A rare oil pool of Mesozoic lamprophyric intrusive body has been found on the Yihezhuang Uplift in the Chezhen Depression

North Shandong. This paper deals with the origin and distribution of porosity in the particular reser-voir rocks. The study made by means of maay petrological methods shows that: 1. The lamprophyric reservoir rocks are characterized by rich intracrystal porosity of augite and hornblende

clearly different from ordinary sedimentary reservoir rocks; 2. The porosity (5.2-25.2%) and the permeability (0.12-30 mD) are higher than that of the top and bottom sand stone reservoir rocks; 3. The secondary porosity was formed in the course of deep buried stage andthe acid organic solution came from adjacent organic rich source rocks of the Lower Tettiary (short distance migration); 4. The tectonic fractures have provided favourable passage for the migration of acid organic solution and oil; 5. The rapit evolution that started from the generation of organic solvent to hydrocarbon maturation associated with adequate fluid flux is another favour-able condition for the formation of secondary porosity. The periphery of the oil generation depression and the uplift within it are favourable targets for oil exploration when their basement faults are connected with the depression and various rocks there have fractures and easily disso-luting component.