SHALLOW HYDROCARBON INDICATIONS ALONG THE ALPINE THRUST BELT AND ADJACENT FORELAND BASIN: DISTRIBUTION AND IMPLICATIONS FOR PETROLEUM EXPLORATION

Shallow oil and gas shows are common in the Alpine thrust front (including the Flysch Zone) and the North Alpine Foreland Basin in Switzerland, southern Germany and Austria, but have not hitherto been evaluated systematically. In the vertically‐drained Vienna Basin and the easternmost part of the Flysch Zone, shallow oil and gas shows and seeps often coincide with deeper‐lying hydrocarbon accumulations, and gas shows occur along major faults – for example within the urbanised area of the city of Vienna. The number of gas shows decreases in the Vienna Basin away from (to the south of) the subcrop of the main thermogenic source rock (the Upper Jurassic Mikulov Formation); however shallow accumulations of microbial gas occur in that area. To the west, along the northern margin of the laterally‐drained North Alpine Foreland Basin, oil shows have been recorded in both Austria and Switzerland; microbial gas shows are common in addition to thermogenic hydrocarbons. Typically the shows form regional clusters along river valleys and occur above shallow gas accumulations. A Lower Oligocene organic‐rich interval represents the main source of oil / condensate and thermogenic gas in the Upper Austrian part of the North Alpine Foreland Basin, whereas the composition of oil shows within the Calcareous Alps to the south indicates the presence of mature Mesozoic source rocks within the Alpine nappes. This implies the presence of an additional, as‐yet untested petroleum system. Thermogenic gas, occurring in Permo‐Triassic evaporitic rocks in the Calcareous Alps, as well as microbial gas in younger sediments, has frequently been encountered during salt mining and tunnelling activities. A surprising discrepancy has been found in different parts of the study area between the number of hydrocarbon shows and the number of economic fields. Whereas the number of fields and shows are approximately in proportion in the Vienna Basin and the Austrian sector of the North Alpine Foreland Basin, shows appear to be “under‐represented” in Germany. By contrast in Switzerland, despite a high number of shows especially in the North Alpine Foreland Basin and the Jura fold‐and‐thrust belt, no economic production has been established to date. Future exploration will show whether this is due to poor reservoir/trap quality, or if undiscovered resources are in fact present. The presence of oil shows generated from Mesozoic and Oligocene source rocks in the SW German and Swiss parts of the North Alpine Foreland Basin suggests the occurrence of multiple petroleum systems; these systems should be delineated in future studies. Few surface seeps have been recorded in less populated parts of the study area such as the high Alps, possibly due to sampling bias. However, this bias does not explain the low frequency of recorded hydrocarbon shows in the German part of the North Alpine Foreland Basin. This may be because the geological setting there is in general less favourable for the migration of thermogenic gas into shallow reservoirs and its preservation in shallow traps.     

库车前陆盆地含油气系统的地质特征

论述了库车含油气系统的地质特征:1具有一个生烃灶,发育有三叠系和侏罗系烃源岩,岩性为湖相泥岩、沼泽相煤系和高碳泥岩,干酪根为 ～ 1型;2具有低温度场、高压力场和强应力场,这种能量场导致了晚期运聚和事件成藏;3成藏组合包括三叠系-侏罗系烃源岩,侏罗系红色泥岩和下第三系-上第三系膏泥岩两套区域盖层和其它局部盖层,和三叠系-上第三系的砾岩、砂岩、粉砂岩和白云岩储层;4圈闭主要为坳陷区中新世以来形成的成排成带的断层相关褶皱和前缘隆起正断层下盘的断块;5由于强烈的构造运动,有早白垩世成油期和中新世末两个成气期,最重要的成藏期为中新世末(1.8Ma前);6有3种成藏模式,油藏、凝析气藏和气藏分布于三叠系-侏罗系的砂岩和砾岩储层、白垩系和下第三系的砂岩和粉砂岩以及白云岩储层。认为形成大油气田的关键因素有区域盖层、有效烃源岩的范围、疏导体系的连通性和圈闭的规模等。     

THE OLIGOCENE–MIOCENE MENILITE FORMATION IN THE UKRAINIAN CARPATHIANS: A WORLD‐CLASS SOURCE ROCK

This study investigates the hydrocarbon potential of Oligocene–Miocene shales in the Menilite Formation, the main source rock in the Ukrainian Carpathians. The study is based on the analysis of 233 samples collected from outcrops along the Chechva River in western Ukraine in order to analyse bulk parameters (TOC, Rock‐Eval), biomarkers and maceral composition. In Ukraine, the Menilite Formation is conventionally divided into Lower (Lower Oligocene), Middle (Upper Oligocene) and Upper (Lower Miocene) Members. The Early Oligocene and Early Miocene ages of the lower and upper members are confirmed by new nannoplankton data. The Lower Menilite Member is approximately 330 m thick in the study area and contains numerous chert beds and turbidite sandstones in its lower part together with organic‐rich black shales. The shales have a high content of silica which was probably derived from siliceous micro‐organisms. The TOC content of the shales frequently exceeds 20 wt.% and averages 9.76 wt.%. HI values range between 600 and 300 mgHC/gTOC (max. 800 mgHC/gTOC). The Middle Member contains thin black shale intervals but was not studied in detail. The Upper Member is about 1300 m thick in the study area and is composed mainly of organic‐rich shales. Chert layers are present near the base of the Member, and a prominent tuff horizon in the upper part represents a volcanic phase during shale deposition. The member grades into overlying molasse sediments. The average TOC content of the Upper Menilite succession is 5.17 wt.% but exceeds 20 wt.% near its base. Low T_max and vitrinite reflectance measurements for the Lower (419°C and 0.24–0.34 %R_r, respectively) and Upper (425°C and 0.26–0.32 %R_r, respectively) Menilite Member successions indicate thermal immaturity. Biomarker and maceral data suggest a dominantly marine (Type II) organic matter input mixed with varying amounts of land‐plant derived material, and indicate varying redox and salinity conditions during deposition. Determination of the Source Potential Index (SPI) shows that the Menilite Formation in the study area has the potential to generate up to 74.5 tons of hydrocarbons per m². The Chechva River outcrops therefore appear to have a significantly higher generation potential than other source rocks in the Paratethys realm. These very high SPI values for the Menilite Formation may explain why a relatively small area in Ukraine hosts about 70% of the known hydrocarbon reserves in the northern and eastern Carpathian fold‐thrust belt.     

塔里木前陆盆地构造特征及油气分布

塔里木中新生代前陆盆地十分发育,油气资源潜力大,目前已发现10多个油气田,前景广阔。它的演化经历了早期前陆、晚期前陆及陆内统一盆地等3个阶段;按其动力学性质又可划分为单前陆、双前陆及走滑前陆等盆地;它的构造变形十分复杂,盆地构造样式为压性逆冲断裂;在平面上可划分为逆掩带、断褶带、坳陷带及斜坡带;其油气主要分布在断褶和斜坡带中。     

中国中西部前陆盆地的油气勘探

典型前陆盆地具有双层结构，即前陆盆地发育前的被动陆缘沉积和前陆盆地本身的沉积建造。中国的前陆盆地独具特色，在分类上大多应归于类有前陆盆地。按照发育的时代，中国中西部的前陆盆地可划分为３个世代，中生代产陆盆地的油气是最为现实折勘探目标。     

江汉盆地潜江期盐湖沉积石油的形成与演化

本文论述了江汉盆地潜江期盐湖沉积石油形成的地质环境和地球化学特征,探讨了盐湖相生油岩干酪根和烃类的演化规律,提出正烷烃由未成熟的高偶碳优势演变到成熟的偶奇相当,即OEP值由0.39演变到近于1;地温梯度较低,导致有机质的演化速率较慢,各演化界限较深。这是盐湖相生油岩烃类演化的二个特点。     

THE DISTRIBUTION OF OIL-AND GASFIELDS IN RELATION TO SATELLITE IMAGE INTERPRETATION: AN EXAMPLE FROM THE POLISH EAST CARPATHIANS AND THE ADJACENT FOREDEEP

The Polish East Carpathians consist of a series of nappes which have been thrust northwards onto the Miocene sedimentary fill of the Carpathian Foredeep, a foreland basin located between the Meta-Carpathian Swell to the north and the Carpathian orogen to the south. A total of 151 oil- and gasfields are present in the Polish Carpathians and the adjacent foredeep.
In the Carpathians, all the oilfields are related to structural traps such as anticlinal folds which are frequently cut by faults, thrusts and décollement planes. In the Carpathian Foredeep, oil and gas accumulations are located both within the Neogene interval and in the pre-Neogene basement. The most productive fields occur on the northern and southern margins of the Carpathian Foredeep; these locations received sandy detritus from the developing orogen to the south, and from the Meta-Carpathian ridge to the north.
In this paper, we compare the distribution of oil- and gasfields in the Polish Carpathians and the foreland basin to that of structural lineaments identified on Landsat imagery. Within the Carpathians, the lineaments are connected with fold axes, nappes, thrust slices and faults. In the Carpathian foredeep, by contrast, the lineaments must also be associated with faults, but no faults are indicated on surface geological maps. The simplest way to distinguish the faults is to interpret their presence in the pre-Tertiary basement, and to project them into the Miocene cover.
A satellite image of the study area was analysed independently by 40 different researchers, and the resulting interpretations were collated. With reference to this summary interpretation, we have attempted to analyse the spatial relationship between major lineaments and the distribution of oil- and gasfields in the study area.     

川西坳陷中段晚三叠世前陆盆地构造变形与油气勘探

由于龙门山地区会聚构造运动,地表露头与地下地震资料揭示了川西晚三叠世前陆盆地被卷入板内形变的构造地质现象。鉴于这一地区已经证实晚三叠世地层中富含油气,该文以获得的实际资料对晚三叠世前陆盆地形变年代、形变特征、形变运动(动力)学机制进行了深入分析,并着重分析了构造形变与油气成藏的关系。针对区内前陆盆地形变后所形成的3种不同类型(磁峰场、鸭子河、马井)的含气构造,文中讨论了其成藏的主控因素,并据此提出了该地区这一领域的油气勘探方向。     

酒东盆地营尔凹陷油气生成和运移聚集

酒东盆地营尔凹陷存在下白垩统和中、下侏罗统２套生油层。其中，下白垩统中沟组下段有机质丰度类型最好，但尚处于低熟阶段；成熟的、中、下株罗统是极重要的生油层。营尔凹陷内，２套生油层生物标志物分布截然不同；下白垩统和中、下侏罗统的原油是２类自生自储原油；３个异常高压流体带严格控制油气的纵向运移聚集。     

黄骅坳陷早第三纪介形类化石组合序列与油气生成

黄骅坳陷早第三纪介形类化石丰富、含8个组合、5个亚组合和1个化石分布段.其中,含化石属种和个体数量丰富的组合与油气生成,特别是与生油岩类型有密切关系.