FACTOR ANALYSIS ON THE PORE TESTURE OF THE TIGHT SANDSTONES IN THE LONGTAN FORMATION(JIANGSU)

The clastic type of tight sandstones is dominantly made up by feldspathic lithic quart-zose sandstone with fine grain size rather than feldspathic litharenite,As for fine-micro-throat tight sandstones,samples with value of Φ fewer than 5% occupy 63%of the total,those with value of K fewer than 0.1×10^-3μm occupy 78%,and the value of R_M is 0.007to 0.472μm,A part of porous parameters have good correlations among themselves,butthey have no correlation to the parameters of conventional physical property or even far.With the assistance of R-factorQ-factor analysis,we select the parameters to evaluatethe quality of pore structure,and set the standard with the value of R_M more than 0.15μmand the value of C fewer than 0.45 to ascertain(poor)reservoir rocks.The(poor)reser-voir rocks are mainly medium-grained and partly fine-grained quartzose sandstone of in- creased interstice─feldspathic solution opening,and generally have fair-level oil showswhich are common in Zhenjiang Coal Mine and Yixing Chuanbu region,Therefore it is be-lieved these two areas should be good prospecting targets for exploration.