Geochemistry and origin of Ordovician oils in the Rewapu Block of the Halahatang Oilfield(NW China)

The oils in the Rewapu Block of the Halahatang Oilfield in the Tarim Basin(northwestern China) were geochemically analyzed by gas chromatography–mass spectrometry to investigate their origin and possible secondary alteration. The physical properties and chemical compositions of these Ordovician oils vary greatly, ranging from light to extremely heavy oils. All these oils belong to one single population and were derived from same source kitchen/bed. The differences in their chemical compositions and physical properties mainly result from secondary alteration of oils that were charged during the early phase of trap formation. The thickness of Upper Ordovician and Silurian caprocks of oil reservoirs in the Rewapu Block is higher than that in the north part of the Halahatang region, and therefore, significant biodegradation process is prevented. Compared to heavy oils in the north part, the Rewapu oils are dominated by light oils with no 25-norhopanes and no GC–MS ‘‘hump''(UCM: unresolved complex mixture) on the chromatographic baselines. The heavy oils in Wells RP7 and RP101 C were primarily influenced by water washing since apparent reduction of alkylated dibenzothiophenes was observed. The local geological background favored the water washing alteration. The reservoir geochemical study has practical application in hydrocarbon exploration and predicts the nature of oils in this oilfield.

Geochemical analysis of mixed oil in the Ordovician reservoir of the Halahatang Depression,Tarim Basin,China

In this study,12 crude oil samples were collected and analyzed from the Ordovician reservoir in the Halahatang Depression,Tarim Basin,China.Although the density of oil samples varies considerably,based on saturated hydrocarbon gas chromatographic(GC),saturated and aromatic hydrocarbon gas chromatographic-mass spectrometric(GC/MS) and stable carbon isotopic composition analyses,all the samples are interpreted to represent a single oil population with similar characteristics in a source bed or a source kitchen,organic facies and even in oil charge history.The co-existence of a full suite of n-alkanes and acyclic isoprenoids with UCM and 25-norhopanes in the crude oil samples indicates mixing of biodegraded oil with fresher non-biodegraded oil in the Ordovician reservoir.Moreover,according to the conversion diagram of double filling ratios for subsurface mixed crude oils,biodegraded/non-biodegraded oil ratios were determined as in the range from 58/42 to 4/96.Based on oil density and oil mix ratio,the oils can be divided into two groups:Group 1,with specific density>0.88(g/cm3) and oil mix ratio>1,occurring in the north of the Upper Ordovician Lianglitage and Sangtamu Formation pinchout lines,and Group 2,with specific density<0.88(g/cm3) and oil mix ratio<1,occurring in the south of the pinchout lines.Obviously,Group 2 oils with low densities and being dominated by non-biodegraded oils are better than Group 1 oils with respect to quality.It is suggested that more attention should be paid to the area in the south of the Upper Ordovician Lianglitage and Sangtamu Formation pinchout lines for further exploration.

Geochemical characteristics of Ordovician crude oils in the northwest of the Tahe oil field, Tarim Basin

Forty-six crude oil samples were selected from the Ordovician in the northwestern part of the Tahe oilfield for detailed molecular geochemical and isotopic analysis, including group compositions, carbonhydrogen isotopes and gas chroma-tograms of saturated hydrocarbons, as well as the characteristics of terpane, sterane and other biomarkers, indicating that crude oils are of the same origin from different districts in the Tahe oilfield and were derived from the same source kitchen (or oil source formation), i.e., mainly stemming from marine hydrocarbons. Detailed studies of oil physical properties of 25-honpane revealed that such oils have heavy or thick oil qualities due to biodegradation. Comprehensive assessment in terms of five maturity parameters shows that the oils from the Ordovician with Ro values varying from 0.80% to 1.59% are widely distributed in the northwest of the Tahe oilfield.

Large-scale Tazhong Ordovician Reef-flat Oil-Gas Field in the Tarim Basin of China

The Tazhong reef-fiat oil-gas field is the first large-scale Ordovician organic reef type oil-gas field found in China. Its organic reefs were developed in the early Late Ordovician Lianglitag Formation, and are the first large reefs of the coral-stromatoporoid hermatypic community found in China. The organic reefs and platform-margin grain banks constitute a reef-flat complex, mainly consisting of biolithites and grainstones. The biolithites can be classified into the framestone, baffiestone, bindstone etc. The main body of the complex lies around the wells from Tazhong-24 to Tazhong-82, trending northwest, with the thickness from 100 to 300 m, length about 220 km and width 5-10 km. It is a reef-flat lithologic hydrocarbon reservoir, with a very complex hydrocarbon distribution： being a gas condensate reservoir as a whole with local oil reservoirs. The hydrocarbon distribution is controlled by the reef complex, generally located in the upper 100-200 m part of the complex, and largely in a banded shape along the complex. On the profile, the reservoir shows a stratified feature, with an altitude difference of almost 2200 m from southeast to northwest. The petroleum accumulation is controlled by karst reservoir beds and the northeast strike-slip fault belt. The total geologic reserves had reached 297.667 Mt by 2007.

Variations in Stable Carbon Isotopic Composition of n-Alkanes from Ordovician- and Triassic-Derived Oils in Lunnan Oilfield, Tarim Basin, NW China: Global Paleoenvironmental Constraints

Molecular stable carbon isotope technique was employed to study well-sourced crude oils collected from a single drilling well and from the entire Lunnan oilfield, Tarim Basin, NW China. The stable carbon isotopic composition of n-alkanes from crude oils showed that Ordovician-derived oils are enriched in {}+{13}C and Triassic-derived oils are depleted in {}+{13}C. This is consistent with the distribution and evolution trend of stable carbon isotope ratios in crude oils/organic matter from all over the world in geological history (Stahl, 1977; Andrusevich et al., 1998). An extensive survey of literature indicates that, except for thermal maturity, organic matter input and depositional environment, paleoenvironmental background is another key factor that affects the stable carbon isotopic composition of Ordovician- and Triassic-derived crude oils. The results showed that gas chromatographic-isotope ratio mass spectrometry (GC-C-IRMS), combining with biogeochemical evolution of organic matter in geological history, may be a powerful tool in refining oil/oil, oil/source correlations in multi-age, multi-source petroliferous basins like Tarim.

鄂尔多斯盆地奥陶系盐下储层中固体沥青的发现及其对天然气成藏的启示

近期,鄂尔多斯盆地奥陶系盐下地层取得了天然气重大勘探突破和新进展,已成为天然气勘探的重点新领域。但是,该领域天然气成因、资源潜力等关键成藏问题尚不清楚。为此,以鄂尔多斯盆地中东部奥陶系马家沟组五段7亚段—马家沟组四段(以下简称马五7亚段—马四段)为研究对象,通过岩心与显微镜观察,发现盐下储层中存在固体沥青,并明确了沥青的产状和地球化学特征,最后结合天然气地球化学分析,探讨了盐下地层中天然气(以下简称盐下天然气)的成因和资源潜力。研究结果表明:(1)奥陶系盐下储层中存在大量固体沥青,透射光显微镜观察沥青呈花状、片状、团块状、薄膜状或条带状赋存于白云岩和石灰岩的孔、缝、缝合线和沥青包裹体内,固体沥青的质量百分数介于0.07%~0.55%(平均值为0.17%),等效镜质体反射率介于1.75%~1.97%,碳同位素值介于-28.4‰~-27.7‰;(2)盐下天然气干燥系数介于0.95~1.00,为典型的干气,天然气的甲烷、乙烷和丙烷碳同位素值分别介于-44.8‰~-32.4‰、-31.1‰~-22.6‰和-28.8‰~-19.7‰,具有甲烷碳同位素偏轻、乙烷与丙烷碳同位素偏重的异常特征;(3)奥陶系盐下储层中的固体沥青和天然气均为石油热裂解成因,石油来自于马家沟组或更古老的地层,石油裂解发生在早白垩世中—晚期;(4)盐下天然气遭受了不同程度的硫酸盐热化学还原作用的改造,其中乌审旗地区改造程度较强,天然气中H2S含量高,最高可达13.31%。结论认为,马五7亚段—马四段天然气预测储量约为1.00×1012 m3,该盆地奥陶系盐下天然气勘探潜力巨大。

Main progress and problems in research on Ordovician hydrocarbon accumulation in the Tarim Basin

The Tarim Basin is the largest petroliferous basin in the northwest of China, and is composed of a Paleozoic marine craton basin and a Meso-Cenozoic continental foreland basin. It is of great significance in exploration of Ordovician. In over 50 years of exploration, oil and gas totaling over 1.6 billion tonnes oil-equivalent has been discovered in the Ordovician carbonate formation. The accumulation mechanisms and distribution rules are quite complicated because of the burial depth more than 3,500 m, multi-source, and multi-stage accumulation, adjustment, reconstruction and re-enrichment in Ordovician. In this paper, we summarized four major advances in the hydrocarbon accumulation mechanisms of Ordovician carbonate reservoirs. First, oil came from Cambrian and Ordovician source rocks separately and as a mixture, while natural gas was mainly cracked gas generated from the Cambrian-Lower Ordovician crude oil. Second, most hydrocarbon migrated along unconformities and faults, with different directions in different regions. Third, hydrocarbon migration and accumulation had four periods： Caledonian, early Hercynian, late Hercynian and Himalayan, and the latter two were the most important for oil and gas exploration. Fourth, hydrocarbon accumulation and evolution can be generally divided into four stages： Caledonian （the period of hydrocarbon accumulation）, early Hercynian （the period of destruction）, late Hercynian （the period of hydrocarbon reconstruction and re-accumulation）, and Himalayan （the period of hydrocarbon adjustment and re-accumulation）. Source rocks （S）, combinations of reservoir-seal （C）, paleo-uplifts （M）, structure balance belt （B） matched in the same time （T） control the hydrocarbon accumulation and distribution in the Ordovician formations. Reservoir adjustment and reconstruction can be classified into two modes of physical adjustment and variation of chemical compositions and five mechanisms. These mechanisms are occurrence displacement, biodegradation, multi-source mixing, high-temperature cracking and late gas invasion. Late hydrocarbon accumulation effects controlled the distribution of current hydrocarbon. The T-BCMS model is a basic geological model to help understanding the control of reservoirs. At present, the main problems of hydrocarbon accumulation focus on two aspects, dynamic mechanisms of hydrocarbon accumulation and the quantitative models of oil-bearing in traps, which need further systemic research.

Ordovician Carbonate Reservoir Bed Characteristics and Reservoir-Forming Conditions in the Lungudong Region of the Tarim Basin

Basic characteristics of Ordovician carbonate reservoir beds in the Lungudong region of northeastern part of the Tarim Basin are described in detail and the reservoir-forming conditions of oil and gas are preliminarily discussed in this paper by collecting and sorting out a large amount of data. The carbonate reservoir beds are mainly developed in open-platform and platform marginal facies; the reservoir beds have large changes in and low average values of physical property; the main type is fractured reservoir beds with the fracture-porous type second. The reservoir bed development is chiefly controlled by the distribution of sedimentary facies, tectonic activity and karstification. Whereas the accumulation and distribution of hydrocarbons in the region are controlled by an advantageous structural location, a good reservoir-caprock combination and a favorable transporting system, with the distribution characterized by zones horizontally and belts vertically, the oil and gas are mainly concentrated in areas with structural uplift, densely developed fractures, and surface karst, a vertical vadose zone, and a horizontal undercurrent belt of palaeokarst.

Geological features and hydrocarbon accumulation in the Xinken oil field,Tarim Basin

Recently,a large-scale Ordovician oil and gas pool has been discovered in Xinken,north of the Tarim Basin,and it has strongly heterogeneous reservoirs and complicated fluid distribution.Through analyzing oil,gas and water samples collected from this area,in combination of field production and testing data,this study reveals that the Xinken oil pool contains dominantly normal oil characterized by low viscosity,low sulphur,and high wax.It has a low content of natural gas,which presents typical characteristics of wet gas and is oil-associated gas.Oil-gas correlation shows that the oil was from the Middle-Upper Ordovician source rocks and the charge and accumulation of oil and gas took place in the Late Hercynian Period.Controlled by paleogeomorphology,sedimentary facies,ancient karstification,faults,and other factors in the Caledonian Period,the Ordovician carbonate reservoirs are dominated by dissolved pores,cavities and fractures.The reservoir body of fractures and cavities is distributed in the shape of strip and laminate along faults and excellent reservoirs are mostly in the range of 70–100 m below the top of the Yijianfang Formation.As a whole,the Xinken oil pool is a fracture-cavity pool controlled by interbedded karst reservoirs and is a complex composed of stacked karst fractures and cavities of various sizes.It contains oil in large areas horizontally,which is quasi-laminated in distribution,and the accumulation of oil and gas is controlled by the distribution and development degree of the Ordovician carbonate reservoirs.The study shows that this area has abundant resources and a great exploration potential for oil and gas.

Oil-source correlation of the pre-Tertiary in the Huanghua Depression:Insights from stable carbon isotopes and molecular markers

Stable carbon isotopes were used together with molecular markers to constrain genetic relationships between sandstone extracts and potential source rocks in the pre-Tertiary in the Huanghua Depression,North China.Comparison of the extracts from Permo-Carboniferous terrigenous mudstones and Ordovician marine carbonates indicated that their prominent differences are in stable carbon isotopes,molecular markers and thermal maturity.Although the extracts of the Mesozoic and Lower Permian Xiashihezi Formation sandstones have some similar iso-topic characteristics,molecular markers data provide a good correlation between the Upper Jurassic-Lower Cretaceous oils and the Upper Carboniferous Taiyuan Formation mudstones,and between the Lower Permian Xiashihezi Formation oils and the Lower Permian mudstones.The results showed that the Upper Jurassic-Lower Cretaceous sandstone oils were derived chiefly from the Upper Carboniferous Taiyuan Formation terrigenous mudstones and that the Lower Permian Xiashihezi Formation oils were sourced from the Lower Permian Shanxi Formation and Xiashihezi Formation terrigenous mudstones.

Positive carbon isotope excursions:global correlation and genesis in the Middle-Upper Ordovician in the northern Tarim Basin,Northwest China

Stable carbon isotope ratio （δ13Ccarb） analysis has been widely applied to the study of the inter-conti- nental or global marine carbonate correlation. Large-scale Cambrian-Ordovician carbonate platforms were developed in the Tarim Basin. But research on fluctuation character- istics and global correlation of δ13Ccarb is still weak. Based on conodont biostratigraphy and whole-rock δ13Ccarb data in the Tahe oil-gas field of the northern Tarim Basin, the global correlation and genesis of positive carbon isotope excursions in the Darriwilian--Early Katian was exam- ined. Three positive excursions were identified in the Tahe oil-gas field including the middle Darriwilian carbon iso- tope excursion （MDICE）, the Guttenberg carbon isotope excursion （GICE）, and a positive excursion within the Pygodus anserinus conodont zone which is named the Early Sandbian carbon isotope excursion （ESICE） in this paper. Furthermore, these positive excursions had no direct relation with sea level fluctuations. MDICE and GICE could be globally correlated. The Middle-Upper Ordovi- cian Saergan Formation source rocks of the Kalpin outcrops were in accordance with the geological time of MDICE and ESICE. GICE had close relationship with the source rock of the Lianglitag Formation in the basin.Massive organic carbon burial was an important factor controlling the genesis of these positive excursions.

鄂尔多斯盆地中奥陶统乌拉力克组页岩油气富集条件及勘探方向

鄂尔多斯盆地油气资源丰富,常规油气与非常规油气并存,是中国油气重点勘探开发的含油气盆地之一。近年来,盆地中奥陶统乌拉力克组先后有多口探井获得工业油气流,展现出该盆地海相页岩油气良好的勘探开发新局面,研究其油气富集规律对于客观认识地质特征和指导下一步油气勘探具有重要意义。为此,基于岩心观察、铸体薄片、扫描电镜、核磁共振和有机地球化学分析等资料,系统分析了页岩烃源条件、储层特征及控藏因素,探讨了乌拉力克组海相页岩油气富集条件及勘探方向。研究结果表明:(1)与四川盆地下志留统龙马溪组页岩气藏相比,海相乌拉力克组页岩气藏具有“低丰度、低含气量、深埋藏、常压”的不足和“高硅质含量、高脆性指数”的优势;(2)乌拉力克组页岩总有机碳含量平均值为0.86%,含气量一般介于0.94~2.21 mL/g,埋深一般介于3 700~4 500 m,地层压力系数介于0.96~1.00,硅质矿物含量平均值为54.0%,脆性指数平均值为75.0%;(3)乌拉力克组页岩大面积含气、局部富集,具有“三元控藏”的特征,硅质页岩大规模发育是物质基础,良好的顶底板是必要条件,稳定的构造条件是页岩气富集的关键。结论认为,鄂尔多斯盆地海相乌拉力克组页岩油气发育4个勘探有利区,有利勘探面积为5 500 km^(2),其中马家滩、棋盘井地区为目前现实的页岩气勘探目标区。

塔里木盆地哈拉哈塘奥陶系缝洞型碳酸盐岩油田的勘探发现与评价探明

塔里木盆地塔北隆起哈拉哈塘油田发现于2009年,是塔里木盆地碳酸盐岩原油增储上产的重要领域。哈拉哈塘油田具有复杂的油气成藏过程与油气分布,地质认识、勘探指导思路历经多次转变,经历了碎屑岩、礁滩体、层间岩溶与断控岩溶等多种类型油气藏勘探阶段。通过油田的勘探历程与勘探开发生产资料的综合分析,认识到受断裂、岩溶和不整合面等多因素控制的缝洞型储层是油气赋存的主要场所,走滑断裂控制了油气的分布与富集,油田具有复杂的油气成藏与分布规律。哈拉哈塘油田的勘探实践表明:优越的石油地质条件是形成大油田的基础,地质认识的突破是发现复杂大油田的关键,物探技术进步是复杂油田勘探开发的保障,勘探开发一体化是碳酸盐岩快速增储上产的有效途径。该案例研究对国内外类似的缝洞型碳酸盐岩油田的勘探开发具有重要借鉴意义。

塔里木盆地顺北地区走滑断裂带压扭段和张扭段油气成藏实验模拟及成藏特征研究

近年来,塔里木盆地顺北地区在超深碳酸盐岩取得重要勘探突破,发现了断控缝洞型油气藏。该油气藏具有良好的生储盖组合,走滑断裂不同组合样式对油气运聚具有重要的影响和控制作用。本文选取顺北地区典型走滑断裂压扭段和张扭段开展解析,明确压扭段具有树枝状和树杈状两种断裂组合样式,张扭段具有非对称式和对称式两种组合样式,结合实钻油气藏的开发特征,建立实验模型,进行物理模拟实验,发现断裂带物性、断裂连接关系、供烃强度及缝网系统的发育是影响油气水分布的主要因素,压扭段直接相连主次断裂处于成藏优势区,可作为后期勘探开发的重点。建立了顺北地区压扭段和张扭段不同的油气成藏模式,对深化深部走滑断裂油气运移和成藏理论、指导顺北地区断控缝洞型油气藏的勘探具有重要意义。

塔里木盆地顺北油气田奥陶系断控缝洞型储层特征及成藏模式

顺北油气田为塔里木盆地重要的产油气区。根据钻井动态、岩心分析、测井、地震等资料,结合酸化压裂曲线及试井资料等对塔里木盆地顺北油气田奥陶系断控缝洞型储层的特征及成藏模式进行了研究。研究结果表明:①顺北油气田奥陶系断控缝洞型储层是伴随走滑断裂发育的一类特殊储层,垂直于断裂带发育,由基岩-裂缝带-洞穴带有序排列组成的多组缝洞集合体,洞穴带和裂缝带是其主要的储集空间,地震上的识别特征为断裂-串珠-杂乱强反射。②研究区规模较大的断控缝洞型储层的改造曲线具有初始泵压低、最大压降大,停泵压力低等特征,北东断裂体系的①号、④号、⑧号断裂带的钻井压力恢复曲线均呈“W”-箱形形态。③按照地震响应特征和试井压力恢复曲线形态可将研究区的断控缝洞型储层划分为洞穴型和裂缝型两大类,按试井压力恢复曲线形态可细分为裂缝-多洞穴型、裂缝-洞穴型、洞穴-裂缝型和裂缝型4类。④研究区断控缝洞型油气藏油源来自于玉尔吐斯组,沿走滑断裂运移,以孔洞和裂缝为储集空间,盖层为致密碳酸盐岩和巨厚泥岩。

鄂尔多斯盆地东部下奥陶统马家沟组盐下含气系统特征与勘探潜力

奥陶系下统马家沟组是鄂尔多斯盆地下古生界重要产气层位,目前已在马家沟组盐上风化壳领域获得了近万亿立方米的天然气地质储量,且盐上组合研究成果丰富,认识较为统一。但是,马家沟组盐下组合含气系统研究不足和认识分歧较大,已严重制约了该区盐下天然气的勘探。为此,从天然气地球化学特征出发,利用地质、地球物理和地球化学手段,对盐下含气系统进行了系统研究;结合盐下天然气来源、烃源岩规模和储层特征以及圈闭成藏要素评价,明确了马家沟组盐下天然气成藏的有利条件和富集区带。研究结果表明:(1)马家沟组盐下天然气的甲烷、乙烷碳同位素偏轻,具有典型油型气特征,其烃源岩可能为马家沟组高频层序相关的薄层海相烃源岩,岩性主要为暗色泥质白云岩和微生物白云岩,具备规模供烃能力;(2)盐下发育多套丘滩和丘坪粉晶白云岩储层,沿台内低隆规模分布,源储盖组合反映盐下具备自生自储成藏条件,疏导断层、侧向封堵是成藏关键要素;(3)榆林—横山和神木—米脂地区是盐下天然气有利富集区带。结论认为,马家沟组盐下含气系统和天然气富集区带新认识的提出有效地支撑了米探1井的天然气勘探突破,对鄂尔多斯盆地深层天然气深化勘探具有重要指导意义。

塔里木盆地顺北地区中下奥陶统流体改造与油气充注耦合关系

为明确顺北地区中下奥陶统流体改造与油气充注耦合关系,通过对方解石充填物进行阴极发光、流体包裹体显微镜下观察和油包裹体及其伴生盐水包裹体均一温度测试分析,结合方解石微区原位U-Pb同位素定年开展顺北地区中下奥陶统流体改造期次及序列、油气充注期次和时期及流体改造与油气充注耦合关系研究。结果表明:一间房组和鹰山组上段均经历多期流体改造,形成了具有不同阴极发光特征的多期方解石充填物,两者区别在于鹰山组地层未经历大气水改造;油包裹体荧光显示呈现蓝绿色-蓝白色,指示原油成熟度较高,且一间房组与油包裹体共生的盐水包裹体均一温度分布范围为84~98℃,平均均一温度为92.49℃和113~130℃,平均均一温度为119.91℃、鹰山组上段均一温度分布范围91.2~104℃,平均均一温度为96.1℃和112.7~128.1℃,平均均一温度为119.97℃,表明存在加里东晚期和海西晚期-印支期两期油气充注,主成藏期为海西晚期-印支期。烃类包裹体宿主矿物方解石微区原位U-Pb测试表明,其主要形成于加里东中晚期[(466.8±8)~(470.6±4.5)Ma],揭示油气充注发生在加里东晚期混源流体改造形成的具备红色-橙红色阴极发光特征方解石之后。

广域电磁法在豫西地区济源凹陷古生界油气勘探中的应用

豫西地区济源凹陷由山地和丘陵组成,地形条件复杂,地震资料品质较差,盆地内断裂形态结构、深部古生界展布特征等不清楚,制约着济源凹陷的油气勘探和资源潜力评价。本文利用广域电磁法在豫西地区济源凹陷进行方法应用研究,采用“地球物理资料综合处理解释一体化系统”进行数据处理与反演,获得了地下真实的电性特征,建立了目标层与视电阻率的电性关系,刻画了研究区目标层的构造特征。本研究查明了济源凹陷西部斜坡的断裂结构特征,新识别出12条断裂;揭示石炭-二叠系厚度分布范围在200~1800 m,最大埋深2200 m;奥陶系顶界面埋深分布在300~2450 m,呈“条带状”展布,得到了地质调查井岩心编录的证实。

饶阳凹陷赵皇庄-肃宁构造带奥陶系潜山勘探潜力简析

饶阳凹陷是冀中坳陷发现潜山最多、潜山油藏规模最大的富油凹陷,尽管经过多年的勘探,饶阳凹陷仍具有较大的勘探潜力。饶阳凹陷中部的赵皇庄-肃宁构造带潜山虽然勘探程度较高,但奥陶系潜山一直没有突破,具有较大的勘探潜力。由于该构造带的断裂系统复杂、钻井出露的潜山层位多,影响了奥陶系潜山地层的准确落实;而且钻入第三系沙三段地层的井较少,也给奥陶系潜山油源分析带来一定困难。为此采用了加强潜山层位对比及区域分布特征研究,推算该区奥陶系地层的厚度;以已知井进山层位为依据,重新精细梳理断层,加强潜山断裂结构研究,确定断槽内奥陶系层位的存在;加强下第三系沙三段暗色泥岩分析,寻找奥陶系潜山油气运移通道等方法。通过综合研究分析,构建该区奥陶系潜山的油藏模式,提出奥陶系潜山有利目标,明确了该区奥陶系潜山具有较大的勘探前景,从而为华北油田的增储上产奠定了坚实基础。

塔里木盆地奥陶系碳酸盐岩复杂油气藏的特性

油藏地质与开发地质综合分析表明,塔里木盆地奥陶系碳酸盐岩油气藏具有不同于常规油气藏的特性,具有油气分布的广泛性、油气性质的多样性、油气聚集的成层性与非均质性、油气产出的不稳定性等特性。储层强烈的非均质性、油气成藏与调整的多期性是形成油气藏特殊性的两大基本地质条件。塔里木盆地奥陶系大面积含油气、油气水分布复杂、少数高产稳产井支撑大部分产量的特殊碳酸盐岩油气藏具有普遍性,需要采取针对性的勘探开发一体化组织方式。