Dynamic-Static Integrated Classification Evaluation and Distribution Based on Genetic Control of Bioclastic Limestone Reservoir

Abstract

AbstractImpacted by complex sedimentary and diagenetic characteristics, bioclastic limestone reservoirs develop pore with diverse types, and pore-throat with complex structures, which put difficulty in classification evaluation, and further restrict the efficient development of the reservoirs. Comprehensively utilizing the data of core, well-logging, seismic, cast thin section, high pressure mercury injection and production performance, taking the lower member of Mishrif Formation in the Middle East H oilfield as an example, the differential diagenesis characteristics of bioclastic limestone reservoirs are clarified, and reservoir genetic classification evaluation system with sedimentary diagenesis control and production dynamic is established, the characteristics of reservoir distribution are then revealed based on the associative analysis of well-logging and seismic. The results show that the sedimentary microfacies determine the original fabric structures and bioclastic types of Mishrif Formation, and thus further control the diagenesis sequence and intensity. There are four types of differential diagenesis characteristics: high energy microfacies developed with non-selective dissolution, medium energy microfacies superimposed with selective dissolution, medium-low energy microfacies developed with moderate cementation and moderate -weak dolomitization, low energy microfacies superimposed strong cementation and moderate dolomitization, each type of reservoir develops pore with similar combinations and pore-throat with similar structures. Based on the impact of sedimentary diagenesis, reservoir physical properties and their control on productivity, the bioclastic limestone reservoirs in the studied area are divided into six categories, and the density and deep resistivity identification crossplot is also constructed. Under the constraints of sedimentary microfacies, combined with seismic cloud-transformation physical property inversion method, the distribution characteristics of various types of reservoirs are described. Type I and II reservoirs with medium-high porosity, high permeability and high productivity are mainly developed in the rudist shoal and bioclastic-arene shoal on the platform edge in MB2-1, MB2-2 and MC1-2 layers. The bioclastic limestone of Mishrif Formation is the main production layer in the Middle East, and the research above is of guiding significance for the development of similar reservoirs.KeywordsBioclastic limestoneSedimentary microfaciesDifferential diagenesisGenetic classificationDistribution characteristics