柴达木盆地三湖地区第四系七个泉组物源研究^*

Provenance features of the Quaternary Qigequan Formation in Sanhu area, Qaidam Basin

摘要

为了深入评价柴达木盆地东部三湖地区第四系七个泉组天然气勘探潜力以及预测有利岩性气藏勘探区带和目标,文中通过重矿物组合、ZTR指数、重矿物稳定系数以及砂岩碎屑组分等参数,系统分析了该地区七个泉组的物源组成,确定物源方向并恢复母岩类型。研究表明: (1)七个泉组沉积时期,三湖地区重矿物稳定系数和ZTR指数均由柴达木盆地边缘向盆地中央方向增大,大致呈环带状展布,不同物源区主要重矿物组合差异显著,不稳定重矿物含量变化明显。(2)格尔木物源主要流动方向为北偏西方向,向北影响涩北地区的南部; 乌图美仁物源规模小于格尔木物源,主要流动方向为北东方向,向北东影响台南地区的西南部和涩南3井区。(3)锡铁山—埃姆尼克山物源和绿梁山物源规模均较小,其中前者影响范围向南达察尔汗地区,而后者向南影响伊克雅乌汝北部和驼峰山地区。(4)台南—涩北地区主要为乌图美仁物源和格尔木物源的共同影响区。该研究首次明确了柴达木盆地三湖地区物源由乌图美仁物源和格尔木物源组成的昆仑山缓坡物源体系、由锡铁山—埃姆尼克山物源和绿梁山物源组成的祁连山陡坡物源体系以及盆地内部台南—涩北地区混合物源体系组成,可为该地区天然气勘探开发提供指导作用。

Abstract

To assess the potential for natural gas exploration in the Quaternary Qigequan Formation in the Sanhu area of the eastern Qaidam Basin and identify favorable lithologic gas reservoir exploration zones and targets,this paper systematically analyzes the provenance composition of the Qigequan Formation in the area. By examining parameters such as heavy mineral assemblage,ZTR index,stability coefficient of heavy mineral sand sandstone clastic composition,the study determines the provenance direction and reconstructs the parent rock type. The findings reveal that the stability coefficient and ZTR index of heavy minerals in the Sanhu area increased from the margin to the center of the Qaidam Basin during the sedimentary period of the Qigequan Formation,which was roughly distributed in a ring belt. The study identifies different main heavy mineral assemblages in various source areas and significant variations in the content of unstable heavy minerals. The study indicates that the Golmud provenance flows in a north-west direction,influencing the southern part of the Sebei area,while the Wutumeiren provenance has a smaller scale and flows northeast,impacting the southwestern part of the Tainan area and the Senan 3 well area. Additionally,the study shows that the provenance scale of Mt. Xitieshan-Emnik and Mt. Lvliang is limited,with distinct effects on surrounding regions. The Tainan-Sebei area is primarily influenced by the Wutumeiren provenance and Golmud provenance. This study establishes that the Sanhu area in the Qaidam Basin is characterized by the Wutumeiren provenance and Golmud provenances. The Kunlun Mountain gentle slope provenance system,the Qilian Mountain steep slope provenance system made up of the Xitieshan-Emnike Mountain source and the Lvliang Mountain source,and the blended source system in the Tainan-Sebei area within the basin can offer direction for natural gas exploration and development in this region.

关键词

重矿物 / 物源方向 / 七个泉组 / 第四系 / 三湖地区 / 柴达木盆地

Key words

heavy minerals / provenance direction / Qigequan Formation / Quaternary / Sanhu area / Qaidam Basin

基金资助

*中国石油重大科技项目(编号: 2021DJ08,2021DJ1705,2016E-01),国家重大科技专项(编号: 2016ZX05003-006)联合资助