Patent Application
20240384640
The present disclosure relates to a method and system for remediating a wellbore, particularly by extracting contaminants from a contaminated region associated with the wellbore.
Hydrocarbon extraction or fracking activities typically result in uncontrolled release of contaminants, such as methane (coal seam gas) or carbon dioxide gas, from a production zone. Gases or vapours that escape from the production zone may travel along gaps created in the rock surrounding the borehole (also referred to as a wellbore) or in the cement surrounding the production casing of the borehole and the surrounding rock and migrate into a water permeable layer, potentially contaminating water supplies. These contaminant gases and vapours may also escape from the production zone over time and migrate through these gaps, ultimately being released into the atmosphere and potentially contributing to greenhouse gas emissions. It is also difficult or impossible to fix the leak of contaminants as they occur below the surface and on the outside of the casing of the wellbore. It is also possible that the casing or the cement of the wellbore may fail over time as a result of structural or chemical failure resulting in leaks through the casing.
It is desirable to reduce or minimise contamination of a water permeable layer. It is also desirable to capture the contaminants to reduce or minimise the leakage of greenhouse gases released into the atmosphere from the wellbore.
Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and/or combined with other pieces of prior art by a skilled person in the art.
According to one aspect of the invention, there is provided a system for contaminant extraction from a contaminated region of a borehole including a production pipe extending from a surface of the earth through a water permeable layer and into an underlying production zone, the system comprising: a side remediation borehole located proximate the borehole and extending through the water permeable layer towards the production zone, the side remediation borehole including a remediation pipe; and a vacuum source in fluid communication with the side remediation borehole, the vacuum source being configured to extract gaseous contaminants from the side remediation borehole and the region of the borehole.
The system may further comprise an outlet of the remediation pipe that is in direct or indirect fluid communication with an outlet pipe of the production pipe to combine the gaseous contaminants with gases extracted from the production pipe for downstream filtering and/or processing. The remediation pipe may include a lowermost funnel for directing gaseous contaminants migrating from the production zone towards the remediation pipe.
The system may further comprise a gas filtration assembly in fluid communication with the side remediation borehole and configured to filter gaseous contaminants extracted from the side remediation borehole and the region of the borehole. The gas filtration assembly may include a series of gaseous contaminant filter modules providing multi-stage filtering. The series of gaseous contaminant filter modules may be arranged in two or more releasably connected filter banks. The multi-stage filtering provided by the series of gaseous contaminant filter modules may involve four filtration stages. The gas filtration assembly may also be located in a relocatable container. The relocatable container is coupled to a lifting and lowering system for lifting and lowering the relocatable container from, or into, a subsurface pit.
The system may further include a filtered gas storage system in fluid communication with a filtered gas outlet from the gas filtration assembly.
The vacuum source may comprise a venturi pump driven by gases from the production pipe.
According to another aspect of the invention, there is provided a method for contaminant extraction from a contaminated region of a borehole including a production pipe extending from a surface of the earth through a water permeable layer and into an underlying production zone, the method comprising: providing a side remediation borehole located proximate the borehole and extending through the water permeable layer towards the production zone, the side remediation borehole including a remediation pipe; coupling a vacuum source to the side remediation borehole, the vacuum source being configured to extract gaseous contaminants from the side remediation borehole and the region of the borehole.
The method may further comprise extracting gaseous contaminants from an outlet of the remediation pipe that is in direct or indirect fluid communication with an outlet pipe of the production pipe to combine the gaseous contaminants with gases extracted from the production pipe for downstream filtering and/or processing. The remediation pipe may include a lowermost funnel for directing gaseous contaminants migrating from the production zone towards the remediation pipe.
The method may further comprise extracting the gaseous contaminants through a gas filtration assembly in fluid communication with the side remediation borehole and the vacuum source, wherein the gas filtration assembly is configured to filter gaseous contaminants extracted from the side remediation borehole and the region of the borehole. The gas filtration assembly may include a series of gaseous contaminant filter modules providing multi-stage filtering. The series of gaseous contaminants may be arranged in two or more releasably connected filter banks. The multi-stage filtering provided by the series of gaseous contaminant filter modules may involve four filtration stages. The gas filtration assembly may also be located in a relocatable container.
The method may further comprise coupling a filtered gas storage system to a filtered gas outlet from the gas filtration assembly.
As used herein, except where the context requires otherwise, the term “comprise” and variations of the term, such as “comprising”, “comprises” and “comprised”, are not intended to exclude further additives, components, integers or steps.
Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings.
The production well head 112 may be located at the surface or located in a sub-surface pit 118 as shown in
A blowout preventer, choke line and kill line may also be provided at the production well head 112 in order to control and secure the integrity of the production wellbore and prevent the uncontrolled release of production fluids, such as shale gas, from the borehole 116.
During hydrocarbon extraction, geothermal well operation, or fracking activities some contaminants may leak from the production zone 106 and migrate upwards around the borehole 116. The flow of these contaminants may occur between the production pipe 114 and the cement, the cement and the surrounding borehole 116, and/or in the rock surrounding the borehole 116. It will be appreciated that the contaminants may be released and continue to migrate upwards along the production pipe 114 both during and after the hydrocarbon extraction, geothermal or fracking activities have ceased. It will also be appreciated that these contaminants may include excess methane gas (coal seam gas) or carbon dioxide gas.
In some circumstances, leakage of the contaminants may be due to poor sealing between the production pipe 114 and the surrounding rock wall of the borehole 116. In other circumstances, this may be due to deterioration or failure of the production pipe 114 or fracturing of the cement over time or due to the natural movements of the rock strata surrounding the borehole 116 or seismic activity. Alternatively, rock strata around the production pipe 114 may be fractured or permeable thereby creating a path for leaking gas. Some exemplary pathways of contaminant gas will be described in further detail in relation to
Located in proximity to the production wellbore 111 is one or more remediation wellbores 125 for capturing contaminants escaping from the production zone 106. The one or more remediation wellbores 125 may be located at any suitable distance from the production wellbore 111, for example, to maintain the structural integrity of the production wellbore 111 during drilling of the one or more remediation wellbores 125. For example, a remediation wellbore 125 may be located at a distance of 2-4 meters, 4-8 meters or 8-12 meters from the production wellbore 111. Where a plurality of production wellbores exist, one or more remediation wellbores may be associated with each production wellbore. In another embodiment, a plurality of boreholes may be associated with a remediation wellbore 125.
The remediation wellbore 125 includes a remediation well head 126 from which a remediation pipe 128 extends into a borehole 130 that passes through the underground formation 102 towards the semi-permeable layer 108 located below water permeable layer 104 which may include an aquifer and impermeable layer 105. Cement 131 is provided in the annulus surrounding the remediation pipe 128 and the borehole 130.
The remediation wellhead 126 includes similar components as those described in relation to production wellhead 112 including a seal arrangement, a blowout preventer, choke line and kill line. The remediation wellhead 126 may also be located at the surface or in a subsurface pit. The remediation wellhead 126 may be located in the same subsurface pit 118 associated with the production wellbore 111 or be located in a separate subsurface pit 132 as shown, for example, in
The remediation wellbore 125 may be located at any suitable depth below the water permeable layer 104. In one example, the remediation wellbore 125 may be located at a depth of any of 1-25 meters, 1-20 meters, 1-15 meters, 1-10 meters or 1-5 meters below the water permeable layer 104. The depth below the water permeable layer is dependent on the type and depth of the geological layers of the geological formation. Typically the wellbore will extend through and below any impermeable layer 105 directly beneath the water permeable later into an underlying semi-permeable layer 108. It will be appreciated that by positioning the remediation wellbore 125 below the water permeable and impermeable layers 104 and 105, for example, in semi-permeable layer 108 or impermeable fractured layer 110, contaminants may be captured before they enter the water permeable layer 104.
The contaminants escaping from the production zone 106 rise upwards through the remediation wellbore 125 where they are captured at the remediation wellhead 126. In one embodiment, the contaminants captured at the remediation wellhead 126 are piped into outlet pipe 134 or a downstream line associated with the production pipe 114. In this embodiment, the contaminant gas from remediation wellbore 125 combines with the gases extracted from the production wellbore 111 and are directed downstream for further filtering, processing, transport and/or storage.
In another embodiment, the contaminants captured at the remediation wellhead 126 are directed to gas filtration assembly via outlet pipe 134. In the embodiment shown in
In a further embodiment, a mechanical pump may be used in addition or as an alternative to assist in the extraction of filtered gases and/or contaminants. In one embodiment, the filtered gases may be piped to outlet pipe 122 associated with the production pipe 114 where they combine with the gases extracted from the production wellbore 111 for further processing downstream. In another embodiment, the filtered gases may be stored in a storage tank 140 for transport and further processing.
In some embodiments, one or more filtering assemblies may be provided in the remediation wellbore 125 to capture contaminants from the production zone 106 including solid, liquid and/or gaseous contaminants. Exemplary filter assemblies include those described in PCT application no PCT/AU2018/050353 (WO 2018/191783) filed on 19 Apr. 2018 and PCT application no PCT/AU2015/050271 (WO 2015/176139) filed on 22 May 2015, the contents of which are incorporated herein by reference in their entirety.
In some embodiments, the remediation wellbore 125 may be provided with a funnel 142 for directing contaminants into the remediation wellbore. In one embodiment, the funnel 142 is bolted or welded to the remediation pipe 128 prior to the remediation borehole 130 being drilled. Stiffeners may also provided between the lowermost portion of the remediation pipe 128 and the funnel 142 to reduce the vertical load of the remediation pipe 128. In one example, the funnel 142 of the remediation wellbore 125 has a diameter of 25-60 centimetres where it engages the remediation pipe 128 and a diameter of 1-1.5 meters, 1.1-1.3 meters, or approximately 1.2 meters at its opposite end. The remediation pipe 128 may also have a larger diameter than the production pipe 114. It will be appreciated that the larger diameter of the remediation pipe 128 may permit greater capture of contaminants from the underlying rock formation as it provides a less resistive escape path.
In one embodiment, the funnel 142 is a single component. In this embodiment which is shown in
The gas filtration assembly 300 includes one or more banks of filter modules whereby each bank has one or more filtration stages with each stage including one or more filter modules connected in series by lower and upper manifolds. In the embodiment shown in
Referring to the embodiment shown in
The inlet of each filter module of the first filtration stage may be connected to an inlet pipe 424 for receiving contaminant gas extracted from the remediation wellbore 125 and the outlet of each filter module of the last filtration stage may be connected to an outlet pipe 426 for transmitting filtered gases to pipe 138.
Inlet pipe 424 may be provided with a valve diverter 428 for selectively diverting contaminant gases extracted from the remediation wellbore 125 to each bank 302a,b of filter modules. In the example shown in
The filter modules of each filtration stage may be provided with chemical and/or physical filter media for filtering gaseous contaminants. The type of physical and/or chemical filter media located in the filter modules may depend on the type of contaminants leaking from the production zone and/or the stage of filtration. In one example, the filter modules may house a bed of activated carbon to remove contaminants using chemical absorption. In another example, the filter modules may house a bed of zeolite such as zeolite clinoptilolite to remove contaminants, for example, ammonium, iron and manganese. In another example, the filter modules may house a bed of chemicals to remove contaminants such as benzene, toluene, xylene and volatile organic compounds using chemical reactions. In another example, filter modules of the first and second filtration stages are provided with a bed of activated carbon, while the filter modules of the third and fourth filtration stages are provided with a bed of zeolite. Additionally or alternatively, the housing of each filter module may be provided with one or more apertured structures to assist in replacing the chemical and/or physical media within the housing. In one example, the apertured structure may be a rigid basket and in another example the apertured structure may be a mesh bag suitably shaped and dimensioned to reside within the filter module housing.
One or more sensors may be coupled to one or more of the filter modules 406a-e, 408a-e, 414a-e and 418a-e, manifolds 410a-j, 416a-j and 420a-j and/or central conduits 412, 417, 422 for detecting one or more conditions of the filter module and/or the surrounding environment. The one or more sensors are connected to the control system 303 via sensor lines 421. In one example, each filter module 406a-e, 408a-e, 414a-e and 418a-e is provided with a first and second sensor for detecting the respective composition and concentration of the gases prior to, and post, filtration. In another example, each filter module may be provided with a sensor to detect the saturation of the filter media and provides an indication of when the filter module requires replacing. In another example, each filter module may be provided with a sensor to detect whether a user has attempted to remove the filter module from the respective filter bank or access the contents of the module.
In embodiments where two or more banks of filter modules are used, each bank of filter modules may be releasably connected to each other. In the example, shown in
The filter modules may be any suitable shape and arranged in any suitable configuration to form a filter bank. In the embodiments shown in
The operation of system 100 for capturing contaminants released from an underground formation 102 will now be described with reference to
At step 602, a suitable location of the remediation borehole 130 is determined that is in proximity to the production wellbore 111 and the borehole 130 is drilled from the surface to a desired depth below the water permeable layer 104 based on the above-described factors. The depth may be determined using GIS mapping data, as well as well drill monitor and depth tracking sensors. In some embodiments, the remediation borehole 130 may be drilled after the production wellbore 111 has been completed, for example, while the production wellbore is in production or after it has been abandoned. In some embodiments, the remediation borehole 130 may be drilled during completion of the production wellbore 111.
At step 604, the remediation pipe 128 and funnel 142 are inserted through the borehole 130. It will be appreciated that drilling of the remediation borehole 130 and insertion of the remediation pipe 128 may be completed together, for example, using Casing-while-Drilling techniques or separately. In some embodiments, reverse circulation mud rotary drilling may be used to drill the borehole. Reverse circulation drilling may minimise or avoid the risk of an explosion during drilling in an environment where there is methane gas. The remediation pipe 128 may be completed separately or together with reverse circulation drilling.
It will also be appreciated that the remediation borehole 130 is drilled at a greater diameter than the remediation pipe 128 and funnel 142. In one example, the borehole 130 is drilled with a diameter of approximately 1.5 meters or less and a remediation pipe 128 having a diameter of approximately 60 centimetres and a funnel 142 having a maximum diameter of 1.2 meters is used.
Once the desired depth below the water permeable layer 104 has been reached at step 606, the remediation pipe is cemented in place (step 608). In one example, the desired depth is when the funnel 142 is located at the transition between the impermeable layer 105 and underlying semi-impermeable layer 108. In another example, the desired depth is when the funnel 142 is located approximately 1-5 meters below the transition between the water permeable layer 102 and the underlying impermeable layer 105. Steps 602-606 may be repeated until a desired depth below the water permeable layer 104 has been reached.
At step 610, the remediation wellhead 126 is completed. Completion of the remediation wellhead 126 may include sealing the remediation borehole 130 and attaching a blowout preventer, a choke line and a kill line, installing the filtering assembly and connecting the remediation wellhead 126 to the filtering assembly 136 and vacuum source 124.
In the embodiments shown in
In some embodiments, when the gas filtration assembly 300 located in the container 136 becomes saturated with contaminants, pipes 134 and 138 are disconnected from respective inlet 424 and outlet 426 pipe of the gas filtration assembly and the container 136 is lifted from the sub-surface pit 703 by the lifting and lowering system 704 onto a transport vehicle 714 for downstream processing and storage. A replacement container, including a replacement gas filtration assembly 300, may then be lowered into the sub-surface pit 714 from a transport vehicle by the lifting and lowering system 704 and pipes 134 and 138 are connected to the respective inlet 424 and outlet pipe 426 of the gas filtration assembly 300.
It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021902977 | Sep 2021 | AU | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AU2022/051114 | 9/15/2022 | WO |
