Reserves Estimation for Ultra-Deep Fault-Controlled Fractured Cavity Carbonate Reservoirs

The carbonate reservoir of the Yijianfang Formation - the 2nd Member of the Yingshan Formation in the Ordovician System of the Fuman Oilfield is a typical fault-controlled fractured-vuggy carbonate reservoir. For reservoir engineers, evaluating the dynamic reserves of single wells or connected units in this reservoir is a challenging task; improper evaluation will lead to large errors and even result in mistakes in development decisions. Based on the reservoir characteristics and flow characteristics of the Fuman Oilfield, this study established two well test analysis methods, namely the wellbore storage coefficient analysis method and the pressure drawdown well test analysis method. The basic principles and application conditions of each calculation method were elaborated respectively, and verification was conducted using field data. The calculation results show that the dynamic reserve calculation results obtained by the well test methods are consistent with those of the RTA (Rate Transient Analysis) method, which provides a reliable basis for formulating development technical policies of this type of reservoir and implementing enhanced oil recovery measures in the middle and later stages of reservoir development.