Quantitative evaluation method of OOIP and aquifer size for fractured-caved carbonate reservoirs with active aquifer support

Abstract

Fractured-caved carbonate reservoirs have the characteristic of strong heterogeneity, poor connectivity and complicated oil-water relationship, these reservoirs generally contain edge-bottom aquifer support and has non-uniform oil-water contact. Because of wrong estimation of the well original oil in place, well drilling success ratio is generally low and the development performance is also poor. How to quantitatively evaluate this kind of reservoirs’ reserves and aquifer size by dynamic methods, which can provide support to the following new well drilling and development strategy decision, is the key problem need to solve. Based on the Blasingame method and flowing material balance method, this paper derives the dynamic reserves evaluation theory for reservoirs with pseudo-steady state water-drive and proposes a process and method according to aquifer influx identification to quantitatively evaluate dynamic reserves and aquifer size. This method firstly uses aquifer influx dynamic identification method to divide well production history into three periods: no aquifer influx period, early aquifer influx period and middle-late aquifer influx period. Then the dynamic reserves can be evaluated according to matching well production data of no aquifer influx period, and then the aquifer size can be quantitatively evaluated by means of matching well production data of early aquifer influx period. What’s more, the established numerical simulation conceptual model with edge and bottom aquifer support verifies that the method is reliable. This method has been widely used in a fractured-caved carbonate oil field in China, the application is good.