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1.
Compared to conventional reservoirs, pore structure and diagenetic alterations of unconventional tight sand oil reservoirs are highly heterogeneous. The Upper Triassic Yanchang Formation is a major tight-oil-bearing formation in the Ordos Basin, providing an opportunity to study the factors that control reservoir heterogeneity and the heterogeneity of oil accumulation in tight oil sandstones.The Chang 8 tight oil sandstone in the study area is comprised of fine-to medium-grained, moderately to well-sorted lithic arkose and feldspathic litharenite. The reservoir quality is extremely heterogeneous due to large heterogeneities in the depositional facies, pore structures and diagenetic alterations. Small throat size is believed to be responsible for the ultra-low permeability in tight oil reservoirs. Most reservoirs with good reservoir quality, larger pore-throat size, lower pore-throat radius ratio and well pore connectivity were deposited in high-energy environments, such as distributary channels and mouth bars. For a given depositional facies, reservoir quality varies with the bedding structures. Massive- or parallel-bedded sandstones are more favorable for the development of porosity and permeability sweet zones for oil charging and accumulation than cross-bedded sandstones.Authigenic chlorite rim cementation and dissolution of unstable detrital grains are two major diagenetic processes that preserve porosity and permeability sweet zones in oil-bearing intervals. Nevertheless, chlorite rims cannot effectively preserve porosity-permeability when the chlorite content is greater than a threshold value of 7%, and compaction played a minor role in porosity destruction in the situation. Intensive cementation of pore-lining chlorites significantly reduces reservoir permeability by obstructing the pore-throats and reducing their connectivity. Stratigraphically, sandstones within 1 m from adjacent sandstone-mudstone contacts are usually tightly cemented (carbonate cement > 10%) with low porosity and permeability (lower than 10% and 0.1 mD, respectively). The carbonate cement most likely originates from external sources, probably derived from the surrounding mudstone. Most late carbonate cements filled the previously dissolved intra-feldspar pores and the residual intergranular pores, and finally formed the tight reservoirs.The petrophysical properties significantly control the fluid flow capability and the oil charging/accumulation capability of the Chang 8 tight sandstones. Oil layers usually have oil saturation greater than 40%. A pore-throat radius of less than 0.4 μm is not effective for producible oil to flow, and the cut off of porosity and permeability for the net pay are 7% and 0.1 mD, respectively. 相似文献
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继尼雄、弗野、材玛等铁矿床的发现之后,新一轮1：5万区域地质调查又在班公湖-怒江成矿带西段乌鲁穷地区发现了较大规模的含铜磁铁矿矿床。野外路线调查、剖面实测和大比例尺填图表明,乌鲁穷磁铁矿形成于南羌塘南缘中-晚侏罗世中酸性岩体与上三叠统日干配错群二组（T3R2）碳酸盐岩外接触带中,矿体受后期近南北向高角度正断层改造,成矿作用表现出多期次、多阶段特征。通过对矿体邻近的石英闪长岩、二长花岗岩和控矿断层中同构造碳酸盐脉进行锆石LA-ICP-MS U-Pb同位素测年,获得石英闪长岩、二长花岗岩成岩年龄分别为：（161.3±0.72）Ma、（157.5±1.7）Ma,并获得同构造碳酸盐脉热液锆石年龄为（84.2±1.1）Ma。结合前人研究和1：5万地质调查成果,认为乌鲁穷含铜磁铁矿在中-晚侏罗世（157.5~161.3 Ma）班公湖-怒江洋北向俯冲过程中初步富集成矿,形成矽卡岩型含铜磁铁矿矿床,矿体在晚白垩世（84.2 Ma）陆内伸展过程中再次富集;提出班公湖地区在晚白垩世中期存在一期横跨缝合带的陆内伸展成矿事件,成矿作用与班公湖-怒江洋闭合后地幔软流圈底辟及其相关的地壳线性热隆伸展是一个机理关联的系统。 相似文献
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介绍了PNN方法原理及其算法训练学习过程,详细阐述了网络识别岩性参数的选取、岩性识别模型的建立过程.通过对比研究PNN与其他6种岩性识别方法,分析相同条件下预测结果,得到不同识别方法的优劣性.经研究发现,PNN概率神经网络方法在生产应用中效果更佳、训练识别用时最短.利用人工智能神经网络对测井数据进行自动解释分析,可满足随钻测井时效性及快速解释处理的地质导向需求. 相似文献
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断裂带的区域构造应力特征是研究其活动性的重要依据。在应变指示较少的地区,磁组构是研究区域构造应力的有效手段。在安徽1∶5万后山幅区域地质调查的基础上,对汤口断裂带进行系统的岩石磁组构特征研究。结果表明:该断裂带沉积地层的磁性矿物以磁铁矿为主,岩石磁化率椭球体以"扁球形"为主,显示其在原生沉积组构的基础上叠加了弱变形组构。磁化率椭球体的最大轴Kmax沿NEE-SWW向、最小轴Kmin沿NNWSEE向,反映汤口断裂带晚期受NNW-SEE向的挤压应力,兼较弱的NEE-SWW向拉张应力作用,说明喜山期汤口断裂带为近EW向正断拉张,兼具左行平移,时限为中新世—早更新世。 相似文献
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采用LA-ICP-MS法分析了塔里木北缘库鲁克塔格一带二长花岗岩锆石U-Pb年龄,获得该二长花岗岩岩体的年龄为(832.3±3.3)Ma(MSWD=2.8,n=24)。岩石地球化学特征显示,二长花岗岩属于准铝质高钾钙碱性系列,为I型花岗岩。微量元素富集大离子亲石元素(LILE)Ba、K、Sr、U等,亏损高场强元素(HFSE)Nb、Ta、Ti、P等;稀土元素总体含量较低(29.88×10-6~63.57×10-6),具有弱Eu正异常(δEu=0.87~1.39),整体配分模式与下地壳一致。结合区域地质背景对岩浆岩地球化学特征进行综合分析,认为二长花岗岩形成于岛弧环境。区域构造演化特征指示832 Ma该区洋壳已经开始俯冲,使得这一地区的地壳加厚,同时地幔柱的上涌加热作用导致古老地壳物质发生部分熔融而形成该期花岗岩。 相似文献
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The Qiongdongnan Basin is a strongly overpressured basin with the maximum pressure coefficient over 2.2. Two types of vertical overpressure configuration can be identified by electronic logs and mud pressure, based on the calibration with the test pressure. The first is a double overpressure configuration, in which the middle low overpressure zone divides the entire overpressure zone into two zones. The double overpressure configuration lies primarily in the western part of the basin. The second is a single overpressure configuration, in which overpressure increases with depth. The single overpressure configuration lies primarily in the eastern part of the basin. Distribution maps of the overpressure top and overpressure horizons show three important characteristics: (1) The distribution of the pressure coefficient is not uniform. There are many low overpressure zones against a background of high overpressure. (2) The pressure coefficient in the western area is greater than in the eastern area. The maximum pressure coefficient in the western area is greater than 2.2. (3) There is a low overpressure interval between the high overpressure zones in the western area. Based on the overpressure distribution, some important implications for hydrocarbon exploration can be drawn. In the Qiongdongnan Basin, it has been shown that normal pressure zones are favorable for hydrocarbon accumulation, and strongly overpressured zones (pressure coefficient greater than 1.8) are unfavorable for hydrocarbon accumulation. Accordingly, the NW low overpressure belt around wells R, Q and S should be beneficial for hydrocarbon accumulations, and should be considered as the next exploration play in the Qiongdongnan Basin. Theoretical hydrofracture calculation and interpretation of the sand injectites indicate the presence of widespread hydrofractures in the basin. Comparison between the sealing capacities of the double overpressure and single overpressure configurations shows that the former is superior for hydrocarbon accumulation and preservation. Because of the strong sealing capacity provided by the displacement pressure and pore pressure difference between the seal rock and reservoir in the double overpressure configuration zone, hydrocarbons barely penetrate the seal rock in the middle low overpressure zone. Therefore, the exploration interval should be within and below the middle low overpressure zone in the western basin. 相似文献
9.
The planning and management of water resources in the Shiyang River basin, China require a tool for assessing the impact of groundwater and stream use on water supply reliabilities and improving many environment‐related problems such as soil desertification induced by recent water‐related human activities. A coupled model, integrating rule‐based lumped surface water model and distributed three‐dimensional groundwater flow model, has been established to investigate surface water and groundwater management scenarios that may be designed to restore the deteriorated ecological environment of the downstream portion of the Shiyang River basin. More than 66% of the water level among 24 observation wells have simulation error less than 1·0 m. The overall trend of the temporal changes of simulated and observed surface runoff at the Caiqi gauging station remains almost the same. The calibration was considered satisfactory. Initial frameworks for water allocation, including agricultural water‐saving projects, water diversion within the basin and inter‐basin water transfer, reducing agricultural irrigation area and surface water use instead of groundwater exploitation at the downstream were figured out that would provide a rational use of water resources throughout the whole basin. Sixteen scenarios were modelled to find out the most appropriate management strategies. The results showed that in the two selected management options, the groundwater budget at the Minqin basin was about 1·4 × 108 m3/a and the ecological environment would be improved significantly, but the deficit existed at the Wuwei basin and the number was about 0·8 × 108 m3/a. Water demand for domestic, industry and urban green area would be met in the next 30 years, but the water shortage for meeting the demand of agricultural water use in the Shiyang River basin was about 2·2 × 108 m3/a. It is suggested that more inter‐basin water transfer should be required to obtain sustainable water resource use in the Shiyang River basin. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
10.
针对当前BDS-2/BDS-3组合定位性能,基于国际GNSS服务(IGS)跟踪站对BDS-2/BDS-3的组合定位实测数据,分析了北斗二号(BDS-2)不同类型卫星对北斗三号(BDS-3)卫星B1I、B3I与B1I/B3I双频组合伪距单点定位精度的影响. 经研究发现,BDS-2不同类型星座卫星都能有效改善BDS-3卫星可见数与卫星空间几何构型,地球静止轨道(GEO)卫星、倾斜地球同步轨道(IGSO)卫星、中圆地球轨道(MEO)卫星使BDS-3单频和双频伪距单点定位精度的提升在20%以内,而全部BDS-2卫星使BDS-3单频和双频伪距单点定位精度的提升在30%以内,整体提升关系为:BDS-2全部卫星>IGSO卫星>GEO卫星>MEO卫星. 相似文献