AU2009251013A1

AU2009251013A1 - Zonal well testing device and method

Info

Publication number: AU2009251013A1
Application number: AU2009251013A
Authority: AU
Inventors: Barry Nicholson
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-12-23
Filing date: 2009-12-18
Publication date: 2010-07-08

Description

1 ZONAL WELL TESTING DEVICE AND METHOD FIELD OF THE INVENTION 5 This invention relates to equipment for testing eruptive and non-eruptive wells drilled to tap coal seam gas, water or other hydrocarbons. BACKGROUND OF THE INVENTION 10 Well testing systems that allow flow testing of wells, such as drill stem tests (DSTs) consist of one or more packers, used to isolate a section of wellbore under test, and a downhole valve, used to connect the volume isolated by the packers to the hollow string used to carry the equipment to the test depth. In the case of an eruptive well, there is sufficient formation pressure to produce 15 flow of reservoir fluids to the surface where they are separated, measured or flared, as appropriate. In the case of non-eruptive wells, where the formation pressure is insufficient to produce fluids at the surface, the pressure in the hollow string must be lowered, for example by pump or by air displacement, to provide a low pressure sink for the formation fluids to flow into, and slowly fill, 20 the pipe in the string. In both test systems, eruptive and non-eruptive, the downhole valve which measures pressure is either open or closed and does not directly control the flow into the well. The latter is controlled initially by the expansion of fluids in 25 the system, followed by the restriction due to the permeability of the formation under test. Those skilled in the art will be aware that transient test quality is affected by the stability of flow prior to a shut in, so lack of control can lead to wide rate variation during the flowing period, and an unknown amount of drawdown on the formation. These effects cause either multiple transients, high 30 formation stress or yield a test which cannot be interpreted due to multiphase flow. Further, the provision of only a liquid column above the tester valve (called 2 the water "cushion") means the formation fluid must be liquid, otherwise the influx of gas would quickly displace the cushion, and result in gas flow to the surface. 5 In many cases, the simple construction of conventional tester systems also requires the use of multiple high pressure hoses in order to inflate and operate the downhole packers and valve. Alternatively mechanical systems are used which restrict the testers to the use a single packer only, making multiple zone testing a slow process, as each zone must be drilled and tested in sequence, 10 requiring multiple trips, alternating with drill string and testing equipment. OBJECT OF THE INVENTION It is therefore an object of the present invention to provide an improved well 15 testing system for both eruptive and non-eruptive wells through provision of a constant flowrate during testing through the action of real time control of downhole rate, a zonal isolation and testing system that can sequentially test multiple permeable formations in a single trip in a subterranean well to derive reservoir parameters, such as permeability, skin, formation pressure and flow 20 boundaries, that isolates wellbore fluids from the testing string, allowing testing of gas as well as liquid production and avoiding production of wellbore fluids to surface, improving safety and reducing environmental footprint and that avoids the need for separate inflation and deflation lines to packers, improving running and operational efficiency and which can provide small volume chemical or 25 hydraulic fracture treatments of subterranean strata or at least to provide an alternative method of testing eruptive and non-eruptive wells. STATEMENT OF THE INVENTION 30 According to the present invention a well testing device comprises at least two packers designed to seal and isolate a section of bore hole strata to be tested, 3 a pressure chamber with an internal piston which is open on its lower side to the strata under test and has fluid on its upper side, a motorized flow control valve between the sealed section and the pressure chamber, a control and sensor system with bidirectional telemetry to a surface acquisition unit and 5 means to adjust the level of fluid in the pressure chamber as required for the strata under test. In another form of the invention a method is provided for using a well testing device comprising at least two packers designed to seal and isolate a section of 10 bore hole strata to be tested, a pressure chamber with an internal piston which is open on its lower side to the strata under test and has fluid on its upper side, a motorized flow control valve between the sealed section and the pressure chamber, a control and sensor system with bidirectional telemetry to a surface acquisition unit and means to adjust the level of fluid in the pressure chamber 15 as required for the strata under test to measure flow rate pressure of the bore hole strata. BRIEF DESCRIPTION OF THE DRAWINGS 20 Various embodiments of the invention are now described by way of example only with reference to the accompanying drawings in which Fig 1 is an elevation of a hollow string drill stem testing device Fig 2 is an elevation of the hollow string of Figure 1 in situ in a well and Fig 3 is an isometric view of a pressure piston inter carrier. 25 DETAILED DESCRIPTION OF THE INVENTION 30 A preferred embodiment of the device shown in Figs 1 and 2 has lower packer 6, filter 7, spacers 8, upper packer 9, isolation chamber 10 and control module 4 11 all of which are suspended in the well on hollow string of pipe 12 to a predetermined depth based on a review of petrophysical or core data. A predetermined amount of filtered water 13 is injected into pipe 12. 5 By command from surface control unit 14 via electrical cable 25, the operator selects packer 6 or 9 to inflate with water from pipe 12 by opening the corresponding inflation valve 4 or 5, while recording data from downhole or surface sensors on control unit 14. High pressure source 26 which is an air compressor or water pump, is applied to the running string and packers 6 and 9 10 are inflated by displacement of filtered water 13, thus isolating the strata under test. Pressure is retained in packers 6 and 9 by closure of packer valves 4 and 5 respectively. The level of filtered water 13 in the running string is adjusted by applying air 15 pressure to the running string in excess of the annular pressure which is measured by pressure gauge 15 and opening circulation valve 16 to displace water 13 to the annulus of isolation chambers 10. An alternative method of adjustment is to displace or "swab" water 13 out of the running string by the use of winch 17 with wire cable 18 and swabbing tool 19 as shown in Fig 2. 20 The operator sets surface control unit 14 to the desired minimum and maximum drawdown limits, which are measured by pressure sensors 1 and 2. The amount of drawdown is affected by the formation pressure, permeability and skin parameters of the strata to be tested and are unknown prior to the test, 25 and the flowrate through the string is controlled by control valve 3. Upon commencing a test, control module 11 starts to open control valve 3 while monitoring the differential pressure from sensors 1 and 2 and a feedback signal is provided to valve control system 20. Flow from the formation enters through 30 a filter (not shown) to displace piston 24 in isolation chambers 10 which in turn displaces filtered water 13 through control valve 3.

5 Valve control system 20 acts to set a flowrate that falls within the minimum and maximum values of drawdown set by the operator, and then maintains that flowrate for the duration of the flow period, based on a) the calibration data for 5 the valve being used, the measured differential pressure and the position of flow control valve 3, measured by optical sensor 23, b) the signal from the downhole flowmeter 21 and c) the overall pressure change in the string, monitored by pressure gauge 1. 10 After the flow period is complete, the operator sends a command to close flow control valve 3 and continues to record the shut in pressure with formation pressure gauge 2 until the test is complete. At this point, packers 6 and 9 are deflated by transfer of filtered water 13 into the running string by opening packer valves 2 and 3 and piston 24 in isolation chambers 10 is reset by 15 applying pressure from surface and expelling the formation fluids. Where preferred, this sequence can be reversed, so the formation fluids are first re injected into the formation prior to releasing the packers. It will be clear that a number of pressure chambers may be required depending 20 on the flow pressures of the strata to be tested. The measurement of higher permeabilities may require more chambers to be joined together and Fig 3 shows the detail of the inter carrier between chambers which allows pressure piston 34 to travel from one chamber to the next. 25 Pipes 30 attach to annular joining disc 31 by screws 32 and are sealed by 0 rings 33. Piston 34 is carried by annular piston discs 35 and 0 rings 36 seal discs 35 as they carry piston 34 along pipes 30. Piston 34 also has 0 rings 37 which seal piston 34 in discs 35. Accordingly a piston disc 35 carries piston 34 along pipe 30 under pressure until it encounter disc 31. 30 6 At that point it stops and piston 34 continues under pressure through joining disc 31 and into the next disc 35. When piston 34 fully enters disc 35 the pressure will bear on the greater annular area of the face of disc 35 and it will move along pipe 30 carrying piston 34 with it to the next joining disc 31. 5 Accordingly the inter carrier can be used to join as many pressure chambers as are required to measure pressure in the strata to be tested. Those skilled in the art will appreciate that the system described is general in application, and may also be used to perform, for example, injection testing, 10 chemical treatments or hydraulic stress ("frac") treatments by injecting either a) wellbore or formation fluids below the isolation chamber piston or b) fluids provided from surface by removal of the isolation chamber, but retaining the flow control valve 3 or c) chemical treatment fluids pre-loaded into inverted isolation chambers so the flow control valve 3 is below the chamber piston. 15 VARIATIONS It will be realised that the foregoing has been given by way of illustrative example only and that all other modifications and variations as would be 20 apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as herein set forth. Throughout the description and claims of this specification the word "comprise" and variations of that word such as "comprises" and "comprising" are not intended to exclude other additives, components, integers or steps.

Claims

1. A well testing device comprising at least two packers designed to seal and isolate a section of bore hole strata to be tested, a pressure chamber with an 5 internal piston which is open on its lower side to the strata under test and has fluid on its upper side, a motorized flow control valve between the sealed section and the pressure chamber, a control and sensor system with bidirectional telemetry to a surface acquisition unit and means to adjust the level of fluid in the pressure chamber as required for the strata under test. 10

2. The device of claim 1 in which the packers are mounted on a string of pipe containing fluid under pressure and the pressure chamber is formed by the piston within the pipe. 15

3. The device of claim 2 in which the packers are inflated via control valves by the fluid within the pipe.

4. The device of claim 2 in which pressure is applied to the fluid by compressed air. 20

5. The device of claim 2 in which a swabbing tool is used to displace fluid out of the pipe.

6 The device of claim 2 which has two or more pressure chambers incorporated 25 in the hollow string of pipe and coupled so that the internal piston can travel between pressure chambers.

7. The device of claim 2 in which the fluid is filtered water. 30

8. A method of testing a well by using a device comprising at least two packers designed to seal and isolate a section of bore hole strata to be tested, a 8 pressure chamber with an internal piston which is open on its lower side to the strata under test and has fluid on its upper side, a motorized flow control valve between the sealed section and the pressure chamber, a control and sensor system with bidirectional telemetry to a surface acquisition unit and means to 5 adjust the level of fluid in the pressure chamber as required for the strata under test to measure flow rate pressure of the bore hole strata.

9. The method of claim 6 in which the control and sensor system sets desired maximum and minimum test pressure limits and monitors differential pressure 10 from sensors in the pressure chamber to measure flow rate.

10. The method of claim 8 applied to eruptive and non eruptive wells. 15 20 25 30