CO2 CO2 and H2S geological sequestration EOR History of engineering & technology L80-1 steel Technology: general issues WAG acid gas acid gas migration acid gas reinjection adhesion aggressive natural gas components annular space borehole cleaning borehole sealing efficiency bottomhole sampling capillarity carbonate reservoir cement sheath cement slurry cement stone cementing chrome coating cleaning the borehole cluster analysis corrosion resistance drilling fluids drilling mud emulsifier emulsion stability