THE CHARACTERISTICS OF MINERAL COMPONENTS FOR EFFECTIVE SOURCE ROCKS FROM DONGYING DEPRESSION OF BOHAI BAY BASIN AND ITS SIGNIFICANCE

The results of X-ray diffraction of effective source rocks in Dongying Depression of the Bohai Bay Basin show that the main mineral components of effective source rocks for Es^3(下) and Es^4(上) are quartz,feldspar,clay(illite and illite-smectite),carbonate(calcite and dolomite);the minor mineral components are pyrite,gypsum,anhydrite,mineral salt and brongniartine.This suggests that both source rocks are deposited in moderate deep or deep lacustrine facies with brinish,alkalic and strength reduction water body.The percent of smectite in illite-smectite(%S) of effective effective source rocks can quite truly reflect the thermal maturity of source rocks.The characteristics of mineral components for both source rocks are similar to the shale with high production of shale gas,that is rich in brittle minerals and lower in clay mineral.This means both source rocks in Dongying Depression are favorable to form fracture and can be fractured easily,and are also favorable to produce shale gas.The favorable places for prospecting and developing shale gas in Dongying Depression are at the main sag of Lijin and Minfeng.