Abstract:

Marine carbonate has been an important hydrocarbon prospecting domain of our country, in which the secondary space, such as karst cavity, is an important reservoir. However, the unpredictable of the buried karst reservoir is a challenge for carbonate hydrocarbon prospecting. Dissolutiondeposition equilibrium theory used in carbonate indicates that there was little fluid inclusion in dissolution zone or dissolutiondeposition equilibrium zone and many fluid inclusions were generated in deposition zone accompanying new mineral generation. The developmental phases of fluid inclusions suggested the fluid active phases during the geological history. Based on this, the following idea was deduced: the packing action is more obvious where there are more developmental phases of fluid inclusion, and thus the reservoir is relatively worse, and vice versa. In this paper, based on dissolutiondeposition equilibrium theory, using fluid inclusion data of Ordovician holes filling in Tarim Basin, combined with geology of buried history, the buried karst reservoirs packing timespace history of the research area was restored, and the karst reservoir zones of varying degrees of packing were fixed, and the beneficial reservoir area can be located under reverse thinking. The application of this method to the Ordovician carbonate formation of Tarim Basin area proved its feasibility; the result shows that the prediction of the fluid inclusion method is almost identical with the core observation and drilling or logging results. By this approach, we can predict the better reservoir correctly. On the whole, the fluid inclusion approach provides a feasible method in evaluating holes filling strength in strata environment. This is significant in theory and practice for the buried karst reservoir evaluation.

Key words: fluid inclusion, carbonate, buried karst reservoir, holes filling strength, Ordovician, Tarim Basin