珠江口盆地白云凹陷珠江组深水牵引流沉积特征及其地质意义

研究深水牵引流对古大洋环流重建、陆坡位置判断及沉积矿产和能源资源勘探具有重要意义。珠江口盆地白云凹陷中新统珠江组取心段发育丰富的、与远洋低密度浊流和半远洋-远洋悬移沉积有明显区别的深水牵引流沉积,产物包括平行层理细砂岩、双泥岩纹层、双向交错层粉-细粒砂岩、波状层理和脉状层理灰质粉-细粒砂岩、波状层理和脉状层理抱球虫灰岩、透镜状沙纹层理粉砂岩等岩石相类型。珠江组深水牵引流沉积的发现具有重要地质意义,由其可以推测自渐新世末(23.8 Ma)白云凹陷陆架坡折带形成之后就开始存在沿着陆架坡折带活动的深水牵引流,并可能影响和改变沉积物的物质组成和区域分布,这将为南海北部古大洋洋流循环重建起到重要启示作用。     

珠江口盆地白云凹陷早中新世深水层序模式

近年来深水勘探已成为寻找油气的重要领域,白云凹陷在早中新世经历了复杂的构造沉积环境,解剖深水层序模式有利于揭示深水沉积演化规律。通过井震结合及属性分析对白云凹陷早中新世层序地层进行研究,识别出3个层序界面:ZJSB1(23.8 Ma),ZJSB2(22 Ma),ZJSB3(21 Ma)。其中ZJSB1、ZJSB3为重大不整合面,ZJSB2为水道下切侵蚀面。与之对应的界面发育3套层序:ZJSQ1,ZJSQ2,ZJSQ3。由于白云凹陷构造运动及古地貌的差异性,总结了2套深水层序模式:水道—深海披覆泥层序模式与块状搬运复合体—砂质碎屑流深海扇—水道—深海泥层序模式,在不同的演化阶段,前者主要受海平面的变化控制,而后者是受构造和海平面双重影响的。而同一地质时期古地貌又控制了沉积发育,高地势区发育下切水道,而低洼区发育深海披覆泥岩。因此,深水层序模式下研究深海沉积单元,对指导深水沉积和油气勘探具有极其重要的意义。     

青藏高原东北缘永昌南山北麓洪积扇对气候变化与构造运动的响应

永昌南山位于河西走廊东段,北麓受丰乐断裂控制。丰乐断裂是祁连山东北缘冲断带的重要组成部分, 其晚第四纪活动地表行迹西起西大河东到西营河,2期普遍发育地貌面被错断并形成明显断层陡坎。用无人机对杜家团庄、周家庄、西营河河口3个地点进行航空测量,生成数字高程模型(DEM),提取各阶地和洪积扇的断层陡坎剖面,并对断层上下盘面进行线性拟合,计算得到了不同位置的垂直断距。在杜家团庄洪积扇T1和东大河阶地T3砾石层顶部采集黄土样品,用光释光方法测得年龄分别为(19.30±2.45)ka和(27.40±2.47)ka,结合前人测年结果,认为永昌南山北麓普遍发育的两期地貌面年龄分别为19.3~16.3ka和29.9~27.4ka,两期地貌面均形成于气候由冷变暖的过渡阶段。利用地貌面陡坎的位错量和年代数据,得到晚更新世以来丰乐断裂在杜家团庄处的垂直滑动速率为0.65~0.82mm/a,在周家庄处的垂直滑动速率为0.60~0.76mm/a,在西营河河口处的垂直滑动速率为1.99~2.56mm/a。     

西湖凹陷平西地区古沟谷内隐蔽油气藏潜力

西湖凹陷平湖油气田经多年的勘探开发,取得了丰硕的成果,但也面临着后备储量不足的严峻现状。油气田西部的平西地区,占地面积大、研究程度低,是发现新增资源量的潜在地区。利用三维地震资料,从古地貌着手,在平西地区自南向北识别出多个古沟谷,其限制型地貌为隐蔽油气藏提供了有利背景。结合古生物、微量元素、测录井、岩芯、地震等资料综合分析认为,始新统平湖组早期古沟谷内发育多期低位域扇三角洲沉积,自下而上扇体逐步将基底填平补齐,可作为有利的储集相带。随着海平面上升,扇三角洲之上发育海侵潮坪沉积,以稳定泥岩为主,形成一套良好的储盖组合。且平西地区地貌相对高,位于流体运移的有利指向区,扇三角洲低部位油源断裂发育,油气供给充足。古岸线之上扇三角洲根部为近源沉积,分选差、泥质填隙物含量高、压实作用强,与扇三角洲前缘存在明显物性差异,可以形成良好的封堵条件。“沟-扇-断”耦合背景下利于扇体型隐蔽油气藏的发育,对平湖油气田的可持续发展具有重要的现实意义。     

Morphodynamics of the barrier-inlet system, west-central Florida

The barrier-inlet system along the Gulf Coast of peninsular Florida has one of the most diverse morphologies of any barrier system in the world. The delicate balance between tidal- and wave-generated processes on this low-energy coast permits only slight changes in either of these processes to result in significant and rapidly developing morphologic responses. Some of these responses are the result of natural phenomena such as hurricanes opening tidal inlets, closure of inlets due to longshore transport of sediment, and changes in the availability of sediment. Tidal prism is the primary factor in controlling inlet morphology and is greatly influenced by anthropogenic activities in the backbarrier area. Human activity has also modified the coast in many ways over the past several decades, beginning with the construction of the first causeways in the 1920s. The various modifications by development have resulted in important morphodynamic changes in the barrier-inlet system. These include hardening the coast on the beach and at inlets, dredging and filling in backbarrier environments, and construction of fill-type causeways connecting the islands to the mainland. Construction of seawalls and jetties has inhibited normal coastal processes. Examples include the downdrift erosion at Blind Pass and Big Sarasota Pass. Construction of fill-type causeways between the barriers and the mainland has created artificial tidal divides that reduce the tidal prism at some inlets, thereby resulting in instability or closure such as Blind Pass and Dunedin Pass. This is further exacerbated by dredge and fill construction that reduces tidal prism by reducing the area of open water in the backbarrier. Dredging of the Intracoastal Waterway also results in a negative impact on selected inlets by channeling tidal flux away from some inlets. Impacts of these changes inhibit the barrier/inlet environments from responding to open coast processes.     

水下扇储层沉积微相建模--以濮城油田沙三中亚段油藏为例

储层沉积微相是影响储层非均质性的重要因素之一,准确预测储层沉积微相分布对认识储层非均质性、提高油田油气采收率具有重要意义.储层随机建模方法具有很强的地质适用性,合理选择随机建模方法能够有效提高模型精度.以东濮凹陷濮城油田沙三中亚段6-10水下扇油藏为例,由于水下扇沉积储层微相具有几何构型及空间分布复杂的特点,选择序贯指示建模可以对不同微相采用不同变差函数来表征其空间分布结构特征,从而再现储层微相复杂的空间分布.通过定义沟道吻合程度参数Mat对模拟实现进行检验,抽稀井沟道吻合程度参数Mat平均值达到84.7%,表明建模结果具有较高的准确度.序贯指示建模适合于建立水下扇储层沉积微相模型.     

湿地扇扇中辫状水道沉积微相-岩石相划分方法

综合应用岩心、测井、分析化验等资料,对湿地扇扇中辫状水道粗碎屑沉积特征进行了详细研究,提出了沉积微相-岩石相的划分方法。根据不同岩石相的物性、电性及含油性特征,将扇中辫状水道微相细分为辫状水道砂砾岩相、辫状水道粗砂岩相和辫状水道细砂岩相。研究结果表明,沉积微相-岩石相对油水分布具有明显的控制作用,其中以辫状水道砂砾岩相单井日产油能力最高,辫状水道粗砂岩相次之,辫状水道细砂岩相最低,比较符合油田的开发实际。辫状水道粗砂岩相因物性最好,剩余油丰度高,可作为下一步挖潜的主要目标。     

Sedimentology,stratigraphy and architecture of the Nicobar Fan (Bengal–Nicobar Fan System), Indian Ocean: Results from International Ocean Discovery Program Expedition 362

Drill sites in the southern Bay of Bengal at 3°N 91°E (International Ocean Discovery Program Expedition 362) have sampled for the first time a complete section of the Nicobar Fan and below to the oceanic crust. This generally overlooked part of the Bengal–Nicobar Fan System may provide new insights into uplift and denudation rates of the Himalayas and Tibetan Plateau. The Nicobar Fan comprises sediment gravity-flow deposits, mostly turbidites, that alternate with hemipelagite drapes and pelagite intervals of varying thicknesses. The decimetre-thick to metre-thick oldest pre-fan sediments (limestones/chalks) dated at 69 Ma are overlain by volcanic material and slowly accumulated pelagites (0.5 g cm⁻² kyr⁻¹). At Expedition 362 Site U1480, terrigenous input began in the early Miocene at ca 22.5 Ma as muds, overlain by very thin-bedded and thin-bedded muddy turbidites at ca 19.5 Ma. From 9.5 Ma, sand content and sediment supply sharply increase (from 1–5 to 10–50 g cm⁻² kyr⁻¹). Despite the abundant normal faulting in the Nicobar Fan compared with the Bengal Fan, it offers a better-preserved and more homogeneous sedimentary record with fewer unconformities. The persistent connection between the two fans ceased at 0.28 Ma when the Nicobar Fan became inactive. The Nicobar Fan is a major sink for Himalaya-derived material. This study presents integrated results of International Ocean Discovery Program Expedition 362 with older Deep Sea Drilling Project/Ocean Drilling Program/International Ocean Discovery Program sites that show that the Bengal–Nicobar Fan System experienced successive large-scale avulsion processes that switched sediment supply between the Bengal Fan (middle Miocene and late Pleistocene) and the Nicobar Fan (late Miocene to early Pleistocene). A quantitative analysis of the submarine channels of the Nicobar Fan is also presented, including their stratigraphic frequency, showing that channel size/area and abundance peaked at ca 2 to 3 Ma, but with a distinct low at 3 to 7 Ma: the intervening stratigraphic [sub]unit was a time of reduced sediment accumulation rates.     

东营凹陷北部陡坡带稠油地球化学特征与成因

对东营凹陷北部陡坡带郑家—王庄地区稠油与相对稀油烃类组成进行了定性与定量分析。发现多数原油遭受不同程度的破坏 ,饱和烃、芳烃馏分呈有序缺失 ,于多数原油中检测到生物降解标志物 2 5 -降藿烷系列。地质与地球化学综合研究认为 ,以生物降解—氧化及相关的生化 /化学作用、以水洗—重力分异—轻质组分逸散为主的物理作用是郑家—王庄原油稠化的重要机理 ;东营凹陷北部“有限后退型”盆地边界发育的风化壳潜山、砂砾岩扇体储层孔渗条件好、油藏埋深浅、盖层条件差和不整合面等通道与外界的连通是郑家—王庄及邻区重质油形成的根本原因。提出生物标志物绝对定量可作为识别原油遭受次生改造作用程度、判断不同类型生物标志物抵抗降解能力大小的有效指标。利用生物标志物 ,发现郑家—王庄局部地区原油具有不同降解级别原油相混的混合现象 ,可能反映两次或多次充注。郑家—王庄及其邻区有望获得相对稀油新增储量。     

近岸水下扇微相划分研究及意义初探——以滦平盆地下白垩统西瓜园组为例

滦平盆地下白垩统西瓜园组沉积期发育大量的粗碎屑岩沉积,通过野外实地考察以及结合无人机摄影技术,将流体搬运机制与微相划分相结合,对断陷湖盆内部粗碎屑沉积体进行详细研究。结果表明:滦平盆地西瓜园组沉积期北部受边界断层活动影响,发育典型陆相断陷湖盆的近岸水下扇沉积体系。根据露头观测及研究,可划分出扇根、扇中及扇端三种亚相。其中扇根亚相以碎屑物质直接入湖、岩性较粗、分选极差、无磨圆为特征。扇中亚相采用"水下河道微相"及"边缘微相"的划分方式,水下河道微相可见同时发育由碎屑流及浊流两种不同流体性质控制的沉积体,沉积迅速,界限清晰且含轻微冲刷,横向连续性较为稳定,砾石出现一定定向性,磨圆较差,在扇中亚相中最为发育;边缘微相沉积相对较为混杂,漂砾较为常见,可见明显的板状交错层理,横向连续性差,指示河道的改道或者边缘沉积,不发育冲刷-充填构造。扇端亚相以砂泥岩薄互层或者厚层细砂岩为特征,可见细小砾石层。微相划分方法结合流体搬运机制及沉降方式,更加具有成因性依据,同时更好地解释了远离物源区的稳定砾石层发育。研究结果为近岸水下扇内部砂体发育规律和叠置关系研究及下一步油气勘探与开发提供了新思路。