Abstract
Owing to multiple tectonic events after the Late Triassic, the northern segment of the western Sichuan depression (NSWSCD) has a complex geological history of significant uplift and deeply buried. With abundant oil and gas play in the NSWSCD, the study of paleo-oil reservoir systems and early hydrocarbon accumulation in this area is of great significance for deep marine hydrocarbon distribution prediction in complex structural settings. Analysis on the northern section of the Mianyang-Changning Intracratonic Sag (MY-CN IS) and the Tianjingshan Paleouplift (TJS PU), the two Early Paleozoic tectonic units are laterally superimposed. Combined the reservoir bitumen of the Sinian Dengying Fm firstly, the biomarker (TT23/tT24, S21/S22, etc.) and Organic δ13C (lighter than 30‰) characteristics indicate that the Sinian-Jurassic paleo-oil system in the TJS PU area is the main source of Lower Cambrian organic-rich black shale. This is closely related to the superimposition and combination effects of the intracratonic sag and paleouplift. Therefore, this study establishes a geological-geochemical accumulation model through a combination of R o and fluid inclusion data. The No. 1 fault is an important zoning fault in the NSWSCD, which significantly controls the division of the oil-gas zone. The process of paleo-oil reservoir destroyed directly only exists in the frontal deformation zone. The deep marine strata of the eastern No. 1 fault demonstrate the four-center hydrocarbon accumulation processes, which include oil generation, gas generation, gas storage, and gas preservation. The superdeep Dengying Fm has long-term exploration potential in the NSWSCD.
Highlights
Typical dual thrust belt and foreland basin structures are well developed in the western Sichuan Basin [1]
The western Sichuan depression (WSCD) is a foreland depression that has been influenced by Indosinian, Yanshan, and Himalayan tectonic events
Since the Indosinian Orogeny, the typical multistage basin evolution and tectonic movement characteristics in the WSCD have been largely controlled by the formation and evolution of the Longmenshan Thrust Belt (LMS TB) on the western margin [2, 3]
Summary
Typical dual thrust belt and foreland basin structures are well developed in the western Sichuan Basin [1]. Since the Indosinian Orogeny, the typical multistage basin evolution and tectonic movement characteristics in the WSCD have been largely controlled by the formation and evolution of the Longmenshan Thrust Belt (LMS TB) on the western margin [2, 3]. Both of these are relatively consistent in the present tectonic pattern [4, 5]. Related studies on oil-source correlation, thermal burial history, and deep hydrocarbon accumulation processes were considered This allows for a better understanding of the extension-compression transition and the processes responsible for the formation of the paleo-oil reservoir system in the northwestern Sichuan Basin. The oil-gas migration model and implications for deeply buried hydrocarbon predictions were clarified
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