Abstract: In the Liaozhong sag,Bohai Sea,complex fault zones give rise to numerous secondary accommodation normal faults,which form and control a large number of fault block traps.Well data have confirmed that the vertical oil migration ability of source tapping faults,which connect mature source rocks with fault block traps located on top of it,is of great importance to abundance of oil and gas accumulation in these traps.The study regards that the geometry of source tapping fault's surface and its contact area within the mature source rocks control the oil and gas migration.Thus,the seismic data are used to elaborately interpret source tapping faults,to depict the three-dimensional geometry of fault section and its contact area within mature source rocks.Under the control of the above two geological factors,the migration ability was estimated by numerical simulation,and combined with logging data,we identified fault-associated fracture zones.Thus the model of oil and gas migration in LD oilfield is established based upon these results.The results are as follows:The oil migration ability of the six studied source tapping faults varies significantly.There are 24 charging points to the oil reservoir of the oilfield with diverse contributions,and result in different reserve abundance in different fault blocks.The intensity of associated fracture zone of the source tapping fault is different on either walls of the fault,with the better developed fractures and improved porosity and permeability near the downthrown side,where the selective hydrocarbon migration from the charging points occurs.And based on these results,we established the migration model of oil and gas in the study area,which matches well with the actual drilling results.

Key words: oil migration ability, migration model, quantitative evaluation, complex fault zone, oil source tapping fault, LD oilfield, Liaozhong sag