Methods of using a laser to perforate composite structures of steel casing, cement and rocks
AssigneeThe University of Chicago
InventorsClaude Reed, Zhiyue Xu
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Abstract
Apparatus and methods of using lasers are provided for the perforation of oil and gas well casings and rock formations. A rock removal process called laser spallation is provided that utilizes a combination of laser-induced thermal stress and laser induced superheated steam explosions just below the surface of the laser/rock interaction to spall or fracture the rock into small fragments that can then be easily removed from the rock formation. The use of high power laser beams of kilowatt level is provided to rapidly cut the steel casings and perforate into the formation. Techniques of the invention increase permeability and reduce hole tapering while perforating a deep hole in reservoir rock formations.
Claims12
A method for perforation of oil and gas well casings and rock formations utilizing a high power laser beam to perforate the casing, and cement and form penetrations into a rock formation to enhance the flow of gas and oil into the wells comprising the steps of:
- delivering a high power laser beam to a laser perforator located in a production zone of a borehole;
- bending, tilting and shaping the high power laser beam to the desired beam orientation and profile;
- providing a purging flow to move spalled rock fragments out of the hole and to create a stable clear path for the laser beam to reach the rock surface while perforating through wellbore liquid;
- focusing and offsetting the laser beam on the steel casing and rotating the focused laser beam to cut a hole through the steel casing;
- defocusing the laser beam by one-half diameter of the hole to be perforated and offsetting the laser beam by about one-half beam diameter from the center of the hole to be perforated and rotating the offset laser beam around the axis of the hole to perforate a hole into the cement and rock;
- the laser beam having an irradiance and rotation speed set for material removal by laser spallation and having a tilting angle set for minimum hole tapering.
Dependencies are inferred from the claim text.