Autogenic avulsion,channelization and backfilling dynamics of debris‐flow fans

Alluvial fans develop their semi‐conical shape by quasi‐cyclic avulsions of their geomorphologically active sector from a fixed fan apex. On debris‐flow fans, these quasi‐cyclic avulsions are poorly understood, partly because physical scale experiments on the formation of fans have been limited largely to turbidite and fluvial fans and deltas. In this study, debris‐flow fans were experimentally created under constant extrinsic forcing, and autogenic sequences of backfilling, avulsion and channelization were observed. Backfilling, avulsion and channelization were gradual processes that required multiple successive debris‐flow events. Debris flows avulsed along preferential flow paths given by the balance between steepest descent and flow inertia. In the channelization phase, debris flows became progressively longer and narrower because momentum increasingly focused on the flow front as flow narrowed, resulting in longer run‐out and deeper channels. Backfilling commenced when debris flows reached their maximum possible length and channel depth, as defined by channel slope and debris‐flow volume and composition, after which they progressively shortened and widened until the entire channel was filled and avulsion was initiated. The terminus of deposition moved upstream because the frontal lobe deposits of previous debris flows created a low‐gradient zone forcing deposition. Consequently, the next debris flow was shorter which led to more in‐channel sedimentation, causing more overbank flow in the next debris flow and resulting in reduced momentum to the flow front and shorter runout. This topographic feedback is similar to the interaction between flow and mouth bars forcing backfilling and transitions from channelized to sheet flow in turbidite and fluvial fans and deltas. Debris‐flow avulsion cycles are governed by the same large‐scale topographic compensation that drives avulsion cycles on fluvial and turbidite fans, although the detailed processes are unique to debris‐flow fans. This novel result provides a basis for modelling of debris‐flow fans with applications in hazards and stratigraphy.     

The effects of channelization on a high-energy river

Extensive channelization of a high-energy river in Montana was accomplished during 1957–1958. The technique applied was the same throughout, even the fluvial characteristics are considerably different in the and downstream segments of the river. In the braided reach, rubble dikes composed of river bedload that was against the channel banks prevent the river from high-stage channels which traverse the lowest surface in the valley. The river has responded by altering its hydrologic characteristics at any given discharge and by accelerating the lateral erosion where banks have been left unprotected. Downstream, where the river is in a single-channel pattern, the dikes have been destroyed because the meandering thalweg, repeatedly shifting its position and impinging against the base of the dikes, provides the force needed to erode the boulders comprising the dikes. Some bank protection is provided by riprap composed of large sandstone blocks. This method works, however, only if long segments of the channel are riprapped. The various responses of the river in reaches having different channel patterns indicates that some knowledge of local fluvial mechanics must be obtained prior to the channelization.     

贵州赤水及邻区裂缝性气藏模式探讨

以“三结合”为基础，建立了本研究区碳酸盐岩裂缝性气藏模式。该模式对本区二，三纱裂缝性气藏的构造发展与演化配置关系，构造裂缝与油气成藏关系，储集体成藏机理与成藏关系进行了全面系统的“三分析”，归纳出十基成藏规律。     

Formation Models and Distribution of Oil and Gas Pools in Tarim Basin,China

This article reports the main formation models and distribution of the oil and gas pools in Tarim basin,China,including (I) occurrence of the found oil and gas pools,(2) main formation models of oil and gas pools,and (3) distribution law of oil/gas pools.Petroleum is distributed widely in the strata of Tarim basin from the Sinian at the bottom to the Neogene at the top.However,the found oil and gas fields are mainly distributed in Shaya (沙雅) uplift,Tazhong (塔中) uplift,and Kuche (库车)depression.This article presents 4 main formation models,namely,early formation and long-term preservation,early formation and late reformation,middle-late multiphase-multisource formation,late single-stage formation.Tarim basin is very rich in petroleum resources.Long-term inherited intrabasinal paleohighs and slope zones are the most favorable areas for accumulation of hydrocarbons,but the types of oil and gas pools are different from area to area.The control of unconformities and faults on hydrocarbon accumulating is prominent in Tarim basin.Preservation conditions are of utmost importance.Formation of some oil and gas pools is the result of reforming and re-accumulating of early accumulated hydrocarbons.     

酒西坳陷青西凹陷富油的地质-地球化学因素分析

青西凹陷下白垩统暗色半深湖相-深湖相的泥岩、白云质泥岩和泥质白云岩为研究区主力烃源岩,其沉积时为整体上处于封闭-半封闭强还原-还原环境的断陷湖泊,有利于有机质的保存和转化,且烃源岩厚度占地层比例均大于 5 0%以上,加之有机质类型以混合型为主、有机碳含量普遍大于 1%,为油田形成提供了重要的物质基础。喜山期构造运动形成了许多挤压逆断层、剪切性断层和构造缝,造成地层和构造叠覆,为有机质成熟、运移和聚集提供了动力和空间,从而为该区油藏的形成提供了有利条件.     

凝析气藏的成因类型与成藏模式

根据凝析气藏形成过程中相态变化,可将其分为原生凝析气藏和次生凝析气藏。原生凝析气藏是有机质直接生成凝析气,并以气相运移聚集成藏,成藏过程中不存在相态变化。次生凝析气藏是圈闭中轻质油溶解于天然气中形成的凝析气藏,成藏过程中流体相态发生了变化。本文从两类凝析气藏的地质、地球化学特征分析入手,分析了凝析气藏的成藏模式和剖面上的相态分布,最后指出了区分二者的意义。     

泌阳凹陷栗园地区基岩油藏石油地质特征

泌阳凹陷栗园地区在基岩露头发现油气显示并钻遇基岩油藏,研究其地质条件和油气成藏过程对指导凹陷油气勘探具有重要意义。以露头、地震、钻井、测录井、岩心、地化资料为基础,深入分析栗园地区基岩油藏形成的油气成藏要素和成藏过程。研究认为：生烃洼陷内核桃园组地层形成的油气在鼻状构造背景下通过断裂－砂体复合输导体系向基岩内运移并聚集成藏。中元古界大河群蔡家凹组大理岩在构造作用下发育高角度剪切构造缝和溶蚀孔洞,孔渗性能良好,是主要基岩储层。上覆孤山头组片岩、边界断层泥、上盘泥页岩和稳定基岩内幕水动力条件为油气提供有效保存条件。栗园地区基岩油藏成藏模式分析可为同类型断陷盆地基岩油藏油气勘探提供借鉴。     

中国南方古油藏与油气评价

从早古生代至中、新生代，中国南部确实形成过相当数量和相当规模的油气藏。而后经较高的演化和多期次的构造运动，最终成为古油藏。如麻江、瓮安、泰山、米仓山、天井山、中和、龙街及小古山等古油藏。它展示了分布于中国南方各地质时期及各种地质条件下，油气藏形成、发展的全过程及其规律，充分揭示了油气藏的成藏、发展条件及破坏因素。因而运用其成藏规律，可以为油气远景评价、勘探部署做出重要的决策。     

Stratigraphic and Ecophysical Characterizations of Salt Pools: Dynamic Landforms of the Webhannet Salt Marsh,Wells, ME,USA

Salt pools are water-filled depressions common to north-temperate salt marshes. In Wells, ME, USA, cores reveal a unique salt pool signature consisting of water-saturated dark-gray mud often containing fragments of Ruppia maritima. Cores through pool sediment reenter salt marsh peat, not tidal flat sediment, demonstrating that most pools are of secondary origin. A principal component analysis of attribute data collected from 119 pools defines three distinct pool types: those with (1) surrounding high-marsh vegetation and thick heavily undercut banks (40% of the variance), (2) surrounding low-marsh vegetation and thicker slightly undercut banks (18% of the variance), and (3) surrounding low-marsh vegetation and less thick moderately undercut banks, containing R. maritima and a surficial drainage (15% of the variance). Cores and spatiotemporal analyses of aerial photographs between 1962 and 2003 reveal dramatic salt marsh surface dynamism suggesting that salt pools influence the geomorphological evolution of coastal marshes.     

再论流体势及其与圈闭和油气藏关系

在Hubbert(1953)关于流体势和圈闭的经典论文基础上,从流体势计算的基本原理出发,论证了气势与水势、油势计算表达式的具体形式是不同的,如等地温梯度的静水压力场中理想气体的势包含压力的对数函数与线性函数之和,而不只是包含压力的线性函数.表述了同一求势面所对应的测势面对于不同流体是不同的;指出了圈闭的溢出点通常是等势面与非渗透层面交线的切点;应用简洁的数学分析方法,推导了地下水三维流动情形下油(气)等势面某点切平面坡度与水头、渗滤速度关系的表达式,其中坡度绝对值与渗滤速度关系的表达式为:tanθ=√v2x v2y/|vf vz|,其中vf=K[ρw-p(p)]g/μ,式中:θ为切平面的倾角;vx、vy和vz分别为沿坐标轴ox、oy和oz方向的渗滤速度分量;K和μ分别为渗透率和水的动力黏度;ρw、ρ(p)分别为水和油(气)的密度.根据这些基础性的分析,对被广泛引用的Levorsen(1954)的背斜-水动力复合油藏中水头与油水界面产状的关系示意图进行了两点修改:将油水界面改为曲面、将油水界面处油藏的测势面改为高于油水界面处水的测势面的水平面;对向斜部位聚集油气的水动力条件进行了讨论,认为只有两(各)翼水流都向下流动且水流强度中等条件下才能在向斜部位聚集油气.     

中国煤型气区的构造环境、典型气藏及勘探方向Ⅱ——中、新生界煤型气

本篇论述中、新生界煤型气的有关问题。中生界煤型气资源集中分布在北方,气源岩以侏罗纪煤系为主,以西北区资源前景最好。其中吐—哈盆地最具代表性,构造环境反转是本区煤层气形成并富集的特殊构造条件。新生界煤型气资源则集中分布于大陆架裂谷系,第三纪煤系为主力气源岩,裂谷高温构造环境是源岩热演化生烃的有利条件,而背斜—断层圈闭是最有利成藏的构造类型。崖13-1气田为本区典型代表并具自生自储的特点。     

中国煤型气区的构造环境、典型气藏及勘探方向Ⅱ--中、新生界煤型气

本篇论述中、新生界煤型气的有关问题。中生界煤型气资源集中分布在北方,气源岩以侏罗纪煤系为主,以西北区资源前景最好。其中吐-哈盆地最具代表性,构造环境反转是本区煤层气形成并富集的特殊构造条件。新生界煤型气资源则集中分布于大陆架裂谷系,第三纪煤系为主力气源岩,裂谷高温构造环境是源岩热演化生烃的有利条件,而背斜-断层圈闭是最有利成藏的构造类型。崖13-1气田为本区典型代表并具自生自储的特点。     

马岭—镇北地区延长组长8油组的砂体类型与多层叠置的连续型油藏特征

重点通过对马岭—镇北地区长8油藏储层的研究,将研究区长8油藏的储层砂体类型划分为2大类4小类：水道砂体（水下分流河道、水下深切水道、扇内水道）、河口坝砂体。在其它成藏条件的有机配置下,形成了以上述4种类型砂体为储层的多层叠置的连续型油藏。其特征为：①油藏分布在湖盆斜坡和中心位置的砂体连片叠置的沉积体系中;②4类储层单砂...     

The Isotope Geochemistry of N2 in Natural Gas Pools

ＩＮＴＲＯＤＵＣＴＩＯＮＭｏｌｅｃｕｌａｒｎｉｔｒｏｇｅｎ（Ｎ２）ｉｓｏｎｅｏｆｔｈｅｍｏｓｔｃｏｍｍｏｎｎｏｎｈｙｄｒｏｃａｒｂｏｎｃｏｍｐｏｎｅｎｔｓｉｎｇａｓｐｏｏｌｓ（Ｚｈｕ,１９９４）．Ｎ２ｒｉｃｈｇａｓｐｏｏｌｓｈａｖｅｂｅｅｎｄｉ...     

中国碳酸盐岩油气藏探明储量分布特征

通过对我国1465个碳酸盐岩油气藏(或储量计算单元)探明储量的统计分析研究,提出了"生储组合分类法",并把这些碳酸盐岩油气藏类型划分为湖相型、海生海储型、新生古储型和新生新储型四类。石油地质储量以海生海储型和新生古储型为主,分别占碳酸盐岩油气藏石油总储量的40.11%和37.12%;天然气地质储量则以海生海储型独占绝对优势,占碳酸盐岩油气藏天然气总储量的93.28%。从油公司、盆地、层系、埋深以及油品等多角度进行了探明储量分布特征的研究,揭示了各种分布规律。     

A Comprehensive Study of Silica Pools and Fluxes in Wadden Sea Salt Marshes

As an essential nutrient for diatoms, silica plays a key role in the estuarine and coastal food web. High concentrations of dissolved silica (DSi) were found in the seepage water of tidal freshwater marshes, which were therefore assumed to contribute to the silica supply to estuarine waters in times of silica limitation. A comprehensive budget calculation for European salt marshes is presented in this study. Earlier, salt marshes were considered to have even higher silica recycling rates than tidal freshwater marshes. Between 2009 and 2011, concentrations, pools and fluxes of silica in two salt marshes at the German Wadden Sea coast were determined (in soil, pore water, aboveground vegetation, freshly deposited sediments and seepage water). Subsequently, a budget was calculated. Special emphasis was placed on the influence of grazing management on silica cycling. Our results show that the two salt marshes were sinks for silica. The average import of biogenic silica (BSi) with freshly deposited sediments (1,334 kmol km^?2 year^?1) largely exceeded the DSi and BSi exports with seepage water (80 kmol km^?2 year^?1). Grazing management can affect silica cycling of salt marshes by influencing hydrology and vegetation structure. Abandoned sites had larger DSi export rates than grazed sites. One third of all BSi imports occurred in only one major flooding, underlining the relevance of rare events in the silica budget of tidal marshes. This aspect has been widely neglected in earlier studies, what might have led to an underestimation of silica import rates to tidal marshes hitherto.     

Application of Biomarkers to Quantitative Source Assessment of Oil Pools

Recent detailed organic geochemical and geological investigation indicate that oils of the Bamianhe oilfield, Bohai Bay Basin, East China are the mixture of less mature oils and normal oils derived from the ES4 mudstones and shales with a wide range of thermal maturity from immature to middle-maturity, and most of the oils were proved to be sourced from the depocenter of the Niuzhuang Sag immediately adjacent to the Bamianhe oilfield. Two approaches to quantify the amount of immature oils mixed through quantitative biomarkers were established. One is a relatively simple way only through organic geochemical analysis while the other is to be combined with basin modeling. Selecting biomarkers as proxies is the crucial point in both of them. The results show that the less mature oils mixed in the Bamianhe oilfield is less than 10% and 18% respectively based on the two approaches, which coincide with the results of oil-source rock correlation.     

海相碳酸盐岩层系不整合量化研究及其意义——以四川盆地北部二叠系为例

本文以四川盆地北部二叠系为例,将层序地层分析和沉积盆地波动过程分析相结合,提出了运用沉积波动过程分析研究沉积记录不完整性的量化方法,该方法可以相对准确地定量描述盆地形成演化过程中的升降运动,恢复无地层"记录"中的沉积-剥蚀过程,进而定量分析盆地的沉积-剥蚀过程、计算沉积间断(不整合)内的地层剥蚀量、认识其时空分布规律.同时,通过实际钻井及"人工井"的波动过程分析,结合地震剖面解释成果,可以作出主要不整合的空间分布图、各层位的剥蚀厚度图和原始厚度图、各期构造的剥蚀量分布图等重要基础图件,为盆地进一步系统分析及盆地模拟打好基础,结合沉积相研究及构造样式分析还可分析盆地沉积中心、生油层、盖层、储层等在时空中的变化规律.由于沉积盆地的升降波动过程直接影响着盆地的埋藏史、热史和生、排烃史,因此通过沉积波动过程的系统分析不仅能正确建立盆地演化的地质模型,还可以正确认识油气形成与分布规律,有效指导油气勘探.     

四川盆地威远气田和资阳含气区震旦系油气成藏差异性研究

本文通过对四川盆地元古宇-下古生界勘探最成功的两个地区--威远震旦系气田和资阳震旦系含气区天然气成藏要素和成藏过程的详细比较,得出 ①资阳含气区和威远气田的原始烃源相同,均是下寒武统生成的油裂解的天然气,不同的是资阳为残留的气顶气,威远是水溶气脱溶气.②资阳含气区和威远气田震旦系碳酸盐岩基质孔隙度相近,资阳地区溶蚀洞穴发育,但裂缝不发育,储层渗透性较差,非均质性强;威远地区储层洞穴不发育,但裂缝发育,形成统一的裂缝-孔洞系统.③威远地区具有统一的圈闭,闭合度高(800 m),闭合面积大(895 km2).资阳含气区不具有统一的圈闭,多为局部的小高点.④喜马拉雅期隆升作用使资阳统一含气区分散化和气藏变小,形成多压力系统的含气区;威远地区快速大幅度隆升, 溶于水中的天然气脱溶, 形成具同一压力系统的整装气田.⑤资阳含气区的成藏过程为 (资阳-威远)古油藏→原油裂解→气顶天然气→隆升调整→现今(残留)含气区,其天然气藏是隆升调整成藏,是在原古气藏的基础上改造残留而成;威远地区的成藏过程则是(资阳-威远)古油藏→原油裂解→天然气大量溶于水中→隆升使得带有大量天然气的水向威远运移和天然气脱溶→现今(新生)气藏,属天然气的脱溶成藏.资阳含气区受古构造的控制明显;威远气田则主要受今构造的制约.因此, 在四川盆地震旦系和下古生界的油气勘探中, 既要研究其古构造的特征和演化, 也要研究今构造的特征和分布规律, 才能发现不同类型的天然气藏.     

从地震信息看中国东部和中国中西部沉积盆地构造演化动力学与断块油气藏(下) 中国中西部盆地演化及断块(圈闭)油气藏

中国中西部地区以塔里木盆地及其演化为典型代表。震旦纪以来,经历了地台发育、持续沉降、拉张翘倾、挤压坳陷及断陷推覆等构造发育阶段,与中国东部一样,表现为拉张与挤压交互出现的手风琴式演化史,突出的差别在于晚喜马拉雅期在西部地区形成强烈的挤压逆掩推覆构造,而东部地区只形成坳陷式的沉积盆地。中亚—蒙古大洋、秦—祁—昆大洋、古特提斯洋、中特提斯洋、印度洋以及印度板块等在不同地质时期的板块活动是中国中西部地区盆地演化发展的动力学因素。根据地震剖面解释成果,可确定出四种断块油气藏类型,均反映后期挤压逆冲特征,尤其是燕山期—喜马拉雅期推覆前锋带断块油气藏,还可区分为拆离型、褶皱型、前冲型和反冲型等四种,且每一种还可再区分出若干种。