Abstract:

Taking for example the main oil and gas production formations of carbonate in Callovian-Oxfordian of Samandepe gas field, Amu Darya basin, Turkmenistan, and settings about the sedimentary facies, diagenesis means, diagenetic evolution sequence and corresponding products of geologic process, the authors make a comprehensive research on diagenetic environment and diagenetic fluid property reflected by the geochemical behavior, such as trace element, Fe, Mn, Sr, stable isotope, C, O, Sr, fluid inclusion, and cathode luminescence. According to the “hydrologic system”, CallovianOxfordian are divided into three diagenetic system, seawater-freshwater,compaction brine and deep cycle temperature and pressure water in different diagenetic stage. The deposition and diagenetic system have a good coupling relationship with reservoir in the space and time, which can be classified as: ①Platform edge reef and shallow facies control the regional distribution of reservoir. ②The early-denudation of fresh water system, and the shallow burial dolomitization of compaction brine diagenetic system in early-diagenetic stage are the key to forming reservoir. ③Buried denudation of the diagenetic system of temperature and pressure water, middle-deep buried dolomitization and tectonic disruption action in mid-diagenetic stage enlarge the reservoir scale, promote the reservoir quality, and contribute greatly to the development of high-grade reservoir.

Key words: sedimentary facies, carbonatites, reservoirs, depositional and diagenetic system, Callovian-Oxfordian, Samandepe gas field, Turkmenistan