Abstract:

Data derived from DST(Drill Strata Test)suggest that low pressure systems developed in Dongying Depression.The low pressure oil and gas reservoirs are usually located in the marginal uplift zone,marginal fault zone and central uplift zone.The low pressure system in the marginal uplift zone is shallower than 2000 m;in the central uplift zone,it is distributed in the strata deeper than 2000 m;and near the marginal fault zone,it developed in both shallow and deep strata.The distribution of low pressure was determined by the origin mechanesms.The main causes of the low pressure origins were diffusion of light hydrocarbons,pressure release resulting from quick fluid and hydrocarbon escape along faults and surfaces of unconformities,and osmosis due to salinity differences.The low pressure anomaly does not only exist in gas pools in the depression,but also in heavy oil pools and normal oil pools.

Key words: under pressure system, diffusion, pressure release, Dongying Depression