This is related to a retrieving tool for retrieving a core sample from an underground formation, and in particular, a retrieving tool that collects the fluids released by the core sample.
Samples of an underground formation are taken from a wellbore using a coring tool. U.S. Pat. No. 9,506,307 (Kinsella) entitled “High pressure coring assembly and method” discloses a coring tool used to obtain core samples from an underground formation.
According to an aspect, there is provided a core retrieving tool for retrieving a core sample of an underground formation, the core retrieving tool comprising a coring assembly having a coring bit, a core barrel within the coring assembly, the core barrel defining a core-receiving chamber having a first end and a second end, and an expandable fluid chamber in fluid communication with the second end of the core-receiving chamber, and a valve that is moveable between an open position to receive the core sample and a closed position to seal the first end of the core-receiving chamber when the core sample is received within the core barrel, wherein, when the valve seals the first end of the core-receiving chamber, the expandable fluid chamber is expandable in response to a pressure differential between a pressure of the core-receiving chamber and a pressure outside the core barrel, and in a retrieval state, the expandable fluid chamber is in open fluid communication with the core-receiving chamber such that a pressure of the expandable fluid chamber is equalized with the pressure of the core-receiving chamber.
According to other aspects, one or more of the following features may be provided, alone or in combination: the expandable fluid chamber may be in open fluid communication with the core-receiving chamber when the valve is in the open position and in the closed position; the expandable fluid chamber may comprise a piston movable between a first position toward the core receiving chamber and a second position away from the core receiving chamber, wherein the piston moves in response to the pressure differential; expandable fluid chamber may comprise a first portion and a second portion separated from the first portion by the piston, such that, as the piston moves toward the second position, the second portion contracts to allow the first portion to expand and receive fluids from the core-receiving chamber; the second portion may be filled with hydraulic fluid; the retrieving may further comprise a pressure valve that is in fluid communication with the second portion, the pressure valve opening at a preset pressure to expel the hydraulic fluid from the second portion; the coring assembly may comprise an outer housing and an inner housing positioned between the outer housing and the core barrel, wherein the core barrel and the inner housing may define the core-receiving chamber, the inner housing may carry the valve and the core barrel may be moveable within the inner housing; and the core retrieving tool may further comprise a transfer valve in fluid communication with the expandable fluid chamber for selectively removing fluid from the expandable fluid chamber.
According to an aspect, there is provided a method of retrieving a core sample of an underground formation, the method comprising the steps of:
inserting a core retrieving tool in a wellbore, the core retrieving tool comprising a coring assembly comprising a coring bit, a core barrel within the coring assembly, the core barrel defining a core-receiving chamber having a first end and a second end, and an expandable fluid chamber in fluid communication with the second end of the core-receiving chamber, and a valve that selectively seals the first end of the core-receiving chamber;
drilling the core sample with the coring bit;
receiving the core sample into the core-receiving chamber;
closing the valve to seal the first end of the core-receiving chamber; and
withdrawing the core-retrieving tool from the wellbore and permitting the expandable fluid chamber to expand in response to a pressure differential between the core-receiving chamber and a pressure outside of the core barrel, the expandable fluid chamber being in open, fluid communication with the core-receiving chamber such that a pressure of the expandable fluid chamber is equalized with the pressure of the core-receiving chamber.
According to other aspects, one or more of the following features may be provided, alone or in combination: the expandable fluid chamber may be in open fluid communication with the core-receiving chamber before and after the valve is closed; permitting the expandable fluid chamber to expand may comprise moving a piston within the expandable fluid chamber from a first position toward the core receiving chamber towards a second position away from the core receiving chamber; the expandable fluid chamber may comprise a first portion and a second portion separated from the first portion by the piston; permitting the expandable chamber to expand may comprise contracting the second portion to allow the first portion to expand and receive fluids from the core-receiving chamber; the second portion may be filled with hydraulic fluid; the method may further comprise the steps of opening a pressure valve that is in fluid communication with the second portion upon reaching a preset pressure and expelling the hydraulic fluid from the second portion; the method may further comprise the step of transferring fluid collected in the core barrel to a surface storage container; the core retrieving tool may further comprise an inner housing between the outer housing and the core barrel, wherein the core barrel and inner housing may define the core-receiving chamber, the inner housing may carry the valve, and the core barrel may be moveable within the inner housing; and the method may further comprise the step of sealing the core sample within the inner housing and removing the inner housing from the outer housing
In other aspects, the features described above may be combined together in any reasonable combination as will be recognized by those skilled in the art.
These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein:
A core retrieving tool, generally identified by reference numeral 10, will now be described with reference to
Referring to
As shown, coring assembly 12 has an inner housing 20 positioned within an outer housing 18. Coring bit 14 is carried and driven by outer housing 18, while inner housing 20 defines a core-receiving chamber 32 and an expandable fluid chamber 40. Core-receiving chamber 32 has a first end 34 toward the downhole end 16 of coring assembly 12, and a second end 36 that is open to expandable fluid chamber 40.
Referring to
Valve 60 is shown as a flapper valve, however valve 60 may have any suitable design that, in an open state as shown in
In the depicted example, valve 60 is carried by inner housing 20 and core barrel 30 is movable in an axial direction relative to inner housing 20 and outer housing 18. As is known in the art, core barrel 30 may be used to grip core sample 100, which allows core sample 100 to be withdrawn into core-receiving chamber 32, either by raising core barrel 30 or lowering outer and inner housings 18 and 20. Core barrel 30 may be designed according to known processes to allow core sample 100 to be properly manipulated within coring assembly 12. Typically, a core barrel will have a catcher element (not shown) that grips core sample 100 and breaks off core sample 100 from the formation from which it has been drilled. Once properly positioned within core-receiving chamber 32, valve 60 is permitted to close and seal core-receiving chamber 32. This may be done, for example, by releasing a catch that otherwise holds valve 60 open. Valve 60 may be biased to the closed position, such that, when released, it moves to the closed position. Alternatively, valve 60 may be designed to be pushed open as core sample 100 passes by valve 60, which then closes after core sample 100 no longer holds valve 60 open. Those skilled in the art may provide different designs of valve 60, including the manner in which the valve is opened and closed. In the depicted example, core-receiving chamber 32 is defined by core barrel 30 toward second end 36 and inner housing 20 with valve 60 toward first end 34. As will be understood, the design of inner housing 20, core barrel 30, and valve 60 may vary as deemed appropriate by those skilled in the art, provided that the design permits a core sample to be drilled from a formation, and withdrawn into core-receiving chamber 32 sufficiently that it is able to be sealed within chamber 32. As depicted, this is accomplished by permitting core barrel 30 to move relative to inner housing 20 and valve 60, which closes once core sample 100 is withdrawn sufficiently into core-receiving chamber 32.
Referring to
As shown, expandable fluid chamber 40 is in open fluid communication with core-receiving chamber 32 at all times, i.e. in the core-drilling state, and the retrieval state after the core sample has been formed. However, at the very least, expandable fluid chamber 40 will be in open fluid communication with core-receiving chamber 32 when core sample 100 is sealed within core-receiving chamber 32 and core retrieving tool 10 is in a retrieval state. For example, withdrawing core barrel 30 or closing valve 60 may cause a separate valve or channel to open (not shown). With expandable fluid chamber 40 in open fluid communication with core-receiving chamber 32, the pressure of expandable fluid chamber 40 is equalized with the pressure of core-receiving chamber 32. With valve 60 closed to seal first end 34 of core-receiving chamber 32, fluids 102 including gasses 102 released by core sample 100 will fill core-receiving chamber 32 and expandable fluid chamber 40. As core retrieving tool is returned to surface, the pressure outside of core barrel 30 will be reduced, creating a pressure differential between the pressure in core-receiving chamber 32 and an external pressure. This pressure differential causes expandable fluid chamber 40 to expand, such that gasses 102 and other fluids that have been released or are permitted to be released by the change in pressure from core sample 100 will fill expandable fluid chamber 40 core-receiving chamber 32. This process continues until expandable fluid chamber 40 reaches its largest permitted volume, or until the pressure differential is insufficient to further expand chamber 40.
In the depicted example, expandable fluid chamber 40 is designed with a piston 42 within a chamber housing 44 where the piston is movable within chamber housing 44 between a first position toward core receiving chamber 32 and a second position away from core receiving chamber 32, shown in
As depicted, piston 42 separate chamber housing 44 into a first portion 48 and a second portion 50, where first portion 48 is in fluid communication with core-receiving chamber 32. As piston 42 moves from the first position to the second position, second portion 50 contracts to allow first portion 48 to expand and receive fluids from core-receiving chamber 32. Second portion 50 may be filled with hydraulic fluid that is expelled through a pressure valve 46 in fluid communication with the hydraulic fluid chamber when second portion 50 contracts. Pressure valve 46 may be a check valve that opens once a preset pressure across valve 46 is reached, or it may be a flow restrictor that restricts the rate of flow, such as by appropriate selection of the orifice and/or the viscosity of the hydraulic fluid to provide a desired amount of resistance to movement. If a preset pressure is used, it may fully or partially determine the pressure differential at which expandable fluid chamber 32 expands. Restricting the flow rate through pressure valve 46 may be beneficial as depressurizing a core sample too quickly may damage the integrity of the sample. The hydraulic fluid within second portion 50 will typically be a non-compressible fluid such that the hydraulic fluid cooperates with pressure valve 46 to provide resistance to movement of piston 42. Hydraulic fluid that is expelled through pressure valve 46 may be expelled to an alternate chamber within core retrieving tool 10 or it may be expelled into the wellbore. Other designs that provide an expandable fluid chamber, such as a telescopic chamber where piston 42 is the end of the chamber, may also be used, however having a chamber housing 44 with a fixed length simplifies the use and installation of tool 10.
When piston 42 is in the second position, shown in
Referring to
Referring to
A method of retrieving core sample 100 using core retrieving tool 10 will now be described with reference to
Referring to
Once core sample 100 is received within core-receiving chamber 32 and valve 60 is closed, core-retrieving tool 10 is removed from the wellbore back to surface. Referring to
Referring to
In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the elements is present, unless the context clearly requires that there be one and only one of the elements.
The scope of the following claims should not be limited by the preferred embodiments set forth in the examples above and in the drawings, but should be given the broadest interpretation consistent with the description as a whole.