Investigation of Using CO2 as Supercritical Drilling Fluid in Jet-assisted Mechanical Drilling

In Coiled Tubing Drilling (CTD) rate of penetration could be increased by providing high pressure fluid jets, however, effective jet erosion drilling requires pressures of at least 14500 psia. Carbon dioxide exists as a supercritical fluid with a density near the water and evident low viscosity at under the pressure and temperature conditions in oil and gas well CTD. These properties can enhance jet erosion and reduce dynamic confinement loads during drilling in a pressurized borehole. Jet-assisted erosion experiments carried out with CO2 and water inside a pressurized vessel, show that CO2 provides much faster cutting of shale and granite and the threshold pressure for jet erosion with CO2 is significantly lower and drilling rate is also much faster when CO2 is used. It can provide fast penetration at low bit-weight and torque and also low cost small-diameter coiled tubing in short-radius lateral drainage wells. A model of CO2 circulation through a CTD system shows that a choke manifold will provide complete control over formation pressures and cuttings transport should be superior to that of water.

Investigation of Using CO2 as Supercritical Drilling Fluid in Jet-assisted Mechanical Drilling Keywords:

Supercritical CO2 , Coiled Tubing Drilling (CTD) , Drilling Fluid