Hierarchical Architectural Element Analysis for Sandy Conglomerate Deposits of Baikouquan Formation, Mahu Sag

摘要/Abstract

摘要： Enormous petroleum resources have been discovered in the Lower Triassic Baikouquan formation of Mahu sag, Jungar basin since the year of 2010, but reservoir evaluation and efficient development are difficult due to the complicated internal structure and serious reservoir heterogeneity of the sandy conglomerate in Baikouquan formation, so profound analyses on sedimentary genesis and architectural structure of the sandy conglomerate are needed. The paper utilizes hierarchical architectural element analysis method to delineate the architectural structure of the sandy conglomerate in Baikouquan formation of Mahu sag. Based on the detailed description of cores of 1,922 m long obtained from 82 wells, the paper presents a multi-attribute lithofacies denomination program which is dominated by 4 attributes i.e., rock grain size, sedimentary structure, color and grain support mode and 227 lithofacies are identified in the sandy conglomerate of Baikouquan formation. According to core, logging and seismic data, depositional interfaces of 11 orders are classified in the studied interval and architectural elements of 11 orders are identified correspondingly, and the corresponding architectural elements to lithofacies and sedimentary microfacies are analyzed. Taking the 9th order architectural element as a basic unit, the evolution processes of the sedimentary systems in Huangyangquan fan and Xiazijie fan are characterized through well-tie correlation constrained by seismic data. It is considered that the Baikouquan formation in both Huangyangquan fan and Xiazijie fan belongs to coarse-grain sandy conglomerate deposits and takes river as the main transportation force. The depositional system of Huangyangquan fan is of relatively small scale and has more characteristics of alluvial fans and fluvial fans; the depositional system of Xiazijie fan is of large scale and has more characteristics of river fans. From the first member to the third member of Baikouquan formation, the depositional system gradually changed from alluvial and fluvial fans to fan delta with the rise of water level of lake. Medium-fine conglomerate with low content of matrix is good lithofacies, seasonal channel deposits and underwater distributary channel deposits are favorable sedimentary microfacies, the second member of Baikouquan formation is the most favorable interval for oil accumulation.

关键词: Junggar basin, Mahu sag, Baikouquan formation, conglomerate deposit, analytic hierarchy process, architectural element analysis

Abstract: Enormous petroleum resources have been discovered in the Lower Triassic Baikouquan formation of Mahu sag, Jungar basin since the year of 2010, but reservoir evaluation and efficient development are difficult due to the complicated internal structure and serious reservoir heterogeneity of the sandy conglomerate in Baikouquan formation, so profound analyses on sedimentary genesis and architectural structure of the sandy conglomerate are needed. The paper utilizes hierarchical architectural element analysis method to delineate the architectural structure of the sandy conglomerate in Baikouquan formation of Mahu sag. Based on the detailed description of cores of 1,922 m long obtained from 82 wells, the paper presents a multi-attribute lithofacies denomination program which is dominated by 4 attributes i.e., rock grain size, sedimentary structure, color and grain support mode and 227 lithofacies are identified in the sandy conglomerate of Baikouquan formation. According to core, logging and seismic data, depositional interfaces of 11 orders are classified in the studied interval and architectural elements of 11 orders are identified correspondingly, and the corresponding architectural elements to lithofacies and sedimentary microfacies are analyzed. Taking the 9th order architectural element as a basic unit, the evolution processes of the sedimentary systems in Huangyangquan fan and Xiazijie fan are characterized through well-tie correlation constrained by seismic data. It is considered that the Baikouquan formation in both Huangyangquan fan and Xiazijie fan belongs to coarse-grain sandy conglomerate deposits and takes river as the main transportation force. The depositional system of Huangyangquan fan is of relatively small scale and has more characteristics of alluvial fans and fluvial fans; the depositional system of Xiazijie fan is of large scale and has more characteristics of river fans. From the first member to the third member of Baikouquan formation, the depositional system gradually changed from alluvial and fluvial fans to fan delta with the rise of water level of lake. Medium-fine conglomerate with low content of matrix is good lithofacies, seasonal channel deposits and underwater distributary channel deposits are favorable sedimentary microfacies, the second member of Baikouquan formation is the most favorable interval for oil accumulation.

Key words: Junggar basin, Mahu sag, Baikouquan formation, conglomerate deposit, analytic hierarchy process, architectural element analysis

ZHANG Changmin, LIU Jiangyan, PAN Jin, ZHU Rui. Hierarchical Architectural Element Analysis for Sandy Conglomerate Deposits of Baikouquan Formation, Mahu Sag[J]. 新疆石油地质, 2018, 39(zk(English) ): 9-20.

ZHANG Changmin, LIU Jiangyan, PAN Jin, ZHU Rui. Hierarchical Architectural Element Analysis for Sandy Conglomerate Deposits of Baikouquan Formation, Mahu Sag[J]. Xinjiang Petroleum Geology, 2018, 39(zk(English) ): 9-20.

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