Depositional Characteristics of Gravity Flow and Its Geologic Significance of the Continental Fault Basins: A Case at the Third Member of Shahejie Formation in Maozhou Area of Baxian Depression, China

Abstract

Abstract

In recent years, deep-water reservoir gravity flow, especially those that were developed in the deep lake areas, have elicited considerable attentions from petroleum geologists in China. Therefore, detailed study of depositional characteristics is a key area to deep-water sandstone reservoir prediction.

The study area, Maozhou, is located in south-central Baxian depression, and bounded in its northwest by Niudong fault and southeast by Maxi fault. It is a transfer zone that covers 300 km².

During the depositional period of the third member of Shahejie formation (Es₃), intense tectonic movements have resulted in relatively large accommodation, which provided circumstances for deep-water gravity flow deposits. Furthermore, comparatively thick salt successions have developed and are interbedded with the gravity flow deposits.

Using high-resolution 3D seismic data, borehole data, cores and experimental data, this paper studied the sedimentary characteristics and facies model of gravity flow deposits during the depositional period of Es₃ in Maozhou area, and provides reference for the study of gravity flow systems in continental fault basins.

This research has presented the following conclusions. 1) The study area of gravity flow are of three main types: sandy debris flows, muddy debris flows and turbidity deposit. 2) The sublacustrine fan gravity flow system is located mainly in the south of basin center, which extends 10 km to the axial direction and 6 km to the axis-vertical direction. Affluent deformation structures occur on the core sequence. The slump gravity flow system is located mostly in the west and southeast part of the study area and it has formed a massive delta, especially at the delta front. 3) Channel show typical scour-fill reflection characteristics on the seismic sections, such as “lenticular”, “fusiform”, and “wormlike” reflection characteristics. Sublacustrine fan show typical wedge-shaped or heterotropic reflection characteristics. 4) The research team has established a model of gravity flow deposit in Es₃. Fault activities affects the location of gravity flow deposits and the sedimentary body shape. Sandy debris flow can deposit both on the slope and in deep lake plain.

Findings from this study not only contributes to the geological theory of depositional characteristics of gravity flow, but also provides some insights for oil and gas exploration in the future.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016