Technical Petrophysics

COBRA (CO2 Borehole Research Apparatus)

Specially designed for the Investigation of the Borehole Tightness

To investigate the evolution of the tightness of cemented boreholes even under cyclic loading, two autoclave systems are used by the division of petrophysics. Both systems were designed for the former COBRA project and are currently used in the SUBI project.

COBRA I is the smaller system that consists of two autoclaves and a typical oilwell-casing filled with cement. Variations in temperature and pressure can be applied on the whole apparatus to simulate cyclic loading. The pressure buildup in the upper autoclave is used to determine potential leakage through the cemented casing for different loading cycles. This is analyzed and modeled by software developed for the experiment. Water circulation is also a possible option for experiments. Furthermore, rock samples can be placed inside the lower autoclave to investigate alteration.

The COBRA II is similar in its function, but the sample diameter is much larger. Therefore, it’s possible to investigate the tightness of large rock samples on a realistic scale. A hole can be drilled through the sample and filled with either cement or cement and a casing. Additionally, the application of confining and vertical stresses is possible.

For questions please contact Marcel Schulz.

 

  COBRA I COBRA II
Max. Temperature 150 °C 150 °C
Max. Pore Pressure 100 bar 70 bar
Max. Confining Stress - 80 bar
Max. Vertical Stress - 120 bar
Sample

Cemented Casing

(5.5" diameter, 2 m long)

Rock Sample with optional drilling

(56 cm diameter, 1.08 m long)

Mass 1.6 t 13 t

 

COBRA I without insulation. Orange heating matsare visible. Early version of the COBRA II without insulation.