Petrophysical,seismic structural and facies analysis of the Miocene reservoirs of East Morgan oil field,Gulf of Suez,Egypt

The Gulf of Suez is characterized by the presence of many hydrocarbon-bearing fields including reservoirs ranging in age from the Palaeozoic to the Tertiary. East Morgan oil field is one of the promising oil fields which are located in the southern part of the Gulf of Suez and tapping hydrocarbon deposits and potentials of the Miocene age. The purpose of this work is to evaluate the Miocene sediments of the Asl and Hawara Formations in East Morgan oil field (western sub-basin) through carrying out an integrated petrophysical, seismic structural and sequence stratigraphy study. Quantitative well logging analyses are carried out over Asl and Hawara Formations to throw light over their hydrocarbon potentiality. Good oil saturation is exhibited by the sand sections of Asl Formation, and fair to good are assigned for those of Hawara Formation in the Belayim dip province. On the other hand, a little hydrocarbon saturation is represented by both formations to the south of the study area in the Morgan accommodation zone (MAZ). The estimated petrophysical parameters of Asl reservoir throughout the study area range between 4 % and 10 % for effective porosity, 18 % and 89 % for shale volume and 2 % and 48 % for hydrocarbon saturation. Meanwhile, the ranges of 1–8 %, 20–98 % and 2–32 % are given for Hawara Formation for effective porosity, shale volume and hydrocarbon saturation, respectively. The lateral distribution maps show that the central and the western parts of the MAZ attain the best petrophysical parameters and hydrocarbon potentiality. Seismic facies analysis, structural framework and depositional history of the study area were studied through interpreting the seismic reflection data of 27 seismic profiles. A number of geo-seismic cross sections are constructed and interpreted to investigate the structural setting of the study area and clarify the main structural elements that affect the hydrocarbon bearing reservoirs. A group of simple NW–SE step-like normal faults, parallel to the Clysmic trend, is found cutting through the reservoir rocks at the bottom layers of the section (Rudeis Formation) and extending upwards to overlying layers (Zeit Formation). Some graben- and horst-shaped structures are found and usually bounded by two sets of oppositely dipping normal step-like cross faults. The seismic facies and sequence analysis revealed that the Miocene rocks are subdivided into two major third-order depositional sequences (S1 and S2), separated by two major depositional sequence boundaries (DSB1 and DSB2). The first sequence (S1, Lower–Middle Miocene rocks) is of prime interest, as it encounters the main hydrocarbon reservoirs in the study area (Asl and Hawara Formations that are equivalent to Rudeis Formation). The seismic facies of this sequence are characterized by low to moderate amplitude, discontinuous horizons and bounded by the depositional sequence boundary (DSB1) at the top. The reflection geometry at the cycle boundaries is considered as erosional truncation, toplaps and even concordant along the upper boundary of the cycle. The external form of these sediments is considered as sheet-like and wedge-shaped units. The entrapment of hydrocarbons seems to be of a combined effect of the stratigraphic and structural elements. It appears clear that both of the step-like structural fault system and the lateral variation of facies are the key parameters that control the accumulation of hydrocarbon in this area and in East Morgan field as a whole.     

Geochemistry and origin of rare earth elements (REEs) in the Shengli River oil shale, northern Tibet, China

The Shengli River-Changshe Mountain oil shale zone, located in the North Qiangtang depression, northern Tibet plateau, represents a potentially large marine oil shale resource in China. Twenty-eight samples including oil shale, micritic limestone and marl were collected from the Shengli River area to determine the contents and distribution patterns of rare earth elements (REEs) in marine oil shale. Oil shale samples from the Shengli River area have high ash yield (61.86–67.48%) and TOC content (8.02–13.67%) with low total sulfur (S_t,d) content (0.76–1.39%) and intermediate shale oil content (3.60–16.30%). The total rare earth element (ΣREE) content in oil shale samples is notably depleted (46.79–67.90 μg/g), approximately one third of the mean value of the North American Shale Composite (NASC), and lower than that of world-wide black shales and Chinese coals, but higher than that of world-wide coals and micritic limestone samples (29.21 μg/g) from the Shengli River area. The oil shale samples from the Shengli River area exhibit shale-like Chondrite or NASC-normalized REE patterns similar to those of micritic limestone and marl samples from this area, indicating that REEs of these different lithological samples may have been derived from a similar terrigenous source.REE contents of oil shale samples are highly positive correlated with ash yield and show a positive correlation with Fe and a weakly positive correlation with organic sulfur, and the vertical variations of REEs mainly follow those of Si, Al, K and Ti. All these facts indicate that the REE contents in oil shale seams are mainly controlled by clay minerals and, to a lesser extent, by pyrite, as well as partly associated with oil shale organic constituents. Rare earth elements in the Shengli River oil shale have originated from two sources: a felsic volcanic rock source and a clastic or/and limestone source.     

Geophysical interpretation of the Rashidpur structure Surma Basin,Bangladesh

The Rashidpur structure is located in the southern part of the Surma Basin, Bangladesh. This paper presents an integrated interpretation of seismic and other geophysical data considering the available geologic information in terms of hydrocarbon potential of this structure. The study area lies within a gravity high and a high magnetic intensity. Fifteen seismic sections of the study area have been analyzed to interpret the subsurface geology, structure and stratigraphy. Based on the analysis of seismic sections and correlation with well data, four prominent reflecting horizons have been identified. The litho-stratigraphy of the Rashidpur structure is prepared on the basis of well information. The lithological sequences encountered in the Rashidpur structure range in age from Miocene to Plio-Pliestocene. The gas producing sands of the structure are within Bokabil to Bhuban Formations of the Miocene age. The seismic study indicates that the Rashidpur structure is a narrow, NS elongated anticline affected by a major reverse fault on the eastern flank. It is an asymmetrical anticline with the axis swinging slightly to the east on the northern plunge and thus attaining a slight concavity to the east. There are various geophysical indications of hydrocarbons in this structure.     

Quantifying a critical marl thickness for vertical fracture extension using field data and numerical experiments

In fractured reservoirs characterized by low matrix permeability,fracture networks control the main fluid flow paths.However,in layered reservoirs,the vertical extension of fractures is often restricted to single layers.In this study,we explored the effect of changing marl/shale thickness on fracture extension using comprehensive field data and numerical modeling.The field data were sampled from coastal exposures of Liassic limestone-marl/shale alternations in Wales and Somerset(Bristol Channel Basin,UK).The vertical fracture traces of more than 4000 fractures were mapped in detail.Six sections were selected to represent a variety of layer thicknesses.Besides the field data also thin sections were analyzed.Numerical models of fracture extension in a two-layer limestone-marl system were based on field data and laboratory measurements of Young's moduli.The modeled principal stress magnitude σ_3 along the lithological contact was used as an indication for fracture extension through marls.Field data exhibit good correlation(R~2=0.76) between fracture extension and marl thickness,the thicker the marl layer the fewer fractures propagate through.The model results show that almost no tensile stress reaches the top of the marl layer when the marls are thicker than 30 cm.For marls that are less than 20 cm,the propagation of stress is more dependent on the stiffness of the marls.The higher the contrast between limestone and marl stiffness the lower the stress that is transmitted into the marl layer.In both model experiments and field data the critical marl thickness for fracture extension is ca.15-20 cm.This quantification of critical marl thicknesses can be used to improve predictions of fracture networks and permeability in layered rocks.Up-or downsampling methods often ignore spatially continuous impermeable layers with thicknesses that are under the detection limit of seismic data.However,ignoring these layers can lead to overestimates of the overall permeability.Therefore,the understanding of how fractures propagate and terminate through impermeable layers will help to improve the characterization of conventional reservoirs.     

盐间页岩油韵律层地震响应模拟及页岩薄储层厚度预测

江汉盆地潜江凹陷潜江组页岩油储层的地质结构为韵律背景下的页岩薄层,由于地震分辨率的限制,常规地震勘探方法难以精确描述盐间页岩油薄储层厚度的空间展布。因此,应用现有地震资料,探索适用于韵律结构中页岩薄层的地震预测方法具有重要意义。本文通过地震传播矩阵方法计算并分析研究区目标韵律层的地震响应特征,系统模拟并分析非均匀薄互层结构中页岩薄层的厚度、纵波速度等变化时地震波的反射动力学特征,发现地震反射波形的振幅和相位随非均匀页岩薄层的纵波速度和厚度的变化产生明显的变化,这些变化是本文页岩薄层厚度预测的基础。结合测井分析构建韵律层地质地球物理模型,模型空间考虑了页岩薄层纵波速度和厚度共99种组合变化的情况。通过求取目标层实际地震反射波形与构建的模型空间中地震波形的最佳匹配,提出基于反射波形的页岩薄储层厚度的地震预测方法,预测研究区页岩薄层厚度变化范围为5~20 m,并且由西南向东北呈增加趋势。预测页岩薄层厚度与测井解释具有较高的一致性,验证了本文地震预测方法的有效性。     

Palynofacies,organic geochemical analyses and hydrocarbon potential of some Upper Jurassic-Lower Cretaceous rocks,the Sabatayn-1 well,Central Yemen

The current work investigates the hydrocarbon potentiality of the upper Jurassic–lower Cretaceous rocks in the Marib-Shabwah Basin, Central Yemen, through the Sabatayn-1 well. Therefore, palynological and organic geochemical analyses were carried out on 37 ditch cutting and 12 core samples from the well. Palynofacies analysis of the Madbi (late Oxfordian–early Tithonian) and Nayfa (Berriasian–Valanginian) Formations sediments indicates deposition of their organic-rich shale, calcareous shale and marl in middle to outer shelf environments under dysoxic–anoxic conditions, containing mainly kerogen of types II to III. However, the shales of the lower Sabatayn (Tithonian) Formation were deposited in an inner shelf environment of prevailing dysoxic–suboxic conditions, and show kerogen types III to II. Regional warm and relatively dry palaeoclimate but with local humid conditions developed near the site of the well is thought to have prevailed during deposition of the studied well sediments. The geochemical analyses of the Madbi Formation show higher total organic carbon content (TOC) than the overlying Sabatayn and Nayfa formations: it is varies between 1.2 and 7, and with average 4 wt% TOC, and the obtained S2 values (～3–10, average 7 mg HC/g rock) indicates that the Madbi Formation is mainly good source rock. It shows a good petroleum potential of 4–11 mg HC/g dry rock, and the Rock-Eval pyrolysis indicates mainly kerogen types II to III (oil to gas prone) of hydrogen index values (132–258, and only one sample from Lam Member is of 360 and average 215 mg HC/g TOC). The thermal maturation parameters as T _max (425–440 °C), production index (average 0.13 mg HC/g rock) and thermal alteration index (2 to 2+) reflected that this formation is present at margin of maturation to early mature stage oil window. So, the Lam Member (upper part) of the Madbi Formation is considered the main hydrocarbon (oil and gas) source rock in the Marib-Shabwah Basin. Accordingly, we predict that the Meem Member is an active source for gas and oil accumulations in the overlying sandstone reservoir of the Sabatayn Formation in the Sabatayn-1 well.     

Log-derived petrophysical characteristics and oil potentiality of the Upper Qishn Clastic Member,Masila Basin,Yemen

The Lower Cretaceous Qishn Formation at Masila Basin, Yemen, contains substantial amounts of proven crude oil. It is divided into a lower shaly silisiclastic member and an upper carbonate member. In the present work, detailed formation evaluation of the Upper Qishn Clastic Member was carried out using the digitized well logging data from 12 wells, via computer-assisted analysis, to accomplish its reservoir characteristics and oil potentiality. Accordingly, the true resistivity (R _t), porosity (total φ _t and effective φ _e), shale content (V _sh), permeability (K), water saturation (S _w), hydrocarbon saturation (S _h) (movable “S _hm” and residual “S _hr”) and lithologic composition in each well were estimated, analyzed, and illustrated versus depth on litho-saturation cross-plots. Likewise, the areal distribution of such parameters alongside the member in the investigated area and their relations to geological setting were defined from the constructed isoparametric contour maps. Based on the obtained results, the components of Upper Qishn Clastic Member of Masila Basin are mainly shaly sandstone and minor calcareous sandstone with considerable amount of shale. Regionally, the Member was deposited on an inner neritic to shallow-marine platform setting. It is interpreted as a good-quality reservoir rock which has been established from high total porosity (15–22 %), good effective porosity (8–13 %), and variable shale volume (24–31 %). A number of high hydrocarbon saturation zones (exceeding 55 %) are detected through intervals having S _w?<?60 % and S _hm?>?20 % which have been considered as economic oil producers. The storage and pay capacities of the reservoir intervals have been resolved. The obtained results were confirmed from the available data of core analyses and production tests. The Upper Qishn Clastic Member reveals promising reservoir characteristics which should be taken into consideration during future development of the oilfields in the area.     

三维地震约束多点建模降低井间砂体预测的不确定性

本文利用垦71断块的测井数据和三维地震数据,运用多点统计建模方法,和软硬数据结合的原理,进行了油藏建模的井间砂体预测研究。本文的研究包括,三维地震数据的质量控制,软硬数据结合,多点统计学建模应用,训练图象的制作,砂体概率生成曲线的选用。在这基础上,本文利用测井数据和三维地震数据结合的建模结果,与仅用测井数据的建模结果进行了对比。这种分析和对比,以地震泥质含量剖面图为对比根据,分为三个层次:研究层段的上部和下部的砂泥岩分布对比,不同井及其周围地区的砂泥岩分布对比,不同随机种子产生的多个测井砂体预测剖面图之间、和多个井震砂体预测剖面图之间分别对比。本文结果可以说明,地震约束的多点统计建模结果明显地提高了井间砂体预测的合理性,并降低了油藏建模的不确定性。     

山东省油页岩资源特征及开发利用前景

随着石油资源可用量的不断减少,页岩气、油页岩、油砂与稠油作为一种新能源,近年来备受人们的重视。山东省存在着丰富的油页岩资源。近年来笔者通过收集前人相关资料、野外地质填图、钻探编录、典型矿区考察、关键样品化验分析等手段对其进行了初步研究,初步认识了山东地区油页岩的资源特征及其形成环境,对未来山东地区油页岩矿的预测及潜力的评价具有一定的指导与借鉴作用。     

Stratigraphic status,age, and paleobathymetry of the Grey shale Member,Dalmiapuram Formation,Cauvery Basin,India

Grey shale Member of the Dalmiapuram Formation, Ariyalur Group, Cauvery Basin, India was studied for its stratigraphic position, age, and paleobathymetry with a re-look into the lithological relationship and foraminifer assemblages in the deepened limestone mine excavations at M/s Dalmia Cements, Dalmiapuram. Twenty grey shale samples from Kovandankurchchi (pit-4) and Kallakkudi mines yielded diversified calcareous, benthic, and rare index planktic foraminifera. The foraminiferal assemblages suggest a latest Albian age and middle neritic depositional conditions. The abundance of kaolinite and smectite clay minerals relate to warm/humid climate which corroborate with rising relative sea level during grey shale deposition. The grey shale occurs in patches within the marl bedded limestone member which exhibits cyclic deposition of limestone and marl. The limestone mine sections demonstrate that the grey shale forms part of basal marl bedded limestone, directly overlying the coral algal limestone. The present study demonstrates that the grey shale outcrops in Dalmiapuram Formation should be placed stratigraphically as part of marl bedded limestone. The member status for grey shale which is current usage stands discounted.     

陆相油藏中砂泥岩互层时移地震遮掩效应及其对时移地震资料解释的影响

从差异波形特征的角度出发,分析时移地震差异波形特征与砂泥岩互层油藏中油层速度变化的关系。通过建立由5层地层组成的楔形地质模型,运用褶积公式及时移地震求差公式,得到泥岩速度为2 400 m/s和砂岩速度为2 700m/s条件下,互层中砂岩速度变化±150 m/s的时移地震响应。研究结果表明:砂泥岩互层的差异波形是一个多峰复合波,泥岩夹层的厚度是决定差异波形特征的一个主要因素,并且存在一个临界值,即四分之一主波长;如果泥岩夹层的厚度小于这一临界值,就会发生遮掩效应,即顶部油层的时移地震响应可以掩盖中、下部油层的时移地震响应。     

陆相汕藏中砂泥岩互层时移地震遮掩效应及其对时移地震资料解释的影响

从差异波形特征的角度出发,分析时移地震差异波形特征与砂泥岩互层油藏中油层速度变化的关系.通过建立由5层地层组成的楔形地质模型,运用褶积公式及时移地震求差公式,得到泥岩速度为2 400 m/s和砂岩速度为2 700 m/s条件下,互层中砂岩速度变化±150 m/s的时移地震响应.研究结果表明砂泥岩互层的差异波形是一个多峰复合波,泥岩夹层的厚度是决定差异波形特征的一个主要因素,并且存在一个临界值,即四分之一主波长;如果泥岩夹层的厚度小于这一临界值,就会发生遮掩效应,即顶部油层的时移地震响应可以掩盖中、下部油层的时移地震响应.     

准噶尔盆地吉木萨尔地区二叠系芦草沟组油页岩地球化学特征与成矿条件

【研究目的】本文旨在通过对比准噶尔盆地吉木萨尔地区二叠系芦草沟组高品位和低品位油页岩的品质和成因差异,揭示高品位油页岩的特殊成矿条件。【研究方法】对吉木萨尔地区两个剖面采集的露头样品,进行TOC、热解、含油率、微量、稀土元素测试,从而开展高品位和低品位油页岩有机地球化学特征,微量稀土元素特征及成矿条件差异分析。【研究结果】研究区高品位油页岩有机质类型为I型;低品位油页岩有机质类型为I-II1型。高品位和低品位油页岩中B、Ba、Cr、Nb、Sr、V、Zr等微量元素含量差异明显,高品位油页岩中各稀土元素平均含量和各样品稀土元素分布区间都小于低品位油页岩,且外源元素富集程度也相对更低,显示了更少的陆源碎屑输入。微量元素比值显示,研究区油页岩形成于温暖湿润气候,淡水—半咸水,还原环境。高品位油页岩与低品位油页岩相比,形成时水体盐度值更大,有机质生产力更高。【结论】温暖湿润气候背景下,相对较少的陆源碎屑供给,减少了对有机质的稀释和氧化破坏,同时较高的水体盐度值更利于水体分层,从而形成一个长时间的还原环境,再加上更高的有机质生产力,从而形成了高品位油页岩。     

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。     

Velocity and Structural Modeling of Mesozoic Chiltan Limestone and Goru Formation for Hydrocarbon Evaluation in the Bitrisim Area, Lower Indus Basin, Pakistan

The present study focuses on building a workflow for structural interpretation and velocity modeling and implementing to Jurassic-Cretaceous succession (Chiltan Limestone and Massive sand of the Lower Goru Formation). 2D-Migrated seismic sections of the area are used as data set and in order to confirm the presence of hydrocarbons in the study area, P and S-wave seismic velocities are estimated from single-component seismic data. Some specific issues in the use of seismic data for modeling and hydrocarbon evaluation need to deal with including distinguishing the reservoir and cap rocks, and the effects of faults, folds and presence of hydrocarbons on these rocks. This study has carried out the structural interpretation and modeling of the seismic data for the identification of traps. The results demonstrate existence of appropriate structural traps in the form of horst and grabens in the area. 2D and 3D velocity modeling of the horizons indicates the presence of high velocity zones in the eastern half of the study while relatively low velocity zones are encountered in the western half of the area. Two wells were drilled in the study area (i.e. Fateh-01 and Ichhri-01) and both are dry. Immature hydrocarbons migration is considered as a failure reason for Fateh-01 and Ichhri-01 well.     

鄂尔多斯盆地富县地区延长组物源体系分析

物源问题一度成为制约富县地区延长组油气勘探的焦点。作者充分利用了研究区的野外露头、钻孔资料和地震资料,系统分析了能够用于指示古物源方向的6种关键参数——实测古水流方向、砂体展布走向、极端暴露标志（煤）和覆水标志（油页岩）空间分布规律、重矿物组合分异特征、三角洲沉积体系前积结构（地震剖面）、鄂尔多斯盆地区域古构造—古地理特征等。综合研究表明,富县地区晚三叠世延长组的沉积物来自于盆地东北部,研究区不存在南部物源体系。     

鄂尔多斯盆地大牛地气田上古生界沉积演化特征

鄂尔多斯盆地上古生界海陆变迁过程中其沉积演化特征决定了气田内储层成因类型,分布特征和分类评价。通过对大牛地地区太原组-山西组-下石盒子组岩芯观察,结合测井,地震等资料分析,综合确定太原组为滨浅海环境,下部发育碳酸盐岩斜坡体系,上部为障壁-潮坪-潟湖沉积体系;受北部物源区抬升影响,陆源推进和尚未完全褪去的海水影响,山西组为海陆过渡环境,发育潮控辫状三角洲沉积体系;伴随北部物源区逐渐抬升,陆相碎屑显著推进至研究区,下石盒子组底部形成陆相河流环境,发育辫状-曲流河沉积体系;大牛地上古生界整体呈陆进海退特征。由海向陆变迁过程中,太原组和山西组发育的煤层是研究区重要烃源岩;太原组上部障壁砂坝和潮道等砂体,山西组下部辫状河道,潮道和潮砂坝砂体和下石盒子组底部厚层叠置辫状-曲流河道砂体是研究区内上古生界重要的产气储层。     

藏北羌塘盆地胜利河油页岩干酪根特征及碳同位素指示意义

胜利河油页岩位于北羌塘盆地南部, 走向长超过34 km, 宽9 km。笔者对该油页岩各岩系干酪根进行了分离、镜鉴、元素分析和碳同位素分析, 结果表明, 该油页岩干酪根为Ⅱ型干酪根, 油页岩中干酪根含量较高, 介于15.79%~20.37%, 具有富氢少氧的特征, 其H/C和O/C比率分别为1.11~1.19和0.08~0.25, 为胜利河地区非常好的烃源岩。油页岩层干酪根13C相对富集, 具有相对较高的δ13CPDB值(-20.79‰~ -21.78‰), 与胜利河地区油页岩母源为较单一的藻类有关。藻类的大量繁殖造成了该类生物死亡埋藏速率远大于氧化速率, 在还原环境下大部分藻类还未被氧化就被埋藏, 从而保留了原始藻类略富13C的特征。胜利河油页岩的空间展布以及规模明显受古泻湖环境的控制。     

Delineation using geophysical data of the hydrocarbon bearing zone in the Begumganj structure, Hatia Trough, southern Bengal Basin, Bangladesh

The Begumganj structure of the Hatia Trough in Bengal Basin has proved it’s hydrocarbon potentiality. Several seismic sections have been analyzed to construct different maps and to interpret subsurface geology, structure and stratigraphy. These maps reveal that the Begumganj structure is an elongated to oval shaped asymmetrical anticline having the general trend NNW-SSE. No major faults affecting the structure could have been identified. Most of the reflectors are strongly affected by channels, especially at the western flank. Based on the analysis of seismic and available well data, the only gas bearing strata at depth of 2995 m (or TWT 2.02 seconds) has been identified. The structure is interpreted as a strati-structure entrapment because shale fill channel truncated this layer on western flank and at the crestal part of the anticline. The structure probably formed after the deposition of sediments. The channel has formed after the corresponding unit cut has been deposited. The channels eroding the reservoir unit range from Late Miocene to Early Pliocene age where the anticline probably begun to form during the Pliocene. Strong increase in amplitude (bright spot), possibly associated with hydrocarbon, has been apparent on seismic lines BG 9 and BG 10. The stratigraphic succession based on the information of the wells drilled on this structure and it’s surrounding fields reveals that the lithological sequences range from Miocene to Recent age where the only proven gas producing sand zone is located in the Bhuban Formation.