High standard and strict requirement for bulk sealing off system have been determined by nature of easily loss of natural gas.Evaluation of the thinking shall be guided by the theory of board bucket(wooden bucket effect) and more attention shall be paid to the decisive role of locality over bulk in particular.With distinction between sealing off of natural gas and petroleum

emphasis must be placed on stereo and effectiveness when mentioning intension of bulk sealing off system.practical oil and gas exploration in eastern and northeastern Sichuan indicates that overpressure-static pressure fluid system in the lower part(Mesozoic-Palaeozoic) and high pressure-static pressure fluid system in the upper part(Mesozoic-Cenozoic) jointly constitute the stereo of bulk sealing off system

in fact a combined-sealing off system is composed of physical property

concentration and pressure.Effectiveness is decided by(1).buried depth;(2).regional hydro-dynamics;(3).late uplift;(4).time limit of uplift.Stereo is constitution and effectiveness is reconstruction

only by putting these two into one

can maximum function of bulk sealing off system be fully brought into play.