Property distribution of carbonate rock reservoir is a complex thing due to the high level of heterogeneity, but it also becomes the cause that carbonate reservoir turn into a hydrocarbon reservoir with highly potential not only in Indonesia but also in the world. In Indonesia carbonate reservoir known to evolve at a very varied facies, starting from coral reefs, shoals up to bioclastic platform where each reservoir has its own history of diagenesis.
Diagenetic process that works on each reservoir affects the reservoir characteristics that are reflected in the genetic relationship with log characteristics that recorded on each reservoir. Diagenetic process that works generate secondary porosity as; vuggy porosity and intercrystalin dolomite porosity and also microporosity formed by diagenetic processes related to freshwater vadose and marine burial.
Diagenesis analysis conducted in the core data in the form of petrography thin section shows indication that each process of diagenesa that occurred in carbonate rocks if the result is being in comparative with log data it generates specific correlation and has a unique characteristic response to the log; GR, NPHI, RHOB and other conventional logs.
The unique phenomenon can be applied in other wells that have only log data and does not have the core data. By knowing the relationship between the log characteristics and diagenetic process that occurred in each carbonate reservoir, we can be determine where the good location for distribution of reservoir property that will eventually be useful for the development and the hydrocarbons depletion in carbonate reservoirs.
It is estimated that more than 60% of the world's oil and 40% of the world's gas reserves are held in carbonate reservoirs. The Middle East, for example, is dominated by carbonate fields, with around 70% of oil and 90% of gas reserves held within these reservoirs (Schlumberger).