DIAGENESIS AND PORE EVOLUTION OF MAWU_4~1 RESERVOIR IN JINGBIAN GASFIELD

In the Mawu 4 1 Member,Ordovician Majiagou Formation in Jingbian gasfield of northern Ordos Basin,its reservoir rock is composed of granular dolomite,coarse crystal dolomite and crystal dolomite;the reservoir space is mainly solution vug,and fractures are favorable channel to improve a reservoir-permeability capacity;the most important reservoirs in this study area are made up from vug-fractured and intergranular pore-fractured ones.Both compaction and pressure solution nearly make primary pore missing.However,dissolution in the exogeneous stage is important to form Mawu 4 1 Member.The largest secondary pore,which contributes to reservoir space better than primary pore,is formed by karstification at the end of Caledonian stage.These factors match together to from better gas reservoirs.