Method and arrangement for operating an extraction in a borehole
A method and an arrangement for operating a process for extracting a fluid in a borehole are optimized. In the case of deep wells, the location of an interface depth in the borehole is detected. A pressure measurement of the pressure at the head of the borehole is made. The pressure in the liquid in the borehole below the interface depth is determined from the measured pressure at the head of the borehole and the detected location of the interface depth. The determination of this pressure is used for regulating the performance of an extracting device for the liquid that is to be extracted.
1. A method for the extraction of a fluid in a borehole in which a location of an interface depth in the borehole is detected in the case of deep wells,
characterized
in that a pressure measurement of the pressure at a head of the borehole is made,
in that a location of an interface depth is detected,
in that an acoustic event which produces acoustic pressure waves is deliberately effected for the purposes of detecting the location of the interface depth,
in that a pressure in the liquid below the interface depth in the borehole is determined from the measured pressure at the head of the borehole and the detected location of the interface depth, the pressure in the liquid below the interface depth determined using a productivity index (PI), a supply rate (q), and a zero-bottom hole pressure supply rate (q MAX ) of the borehole;
in that an extraction device that comprises a electrically driven pump is provided in communication with the borehole, and
in that the determination of the pressure in the liquid below the interface depth is utilised for regulating the performance of the electrically driven pump for the liquid that is to be extracted from the borehole.
2. A method in accordance with claim 1 ,
characterized
in that the pressure waves produced in the borehole by the event travel into the borehole,
in that pressure waves travelling into the borehole are also reflected at least at the interface depth,
in that the reflected pressure waves travelling out of the borehole at the surface of the earth are captured and the time that has elapsed since the acoustic event is measured,
in that the captured pressure waves are evaluated and are used together with the associated elapsed time for indicating the location of the interface depth,
in that the acoustic event produces a signal sample having a predetermined, time-varying frequency spectrum,
in that the signal sample is emitted into the borehole as an oscillatory event, travels into the borehole and is reflected,
in that captured signals emanating from the borehole at the earth's surface are analyzed,
in that oscillatory events which correlate to the emitted signal sample are filtered out from the captured signals during the analysis, and
in that an estimate of the location of the interface depth is made from the oscillatory events which are correlated to the emitted signal sample amongst the captured signals and the time elapsing since the transmission of the signal sample.
3. A method in accordance with claim 1 ,
characterized
in that a pumping performance of the electrically driven pump is regulated in such a way that constant feed rates and/or a constant location of the interface depth and/or the pressure at the head of the borehole prevail.
4. A method in accordance with claim 1 ,
characterized
in that the determination of the pressure is utilised for a regulation process in such a way that the pressure in the liquid is always held above the boiling point or the bubble point or the beginning of the degassing process.
5. A method in accordance with claim 1 ,
characterized
in that in the case of extraction process conditions using an intermittent mode consisting of cyclic running and switched-off periods, automatic adjustment of switch-off and switch-on time points of the electrically driven pump situated in the borehole is effected as a function of the pressure at the bottom of the borehole.
6. Arrangement for carrying out the method in accordance with claim 1 ,
characterized
in that a pressure measuring device is provided above the earth's surface for the purposes of measuring the pressure at the head of the borehole,
in that a device is provided for detecting the location of the interface depth,
in that the acoustic event produces signal samples having a predetermined, time-varying frequency spectrum,
in that there is provided an evaluating device to which the values of the pressure measuring device and the device for detecting the location of the interface depth are supplied, and
in that the evaluating device supplies values to a control system of the electrically driven pump.
7. A method in accordance with claim 1 ,
characterized
in that the acoustic event which produces acoustic pressure waves is deliberately effected for the purposes of detecting the location of the interface depth in the borehole at the earth's surface in the case of deep wells,
in that the acoustic event produces signal samples having a predetermined, time-varying frequency spectrum,
in that the pressure waves produced in the borehole by the acoustic event travel into the borehole,
in that pressure waves travelling into the borehole are also reflected at least at the interface depth.
8. A method in accordance with claim 7
in that the reflected pressure waves travelling out of the borehole at the earth's surface are captured and the time that has elapsed since the acoustic event is measured.
9. A method in accordance with claim 8
in that the captured and measured pressure waves are evaluated and are used together with the associated elapsed time for indicating the location of the interface depth,
in that the acoustic event produces signal samples having a predetermined, time-varying frequency spectrum.
10. A method in accordance with claim 9
in that the signal sample is emitted into the borehole as an oscillatory event, travels into the borehole and is reflected.
11. A method in accordance with claim 10
in that captured signals emanating from the borehole at the earth's surface are analysed.
12. A method in accordance with claim 11
in that oscillatory events which correlate to the emitted signal sample are filtered out from the captured signals during the analysis.
13. A method in accordance with claim 12
in that an estimate of the location of the interface depth is made from the oscillatory events which are correlated to the emitted signal sample amongst the captured signals and the time elapsing since the transmission of the signal sample.
14. A method in accordance with claim 1
in that the acoustic event produces signal samples having a predetermined, time-varying frequency spectrum.
15. A method in accordance with claim 14 ,
characterized
in that the determination of the pressure is utilised for a regulation process in such a way that the pressure in the liquid is held above the boiling point or the bubble point or the beginning of the degassing process.
16. A method in accordance with claim 1 , characterized
in that the productivity index (PI) is a function of the supply rate (q), a pressure of a reservoir (P r ), and a flow pressure at a bottom of the borehole (P wf ),
in that the zero-bottom hole pressure supply rate (q MAX ) is a function of the productivity index (PI) and the pressure of the reservoir (P r ), and
in that the supply rate (q) is a function of the zero-bottom hole pressure supply rate (q MAX ), the flow pressure at a bottom of the borehole (P wf ), and the pressure of the reservoir (P r ).
17. A method for the extraction of a fluid in a borehole in which a location of an interface depth in the borehole is detected in the case of deep wells,
characterized
in that a pressure measurement of the pressure at a head of the borehole is made,
in that a location of an interface depth is detected,
in that an acoustic event which produces acoustic pressure waves is deliberately effected for the purposes of detecting the location of the interface depth,
in that a pressure in the liquid below the interface depth in the borehole is determined from the measured pressure at the head of the borehole and the detected location of the interface depth,
in that an extraction device that comprises a electrically driven pump is provided in communication with the borehole,
in that the determination of the pressure in the fluid below the interface depth is utilised for regulating the performance of the electrically driven pump for the liquid that is to be extracted from the borehole and
in that for the purposes of determining the pressure in the liquid in the borehole, this is determined using the following equations:
PI
=
q
P
r
-
P
wf
(
1
)
q
MAX
=
PI
*
P
r
(
2
)
q
=
q
MAX
*
[
1
-
(
P
wf
P
r
)
2
]
(
3
)
v
sg
=
q
MAX
*
[
1
-
(
P
wf
P
r
)
2
]
*
GOR
*
B
g
A
F
(
4
)
f
g
=
v
sg
(
C
+
D
*
TU
OD
CA
ID
)
*
v
sg
+
E
*
[
g
*
σ
*
(
ρ
o
-
ρ
g
)
ρ
o
2
]
0.25
(
5
)
wherein PI is the productivity index;
q is the supply rate;
P r is the pressure of the reservoir;
P wf is the flow pressure at the bottom of the borehole;
q MAX is the supply rate in the case of “Zero Bottom Hole Pressure”;
v sg is the empty tube gas speed;
GOR is the ratio of gas to oil;
B g is the volume factor of the gas formation;
A F is a designated surface;
wherein the terms C, D and E are constants;
TU is the inner pipe size;
CA is the outer pipe size;
ρ o is the oil density; and
ρ g is the gas density.
18. A method in accordance with claim 17 , characterized
in that for the purposes of determining the pressure in the liquid in the borehole, this is determined using the empty gas tube speed (v sg ) and the gas bubble fraction (f s ),
in that the empty gas tube speed (v sg ) is a function of the zero-bottom hole pressure supply rate (q MAX ), the flow pressure at a bottom of the borehole (P wf ), the pressure of the reservoir (P r ), the ratio of gas to oil (GOR), and the volume factor of the gas formation (B g ), and
in that the gas bubble fraction (f s ) is a function of the empty tube gas speed, (v sg ) as a function of the inner pipe size (TU), the outer pipe size (CA), the oil density (ρ o ), and the gas density (ρ g ).
19. A system for the extraction of a fluid in a borehole in which the location of an interface depth in the borehole is detected in the case of deep wells, and comprising:
a pressure measuring device that is above the earth's surface for the purposes of measuring the pressure at the head of the borehole,
a device for detecting the location of the interface depth,
an evaluating device to which the values of the pressure measuring device and the device for detecting the location of the interface depth are supplied, wherein an empty tube gas speed and a gas bubble fraction are computed by the evaluation device using a new supply rate for each measurement of the interface depth and the pressure at the head of the borehole, and
an extracting device for extracting the fluid,
wherein the extracting device comprises an electrically driven pump,
wherein the evaluating device supplies values determined from input data to a control system of the electrically driven pump.
20. A system in accordance with claim 19 including a pipeline to transport crude oil from the borehole to the earth's surface.
21. A system in accordance with claim 20 wherein the pipeline runs vertically in the borehole.
22. A system in accordance with claim 21 wherein the pipeline includes an inner tubular pipe and an outer tubular pipe which surrounds the inner tubular pipe concentrically and at the same time forms a pipe wall.
23. A system in accordance with claim 22 wherein the crude oil is extracted upwardly through the inner tubular pipe and an annular space is formed between the inner tubular pipe and the outer tubular pipe.
24. A system in accordance with claim 23 wherein, during the extraction of the fluid, crude oil is ascending in the inner tubular pipe, crude oil is likewise present in the annular space below the interface depth, but above the interface depth a gas is ascending upwardly.
25. A system in accordance with claim 19 ,
wherein the empty gas tube speed (v sg ) is a function of the zero-bottom hole pressure supply rate (q MAX ), the flow pressure at a bottom of the borehole (P wf ), the pressure of the reservoir (P r ), the ratio of gas to oil (GOR), and the volume factor of the gas formation (B g ), and
wherein the gas bubble fraction (f s ) is a function of the empty tube gas speed, (v sg ) as a function of the inner pipe size (TU), the outer pipe size (CA), the oil density (ρ o ), and the gas density (ρ g ).
26. A system in accordance with claim 19 ,
wherein for the purposes of determining the pressure in the liquid in the borehole, this is determined based on equations further using a productivity index (PI), a supply rate (q), and a zero-bottom hole pressure supply rate (q MAX ),
wherein the productivity index (PI) is a function of the supply rate (q), a pressure of a reservoir (P r ), and a flow pressure at a bottom of the borehole (P wf ),
wherein the zero-bottom hole pressure supply rate (q MAX ) is a function of the productivity index (PI) and the pressure of the reservoir (P r ), and
wherein the supply rate (q) is a function of the zero-bottom hole pressure supply rate (q MAX ), the flow pressure at a bottom of the borehole (P wf ), and the pressure of the reservoir (P r ).