Distinctive erosional and depositional structures formed at a canyon mouth: A lower Pleistocene deep‐water succession in the Kazusa forearc basin on the Boso Peninsula,Japan

The canyon mouth is an important component of submarine‐fan systems and is thought to play a significant role in the transformation of turbidity currents. However, the depositional and erosional structures that characterize canyon mouths have received less attention than other components of submarine‐fan systems. This study investigates the facies organization and geometry of turbidites that are interpreted to have developed at a canyon mouth in the early Pleistocene Kazusa forearc basin on the Boso Peninsula, Japan. The canyon‐mouth deposits have the following distinctive features: (i) The turbidite succession is thinner than both the canyon‐fill and submarine‐fan successions and is represented by amalgamation of sandstones and pebbly sandstones as a result of bypassing of turbidity currents. (ii) Sandstone beds and bedsets show an overall lenticular geometry and are commonly overlain by mud drapes, which are massive and contain fewer bioturbation structures than do the hemipelagic muddy deposits. (iii) The mud drapes have a microstructure characterized by aggregates of clay particles, which show features similar to those of fluid‐mud deposits, and are interpreted to represent deposition from fluid mud developed from turbidity current clouds. (iv) Large‐scale erosional surfaces are infilled with thick‐bedded to very thick‐bedded turbidites, which show lithofacies quite similar to those of the surrounding deposits, and are considered to be equivalent to scours. (v) Concave‐up erosional surfaces, some of which face in the upslope direction, are overlain by backset bedding, which is associated with many mud clasts. (vi) Tractional structures, some of which are equivalent to coarse‐grained sediment waves, were also developed, and were overlain locally by mud drapes, in association with mud drape‐filled scours, cut and fill structures and backset bedding. The combination of these outcrop‐scale erosional and depositional structures, together with the microstructure of the mud drapes, can be used to identify canyon‐mouth deposits in ancient deep‐water successions.     

龙门山南段青衣江阶地沉积物的化学风化特征及其意义

本文通过对龙门山南段青衣江阶地的研究, 尝试以常量元素所体现的风化特征, 来解决阶地对比的问题, 并取得了一定的进展。通过主量元素的分析, 发现CIA指标、 A-CN-K三角模型等, 在区分不同年龄的阶地有很好的效果, 而且沉积物砾石之间的基质颜色也一定程度地反映了新老关系。结合流域内更古老洪积扇的研究, 发现河流阶地在距今200ka内化学风化速度较稳定, 但更老的地貌面风化呈现非线性。另外, 在本文研究的600ka时间尺度内, 阶地风化速度与全球气候变化相关, 体现为冰期风化速度慢, 间冰期风化速度快, 并具一定的滞后效应。     

PALEOGENE(?) DEPOSYSTEMS AND BASIN EVOLUTION IN THE EASTERN TIBETAN PLATEAU: NANGQIAN AND XIALAXIU BASINS

PALEOGENE(?) DEPOSYSTEMS AND BASIN EVOLUTION IN THE EASTERN TIBETAN PLATEAU: NANGQIAN AND XIALAXIU BASINS     

乌里雅斯太凹陷斜坡带湖底扇相砾岩体沉积特征与隐蔽油藏勘探

乌里雅斯太凹陷南洼槽斜坡带发育一套厚度大、粒级粗和相变快的砾岩体,根据岩心观察、岩电组合特征和地震相分析等手段,结合岩矿等分析化验资料,认为该套砾岩体属具补给水道的湖底扇相沉积。砾岩体夹于较深湖亚相的深灰色泥岩中,发育沉积物重力流成因的沉积构造,内扇、中扇和外扇等相带发育齐全,并具有多期发育的特点。物源区具有的线物源或多物源特征,以及极粗的粒级造成补给水道的稳定性较差、规模较小、迁移性较强,沿斜坡带形成了纵向上由南向北依次叠置、横向上叠加连片的多个湖底扇相砾岩体。坡度很陡的斜坡,特别是构造坡折带的存在控制了湖底扇的形成和发育,使湖底扇相砾岩体主要沿构造坡折带下部分布,具有很好的隐蔽油藏成藏条件,以中扇辫状沟道微相区最为有利,已有多口井发现厚油层并获工业油流,实现了隐蔽油藏勘探的重大突破。     

乌干达K油田扇三角洲沉积正演模拟与应用

乌干达K油田位于Albert盆地,由于钻井数较少,地震资料品质差,沉积储层空间分布预测存在严峻挑战.根据岩心、测井、古生物、重矿物、粒度分析等资料综合分析后认为,乌干达K油田属滨浅湖环境,发育受边界断层控制的近源扇三角洲沉积,物源方向位于油田东南部,以低能长期的水下分流河道牵引流搬运为主.在沉积主控因素定量分析的基础上,将可容纳空间变化、物源供应及沉积物搬运等参数定量表征,并在年代地层框架约束下,通过正演模拟,再现地质历史时期地层沉积演化过程,建立了三维储层砂岩分布概率模型,进一步认识了研究区各层砂体的空间分布特征.将沉积演化模拟的砂岩分布结果转化为三维地质建模的定量控制条件,对沉积相模型进行约束,建立了更符合沉积认识的高精度相控地质模型,实现了扇三角洲储层砂体定量预测与表征.     

Architectures and evolution of arid alluvial fans: Insights from a flume experiment

Using time-lapse cameras and a 3D laser scanner,74 groups of geomorphic data of alluvial fans were obtained through flume experiments. Then a detailed sedimentary analysis based on these data was performed by using a quantitative software to reveal the sedimentary evolution process of the arid alluvial fan and its depositional architecture. Results suggest that there are obvious differences in hydrodynamics,water flow patterns and growth pattern during the evolution of arid alluvial fans. Based on these differences,the experiment is divided into three stages,including an early,middle,and late stage. In the early stage,the fan surface hydrodynamics was relatively strong,and the sheet flow dominated the deposition. According to the distribution of sheet flow deposits,it can be divided into wide-spread sheet flow deposition and local sheet flow deposition. In the middle period of the experiment,the hydrodynamic strength and expansion rate at the middle-distal part of the fan body reduced. The non-confined channel which is close to the source dominated the deposition,and terminal lobe was mainly deposited on the edge of the river channel. In the late stage of the experiment,the hydrodynamic further reduced causing by the large fan surface and confined channels were the main deposits. Through the flume experiment,an arid alluvial fan depositional architecture model with a three-layer structure has been established. The bottom layer is of a sheet flow lobe complex,the middle layer is characterized by unconfined channels and terminal lobes,and the top layer is constituted by stacked confined channels and small terminal lobes.     

东濮凹陷濮卫环洼带沙三段沉积体系及储层发育规律

为了提高东濮凹陷濮卫环洼带隐蔽油气藏的勘探精度,以层序地层学理论和瓦尔特相律为指导,通过钻井岩芯、测井和地震的三元分析法,综合构造-地层分析,在东濮凹陷濮卫环洼带沙三段共识别出湖底扇、滨浅湖砂坝-风暴、低位盐湖、三角洲、深湖-半深湖等五种沉积体系,分析了主要储层发育期沉积体系的时空展布特征,探讨了层序地层体制下沙三段的沉积体系发育模式及储层发育规律,指出环洼带东部及北部水下河道与坡折带的交汇处是储层的主要发育地带,其沉积体系主要为湖底扇、三角洲沉积体系.     

丽水凹陷远岸水下扇体识别及特征分析

在丽水凹陷西次凹西部斜坡带发育多条坡折断层,它们控制了古新统明月峰组下段远岸水下扇体的发育。钻井揭示该区水下扇体具有沉积厚度大、物性好、含油气性活跃的特征。储层特征描述、分布范围预测对寻找本区岩性油气藏具有重要意义。本文通过对明月峰组沉积初期古地貌恢复,总结了坡折断层对扇体发育的影响作用。坡折断层上升盘发育孤立型和复合型水道;坡折断层下降盘发育扇体主体,扇中水道微相为优势相带,岩性以灰色细砂岩为主,存在反映垮塌变形的泄水、泥质火焰等沉积构造,测井相表现为低伽马、高自然电位异常,地震相为强振幅、低频、断续反射。同时,利用地震沉积学技术完成了本区3期次扇体分布范围识别,说明自早期到晚期扇体具有从北往南逐渐迁移的特征。     

测高数据不准时的直升机航空瞬变电磁一维反演方法理论研究

航空电磁勘探中,高度计显示的发射线圈高度数据往往是不准确的,这可能会影响反演结果,出现假异常现象.针对这一情况,提出了一种高度计数据不准确条件下的航空瞬变电磁资料一维反演方法,在重构地电参数的同时也对发射线圈高度值进行校正.由于航空电磁反演问题是典型的病态问题,使用正则化反演方法,正则化因子由数据目标函数与模型目标函数之间的关系以自适应方式给出,使得反演迭代能稳定进行.以直升机航空瞬变电磁资料反演为例,用理论模型响应数据加入噪声进行反演,结果表明,无论初始高度值是高于真值还是低于真值,该反演方法均能够较好地重构地下介质参数和发射线圈高度值;作为反演初值的发射线圈高度测量值越准确时,反演迭代收敛速度就越快,反演效果也越好.     

新疆克拉玛依油田八区上二叠统下乌尔禾组河控型扇三角洲沉积

从岩心、薄片等实际资料着手,结合EMI成像测井等现代技术研究,认为新疆克拉玛依油田八区上二叠统下乌尔禾组属河控型扇三角洲相沉积,并识别出两种亚相和9种微相：2种亚相是扇三角洲平原和扇三角洲前缘亚相,而前扇三角洲不发育。9种微相是辫状河道沉积、漫流沉积、泥石流沉积、筛滤沉积、水下分流河道沉积、水下分流河道间沉积、水下天然堤沉积、碎屑流沉积及颗粒流沉积。同时,以成像测井资料为主要依据,结合岩石粒度及成分特征分析,表明研究区下乌尔禾组5个时期的物源方向不尽一致,表现为从早到晚,由第5亚期至第1亚期,物源方向由以西南方向为主,逐渐变为以西北为主。与物源变化相对应,沉积相也呈现有规律的变化。本文在对沉积相进行详尽研究的基础上,深入解剖了克拉玛依油田上二叠统下乌尔禾组的沉积微相特征,阐明了沉积相的展布和演化。