U.S. patent application number 15/536605 was filed with the patent office on 2017-12-28 for online tracer monitoring and tracer meter.
This patent application is currently assigned to Resman AS. The applicant listed for this patent is Resman AS. Invention is credited to Fridtjof NYHAVN, Thomas SPERLE.
Application Number | 20170370210 15/536605 |
Document ID | / |
Family ID | 55398353 |
Filed Date | 2017-12-28 |
United States Patent
Application |
20170370210 |
Kind Code |
A1 |
NYHAVN; Fridtjof ; et
al. |
December 28, 2017 |
ONLINE TRACER MONITORING AND TRACER METER
Abstract
A tracer method for online monitoring of downhole zonal
contributions of oil, condensate, gas, or water mass flux of a
production flow in a petroleum production well, includes arranging
distinct tracer carrier systems, each in different production zones
in said well, the distinct tracer carrier systems arranged for
releasing unique tracers to a fluid of the production zones, the
tracers having affinity after downhole release to separate phases
of oil, condensate, gas, or water, using an online tracer monitor,
conducting sampling of tracer concentrations for at least one of
the tracers in said zonal mass fluxes at a high sampling rate,
based on said concentration values, estimating the corresponding
zonal tracer fluxes for each delivery data point and using said one
or more estimated zonal mass fluxes to control one or more Petro
Technical processes.
Inventors: |
NYHAVN; Fridtjof;
(Trondheim, NO) ; SPERLE; Thomas; (Ranheim,
NO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Resman AS |
Ranheim |
|
NO |
|
|
Assignee: |
Resman AS
Ranheim
NO
|
Family ID: |
55398353 |
Appl. No.: |
15/536605 |
Filed: |
December 23, 2015 |
PCT Filed: |
December 23, 2015 |
PCT NO: |
PCT/NO2015/050260 |
371 Date: |
June 15, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 43/38 20130101;
G01V 15/00 20130101; E21B 34/06 20130101; E21B 49/08 20130101; E21B
47/11 20200501 |
International
Class: |
E21B 47/10 20120101
E21B047/10; E21B 43/38 20060101 E21B043/38; G01V 15/00 20060101
G01V015/00; E21B 49/08 20060101 E21B049/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 23, 2014 |
NO |
20141559 |
Claims
1.-40. (canceled)
41. A tracer method for online monitoring of downhole zonal
contributions of oil, condensate, gas, or water mass flux of a
production flow in a petroleum production well, said well having
different well components with different behavior, acting as delay
chambers during flush out, and comprising: production tubing; a
completion void; a gravel pack; and surrounding permeable
geological formation, said method comprising: a) arranging one or
more distinct tracer carrier systems each in different production
zones in said well; b) said distinct tracer carrier systems
arranged for releasing tracers to a fluid of said production zones;
c) said tracers having affinity after downhole release to separate
phases of oil, condensate, gas, or water with corresponding zonal
mass fluxes; d) conducting a continuous loop of the following steps
(e)-(f), comprising: e) using an online tracer monitor, conducting
sampling of tracer concentrations for at least one of the tracers
in said zonal mass fluxes at a high sampling rate, said high
sampling and analysis rate, up to 1 sampling/5 sec, [claim, p 11
l2, p 11 second and third paragraph, p 12 bp(e), p19,] but set and
conducted at a time rate obeying Nyquist sampling of information
related to one or more Flow Physical Events and noise; and f) based
on said concentration values and the retention times for the
different delay chambers, estimating the corresponding zonal tracer
fluxes and the zonal mass flux of oil, condensate, gas, or water
for each delivery data point; g) using said one or more estimated
zonal mass fluxes as input to control said production well.
42. The method according to claim 41, further comprising allowing
all or part of a production flow of said well to be separated, into
two or more segregated phases of oil, condensate, gas, and water
before conducting the continuous loop of step (e)-(f).
43. The method of claim 42, further comprising allowing all or part
of a production flow of said well to be continuously separated,
naturally occurring, at said downstream location.
44. The method according to claim 41, wherein the step of using a
tracer monitor e) comprises applying an online tracer sensor
conducting sampling of samples for at least one of the tracers in
said phases at a high sampling rate of up to 1 sample/5 sec, the
method further comprising using an analyzer, analyzing each said
samples and providing discrete concentration estimates of possibly
occurring said unique tracers, said high sampling and analysis rate
conducted at a time rate obeying Nyquist sampling of information
related to one or more petrotechnical processes and noise.
45. The method of claim 41, further comprising allowing all or part
of a production flow of said well to be continuously separated,
forced in a separator, in-line or in a side branch, at said
downstream location.
46. The method of claim 41, further comprising using said one or
more estimated zonal mass fluxes as input to control one or more
Petro Technical processes in said production well, said Petro
Technical processes comprising one or more of: estimating the
quality of clean-up and initial inflow profile of one or more
component; oil, condensate, gas and water in said well; estimating
the inflow profile of one or more component; oil, condensate, gas
and water in said well during normal production; updating of
reservoir model in general; changing injection pattern from
injection wells; adjusting remotely operated downhole chokes to
change drainage pattern around said well; alarm water intrusion
into one or more of said production zones in said well; performing
well flow diagnostics; performing well integrity diagnostics;
performing production allocation; infill drilling optimization;
Reservoir Management Purposes; and Completion optimization and
verification.
47. The method of claim 45, further comprising allowing said
production flow of said well to be continuously annular separated
into annular phase flows of oil, possibly gas, and water.
48. The method of claim 47, further comprising allowing said
annular separation to occur in a cyclone in said production
flow.
49. The method of claim 47, further comprising conducting said
annular separation utilizing an annular flow formation occurring in
a multi-phase fluid meter MPFM.
50. The method of claim 49, further comprising arranging said
online tracer monitor system and said multi-phase fluid meter MPFM
near the Earth's surface, either at the seafloor wellhead or at the
production platform.
51. The method of claim 49, further comprising arranging said
online tracer monitor system and said multi-phase fluid meter MPFM
downhole near said production zones.
52. The method of claim 51, further comprising arranging said
monitor system and said MPFM adjacent to a liner hanger.
53. The method of claim 41, further comprising allowing said
production flow of said well to be continuously separated into
phase flows of oil, condensate, gas, and/or water by suddenly
decreasing pressure in all or part of the flow.
54. The method of claim 41, wherein after said step (c), allowing
all or part of a production flow of said well to be continuously
separated at a downstream location along a production tubing, into
two or more segregated phases of oil, condensate, gas, and water,
at one instant, changing the affinity properties of one or more of
said tracers.
55. The method of claim 54, further comprising introducing soap for
moving the tracer from oil to water.
56. The method of claim 54, further comprising changing the pH of
one or more of said fluids in order to shift the tracer from oil to
water or vice versa.
57. The method of claim 54, further comprising using a cyclone for
centrifuging out tracers.
58. The method of claim 41, wherein under step (c), said tracers
after release having affinity to separate phases of oil,
condensate, gas, or water, in that the tracer will follow the
flowing target fluid while running downstream, said affinity be
based on properties such as being oleophilic or hydrophilic, or
based on equality of densities.
59. The method of claim 41, said tracers being oleophilic, said
tracer bound to or residing in a heavy particle centrifuge
separable from oil to water.
60. The method of claim 41, each said tracer arranged for
conditional release, said distinct tracer carrier systems being
arranged for releasing said unique tracers: on condition; on demand
from the surface or another downhole node; and/or on time.
61. The method according to claim 41, wherein one or more of said
tracers are arranged for being detected using optical sensors.
62. The method according to claim 61, wherein said optical sensors
comprise optical spectroscopy.
63. The method according to claim 61, wherein said optical sensors
comprise a laser source and an optical detector.
64. The method according to claim 41, wherein said heavy particles
have a density similar to the density of water.
65. The method according to claim 64, wherein said particles are
oleophilic.
66. The method according to claim 64, wherein said particles are
hydrophilic.
67. The method according to claim 41, wherein one or more of said
tracers are acoustically detectable.
68. The method according to claim 67, wherein said online tracer
monitor system is an acoustic in-line tracer measurement
device.
69. The method according to claim 67, wherein said online tracer
monitor system is an acoustic clamp on measurement device.
70. The method according to claim 41, wherein one or more of said
tracers are magnetically detectable.
71. The method according to claim 70, wherein said online monitor
system is a magnetic in-line tracer measurement device.
72. The method according to claim 70, wherein said online monitor
system is a magnetic clamp on measurement device.
73. A high frequency multiphase fluid sampler comprising: two or
more multiphase fluid sampler pipes for collecting fluid samples
for each separated phase flow, each fluid sampling pipe further
comprising: a fluid sampling valve; a distributing valve
distributing single phase fluid samples to one or more sensors; and
analyzers for measuring and analyzing fluid samples at a high
measure rate up to 1 measure/5 sec.
74. The device according to claim 73, wherein one or more of said
monitor systems is a multi phase flow meter.
75. The method according to claim 41, wherein one or more of said
tracers are isotopes and detectable by radiation sensors.
76. The method according to claim 75, wherein said online tracer
monitor system comprises a detector of radiation from isotopes.
77. The method according to claim 41, wherein one or more of said
tracers are RF ID and detectable via electromagnetic waves.
78. The method according to claim 77, wherein said online tracer
monitor system is a detector based on electromagnetic waves.
79. The method according to claim 41, wherein one or more of said
tracers are chemical tracers.
80. The method according to claim 79, wherein said online tracer
monitor system is an analyzer for chemical tracers.
Description
INTRODUCTION
[0001] The present invention relates to a method and an apparatus
for online monitoring of tracer concentration of oil-, condensate-,
gas-, or water-following tracers in a production flow in a
petroleum well, if required, estimating the tracer flux, and with
the objective of estimating downhole inflow profiles of one or more
of the fluid phases.
[0002] More specifically the invention is a method for high
frequency online monitoring tracer concentration of oil-,
condensate-, gas-, or water-following tracers in a production flow,
comprising arranging distinct tracer carrier systems in different
production zones in a well for releasing tracers to a fluid of the
production zones, allowing all or part of a production flow of said
well to be separated into two or more segregated fluids and using
an online tracer monitoring system for measuring concentrations of
possible said unique tracers in at least one of said segregated
phases. The monitoring system may be based on a combination of one
or more sensor principles.
BACKGROUND AND RELATED ART
[0003] Throughout this document, the terms "samples" and "sampling"
relates to discrete time values of tracer concentrations;--number
of particles/molecules per volume unit, or tracer fluxes;--flow of
particles/molecules per time unit.
[0004] Exceptions are when fluid samples and fluid sampling are
used to point at the material fluid (liquid or gas) volume from
which the concentrations and fluxes are sampled.
[0005] Tracers are commonly used for monitoring of oil and gas
wells to e.g. verifying the success of a clean-up process during
the completion of a well, for early alarming the operator upon
water breakthrough or for reservoir monitoring for example by
analysis and modelling of downhole inflow profiles, by exploiting
tracer flow back transients.
[0006] The applicant has, during the latest 10 years, established a
petroleum service wherein tracers are used to answer as much as
possible of the basic, slogan-like question: "What flows where and
how much"? The tracer responses, as they appear at surface, are
seldom directly usable for the customer without some data
MANAGEMENT and interpretations. The services delivered to the
client or "Operator", which may be an oil company operating a
petroleum producing field, may be called Real-Time or Timely
Services when they are ACQUIRED, MANAGED and DELIVERED to the
Operator's Workflow to enable/aid/impact a Petro Technical Process
(U1, U2, . . . ), please see FIG. 1.
[0007] But the AQUIREMENT of raw data is not necessarily done with
the same speed as the Real-Time requirements of the DELIVERIES.
Real-Time requirements for a customer are seldom at a higher
frequency than one good "data point" per hour or as little as one
data point per day (a data point can be something like the
estimated inflow profile during a ramp up or at a certain rate).
However, behind each good delivered such data point is normally a
series of much higher frequency raw data points; a requirement for
following all relevant flow dynamics physics. This can in extreme
cases, e.g. when tracers are injected directly into the production
tubing, mean relevant flow variations up to one variation per 10
sec (0.1 Hz). The present invention relates to such high frequency
raw data that is the basis and requirement for producing high
quality Real-Time Service DELIVERIES.
[0008] Traditionally, tracer concentrations are measured by taking
fluid samples out of the production flow, top side, during
so-called "campaigns", and then perform the analysis in a
laboratory, usually on shore. The transport from the sampling site
to the laboratory may include marine helicopter transport, and may
take several hours to reach the laboratory at the very best, so
there is no talk of real-time sampling and analysis in the state of
the art. The present practice is a time consuming and demanding
procedure. There is also a cost component to it that leads to
minimizing the number of fluid samples to be analyzed. Such
campaigns might define the frequency for withdrawal of fluid
samples to e.g. maximum every 5 minutes. Fluid sampling is manually
performed by an operator. Thus, long campaigns will become
unwieldy; the fluid samples may be manually withdrawn from the
production flow by an operator, and the filling and handling of
pre-marked bottles may take up to 41/2 minutes to achieve the goal
of 5 minutes fluid sampling frequency which is the goal of the
present practice. The harsh environment at the production fluid
sampling site may easily incur a loss or untimely fluid sampling of
one or more of the fluid samples. A higher frequency of fluid
sampling will be too difficult to carry out with present practice.
This motivates automation.
[0009] Some approaches to automatic fluid sampling and analysis are
made, and WO2011132040A2 describes a method for monitoring wellbore
comprising placing tracers in subterranean locations within or
proximate the wellbore, repeatedly taking fluid samples from the
flow from the wellbore, and analyzing the fluid samples for the
presence of tracer. A one per hour fluid sampling rate is
indicated. Fluorescent tracers released by water, or on a signal
from top side, are used, and detected/quantified topside by
spectroscopy. The system may also be used for a quantitative
analysis by voltammetry and then a water soluble tracer capable of
undergoing for instance a redox reaction may be used. The fluid
samples are extracted from one phase after permanently separation
of the flow into water, oil and gas, by a production-scale
separator or from a temporarily acting separator. Fluid samples are
taken at the surface by automatic equipment controlled by a
programmed computer, but flasks collecting the fluid samples are
still used. The inspection and measurement is automatically carried
out e.g. every hour by inspection of the fluid sample in the flask,
placed at a rotary table. The rotary table may contain about 30
containers and has to be refilled by fresh containers manually by
an operator daily when the fluid sampling frequency is about one
fluid sample per hour.
[0010] Another automatic fluid sampling and measuring system is
described in US20140260694A1. Tracers are injected to a reservoir
or aquifer, and thereafter produced and fluid sampled to measure
for tracer concentration; that is, the tracer is arranged outside
the wellbore. A fluid sampling device, piping and an automated
solution is installed as an integrated inline system at or near a
wellhead or production manifold. The fluid sampling system is
computer controlled. The sampling frequency mentioned is limited to
very low frequency fluid sampling, e.g. in the range between every
4th to 24th hour. The system further comprises a filtering system,
a phase separation device, and a measurement device. Some examples
of tracers used are e.g. fluorinated benzoic acids, fluorescein
dyes, fluorescing nano crystals or particles and radioactive
tracers, and arranged for be detected by laboratory spectroscopes,
fiber optic fluorospectroscopes, Hall Effect sensors, fluorimeters,
Geiger counters, gas chromatography measurement devices, and post
column reaction spectroscopes and limited to detection of tracers
in a liquid or aqueous phase. The fluid sampling frequency is, as
mentioned above, limited to low frequency fluid sampling, e.g. in
the range between every 4th to 24th hour. Due to the slow flow
fluid velocities in a permeable formation rock outside the
wellbore, such an "ultra low" fluid sampling frequency may be
sufficient for detecting the fastest tracer signals due to
production of tracer with the fluids from the formation.
[0011] Fluids fluid sampling for compositional analysis is another
area that show techniques relevant for this invention. In Oilfield
Review Summer 2009; 21, no. 2 a novel approach is presented.
SHORT FIGURE CAPTION
[0012] FIG. 0 is an illustration of a rough overview of the
applicant's work process related to ACQUIRE, MANAGE and DELIVER
monitoring data to customers. The present invention relates to the
ACQUISITION part of the process and more specifically how Raw Data
are acquired.
[0013] FIG. 1 is an illustration of a section view of a limited
section of a wellbore and it's near-wellbore and indicates the Flow
Physics through the finer reservoir formation and the layers of
subsequently increasing permeability, gravel pack, completion void
of the completion, and into the Production tubing flow.
[0014] FIG. 2 is roughly indicates different residence times,
"t.sub.r", for different types of well components acting,
intentionally or not, as tracer delay chambers, during flushout,
after a build-up of tracer locally due to a halt in the production
flow, or due to an injection of a tracer cloud, or the combination
of the two.
[0015] FIG. 3a to FIG. 3d are illustrations similar to FIG. 1,
and
[0016] FIG. 3a shows a normal production scenario with a tracer
system arranged outside the Production tubing. In the illustrated
embodiment the tracer system, which releases tracer molecules or
particles, is arranged in the annulus, more specifically in the
completion void between the production tubing and a metal sand
screen. A gravel pack here fills the remainder of the annulus,
radially up to the borehole wall to the reservoir formation.
[0017] FIG. 3b indicates a so-called tracer cloud which may form by
diffusion during shut-in of a well, wherein fluids move minimally
in the example illustrated For longer shut in periods the cloud
will probably spread past the borehole wall and into the reservoir
formation as well.
[0018] FIG. 3c illustrates the situation just after opening/re
opening the chokes; production flow has started or resumed in the
production tubing adjacent to the built up tracer cloud. The
tracers in the production tubing starts flowing to the surface, but
the response time for the tracer cloud parts, the tracer residence
times, in the completion void and within the gravel are generally
progressively longer with increasing distance from the production
tubing axis.
[0019] FIG. 3d illustrates a subsequent stage in the flushing
process wherein much of the tracers in the tubing have followed
along with the production flow and the part of the tracer cloud in
the completion void has also started to follow along with the
production flow.
[0020] FIG. 3e illustrates a subsequent stage in the flushing
process wherein the tracer cloud in the gravel has also been partly
flushed out to follow along with the production flow, and also
having migrated significantly away from the borehole wall. The
steps of FIGS. 3a to 3d are, with a normal production flow,
expected to take 20-30 seconds or considerably longer time up to
several minutes. The flushing of the gravel, scenario 3e, may take
up to an hour.
[0021] FIG. 4 is a diagram showing zonal tracer flux towards the
surface with fully vented sand screen (completion void) and gravel
pack, as was illustrated in FIGS. 3a-3e. A so-called "ultra-high
frequency" zonal tracer flux signal may have arisen due to the
flushing out of the base pipe (Production tubing) as such, with a
pulse "width" of 10-15 seconds. A lower, but still high frequency
tracer signal is due to the flushing out from the completion voids.
Further, there is a low frequency tracer signal from the flush out
from the gravel, with a pulse width on the order of minutes to
hours.
[0022] FIG. 5 shows data from a real well. Zonal tracer flux to
surface is shown. The fluid sampling interval is every 5th minute.
A modeled separation of the measurements into a high frequency
zonal tracer flux signal and a lower frequency zonal tracer flux
signal has been drawn. There are, due to under-sampling in the
fluid sampling (too low fluid sampling frequency), too few data
points in the beginning of the fluid sampling series to discern the
zonal tracer flux flushout from the base pipe liner.
[0023] FIG. 6 is a section of a production well similar to the view
of FIG. 1, but here the tracer source in place illustrates a
mechanical release tracer source. Since no accumulation of tracer
material during shut-in is needed, the mechanical injector device
enables forming a tracer cloud during full flow rate. Note that the
cloud during such conditions is not expected to have sufficient
time to significantly form inside the gravel, so zonal tracer flux
signals migrating to the surface may most probably all be high
frequency components. A concept of mechanical release of tracer is
described in WO2013062417A1.
[0024] FIG. 7 is a simplified section illustration of a well and
its transport system to the tracer sampling/monitoring point,
according to the invention. General noise and distortion are
described below. The tracer's carrier systems (Trs.sub.1, . . . ,
Trs.sub.n) are placed each in different production zones (Z) within
the annulus up to the borehole wall in said well (1). Possible
inflows of oil, gas, water condensate (Fo,Fc,Fw,Fg) for each zone
are indicated.
[0025] FIG. 8 is an illustration sketch of an embodiment of the
invention wherein the tracer is measured in a gaseous phase top
side by e.g. GC, SIFT MS etc.
[0026] FIG. 9 is an illustration sketch of an embodiment of the
invention where each tracer has unique acoustical response and is
detected and measured by an acoustic clamp on or in-line tracer
measurement device.
[0027] FIG. 10 illustrates detection of tracer particles with
non-linear acoustic properties compared to the oil or water flow in
which they are transported. This may be conducted directly on a
phase of the flow.
[0028] FIG. 11 is an illustration of the zonal tracer flux signal
for one single tracer in one single zone. The zonal tracer flux
with noise is shown in the upper diagram while it is plotted
against frequency in the lower diagram. This illustrates the
frequency bands of noise and the different signal components from
gravel flush out, void flush out and ultra-high frequency flush out
for the tubing. The Nyquist sampling frequency is shown as two
times the highest frequency component of either the signals or the
noise, whichever has the highest frequency.
[0029] FIG. 11a is an illustration of a tracer flux signal for one
single tracer, wherein the information carried by the tracer flux
is, due to some near steady-state flow condition, low frequent.
Note that the noise component may still be high frequent so high
sampling frequency will still be needed.
[0030] FIG. 12 is an illustration of an embodiment of a multiphase
flow fluid sampler according to the invention. Fluid sampler pipes
(SP1, SP2, . . . ) extend into each separated phase flow (Fw, Fo,
Fg, Fc). Fluid sampling valves (SV, SV1, SV2, . . . ) and
distributing valve (DV, DV1, DV2, . . . ), are further arranged at
the piping. A manifold valve may be arranged for distributing
samples from the sampling valve, so as for distributing consecutive
fluid samples to chromatographic columns. This will significantly
increase the sampling analysis rate.
[0031] FIG. 13 is a simplified illustration of the process flow
according to different embodiments of the invention represented by
four different options. The illustration shows embodiments
monitoring either conducted on a side branch of the production
flow, or at the full production flow. All sampling should obey
Nyquist Sampling Theorem and according to the bandwidth of the
physics in question. The options/embodiments may operate separately
or in combination. Option #4 may be used for campaigns or
calibration purposes. Monitors may be calibrated by a manually
sampling e.g. on larger volumes of retracted flow fluid samples for
analysis in a laboratory.
TECHNICAL FIELD OF THE INVENTION
[0032] The applicants studies performed by for instance the concept
shown in WO2012057634A where actually measured concentrations and
type of tracer material over time, are compared with calculated
model concentrations for the type of modeled tracer material and
adjusting the model mass influx rates so as for improving the
consistency between the model mass influx profile and the real mass
influx profile show that tracer transients occurring in the
wellbore such as in a completion void, in a screen, in the gravel
pack, and possibly in the near wellbore part of the formation, play
an important role.
[0033] Many real-well studies indicate that tracer transients after
shut-in or low rate production perform with significantly longer
time constants than what could be expected from the completion
voids or the production tubing alone. This can also be concluded
from both CFD-simulations and from flow laboratory tests. A
plausible explanation is that tracer molecules released during
shut-in or low rate production may migrate into the annulus
comprising completion voids and gravel pack and possibly into the
near wellbore formation either by diffusion if still liquids or by
convection if cross flow. This generally creates tracer delay
portions around the production tubing, which we may call "delay
chambers", a chamber where tracers are delayed according to the
characteristic tracer residence time distribution. When production
is resumed to its desired flow level there will be flush-outs from
delay chambers with different permeabilities, porosities and
adhesion parameters that together form the tracer residence times
in the different delay chambers that are formed in and around a
wellbore, please see illustration in FIG. 1. To enable the
decomposition of the different signal components it is crucial that
sufficiently high sampling frequencies are performed (Nyquist). By
this it should be possible to identify the different time constants
which correspond to the different layers. This is then crucial for
estimation of zonal rates.
[0034] The applicant's earlier patent publication WO2012057634A is
based on tracer transients from completion voids wherein the
geometries and flow conditions in the different chambers are
assumed to be known. When these assumptions are valid the residence
times from the different chambers will mainly be a function of flow
rate through the chambers, and the time constants may be compared
from one chamber to another, giving relative flow rates.
[0035] Exploiting multi-chamber tracer flush-outs for zonal rate
estimation; Typically, delay chambers with different residence
times are formed from
[0036] a) production tubing,
[0037] b) completion voids,
[0038] c) man-made particle layers in the annulus, such as
gravel,
[0039] d) geological formation.
[0040] Significantly different flush-out time constants (residence
time distribution) may be derived from the different delay
chambers, such as indicated in FIG. 2.
[0041] FIG. 3a shows a similar setup as FIG. 1 and which is the
geometry through which well inflow is occurring. Note that a tracer
release system is now placed into one of the so-called "delay
chambers": the completion void.
[0042] FIG. 3b show an imagined example where a tracer cloud is
formed around a tracer system during shut-in and so that the cloud
extends into the annulus: from the production tubing, completion
void, and gravel. FIG. 3c-e illustrates the situation after the
production is resumed: The part of the tracer cloud that has
accumulated in the completion void and the production tubing has
shorter tracer residence times and are flushed out faster than the
part of the cloud that resides inside the gravel which has both
lower permeability and wherein the fluid has a longer distance to
go and more possible paths.
[0043] Tracer Cloud Forming with Downhole Mechanical Injector
[0044] Tracers may be placed in different zones with mechanical
injector and/or release systems and may be released as a function
of time, at a given condition, or upon a release signal from the
surface. More or less the same physics as for the above discussed
tracer behavior will be applicable except for some features: [0045]
The tracer cloud may not diffuse much into the gravel as for a
shut-in volume of fluid so it will have more high frequency
components. [0046] The tracer cloud is formed during full
production rate, which is a huge benefit due to the undisturbed
stability of the production flow. [0047] All flush-outs will be
faster and not suffer any of the ramp-up effects that would
otherwise cause more uncertain flow dynamics.
[0048] The prior art techniques for fluid sampling from the well
production flow and analyzing tracer concentration provides up to
maximally one fluid sample per hour, which is too low frequent
tracer concentration determination for the tracer signal for
analyzing dynamic tracer movement within the borehole, and far too
low also for characterizing noise in the system.
[0049] Thus, there is a need for a new, automated, online, sampling
and measurement system for high frequency sampling and
analysis.
[0050] Sampling Frequency
[0051] Distortion and noise;
[0052] Distortion and noise are two different undesired effects on
signals that will/may happen as tracers are travelling from the
production zone (sand face) up to the tracer monitoring point.
[0053] Distortion will for transient zonal tracer flux signals be
different kinds of dispersion; particles and molecules are smeared
out as they migrate. This distortion will only make the signal more
low frequent, so for this invention there will be no issues, ref
FIG. 11. Distortion may be regarded a change in the original
signal. [0054] Noise is an undesired, random signal that is added
(superposition) to the zonal tracer flux signal. Noise is added to
signals due to different Flow Physical Events when tracers are
travelling through the upper part of the well and the subsea
flow-lines to reach to the tracer monitoring point (TMP). Noise can
randomly fluctuate the signals (flow instabilities), and it
disturbs the process of revealing the desired information that was
modulated onto the zonal tracer flux in the downhole production
zone. To be able to "de-noise" the zonal tracer flux signal we
first must assure that the highest tracer noise frequency
components practically available are monitored (sampled) according
to the Nyquist sampling theorem.
[0055] The Nyquist Sampling Theorem Applied for in-Well
Tracing;
[0056] Any zonal tracer flux signal from a real well may be
considered as a signal which comprises components at various
frequencies (changes per time unit). Traditionally, tracers from
wells are monitored at slow sampling frequencies (each 5 minute or
slower) so little experience has been built on finding the real
information bandwidth (highest frequency components) that may
exist. There may be relevant changes in the sub minute range, so
that the bandwidth may be up to 0.1 Hz (one change period per 10
seconds) or even higher frequency. Suppose the highest frequency
component for a given zonal tracer flux signal is f.sub.max.
According to the Nyquist Theorem, the tracer monitoring sampling
rate must be at least 2f.sub.max, or twice the highest frequency
component in the zonal tracer flux signal, ref FIG. 11. That means
that in extreme cases, the zonal tracer flux with a sampling
frequency of 0.2 Hz (one sample per 5 seconds) may be required.
[0057] One such extreme case is when a tracer is injected directly
into the production tubing flow and the transport to surface is
relatively dispersion-free (short and stable flow path). It may
then be required to monitor with a sampling frequency of 0.2 Hz
(one sample per 5 sec) to reconstruct the rapid flushout from the
downhole production tubing. Another example is when two or more
tracer carrying flows from different wells are commingled at a
seafloor manifold, and at least one flow source is unstable, e.g.
oil-water-gas rates are rapidly varying.
SHORT SUMMARY OF THE INVENTION
[0058] The present invention relates to a method and an apparatus
for online monitoring of tracer concentration of oil-, condensate-,
gas-, or water-following tracers in a production flow in a
petroleum well, with to overall objective of estimating the
downhole inflow profiles of all phases. The invention comprises a)
arranging distinct tracer carrier systems each in different
production zones in said well b) said distinct tracer carrier
systems arranged for releasing unique tracers to a fluid of said
production zones, characterized by c) said tracers having affinity
after downhole release to separate phases of oil, condensate, gas,
or water) allowing all or part of a production flow of said well to
be separated at a downstream location, along a production tubing,
into two or more segregated phases of oil, condensate, gas, and
water, conducting a continuous loop of the following steps (e)-(g),
comprising: e) using an online tracer monitor, conducting sampling
of samples at least one of said phases at a high sampling rate of
up to one sample per 5 sec. f) using a tracer monitoring system and
providing concentration estimates of possibly occurring said unique
tracers, said high sampling and analysis rate conducted at a time
rate obeying Nyquist sampling of information related to one or more
Flow Physical Events and noise, g) based on said concentration
values, estimating zonal mass flux of oil, condensate, gas, or
water for each sampling time, using said one or more estimated
zonal mass fluxes to control said one or more Petro Technical
Processes.
DESCRIPTION OF THE INVENTION AND EMBODIMENTS
[0059] In the following the invention will be described with
references to, but not limited to illustrations in the attached
figures.
[0060] The applicants work process is related to ACQUIRE and MANAGE
raw zonal tracer flux data and finally DELIVER usable information
to customers. This invention relates to the ACQUISITION and a
method and an apparatus for high frequency online monitoring of
zonal tracer flux of oil-, condensate-, gas-, or water-following
tracers in a production flow in a petroleum well so as for
detecting tracer concentrations that corresponds to so-called
"ultra-high frequency" zonal tracer flux signals.
[0061] The invention is a tracer method for online monitoring of
downhole zonal contributions of oil, condensate, gas, or water mass
flux (Foz, Fcz, Fwz, Fgz) of a production flow (2) in a petroleum
production well (1), comprising
[0062] a) arranging distinct tracer carrier systems (Trs1, Trs2, .
. . ) each in different production zones (Z1, Z2, . . . ) in said
well (1), please see FIG. 7.
[0063] b) said distinct tracer carrier systems (Trs1, Trs2, . . . )
arranged for releasing unique tracers (Tr1, Tr2, . . . ) to a fluid
of said production zones (Z1, Z2, . . . ); characterized by
[0064] c) said tracers (Tr1, Tr2, . . . ) having affinity after
downhole release to separate phases of oil, condensate, gas, or
water with corresponding zonal mass fluxes (Fo, Fc, Fw, Fg),
[0065] conducting a continuous loop of the following steps (e)-(f),
comprising:
[0066] e) using an online tracer monitor (5), please see FIG. 13,
conducting sampling of tracer concentrations (c1, c2, . . . ) for
at least one of the tracers (Tr1, Tr2, . . . ) in said zonal mass
fluxes (Fo, Fc, Fw, Fg) at a high sampling rate of up to 1 sample/5
sec, said high sampling and analysis rate conducted at a time rate
(R) obeying Nyquist sampling of information related to one or more
Flow Physical Events and noise, please see FIG. 11,
[0067] f) based on said concentration values (c1, c2, . . . ),
estimating the corresponding zonal tracer fluxes and ultimately the
zonal mass flux of oil, condensate, gas, or water (Foz, Fcz, Fwz,
Fgz) for each delivery data point
[0068] using said one or more estimated zonal mass fluxes (Foz,
Fcz, Fwz, Fgz) to control said one or more Petro Technical
processes (U1, U2, . . . ), please see FIG. 1.
[0069] In an embodiment of the method according to the invention
all or part of a production flow (2) of said well (1) is allowed to
separate at a downstream location (4), along a production tubing
(3), into two or more segregated phases (Fo, Fc, Fw, Fg) of oil,
condensate, gas, and water (o, c, g, w).
[0070] In an embodiment the tracer monitor (5) is an online tracer
sensor (5s), conducting sampling of samples (s) for at least one of
the tracers (Tr1, Tr2, . . . ) in said phases (Fo, Fc, Fw, Fg) at a
high sampling rate of up to 1 sample/5 sec and an analyzer (5a),
analyzing each said samples (s) and providing discrete
concentration estimates (c1, c2, . . . ) of possibly occurring said
unique tracers (Tr1, Tr2, . . . ), said high sampling and analysis
rate conducted at a time rate (R) obeying Nyquist sampling of
information related to one or more petrotechnical processes (U1,
U2, . . . ) and noise, mostly as one unit but in some embodiments
may be separate units.
[0071] By sampling at a high frequency rate one may be able to
reconstruct all signal and noise components for the zonal tracer
flux. Obeying the Nyquist sampling theorem is a basic requirement
for obtaining this. The sampling frequency should be set to twice
the signal or noise component that has the highest frequency
content. The reconstruction of all signal and noise components is a
requirement for separating information from noise. Based on a
sequence of high frequency concentration measurements, a good and
reliable delivery data point is given, at the frequency that suits
the customer's work process.
[0072] High frequency raw data enable the estimation of multiple
delay chamber flushouts, as indicated in FIG. 2. This is a major
advantage of the invention and a requirement for using the delay
chambers flushout time constants as carriers of zonal rate
information.
[0073] The high frequency sampling may also enable a reconstruction
of high frequency tracer pulse arrivals. These may in some cases be
important carriers of time-of-flight information,--a well-known
technique for flow rate estimation.
[0074] The separation of the flow may take place close to the choke
at the seabed or at the surface platform. The tracer monitor system
will be chosen dependent of the separated phase (oil, gas, water,
liquid type, etc.) and the type of tracer to be measured. For
measuring the tracer concentration of each tracer type there might
be used more than one sensor principle. The method is developed for
high frequency sampling for monitoring high frequency zonal tracer
flux, but for other purposes in may work on a slower basis.
[0075] The distinct tracer carrier systems (Trs1, Trs2, . . . ) is
arranged each in different production zones (Z1, Z2, . . . ) and
close to the sand face. A normal placement is in completion voids
like the drainage layer of sand screens.
[0076] The main purpose of the invention is monitoring what flows
where and how much flows in producing wells. The information
created may be used for direct action on one or more Petro
Technical Process. One such process is to use the result for
controlling the choke for adjusting the petroleum production up or
down, such as for improving the oil/water ratio, or for adapting
the petroleum/water/gas flow into a production separator and for
feeding the data into a model for history matching.
[0077] One advantage of the invention is that it is an online
automatic monitoring method and it enables not only conducting
continuous campaign-based monitoring for one or a few hours, but
even monitoring going on for days, continuous monitoring over
weeks, months or even years; always with the possibility of
catching the most rapid changes and with no manual action
required.
[0078] In an embodiment of the invention, all or part of a
production flow (2) of said well (1) is allowed to be continuously
separated, naturally occurring, at said downstream location (4) and
in one embodiment all or part of a production flow (2) of said well
(1) may be continuously separated, forced in a separator, in-line
or in a side branch, at said downstream location (4), see FIG. 13.
In an embodiment of the invention the annular separation that is
utilized for flow monitoring reasons in some multi-phase flow
meters MPFM (8) may also be used for measuring the tracer
concentrations. An extra advantage may then be harvested from the
correlations with simultaneous high precision estimation of flow
rates that are produced by the MPFM. Annular separation will also
occur naturally in any flow line and will be amplified through
bends; so flow-driven cyclone effects may be used independently of
MPFMs. Centrifuges may add efficiency to the separation
process.
[0079] The Petro Technical processes (U1, U2, . . . ) may comprise
one or more of: [0080] estimating the quality of clean-up and
initial inflow profile of one or more component; oil, condensate,
gas and water in said well (1), [0081] estimating the inflow
profile of one or more component; oil, condensate, gas and water in
said well (1) during normal production, [0082] updating of
reservoir model in general [0083] changing injection pattern from
injection wells [0084] adjusting remotely operated downhole chokes
to change drainage pattern around said well (1), [0085] alarm water
intrusion into one or more of said production zones (Z1, Z2, . . .
) in said well (1), [0086] performing well flow diagnostics [0087]
performing well integrity diagnostics [0088] production
allocation
[0089] One or more Petro Technical processes (U1, U2, . . . ) may
also be related to operations such as opening or closing valves
changing flows, intrusion of water, leaks occurring, periodically
changing flow in the reservoir, noise etc.
[0090] In an embodiment of the invention wherein the annular
separation utilizing an annular flow formation occurring in a
multi-phase fluid meter MPFM the online tracer monitor (5) and said
multi-phase fluid meter MPFM (8) is arranged near the Earth's
surface, either at the seafloor wellhead or at the production
platform.
[0091] In an embodiment of the invention, the online tracer monitor
system (5) and said multi-phase fluid meter MPFM (8) are arranged
near the Earth's surface, either at the seafloor wellhead or at the
production platform.
[0092] In an embodiment of the invention the online tracer monitor
system (5) and said multi-phase fluid meter MPFM (8) are arranged
downhole near said production zones.
[0093] In an embodiment a monitor will have a sampling device,
please see an embodiment of such in FIG. 12, that is arranged for
instance close to the MPFM. The sampling device will be connected
to the sensor and analyzer of the monitor by shorter or rather long
piping systems, allowing sensor and analyzer (5) to be placed in
non-hazardous environment, such as a control room, a laboratory or
another protected place. Sensor and analyzer might be the one and
same equipment, a monitor, or parted in physically separated
devices, preferably with electronic connection.
[0094] In an embodiment of the invention the monitor system (5) and
said MPFM (8) is arranged adjacent to a liner hanger (11).
[0095] An advantage of sampling tracers and fluid flow at the same
location is both that one may utilize the separated flow already
separated for the MPFM for the tracer sampling and one is measuring
tracer concentrations (c1, c2, . . . ) at the same location in the
flow as all other flow parameters are measured by the MPFM (8).
Having the measurements at the same place will provide measurements
relating to a common sampling time and are more easily related.
Also, having tracers analyzed at the same location as MPFM gives
the benefit of directly knowing the flow condition at the location
and with a high sampling rate.
[0096] In an embodiment of the invention the production flow (2) of
said well (1) will be continuously separated into phase flows (Fo,
Fc, Fw, Fg) of oil, possibly gas, and water (o, c, g, w) by
flashing, i.e. by suddenly decreasing pressure in all or part of
the flow (2). The monitoring of the tracers may then be performed
by the automatic sampling device topside in a gaseous phase. The
tracer sensor is a GC, SIFT MS or the like, as illustrated in FIG.
8. The Tracers used will normally be a liquid at bottom hole
pressures and will flash into a gas state when the pressure is
reduced. At the topside choke, the pressure is normally reduced
from above 10 bars and almost down to 1 bar. Gas is easy to take
out in a side-stream topside, and gas+tracer is fed to topside
analysis equipment. Many installations do already have GC's or
other analysis equipment in place and the tracer analyzing
apparatus should be arranged to handle samples as quick as every
second. The gas+gaseous tracers can be analyzed online topside with
real-time transfer of data to an office, preferably electronic
transfer, and further used together with other real time data of
physical properties or flow measurements.
[0097] In an embodiment of the invention, the affinity properties
of one or more of said tracers (Tr1, Tr2, . . . ) are changed
between said steps (c) and (d) of
[0098] c) said tracers (Tr1, Tr2, . . . ) having affinity after
downhole release to separate phases of oil, condensate, gas, or
water (Fo, Fc, Fw, Fg),
[0099] d) allowing all or part of a production flow (2) of said
well (1) to be continuously separated at a downstream location (4)
along a production tubing (3), into two or more segregated phases
(Fo, Fc, Fw, Fg) of oil, condensate, gas, and water (o, c, g,
w).
[0100] One way of doing this is by introducing a soap (a
surfactant) for moving the tracer (Tr) from oil (Fo) to water (Fw)
or changing the pH of one or more of said fluids in order to shift
the tracer (Tr) from oil to water or vice versa.
[0101] Moving tracers from one phase to another may allow tracer
released or transported by one phase in the tubing to be detected
in another phase further downstream and by using the monitor system
(5). For instance tracers arranged for optical detection in a water
phase may release by, or to, the oil phase but later being detected
in the water phase with equipment able to measure in water phase.
This method may also be used for other phases e.g. tracers may be
detected at a GC arranged for measuring tracers in the gas flow for
instance to the flaring system. One may then also measure tracers
for more phases without fluid sampling more phases. The transfer of
tracers between phases may be performed between any of the phases
in the flow and due to particular e.g. tailor made, characteristics
of the tracers.
[0102] In an embodiment a cyclone (6) is used for centrifuging out
tracer particles (Tr), such as from oil to water; in an embodiment
by removing a light mantle of the particle to change the bulk
tracer particle buoyancy so it can be balanced towards the density
of a fluid different from the one it was following due to the
affinity. A mantle can also be of greater density so as to change
to a heavier phase after it is separated from the bulk
particle.
[0103] In an embodiment of the invention under step (c), after
release the tracers (Tr1, Tr2, . . . ) have affinity to separate
phases of oil, condensate, gas, or water (Fo, Fc, Fw, Fg), in that
the tracer (Tr1, Tr2, . . . ) will follow the flowing target fluid
while running downstream, the affinity is based on properties such
as being oleophilic or hydrophilic, or based on equality of
densities, or based on surface properties. The tracers (Tr1, Tr2, .
. . ) being oleophilic, may also be bound to or residing in a heavy
particle (higher density than oil) centrifuge separable from oil to
water.
[0104] In an embodiment of the invention the distinct tracer
carrier systems (Trs1, Trs2, . . . ) is arranged for releasing said
unique tracers (Tr1, Tr2, . . . ) [0105] on condition of
surrounding fluids (so called intelligent release), [0106] on
demand (on signal form surface or another down hole node), and/or
[0107] on time.
[0108] In an embodiment of the invention one or more of said
tracers (Tr1, Tr2, . . . ) are arranged for being detected using
optical means (5), and then using such optical means (5) as a
detecting sensor. Optical means may in an embodiment be an optical
spectroscope. Optical detectors may easily be used for a water
phase and also for the gas phase. Optical inspection of the oil
phase is not that easy measurement due to the interference in used
light area. Optical detection of tracers from the oil phase may
rather be detected in another phase after changing phases as
mentioned above. An exception is e.g detection of tracers with
fluorescent properties that may be optical detectable in or at the
surface of an oil phase. In an embodiment comprising tracers
arranged for electric detection, then the oil phase will be a
suitable monitoring phase.
[0109] Optical means (5) may, in an embodiment, comprise a laser
source and an optical detector.
[0110] In an embodiment heavy particles having a density similar to
the density of water may be used so as for allowing the particles
to migrate into the water and flow with the water, or for allowing
the particles to migrate to the oil/water boundary. If oleophilic
they may then reside at the interface and be more easily detected.
In an embodiment such particles are hydrophobic.
[0111] In an embodiment of the invention the one or more tracers
(Tr1, Tr2, . . . ) are acoustically detectable. Such tracers could
be flexible to be able to be separated from detected other
particles in a well, please see FIG. 10. Such acoustic sensors (5)
may be an in-line tracer measurement device or it may be an online
acoustic clamp on measurement device. This embodiment may be used
as a stand-alone method or in combination with other embodiments.
Acoustically detectable tracer particles are injected into the
downhole production stream in different locations. The tracer
particles will carry unique addresses for each zone and will be
programmed to follow specific target phases (affinities). The
tracer particles may have special and unique acoustical responses
so that they will feature different scattering than sand, dirt, gas
bubbles etc. Resonance effects, non-linear effects may be used and
combination of the two.
[0112] In an embodiment of the invention the, one or more of said
tracers (Tr1, Tr2, . . . ) are magnetic detectable, and the online
tracer sensor (5) is a magnetic in-line tracer measurement device
or a magnetic clamp on measurement device. This embodiment may be
used as a stand-alone method or in combination with other
embodiments.
[0113] In an embodiment of the invention the fluid samples is
retracted from the flow by a multiphase fluid sampler comprising
two or more multiphase fluid sampler pipes (SP1, SP2, . . . ) for
collecting fluid samples for each separated phase flow (Fw, Fo, Fg,
Fc), each fluid sampling pipe further comprising a fluid sampling
valve (SV1, SV2, . . . ), a distributing valve (DV1, DV2, . . . ),
distributing single phase fluid samples to one or more sensors and
analyzers (5) for measure and analyzing fluid samples at a high
measure rate of between 1 measure/5 sec to one measure per 5
minutes, please see FIG. 12. It is an advantage to the invention
that the fluid sampling may be controlled by a fluid sampling valve
for each phase which may be controlled by instruction signal from
an operator, e.g. due to a defined campaign or on a signal set on
the basis of another happening such as change in flow, temperature,
pressure measured elsewhere in the monitored petroleum system. The
distributing valve will distribute fluid samples to the different
columns of a sensor (5) or to different sensors or apparatus. This
will ensure that tracers in the fluid samples may be detected with
the required high speed, such as e.g. every 5th second.
[0114] In an embodiment of the invention this fluid sampler is
connected to a multi phase meter and as well as the tracer sensor
and then constituting a complete tracer and flow meter for high
frequency online monitoring.
* * * * *