南海北部琼东南盆地深水区陵水凹陷南部油气成藏条件

勘探已证实陵水凹陷浅层新近系发育中央峡谷莺歌海组—黄流组有效天然气成藏组合。渐新统崖城组煤系是陵水凹陷的主力气源岩,也可为陵水凹陷南部提供烃源。渐新统上部陵水组一段—中新统下部三亚组二段发育扇三角洲、浊积水道、海底扇砂岩储层,砂体富集的主控因素是凹陷边界断裂转换带、断阶带及构造坡折。陵水凹陷南部具有晚期成藏的特点,陵水凹陷生成的烃类通过断裂、砂体向南侧发生垂向与侧向运聚。综合储层、运移及圈闭条件等因素,优选出陵南斜坡反向断阶构造带为有利勘探区带。     

深水重要油气储层--琼东南盆地中央峡谷体系

南海北部海域琼东南盆地发育一个大型中央峡谷体系,平面上呈“S”型NE向展布,西起莺歌海盆地中央拗陷带东缘,横穿琼东南盆地中央拗陷带,向东延伸进入西沙海槽。通过2D及3D地震资料的精细解释和钻井资料综合分析,研究揭示该峡谷体系可以划分为4个区段,不同区段不仅具有明显不同的剖面形态,而且具有不同沉积物构成、沉积微相以及不同沉积物源。不同区域峡谷形态及充填分析表明,自西向东,中央峡谷下切深度越来越大,下切层位越来越老。其下切剖面形态发育有“V”、“U”、“W”和复合型。其中“V”型峡谷下切深度最大,冲刷、削截特征最明显。峡谷西段以浊积水道沉积为主,峡谷东段为浊积水道与块体流沉积互层沉积,但在不同区带不同沉积物所占比例有一定差异。浊积水道沉积的物源主要来自于盆地西侧,块体流沉积的物源主要来自于盆地北部陆坡体系,从而,来自于西部浊积水道沉积与来自于北部块体流沉积在中央峡谷内形成了多源多期发育的复杂的峡谷系统。     

虚拟井技术在琼东南深水区储层预测中的应用

琼东南盆地深水区钻井少,影响了储层预测的准确度。为了解决这个问题,采用虚拟井技术对琼东南盆地深水区陵水凹陷南部已证实的A?1含气构造进行储层预测,验证了该方法的合理性;并总结出了A研究区内储层发育区的波阻抗经验值,据此预测相邻待钻A?2构造的储层厚度。 A?2构造的预测结果与实钻结果相吻合,证实了虚拟井技术在琼东南盆地深水区勘探目标储层预测方面具有较高的可行性。     

琼东南盆地深水区中央峡谷天然气成藏条件与成藏模式

利用钻井岩芯、岩屑地质化验资料及测井、二维、二维地震数据,综合分析了琼东南盆地深水区中央峡谷储层的发育特征、天然气成藏条件及成藏主控因素.结果表明,峡谷中、下部堆积的多期浊积砂岩,储集物性好,是该区带的优质储层;峡谷内发育的大量岩性、构造-岩性复合型圈闭为天然气聚集造就了重要场所;凹陷中的渐新统崖城组煤系烃源岩及广厚的半封闭浅海泥岩生气潜力大,提供了丰富的烃源基础;峡谷下方的底辟/微裂隙是深部崖城组烃源岩生成的天然气向上运移的重要通道.可见,中央峡谷成藏条件优越,圈闭有效性和运移是该区天然气成藏的关键要素;由于峡谷内圈闭大多数定型于上新世莺歌海组沉积时期,与下伏崖城组烃源岩主生气期形成合理配置,因此,天然气成藏较晚,L1、L2和L3气田的重大发现就是很好的例证.     

琼东南盆地深水区新生代海底扇沉积演化——以宝南断阶带为例

琼东南盆地深水区是油气勘探的重要领域,大型储集体的发育条件及预测研究对该领域下一步的勘探至关重要。以钻井、测井、高精度三维地震等资料为基础,应用井震精细标定、骨架砂体雕刻和高精度三维地貌叠合等技术手段,对琼东南盆地深水区宝南断阶带的物源方向和海底扇展布规律进行了精细研究。结果表明:①宝南断阶带的主物源来自南部隆起;②研究区内主要发育永乐C-1和永乐D-1两个大型海底扇,扇体纵向上多期叠置,扇体内部沟通下伏烃源岩的断裂发育,成藏条件优越,具有重要的勘探意义。     

琼东南盆地深水区中央峡谷沉积微相特征

中央峡谷位于南海北部琼东南盆地深水区,是琼东南盆地深水区油气勘探的重点区域。迄今为止,对于峡谷的成因及沉积微相的认识,不同学者有不同的观点。近来,峡谷内又新增了多口钻井,系统的分析总结峡谷的充填期次、沉积微相的划分及骨架砂体的展布意义重大,将直接影响到峡谷下一步的勘探部署。因此,本文以钻井资料为基础,通过岩矿特征、粒度分析、沉积构造、古生物特征、测井相等的分析,再结合高分辨率三维地震资料,综合分析了地震剖面、均方根振幅属性、多种切片技术等地震相特征,根据从点到面的研究思路对黄流组时期（S₄₀～S₃₀）中央峡谷发育的沉积微相进行了精细研究,研究表明琼东南盆地中央峡谷为大型侵蚀型水道,具有曲流水道特征,类似陆上曲流河沉积,发育点砂坝、天然堤复合体、泥质水道等沉积微相;综合构造背景、古地貌及古地貌与平面沉积相叠合图的研究表明,点砂坝主要发育于峡谷古地形的弯曲处,系水道不断迁移摆动而形成的侧向加积体,地震剖面上表现为强振幅叠瓦状前积型特征,岩性为块状细砂岩夹薄层泥岩,测井曲线GR呈中-高幅箱形夹薄层低幅齿形,为正旋回沉积特征。点砂坝规模不等,面积约8~20.5 km2;天然堤复合体范围较窄,这可能受峡谷壁的限制作用影响。已钻井也证实,点砂坝作为峡谷水道的骨架砂体,储层物性好,具有良好的勘探前景。     

生物礁、生物丘及滩相沉积的地震特征对比与识别——以琼东南盆地深水区储层预测为例

在深水无井碳酸盐岩发育区开展储层预测,单纯以丘状地震反射作为识别生物礁的依据容易把不具有储层意义的生物丘误判为生物礁,同时也会忽略具有储层意义但不具有丘状反射特征的滩相沉积。对生物礁、生物丘及滩相沉积这三类地质体从地震反射特征和地震速度特征两方面进行了分析对比,它们相互之间既有联系又有区别:生物礁为高速反射,同时具有丘状反射外形;生物丘具有丘状反射外形但为低速反射;滩相沉积为高速反射,但无丘状反射外形。由此建立了新的深水区礁滩储层预测方法,并对琼东南盆地一深水研究区中新统梅山组碳酸盐岩储层进行了重新预测,把原来预测的相当大的一部分"生物礁"划分为生物丘,同时还新发现了面积几可与生物礁相当的滩相沉积。本文所用方法对深水区碳酸盐岩储层的预测更为精确。     

琼东南盆地深水区油气成藏条件分析与勘探方向选择

深水区油气资源丰富,已成为油气储量增长的重要领域.琼东南盆地深水区具有与世界典型深水领域油气产出相似的构造和沉积背景,发育三套优质烃源岩、四类有利储层,同时圈闭类型多样,油气运聚条件良好,具备发育大型油气田的条件,油气潜力巨大.其中,陵水凹陷南斜坡是近期内最可行的勘探区域.     

南海北部琼东南盆地第四系陆架边缘轨迹迁移及深水沉积模式

陆架边缘迁移轨迹综合受控于构造、物源、海平面和气候等多种因素,其迁移演化与深水沉积体系发育关系密切。陆架边缘迁移规律及沉积物输送体制与深水砂体预测是当前国际地学领域的热点议题。本文通过基于琼东南盆地新采集的高精度地震资料,定量表征了第四系陆架边缘轨迹,识别了低角度缓慢上升型、中等角度上升型和高角度急剧上升型等3类陆架边缘轨迹类型。2.4 Ma以来,陆架边缘轨迹时空演化可分为3个阶段且具有侧向差异性:2.4~1.9 Ma以低角度缓慢上升型为主,1.9~0.8 Ma西北部以低角度缓慢上升型为主,东北部则以中等角度上升型为主,0.8 Ma至今西北部以中等角度上升型为主,东北部以高角度急剧上升型为主。琼东南盆地第四系陆架边缘迁移轨迹研究表明:当陆架边缘轨迹角0°<α<4°时,陆坡区峡谷规模较小且下切浅,深海平原区发育多期大型海底扇沉积,块体搬运沉积(MTDs)较少;当4°<α<35°时,陆坡区峡谷规模有所增加,深海平原区海底扇沉积与块体搬运沉积均有出现;当35°<α<90°时,陆坡区峡谷发育较少但下切深,深水平原区沉积以大型块体搬运沉积为主,海底扇几乎不发育。琼东南盆地更新世以来气温不断下降,以及东亚冬季风的显著增强,物源供给增强加之海平面的下降进而导致了西北部陆架边缘表现为进积特征;研究区东北部的断裂活动频繁以及物源供给弱,导致了研究区东北部陆坡推进距离远远小于研究区西北部且发育多期次块体搬运沉积物。以上认识对南海北部陆架边缘体系及深水扇预测具有一定的理论意义。     

南海莺歌海盆地黄流组海底扇储层构型特征*

南海莺歌海盆地东方X气田中新统黄流组一段发育浅海海底扇沉积,沉积类型特殊,砂体连通性复杂,对储层构型的研究较为薄弱,影响了该地区的油气勘探和开发。以层序地层学、沉积学、测井地质学、地震沉积学等理论为指导,结合岩心、钻井、测井、三维地震和地震波阻抗反演成果等资料,对东方X气田中新统黄流组一段Ⅱ_b气组海底扇构型单元及砂体分布规律进行研究。结果表明: 研究区海底扇主要发育中扇亚相的水道沉积、堤岸沉积、席状砂和扇缘砂; Ⅱ_b气组以水道沉积及席状砂为主,2期水道沉积以充填沉积作用为主,整体呈NW-SE向展布;储集层内部砂体有层状充填、垂向切叠及侧向切叠3种叠置样式; 储层构型主控因素包括物源供给、地形坡度及重力流能量。     

南海莺歌海盆地黄流组海底扇储层构型特征*

南海莺歌海盆地东方X气田中新统黄流组一段发育浅海海底扇沉积,沉积类型特殊,砂体连通性复杂,对储层构型的研究较为薄弱,影响了该地区的油气勘探和开发。以层序地层学、沉积学、测井地质学、地震沉积学等理论为指导,结合岩心、钻井、测井、三维地震和地震波阻抗反演成果等资料,对东方X气田中新统黄流组一段Ⅱ_b气组海底扇构型单元及砂体分布规律进行研究。结果表明: 研究区海底扇主要发育中扇亚相的水道沉积、堤岸沉积、席状砂和扇缘砂; Ⅱ_b气组以水道沉积及席状砂为主,2期水道沉积以充填沉积作用为主,整体呈NW-SE向展布;储集层内部砂体有层状充填、垂向切叠及侧向切叠3种叠置样式; 储层构型主控因素包括物源供给、地形坡度及重力流能量。     

Gravity Flow on Slope and Abyssal Systems in the Qiongdongnan Basin, Northern South China Sea

The study of new seismic data permits the identification of sediment gravity flows in terms of internal architecture and the distribution on shelf and abyssal setting in the Qiongdongnan Basin (QDNB). Six gravity flow types are recognized: (1) turbidite channels with a truncational basal and concordant overburden relationship along the shelf edge and slope, comprising laterally-shifting and vertically-aggrading channel complexes; (2) slides with a spoon-shaped morphology slip steps on the shelf-break and generated from the deformation of poorly-consolidated and high water content sediments; (3) slumps are limited on the shelf slope, triggered either by an anomalous slope gradient or by fault activity; (4) turbidite sheet complexes (TSC) were ascribed to the basin-floor fan and slope fan origin, occasionally feeding the deep marine deposits by turbidity currents; (5) sediment waves occurring in the lower slope-basin floor, and covering an area of approximately 400?km2, were generated beneath currents flowing across the sea bed; and (6) the central canyon in the deep water area represents an exceptive type of gravity flow composed of an association of debris flow, turbidite channels, and TSC. It presents planar multisegment and vertical multiphase characteristics. Turbidite associated with good petrophysical property in the canyon could be treated as a potential exploration target in the QDNB.     

琼东南盆地中央峡谷深水天然堤—溢岸沉积

中央峡谷位于琼东南盆地深水区,发育面积较广,内部天然堤—溢岸沉积发育。深水天然堤—溢岸可作为良好的油气储集体,深受油气工业界的关注。为了指导中央峡谷的油气勘探,利用三维地震资料,结合地震剖面以及均方根振幅属性对中央峡谷内部天然堤—溢岸沉积的形态和控制因素进行了分析,总结了天然堤—溢岸的沉积模式,并对其油气勘探前景进行了...     

Features of Late Cenozoic Deepwater Sedimentation in Southern Qiongdongnan Basin,Northwestern South China Sea

Based on high resolution 2D and 3D seismic data acquired in recent years,using sequence stratigraphy analysis and geophysical methods,we discuss the features of Late Cenozoic deepwater sedimentation in the southern Qiongdongnan (琼东南) basin.The study area entered a bathyal slope environment in the Miocene.The channel developed in the Sanya (三亚) Formation was controlled by a fault break,and its shingled seismic characteristics represent multiple erosion and fill,which may indicate that turbidite current developed in the slope environment.The polygon faults found in mudstone of the Meishan (梅山) Formation represent the deepwater hungry sedimentary environment.The large-scale channels developed on the top of HuangUu (黄流) Formation could be the result of a big sea level drop and an increase of sediment supply.The fantastic turbidite channel developed in Late Quaternary in the slope environment has "fan-like" body and long frontal tiny avuision channel The analysis of these features suggests that the sediment supply of the study area in the post-rifting period was dominant from the Vietnam uplift in the southwest.These deepwater sedimentary features could be potential reservoirs or migration pathways for deepwater petroleum systems.     

南海北部琼东南盆地岩石热物性特征

岩石热物性是盆地模拟和预测深部温度时不可或缺的参数。琼东南盆地是当前我国海洋油气资源勘探开发的重点区 块，揭示该盆地的热状态和烃源岩热演化历史均离不开真实可靠的岩石热物性参数。前人虽然对南海北部地区的岩石热物 性开展过相关研究，仍存在实测数据偏少、代表性不足和相互矛盾等问题，亟需新增一批新的实测数据来弥补该区基础地 热参数的不足。文章对采自琼东南盆地19口钻孔的32块岩心样品开展了热导率、生热率以及密度和孔隙度等物性参数测 试，揭示了它们的空间展布特征、相互关系及其主控因素，建立了琼东南盆地新生界地层平均热导率和生热率，据此估算 出盆地沉积物的放射性生热贡献约占地表热流的33%。这些实测的岩石热物性参数为南海北部海域沉积盆地的盆地模拟和 地热相关研究提供了坚实的基础数据。     

Postrift Rapid Subsidence Characters in Qiongdongnan Basin,South China Sea

In this article,the backstripping technique was used in studying the subsidence charac-ters of the Qiongdongnan(琼东南) basin(QDNB) in order to understand its dynamic mechanism of formation and evolution.Meanwhile,the geothermal characteristics of this area were summarized,and the stretching factors(β) of the upper crust,the whole crust,and the whole lithosphere were calculated.The QDNB is characterized by high subsidence rate,high geothermal gradient,high geothermal heat flow,and the lithosphere stretching an...     

The formation mechanism of mud diapirs and gas chimneys and their relationship with natural gas hydrates: insights from the deep-water area of Qiongdongnan Basin,northern South China Sea

ABSTRACT

Mud diapirs and gas chimneys are widely developed in continental slope areas, which can provide sufficient gas for hydrate formation, and they are important for finding natural gas hydrates. Based on the interpretation and analysis of high-resolution 2D and 3D seismic data covering the deep-water area in the Qiongdongnan Basin (QDNB), northern South China Sea, we studied the formation mechanism of mud diapirs and gas chimneys and their relationship with natural gas hydrates. Mud diapirs and gas chimneys are columnar and domelike in shape and the internal regions of these bodies have abnormal reflections characterized by fuzzy, chaotic, and blanking zones. The reflection events terminate at the rims of mud diapirs and gas chimneys with pull-up reflections and pull-down reflections, respectively. In addition, ‘bright spots’ and diapiric-associated faults occur adjacent to mud diapirs and gas chimneys. The rapidly deposited and deeply buried fine sediments filling in the Tertiary in deep-water areas of the QDNB and overpressure potential derived from undercompacted mudstones, as well as from the pressurization of organic matter and hydrocarbon generation, provide abundant materials and intensive driving forces for the formation of mud diapirs and gas chimneys. Bottom simulating reflectors (BSRs) with strong amplitude and high or poor continuity were recognized atop the mud diapirs and gas chimneys and in the structural highs within the same region, indicating that they have a close relationship with each other. The mud diapirs and gas chimneys and associated high-angle faults provide favourable vertical pathways for the hydrocarbons migrating from deep strata to shallow natural gas hydrate stability zones where natural gas hydrates accumulate; however, some BSRs are characterized by weak amplitude and poor continuity, which can be affected by high temperature and overpressure in the process of the mud diapir and gas chimney activities. This mutually restricting relationship must be taken into consideration in the process of gas hydrate exploration in QDNB.