LNG with ethane enrichment and reinjection gas as refrigerant

A process for producing liquefied natural gas from methane gas, wherein the process is carried out in the vicinity of a hydrocarbon producing reservoir having an associated natural gas liquids extraction apparatus comprising a demethanizer, the process comprising:

• supplying the methane gas for the process from an outlet of the demethanizer;
• cooling and expanding the methane gas;
• and
• separating liquefied natural gas from cold methane vapor.

An apparatus for producing liquefied natural gas from methane gas, comprising:

• means for cooling the methane gas;
• means for expanding the gas;
• means for separating liquefied natural gas from cold methane vapor;
• and
• a conduit to a methane gas inlet of the apparatus from a methane outlet of a demethanizer, the demethanizer being a component of a natural gas liquids extraction apparatus.

An apparatus for simultaneously producing liquefied natural gas and extracting natural gas liquids from a mixture of hydrocarbons, the apparatus comprising:

• a demethanizer for distilling the mixture to produce a methane overhead fraction and a demethanizer bottoms fraction;
• a turbo-expander for expanding and cooling the methane;
• a separator whereby the methane is separated into liquefied natural gas and cold methane vapor;
• a compressor for recompressing the cold methane vapor;
• and
• a conduit connected between the compressor and a producing hydrocarbon reservoir such that at least a portion of the compressed methane vapor is injected into the producing hydrocarbon reservoir.

A process for producing liquefied natural gas from a mixture containing methane, ethane, and heavier hydrocarbons, comprising:

• separating the hydrocarbon mixture into a methane-rich fraction and a methane-lean fraction;
• cooling and expanding the methane-rich fraction;
• separating the expanded methane-rich fraction into methane-rich liquid and methane-rich vapor, at least a portion of the methane-rich vapor accomplishing the cooling of the methane-rich fraction by heat exchange therewith;
• separating at least a portion of the ethane from the methane-lean fraction;
• cooling the ethane by heat exchange with at least a portion of the methane-rich vapor;
• combining the methane-rich liquid with the cooled ethane to form a product mixture;
• expanding the product mixture;
• separating the product mixture into a liquid product and a gas product;
• and
• recompressing the methane-rich vapor and reinjecting at least a portion of the recompressed vapor into a producing hydrocarbon reservoir.

A process for producing ethane-enriched liquefied natural gas from a mixture of hydrocarbons, comprising:

• distilling the mixture successively to produce a condensate product and a plurality of overhead products, one of the overhead products comprising methane and another comprising ethane;
• liquefying at least a portion of the ethane overhead product and a first portion of the methane overhead product to form a liquefied natural gas product;
• cooling the hydrocarbon mixture, the methane overhead product, and the ethane overhead product by heat exchange with a second portion of the methane overhead product;
• and
• recompressing the second portion and injecting at least part of the second portion into a producing hydrocarbon reservoir.

A process for separating a mixture of hydrocarbons comprising:

• (a) cooling the mixture by heat exchange with a cold methane stream;
• (b) distilling the cooled mixture in a demethanizer column to produce methane-rich and methane-lean fractions;
• (c) distilling the methane-lean fraction in a deethanizer column to produce ethane-rich and ethane-lean fractions;
• (d) cooling the methane-rich and ethane-rich fractions by heat exchange with the cold methane stream;
• (e) expanding the cooled methane-rich fraction;
• (f) separating the expanded methane-rich fraction to produce a first methane-rich vapor and a first methane-rich liquid;
• (g) mixing the first methane-rich vapor with a second methane-rich vapor to form the cold methane stream;
• (h) compressing the cold methane stream to form a compressed methane stream;
• (i) injecting a portion of the compressed methane stream into a producing hydrocarbon reservoir;
• (j) cooling and expanding the remaining portion of the compressed methane stream to form an incremental methane stream;
• (k) separating the incremental methane stream to produce the second methane-rich vapor and a second methane-rich liquid;
• (l) mixing the first and second methane-rich liquids with the cooled ethane-rich fraction to produce a product mixture;
• (m) expanding the product mixture;
• (n) performing a vapor-liquid separation of the expanded product mixture to produce fuel gas and liquefied natural gas.