THE TECTONIC EVOLUTION AND RESERVOIR FORMATION IN WENLIU AREA, BOHAIWAN BASIN

Wenliu structure is an anticline caused by salt-gathering on the background of center mole track,it was formed from Es³⁽²⁾to Es².The extent of the trap is enlarged because of the salt-slumping of the wings.With the increase of the burial depth,C-P coal formation began its secondary hydrocarbon generating,and started migrating at depth of 4 000m for the first time.The main source rock was located in Wendong and Qianliyuan areas,with the depth of 5 200～6 300m.Micro-fracture-fault network was the main way for the coal-derived gas to migrate to the center mole track,the migration reached its peak at the age Ed (Ⅱ episode).In the trap,the gas prefered to entering the typeⅠand Ⅱreservoirs in Es^4(3-5)(the water-displacement rate is 73%～56%),then with the increase of the gas column and pressure,the gas began to enter the type Ⅲ of reservoir in Es^4(1-2 and Es^4(7-8),the final water-displacement rate is 40%.