须家河组沉积模拟实验及大面积砂岩成因机理分析

四川前陆盆地上三叠统须家河组砂岩大面积分布,是整个盆地现今天然气勘探的重点层系之一,随着气田的勘探和开发,亟需弄清形成大片砂岩的主控因素来指导勘探和生产。为研究其成因机理,在对须家河组区域构造演化、古地貌、沉积体系等地质条件调查研究的基础上,运用沉积物理模拟的方法,将原型地质条件转化为物理模型,并设计模拟实验参数,通过水槽模拟实验技术进行研究。实验主要设计三个物源,通过控制流量、加沙量、地形坡降、活动底板沉降量及湖水位等参数,在水槽装置再现形成大面积砂岩的演变过程,系统研究大面积砂岩形成的主控因素。模拟结果表明,地形坡降小、不同来水特征组合、湖水频繁进退、各沉积体系间交汇及盆地沉降与沉积速率的匹配等,影响着大面积砂岩的形成。实验发现多期河道不断分汊改道,在侧向上不断迁移,纵向上受湖水位的变化表现为前积和退积,致使砂体在横向和纵向上相互拼接,导致砂岩大面积分布。     

Detrital K‐feldspar 40Ar/39Ar Ages: Source Constraints of the Lower Miocene Sandstones in the Pearl River Mouth Basin,South China Sea

The South China Sea began to outspread in the Oligocene. A great quantity of terraneous detritus was deposited in the northern continental shelf of the sea, mostly in Pearl River Mouth Basin, which constituted the main paleo-Pearl River Delta. The delta developed for a long geological time and formed a superimposed area. Almost all the oil and gas fields of detrital rock reservoir distribute in this delta. Thirty-three oil sandstone core samples in the Zhujiang Formation, lower Miocene (23–16 Ma), were collected from nine wells. The illite samples with detrital K feldspar (Kfs) separated from these sandstone cores in four sub-structural belts were analysed by the high-precision 40Ar/39Ar laser stepwise heating technique. All 33 illite 40Ar/39Ar data consistently yielded gradually rising age spectra at the low-temperature steps until reaching age plateaus at mid-high temperature steps. The youngest ages corresponding to the beginning steps were interpreted as the hydrocarbon accumulation ages and the plateau ages in mid-high temperature steps as the contributions of the detrital feldspar representing the ages of the granitic parent rocks in the provenances. The ages of the detrital feldspar from the Zhujiang Formation in the four sub-structural belts were different: (1) the late Cretaceous ages in the Lufeng 13 fault structural belt; (2) the late Cretaceous and early Cretaceous-Jurassic ages in the Huizhou 21 buried hill-fault belt; (3) the Jurassic and Triassic ages in the Xijiang 24 buried hill-fault belt; and (4) the early Cretaceous – late Jurassic ages in the Panyu 4 oil area. These detrital feldspar 40Ar/39Ar ages become younger and younger from west to east, corresponding to the age distribution of the granites in the adjacent Guangdong Province, Southern China.     

四川盆地龙潭向斜砂岩型铀矿成矿条件分析

通过对四川盆地龙潭向斜区域地质背景、找矿目的层侏罗系沙溪庙组和遂宁组地层特征、砂岩岩性岩相发育特征及地球化学特征的研究,笔者认为,目的层内灰色砂体发育,黄色砂岩为其蚀变产物。通过对砂岩型铀矿化特征的研究,综合分析了该区砂岩型铀矿成矿条件,认为该区具有较好的铀成矿环境和找矿前景。     

松辽盆地南部白兴吐地区油气后生还原对铀成矿的作用

白兴吐地区姚家组铀矿化岩石中有机炭和有机硫都较低,而矿石中烃类含量比围岩高数至数十倍,油气对砂岩型铀矿成矿作用明显。油气及热液沿断裂上升,热事件有利于CH4在溶液中发生TSR反应,并加速铀的沉淀。断裂及油气是该区铀矿化的主要因素。     

鄂尔多斯盆地姬塬油田上三叠统延长组超低渗透砂岩储层微裂缝研究

通过对鄂尔多斯盆地姬塬油田上三叠统延长组长4+5油藏的精细描述,指出微裂缝对提高储层渗流能力、提高超低渗透油藏开发效果具有十分重要的意义。研究表明,鄂尔多斯盆地姬塬油田上三叠统延长组长4+5油藏微裂缝线密度为7.86条/cm,微裂缝开度为3.70μm,微裂缝间距为1.2723mm,微裂缝孔隙度为0.29%,微裂缝渗透率为332×10-3μm2。微裂缝孔隙度是基质孔隙度的2.74%,微裂缝渗透率是基质渗透率的12.15倍。微裂缝分布的差异性和不均一性是造成研究区超低渗透致密储层中有相对高渗透层的主要原因。微裂缝发育及展布状况是沉积微相带及基底断裂基础上成岩过程中多期古构造应力场与现今构造应力场共同作用的结果。在油气勘探中以寻找有利的沉积相—成岩相—微裂缝带为勘探目标,会加大勘探成功率。     

Zircon alteration,formation and preservation in sandstones

Zircon textures, chemistry and microstructures have been characterized in situ within Carboniferous sandstones from the Midland Valley of Scotland using back‐scattered electron and cathodoluminescence images, electron backscatter diffraction techniques and chemical analyses. The study of polished thin sections reveals a variety of zircon types including unmodified detrital zircon, zircon outgrowths and different forms of modified zircon that formed in low‐temperature conditions within the sedimentary rocks. These rocks have only experienced temperatures of <100 °C during burial; however, altered zircon is abundant and characterized by a low mean atomic number, with relatively high contents of non‐formula elements and a nano‐crystalline or microcrystalline structure. It forms by replacement of detrital zircon that subsequently became metamict. Two types of replacement mechanisms are effective in sedimentary environments and involve either dissolution–reprecipitation or solid‐state reaction, but both require fluid access to the radiation‐damaged areas. The former process appears to become the dominant replacement mechanism as temperature increases and produces highly porous, inclusion‐rich zircon. Metamict zircon is extremely reactive in near‐surface conditions and the production of low‐temperature zircon is sensitive to both parent zircon characteristics and environmental conditions. As such, the alteration of zircon has the potential to yield unique information on the diagenetic history of sedimentary rocks. Low‐temperature zircon would be unlikely to survive sedimentary transport or the rock crushing procedures that characterize many investigations of detrital zircon populations and consequently may generate severe biases in studies of this type.     

胜利油田东营凹陷流体—砂岩相互作用期次及其识别标记

胜利油田东营凹陷主要储层砂岩自始新世形成以来经历了至少四期流体的活动,这四期流体与砂岩的相互作用通过矿物溶解、胶结及脉体充填等成岩事件而表现出来。作用过程中溶解作用使砂岩孔隙度增加,改善储层质量;而胶结作用通常使孔隙度减少,伤害储层或破坏储层,但早期胶结作用形成的粗晶碳酸盐矿物可以支撑格架颗粒,阻止后期的压实而导致孔隙“坍塌”。通过东营凹陷坨胜永断裂带和中央背斜及凹陷带沙三段（Es3）和沙四段（Es4）段储层砂岩薄片镜下观察,胶结物电子探针成分分析,综合其它资料得出:第一期流体与砂岩相互作用发生在孔店晚—沙四晚期,以方解石＋石膏胶结为标志;第二期发生在沙三—东营（Ed）末,以粗晶“马鞍状”白云石为标志;第三期发生在馆陶(Ng)沉积时期,以微晶含铁白云石为标志;第四期发生在馆陶沉积之后,以铁白云石脉为标志。     

塔里木含油气盆地沉积学研究进展

随着近年来塔里木盆地油气勘探的深化,各主要目的层的沉积学研究取得了长足的进展:对轮南-塔河亿吨级油田为代表的奥陶系碳酸盐岩非均质古岩溶储层形成机理认识的进步及其地震识别技术的建立,极大地提高了勘探成功率;近年来油气勘探新突破也展示了轮南奥陶系主风化壳区外围台地边缘区带存在广阔的勘探前景;以哈得4亿吨级油田为代表的上泥盆统-下石炭统东河砂岩滨岸穿时砂体层序地层格架及其分布模式的建立,拓宽了东河砂岩岩性圈闭及岩性-构造复合圈闭油气藏的勘探领域;以英南2气田为代表的侏罗系低孔低渗砂岩储层-含水网状粘土胶结砂岩因水锁效应成为气藏直接盖层的特殊储盖组合的发现,拓宽了天然气勘探领域;以克拉2特大型气田为代表的高压气藏储盖组合(干旱气候下形成的下白垩统巴什基奇克组辫状河三角洲及扇三角洲巨厚砂岩储层-早第三纪海湾-蒸发泻湖环境沉积的巨厚膏盐泥岩优质盖层),在库车及塔西南等地区普遍分布,具有广阔的勘探前景。     

柴达木盆地西南区古近系及新近系砂岩储层

根据40余口钻井的岩石学资料,较系统地描述了柴达木盆地西南区古近系及新近系的砂岩储层特征：（1）砂岩储层的岩石（矿）成分在时空上呈现规律性的变化。在研究区东南和西北两侧,砂岩成分成熟度和结构成熟度均比中部地区明显偏低;从古近系到新近系,砂岩的成分成熟度和结构成熟度均逐渐降低,这与区域上由早到晚构造活动逐渐增强是一致的。砂岩储层岩石学的这种变化明显地影响到其储集性质,本区东南和西北两侧砂岩储层性质比中部地区变差即与此有关。（2）砂岩储层的孔隙类型以原生孔隙为主。前人大都认为本区砂岩储层的孔隙类型以次生孔隙为主,尤其是下干柴沟组,主要发育次生孔隙。本文认为古近系及新近系砂岩储层以原生孔隙为主,其次为胶结物溶孔和碎屑颗粒溶孔,次生孔隙仅在有限程度上改善了砂岩的储集性质。因此研究砂岩储层的原生孔隙的发育规律是比较重要的。（3）压实作用的差异是造成储集性质变化比较大的主要因素,其次为胶结作用。压实作用的大小受到埋藏深度和岩性的影响,也与储层所经历的埋藏方式有关。本区砂岩储层中的胶结物以方解石和硬石膏为主,也见少量方沸石。不同层段砂岩中的碳酸盐胶结物含量为4.0%～16.0%,局部地区硬石膏胶结物含量可达11.5%～28.0%,成为影响储集性质的主要因素。     

日本白山地区甚之助谷特大型滑坡的变形机制

甚之助谷滑坡是位于日本白山地区的特大型滑坡。其长约为2000m．宽500m。滑坡由中侏罗系一早白垩系的手取层群砂岩一页岩互层组成。7年来的地表变形观测结果表明．由于变形速度的差异,该滑坡可以分成上下两个部分。上部的变形速率为80～170mm／a的速度．而下部则相对稳定(3～15mm／a)。观测数据还显示了水位变动对滑坡位移造成的明显影响。变形观测和现场观察的结果证实该边坡的顺向坡结构和互层的风化效应是该滑坡变形的最基本因素。