Sequence Stratigraphic Study, Prediction and Quality Evaluation of Reservoir for the Ordovician Yijianfang Formation of the Southern Part of the Tahe Oilfield

Key words: 
• Tahe oilfield /
• Yijianfang Formation /
• beach facies /
• thirdorder sequence /
• high frequency sequence /
• reservoir prediction and evaluation of reservoir quality

Abstract: According to sequence stratigraphy, on the basis of integrated study on outcrop, well drilling, well logging and seismic data, one thirdorder sequence has been recognized in the Yijianfang Formation. In the upper of the high system tract, at least 5 high frequency sequences have been recognized. And beach facies distribution is depicted both in thirdorder sequence and in high frequency sequence. Then based on the foregoing research, the reservoir in this area has been predicted and conclusions have been made as follows: Vertically, the development of reservoir is controlled by sequence and highfrequency. Flatly, the reservoir develops on the center of the beach which lies in the north of break of slope in the platform. Then by researching the relationship between reservoir qualities and controlling factor, controlling mode of reservoir quality has been set up. At last, by researching the relations between reservoir quality and highfrequency, beach position and tectonic, it can be seen that the fifth highfrequency's reservoir quality is superior to the third, beach center quality is superior to the edge, southwest and south of Tahe oilfield's quality is superior to the east.