Lithofacies, Succession, and Their Genetic Interpretation of Lacustrine Gravel Beach-Bars

Biao Peng,Yulu Wei,Huanyuan Wang,Siqi Liu,Jianfeng Li,Shenglan Ye,Lulu Zhang,Zhongwei Wu

doi:10.2113/2021/4719519

Abstract

Abstract Based on the elaborate dissection of profile sections parallel and vertical with the shoreline and the forming beach-bars, the unique sedimentary succession of gravel beach-bars, “ABC” sequence, has been found, and their lithofacies and origin have been explained. The A interval is composed of poorly sorted sand and gravel, formed in the wave asymmetric zone. The B interval is composed of well-sorted gravel, formed in the breaker zone. The C interval is composed of normally graded sand, formed in the surfing zone. In the actual gravel beach-bars, three intervals are often presented in a variety of combinations, such as “ABCABC,” “BCBCBC,” “ABABAB,” and others. These findings provide an important basis for the identification and distribution prediction of beach-bar reservoirs in the ancient continental lake basins.

Highlights

Lacustrine beach-bar deposits are characterized by well physical property, and it is easy to form large-scale oil and gas fields that is one of the important reservoirs in petroliferous basins in China [1,2,3,4,5,6]
The A interval is dominated by gravels and sands, which are subround and poorly sorted and have massive bedding, with gravels oriented floating in the coarse sands
Through a detailed study of the profile vertical and parallel with the shoreline, it is found that gravel beach-bars have a fixed sedimentary succession, named “ABC” sequence (Figure 7): (1) The A interval, the bottom of the sedimentary succession, is dominated by coarse sands and gravels, which are subround and poorly sorted and have massive bedding, with gravels oriented floating in the coarse sands

Summary

Introduction

Lacustrine beach-bar deposits are characterized by well physical property, and it is easy to form large-scale oil and gas fields that is one of the important reservoirs in petroliferous basins in China [1,2,3,4,5,6]. Most of researches pay close attention to sandy beach-bars and lose sight of gravel beach-bars, such as Aagaard (1990), Zhu Xiaomin (1994), Soreghan and Cohen (1996), Deng Hongwen (2011), Schwartz (2012), and Jiang Zaixing (2012) [6, 13,14,15,16,17]. They have made a comprehensive study on the sedimentary characteristics, geophysical characteristics, distributional pattern, and reservoir characteristics of the sandy beach-bars.

Methods

Discussion

Conclusion