Abstract:

After years of exploration,three oil fields,including Baiyang River oilfield,were discovered in the monocline zone in the northern part of the west Jiuquan basin.It is an urgent task for us to find out new oil fields.There-fore,we have,combining with geological studies and using trend surface anddiscriminant analyses,comprehensively studied the relations of known oil fields with geological variables,such as reservoir's structural residual value,thickness and its residual value,mean value of self-potential curve,frequen-cy of sand bed,ratio of thickness of less permeable intercalation to totalthickness of reservoir,and with the marginal slopes of these variables.It isdemonstrated quantitatively that the oil pool in the middle and upper parts of Huoshaogou Group(Eh₂₊₃) is mainly controlled by lithological and structural factors.The characteristics summarized here of the distribution of oil fieldsare as follows All known oil pools occupy the favorable structure positions in areas with positive residual values and with less permeable zones along updip formations.They may also be alined as strings of beads in a northwestern direction.Based on this,it was suggested that drilling should be carried out in eight promising blocks of four areas.Consequently,oil sand or commercial oil was found in blocks A,B and C by test-weels（Fig.8）,which shows that initial success has been achieved in the prediction.