1. Field of the Invention
The invention relates to downhole well testing which is a broad term to designate methods to evaluate subterranean rock layers intersected by a well for their potential to produce hydrocarbons.
2. Description of the Prior Art
Downhole well testing consists in lowering an apparatus or combination of apparatuses in the well in order to hydraulically isolate the layer of interest from the rest of the well and enable that layer to either flow into a chamber that is part of the combination of apparatuses or to flow to surface via suitable pipes that are connected to the apparatuses.
After a wellbore has been drilled through the formation, the various layers of the formation are perforated using perforating guns. Following perforation, testing, such as drillstem testing, is performed. Drillstem testing (DST) is a procedure to determine the productive capacity, pressure, permeability and nature of the reservoir fluids, or extent (or some combination of these characteristics) of a hydrocarbon reservoir in each layer of the formation.
In the field of oil and gas well testing, it is common to encounter wells that traverse more than one separate subterranean hydrocarbon bearing zones which may have similar or different characteristics.
In this event, it is today necessary to perform as many Drill Stem Test (DST) trips in the well as there are layers to be tested. This is a source of considerable non-productive time for a drill stem downhole testing operations.
Currently when several layers that are intersected by a given well are to be tested, a separate downhole test is performed on each layer, sequentially starting from the bottom of the well, using a drillstem testing tool (DST tool) also called a test string. At the end of each test, said test string is removed from the well to enable the layer that was just tested to be hydraulically isolated from the well and the test tools to be reset for the next run of the string in the well.
A typical sequence deployed to test two zones in a given well with a downhole testing system according to the prior art is illustrated in
As shown in
In the system as described above, the test string 3 needs to be removed for each layer to be tested, for the test string 3 to be reset and a plug to be set. As a result, the downhole testing of multiple layers in a wellbore may be a lengthy and costly process.
It may take up to several days which may be costly in terms of labor and equipment costs and which delays the completion of a wellbore.
An example of a multizone testing system is disclosed in U.S. Patent Application No. 2006/0207764. This application relates to an assembly enabling a plurality of layers of interest to be sequentially tested. Said assembly comprises a plurality of valves, each being actuatable by dropping a valve-actuating object into the corresponding valve. The valves are successively actuatable to an open state in a predetermined sequence and the different layers are tested or stimulated after actuating corresponding valves to the open state.
The document mentioned above describes a downhole testing system principally related to the stimulation of the layers. Once actuated, the valves cannot be closed. Accordingly, it doesn't provide any flexibility in the testing of the layers.
The system of the present invention solves the above-mentioned problems by providing a testing system which may be used to test several layers within a single trip of the downhole test string in the well and which provides flexibility in the testing of the layers.
According to a first aspect, the invention relates to a multizone testing system, for the testing of subterranean layers, comprising an upper subsystem comprising a control station and a main isolation packer for isolating the upper subsystem from the lower subsystem, a lower subsystem comprising an array of individual apparatuses connected in series, each apparatus being adapted for the testing of one layer and comprising a series of remotely activated tools for hydraulically isolating and testing the corresponding layer. It further comprises a communication system comprising communication means between the control station and the surface and between the control station and each of the individual apparatuses in order to control the remotely activated tools of the individual apparatuses for sequential testing of the layers. The communication system also retrieves data collected by the various tools to the surface.
According to a second aspect, the invention relates to a multizone testing method, for the testing of a plurality of subterranean layers intersected by a well, using a multizone testing system according to the first aspect of the present invention, comprising the steps of running and positioning said system into the well such that each individual apparatus is adjacent to a layer to be tested and controlling the remotely activated tools of the individual apparatuses for a sequential test of the layers.
Other aspects and advantages of the invention will be apparent from the following detailed description and the appended claims.
a to 1f illustrate conventional testing sequences from the prior art (already described).
a to 4c illustrate the sequential multi-zone testing using the system according to one embodiment of the present invention.
a and 5b illustrate the sequential multi-zone testing using the system according to another embodiment of the present invention.
a to 6c illustrate the sequential multi-zone testing using the system according to another embodiment of the present invention.
a to 7d show a table summarizing the states of the different valves (open or closed state) and the different pressure measurements made during a sequential multi-zone testing using a system according to one embodiment of the present invention.
Exemplary embodiments of the invention will now be described in detail with reference to the accompanying figures, in which like elements may be denoted by like reference numerals for consistency.
In the following description, the terms “up” and “down”, “upper” and “lower”, “above” and “below” and other like terms indicating relative positions above or below a given point or element are used to more clearly describe some embodiments of the invention. However, when applied to equipment or methods for use in wells that are deviated or horizontal, such terms may refer to a left to right, right to left, or other relationship as appropriate.
Referring now to the figures and more particularly to
System 100 is designed for use in a well 107 and is equipped with an inner tubing 104 in which the layers' material may flow. Typically, well 107 will have a plurality of well formations or layers of interest, such as designated by numerals 101, 102 and 103 (
As shown on
In the example embodiment of
The lower subsystem 111, located below the main packer 113, comprises an array of individual apparatuses 116 connected in series, each apparatus 116 being adapted for the testing of one layer and comprising a series of remotely activated tools for hydraulically isolating and testing the corresponding layer.
Under operation, the downhole multizone testing system 100 is run and positioned into the well such that each individual apparatus is adjacent to a layer to be tested.
In the example embodiments illustrated on
The testing means advantageously comprise a pressure gauge 123, 125, 127, and a sampling device (not shown in the Figures) to allow the sampling of the tested layer's material.
The tester valves 117, 119, 121 may be remotely controlled to an open or shut-in state and are used to hydraulically isolate the corresponding layers 101-103. The valves 117, 119, 121 allow the layer 101-103 to flow from the well 107 to the upper part of the testing system 100 via the inner tubing 104 of the system 100. In the embodiments shown on
The packers 139, 141, when set, are used to isolate the different layers 101-103 of the well 107. They enable each zone of interest 101-103 to be independently and individually perforated using the perforating gun systems 129, 131, 133 and tested by, for example, pressure measurements and sampling of the layers material.
According to one aspect of the present invention, the control station 151 is a wireless control station and is equipped with a control station antenna 157 (
In another preferred embodiment, communication means between the control station 151 and the surface 105 comprise one or more repeaters 155 to relay the wireless communication between the control station 151 and the surface 105.
In a preferred embodiment, the communication means comprise a long hop link 147 that takes care of the global communication between the surface 105 and the control station 151. Depending on the well characteristics, the long hop link 147 may also include one or more repeaters 155 to relay the communication. The long hop link 147 may be for example an electromagnetic link.
The communication means between the individual apparatuses 116 and between the control station 151, and between the individual apparatuses 116 comprise a short hop link 149, advantageously an acoustic link.
Generally speaking, the communication system enables tool status and data obtained downhole to be conveyed in real time or near real time to surface 105 as well as sending, from surface 105, activation commands to the tools and receiving back a confirmation that the commands have been properly executed.
On
a and 5b describe a system 100 substantially similar to the system described in reference to
a to 6c describe a system 100 substantially similar to the system described in reference to
The multizone testing system described enables the various layers to be tested individually and sequentially, starting from the bottom, as well as commingled, as it is described now.
According to a second aspect, the present invention concerns a multizone testing method for the testing of a plurality of subterranean layers 101-103 intersected by a well 107, using a multizone testing system 100 as described above. The method comprises the steps of:
In a preferred embodiment, and in reference to the multizone testing system 100 described above as shown on
In preferred embodiments, step (b) may comprise one of all of the following steps:
According to the method, the testing of the pressure build up for each of the layer 101-013 is also possible. For example, after the closing of the tester valve 117 of the first individual tool 116, said testing is achieved using the pressure gauge 123 of the first individual tool 116 (step b4′).
In yet another preferred embodiment, the method also comprises the testing of the commingled flow and commingled pressure build-up. Testing of the commingled flow may be achieved for example by:
Testing of the commingled pressure build-up may be achieved for example by:
The same method may be applied using a system 100 in which each individual apparatus 116 further comprises a “Y-block” 504 which splits the inner tubing 104 into two paths: a main path in which the layer's material will flow and a derivative path 505 in which the perforating guns 129, 131, 133 are positioned.
The same method may further be applied using a system 100 where the tester sleeve valves 117, 119, 121 are replaced by tester ball valves 517, 519.
The method is now described in more details according to exemplary embodiments and with references to
As shown on
During the flow period (159), the first layer 101 is tested. For example, pressure, L1Fl, is measured by the first-layer pressure gauge 123 and layer material 157 is sampled by the sampler carrier and/or analyzed by the fluid analyzer 143.
At the end of the flow period (159), the first-layer tester valve 117 is actuated close via the wireless communication system to record the bottom hole pressure build-up, L1Bup, using the first-layer pressure gauge 123.
Once this is completed, and while maintaining the first-layer tester valve 117 closed, the next layer of interest 102 up the well 107 is perforated with the second-layer perforating gun system 131 and layer material 161 is flowed (163) into the inner tubing 104 of the testing system 100 through the open second-layer tester valve 119, as shown on
During the flow period (163), the layer 102 is tested. For example, pressure, L2FI, is measured by the second-layer pressure gauge 127 and layer material 161 is sampled by the sampler carrier and/or analyzed by the fluid analyzer 143.
Further, as the first-layer tester valve 117 is maintained closed, the build-up pressure of the first layer 101 may be measured using the first-layer pressure gauge 123, which enables to test the effect of the flow 163 of the second layer 102 on the pressure build-up of the first layer and to detect if there is communication or leak between the two layers 101 and 102 (interference test).
At the end of the flow period (163), the second-layer tester valve 119 is actuated close via the wireless communication system to record the bottom hole pressure build-up, L2Bup, using the second-layer pressure gauge 127.
Finally, as shown on
During the flow period (167), the layer 103 is tested the same way as the previous layers. For example, pressure, L3Fl, is measured by the third-layer pressure gauge 127 and layer material is sampled by the sampler carrier and/or analyzed by the fluid analyzer 143.
Once again, interference tests may be performed, to measure the effect of the flow of the third layer on the build-up of the first and second layers, using the pressure gauges 123, 125 and while maintaining the first-layer and second-layer tester valves 117, 119 closed, in order to detect if there is communication or leak between the layers 101-103.
At the end of the third flow period 167, the third-layer tester valve 121 is actuated close via the wireless communication system to record the bottom hole pressure build-up, L3Bup, using the third-layer pressure gauge 127.
The same method is repeated for any additional layer that needs to be tested in the well 107.
Once all layers have been tested individually (flow and pressure build-up), all lower tester valves 117, 121, 123 may be reopened to allow all layers to flow commingled. A final global pressure build-up may be recorded by closing the main dual valve 115, as shown on
We describe now an example of the method according to the invention with reference to
One layer below the layer of interest 102 has already been perforated and layer material 157 is flowing (159) in the inner tubing 104, as shown on
We describe now an example of the method according to the invention with reference to
The first layer 101 is perforated the same way as previously explained. Then, layer material 157 is flowed (159) through the first-layer flow port 134 into the inner tubing 104 of the testing system 100. It goes up through the first-layer isolation packer 139 and through the open first-layer tester valve 117. It then exits, via the lower second-layer flow port 135, in the well bore's 107 zone adjacent to the second layer 102. The flow 159 then goes back into the inner tubing 104 of the testing system 100 via the upper second-layer flow port 136, goes through the second-layer isolation packer 141 and through the open second-layer tester valve 119. It then goes back into the well bore's 107 zone adjacent to the third layer 103 via the lower third-layer flow port 137. It finally goes back again into the inner tubing 104 of the testing system 100 via the upper third-layer flow port 138 and so on up to the upper part 109 of the testing system 100 above the main packer 113.
The flows 163, 167 of the layer material 161, 165 of all the other layers 102, 103 to be tested follow the same path as the flow 159 of the first layer 101 starting from the well bore's 107 zone adjacent to the tested layer.
The system according to the invention further enables to convey the data from the testing means of the individual apparatuses to the station in real time using the wireless communication means.
While the invention is described in relation to preferred embodiments and examples, numerous changes and modifications may be made by those skilled in the art regarding parts of the downhole multi-zone testing system and steps of the testing method without departing from the scope of the invention. The advantages of the downhole multi-zone testing system and method as described above include, among others:
Time saving as several zones may be tested individually and together within a single trip in the well of test system.
The data may be accessed in real-time from surface via the wireless communication system.
The status of any given apparatus is accessible in real-time from surface via the wireless communication system.
The various apparatuses may be activated at will from surface via the wireless communication system.
The build-up on the lower zones may be extended whilst testing the layers located above.
Sequential interference tests may be performed between an active (flowing) layer and any shut-in layer located below.
Under ideal conditions of zonal isolation, further time gains may be obtained by starting to flow one layer as soon as the previous one has been shut-in.
In an alternative embodiment, communication between the control station and the surface may also be accomplished by an electrical cable. Many variations of the present invention may be readily envisioned by a person skilled in this art without departing from the scope of the present invention as it is defined in the appended claims.
This application claims of priority to U.S. Provisional Patent Application Ser. No. 60/991,445 filed Nov. 30, 2007, which is incorporated herein by reference.
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Office action for the equivalent Chinese patent application No. 200880118348.3 issued on May 9, 2013. |
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