid) in the well by a known ratio
[ψ (τ), p (τ)]
where P _{j the} pressure in the well at a depth of H _j .

 After the descent of the deep manometer to sow and hold it for the required time, the well is opened. At the same time, they begin to lower the level in it, for example, by pumping high pressure gas into the annulus using a compressor. The liquid displaced in this case is taken into a measuring container, degassed and the volume is determined. By lowering the level to a predetermined depth, gas injection is stopped and the well is discharged, i.e. the pipe and annular spaces communicate with the atmosphere, which leads to equalization of levels (pressures) in them.

 Fix the beginning of the rise of the levels and record the pressure recovery curve (pressure recovery). Observations are made at the mouth and, at the time the fluid appears there, the well is closed. The time from the start of the level rise after the discharge of the well to the specified point is calculated. The segment of the HPC recorded during this time can be arbitrarily designated as the HPC1 (figure 1).

 After stopping (closing) of the well, the KVD in time (KVD2) is continued to be recorded until a representative rectilinear section is highlighted in FIG. 2.

 Then, the following processing of the obtained information is performed.

,
где p(τ)
τ замеренные значения давлений, снятые с КВД2, МПа;
V объем вытесненной из скважины жидкости при снижении уровня, см³;
Т время от начала подъема уровня жидкости после разрядки скважины до момента ее появления на устье, с;
q_o= K_пр•Δp_o; текущее время после закрытия скважины, с;

N число использованных точек давления на кривой восстановления давления, зарегистрированной в период времени от начала подъема уровня жидкости после разрядки cкважины до появления ее на устье (КВД1);
i порядковый номер точки;
p_i замeренные значения давлений, снятыe с КВД1, MПа;

Δt
Δp_o интервал времени между точками на КВД1, с.KVD3 recorded in coordinates [time-pressure transform in coordinates

,
where p (τ)
τ measured pressure values taken from KVD2, MPa;
V is the volume of fluid displaced from the well when the level is reduced, cm ³ ;
T is the time from the beginning of the rise in the liquid level after the discharge of the well until its appearance at the wellhead, s;
q _o = K _ol • Δp _o ; current time after well closure, s;

N is the number of pressure points used on the pressure recovery curve recorded during the period from the beginning of the rise in the liquid level after the well is discharged until it appears at the mouth (KVD1);
i serial number of the point;
p _i measured pressure values taken from KVD1, MPa;

Δt
Δp _o the time interval between points on KVD1, C.

The values of the coefficients α, P _к and f (τ) = -Ei (-ατ); f (T + τ) = -Ei [-α (T + τ)]; f (T) = -Ei (-αT); found from the system of equations (1) (3) by the method of successive approximations
(ε)
-Ei (-x) is an integral exponential function.

, коэффициент продуктивности скважины (К_пр) и пластовое давление (P_пл) по следующим соотношениям:

где tgβ тангенс угла наклона прямолинейного участка, выделяемого на кривой восстановления давления, зарегистрированной после закрытия скважины (КВД2), преобразованной в координатах [ψ(τ), p(τ)]
r_с.пр. приведенный радиус скважины;
В отрезок, отсекаемый прямолинейным участком преобразованной КВД2 на оси ординат p(τ);;
p_г забойное давление в момент появления жидкости на на устье скважины, МПа;
F площадь сечения труб, по которым поднимается уровень, м²;
ρ средняя плотность жидкости в скважине, кг/м³.As a result, the reservoir hydraulic conductivity (χ / r $\genfrac{}{}{0ex}{}{\text{2}}{\text{s.pr}}$ ), the given piezoconductivity of the reservoir

, the coefficient of well productivity (K _ol ) and reservoir pressure (P _PL ) in the following ratios:

where tgβ is the tangent of the slope of the rectilinear section highlighted on the pressure recovery curve recorded after closing the well (KVD2), transformed in coordinates [ψ (τ), p (τ)]
r _s.pr. reduced radius of the well;
Into the segment cut off by the rectilinear section of the transformed KVD2 on the ordinate axis p (τ) ;;
p _g bottomhole pressure at the time of the appearance of fluid at the wellhead, MPa;
F the cross-sectional area of the pipes along which the level rises, m ² ;
ρ average density of the fluid in the well, kg / m ³ .

 The method has been tested in a number of fields in Western Siberia, in particular, in FIG. Figures 1 and 2 show the results of studies of the low-permeability reservoir AC-12 of the Lower Cretaceous in SLE. 53 of the Priobskoye oil field.

 The effectiveness of the method lies in the fact that it provides complex and reliable information c) the hydrodynamic parameters of the reservoir in the study of low-permeability reservoirs, which can be used to solve problems of calculating reserves, monitoring and regulating the development of oil fields.

Claims (1)

A method for studying oil and water saturated formations, including lowering a deep manometer to the bottom of a well, recording a downhole pressure change curve in time before and after closing a well, and determining from the obtained hydraulic conductivity of the formation, reduced piezoconductivity of the formation, well productivity coefficient and formation pressure, characterized in that, in order to expand the capabilities of the method due to the study of low-permeability formations in overflowing low-yield wells, the descent of the deep manometer drive to the bottom of a closed well filled with formation fluid, with interval measurement of pressures along its wellbore and determine the average density of formation fluid in the well from their values, after the manometer is lowered, the well is opened and the level of formation fluid is lowered in it, its displaced volume is determined, its volume is produced, well discharge, control the rise in the level of the formation fluid, record the moment it begins to rise and record the pressure recovery curve (KVD1), at the time the formation fluid appears at the wellhead close and calculate the elapsed time between the indicated moments, after closing the well, record the pressure recovery curve (KVD2) to obtain a straight section, convert KVD2 in the coordinates [ψ (τ), P (τ)], where

P (τ) —measured pressure values taken from HPC2, MPa;
V is the volume of fluid displaced from the well when the level is reduced, cm ³ ;
T is the time from the beginning of the rise in the liquid level after the discharge of the well until its appearance at the wellhead, s;
τ current time after well closure, s;
q ₀ = K _etc. ΔP _o;

N is the number of pressure points used on the pressure recovery curve recorded during the period from the beginning of the rise in the liquid level after the discharge of the well until its appearance at the wellhead (KVD1);
i serial number of the point;
P _{i the} measured pressure values taken from KVD1, MPa;

Δt is the time interval between points on KVD1, s,
moreover, the values of the coefficients

and α are found from the system of equations (1) (3) by the method of successive approximations;

E _i (-x) is the integral exponential function, and the reservoir hydraulic conductivity ε is the reduced reservoir conductivity χ / r $\genfrac{}{}{0ex}{}{\text{2}}{\text{s.pr}}$ , the coefficient of well productivity K _{p p} and reservoir pressure P _{p l} calculated by the following ratios:

Where
tgβ is the slope of the straight section highlighted on the pressure recovery curve recorded after well shut-in (KBD2), transformed in the coordinates [ψ (τ), P (τ)] ;;
r _{s. p r the} reduced radius of the well, cm;
B is the segment cut off by the rectilinear section of the converted HPC2 on the ordinate axis P (τ);
P _g bottomhole pressure at the time of the appearance of the fluid at the wellhead, MPa;
F the cross-sectional area of the pipes along which the level rises, m ² ;
ρ is the average density of the fluid in the well, kg / m ³ ;
g acceleration of gravity, m / s ² .

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