宽扎盆地油气地质特征

安哥拉宽扎盆地是典型被动大陆边缘盆地,完整经历了前裂谷阶段、裂谷阶段、过渡阶段及漂移阶段等4个构造演化阶段,形成了盐下、盐间和盐上3套沉积层序,并各自形成含油气系统。在对宽扎盆地构造演化、沉积特征及油气成藏条件进行分析后认为:宽扎盆地盐下、盐间和盐上3套沉积层序的油气成藏主控因素分别为拉伸断陷、盐隆起及盐构造运动;宽扎盆地盐下有利勘探区为盆地东部白垩系地堑构造区,盐间有利勘探区为盆地中东部盐隆发育部位,盐上有利勘探区为盆地东部古近系和新近系地堑发育部位;宽扎盆地今后勘探工作重点应放在盆地东部白垩系地堑构造区的盐下碳酸盐岩储层目标。     

西非加蓬盆地深水盐下局部盐胶结储层精细预测技术

西非加蓬盆地是一个典型的大西洋被动大陆边缘盆地,其深水盐下为一个高风险与高潜力并存的勘探新领域。近年来,在加蓬深水区M气田的勘探中,遇到了盐胶结型储层预测的新难题。在钻井数量少、地震资料品质有限以及缺乏成熟技术体系参考的条件下,通过对盐胶结成因机制进行深入研究,结合岩石物理分析、地震属性分析、盐胶结型砂岩储层岩石物理模型以及正、反演等关键地球物理技术手段,对盐胶结储层进行精细综合预测,探索形成了"基于地质成因机制指导下的盐胶结储层精细预测技术组合"。运用该技术有效预测了M气田的有利储层分布区,指导了M气田的勘探及评价。     

下刚果盆地油气成藏条件及勘探潜力分析

下刚果盆地油气资源非常丰富,有较大勘探前景。但由于其储层是碳酸盐岩储层,受复杂的盐岩活动影响,其构造特征及油气成藏特征也非常复杂,因此给地质认识带来了很大的困难。此文通过对该区区域地质背景、油气成藏条件和勘探潜力的综合分析,认为下刚果盆地构造演化经历了前裂谷期、同裂谷期、过渡期和漂移期四个时期。主要发育盐下和盐上两套主力烃源岩。盐上及盐下地层均具有良好的储盖组合。盐上地层构造经历了三期构造演化和两个演化序列。研究区主要发育盐下生-盐下储、盐下生-盐上储、盐上生-盐上储共三种成藏组合。认为白垩系碳酸盐岩构造具有良好的勘探前景,盐上地层是下一步勘探需要重点关注的区域,盐下构造也是较好的潜在勘探领域。研究成果对我国石油公司参与下刚果盆地或类似盆地的研究和油气勘探具有一定的借鉴意义。     

墨西哥湾深水油气勘探研究特点与发展趋势

墨西哥湾深水勘探区带是近年深水勘探活动最活跃的地区之一,通过对其石油地质条件以及勘探特点的综合分析,认为其具有优越的石油地质条件,其勘探研究具有4个特点:1地震技术革新极大推进了该区的勘探研究;2盐岩活动控制圈闭和油气藏的形成;3墨西哥湾深水区圈闭勘探呈明显的分带性;4圈闭落实和储层发育程度是主要勘探难点。并指出盐下圈闭落实和储层预测是制约该盆地勘探成功率的两大关键问题,而盐下地震成像、古盐构造恢复和古沉积水道的预测是解决这两大关键问题的主要手段。     

桑托斯盆地盐下碳酸盐岩储层伴生侵入岩预测及应用

桑托斯盆地盐下勘探领域,碳酸盐岩储层发育区岩浆岩同样广泛发育,在地震成像质量相对较差的条件下,侵入岩难于预测。分析了桑托斯盆地盐下侵入岩的成因类型特征,进而通过波动方程正演模拟的方法开展侵入岩反射特征分析。依据侵入岩地震反射特征,首先通过敏感属性预测侵入岩的平面分布范围,进而利用薄层模型完成基于调谐曲线的侵入岩厚度预测。将这一侵入岩预测技术应用到研究区,准确地预测了侵入岩发育区和侵入岩厚度,并通过概率法定量评价了侵入岩的发育体积。     

南大西洋被动陆缘共轭盆地烃源岩分布与油气富集规律——以巴西桑托斯盆地和西非纳米贝盆地为例

巴西桑托斯盆地与西非纳米贝盆地属于南大西洋中部被动大陆边缘共轭盆地,其构造演化可划分为3个阶段:裂谷期、过渡期和后裂谷期,过渡期发育阿普特阶盐。南大西洋不对称裂开控制了桑托斯盆地和纳米贝盆地在盐下早白垩世裂谷地堑、盐发育和盐上晚白垩世地层厚度等方面的差异,这些差异控制了桑托斯盆地和纳米贝盆地盐下早白垩世湖相烃源岩发育及盐上晚白垩世海相烃源岩成熟度,进而控制了桑托斯盆地和纳米贝盆地油气富集规律。桑托斯盆地深水区盐下下白垩统构造或岩性圈闭是寻找巨型油气田的有利勘探方向;浅水区盐上上白垩统地堑深凹陷盐活动相关构造或岩性圈闭是寻找大中型油气田的有利勘探方向。     

西非加蓬海岸盆地盐岩特征及其石油地质意义

加蓬海岸盆地主要分为南加蓬次盆和北加蓬次盆,是典型的西非被动大陆边缘含盐盆地,盐岩的分布具有一定规律性和差异性,并且对盆地内油气成藏具有重要的控制作用。分析了加蓬海岸盆地的构造演化与沉积充填特征、基本石油地质条件、盐岩的分布特征及其对盆地烃源岩特征、储层分布、圈闭特征、封盖条件、油气成藏,以及油气藏储量等各方面的影响与控制作用,并指出,由于加蓬海岸盆地的绝大多数油气成藏都与盐岩密不可分,因此深化盆地内盐岩展布特征的研究,对进一步评价北加蓬次盆的盐下层系及南次盆登泰尔地堑的勘探潜力具有重要意义。     

西非宽扎盆地烃源岩分布及油气成藏

宽扎盆地为南大西洋被动大陆边缘盆地,构造演化可划分为裂谷期、过渡期和后裂谷期3个阶段,过渡期发育阿普特阶盐岩.宽扎盆地主要发育3套烃源岩:盐下下白垩统阿普特阶湖相烃源岩、盐间早白垩世阿普特期海相烃源岩和盐上古近纪始新世海相烃源岩.宽扎盆地油气田均围绕烃源灶分布,烃源岩是该盆地油气藏形成与分布的主控因素.宽扎盆地发育4套含油气系统(盐下下白垩统、盐间下白垩统、盐上上白垩统和盐上古近系)以及2种成藏模式(古生新储和自生自储).宽扎盆地深水21区块Cameia-1井、Cameia-2井以及21区块Azul-1井盐下地层获得重大油气勘探突破,表明该盆地深水区存在盐下下白垩统含油气系统并发育优质湖相烃源岩,提高了宽扎盆地深水区油气勘探潜力.     

西非陆缘盆地中南段构造与沉积研究

作为全球油气勘探的热点,西非陆缘盆地中南段已经获得了大量的油气发现,而且中国石油企业在该区域已有开发区块。巨厚的阿普特期盐岩将该区分为盐下陆相裂谷和盐上海相被动陆缘两套勘探层系,该套盐岩作为良好的盖层起到了保存油气的作用,但由于其遮蔽效应,导致了地震资料在盐下层成像品质差,造成了盐下层序研究程度低,裂谷主控断裂、裂谷规模及展布形态不清楚,严重制约了盐下油气勘探的进程。本文综述了国内外近年来关于西非陆缘盆地中南段构造演化、盐上和盐下层序构造、盐岩特征以及盆地构造的研究进展。目前针对盐下裂谷研究主要集中在陆区,海域研究程度低,现有的盆地构造单元划分是以盐上层序为主,并不适用于盐下油气勘探先进问题,建议加强该区基础地质与地球物理研究,开展与南美东部陆缘盆地盐下裂谷对比研究,提高盐下地震成像品质,重视地震-重磁联合研究,通过地质与地球物理综合研究,尽快查明盐下裂谷主控断裂、基底形态、隆坳格局等油气分布控制因素,为中国石油公司在该区油气战略选区及下步勘探部署提供依据。     

琼东南盆地南部中新统“丘”形反射成因探讨

在琼东南盆地南部中新统梅山组广泛发育“丘”形反射, 对其识别分析具有重要的意义。这些“丘”形反射主要分布在北礁凹陷及周缘斜坡带上, 在顶底界面呈强反射, 在内部成层、杂乱或为空白反射, 有时在顶部见披覆沉积, 从盆地中心北礁凹陷向边缘斜坡带迁移生长。通过对“丘”形反射的古构造和古地理背景、几何学特征及地震响应特征等方面综合分析, 对其成因进行了探讨, 排除了其为生物礁、泥底辟以及火山丘的可能, 认为其可能为深水环境底流作用下形成的等深流沉积或某种沉积物波。     

Sequence boundaries and salt diapirism in the Balearic abyssal plain, western Mediterranean

 Unconformities and lapout structures in seismic profiles from the Balearic abyssal plain northeast of Menorca are apparently related to salt dome movements. Six sequence boundaries, observed around different salt structures, could be correlated throughout the area surveyed. The synchronous episodic movements are interpreted to be related to glacial/interglacial sea level fluctuations. During periods of low stand, more material is eroded from the continental shelf than during high stand, and it is deposited in the deep sea, in turn loading the Miocene salts and activating diapirism. DSDP site 372 and site survey seismic lines were used to define the Pliocene–Pleistocene boundary and to date the sequence boundaries.     

The structural styles and formation mechanism of salt structures in the Southern Precaspian Basin: Insights from seismic data and analog modeling

Using the seismic profiles and analog modeling, this paper addresses the salt structures in the M and B blocks in the Southern Precaspian Basin. The salt structural features, the formation mechanism and the controlling factors of structural deformation are investigated and discussed systematically. The interpretation of the seismic profiles shows that typical salt-related structures include salt wall, (flip-flop) salt diapir, salt roller, salt pillow (dome), salt weld, salt withdrawal minibasin and drag structure (or drape fold). In addition, model results demonstrate that the gravity spreading driven by progradation and aggradation is probably the primary factor in controlling the formation of the salt structures in the research area. Due to the differential loading driven by progradation, passive salt diapir developed near the progradational front followed by the formation of intrasalt withdrawal minibasin bounded by two salt diapirs, and secondary reactive triangle salt diapir or salt pillow might form within the intrasalt withdrawal minibasin. Model results also indicate that the pattern of the subsalt basement has important influence on the formation and evolution of salt structures. Salt diapirs primarily developed along the margin of the subsalt uplift basement, where high shear deformation was induced by differential sedimentary loading between the uplift area and the slope area.     

Geological evolution and hydrocarbon potential of the salt-cored Hoodoo Dome,Sverdrup Basin,Arctic Canada

The evaporite-cored Hoodoo Dome on southern Ellef Ringnes Island, Sverdrup Basin, was examined to improve the understanding of its structural geological history in relation to hydrocarbon migration. Data from geological mapping, reflection seismic, thermal maturity and detrital apatite (U–Th)/He cooling ages are presented. Five stages of diapirism are interpreted from Jurassic to Recent times:1. 180 to 163 Ma (pre-Deer Bay Formation; development of a diapir with a circular map pattern).2. 163 to 133 Ma (Deer Bay to lower Isachsen formations; development of salt wings).3. 115 to 94 Ma (Christopher and Hassel formations; ongoing diapirism and development of an oval map pattern)4. 79 Ma (Kanguk Formation; reactivation of the central diapir).5. 42 Ma to 65 Ma (Eurekan Orogeny; tightening of the anticline).During phase1, the Hoodoo diapir was circular. During phase 2, salt wings formed along its margin. During phase 3, the Hoodoo Dome geometry evolved into a much larger, elongate, doubly plunging anticline. Phase 4 is inferred from thermochronology data as indicated by a cluster of cooling ages, but the extent of motion during that time is unknown. During Phase 5 the dome was tightened creating approximately 700 m of structural relief. Denudation since the end of the Eurekan Orogeny is estimated to be about 600 m.A one dimensional burial history model predicts hydrocarbon generation from Middle and Late Triassic source rocks between 140 and 66 Ma, with majority of hydrocarbon expulsion between 117 and 79 Ma. Hydrocarbon generation post-dates salt wing formation, so that this trap could host natural gas expelled from Triassic source rocks.     

Salt structures in the Laizhouwan depression, offshore Bohai Bay basin, eastern China: New insights from 3D seismic data

Using the new high-quality 3D seismic data, this paper addresses the salt structures in the KL11 area of the Laizhouwan depression in the southern offshore Bohai Bay basin. In the study area, the salt in the Sha-4 Member of the Paleogene Shahejie Formation thickened, and then formed an S–N trending salt wall, which changes shape regularly along its trend from salt diapir to salt pillow. The change in thickness of the suprasalt layers record five growth phases of the salt wall from the Eocene to the Quaternary: (1) early diapirism, (2) active diapirism, (3) passive diapirism, (4) relative structural quiescence, and (5) arching. The evolution of the salt structures was mostly governed by the multi-phase compression induced by the dextral strike-slip of the Tan–Lu fault, which formed a restraining bend in the study area. There was an original passive stock in the south, which was later tectonically squeezed by E–W compression and became a diapir. As the shortening propagated to the north from the original stock, the salt pillow was created in the north. Relative structural quiescence then followed until the next phase of compression, which arched the thick roof of the salt wall.     

Bannu Basin,fold-and-thrust belt of northern Pakistan: Subsurface imaging and its implications for hydrocarbon exploration

The Trans Indus-Salt Range, located in northern Pakistan, is one of the most tectonically active fold-and-thrust belts and comprises three main regions: the Potwar-Salt Range, the Kohat-Surghar Range and the Bannu Basin-Khisor Range. Of these, the Bannu Basin is the least studied and only a handful of publically accessible datasets and publications are available. Recently made public 2D seismic profiles and well data from the Bannu Basin indicate the presence of salt as well as evidence for a main detachment surface which is Neoproterozoic in age. Our findings suggest that the Salt Range Formation could be the main detachment for the entire basin.Interpretation also shows a Miocene-Eocene basin-wide unconformity that marks the Himalayan orogenic event which separates the pre-Himalayan from the syn-Himalayan sedimentary units. On the basis of seismic reflection data, we conclude that the basin experienced three main tectonic settings. An early stage of pre-Himalayan passive tectonic environment is followed by the compressional Himalayan tectonics which resulted in uplifted areas sourcing the fluviatile fill of the subsided basin. During this time, sedimentation from the northern margin of the basin may have influenced the southward flow of salt. This is followed by a more recent stage of thrusting that produced folds and thrusts deforming all of the sedimentary units.Structural geometries suggest that prospective traps are developed mainly in the anticlines outlining the eastern and western boundaries of the Bannu Basin, as well as the southern zone of the basin. Furthermore, the presence of salt diapirism and transpression zones together with numerous oil seeps in and around the basin increase the probability of hydrocarbon accumulation and indicate great potential for future exploration.     

Diagenesis in salt dome roof strata: Barite - calcite assemblage in Jebel Madar,Oman

Halokinesis causes a dynamic structural evolution with the development of faults and fractures, which can act as either preferential fluid pathways or barriers. Reconstructing reactive fluid flow in salt dome settings remains a challenge. This contribution presents for the first time a spatial distribution map of diagenetic phases in a salt dome in northern Oman. Our study establishes a clear link between structural evolution and fluid flow leading to the formation of diagenetic products (barite and calcite) in the salt dome roof strata. Extensive formation of diagenetic products occurs along NNE-SSW to NE-SW faults and fractures, which initiated during the Santonian (Late Cretaceous) and were reactivated in the Miocene, but not along the E-W fault, which was generated during Early Paleocene time. We propose that the diagenetic products formed by mixing of a warm (100 °C) saline (17 wt% NaCl eq.) ⁸⁷Sr enriched (⁸⁷Sr/⁸⁶Sr: 0.71023) fluid with colder (35 °C) meteoric fluid during Miocene to Pleistocene. The stable sulphur and strontium isotope composition and fluid inclusion data indicate that a saline fluid, with sulphate source derived from the Ara Group evaporite and Haima Supergroup layers, is the source for barite formation at about 100 °C, predominantly at fault conjunctions and minor faults away from the main graben structure in the dome. In the Miocene, the saline fluid probably ascended along a halokinesis-related fault due to fluid overpressure (due to the rising salt and impermeable layers in the overlying stratigraphic sequence), and triggered the formation of barite due to mixing with barium-rich fluids, accompanied by a drop in temperature. Subsequently, evolving salt doming with associated fault activity and erosion of the Jebel allows progressively more input of colder meteoric fluids, which mix with the saline warmer fluid, as derived from stable isotope data measured in the progressively younger barite-associated calcite, fault zone calcite and macro-columnar calcite. The reconstructed mixing model indicates a 50/50 to 90/10 meteoric/saline fluid mixing ratio for the formation of fault zone calcite, and a 10 times higher concentration of carbon in the saline fluid end member compared to the meteoric fluid end member. The presented mixing model of salt-derived fluids with meteoric fluids is suggested to be a general model applicable to structural diagenetic evolution of salt domes world wide.     

沧东凹陷沙河街组地震地层分析

利用地震资料及地质、钻井资料,对沧东凹陷沙河街组地震反射剖面进行了地震界面及地震层序划分,对其反射特征进行了较详细的描述。在进行地震相及沉积相划分和分析的基础上,对各层序的沉积特征进行了分析,这为该地区沉积盆地的油气生储盖特征提供了基础资料[1]。     

The Valhall Field: a geological overview

The Valhall Field is located within the Central Graben in the southern part of the Norwegian North Sea. The discovery well, 2/8-6, was drilled in 1975 and the field went on production in 1982. Production is currently 55 000 barrels of oil per day. The Valhall Field structure trends NW-SE and has an areal closure in excess of 60 000 acres. The hydrocarbon column measures ～200 m. The structure is located on an elongate anticlinal feature called the Lindesnes Ridge, which developed during Late Cenomanian to Oligocene tectonic movements. The geophysical evaluation of the field is complicated by the existence of a gas-charged Tertiary section which obscures the deeper seismic reflections. Vertical seismic profiles (VSPs) have been utilized in an attempt to resolve the reservoir configuration. Reservoirs occur both in the Tor Formation (Maastrichtian), and in the underlying Hod Formation (Turonian-Coniacian). The Tor Formation is represented by a largely allochthonous chalk facies which thins regionally to the southwest. A crestal graben is developed in which the Tor Formation is locally thick. Autochthonous chalks are characteristic of the Hod Formation. Primary porosity of the chalk varies between 36 to 50% on the crest of structure. Preservation of such high porosity is primarily due to formation overpressure inhibiting mechanical compaction of the chalk. The field contains paraffinic oil of 36 API gravity. It originated from the Upper Jurassic Kimmeridge Clay Formation, which is at peak oil generating capacity under the field at present day.     

川东地区长兴组生物礁有利相带预测技术研究

川东地区长兴组生物礁为四川盆地海相碳酸盐岩主要含气层,生物礁有利相带预测技术的研究对生物礁储层的勘探生产有重要的指导意义.通过对川东地区长兴组生物礁有利相带预测技术的研究所得到的结果表明：目前地震属性分析技术和时差分析技术为生物礁有利相带预测中最常用和最有效的关键技术;层拉平分析技术为生物礁有利相带预测的辅助技术,能近似反映古沉积环境;地震谱分解技术能够精细地刻画相带边界,但是对资料信噪比要求较高.     

合成地震记录制作在油气勘探中的应用

合成地震记录的制作是油气勘探的基础,它是连接地质、测井和地震资料的桥梁。从合成地震记录的基本原理出发,结合油气勘探过程中的具体研究实例,分析了VSP资料与合成地震记录时深关系的差异性、地震资料对合成记录的影响和子波的选择;最后,利用勘探实例着重用阐述合成地震记录在油气勘探中的应用,主要包括把握区域速度、明确储层地震响应特征、识别地震资料的多次波和剔除地震资料的地质＂假象＂。