Study on Depositional Characteristic and Diagenetic Evolvement in Panyu Gas Field of Peal River Mouth Basin

Key words: 
• Peal River Mouth basin /
• Panyu gas field /
• diagenesis /
• Basin simulation /
• multiply

Abstract: The main gasbearing layers at Panyu gas field was belong to delta deposits of marine facies. The main bearing gas layer, SB13.8 layer was as main sediments of deltaic plain, but MFS18.5 layer was the depositing product of deltaic front. Based on the data of core, thin section; scan microscope, Xdiffraction, etc., the reservoir characteristics and diagenesis of Panyu gas field had been studied in detail. According to the latest classified criterion on diagenetic stage of clastic reservoirs, SB13.8 layer, one of the two main gas bearing layers, its stratum water circulating environment was an open type of alkalescence (pH>7.5), which was belong to stage B in early diagenesis with weak cementation and feeble diagenesis. MFS18.5 Layer, an other gas bearing layer, its stratum water circulating environment was an relative closed type of feeble acid(pH<6.5), which was belong to stage A in middle diagenesis. So, the augment of temperature had been catalyzed the dissolution course of organic acid water solution for silicate minerals, which had provided sufficient and indispensable conditions for the development of the secondary porous zones. Hereby, the diagenetic pattern of mavine quartzite sandstone reservoir has been established. As the view of reservoir characteristics, the texture and mineral component mature of MFS18.5 layer was higher than that of SB13.8 layer and it descended from lower to upper. Meanwhile, MFS18.5 layer had been reconstructed by waves and transported with long distance that was much more than those of SB13.8 layer. According to the results on cathode luminescence and scan microscope, the secondary enlargement of quartzs was to be the third degree and autogenetic kaolinite was well developed. This is the reason why the sandstone of MFS18.5 layer has the lower permeability and poor porosity contrasting with other reservoirs in Peal River Mouth basin. On the other hand, using specify basin simulating method of single well, the vertical change of porosity and permeability on the basis of burial history have been simulated, which can intuitively and more accurately analyze one another difference and characteristics of vertical multiply.