Genetic Types and Superimposition Patterns of Subaqueous Distributary Channel Thin Sandbodies in Delta Front: A case study from the Ⅳ-Ⅵ reservoir groups of H3 in Biqian 10 area of Gucheng oilfield

Key words: 
• Biqian 10 area /
• single sandbody /
• short-term base-level cycle /
• subaqueous distributary channel /
• delta-front

Abstract: Thin sandbodies of subaqueous distributary channels of delta-front are widely developed in Biqian 10 area, Gucheng oil field, Biyang sag. Depending on fine study of reservoir sedimentary microfacies with integrating various data including cores and small well spacing logging data, we characterized the single sand body identification in compound subaqueous distributary channels and established a quantitative prediction model for single sand body scale, then we classified the subaqueous distributary channels into 3 types according to channel scale. Based on the short-term base-level cycle theory of high resolution sequence stratigraphy, the paper analyzes the genesis of subaqueous distributary channel sandstones in the study area. The result shows that in the course of base-level rising, A/S<<1, sandstone genetic type is mainly truncated distributary channel sandstone body, A/S<1(close to 1), sandstone genetic type is mainly integrated distributary channel sandstone body. We identified that there are five main vertical superimposition patterns of single sandbodies, including vertical superposition, lateral superposition, vertical tangency, lateral tangency and vertical separated, and three lateral contact patterns, including interdistributary contact, horizontal overlap contact and lateral superimposition-tangency contact, moreover, each type of logging-facies marks is summarized.