Carbonate Sedimentary Facies Characteristics and Model of the Lower Cretaceous Thamama Group in the United Arab Emirates

Abstract

Abstract The purpose this study is to use geophysical technology, analyze the characteristics of typical sedimentary facies in the study area, extract sensitive seismic attributes, compile sedimentary facies distributions, establish a sedimentary model, and improve the understanding of the distribution law of complex carbonate reservoir in oil and gas exploration and development. The Cretaceous Arabian Basin is a typical gentle slope carbonate basin with rich oil and gas resources. The main reservoirs in the study area have complex lithology, including bioclastic grainstone, bioclastic packstone and rudstone. However, the heterogeneity of carbonate rocks is strong and the sedimentary facies change rapidly, which increases the difficulty of understanding the distribution law of reservoirs. Based on core data, well logs, seismic data and well-to-seismic integration, the sedimetary facies study of the Cretaceous Thamama Group has been completed. Typical lithology and logging facies were identified. The logging facies were established, multi-well facies were carried out; and sedimentary characteristics were analyzed. Multi-attributes have been analyzed including amplitude, frequency, continuity and phase attributes to extract sedimentary facies maps by combining lithofacies and logging facies. Based on the above analysis results, a sedimentary model has been summarized. According to this study, the target strata are mainly carbonate deposits of gentle slope with shoal, inner shoal and grain flat facies deposits. Four typical logging facies were identified consisting of low energy shoal, margin shoal, grain shoal and grain flat microfacies. The favorable reservoirs are mainly bioclastic grainstone and packstone formed in a medium-strong hydrodynamic environment. The sedimentary model of the study area is established to analyze the distribution of target reservoirs and guide the analysis of favorable reservoirs in the area. The Thamama Formation has stable thickness in general, the depositional environments changed from subtidal to inner shoal of restricted platform, to grain shoal and grain flat. It is concluded that the Shuaiba Formation and the Kharaib Formation of the Lower Cretaceous Thamama Group in the middle of the study area are the most favorable reservoir development formations, and the central and northern areas are the most favorable oil and gas accumulation areas. Through this study, a more complete and instructive carbonate slope sedimentary model has been established. In addition, through the multi-attribute analysis technology and optimization method, we have completed and deepened the understanding of the distribution of the target layer sedimentary facies, and provided a new geophysical comprehensive research method. However, due to the complexity of carbonate rocks, further research is needed.