Downhole separator for use in a subterranean well and method

A downhole separation apparatus for a formation fluid having a plurality of constituents each having a different density characteristic, the downhole separation apparatus comprising:

• a separation chamber having an input for the formation fluid, a production output, and a disposal output, said separation chamber having an associated residence time for quiescently separating at least a first and a remainder constituent of the plurality of constituents from the formation fluid;
• an input flow regulator coupled to said input of said separation chamber and responsive to a level of the formation fluid in said separation chamber by flowing the formation fluid from a subterranean formation into said separation chamber;
• a production regulator coupled to said production output of said separation chamber and responsive to a level of said first constituent separated from the formation fluid by flowing the first constituent from said separation chamber and toward a well surface;
• and
• a disposal regulator coupled to said disposal output of said separation chamber and responsive to a level of said remainder constituent from the formation fluid by flowing the remainder constituent from said separation chamber to a disposal layer below said separation chamber.

Apparatus for fluid separation in a downhole environment, the apparatus comprising:

• a separation chamber defined by an under-reamed portion of a well bore whereby said under-reamed portion is defined by large bore drilling, said separation chamber for receiving and for quiescently separating a production fluid from the well bore having at least a first constituent with a first density and a second constituent with a second density sufficiently greater than said first density such that said at least first constituent and said second constituent have a tendency to separate over time in the presence of a gravitational force;
• and
• a fluid separator received through said chamber, said separator including an input unit defining a first flow passage in fluid communication with said separation chamber through an input flow regulator, said input flow regulator being responsive to a density property of said production fluid for regulating said production fluid from said flow passage into said chamber with respect to a level of said production fluid;
• a fluid production unit defining a second flow passage in communication with said chamber, said production unit having a production flow regulator responsive to a density property of said first constituent of said production fluid for regulating a flow of said first constituent into said second flow passage, said second flow passage being buffered from said first flow passage;
• and
• a fluid disposal unit in communication with said chamber and having a valve responsive to a density property of said second constituent for regulating said second constituent within said disposal portion for conveying said second constituent through a third flow passage to a disposal zone within said downhole environment and below said chamber.

A method for separating a production fluid downhole, the method comprising the steps of:

• flowing a production fluid from a subterranean formation into a separation chamber;
• quiescently separating the production fluid into a plurality of constituent layers over a residence time period determined as a function of a volume of the separation chamber, each constituent of the plurality of constituent layers having a different density property;
• lifting at least a first constituent of the plurality of constituents from the separation chamber by injecting under pressure a second constituent of the plurality of constituents into the first constituent, the second constituent being more dense than the first constituent;
• and
• disposing a remainder constituent of the plurality of constituents to a disposal layer in the subterranean formation.