近年来珠江口盆地古近系深层勘探屡获突破,经济下限也逐渐下调至埋深4000多米,勘探实践证明,陆丰-惠州地区古近系储层表现出明显的差异性,陆丰地区古近系储层普遍优于惠州地区.为解析这两个地区古近系储层的差异,本文利用岩石薄片、扫描电镜、X衍射、物性等分析化验资料,开展了陆丰、惠州地区古近系储层研究,根据成岩过程中岩石的溶蚀特征及溶蚀产物对其进行分类,建立其与储层物性之间的对应关系,进而还原不同类型储层的孔隙演化过程及控制因素.研究结果显示,陆丰地区文昌组储层受中生代沉积岩物源影响明显,岩石组分具高石英、低长石组分特征,孔隙类型以原生孔为主,具有弱溶蚀-少产物的成岩组合,发育低孔中渗或中高孔中高渗储层;惠州地区文昌组受中生代花岗岩物源影响明显,岩石组分具低石英、高长石组分特征,孔隙类型以原生孔、溶蚀孔和高岭石晶间微孔等混合孔为主,具有强溶蚀-多产物的成岩组合,普遍发育中孔低渗储层,但受强水动力改造下也能形成中孔中渗优质储层.对陆丰与惠州地区古近系优质储层的对比分析认为,母岩性质决定储层的先天优势,沉积改造改善储层初始物性,成岩差异影响储层质量的好坏.厘清不同母岩影响下优质储层发育条件及形成机理,对不同地区古近系储层甜点预测意义重大.

Hundreds of millions of tons of oil and gas geological reserves have been discovered through exploration in the deep-water area of the northern continental margin of the South China Sea, and the distribution of large-scale effective reservoirs during the Paleogene rifting period is the key for continuous discovery in deep-water zone. Large braided fluvio-delta can be observed on seismic data from the Wenchang to Enping formations in the rifting period of the flexural gentle slope belt in the deep-water zone. Due to the absence of wells or few wells, for further understanding of the composition and evolution of large braided fluvio-deltaic sedimentary units in the process of tectonic subsidence in this region, a simulation experiment on the response of the deltaic sedimentation process in the flexural gentle slope zone to flume was carried out. Three phases of tectonic subsidence were designed for the simulation experiment, corresponding to the three phases of Paleogene regional tectonic-sedimentary evolution including balanced rifting period, detached rifting period, and faulted depression rifting period. The hydrodynamic mechanism of tractive flow was simulated by means of flood, flat water, and dry water. Simulation results showed that during the three stages of tectonic subsidence, the flexural gentle slope zone deve-loped distributary channels, natural dikes, floodplains, underwater distributary channels, estuaries, inter-tributary bays and other delta sedimentary microfacies units. The braided river delta was dominated by lateral proliferation, supplemented by vertical accretion, and the sedimentary center gradually migrated to the center of the depression, with almost no degeneration. The delta shape and sand body distribution in the flexural gentle slope zone during the rifting period were mainly controlled by factors such as structural geomorphology, river discharge amount into lake, lake level changes, and water depth.

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 sedimentary and filling characteristics of Paleogene in the Xingning depression are studied in order to provide geological basis for the hydrocarbon exploration in the modern ultra deepwater area.On the basis of systematic analysis of seismic sequence stratigraphy and seismic facies,combined with the previous research results in adjacent area,it is showed that unconformity contact occurs among the Paleogene Wenchang Formation,Enping Formation and Zhuhai Formation in the Xingning depression and a total of 12 Ⅲ-sequences are recognized in the Paleogene.Terrestrial lacustrine deposition occurs in the Wenchang and Enping Formation,with delta deposition on gentle slope zone,shore to shallow lake on gentle slope shallow water zone,fan delta on steep slope zone and semideep-deep lake on depression center.Shallow delta deposition occurs in Zhuhai Formation.The overall process of transgressive sedimentary forms the space-time combination of the lacustrine mudstone source rocks in Enping Formation and sandstone reservoir in Wenchang Formation and Zhuhai Formation,a favorable oil and gas exploration potential in the study area.

珠江组是珠江口盆地东部地区的主要产层，L H 3井23．8～18．5 M a的下珠江组的取心段，包括浅海陆源碎屑岩，碳酸盐以及碎屑岩碳酸盐混积岩，呈现一套硬石膏褐铁矿高岭石白云石的矿物序列，且这套矿物序列在该井附近的同时代地层中也有发育，但完整程度有别。通过对这些矿物物质来源、形成原因以及形成时间的探讨，认为它们形成于沉积时期或者同生成岩阶段或准同生沉积期，均反映了氧化甚至暴露的沉积环境。同时也能提供气候的湿度方面信息，硬石膏以及白云石的发育反映气候干旱，而褐铁矿以及高岭石发育段反映了气候较潮湿。综合孢粉、同位素资料分析认为，取心段在珠江组下段沉积期的气候经历了炎热干旱温暖潮湿炎热干旱的变化过程。

Zhujiang Formation is the provincial reservoir in Pearl River Mouth basin, and the cored section of Lower Zhujiang Formation (deposited from 23.8 to 18.5 Ma) of well LH-3 in eastern basin, consisting of terriclastic and carbonate rocks as well as mixed terriclastic-carbonate rocks, demonstrates a mineral series of anhydrite-limonite-kaolinite-dolomite from bottom to top, which also exist in adjacent wells, while the abundances are different. After the analysis of the material sources, formatting time and geological mechanism of these minerals, the authors draw the conclusion that all of the minerals formed in depositional of syndiagenetic or pene-contemporaneous stage, which reflects oxidized or even exposed environments during their formation. Furthermore, the mineral association can provide humidity information, as anhydrite and dolomite reflect the arid climate, while limonite and kaolinite indicate humid climate. After the integration of sponge and pollen data, carbon-oxygen isotopic data from neighbor wells, the authors know that the climate during the Lower Zhujiang Formation deposition have changed from arid and hot to humid and warm, then back to arid and hot again.

Huizhou is an area with the highest exploration maturity in Pearl River Mouth Basin,wherein the Zhujiang Formation is the primary oil-producing layer and has the potential of finding stratigraphic-lithologic traps.Through analyses on the factors controlling sandbody distribution of the Zhujiang Formation in Huizhou area,this paper concludes that various factors including palaeogeomorphology,sequence stratigraphy,delta-dominated sedimentary facies distribution and hydrodynamics in transitional zone during basin transformation and subsequent tectonic movements all have important influences on the formation and distribution of sandstones.Sedimentary facies determines the macroscopic distribution of sandbodies,and sequence structure influences the lateral and vertical sandbody development and sandbody stacking patterns in different system tracts.Sedimentary facies and sequence structure are the two main controlling factors.Based on the study of the controlling factors and the discovered lithologic hydrocarbon reservoirs,this paper establishes development models of stratigraphic-lithologic traps of Zhujiang Formation in Huizhou area,and analyzes the favorable area and types of stratigraphic-lithologic traps.We believe that the lithologic pinchout traps around sedimentary slope-break and / or within transgressive system tracts are the best ones for hydrocarbon accumulation.

The Pearl River Mouth basin transformed to a kind of quasi-passive continental margin basin from a continental rifted lake basin after Nanhai movement,and then a set of continental-oceanic transitional facies formations and marine formations which are now the main oil-production formation formed in Pearl River Mouth basin.The analysis on controlling factors of these sets of formations is useful to the third-order sequence stratigraphy division and correlation,and helpful to understand the type and structure of each sequence.Based on the analysis of marine sequence type and developing models of Zhuhai Formation to Yuehai Formation,the controlling factors of marine sequence stratigraphy evolution in Pearl River Mouth Basin are analyzed according to its configuration.It is considered that the tectonic movement,paleogeographic framework,relative sea-level change and sediment supply are the main controlling factors of marine sequence stratigraphy evolution.But these four factors have different effects at different times.The tectonic movement and paleogeographic framework play an important role to the development of sequence stratigraphy from late Oligocene to early Miocene when the basin framework made a great adjustment.Three important movements happened during the period of marine formation forming: the Nanhai movement and the Baiyun movement made the basin framework changed,and controlled the early depositional filling in the basin;The Dongsha movement made parts of basin serious uplift and denudation.These three movements all formed regional unconformities which make up of the second-order sequence boundaries.The influence of paleogeographic framework on the sequence stratigraphy happened in the early period of marine sequence forming,which include the influence of palaeouplift topography,depression topography during the fault-depression stage and shelf breaks.During the peaceful period without tectonic movement,relative sea-level change and sediment supply become the main controlling factors.There is relative wide and smooth continental shelf in Pearl River Mouth Basin,and different types of sequence formed due to the degree of relative sea level fall.When there is a significantly large fall in sea level,reaching to shelf break,a type 1 unconformity develops,such as sequence boundary SB21、SB13.8 and SB10.5 in Pearl River Mouth Basin.When the sea level falling is of lesser magnitude,not reaching to shelf break,a type 2 unconformity develops,such as sequence boundary SB11.7,SB8.5 and SB6.3.In the early period of marine sequence forming,there are three kinds of sediment supply which are Paleo-Pearl River delta,Hanjiang delta and Dongsha uplift;but from late stage of Zhujiang Formation,the sediment supply of Paleo-pearl River delta become the main resources.Whereas the influence area of Paleo-Pearl River delta and other sediment supplies made the same sequence present different characters at different places.

Huizhou depression is one of the most prolific hydrocarbon areas in Pearl River Mouth basin.Plentiful Neogene oil and gas have been found,but no breakthrough has been made in Paleogene sediments.Reservoir porosity and permeability are thought very low in Paleogene,and this inhibits the exploration progress.As to the deep reservoir,the factor of porosity is in connection with petrographic composition and architecture.The skeleton components and matrix components of the sandstone are basic substances participating in diagenesis.Feldspar sandstone,feldspathic quartz sandstone and lithic arkose are main rock types in Zhuhai and Enping Formations,which are characterized by coarse grains,poor grading,subangularity,low compositional maturity,and moderate to bad textural maturity.The storage capability is considerably impacted by diagenesis and porosity evolution.Based on slices observation and cores analysis and using such means as scanning electron microscope(SEM),X-diffraction,cathodoluminescence and organic acid test,the authors studied diagenesis and porosity evolution.The results show that the sandstone porosity is decreased mainly by compaction and cementation and subordinately by quartz overgrowth and authigenic mineral filling.Abundant secondary pores are produced by the denudation of such unstable components as feldspar,matrix and cuttings,and this leads to the increase of the percentage of voids.Researches reveal that the deep reservoir has experienced four diagenesis evolution phases,i.e.,syngenetic stage,eogenetic stage(composed of A-stage and B-stage),anadiagenetic stage(comprizing A-stage& B-stage)and late diagenetic stage.Well data show that most of the reservoirs have attained the eogenetic stage,whereas segmental sandstone(under 4 000 m)has entered into the late diagenetic stage.Primary porosity was decreased quickly by compaction at the eogenetic stage(A→B)because of the increasing overlying load.Linear contact occurred at the B-eogenetic stage.Hydrothermal fluid of organic acid was discharged to fastigium with most kerogen being transformed into hydrocarbon at the anadiagenetic stage(A→B).Due to increasing acidity,the unstable components of aluminosilicate framework ingredients such as feldspar,matrix and cuttings were dissolved,so a lot of secondary pores were generated,and the physical property of reservoir was improved.At the late diagenetic stage,organic material was changed from mature to highly mature,organic acid concentration was decreased to the lowest and destroyed by thermal activity,stratigraphic water was gradually turned into alkaline,authigenic minerals were developed generally,and the reservoir physical property was changed to bad by the cementation of anhydrite.Just because lots of secondary pores were generated at the eogenetic stage,it improved the physical property and increased the potential of deep reservoir exploration.

The Paleogene strata are constituted of Wenchang,Enping and Zhuhai Formations in Huizhou Depression.Deep reservoirs are in Enping and Zhuhai Formations.The reservoirs mainly consist of secondary porosity such as intergranular and intragranular dissolved pores,and clay mineral micropores as well as residual primary intergranular pores and fissures,among which the average primary porosity is 2.4%(accounting for 22.2% of the total porosity),the average secondary porosity is 5.6%(65.2% of the total) and the average fissure porosity is 1.0%(12.5% of the total).Development of secondary porosity improved the reservoir capacity of deep sandstone due to dissolution of organic acid to skeleton grains and matrix in sandstone.The secondary porosity developed well in a depth range of 3500～4200m where reservoir property is good but the secondary porosity is obviously decreased in the depth of 4200～4500m due to the late recementation and compaction.argin but TypeⅡand TypeⅢ in the Northwest Shelf of Australia,Mid-Norway continental shelf and South Sea.

The Neogene in Huizhou Depression were deposited in neritic shelf environment and is gentle in dip.However,a comprehensive study of seismic,drilling,log data indicates that three types of slope-breaks (i.e.deposition breaks,fault breaks and flexural breaks) occur in the area.On the plane,these breaks combine with one another in four patterns,including multistage,diagonal,comb-shaped,and ridge-parallel.Their evolution presents such evident features as inheritance,periodicity,scale grading,and migration cyclicity.Slope-breaks in the north margin and south of the basin control the superimposing pattern of the sequences and the development and spatial distribution of depositional systems.

The regional geological background has indicated that Miocene stratigraphic and lithologic traps may be created in Huizhou area.Studies on creation conditions,controlling factors and distribution pattern of the stratigraphic and lithologic traps are very important to continuous oil and gas exploration in the area.Based on establishing Miocene sequence stratigraphy framework with high resolution in Huizhou area,the configuration is analyzed for various sequences,and the formation mechanism,distribution and control on sedimentary system are researched for various types of slope-break zone.The sequence boundaries and the slope-break zones are the important factors to control creation of stratigraphic and lithologic traps in the area.There are three types of stratigraphic and lithologic traps with exploration potential,and the HZ 27-3 lowstand system tract has been drilled successfully.