Dolomitization Model of Pelletoid of Arab C Formation in Southern Arabian Gulf

Dolomitization is the main geological process that turn pelletoid into dolomites. How does dolomitization convert pelletoid into dolomites? Why do dolomites have different structures and crystals? This paper mainly answers these two questions. Based on core, cast thin sections, physical property and mercury intrusion, the Pelletoid types are first determined. Secondly, the diagenesis of the Pelletoid is comprehensively recognized, including the diagenetic types, diagenetic environment and diagenetic product. Finally, the dolomitization model of Pelletoid is established.

There are four types dolomite in Arab C formation in BH oilfield. The Arab C Formation was in a tidal flat environment, in which facies include supratidal, intertidal and subtidal. Different facies have different water energy, lithology, exposure probability and time, as a result, the diagenesis such as gypsification, dolomitization, dissolution and cementation in different area vary greatly. That’s why there are four type of dolomite even the primitive particles are the same pelletoids. The pelletoids were mainly in the intertidal facies, subtidal facies with relatively high energy could also developed. Intertidal facies was easy to exposure, and gypsification and dolomitization was intense in penecontemporaneous stage. Due to the environment difference, response to sea level fluctuation and exposure time, the diagenesis, especially the extent of dolomitazition is different. As a result, the dolomite has different character in structure and crystal.