Main controlling factors of tight oil enrichment and high yield in a certain area of TH depression in Ordos Basin

A certain area of TH depression in Ordos Basin has tight reservoir and good oil-gas exploration potential, but the main controlling factors of tight oil enrichment and high yield are not clear, which seriously restricts the efficient exploration and development of this area. The geological characteristics of the reservoir in the study area were studied on the basis of seismic, drilling, geochemistry and dynamic production data. The tight oil accumulation conditions in member 8 of Yanchang Formation (Chang 8 member) were sorted out, and the main accumulation models were established to identify the main controlling factors of tight oil enrichment and high yield. The results are as follows.① The high quality source rock and upper mudstone cover of member 7 of Yanchang Formation (Chang 7 member) are widely distributed, and the underwater distributary channel of Chang 8 member is favorable for reservoir development. The oil-gas is injected downward from source rocks of Chang 7 member to the sand body of Chang 8 member. And the cycle source matching and preservation conditions are favorable, resulting in the formation of a tight sandstone reservoir. ② The size and physical properties of the reservoir sand body control the oil reserves and hydrocarbon abundance. The physical properties of tight sandstone are improved by the fractures formed by Yanshanian tectonics, and the corresponding fracture development area is the main area with oil production greater than 1t per day. ③ The upwelling of normal faults with smaller drilling intervals in the horizontal segment has a good development effect, while the downwelling of normal faults with larger drilling intervals in the horizontal segment has a poor development effect. Favorable reservoir facies belt, effective fracture reconstruction and well location configuration are the main factors controlling tight oil enrichment and high production. The research achievements have guiding significance for the subsequent well location deployment and reservoir development in the study area.