Oil And Gas Migration Mechanism And Affects On Accumulation In West Slope Of Songliao Basin

Through the analysis of petroleum geology, geochemistry and testing data and the study of oil/gas formation, hydrochemical , hydrodynamic, fluid potential field, migration passages, geochemistry characters, migration directions and control factors , the numerical stimulation of migration pathway ,migration mode, how to control oil/gas distribution ,we can know the oil/gas migration directions, period and pathway along reservoir beds. At the same time, simulating oil/gas migration path numerically, and analyzing reservoir types, distribution laws and formation modes, we can confirm the control affects to oil/gas formation and distributing by migration. The research shows that the thicker the buried depth of the above sediments increases, the more precipitous the gradient of T1 reflection interface becomes, which reaches to the most between 65~70 Ma and the expulsion peak of hydrocarbon of source rocks also reached to the peak. In addition ,the structure background was offered by this increase of the gradient , so the cosmic hydrocarbon migration happened at this time . The main reservoir types of the West Slope can be listed as follow :anticline , up-skew lithologic pinchout ,structure-lithologic ,oil-lens, faults obstructed and unconformity. The hydrocarbon mainly congregates in GaoTai Zi oil reservoir and Sa Er Tu oil reservoir vertically while it mainly distributed around Tai Kang uplift zone .the Tai Kang uplift zone are mainly dominated by the anticline and structure-lithologic reservoirs , while the type of reservoirs in West Overlap zone are mainly up-skew lithologic pinchout and unconformity. There are three preponderant migrating directions for hydrocarbon in Gao Tai Zi reservoirs , four for hydrocarbon in SII , SIII reservoirs and three for S0 and Sâ… reservoirs. The characteristic of oil and gas migration in the West Slope is that oil and gas flowed to the north-west plentifully. The result of simulation showed that the middle of area is the main migration belt. The sands in the Gao Tai Zi oil layer developed and sand overlapped in the portrait easily or is connected by faults. Above all could help it improve transiting ability laterally. The single sand in the SII and SIII oil layer is thick, once it was overlapped in the portrait or connected by faults, the oil and gas could transit far. The sands in the S0 and SI oil layer are poor and lentoid, and disparts from each other , oil and gas could only transfuse into the sands through the faults. The affecting factors on distribution and accumulation of oil and gas in the West Slope are main the follows: Including the space position between oil migration path and traps, the area converging of centripetal flow and acentric flow, unconformities factor and faults factor, the structure evolvement of T1. Through searching mechanism of oil migration and oil accumulation in the West Slope. These could help us guide the next exploration stage.