Mercury injection is one of the efficient methods for investigating pore geometry of reservoirs.A lot of capillary curves from mercury apparatus have been accumulated in an oil field in northwest China.The most important parameter for estimating pore geometry in resevoirs

which is called Gg

has been found out by multivariated analysis combined with geological studies.It can be used to estimate the mode of pore geo-metry of reservoir rocks.It is found that

the smaller the value of Gg

the better is the pore geometry and vice versa.Gg can also be used tohelp estimate the water advance of water driving pools or injection exp-loitation.Thus

it is a useful parameter in exploitation analysis.Onthe basis of our observation of the relationship between Gg

porosityand permeability

a polynomial has been suggested for estimating the Ggvalue and a simple formula is obtained by means of regression.