Controlling factors of reservoir quality and favorable reservoir predictions of the Liushagang Formation in Fushan Sag

Key words: 
• Key words: Liushagang formation /
• sedimentary microfacies /
• diagenetic facies /
• fracture facies /
• controlling factors /
• high-quality reservoir prediction

Abstract: Abstract: The Liushagang formation is one of the petroliferous reservoirs in the Fushan Sag, Beibuwan Basin. However, the controlling factors of reservoir quality are unclear and there are no matched prediction technology for reservoir quality, which restrict the process of oil and gas exploration and development. In our study, the controlling factors of reservoir quality are unraveled from the perspective of “three-element controlling reservoir” including sedimentary microfacies, diagenetic facies and fracture facies. In addition, the methods of logging characterization and identification standards are established. The results show that the sedimentary microfacies, diagenetic facies and fractures play important role in controlling reservoir quality in the Liushagang formation. By analyzing the relationships between different types of sedimentary microfacies, diagenetic facies, and fracture facies and parameters of reservoir quality, it can be concluded that the high reservoir quality reservoirs are formed in the dissolution facies in the underwater distributary channel and mouth bad microfacies under high-energy depositional environment. Additionally, the development of fractures has a significant improvement on reservoir quality. By integrating the three controlling factors (sedimentary microfacies + diagenetic facies + fracture facies) and combined with four important reservoir characteristic parameters, four types of reservoirs are classified. The conclusion of oil and gas interpretation and oil test data prove that the proposed method can effectively evaluate and predict the favorable reservoir layers. This research can provide theoretical guidance for the increase of reservoirs and production in the Liushagang formation in Fushan Sag, and provide insights into the fine characterization of reservoirs and the prediction and evaluation of high-quality reservoirs.