Method of hydrocarbon recovery

Abstract

A method is given for treating a wellbore to increase the production of hydrocarbons from a subterranean formation penetrated by a wellbore, involving a period of injecting into the formation an aqueous injection fluid having a different chemical potential than the aqueous fluid in the formation. If there is water blocking, an osmotic gradient is deliberately created to cause flow of water into the injected fluid; hydrocarbon is then produced by imbibition. If the pore pressure in the water-containing pores in the formation is too low, an osmotic gradient is deliberately created so that water flows from the injected fluid into the water-containing pores, increasing the pore pressure and facilitating hydrocarbon production by imbibition. The method may be repeated cyclically. A semipermeable membrane may be created to enhance the osmosis. Wetting agents may be used to influence imbibition.

1 . A method of producing hydrocarbon from a subterranean formation penetrated by a wellbore comprising a period of injecting into the formation an aqueous injection fluid, other than a fracturing fluid or a pad, having a higher chemical potential than the aqueous formation fluid, wherein water in the injection fluid flows into the formation fluid by osmosis, whereby there is an increase in pressure in the formation, and whereby a portion of the hydrocarbon flows to the wellbore, and further wherein, if the formation is hydraulically fractured, the volume of aqueous injection fluid having a higher chemical potential than the aqueous fluid in the formation is greater than the volume of the hydraulic fracture plus the volume of any natural fractures contacted plus the volume leaked off during the hydraulic fracturing treatment. 
   
   
       2 . The method of  claim 1  wherein the injection fluid contacts at least one quarter of the practical wellbore drainage volume. 
   
   
       3 . The method of  claim 1  wherein injection is performed in different places in the formation. 
   
   
       4 . The method of  claim 1  wherein the period of injection is followed by a period of production without injection. 
   
   
       5 . The method of  claim 4  wherein the period of production without injection is followed by a second period of injection. 
   
   
       6 . The method of  claim 1  further comprising injecting a semipermeable-membrane forming material in an amount sufficient to form a semipermeable membrane. 
   
   
       7 . The method of  claim 1  wherein the injection fluid comprises formate. 
   
   
       8 . The method of  claim 1  wherein the injection fluid further comprises an agent that increases the contact angle of the formation with water. 
   
   
       9 . The method of  claim 1  wherein the injection fluid further comprises an agent that decreases the contact angle of the formation with water. 
   
   
       10 . The method of  claim 1  wherein the osmotic pressure generates fractures in the formation. 
   
   
       11 . The method of  claim 1  wherein the formation is hydraulically fractured. 
   
   
       12 . (canceled) 
   
   
       13 . A method of producing hydrocarbon from a subterranean formation penetrated by a wellbore comprising injecting into the formation an aqueous injection fluid, other than a fracturing fluid or a pad, having a lower chemical potential than the aqueous formation fluid, wherein a portion of the water in the formation fluid flows into the injection fluid by osmosis, whereby a portion of the hydrocarbon flows to the wellbore, and further wherein, if the formation is hydraulically fractured, the volume of aqueous injection fluid having a lower chemical potential than the aqueous fluid in the formation is greater than the volume of the hydraulic fracture plus the volume of any natural fractures contacted plus the volume leaked off during the hydraulic fracturing treatment. 
   
   
       14 . The method of  claim 13  wherein the injection fluid contacts at least one quarter of the practical wellbore drainage volume. 
   
   
       15 . The method of  claim 13  wherein injection is performed in different places in the formation. 
   
   
       16 . The method of  claim 13  wherein the period of injection is followed by a period of production without injection. 
   
   
       17 . The method of  claim 16  wherein the period of production without injection is followed by a second period of injection. 
   
   
       18 . The method of  claim 13  further comprising injecting a semipermeable-membrane forming material in an amount sufficient to form a semipermeable membrane. 
   
   
       19 . The method of  claim 13  wherein the injection fluid comprises formate. 
   
   
       20 . The method of  claim 13  wherein the injection fluid further comprises an agent that increases the contact angle of the formation with water. 
   
   
       21 . The method of  claim 13  wherein the injection fluid further comprises an agent that decreases the contact angle of the formation with water. 
   
   
       22 . The method of  claim 13  wherein the osmotic pressure generates fractures in the formation. 
   
   
       23 . The method of  claim 13  wherein the formation is hydraulically fractured. 
   
   
       24 . (canceled) 
   
   
       25 . A method of producing hydrocarbon from a subterranean formation penetrated by a wellbore comprising injecting into the formation an aqueous injection fluid having the same chemical potential as the aqueous fluid in the formation, whereby no osmotic pressure gradient is created, and whereby a portion of the hydrocarbon flows to the wellbore. 
   
   
       26 . The method of  claim 25  wherein the injection fluid contacts at least one quarter of the practical wellbore drainage volume. 
   
   
       27 . The method of  claim 25  wherein injection is performed in different places in the formation. 
   
   
       28 . The method of  claim 25  wherein the period of injection is followed by a period of production without injection. 
   
   
       29 . The method of  claim 28  wherein the period of production without injection is followed by a second period of injection. 
   
   
       30 . The method of  claim 25  further comprising injecting a semipermeable-membrane forming material in an amount sufficient to form a semipermeable membrane. 
   
   
       31 . The method of  claim 25  wherein the injection fluid comprises formate. 
   
   
       32 . The method of  claim 25  wherein the injection fluid further comprises an agent that increases the contact angle of the formation with water. 
   
   
       33 . The method of  claim 25  wherein the injection fluid further comprises an agent that decreases the contact angle of the formation with water. 
   
   
       34 . The method of  claim 25  wherein osmotic pressure is used in a separate step to generate fractures in the formation. 
   
   
       35 . The method of  claim 25 , wherein the formation is hydraulically fractured. 
   
   
       36 . The method of  claim 35 , wherein the volume of injected fluid is at least the volume of the hydraulic fracture.