Eocene oil shales from Jordan – Paleoenvironmental implications from reworked microfossils

Reworked microfossils, common in Paleogene sediments in Jordan, are here used to reconstruct the depositional environment. The reworked taxa, which include both calcareous nannofossils and foraminifera of Cretaceous and Paleocene age, were found in Eocene oil shales. The potential provenance of the reworked material and the underlying processes of the reworking are discussed. We differentiate between a subaerial erosion of exposed hinterland strata and a submarine abrasion of sediments.A total of 73 smear slides have been prepared to identify calcareous nannofossils, another fifteen samples were analyzed for foraminifera. The allochthonous calcareous nannofossil and foraminifera taxa can be linked to a lithified source, which was eroded and transported with both calcitic lithic fragments and organic matter. Multiple factors controlling the transport of the reworked taxa during the time of deposition have been investigated for the Jordanian oil shales. Climate changes are thought to be the cause for changes in the abundance patterns and in the composition of the reworked taxa. The input of common autochthonous components during arid phases and more allochthonous sediment particles during humid periods filled the Eocene sink. A fall in relative sea level, perhaps in combination with increased storm activity, caused a transport of reworked material to deeper parts of the Azraq Hamza Sub-basin. The relative sea level changes in turn were related to syndepositional movements, redefining the shape of the Azraq Hamza Sub-basin and its internal fault-block architecture.     

Fabric dilatancy and the plasticity modeling of granular media

A novel conceptual model of the mechanics of sands is developed within an elastic–plastic framework. Central to this model is the realization that volume changes in anisotropic granular materials occur as a result of two fundamentally different mechanisms. The first is purely kinematic, dilative, and is the result of the changes in anisotropic fabric. There is also a second volume change in granular media that occurs as a direct response to changes in stress as in a standard elastic/plastic continuum. The inclusion of the two sources of volume change results in three important datum states. When subjected to isotropic strains, the resulting stress state in granular materials is not isotropic but lies upon the kinematic normal consolidation line. There exists a state at which the fabric‐induced volumetric strain rate becomes equal to the stress‐induced volumetric strain rate making the total plastic volumetric strain rate equal to zero. Granular response changes from contractive to dilative at this phase transformation line. The third datum state is the one in which the stress‐induced volumetric strain rate is zero. The sand, however, continues to dilate at this state with the difference between stress and dilation ratio a constant as predicted by Taylor's stress–dilatancy rule. These predictions are shown in accordance with experimental data from a series of drained tests and undrained on Ottawa sand. Copyright © 2011 John Wiley & Sons, Ltd.     

油企业抗震防灾规划信息管理系统的设计

基于石油企业抗震防灾工作对网络与数据库的信息管理系统的需求，对数据库产品进行了简要分析，并根据石油企业抗震防灾规划的需求和信息管理的一般模式，提出了石油企业抗震防灾规划信息计算机管理系统的设想。认为，以 Ｍｉｃｒｏｓｏｆｔ Ａｃｃｅｓｓ 数据库软件为基础，利用 Ｖ Ｂ或 Ｖ Ｃ等可视化前端应用开发工具，是目前比较好的方案，它将使石油企业抗震防灾规划工作在办公自动化方面迈向新的台阶     

对陕北地区石油储量计算中扩边问题的讨论

针对陕北地区油藏类型的特殊性,依据容积法计算模型,对控制储量计算中确定含油面积时的扩边问题进行了讨论,并提出了新的认识.     

Paleo-oil reservoir pyrolysis and gas release in the Yangtze Block imply an alternative mechanism for the Late Permian Crisis

The causes of the global mass extinction that occurred around the Permian–Triassic boundary have been widely studied through the geological record and in various locations. The results show that volcanic activity was a key factor in initiating the crisis during the Late Permian. Compared to other thermal events triggered by volcanic activity, pyrolysis of petroleum in Pre-Permian reservoirs has rarely been suggested as a significant source of the greenhouse gases that caused the mass extinction. In this study, geochemical analysis is carried out of a huge paleo-oil reservoir in the Yangtze Block (YB), South China. The detection of mineral inclusions and pyrobitumens is evidence of rapid pyrolysis of accumulated oil in the Ediacaran reservoir. New evidence from hydrothermal minerals and the presence of domain mesophase in the pyrobitumen suggest that the pyrolysis process occurred abruptly and that greenhouse gases were rapidly released through venting pipes. The dating of such a complex geological event in this old and deeply buried reservoir is inevitably difficult and potentially unreliable. However, cross-validation of the multiple evidence sources, including hydrothermal minerals and domain mesophase, indicates that the rapid oil pyrolysis must have been driven by a major thermal event. Reconstruction of burial and thermal histories suggests that the thermal event was most likely to have been triggered by the Emeishan Large Igneous Province (ELIP), which was in a period of significant volcanic activity during the Late Permian. Massive volumes of gases, including methane, carbon dioxide, and possibly hydrogen sulfide, were released, causing a significant increase in greenhouse gases that may have contributed to global warming and the resulting mass extinction during the Late Permian Crisis (LPC).     

油源断裂输导油气通道演化形式的研究方法及其应用

为了研究含油气盆地下生上储式油源断裂附近油气分布规律,在不同时期油源断裂输导油气通道及影响因素研究的基础上,通过确定油源断裂伴生裂缝可能发育部位和地层脆性发育部位,识别其活动期输导油气通道。通过断裂填充物泥质含量和填充物输导油气所需的最小泥质含量,识别其停止活动后输导油气通道,二者结合建立了一套油源断裂输导油气通道演化形式的研究方法,并将其应用于渤海湾盆地冀中坳馅廊固凹陷大柳泉地区旧州断裂在沙三中-下亚段内输导油气通道演化形式的研究中,结果表明:旧州断裂在沙三中-下亚段内共发育4种输导通道演化形式,其中一直输导通道演化形式仅分布在F;断裂东部局部和F;断裂的东部端部;先输导后不输导通道演化形式主要分布在F;断裂西部、F;断裂中西部及东部和F;断裂处;先不输导后输导通道演化形式主要分布在除东部局部的F;断裂、F;断裂的中东部;一直不输导通道演化形式主要分布在F;断裂中部、F;断裂和F;断裂交界处及F;断裂东部。一直输导和先输导后不输导通道演化形式分布处或附近应是沙三中-下亚段油气成藏的有利部位,与目前旧州断裂附近沙三中-下亚段已发现油气分布相吻合,表明该方法用于研究油源断裂输导油气通道演化形式是可行的。     

Experimental evaluation of shear strength behaviour of plastic and non-plastic silts

Silt is available in many parts of the world in combination with sands and clays. However, due to lack of clear understanding of its engineering behaviour, most of the time it is interpreted in terms of either sands or clays. Structures that are usually built on silty soils are designed to take into account design procedures developed for sandy or clayey soils. Presence of silts in combination with varying amount of sand and clays produces silt that is either plastic or non-plastic in nature. Silt is available in and around the Delhi region, in a majority mixture along with fine sands, which is non-plastic in nature. On the other hand silty deposits found in offshore Bombay High region are found in abundance along with significant amounts of clays and are termed as plastic silts. In this paper a comparison of the stress-strain behaviour of plastic and non-plastic silts is carried out under triaxial compression loading during both drained and undrained conditions. Two representative samples each from Delhi and Bombay High regions were considered for this comparison and results of stress-strain under four sets of confining pressure are discussed in detail. It is observed from this study that behaviour of silts is mainly dependent on the composition and structure of the resultant soil matrix. It is concluded from the results that shear strength parameters as well as volume change/pore pressure response of silty soils is dominated by the constituent soil present along with the silt. It is seen from the comparative behaviour of non-plastic and plastic silts that the presence of sand and clays has a governing effect on pore pressure development and the resultant friction angle. The study also corroborated that the nature of silt is transitional both in the case of plastic and non-plastic forms.     

Geochemistry of the Eocene Jijuntun Formation oil shale in the Fushun Basin,northeast China: Implications for source-area weathering,provenance and tectonic setting

Within the fault-bound Fushun Basin of northeastern China, the Eocene Jijuntun Formation hosts extensive deposits of thick lacustrine oil shale. Systematic sampling and geochemical analysis of these deposits has revealed that the parent rocks of the oil shale underwent moderate chemical weathering; and that its mineralogy and trace and rare earth element geochemistry were mainly controlled by parent rock composition, with no synsedimentary changes in the source terrain. Based on source rock and tectonic setting discrimination diagrams, we concluded that the parent rocks of the oil shale were mostly basalts of the Paleogene Laohutai Formation. These basalts originated in a continental back arc environment and contain abundant nutrient elements such as Fe, P, Ni, Cu and Zn, all of which are essential for the growth of aquatic photoautotrophs in lakes. Continuous, high primary productivity in the Jinjuntun lacustrine depocentre, combined with a stable tectonic setting and underfilled sedimentary environment, were key factors in the genesis of its oil shale.     

Enclave oil development and the rearticulation of citizenship in Turkana,Kenya: Exploring ‘crude citizenship’

Turkana County, located in the arid region of northwestern Kenya, has long been imagined as backwards and unproductive. As a result, successive governments have neglected to provide adequate social services and investments in the county, leaving Turkanas to rely on humanitarian organisations for access to rights and protections traditionally associated with citizenship. Yet when oil was discovered in Turkana in 2012, the county was thrust into the international spotlight. The oil exploration and development activities that followed the oil discovery have already begun to impact life in Turkana. Accordingly, this paper focuses on changing social and political relationships in light of emergent spaces of enclave oil development in Turkana. Our analysis draws from key informant interviews, focus group discussions, and field observations carried out in Kenya between October 2014 and May 2015. Specifically, we demonstrate that the Kenyan state’s historically hands-off approach to governing this region has led some Turkanas to seek recognition, legitimization, and fulfillment for their rights from oil companies, rather than the state. We argue that this is drawing oil companies and rural communities into an uneasy citizen-state-like relationship, altering the experiences and practices of citizenship in Turkana. We conclude that while the presence of oil companies in Turkana may benefit some, it also works to the detriment of others, introducing new forms of inequality and marginalization – a process we refer to as ‘crude citizenship’.     

Sources of polycyclic aromatic hydrocarbons (PAHs) to northwestern Saskatchewan lakes east of the Athabasca oil sands

The past several decades have witnessed a significant expansion of mining activities in the Athabasca oil sands region, raising concerns about their impact on the surrounding boreal forest ecosystem. To better understand the extent to which distal sites are impacted by oil sands-derived airborne contaminants, we examine sources of polycyclic aromatic hydrocarbons (PAHs) in surface sediments and dated sediment cores from Saskatchewan lakes situated ∼100–220 km east–northeast of the main area of bitumen mining activities. The concentrations and fluxes of both parent and alkylated PAHs are low and show considerable variability over the past 70–100 years. Small yet discernible increases in PAH concentrations and fluxes occurred over the past 30 years, a trend which coincides with the rapid growth in bitumen production. However, several lines of evidence point to wildfires as the principal source of PAHs to these lakes: (1) the significant co-variations in most cores between retene (1-methyl-7-isopropyl phenanthrene) and other groups of parent and alkylated PAHs, (2) the similarity in compound specific δ¹³C signatures of the parent PAHs phenanthrene and pyrene in recently deposited surficial sediments and those corresponding to time intervals considerably pre-dating the large scale development of the oil sands and (3) the discernible up-core increases in the proportion of refractory carbon (i.e., char) in Rock-Eval 6 data. The collective evidence points to softwood combustion from boreal forest fires as the principal source of retene in sediments and the general increase in forest fire activity in this region over the past several decades as the source of refractory carbon. Mining activities associated with the Athabasca oil sands are thus not considered a major source of PAHs to these lakes.