Abstract:

Dongying Depression is the typical continent rift basin, and many lithologic traps developed in the basin. Because the main controlling factors and mechanism of oil accumulation are not understood well, the next exploration disposition for lithologic reservoir is seriously controlled. On the basis of the data about 249 lithologic traps collected in the oil field, included good, middle, bad oil fullness and even no oil, the controlling factors of oil fullness were analyzed. The factor-analysis methods were used to find the main controlling factors. The research indicates that the plane and sectional distances between sand body and oil source center, petrophysical quality of sandstone body and the sandstone body size, for example thickness and area, are the main controlling factors of oil fullness for lithologic reservoirs. The relationship of oil fullness and distance is reverse ratio and there is no lithologic reservoir when the distance is longer than 24 km in Dongying Depression. The relationship of oil fullness and petrophysical quality is direct ratio and it goes against oil accumulation when the porosity is less than 10% and permeability is less than 1.3×10^-3 μm². With the sand body size bigger, the oil fullness is increased and then decreased, the corresponding inflexion is 2 m thickness and 0.3 km² area.

Key words: Dongying Depression, continental rift basin, lithologic reservoir, oil fullness, main controlling factor