Experimental investigation of free and forced gravity drainage in petroleum fractured reservoirs

Gas/oil gravity drainage takes place in the secondary gas cap, where the matrix is filled with oil and surrounded by gas-filled fractures. Oil will be produced into the fractures by gravity forces at a rate mainly governed by the density difference Δρ between oil and gas, matrix permeability k, the oil viscosity µo, the oil relative permeability kro, and the height of the gas/oil capillary transition zone H relative to the height H of draining oil column: ݍ ൌ ௞௞ೝ೚ܣ∆ߩ݃ሺ1 െு೎ ሻThe main goal of these experiments is qualitative and quantitative investigation of oil recovery by free gravity drainage and gas injection in various rates and the effect of block height on oil recovery. In free fall gravity drainage, oil is produced just by gravity forces, while after the gas injection, the pressure difference between two permeable zones, provides essential forces for displacing fluid into the low permeable zone and produce the remaining oil. All the experiments have been done using glass etched micromodel and the pictures have been recorded by camera.

Keywords:

Gas–oil gravity drainage , Micromodel , Gas injection , Fr cture , Matrix