准噶尔盆地吉木萨尔凹陷中-上二叠统沉积相特征

准噶尔盆地东部吉木萨尔凹陷中-上二叠统由上芨芨槽子群、泉子街组、梧桐沟组组成．凹陷内中-上二叠统经历了低水位域→高水位域→低水位域的变化过程，其有利相带以扇三角洲和三角洲相为主，主要发育于东斜坡区的东北部及东南部以及凹陷南北两侧断裂下盘，在南北局部的乌拉泊组和梧桐沟组还发育浊积扇．油气显示集中于三角洲或扇三角洲相带内(芦草沟组、梧桐沟组)，凹陷腹部深湖-半深湖相内的扇三角洲和三角洲沉积区是凹陷内油气的最有利聚集区和保存区．     

吉木萨尔凹陷芦草沟组致密油储层沉积相分析

利用岩芯、薄片、录井和测井等资料,在识别各级次基面旋回界面类型及特征的基础上,将准噶尔盆地吉木萨尔凹陷芦草沟组划分为1个长期旋回,6个中期旋回,44个短期旋回,建立高分辨率层序地层对比格架。在总结地球化学、岩性、沉积构造、电性特征的基础上,综合分析古生物化石、测井等资料,以识别沉积相标志为主,进行单井、连井及平面沉积相分析。研究结果认为,吉木萨尔凹陷芦草沟组为咸化湖泊-三角洲沉积体系,岩性复杂多变,在机械、化学、生物等沉积作用共同影响下,形成由细粒碎屑岩、泥岩、碳酸盐岩构成的混积岩层。芦草沟组发育上、下两个致密油甜点体,上甜点体（SSC37-SSC42）为咸化湖相沉积,微相类型以滩坝为主;下甜点体（SSC6-SSC17）以三角洲前缘沉积为主,微相类型为席状砂、远砂坝等。利用开发试验区及水平井部署区的井多、井密的有利条件,对沉积相边界进行控制,从而实现平面微相的精细刻画,研究表明芦草沟组优质甜点以滩坝主体微相为主,主要集中发育在凹陷中心低隆起处。     

吉木萨尔凹陷芦草沟组致密油系统的成藏特殊性

通过烃源岩条件、储层特征与原油类型分布及其来源、源-储配置关系的系统分析,分析了准噶尔盆地吉木萨尔凹陷芦草沟组上、下段致密油系统的自生自储与层控成藏特征。结果表明,芦草沟组咸水湖相沉积中的不同岩性均有不同含量的原始有机质,其中的泥岩有机质丰度和生烃潜力最高,为主力烃源岩,母质类型具倾油特征,处于生油阶段。位于烃源岩层系内的砂岩类与碳酸盐岩类储集层主要为低孔低渗-致密背景,含油性与物性差异存在密切关系。源-储配置表现为互层和泥包砂特征,具有源、储邻近叠置分布的致密油聚集条件。芦草沟组上、下段的原油物性与地化特征存在明显差异,分别主要来自邻近层段烃源岩。综合研究认为吉木萨尔凹陷内芦草沟组具有就近运移、自生自储的层控致密油成藏模式。     

新疆吉木萨尔县水溪沟地区煤田矿坑涌水量预算与检验

对新疆吉木萨尔县西南水溪沟地区煤矿区按不同地质构造单元选取不同水文地质参数,采用＂大井法＂对煤矿床未来各开采中段进行矿坑涌水量预算。其中,用＂大井法＂预算的顺通煤矿现已开采矿井907 m中段的矿坑涌水量与该段实际矿坑涌水量基本一致。     

用树轮密度及宽度资料重建新疆吉木萨尔县的季节降水和最高温度

依据新疆吉木萨尔县天山云杉树木年轮宽度、最大密度和最小密度标准化年表,讨论了晚材宽度、最大密度和最小密度,与月平均最高温度和降水的响应函数基本特征,采用逐步回归方法,确定了利用晚材宽度指数、最大密度指数和最小密度指数重建该地６～９月份降水,以及利用最大密度指数和最小密度指数重建该地４～９月份平均最高温度。重建结果可靠且与实际情况较为一致。分析发现,该地区在过去１５０年中,月平均最高温度和降水有明显的阶段性变化。     

准噶尔盆地吉木萨尔凹陷芦草沟组湖相云质致密油储层特征与分布规律

准噶尔盆地东南缘吉木萨尔凹陷中二叠统芦草沟组新近发现了独特的湖相云质混积岩致密油储层,不同于传统的海/湖相硅质/灰质致密油储层,展示出重要的学科研究意义。本文报道了这类储层的基本特征与分布规律。结果表明,这类储层岩性主要由砂屑白云岩、粉砂质白云岩/白云质粉砂岩和微晶白云岩组成,见少量粉砂岩和凝灰岩;储集空间以次生粒间溶蚀孔隙和部分剩余粒间孔隙为主,微裂缝仅在少数样品中发育。储层含油性与物性呈正相关,据此将储层分为三类:一类储层孔隙度12%,渗透率0.1m D;二类储层孔隙度7%~12%,渗透率0.01m D;三类储层孔隙度以4%~7%,渗透率0.001m D。前两类是相对优质储层,分布特征表现为南厚北薄,物性南好北差。这种特点受控于沉积相及其物源,南部是主物源区。据此预测了有利储层分布区,其中芦草沟组上甜点段优质储层主要分布在吉32-吉171-吉31井区,下甜点段优质储层主要分布在吉174-吉251-吉36井区。这些认识还可供区域油气勘探参考。     

The impact of organic fluids on the carbon isotopic compositions of carbonate-rich reservoirs: Case study of the Lucaogou Formation in the Jimusaer Sag,Junggar Basin,NW China

The processes involved in the interaction between organic fluids and carbonates, and the resulting effect on reservoir quality during the evolution and maturation of organic matter remain unclear despite the fact that these processes influence the carbon and oxygen isotopic compositions of carbonates. Here, we provide new insights into these processes using data obtained from a detailed analysis of a mixed dolomitic–clastic and organic-rich sedimentary sequence within the middle Permian Lucaogou Formation in the Junggar Basin of NW China. The techniques used during this study include drillcore observations, thin section petrography, scanning electron microscopy (SEM) and electron probe microanalysis, and carbon and oxygen isotope analyses. Oil grades and total organic carbon (TOC) contents represent the amount of oil charging and the abundance of organic fluids within a reservoir, respectively, and both negatively correlate with the whole-rock δ¹³C and δ¹⁸O of the carbonates in the study area, indicating that organic fluids have affected the reservoir rocks. Secondary carbonates, including sparry calcite and dolomite overgrowths and cements, are common within the Lucaogou Formation. Well-developed sparry calcite is present within dark mudstone whereas the other two forms of secondary carbonates are present within the dolomite-rich reservoir rocks in this formation. Comparing thin section petrology with δ¹³C compositions suggests that the carbon isotopic composition of matrix carbonates varies little over small distances within a given horizon but varies significantly with stratigraphic height as a result of the development of secondary carbonates. The net change in whole-rock δ¹³C as a result of these secondary carbonates ranges from 1.8‰ to 4.6‰, with the secondary carbonates having calculated δ¹³C compositions from −18.6‰ to −8.5‰ that are indicative of an organic origin. The positive correlation between the concentration of Fe within matrix and secondary carbonates within one of the samples suggests that the diagenetic system within the Lucaogou Formation was relatively closed. The correlation between δ¹³C and δ¹⁸O in carbonates is commonly thought to be strengthened by the influence of meteoric water as well as organic fluids. However, good initial correlation between δ¹³C and δ¹⁸O of whole rock carbonates within the Lucaogou Formation (resulted from the evaporitic sedimentary environment) was reduced by organic fluids to some extent. Consequently, the δ¹³C–δ¹⁸O covariations within these sediments are not always reliable indicators of diagenetic alteration by organic fluids or meteoric water.The characteristics and δ¹³C compositions of the sparry calcite within the formation is indicative of a genetic relationship with organic acids as a result of the addition of organic CO₂ to the reservoir. Further analysis suggests that both carbonate and feldspar were dissolved by interaction with organic CO₂. However, dissolved carbonate reprecipitated as secondary carbonates, meaning that the interaction between organic fluids and dolomites did not directly improve reservoir quality, although this process did enhance the dissolution of feldspar and increase porosity. This indicates that the δ¹³C and δ¹⁸O of secondary carbonates and their influence on whole-rock carbonate isotopic values can be used to geochemically identify the effect of organic fluids on closed carbonate-rich reservoir systems.