Contaminant extraction in a borehole

A system for contaminant extraction in a borehole extending from a surface of the Earth through a water permeable layer and into an underlying production zone, the system comprising:

• an outer casing located within the borehole and extending through the water permeable layer;
• a production pipe located within the outer casing and extending towards the production zone;
• a filter assembly, at least part of which occupies at least part of an intermediate zone between the outer casing and the production pipe, wherein the filter assembly is configured to capture contaminants before they enter the water permeable layer and/or before they are released into the atmosphere, the filter assembly comprising:
• a lower filtering stage configured to filter solid and liquid contaminants;
• and
• an upper filtering stage located externally of the borehole and configured to filter gaseous contaminants migrating from the production zone through the lower filtering stage;
• wherein the intermediate zone is sealed off to prevent the uncontrolled leakage of gaseous contaminants from the intermediate zone and the upper filtering stage is in fluid communication with the sealed off intermediate zone;
• and
• wherein the upper filtering stage comprises a plurality of serially connected replaceable non-perforated filter modules located in an underground or below ground pit adjacent to the borehole.

A system for contaminant extraction in a borehole extending from a surface of the Earth through a water permeable layer and into an underlying production zone, the system comprising:

• an outer casing located within the borehole and extending through the water permeable layer;
• a production pipe located within the outer casing and extending towards the production zone;
• a filter assembly, at least part of which occupies at least part of an intermediate zone between the outer casing and the production pipe, wherein the filter assembly is configured to capture contaminants before they enter the water permeable layer and/or before they are released into the atmosphere, the filter assembly comprising:
• a lower filtering stage configured to filter solid and liquid contaminants;
• and
• an upper filtering stage located externally of the borehole and configured to filter gaseous contaminants migrating from the production zone through the lower filtering stage;
• wherein the intermediate zone is sealed off to prevent the uncontrolled leakage of gaseous contaminants from the intermediate zone, and the upper filtering stage is in fluid communication with the sealed off intermediate zone;
• and
• wherein the lower filtering stage includes a plurality of alignment rollers configured to bear rotatably against the outer casing for facilitating raising and lowering of the lower filtering stage within the borehole.