Patent ID: 7775281

Claim:
A method for stimulating flow of petroleum fluids from a subsurface formation into a wellbore drilled into and exposed to the formation, said method comprising the steps of: (a) providing a string of return tubing having an upper end and a lower end; (b) providing a string of supply tubing having an upper end and a lower end, said lower end being open, and said supply tubing having expander means associated with said lower end; (c) disposing the return tubing string within the wellbore so as to position the lower end of the return tubing at a selected depth, and so as to form a well annulus between the return tubing and the wellbore; (d) disposing the supply tubing string within the return tubing string so as to position the expander means at a selected depth, and so as to form a tubing annulus between the supply tubing and the return tubing, with the return tubing string having associated plug means sealing off the tubing annulus at a selected location below the expander means, and further having flow restrictor means disposed within the tubing annulus at a selected distance above said plug means; (e) ensuring that an aqueous fluid is present in the well annulus to a selected level, and that said aqueous fluid can flow into fissures in adjacent regions of the formation; (f) initiating a freezing cycle by introducing a flow of liquid refrigerant into the supply tubing, such that the refrigerant passes through the expander means and resultantly vaporizes and flows into the tubing annulus, and continuing the flow of refrigerant to freeze the aqueous fluid in a zone within the well annulus adjacent the portion of the return tubing string between said plug means and said flow restrictor means, and to freeze aqueous fluid within an adjacent first region of the formation; and (g) initiating a thaw cycle by discontinuing the flow of refrigerant and allowing said first region of the formation to thaw; and (h) introducing LF wave energy into the formation in association with the freezing cycle; wherein the freezing of aqueous fluid within the adjacent first region of the formation creates expansion pressures promoting enlargement of fractures pre-existing in said first region of the formation.