塔里木盆地乌什凹陷石油地质特征

对乌什凹陷重磁非地震资料和新老地震剖面的地层及构造特征进行了解释,确定了乌什凹陷的盆地结构和断裂构造格架,分析了中生界的地层分布特征,对乌什凹陷的构造区带进行了重新划分。结果表明,乌什凹陷构造样式在东、西向有一定差异,可分西、中、东3个次级凹陷以及西、东2个低梁带,中生界主要分布在乌什凹陷东部。对乌参1井及邻区沉积储层研究表明,乌什凹陷白垩系扇三角洲相砂砾岩物源来自温宿凸起,与北部和东部沉积体系有较大差别。凹陷内白垩系砂岩储层发育,总厚度约为200～300m,纵向上储层非均质性较强。在阿瓦特河剖面的侏罗系恰克马克组新发现了一套更好的湖相灰黑色泥质泥晶云岩源岩。烃源岩评价结果表明,侏罗系恰克马克组母质类型好,成熟度适中,生油潜力巨大;西部石炭二叠系海相源岩的热演化程度高,有机质丰度低,综合评价其生油潜力相对较差。乌参1井油气源对比和成藏研究表明,其油气不同源,天然气来自侏罗系陆相腐殖型源岩;原油来自侏罗系恰克马克组湖相腐泥型母质。乌参1井为常温超高压层状富含油凝析气藏,其成藏机制为:异常压力封存箱内,侧向运移供气,沿断裂或不整合面充注,择优富集,晚期成藏。综合研究结果表明,乌什凹陷东部低梁及其南翼陡断阶带是最有利的油气运聚成藏区带,它们具有类似于却勒地区的有利成藏条件,是目前石油勘探的最现实领域。

Petroleum geologic characteristics of Wushi Sag in Tarim Basin

The integrated explanations of gravity-magnetic data and the characters of seismic sections of Wushi Sag were carried out. The basin filling sequence, structure framework and fault system were determined. The characters of Mesozoic stratigraphic distribution and structural play of Wushi Sag were analyzed. It shows that the structure pattern of Wushi Sag is different from west to east. Wushi Sag can be divided into western,central and eastern sub-sags as well as western and eastern low rise beam belts. The Mesozoic stratigraphy is chiefly distributed in the east Wushi Sag. The geology characters of Well Wucan-1 and adjacent sedimentary reservoir show that the provenance of Cretaceous fan-delta sandstones and conglomerates of Well Wucan-1 is Wen-Su Bulge. The depositional systems of Well Wucan-1 are very different from those of northern and eastern areas. The total thickness of the Cretaceous sandstone reservoir developed in Wushi Sag is approximately from 200 to 300 meters. The heterogeneity of reservoir in vertical sense is relatively strong. A new better source rock of gray dark politic micrite dolomite was found in the Jurassic Qiakemake Formation of Awate river profile. The source rock of the Jurassic Qiakemake Formation has good parent materials,moderate maturity and great oil-bearing potential. The western source rock of the Permo*$-Carboniferous marine facies has poor oil-bearing potential,because of their lower abundance of organic matters and higher degree of thermal evolution of Well Wucan-1.Gas was originated from the Jurassic humic type source rock of continental facies,and oil came from the Jurassic Qiakemake Formation sapropelic type source rock of lacustrine facies. Well Wucan-1 belongs to the rich condensate gas pool with normal temperature,super-pressure and bedded style. The pool-forming mechanism of Well Wucan-1 was characterized by abnormal pressure compartment,feed from lateral hydrocarbon kitchen,charged along fault or unconformity surface,accumulation in high-quality reservoir,pool-forming in late stage. The eastern low bulge belt and the southern belt of Wushi Sag are the most favorable areas for oil and gas accumulation. The pool-forming condition in these areas is similar to the Quele area of Kuqa Basin.