柴西咸水泉地区下油砂山组湖相沉积特征——以咸东1井取心段为例

【目的】勘探实践表明,柴达木盆地剩余油主要集中于西部地区,但受复杂地表及低渗储层的影响,勘探程度相对较低。为提高柴西咸水泉地区地质认识,可进一步加快油气勘探。【方法】基于岩心沉积构造,结合岩石薄片、X衍射全岩分析化验和地震反射等资料,对咸东1井上新统下油砂山组取心段的沉积相进行综合研究。【结果与结论】(1)深灰—灰黑色灰质泥页岩中夹有灰色薄—中层块状层理细杂砂岩,砂体顶、底部与泥岩突变接触,底界面为明显凸凹不平的侵蚀面,侵蚀面之下的泥页岩中变形层理发育,砂体为沉积物再搬运的砂质碎屑流沉积;(2)深灰—灰黑色灰质泥页岩中夹有含介壳—陆源碎屑的砾屑灰岩和具明显变形层理的粉砂岩及粉砂质团块,其变形纹层清晰且具明显的变形方向,为滑塌碎屑沉积;(3)深灰—灰黑色灰质泥页岩主要夹有薄层灰色含云灰黏土质粉砂岩,泥页岩中发育水平层理及韵律层理等,粉砂岩中发育较多泥质纹层的小型单斜层理、上攀波痕纹理及厚互层层理,为半深—深湖沉积夹由沉积物重力流末期演变的较弱底流沉积。此外,盆地发育的不同时期在阿尔金山前较深水区可能具备发育类似咸东1井滑塌—沉积物重力流沉积储层的条件,尚需进一步研究。

坝上河-滩坝微相组合特征——以柴北缘南八仙油气田新近系下油砂山组为例

为了深入评价柴达木盆地北缘南八仙油气田新近系下油砂山组砂体的油气勘探前景以及预测有利勘探区带和勘探目标,在岩心观察和钻测井资料综合分析的基础上,通过岩石学特征、泥岩颜色、粒度特征、沉积构造等沉积相标志综合分析,再结合单井相及连井相对比,精细刻画出南八仙油气田下油砂山组坝上河-滩坝微相组合沉积特征,并剖析了研究区沉积微相平面展布特征。结果表明:新近系下油砂山组属于辫状河三角洲前缘-滨浅湖沉积体系,并主要发育坝上河-滩坝微相组合;坝上河可分为以河为主式、对称式和以坝为主式3种类型,并随着河流作用由强到弱,湖水阻力由弱到强,组合逐渐由以河为主式演变为对称式进而演变为以坝为主式;滩坝区别出有滩无坝及滩坝共生2种类型,其中有滩无坝的远岸滩砂发育规模较小,分布范围局限且较为零散,滩坝共生的近岸砂体面积较大呈席状分布,远岸砂体多孤立呈土豆状分布。最后,根据沉积微相的展布特征建立了研究区辫状河三角洲前缘-滨浅湖的沉积相模式,研究区的水下分流河道、周边的坝上河复合砂体及近岸滩坝是主要的优势储层。研究可为油气田下一步挖潜提供地质依据。

柴达木盆地红柳泉-跃东地区新近系下油砂山组沉积体系展布特征及控制因素

在层序地层学研究的基础上,对柴达木盆地红柳泉—跃东地区新近系下油砂山组作了细致的沉积相分析研究。下油砂山组发育冲积扇相、扇三角洲相、辫状河三角洲相、湖泊相和浊积相等几种沉积相类型,分析了其发育特征及分布范围。以识别出的4个三级层序为单位,详细分析了沉积相的平面展布特征:Ⅰ层序沉积时期,西北地区为冲积扇和扇三角洲、中西部地区为辫状河三角洲发育区;Ⅱ层序沉积时期,沉积相分布格局与Ⅰ层序基本一致;Ⅲ层序沉积时期,西北地区的冲积扇、扇三角洲发育范围有所缩小,中西部地区辫状河三角洲发育范围持续扩张,分布范围较前期增大;Ⅳ层序沉积时期,西北地区依旧发育冲积扇,中西部地区辫状河三角洲沉积快速地向东推进,辫状河三角洲前缘亚相已达研究区中心。结合构造、物源、气候等因素分析了沉积相展布及演化的控制因素。

南八仙油田下油砂山组砂岩成岩作用及孔隙演化

对柴达木盆地南八仙油田上新统下油砂山组(N12)储层砂岩成岩作用及孔隙演化进行了研究。研究发现,N12储层主要为一套辫状河三角洲和滨浅湖砂岩,储集岩主要为长石岩屑砂岩、岩屑砂岩和岩屑长石砂岩,经历了压实压溶、胶结、交代、溶蚀等多种成岩作用,其中压实压溶、胶结作用起主要的破坏作用,溶蚀作用起主要的建设性作用。目前N12储层砂岩达到早成岩B期向中成岩A期过渡阶段。储层砂岩经成岩演化其原生孔隙近一半被破坏,次生孔隙开始大量出现,但还是以原生孔隙为主要储集空间,孔隙演化经历了原生孔隙的破坏、次生孔隙的形成2个阶段。

柴达木盆地花土沟油区上干柴沟组-下油砂山组碳酸盐岩储层特征

柴达木盆地西部花土沟油区碳酸盐岩主要分布于上干柴沟组的上部和下油砂山组的底部 ,与砂岩、泥岩呈不等厚互层 ,单层厚度 0 .5～ 3m,累计厚度可达 10多米。其中藻纹层灰岩和藻叠层灰岩溶孔发育 ,分布范围广 ,厚度大 ,物性最好 ,是一种特殊的油气储层。藻纹层灰岩和藻叠层灰岩发育于相对稳定的滨浅湖环境 ,其发育规模和储层性质主要受沉积环境的稳定性、早期淋溶程度和晚期胶结充填强度的控制。

大风山风西构造下油砂山组藻灰岩储层分析

大风山风西构造下油砂山组优质储集层为藻灰岩层，包括藻泥晶灰岩、藻叠层灰岩和藻团块灰岩层。藻灰岩储层孔隙度为3.4%-13.1%，平均6.9%，渗透率为0.013-17.5μm^2，平均1.353μm^2。藻灰岩储集层储集空间主要为溶蚀孔。空隙结构类型主要有粗孔-中喉型、中孔-中喉型和中孔-小喉型。储层物性主要控制因素为风西地区下油砂山组沉积相、沉积微相及成岩作用。

乌南油田上新统下油砂山组储层成岩作用与微观孔隙特征研究

应用岩石薄片观察、铸体薄片图像分析、压汞实验等方法对乌南油田下油砂山组的成岩作用和储层微观孔隙结构进行了研究。研究表明,乌南油田下油砂山组的成岩作用类型有压实作用、胶结作用、溶蚀作用和交代作用,其中以胶结作用和溶解作用为主;研究区目的层段以微喉道为主,孔隙属小孔,孔喉分布均匀程度中等,孔隙连通性中等。

钻井高分辨率层序地层划分及其古生态响应--以柴达木盆地乌南地区下油砂山组为例

在年代地层框架内,以高分辨率层序基准面旋回识别层序界面,将柴达木盆地乌南地区南参2井下油砂山组划分为两个中期基准面旋回(三级层序)。由于沉积环境演化与层序基准面旋回是相互影响的,所以沉积相和反映沉积环境的古生态特征是基准面旋回的重要划分依据。钻井沉积相划分以西岔沟露头下油砂山组河流-湖泊相砂、泥岩沉积序列为参照,划分古生态有浅水、较深水、淡水、较咸水等类型。以上述方法划分单井层序后,建立了乌南地区下油砂山组等时层序地层格架,并分析了层序格架内基准面旋回与古生态特征的响应关系。

Reservoir formation conditions and key exploration & development technoloiges in the Yingdong Oilfield in western Qaidam Basin

Located in east part of Yingxiongling structural belt in the Qaidam Basin,the Yingdong oilfield has a extremely complicated ground condition.Due to no significant discovery,this oilfield was considered to have no favorable geologic conditions for formation of oil or gas reservoir.In the past few years,with continuous improvement in the mountain 3D seismic surveys and logging data interpretation,some breakthroughs were obtained in 2010,and the Yingdong oilfield,the largest-scale reserves of a single reservoir with highest organic matter abundance,most favorable physical property and optimal development efficiencies in the Qaidam Basin,had been discovered,the production capacity was up to 0.55×10^(6) t.Through detailed analyses of the Yingdong oilfield,some studies,such as hydrocarbon accumulation conditions and technical challenges,are carried out,and following conclusions can be achieved.The Yingxiongling area is located in Mangya hydrocarbon-generation sag in the west part of the Qaidam Basin,its oil sources are rich;the Neogene Xiayoushashan Formation and Shangyoushashan Formation are dominated by wide and gentle delta frontdshore-shallow lacustrine sediments with interbeds of sandstone and mudstone,the sandbodies are widely distributed with favorable physical condition,and the mudstone is the key caprock,combined with high-quality Paleogene hydrocarbon source rocks,a complete source-reservoir-cap assemblage can be formed.Large-scale detachment faults of the Yingdong area connect high-quality Paleogene hydrocarbon source rocks with middle-shallow buried structural traps,thus,reservoirs formed in the early stage are modified,and at the same time,hydrocarbons formed in the later stage continue to migrate and accumulate;in this way,the deep and shallow faults form a relay-style hydrocarbon transport system,and hydrocarbons are accumulated in the shallow structural traps in the later stage;in this area,the middle-shallow faults have good lateral plugging performance which is favorable for preservation of oil and gas.For complex landforms and reservoir features in the Yingdong area,the integral 3D seismic acquisition,processing and interpretation technology is developed for complex mountain areas to provide a reliable foundation for hydrocarbon exploration.For some problems in the Yingdong oilfield like long oil/gas-bearing intervals,great diffi-culty in identification of fluids,the development mode of multiple oil/gas/water systems in the long intervals is established,and the geologic modeling technology with constraint of multiple conditions on complex fault blocks is also developed.Thus,hydrocarbon accumulation mechanism in the Yingdong oilfield is clear,and some complex key technology of engineering are well solved,providing necessary geologic theories and technical supports for high-efficiency development and rapid production construction in the Yingdong oilfield.