Methods for fraccing oil and gas wells

Abstract

A method for stimulating or fraccing an oil or a natural gas well by adding a liquefied hydrocarbon such as liquid petroleum gas and liquefied natural gas, a proppant and a diluent such as carbon dioxide, nitrogen or mixtures thereof to the well. The order of addition is typically liquefied hydrocarbon then diluent but this order can be reversed and in other circumstances the liquefied hydrocarbon and diluent can be mixed together and fed to the well as a mixture.

Having thus described the invention, what we claim is: 
     
         1 . A method for stimulating an oil or a natural gas well comprising adding to the well a combination comprising a liquefied hydrocarbon selected from the group consisting of liquid petroleum gas and liquefied natural gas, a proppant and a diluent selected from the group consisting of carbon dioxide, nitrogen and a mixture of carbon dioxide and nitrogen. 
     
     
         2 . The method as claimed in  claim 1  wherein the oil or natural gas well is in a shale gas formation. 
     
     
         3 . The method as claimed in  claim 1  wherein natural gas and natural gas liquids are recovered from the oil or natural gas well. 
     
     
         4 . The method as claimed in  claim 1  wherein the well is a horizontal well. 
     
     
         5 . The method as claimed in  claim 1  wherein the combination is added to the well sequentially. 
     
     
         6 . The method as claimed in  claim 1  wherein the liquefied hydrocarbon is added to the well first, followed by the diluent. 
     
     
         7 . The method as claimed in  claim 1  further comprising adding water to the well along with the liquefied hydrocarbon. 
     
     
         8 . The method as claimed in  claim 1  wherein the water and liquefied petroleum gas is first added to the well, followed by natural gas, followed by nitrogen. 
     
     
         9 . The method as claimed in  claim 1  wherein sufficient time is allowed for between feeding the liquefied hydrocarbon to the well before feeding the diluent to the well. 
     
     
         10 . The method as claimed in  claim 1  wherein the liquefied hydrocarbon and the diluent are fed to the well together. 
     
     
         11 . The method as claimed in  claim 1  wherein the diluent is added to the well before the liquefied hydrocarbon. 
     
     
         12 . The method as claimed in  claim 1  wherein the liquefied hydrocarbon is fed to the well at a pressure of 5000 to 10,000 psig. 
     
     
         13 . The method as claimed in  claim 1  wherein the liquefied hydrocarbons are fed to the well at a first pressure and increased in pressure by the addition of a higher pressure diluent. 
     
     
         14 . The method as claimed in  claim 1  wherein the liquefied hydrocarbon is in gel form. 
     
     
         15 . The method as claimed in  claim 1  wherein the proppant is selected from the group consisting of silica sand, resin-coated sand and man-made ceramics.