Note: Descriptions are shown in the official language in which they were submitted.
CA 02290050 1999-11-17
INTELLEGENT DOWN HOLE TESTING SYSTEM
BACKGROUND OF THE INVENTION
1. Technical Field of the invention:
The present invention relates to an intelligent down hole testing system
used to obtain reservoir information during a well test without the need for
surface
control. Specifically, the present invention allows for the down hole
intelligent
automation of flow and shut-in testing and sampling.
2. Description of Related Art:
The expense of completing a petroleum producing well can quite frequently
exceed the expense of actually drilling the well. As a result, it is critical
that
sufficient information be gathered on the well after drilling to accurately
determine
if it is economically feasible to complete the well. Testing can provide
valuable
information on the type of completion required to insure adequate production
and
proper reservoir maintenance procedures. Further, if a new formation is being
explored, it is particularly critical that representative samples of the
reservoir fluids
be collected and analyzed from the first few wells drilled in order to
evaluate the
formation.
It is also important that any testing be accomplished as quickly as possible,
since any testing performed will necessarily delay production during the test
period. Development wells are drilled for their economic importance to
production, and, therefore, the best testing strategies minimize time on the
well
site.
Important test data can be obtained by measuring the reservoir pressure
and flow rate with the well in a stabilized flow condition and the pressure
and
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temperature of the well down hole when the well is shut-in. A stabilized flow
condition is reached when the well pressure remains unchanged over a period of
time, resulting in steady-state flow, or the pressure changes linearly with
respect
to time while the well is being flowed at a constant rate. A common test
regimen
involves collecting flow rate, pressure, and temperature data while
alternatively
operating the well in stabilized flow and shut-in conditions. Typically,
stabilized
flow data is measured at the surface and interpolated to estimate the actual
flow
rate and pressure down hole. Calculating the flow rate and pressure at the
surface, however, introduces two serious complications. First, the wellbore
storage of production fluids introduces complications in the interpolation of
the
data to down hole rates and pressures due to the expansion or compression of
wellbore fluids in response to changes in the wellbore pressure. Wellbore
storage
may also result in it taking several hours for a steady-state flow at the zone
of
interest to manifest itself at the surface. Consequently, the well has to be
run at a
steady-state for quite some time before data collection actually begins. When
a
limited amount of time has been set aside for testing, for example one day, it
may
be very difficult to run more than one or two stabilized flow and shut-in
tests given
the amount of time it takes to manifest stabilized flow conditions up hole.
Further,
a failure to timely recognize problems in flow testing parameters could lead
to
permanent damage to the production capabilities of the well.
A second problem inherent in measuring pressures and flow rates at the
surface is the fact that, with data thus collected, estimating true down hole
conditions by interpolation techniques is difficult if the reservoir pressure
drops
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below the bubble point. (The bubble point is the pressure below which gas
evolves from an oil solution.) Further, fluid samples taken when the test well
is
below the bubble point can not be used to determine the hydrocarbon
composition of the reservoir. Importantly, gas and liquid phases are typically
not
produced in a formation in the same proportion as they exist in a single phase
above the bubble-point pressure.
While some prior art methods involve measuring pressures and
temperatures down hole, the determination of whether the flow has reached
steady-state is typically made at the surface, and fluid samples are often
taken at
the surface. Even a fluid sample taken down hole may not be of much use if the
sample was taken below the bubble point, a fact that may not be determined
until
after the sample is painstakingly recovered.
Given the problems detailed above with these methods, a need exists for
an intelligent down hole testing system that can flow and shut-in a well based
on
real time data taken down hole. Further, a need exists to collect samples of
reservoir fluid at pressures above the bubble-point without the necessity of
repeated sampling from the rig level and subsequent well flow manipulation.
Such intelligent down hole testing system would save considerable rig time
while
greatly increasing the reliability and accuracy of well testing.
SUMMARY OF THE INVENTION
The present invention relates to an intelligent down hole testing system
that can be run into the well on a work string along with many of the prior
art
components presently used for well testing. The intelligent down hole testing
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system assures that adequate reservoir information is acquired during a well
test
without the need for surface read-out. The invention is programmed on the
surface to flow, shut-in, and sample the well pursuant to the particular test
parameters best suited for each application. The system is then run in the
well in
the same way a prior art drill and testing string is presently run.
Once the testing string has been run into the well and everything is
prepared down hole and at the surface for well testing, the intelligent down
hole
testing system is activated using a signal that is conveyed by wire line,
telemetry,
or hydraulic pulses. During the testing job, the invention interprets
collected data
and samples so as to make decisions about how the well testing should be
carried out. For example, these decisions can include when to open the well
for
flow, when to shut-in the well, and when to choke the well for sampling. These
decisions are base on pre-programmed information. However, if a change in
decision making parameters is necessary, the intelligent down hole testing
system
can be re-programmed by a wire line probe, telemetry, or hydraulic pulses. If
the
invention does not respond to these changes, a hydraulic override feature
allows
manual control of the intelligent down hole testing system. When the
intelligent
down hole testing system has completed its pre-programmed routine a multi-
cycle
safety circulating valve is activated to indicate that manual control of the
system
has been transferred. The operator on the surface then controls the system for
well kill operations.
There are additionally two special logic features of the system that clearly
distinguish the intelligent down hole testing system from prior art methods
and
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apparatus. First, the invention's testing system has a flow and shut-in logic.
During the flow periods, an intelligent control valve monitors the
pressure/temperature sensors to determine stability of the flow period. Once a
pre-determined stability is achieved, a timer is activated. When the timer
completes its cycle, a ball valve in the intelligent control valve closes.
When the
intelligent control valve closes, the shut-in period commences and the
intelligent
control valve returns to monitoring the response from the pressure/temperature
sensors. When pre-determined reservoir shut-in parameters are met, the timer
is
again activated. Once the timer completes this cycle the intelligent control
valve
opens, and the next flow period commences. The intelligent control valve
continues to operate in this manner until programmed to change to a sampling
mode (as described below) or to terminate the well test.
Second, the intelligent testing system comprises a sampling logic. If the
intelligent control valve switches to the sampling mode, the ball valve is
closed
and a variable choke is opened for flow. Once a pre-determined stability is
achieved, a timer in the intelligent sampling system is activated. When the
timer
completes its cycle, the intelligent sampling system captures a sample and
checks the sample to determine if it was taken above or below the bubble-
point.
If the sample was taken below the bubble-point, the sample is discharged and
the
variable choke in the intelligent control valve is choked back a pre-
determined
amount. The intelligent control valve then monitors the pressure/temperature
sensors to determine stability of the flow. Once a pre-determined stability is
achieved, another sample is taken and tested. This cycle continues until the
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sample pressure is measured at the pre-determined pressure above the bubble-
point. Once a correct sample has been taken the intelligent control valve
opens
the ball valve and closes the variable choke. The intelligent control valve
can
resume further flow and shut-in periods or can end the test.
The present invention is a great improvement over prior art methods and
assemblies by reducing the rig time required in running well tests and greatly
increasing the reliability of such tests by taking measurements down hole.
Further, test parameters can be changed to meet unique down hole conditions,
thereby efficiently gathering all necessary data while limiting the potential
for well
damage during testing.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention, and for
further details and advantages thereof, reference is now made to the following
Detailed Description taken in conjunction with the accompanying drawings, in
which:
Figure 1 is a schematic representation of an embodiment of the present
invention.
Figure 2 is a flow diagram illustrating the overall functional sequence of an
embodiment of the invention.
Figure 3a is a flow diagram illustrating the flow and shut-in logic of an
embodiment of the invention.
Figure 3b is a flow diagram illustrating the sampling logic of an
embodiment of the invention.
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DETAILED DESCRIPTION OF THE DRAWINGS
Figure 1 shows an embodiment of the present invention attached to a work
string 20 and placed inside a wellbore annulus 10. Figure 1 shows a single
zone
of interest 15 to be tested. Many of the components illustrated in Figure 1
are
typical of testing apparatus run on a work strings and are optional equipment
that
can be substituted with other equipment or can be left out of various
embodiments of the present invention. For example, Figure 1 shows a
radioactive tag 22 attached below the work string 20 for locating the work
string in
a hole. Below the radioactive tag 22 is shown both a rupture disc safety
circulation valve 24 and a multi-cycle safety circulation valve 26. An
optional, off
the shelf, telemetry system 28 is shown immediately below the multi-cycle
safety
circulation valve 26. Next, Figure 1 shows a jar sub 30 which can be used to
mechanically shock the work string 20 in the event the work string 20 and/or
the
packer 34 becomes stuck. Below the jar 30 is shown a safety joint 32, which is
a
relax point if the jar sub 30 does not work to free the work string 20.
One essential component to the embodiment illustrated is an isolation
packer 34. Such isolation packer 34, however, could be an off the shelf
hydraulic
packer typical of testing and completion assemblies. Other essential
components
to the embodiment illustrated, although also off the shelf technology, include
down hole pressure/temperature sensors 36. Unlike prior art apparatuses,
however, the down hole pressure/temperature sensors 36 are electronically or
hydraulically connected to and monitored by an intelligent control valve 40.
The
intelligent control valve illustrated in this embodiment comprises both a ball
valve
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43 and a variable choke 41. Also unique to the present invention is an
intelligent
sampling system 50, which is electronically integrated with the intelligence
function of the invention.
Continuing down the work string, further optional equipment is shown such
as a vertical shock absorber 60, a firing head 62, TCP guns 64, and radial
shock
absorbers 66, all of which are typical components of a perforation tool. The
inclusion of these perforation tool components with the testing apparatus
illustrates that the testing can be accomplished on the same work string,
which
performs the perforation of the zone of interest 15.
Figure 2 shows a flow diagram of the testing sequence of one embodiment
of the invention. The process begins by programming 210 the intelligent down
hole testing system at the surface. This programming 210 includes the flow,
shut-
in, and sample testing protocol, which will be described in reference to
Figures 3a
and 3b. After the system has been programmed 210, the invention is then run in
220 the well for testing. The run in step 220 can be accomplished exactly as
prior
art drill stem testing strings are presently run in wells. The intelligent
down hole
testing system ("IDHTS") is then activated 230 using a signal that is conveyed
from the surface to the down hole components by wire line, telemetry, or
hydraulic
pulses. Once the invention is activated 230 the intelligent testing 240 takes
place
down hole. This testing includes collecting data (for example, pressure,
temperature, and flow rates), during shut-in conditions, stabilized flow and
testing
and sampling the well fluids. The parameters of all these tests are performed
pursuant to the programming initiated at the programming step 210. If during
the
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test 240 it becomes necessary to change the programming parameters, the
intelligent down hole testing system can be re-programmed 250 by a wire line
probe, telemetry, or hydraulic pulses. If the invention does not respond to
these
programming changes, a hydraulic override feature 270 allows the surface
operator to revert to manual control of the testing components. However, if
the
re-programming step 250 is successfully accepted by the intelligent down hole
testing system, the testing step 240 is resumed. Once all of the intelligent
down
hole testing has been completed 260 a multi-cycle safety circulating valve, or
other like component, can be activated to indicate manual control of the
system
has been transferred to the surface 280. The operator on the surface would
control the intelligent down hole testing system for well kill operations.
Referring now to Figures 3a and 3b, these flow diagrams illustrate the flow
and shut-in logic and the sampling logic, respectively. Consequently, Figures
3a
and 3b provide greater detail of the intelligent testing step 240 illustrated
in Figure
2.
The flow and shut-in logic begins with the step of opening the ball valve
300. This allows for the well to begin flowing back up the work string. While
the
well is flowing, the invention monitors down hole pressure and temperature
sensors 305 in order to identify a stabilized flow. Once the invention has
determined that a stabilized flow has been achieved 310, pursuant to the
parameters programmed at step 210 of Figure 2, a timer is activated 315 in
order
to conduct stabilized flow testing during a predetermined time period.
Pressure
and temperature data is collected during this timed stabilized flow. Once the
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stabilized flow time period expires, the next step involves closing the ball
valve
320. The system again monitors the pressure and temperature 325 until the pre-
programmed shut-in parameters for testing 330 are met. At this point, the
timer is
again activated 335 so that pressure and temperature data can be collected for
the shut-in condition over a predetermined time period. After this shut-in
test is
complete, the system performs an iteration check 340, again pursuant to the
previous programming, to determine if additional well flow and shut-in tests
are
required. If so, the process begins again with the step of opening the ball
valve
300. Otherwise, the intelligent down hole testing system can revert to the
sampling logic mode, as illustrated in Figure 3b, by first closing the ball
valve 345.
With the ball valve closed 345, a variable choke is opened 350 a pre-
determined amount. The initial choke can be based either on previous surface
programming or can be influenced by the data collected during the previous
flow
and shut-in logic testing. Opening the variable choke 350 allows the well
fluids to
again flow up the work string, but at a pressure that can be regulated by
increasing or decreasing the choke. The system again performs a pressure and
temperature monitor step 355 until stabilized flow parameters are met 360. A
timer is then activated 365 to regulate the period of stabilized flow. The
invention
then captures a sample of the well fluid 370. This sample is captured 370 and
evaluated 375 down hole in very close proximity to a reservoir. Consequently,
the
data obtained from this sample is extremely accurate.
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The sample evaluation step 375 determines whether the sample was taken
above or below the bubble point pressure. If the sample was taken below the
bubble point pressure, the sample is discharged 380 and the choke on the
variable choke valve is increased 385. The invention then again monitors the
pressure and temperature 355 until stabilized flow parameters are met 360,
thus
starting the sampling process all over again. If, however, the sample
evaluation
375 determines that the sample was taken at a pressure acceptably above the
bubble point pressure, the sample is retained for further analysis and the
choke
valve is closed 390. The invention then returns to the beginning of the flow
and
shut-in logic illustrated in Figure 3a by opening the ball valve 300. If
additional
flow and shut-in testing is required or programmed, this process is again
initiated
by the pressure/temperature monitoring step 305. The entire system reverts to
the manual mode 395, however, if no further testing is required.
While Figures 3a and 3b illustrate separate flow and shut-in logic and
sampling logic, another embodiment of the invention initially combines the two
logic functions so that they are accomplished simultaneously. This can be
accomplished by performing the first sample capture 370 while a stabilized
flow
test is being timed 315. If the sample then evaluates 375 to be above the
bubble
point, no further sampling logic is required.
Although preferred embodiments of the present invention have been
described in the foregoing description and illustrated in the accompanying
drawings, it will be understood that the invention is not limited to the
embodiments
disclosed, but is capable of numerous rearrangements, modifications, and
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substitutions of steps without departing from the spirit of the invention.
Accordingly, the present invention is intended to encompass such
rearrangements, modifications, and substitutions of steps as fall within the
scope
of the appended claims.
What is claimed is:
