CHARACTERISTICS AND DISTRIBUIVE REGULARITY OF THE OILS WITH LOW AND HIGH SOLIDIFICATION POINTS IN DAMINGDUN DEPRESSION

According to the characteristics of solidifreation point, wax content, etc., the crude oils in Damingdun Depression can be devided into high solidjfrcation point oil and low solidijication point oil, thinned oil and mixed oils, among which the high solidification point oil is dominant. It is rich in paraffin and ozokerite with wax content higher than 30% and high solidification point over 40℃, even up to 69℃. It differs from normal thickened oil (heavy oil) and can be attributed to low mature unoxidized primary oil. The low solidification point oil solidifies below 0℃, even down to -40℃. It has high specific gravity and viscosity, high contents of resin and asphaltene,high primary distillation point,and low soli-dification point, low wax content and light fractions. Therefore, it belongs to secondary biodegraded oil. The wax content of the thinned crude oil which belongs to waxy oil with low sulfur content is less than 15% while its hydrocarbon content can be 68.6%. The last type of the oils is the mixed oil of different ratios of thinned oil and high solidification point oil and the properties of the mixed oil are between these two oils. The source rocks of the high solidification point oil mainly are of Es⁴ dark claystones and the distribution of the oil is controlled by the source rock and faulting activities. The various types of crude oil layers in the depression are overlapped each others and according to the ordersfrom lower to upper oil layers, they respectively contain high solodification point oil, mixed oil, thinned and low solidification point oil. Howevev, the low solidification point oil is emplaced in shallow buried rocks of younger age while high solidification point oil is emplaced in relatively deep buried rocks of older age.