Flattening diagenesis of clastic rocks and quantitative characterization of sedimentary control on reservoir properties: a case study of Baiyun sag in Pearl River Mouth Basin

Sedimentation and diagenesis are the two main factors controlling clastic reservoir properties. The sediment size, structure, sedimentary facies and the flow regime of transport medium restrict the development of reservoir primary pores and affect the path of subsequent diagenesis. However, due to the long-term diagenesis after sedimentation, it is difficult to quantitatively characterize the reservoir physical property controlled by sedimentation. Therefore, it is proposed to adjust the physical property to correspond with the same level of diagenesis, i.e., flattening diagenesis process. Through studying the analysis and test data of 32 drilling wells in the Baiyun sag, Pearl River Mouth Basin, the abnormal thermal evolution, shallow calcareous cementation, deep secondary corrosion and other local abnormal diagenesis were identified by the porosity-permeability cross plot and the law of variation with buried depth, thus eliminating the affected sample data. According to the correlation between the fitted ground temperature, buried depth and physical properties, the effects of regional differences in diagenesis were corrected, and an analysis was carried out on the control of reservoir physical properties by sedimentation. The analysis results show that the reservoir physical properties are positively correlated with sediment particle size and sorting, unrelated to the maturity of components. The most favorable reservoir sedimentary microfacies are the delta front subaqueous distributary channel and the deep water fan gravity channel. The complete process of quantitative analysis on the reservoir physical properties controlled by sedimentation is useful for similar studies in other regions. © 2019, Editorial Office of ACTA PETROLEI SINICA. All right reserved.