Selective hydrate production with co2 and controlled depressurization

Abstract

The present invention relates to an improved method for recovering hydrocarbons trapped in hydrate formations.

1 . A method for the producing hydrocarbons from a subterranean formation containing gas hydrates, the method comprising:
 a. drilling a well into a subterranean formation;   b. introducing a releasing agent into the well in a controlled manner to partially depressurize the well, wherein the releasing agent is more thermodynamically stable than the gas hydrates present in the formation;   c. causing the releasing agent to contact the gas hydrates, thereby releasing the hydrocarbons in the well without melting the gas hydrate;   d. selectively substituting the releasing agent for the hydrocarbons to thereby release the hydrocarbons from solid-state hydrate structure s without melting the gas hydrates, thereby providing substituted hydrates comprising the releasing agent bound with the solid-state hydrate structures that form hydrates, thereby releasing the hydrocarbons into the well without melting the gas hydrates; and   e. reducing the pressure in the well to selectively dissociate the hydrates with a desired methane content.   
     
     
         2 . The method according to  claim 1 , wherein the releasing agent is selected from a group consisting of carbon dioxide, ethane, xenon, hydrogen sulfide, and mixtures thereof. 
     
     
         3 . The method according to  claim 1 , wherein the gas hydrate is a methane hydrate. 
     
     
         4 . A method for the producing hydrocarbons from a subterranean formation containing gas hydrates, the method comprising:
 a. drilling a well into a subterranean formation;   b. introducing a releasing agent into the well in a controlled manner to partially depressurize the well, wherein the releasing agent is more thermodynamically stable than the gas hydrates present in the formation, wherein the releasing agent is selected from a group consisting of carbon dioxide, ethane, xenon, hydrogen sulfide, and mixtures thereof;   c. causing the releasing agent to contact the gas hydrates, thereby releasing the hydrocarbons in the well without melting the gas hydrate;   d. selectively substituting the releasing agent for the hydrocarbons to thereby release the hydrocarbons from solid-state hydrate structure s without melting the gas hydrates, thereby providing substituted hydrates comprising the releasing agent bound with the solid-state hydrate structures that form hydrates, thereby releasing the hydrocarbons into the well without melting the gas hydrates; and   e. reducing the pressure in the well to selectively dissociate the hydrates with a desired methane content.   
     
     
         5 . The method according to  claim 5 , wherein the releasing agent is in liquid phase when contacted with the gas hydrates. 
     
     
         6 . The method according to  claim 5 , wherein the gas hydrate is a methane hydrate.