METHOD AND APPARATUS FOR FREEZE-THAW WELL STIMULATION USING ORIFICED REFRIGERATION TUBING

摘要

A method and apparatus for introducing refrigerant into a wellbore, for freeze-fracturinga selected region of a subsurface formation, uses refrigerant diffuser pipehaving multiple orifices in a selected pattern along a designated section ofits length. Theorificed supply tubing is disposed within a refrigerant return conduit,thereby forming atubing annulus. A flow of liquid refrigerant is introduced into the diffuserpipe and flowsthrough the orifices into the tubing annulus, with the orifices acting asexpander meanscreating a pressure drop and causing vaporization of the refrigerant as itpasses into theannulus. To facilitate use of the same diffuser pipe in different wells havingdifferentrequirements, a helical orifice-isolation wrap may be disposed around thediffuser pipe,with the orifice-isolation wrap having orifice-plugging elements arrayed toeffectivelyblock fluid flow through selected orifices, while leaving other orifices openas required.In this way, it is possible to design diffuser pipes with particular orificearrangements thatwill accommodate two or more different isolation wraps, with each differentwrapplugging different patterns of orifices.