为了弄清珠江口盆地西江主洼南部缓坡转换带文昌组和恩平组地层的沉积样式及其发育规律,通过钻井、测井、地震、岩芯和分析化验等资料,从岩性、层理构造、结构特征及地球物理特征等方面总结两种缓坡转换带沉积体系的特征,并剖析研究区断裂特征.研究认为,文昌期(T80-Tg)主要发育NE和NW向控洼大断裂,分布于盆地边缘,断裂组合形态以平行状、阶梯状及斜交状为主;恩平期(T70-T80)主要发育NE向、EW向和SE向断裂,分布于盆地中央,断裂组合形态以同向、反向及斜交状为主;虽然同属缓坡带,但文昌组地形较恩平组陡,湖盆较深,发育辫状河三角洲;恩平组地形宽缓,发育浅水三角洲,湖盆中央断裂的活动及季节性洪水的发生,使得浅水三角洲水下分支河道极为发育.两种不同类型的三角洲具有不同的岩性组合特征:文昌组辫状河三角洲砂岩粒度粗且厚,泥岩层薄,恩平组浅水三角洲砂岩粒度粗且薄,泥岩层厚,含煤,均为有利油气勘探区域.

新近系中新统珠江组下段是珠江口盆地东沙隆起主要的油气勘探层段之一,且广泛发育混合沉积,前人主要以陆源碎屑沉积体系开展相关研究.依据录井、岩心和薄片鉴定等资料,同时结合区域油气地质背景,对混合沉积特征、成因、主控因素等进行了系统研究,详细阐述了研究区早中新世的混合沉积格局及成因模式.研究区主要发育混积潮坪相,混合沉积在微观上表现为陆源碎屑与碳酸盐组分上的混积岩,宏观上表现为混积岩、陆源碎屑岩和碳酸盐岩互层的混积层序.混积机理与海平面、物源和水动力条件等的频繁变化密切相关,混积方式以原地混合和相混合为主,见风暴成因的间断混合.通过混合沉积特征、控制因素、成藏潜力等研究,为研究区下一步油气勘探提供了支持.

大型海相三角洲分布范围广,沉积动力复杂,其精细层序—沉积构型和演化规律是沉积学领域长期研究的热点.综合岩矿、测井和三维地震资料,充分结合高精度层序地层学和三维地震沉积学分析方法,对古珠江三角洲西侧的恩平地区中新世早-中期沉积特征进行了精细研究,识别出了辫状河道、曲流河道等河控三角洲的主要微相单元,同时也揭示出海岸砂脊等浪控三角洲中发育的典型微相类型.在高精度层序格架约束下,揭示出单一典型层序内古珠江三角洲的演化特征:低位体系域以河控三角洲为主,发育大型交切状辫状水道;海侵和高位体系域河道规模明显减小,以小规模曲流河道为主,且易于见到海岸砂脊等波浪作用的典型特征.此外,针对恩平地区中新世早-中期沉积相带的系统编图和演化分析,在大约6Ma时间内识别出6次河道大规模改道现象,推测恩平地区沉积演化明显受到自旋回沉积过程的影响.

新近系韩江组是珠江口盆地恩平凹陷的油气主要储集层段,随着勘探程度的提高,寻找岩性油气藏是未来油气勘探的重要方向.为了系统地研究该地区岩性圈闭的发育类型,在"沉积层序"理论模型的指导下,划分出高位体系域、海侵体系域及低位体系域,并通过井震结合、岩芯观察,结合RGB属性融合技术增强关键沉积单元的刻画,开展了精细的沉积微相研究,共识别出辫状河道、串沟河道、曲流河道、河口坝、海岸砂脊和远砂坝6种沉积微相类型.在微相砂体刻画的基础上,结合构造特征,总结了该地区发育的构造-岩性圈闭、多砂体类型岩性圈闭以及上倾尖灭型岩性圈闭三大岩性圈闭类型,其中凹陷中部、西南部以河道砂为储层的构造-岩性圈闭为最具勘探潜力的目标类型.

运用放射性元素寻找油气是一种非常规油气勘探手段.近年来,在珠江口盆地珠一坳陷富烃凹陷周边古近系钻遇高自然伽马(GR)砂岩,其GR值(100～300 API)甚至大于同区泥岩的GR值(100～200 API).为了弄清该特殊现象背后的地质意义,对珠江口盆地珠一坳陷古近系高自然伽马砂岩开展了铀(U)、钍(Th)、钾(K)等3种元素含量与GR值的相关趋势线分析,从井震特征、岩性特征及矿物成分特征等入手分析了砂岩GR值增高的主要原因及成因机制,探讨了放射性元素聚集的条件、运移通道、驱动力以及油气意义.结果表明:西江、惠州地区由U含量增高导致砂岩GR值偏高,恩平、番禺地区由K,Th含量增高导致砂岩GR值偏高;砂岩GR值增高有两大成因机制,一是地下流体带来的放射性元素离子U4+在氧化-还原面处富集后导致地层GR值偏高,这种特殊现象说明在具有连通基底大断裂旁的圈闭中,U4+的富集指示了曾经油气的存在,证实了研究区油气运移通道的有效性,对于油气藏的预测有着非常重要的指导性意义,二是地表流体带来的含放射性元素的矿物大量沉积后导致地层GR值偏高,含放射性元素矿物性质不稳定,可指示近源供给的存在,对于判断物源及沉积环境有着非常重要的意义.该研究成果为预测研究区油气成藏有利区带提供了依据.

During the Miocene, when the Zhujiang Formation was deposited, the eastern part of the Pearl River Mouth Basin, northern South China Sea, underwent intense mixed siliciclastic and carbonate sedimentation, particularly on the platform of the marginal ramp of the Dongsha Rise, northeastern margin of the South China Sea. Cores and well logs from industrial boreholes were collected and systematically investigated to reveal the sedimentary-petrographic characteristics of the mixed deposits and their formative processes. Four lithotypes were differentiated in the deposits, that is, (1) sandstone, (2) dolomitic sandstone and calcitic sandstone, (3) sandy dolomite and sandy limestone, and (4) dolomite, bioclastic limestone, and micrite limestone, which were formed by three major types of mixing processes: punctuated, facies, and in situ mixing processes. The porosity and permeability of the mixed deposits indicated that the siliciclastic component of the mixed deposits that experienced punctuated mixing formed the most high-quality hydrocarbon reservoirs. Exploration revealed that the lithologic reserves in the study area were mainly developed in mixed sedimentation areas. Our results suggest that the mixed sedimentation area, particularly with pure sandstone sedimentation or bioclastic sandstone, that underwent compaction or structural fracture activities, may be the next preference for lithologic exploration.

珠江口盆地惠陆地区至东沙隆起一带珠江组时期位于陆架坡折之上,在持续海侵的背景下,发育了碎屑岩及碳酸盐岩两大岩性,为了厘清不同岩性之间的层序对应关系,利用岩性组合、生物组合、暴露标志以及地震反射特征,确定了海平面升降是控制层序样式的主要因素,识别出6个三级层序界面(SB23.03、SB21.00、SB18.00、SB17.25、SB17.10、SB15.97)及1个全区最大海泛面(MFS19.10),建立了碳酸盐岩—碎屑岩共生区的等时地层格架.在层序对比基础上建立了碳酸盐岩 碎屑岩共生区层序发育模式:海平面上升时期,主要发育退积式三角洲与向高部位退缩的碳酸盐岩地层;海平面下降时期,主要发育进积式三角洲与向侧面扩张的碳酸盐岩地层.

The seismic signal shooting-receiving conditions are poor in Zhunggar Basin of Shinan Oilfield,therefore resulting in poor data quality due to the desert on the ground of the area and the delicate description of oil sand bodies is difficult due to the small thickness of oil sand bodies and complex lateral variation.In order to clarify the spatial distribution of the oil sand bodies,by using the principle and methods of seismic sedimentology and seismic-well combination,the delicate sequence stratigraphy framework is established,the shape of the sand bodies,scale and pinch-out position of Touhetun Formation are determined and the relationship between the sedimentary micro-facies of the delta and the geometry shape of the sand bodies are determined.Based on the spatial superposition mode of the sand bodies the geology concept model is established,setting up a good foundation for future exploration and development of the oil field.

The characteristics of sequence of the L Formation of Paleogene age in deepwater area in A Basin in the South China Sea were studied in reference to the classical sequence stratigraphic theory of Vail and seismic and logging data.It was showed that this method could solve the problems of poor quality seismic data,lack of well logging data,complication by tectonic faulting,and fragmentation of stratigraphic sequence.In this method,well-logging and seismic data were used,five sequence boundary of SB0,SB1,SB2,SB3 and SB4 were identified,and four third order sequences of SⅠ,SⅡ,SⅢ and SⅣ were established respectively.Deltas and fan deltas developed in HST,incised valley,slope fan,basin floor fan,turbidite fan developed in LST and beach bar developed in TST were favorable positions for the development of oil-gas pool.Widely distributed mudstone of marine facies was favorable source rock.All kinds of sands and source rock could develop two kinds of accumulation models of graben and horst,forming lots of blind strtigraphic traps.