GEOLOGIC-SEISMIC MODELS AND PREDICTION OF SANDS BASED ON HIGH-FREQUENCY SEQUENCE STRATIGRAPHY AS APPLIED TO THE LATE MIOCENE, BLOCK BZ34, HUANGHEKOU SAG, BOHAI BAY BASIN, CHINA

The Huanghekou Sag is located in the southeast part of the Bohai Bay Basin, China. A sedimentary system of a large-scale shallow lake delta developed in the Neogene, which provided suitable geological conditions for the formation of a subtle oil-gas reservoirs in this area. To accurately depict reservoir sandbodies is one of the key points in analyzing geological conditions for forming a subtle oil-gas reservoir. The core issue for analyzing sandstone reservoir or sedimentary facies is by using seismic attributes (amplitude) to establish the relationship between lithology combination and seismic attributes (e.g., seismic amplitude). In this paper, a detailed study closely related with establishing this type of relationship was conducted through the following steps: 1) conducting high-frequency sequence research in a 3rd sequence framework, with the sequences being classified into parasequence sets (fourth-order); 2) carrying out detailed statistics and analyses of lithology types and their combination features within this high-frequency sequence framework; 3) conducting attribute extraction, comparison, and optimization within this high-frequency sequence framework; 4) choosing a three-dimensional (3-D) area with relatively dense wells and analyzing the relationship between seismic attributes and lithology combination at well locations using statistical methods; 5) establishing the forward synthetic seismic models regarding the development features of one-dimensional (1-D) sandbodies and selectively analyzing the relationship between the vertical combination of sandstone and mudstone and the sedimentary micro-facies they represent as well as the synthetic seismic amplitude; 6) establishing two-dimensional (2-D) vertical-lateral development models of genetic sandbodies and their two-dimensional (2-D) forward seismic records, and comparing the synthetic seismic records with actual seismic profiles to prove the reliability of the geological model of the spatial development of sandbodies.Different sand-mudstone combinations genetically reflect a certain type of sedimentary micro-facies (or a combination of multiple micro-facies), therefore, predicting sandbodies based on the amplitude features can also reflect sedimentary facies characteristics.