POROSITY AND PERMEABILITY OF PALAEOCENE SANDS FROM THE NORTH SEA;A COMPARISON OF PLUG POROSITY AND IMAGE DERIVED POROSITY

摘要

The relationship between porosity and permeability is traditionally used in the hydrocarbon industry to assist in flow prediction.For the Palaeocene sand reservoir discussed here this relationship is extremely poor.Consequently,image analysis has been used to try and understand the nature of the plug porosity-permeability plot.The image analysis parameter considered is image porosity.The images used for the image analysis process are back scattered SEM images(Figure 1a),at two different magnifications(x30 and x150).Image porosity expresses the two-dimensional pore space seen within an image as a fraction of image area(Figure 1b).Plug porosity,by comparison,is the calculation of three-dimensional interconnected pore space by helium injection.Both of these porosities have been compared with a gas permeability measurement.The permeability and plug porosity measurements are made on the same plug and the image porosity measurement is made from an endtrim of each plug.It should be noted that for the image porosity calculation the pores are not necessarily connected,and only pores greater than 13 μm~2 are counted.It is assumed that 13 images are representative of the entire plug.Forty-eight samples were studied.