Control function of Sedimentary Facies on Tight Oil Distribution—Taking Gaotaizi Oil Layer in Qijia Area as An Example

Abstract

In order to find out the controlling factors of tight oil distribution in Gaotaizi oil layer, Qijia area, the authors consider that the sediment facies is shallow delta in G3-G4 oil layer through the fine study of sedimentary characteristics, and develops delta plain, delta front and prodelta subfacies from north to south. Multiple and small scale transgressions during with the base level falling cause the multistage superposition between delta outer front with prodelta mud, and the terminal of delta inner front with the mud of delta outer front, which provide the premise of source and storage match for inner source tight oil. Then, the authors analyze the control action of sediment facies on tight reservoir, high quality oil layers and the matching relationship between them, and point that there exist two kinds of tight oil reservoir in Qijia area, tight reservoir of distal bar in the rear of delta inner front, tight reservoir of sheet sand in delta outer front. By comparing the superiority of the three conditions, the former is better in reservoir condition, hydrocarbon source rock condition and source storage matching, which is the most important tight oil reservoir type. Finally, it is pointed out the tight reservoir of distal bar in rear of delta outer front is the most favorable microfacies in the next tight oil exploration in southern Qijia area.