Ground property adjustment method and hydrocarbon recovery method using the same

Abstract

A ground property adjustment method characterized by: solidifying the ground by proliferating microorganisms, in the ground, that are capable of producing a biological membrane (biofilm), have urease activity, and can cause calcium ions to precipitate as calcium carbonate through decomposition of urea by the urease activity. Microorganisms may precipitate calcium carbonate on the surface of a biological membrane by incorporating carbon dioxide in the environment.

What is claimed is: 
     
         1 . Aground property adjustment method comprising:
 solidifying the ground by proliferating microorganisms, in the ground, that are capable of producing a biological membrane, have urease activity, and can cause calcium ions to precipitate as calcium carbonate through decomposition of urea by the urease activity.   
     
     
         2 . The ground property adjustment method according to  claim 1 , wherein the microorganisms precipitate calcium carbonate on a surface of the biological membrane by incorporating carbon dioxide in the environment. 
     
     
         3 . The ground property adjustment method according to  claim 1 , wherein, as the microorganisms, at least one of  Sporosarcina newyorkensis  species,  Staphylococcus hominis  species,  Lysinibacillus fusiformis  species,  Sporosarcina pasteurii  species, or  Sporosarcina aquimarina  species is proliferated in the ground. 
     
     
         4 . The ground property adjustment method according to  claim 1 , wherein, as the microorganisms,  Staphylococcus hominis  species or  Lysinibacillus fusiformis  species is proliferated in the ground. 
     
     
         5 . The ground property adjustment method according to  claim 1 , further comprising:
 injecting a nutrient salt containing a calcium source into the ground before or during proliferating the microorganisms.   
     
     
         6 . The ground property adjustment method according to  claim 1 , further comprising:
 injecting casein dissolved under alkaline conditions derived from ammonia produced by hydrolysis reaction of urea into the ground.   
     
     
         7 . The ground property adjustment method according to  claim 1 , wherein the microorganisms produce organic acids, and the organic acids promote uptake of calcium ions by the microorganisms. 
     
     
         8 . A hydrocarbon recovery method using a ground property adjustment method which solidifies the ground by proliferating microorganisms, in the ground, that are capable of producing a biological membrane, have urease activity, and can cause calcium ions to precipitate as calcium carbonate through decomposition of urea by the urease activity, the hydrocarbon recovery method comprising:
 a first injecting of injecting a culture medium for proliferating the microorganisms into a production well;   a second injecting of injecting the urea into the production well;   proliferating the microorganisms;   decompressing the production well after the first injecting, the second injecting, and the proliferating; and   recovering hydrocarbons from the production well.