Relationship between salt diapirism and faulting in the central structural belt of the Dongying sag,Bohai Gulf basin,China

Many growth faults developed in the Dongying sag of the Jiyang depression of the Bohai Gulf basin, China. These normal growth faults consist of flower-like grabens in the hanging walls of the major faults, accompanied by reverse dragging. The central structural belt is an important structural unit in the Dongying sag, and is divided into a series of small blocks by these faults. These internal blocks can be classified into five structural classes, including parallel blocks, arc-shape blocks, plume-like blocks, ring-radial blocks, and splay blocks. It is shown that these complicated block classes and the 'negative flower-like' fault associations in the central structural belt resulted from regional NNW-SSE extension accompanying local salt diapirism and related reverse dragging, rather than strike-slip faulting. On the basis of the diapirism strength, diapers in the central structural belt can be divided into lower salt ridges and pillows, and blind piercing structures. Diapirs are mainly composed of some salts with a little soft mudstone and gypsum. These structures began forming during deposition of the Sha 3 member and terminated during deposition of the Guangtao formation.

Diapir structure and its constraint on gas hydrate accumulation in the Makran accretionary prism, offshore Pakistan

The Makran accretionary prism is located at the junction of the Eurasian Plate,Arabian Plate and Indian Plate and is rich in natural gas hydrate(NGH)resources.It consists of a narrow continental shelf,a broad continental slope,and a deformation front.The continental slope can be further divided into the upper slope,middle slope,and lower slope.There are three types of diapir structure in the accretionary prism,namely mud diapir,mud volcano,and gas chimney.(1)The mud diapirs can be grouped into two types,namely the ones with low arching amplitude and weak-medium activity energy and the ones with high arching amplitude and medium-strong activity energy.The mud diapirs increase from offshore areas towards onshore areas in general,while the ones favorable for the formation of NGH are mainly distributed on the middle slope in the central and western parts of the accretionary prism.(2)The mud volcanoes are mainly concentrated along the anticline ridges in the southern part of the lower slope and the deformation front.(3)The gas chimneys can be grouped into three types,which are located in piggyback basins,active anticline ridges,and inactive anticline ridges,respectively.They are mainly distributed on the middle slope in the central and western parts of the accretionary prism and most of them are accompanied with thrust faults.The gas chimneys located at different tectonic locations started to be active at different time and pierced different horizons.The mud diapirs,mud volcanoes,and gas chimneys and thrust faults serve as the main pathways of gas migration,and thus are the important factors that control the formation,accumulation,and distribution of NGH in the Makran accretionary prism.Mud diapir/gas chimney type hydrate develop in the middle slope,mud volcano type hydrate develop in the southern lower slope and the deformation front,and stepped accretionary prism type hydrate develop on the central and northern lower slope.The middle slope,lower slope and deformation front in the central and western parts of the Makran accretionary prism jointly constitute the NGH prospect area.

The Emergent Salt Diapirs in the East Zagros, Iran

The emergent salt diapirs of the east Zagros, Iran have been investigated by their structural positions. The study area is including of Zagros orogeny belt and Persian Gulf that both of them have been formed on northeastern part of Arabian plate. There are 84 emergent salt diapirs that originated from Hormuz formation with Infra-Cambrian to Cambrian age. Based on location, shape and orientation of the emergent salt domes in the east Zagros hinterland and Persian Gulf foreland basin, internal motivation forces in the salt deposits has been predominant compared to later tectonic forces. In the other words, most of the emergent salt diapirs are pre-orogenic diapirs and they had got prominent role as pines in determining the shape and location of next structures during to the Zagros orogeny. Finally, Neogene continental collision has a supplementary role to diapirism and salt reactivation. However there are an evidence to syn-orogenic emergent diapirs that they have got an important role in the progressive deformation.

Development of Diapirs and Accumulation of Natural Gases in Yinggehai Basin

Overpressure developed throughout most of the Yinggehai basin. The burial depth to top overpressure varied from about 1 600 m to 4 500 m, with the shallowest top overpressure occurring in the depocenter. The main cause of the overpressure was disequilibrium compaction resulting from rapid sedimentation of fine grained sediments. The overpressure was strengthened by the retention of fluids including gases due to lack of faults before diapir development. The diapirism in the Yinggehai basin was a combined result of the strong overpressure and the tensile stress field caused by the right lateral slip of the boundary fault. The diapirism, a product of the movement of overpressured fluids and plastic shales, shaped the vertical conduits from source to traps that would be absent without overpressured fluid release. Natural gas accumulation in traps in the diapir structure zones was also intermittent, which can be inferred from the inter reservoir compositional heterogeneity, transient thermal effect of fluid flow and migration fractionation.

Seismic Characteristics and Hydrocarbon Accumulation Associated with Mud Diapir Structures in a Superimposed Basin in the Southern South China Sea Margin

Mud diapirs are significant structures often associated with hydrocarbon migration and accumulation as well as gas hydrate formation in sedimentary basins.A total of 30 mud diapirs were observed in the northwestern Zengmu Basin in the southern South China Sea based on 2D multichannel seismic data.The structures are distributed along an NW-SE trend near the shelf break of the Kangxi depression in the Zengmu Basin.The mud diapirs were divided into the following according to their vertical shapes,intrusion heights,and effusive activities:tortoise,piercing,and nozzle types,which represent different evolutionary stages of diapirism.The mud diapirs in the study area suggest that the driving forces behind the mud diapirs considerably exceed the rock rupture limit of the overlying strata.Diapir formation can be divided into two steps:the accommodation of a large amount of mud in the Zengmu Basin and the movement of plastic mud induced by gravity-driven flow and regional tectonic compression.Combining seismic interpretations with analyses of the regional geology and tectonic subsidence,the current study proposes that rapid subsidence in the Kangxi depression sufficiently accommodated the vast amount of sediments deposited since the Middle Miocene,which provided favorable conditions for the growth of mud diapirs.Furthermore,the N-S directional stress field in the Zengmu Basin and the gravity slide northward along the southern slope of the depression further facilitated the development of mud diapirs since the late Miocene.The mud diapirs in the southern South China Sea margins were accompanied by the accumulation and release of overpressured fluid.

Structural Study and Analytical Modeling of Mangerak Salt Diapir (South West of Firozabad Fars-Iran)

Mangerak salt diapir is in the South West of Firuz Abad in Fars province, southern Iran and structurally, it is exposed in the simple folded belt of Kohzad Zagros. This diapir, now, is located in a transtentional zone in the overlapping parts of Koreh Bas right fault zone. The origin of this diapir is evaporative series of Hormuz, at the beginning of the Cambrian and ending Precambrian age. In this paper, we investigated tectonic structures around the salt dome of Mangerak. By promoting this salt dome, a variety of structures, such as marginal reverse faults, radial normal faults, folds and caves have been developed. In addition, many changes can be seen in the status line, and the amount and direction of the strata dip, thickness of rock units, and facies change, that all showed the downbuilding phenomenon in the diapir. The method was based on structural desert surveys and relevant measurements. The results show that salt domes above were rising during the Late Cretaceous-Paleocene, and pre-deformation of Zagros and in connection with basement Fault of Korebas, and probably, when sedimentation was in the Zagros basin, they have been exposed in the form of an island. Zagros deformation at the same time, the pressure released from the collision zone on the north side of the East and its wave motion, to the South West, exerts more pressure on the salt horizons and helps them to erupt. About Mangerak salt dome, which is exposed on the side of the Sayakh anticline axis and Basement fault of Korebas, two phenomena are effective in its exposing. Analytical modeling shows the life of the outcrop 31,000 years that this age is consistent with the effects of salt dome Neotectonic.

Seismic Signature Analysis for Clarification of Mud Volcanoes from the New Mud Diapirs Discovered at the NE-SW Moroccan Atlantic Margin

Our aim is to clarify mud volcanoes from the new mud diapirs resulting from the seismic attributes analysis applied to the low resolution Burmah oil “1973-1974” seismic data. The latter was carried out on the Larache and Tanger-Larache offshores from the NE-SW Atlantic margin. The high resolution seismic data was essential for this evaluation. In this case, we applied seismic signature analysis to four seismic profiles from the map of the seismic data set, which includes all new mud diapirs. This helped us to classify different types of mud diapirs within the seismic profiles. And as a result, six deep mud diapirs from the Prerifaine Nappe of Morocco, a shallow mud diapir, and four seafloor-piercing mud diapirs have been observed. Furthermore, the seafloor-piercing mud diapirs show a mushroom-shaped and conical-shaped cone. As they break through the seafloor, these kinds of cones characterize mud volcanoes. In this case, we may conclude that the resultant seafloor-piercing mud diapirs are likely to be mud volcanoes. However, more geological sampling and seafloor observation are still required.

Non-Diapiric Salt Domes in the West Zanjan, Central Iran

The salt domes of the west Zanjan (Central Iran) are the most important structures in the study area. They have been formed by the uplifting and erosion together under low humidity and dry and warm climate condition. The salt rocks with near to 200 meters thickness are related to lower member of the Upper Red Formation (Early Miocene) that deposited in the inverted back arc basin. They have been formed in the Central Iran basin after the Arabian-Eurasian convergence. Based on filed works and preparation of geologic map, salt domes have been cropped out during regional uplifting and erosion along hinge zone of a longitudinal anticline. Also, there is no evidence for salt diapirism and so, they are different from some salt diapirs in the southwestern margin of Zanjan that is investigated by other researchers.

Implications of Salt Tectonics on Hydrocarbon Ascent in the Eastern Persian Gulf:Insights into the Formation Mechanism of Salt Diapirs,Gas Chimneys,and Their Sedimentary Interactions

Gas chimneys,salt domes,and faults are vital to the movement of hydrocarbons within geological systems.Accurate identification of these geological features is crucial to modeling hydrocarbon resources.This study explores the processes that have shaped the eastern Persian Gulf,focusing on salt diapir characteristics,origin,and fluid migration.Plate collisions between the Indian,Eurasian,and Arabian Plates have considerably impacted salt tectonics,developing key features such as the Hormuz salt,Qatar-South Fars Arch,and Zagros and Oman orogenic structures.Salt-related features were discerned through two-dimensional seismic data and drilling records,salt movement sequences were reconstructed,and fluid expulsion patterns were delineated using attribute preferences.The results of this study revealed that fractured substrates influenced by regional tectonic forces contribute to the creation of salt diapirs,which serve as conduits for guided fluid transport.Moreover,these results showed that gravity-driven downbuilding mainly controls salt flow,while the circular arrangement of salt structures results from regional stress and interactions between different salt sources.Distinct stress-induced basement incisions compounded by the hindrance of initial salt movement by the Qatar Arch further contribute to the complex salt structure geometry.Crucially,the uplift of the Qatar Arch and stresses from the Oman and Zagros orogenies profoundly affect the salt structure geometry and depositional patterns across diverse regions,resulting in circular salt structures and gas chimneys.This study offers valuable perspectives for oil and gas exploration and provides a comprehensive understanding of the regional dynamics governing salt tectonics and hydrocarbon ascent in the eastern Persian Gulf.

Mechanism of diapirism and episodic fluid injections in the Yinggehai Basin

The diapirism in the Yinggehai Basin is a combined result of strong overpressure caused by rapid sedimentation of fine-grain sediments and the tensile stress field resulting from right-lateral slip of the boundary-fault. The diapirism showed multiple-stage, episodic nature, and caused intermittent counter-direction onlaps and changes in the thickness of strata. The shallow gas reservoirs in the diapir structural zone displayed obvious inter-reservoir compositional heterogeneities, and their filling history could be divided into 4 stages, with gases injected during different stages having different hydrocarbon gas, CO2 and N2 contents and different stable isotope compositions. The multiple-episode, intermittent activities of the diapirs, multiple-stage, non-continuous injections of fluids, and the transient thermal effect of fluid flow as well as the strong migration fractionation reflected episodic fluid injection and natural gas accumulation.

Primary study on the diapir in the north of the Yellow River delta

Based on the measuring data of landforms, high-resolution seismic profiles, drilling cores, etc. a diapir body was found in the north of the modem Yellow River delta. The diapir body with a length of 5 km and a width of 1 km is distributed on the middle to low part of the slope of an abandoned delta lobe. Its formation is related to the deformity of the soft stratum which is deposited in the prodelta and covered by the stratum of the mouth bar sediments. Research results show that its formation is very different from the Mississippi River delta’s diapirs but related to the erosion of the seabed and occurs on the location with a large eroded quantity. The soft stratum and its diapir body can result in a great hazard to marine buildings.

Mapping salt diapirs and salt diapir-affected areas using MLP neural network model and ASTER data

This study employs visible-near infrared and short wave infrared datasets of Advanced Spaceborne Thermal Emission and Reflection Radiometer(ASTER)to map salt diapirs and salt diapir-affected areas using Multi-Layer Perceptron(MLP)in the Zagros Folded Belt,Iran,and introduces the role of earth observation technology and a type of digital earth processing in lithological mapping and geo-environmental impact assessment.MLP neural network model with several learning rates between 0.01 and 0.1 was carried out on ASTER L1B data,and the results were compared using confusion matrices.The most appropriate classification image for L1B input to MLP was produced by learning rate of 0.01 with Kappa coefficient of 0.90 and overall accuracy of 92.54%.The MLP result of input data set mapped lithological units of salt diapirs and demonstrated affected areas at the southern and western parts of the Konarsiah and Jahani diapirs,respectively.Field observations and X-ray diffraction analyses of field samples confirmed the dominant mineral phases identified remotely.It is concluded that MLP is an efficient approach for mapping salt diapirs and salt-affected areas.

库车坳陷西部阿瓦特—博孜地区构造变形差异及数值模拟分析

库车坳陷西部的阿瓦特-博孜地区位于构造挤压转换区,沿走向构造变形差异显著。本文基于最新的三维地震资料和离散元数值模拟方法,对该区域进行了精细的地质建模,模拟了其形成演化过程,讨论了差异变形的控制因素。阿瓦特地区盐下沿克深断裂远距离逆冲推覆,形成上下叠置的两套沿侏罗系煤层滑脱的逆冲体系;盐上发育厚度较小的阿瓦特凹陷;盐构造以不整合型为主。博孜地区盐下在克深断裂以北为高角度基底卷入变形,以南为沿煤层的滑脱,整体为楔形叠瓦冲断构造;盐上发育厚度巨大的拜城凹陷;盐构造以整合型为主。模拟结果表明,温宿古隆起限制了中生界至古近系的沉积范围,阻碍了变形的向前传递,是造成阿瓦特-博孜地区变形差异性的最主要原因。先存盐底辟构造和南天山的差异挤压作用对该区域的差异变形也具有一定的控制作用。综合地震剖面解释和数值模拟结果的演化过程表明,该区域构造活动具有由弱到强的变化趋势,构造变形开始于早中新世吉迪克组沉积时期,在上新世早期康村组沉积之后发生显著的构造加速事件。

密西西比河谷型(MVT)铅锌矿床与蒸发岩的成因关系

MVT铅锌矿床的形成与蒸发岩关系密切,但在蒸发盐矿物发生溶解或转变为其他矿物而“消失”时,人们常忽视其曾经存在。本文基于前人研究,对蒸发岩的转变、识别特征及其与MVT铅锌成矿流体来源、硫来源及储矿构造三个方面的关系进行综述。其中,MVT矿床迁移铅锌的盆地卤水主要来自蒸发海水,少量来自蒸发岩的溶解,区域上蒸发岩的发育可指示该区具有成矿流体的发育条件。铅锌金属硫化物中的硫均来自于硫酸盐还原作用,而石膏和硬石膏等蒸发盐矿物是硫酸盐的重要提供者。蒸发岩溶解垮塌利于形成角砾岩与垮塌空间,铅锌矿化可赋存于角砾岩内或其邻近岩层中;盐底辟构造会形成有利于流体聚集和矿质沉淀的构造/化学圈闭,铅锌矿化赋存于底辟体顶部冠岩、边部过渡层和围岩、直立的底辟角砾筒或侧向底辟形成的穹隆体顶部。此外,蒸发盐矿物的假晶、残留的蒸发盐矿物是“消失”蒸发岩存在的直接证据,钠长石和方柱石、正延性玉髓/燧石、富碱土元素双锥状石英等,可指示蒸发岩曾经存在;蒸发岩溶解垮塌构造具有顺地层延伸长等特点,盐底辟构造具有穿层及角砾来自下部层位等特点,是可以协助识别蒸发岩的相关构造。可以看出,区域地层记录有蒸发沉积环境是MVT铅锌成矿必要条件,蒸发岩溶解垮塌和底辟构造是重要找矿目标。

鄂尔多斯盆地大牛地西北部地区古岩溶形成机理

全球对燃料的需求日益增加,柳杨堡地区构造特征一直备受争议,通过地震解释有着十几公里似断裂并未证实,古岩溶地貌形成成了确凿的证据,通过地震解释方法1×1地震解释、相干体技术、顺层相干体以及时间切片等技术,研究区内存在大量背斜结构构造为岩溶古地貌控制下的盐底辟及太原组-下石盒子组披覆叠加型构造。研究区内向斜主要是岩溶作用控制下的重力负载等叠加型。柳杨堡气田石炭-二叠系内断层发育主要由盐底辟及岩溶塌陷所诱发。揭示出部分地区地震相位错断,岩溶作用导致的古地貌起伏差异所引起的。加里东末期开始发育大规律的岩溶作用,形成了早期初步岩溶古地貌,这期岩溶地貌对太原组沉积有明显的控制作用。加里东末期岩溶地貌在石炭纪岩溶作用进一步作用下地貌差异逐步扩大,进一步加大了古岩溶对太原组的沉积控制。二叠纪早期,岩溶作用逐步减弱。建议下一步重点加强源内气藏评价开发的力度,选取贴近烃源岩层的砂体,进行水平井钻井评价,有利于钻取砂体内的天然气,通过深度压裂手段把烃源岩层内煤层气钻取出来。

非洲西海岸里奥-德雷盆地泥底辟平面地质结构特征研究

位于西非尼日尔三角洲盆地东缘的里奥-德雷盆地发育了大规模泥底辟,其活动时间和形成机理存在一定争议。基于对里奥-德雷盆地三维地震剖面的精细解释和平面成图,对其中中新世Nguti构造层顶面的泥底辟平面分布特征进行了重新厘定。结果表明:(1)Nguti构造层顶面的泥底辟可分为北部隐伏区、中部刺穿区和南部刺穿区;(2)北部隐伏区的泥底辟形成于Nguti构造层沉积前,是受早期沉积作用控制的被动泥底辟;中部刺穿区的泥底辟形成于上新世S0构造层沉积前,是受重力构造作用控制的主动泥底辟;南部刺穿区的泥底辟形成于Nguti构造层沉积后,是受重力构造前缘逆冲断层控制的逆冲泥底辟;(3)泥底辟整体上为向南凸出的舌状体,分东、西两段,西段为北北西-北西走向,东段为北北东-北东走向。

琼东南盆地崖北凹陷构造沉积特征及油气勘探潜力

崖北凹陷是南海琼东南盆地西北缘的边缘凹陷,勘探历程久,但受地震资料等因素制约而勘探程度低,钻井无商业发现,烃源条件落实程度低。为落实崖北凹陷油气地质条件,推动该凹陷的勘探进程,用新采集的高品质三维地震资料,结合已钻井资料,类比分析相邻盆地烃源岩地震相,厘清了崖北凹陷的断裂、构造、沉积特征和烃源岩分布,并依据区域地质应力背景分析了其成因机制,讨论了崖北凹陷油气成藏条件及勘探部署方向。结果认为崖北凹陷受5号断裂控制凹陷整体呈北断南超的构造沉积特征,纵向上“下断上拗”,新近系地层区域南倾、少有盆内断层发育,古近系断裂控凹,始新统中深湖相烃源岩主要发育在崖城9洼,崖城组煤系烃源岩发育在凹陷东南部位。最终认为,崖北凹陷烃源具有“西油东气”的特征,凹陷西部及西南斜坡和近崖城9洼的陡坡古近系圈闭是找油方向,而凹陷东南部位的凹中隆及围区圈闭天然气勘探前景好。

底辟模糊区成像处理的关键技术

底辟带具有巨大的油气勘探潜力,但受浅层气云的影响,该领域地震资料成像品质差、构造形态不准确,对周缘含油构造潜在目标的落实带来了困难。为解决底辟模糊区成像问题,本文分析近年海上新采集资料的优势及新老资料的共性特征,提出弱信号保护的保幅处理、高精度速度建模及Q深度偏移等关键技术,形成对不同采集方案具有普适性的处理对策。采用上述方法在莺歌海盆地L工区进行实际资料的应用,得出底辟模糊区核部地震资料信噪比得到提升,有效地层清晰成像,井震相关系数比原老资料提高了38%,深度域构造与测井吻合,特别是老资料重处理的效果明显,成像质量不亚于新采集资料,验证了本方法对于底辟模糊区成像挖潜的有效性,可为后续类似领域的采集及处理提供借鉴。

昆阳裂谷边缘刺穿构造力学特征及其与成矿关系厘定

昆阳裂谷位处杨子地台西南缘,历经元古代以来的构造改造活化形成近南北向分布的裂陷格局。易门铜矿床处于昆阳裂谷西部,以刺穿构造广泛分布为特征。本文以矿床所处大地构造背景为基础,从矿区凤山铜矿和狮子山铜矿刺穿构造控矿特征为切入,以控矿构造分析和平面构造统计分析为研究依据,应用矿田地质力学方法对裂谷边缘刺穿构造的发生―发展―复合―转变过程等特点进行分析研究,结合构造实际特点探索刺穿作用的发生、发展与就位,从刺穿体与矿体空间分布关系和统一的力学体系探讨刺穿过程中的成矿条件和矿产分布规律。

Contrast of Seismic Reflection Characteristics of Gas Hydrate Distribution between Northeast SCS Slope and Hengchun Ridge

By analyzing and interpreting the newly acquired seismic profile supported by the national 973 Program and synthesizing the data with other geologic ＆ geographic information, we draw conclusions as follows, a） Two seismic reflections located at the northeast South China Sea （SCS） slope and the Hengchun ridge are the Bottom Simulated Reflections （BSRs）. Yet, the genesis and process of the gas hydrate in these two areas are different because of different regional tectonics and geological environments; b） The genesis of gas hydrate located at the northeast SCS slope area is related to the broadly existing fracture zones, slumping tectosomes, and the distinctive shielding environment of pressure masking field formed by them. But the genesis of the gas hydrate at the Hengchun ridge is associated with the thrust nappe structures and accretionary wedges formed along the Manila subduction zone and the related sub-floor fluid channel system built by them; c） Since the analogous geologic bodies are broadly distributed at slope areas around SCS and the temperature-press environment is very suitable to the formation and conservation of the gas hydrate, we suggest that much more of this resource should be stored in these areas.