Downhole separation of carbon dioxide from natural gas produced from natural gas reservoirs

A system for the production, through a completed well traversing a formation, of natural gas from a production layer in the formation containing natural gas and carbon dioxide, and for sequestration of the carbon dioxide into a sequestration layer in the formation comprising:

• at least three substantially parallel tubes located in the well, said at least three substantially parallel tubes including two packed pressure swing adsorption (PSA) beds and at least one tube for purified compressed carbon dioxide;
• a compressor coupled to said at least one tube for purified compressed carbon dioxide and to said PSA beds;
• a plurality of valves at least some of which are located in the completed well, a first of said valves coupled to a middle portion of a first of said PSA beds and to the production layer, a second of said valves coupled to a middle portion of a second of said PSA beds and to the production layer, a third of said valves coupled to a first of said PSA beds and to said compressor, and a fourth of said valves coupled to a second of said PSA beds and to said compressor, wherein at any given time, one of said two PSA beds produces purified natural gas, and the other of said two PSA beds produces purified carbon dioxide;
• and
• means associated with said tube for purified compressed carbon dioxide for directing said purified carbon dioxide into the sequestration layer of the formation.

A method for separating a mixture of carbon dioxide and natural gas produced from a natural gas reservoir in a formation traversed by a completed well and having a sequestration layer, comprising:

• providing a dual reflux pressure swing adsorption (PSA) system with two packed PSA beds contained in PSA tubes having top, middle, and bottom portions;
• locating said two packed PSA tubes and at least one additional tube in the well;
• maintaining said two packed PSA beds at different pressures relative to each other during operation;
• providing each middle portion of said PSA beds one at a time with the mixture of the carbon dioxide and natural gas from the reservoir, wherein said PSA beds generate purified carbon dioxide and purified natural gas from the mixture, and providing the top portions of said PSA beds one at a time with some of at least one of said purified natural gas and said purified carbon dioxide, and the bottom portions of said PSA beds one at a time with at least some of the other of purified natural gas and purified carbon dioxide;
• obtaining said purified natural gas at a surface of the formation;
• and
• piping said purified carbon dioxide through said at least one additional tube for sequestration in the sequestration layer.