准噶尔腹部火山岩风化壳储层特征及其影响因素

文章通过大量岩芯、铸体薄片观察和测井资料分析,对准噶尔腹部石西石炭系火山岩风化壳储层进行了详细地研究。研究结果表明,该火山岩风化壳储层的储集空间主要有基质溶孔、气孔或杏仁体溶孔、角砾间溶孔、微裂缝和裂缝等,其中与裂缝连通的各类溶孔占主导地位;在岩石分布上以集块岩、条带状熔岩、角砾熔岩和致密凝灰岩为主,玄武岩、安山岩和流纹岩则相对较少;储层物性主要表现为高孔低渗,只有裂缝具有较高的渗透率,且裂缝以高角度缝和直立缝为主。研究还发现,岩性岩相、裂缝和风化淋滤作用是影响该风化壳储层的主要因素。区内油层主要聚中在构造高部位、靠近断裂带和有利岩相区域;油层分布在离石炭系风化壳顶面25~150 m的范围内。     

Sinian-Cambrian Tectonic Framework in the Tarim Basin and its Influences on the Paleogeography of the Early CambrianEI北大核心CSCD

Due to strong remodification and sparse trace remnants, tectonic restoration is critical for the reconstructing of the paleography and basin-prototype in the multiple-cycles superimposed basin, which is also fundamental for the hydrocarbon exploration of the deep marine carbonate in the Tarim Basin. This study presents the tectonic framework of the transition phase from the Sinian to the Cambrian Period and its constrains on the paleography of the Cambrian in the Tarim Basin based on comprehensive analysis of new geochronology data, seismic data and regional tectonic data. The results showed that (1) there is a large regional unconformity between the Cambrian and Precambrian, suggesting a discontinuous deposition from the Sinian to the Cambrian that is contrary to the major view; (2) a broad flattened paleotopography formed before Cambrian Period, which is favorable for the wide epicontinental sea environment and a gentle homoclinal ramp platform development in the early Cambrian, and the residual basement low relief uplifts that influence the microfacies differentiation in the carbonate platform; (3) the Cambrian carbonate platform has been involved much into the marginal orogenic belts, and the proto-platform is probably of 200 km out of the present basin in S-N direction; (4) there is a weak extensional setting in the Cambrian-Early Ordovician rather than a strong rifting setting with a large aulacogen into the platform, in which a inter-platform shallow depression and stable ramp platform developed in the Cambrian; (5) there is not troughs, but rather low relief uplifts developed in the Early Cambrian in the southwestern Tarim Basin, and lack of large uplifts along the carbonate platform margins; (6) it is showed a broad architecture of platform-wide slope-ocean basin from the inner Tarim plate to its margin in the Cambrian Period. Considering the basin prototype, the restoration of the tectono-paleography in the early Cambrian in the Tarim Basin is distinct from those of the previously proposed. We propose that a gentle pattern with “two platforms and one inter-depression” in E-W striking other than multiple small platform constrained in the basin, and further subdivision of the western platform with inner platform low uplift and sag in N-S striking, which is possibly inherited from the basement architecture. On the outer of the united platform, there is probably broad gentle slope for transition to ocean basin. We therefore argue that tectonic restoration is crucial for reconstruction of the paleogeography and basin prototype, especially for basins experienced multiphase of tectonic cycles. © 2018, Science Press. All right reserved.     

Water Cycle Analysis of Social and Economic System in Tarim River Basin

Water cycle includes natural water circulation and social economic system water cycle. The concept of virtual water provides a new method and means for studying social water circulation. This paper is based on the theory of water circulation in social and economic system, using input-output analysis method quantitatively describes the Tarim River basin of social water cycle paths and analysis of water resources management in Tarim River basin sustainable development process of the key issues. The results show that the main sectors of virtual water export in the Tarim River Basin are agriculture, petroleum, natural gas and food industry. Agricultural water accounts for more than 98% of total water consumption, most of which is transferred to the food and textile industries, and the food industry export water from the agricultural sector. Shandong Province is the largest virtual water transport area in the Tarim River Basin. The main sector of virtual water input in the Tarim River Basin is the metallurgical industry. Finally, in view of the problems arising from the inter-industrial and inter-regional social water circulation in the Tarim River basin, the paper puts forward the ways and strategies of regulating agricultural and industrial water use in the Tarim River Basin.     

Subsidence in the Kathmandu Basin,before and after the 2015 Mw 7.8 Gorkha Earthquake,Nepal Revealed from Small Baseline Subset-DInSAR Analysis

Land subsidence in densely urbanized areas is a global problem that is primarily caused by excessive groundwater withdrawal. The Kathmandu Basin is one such area where subsidence due to groundwater depletion has been a major problem in recent years. Moreover, on 25 April 2015, this basin experienced large crustal movements caused by the Gorkha earthquake (Mw 7.8). Consequently, the effects of earthquake-induced deformation could affect the temporal and spatial nature of anthropogenic subsidence in the basin. However, this effect has not yet been fully studied. In this paper, we applied the SBAS-DInSAR technique to estimate the spatiotemporal displacement of land subsidence in the Kathmandu Basin before and after the Gorkha earthquake, using 16 ALOS-1 Phased Array L-band Synthetic Aperture Radar (PALSAR) images during the pre-seismic period and 26 Sentinel-1 A/B SAR images during the pre- and post-seismic periods. The results showed that the mean subsidence rate in the central part of the basin was about ?8.2 cm/year before the earthquake. The spatial extents of the subsiding areas were well-correlated with the spatial distributions of the compressible clay layers in the basin. We infer from time-series InSAR analysis that subsidence in the Kathmandu basin could be associated with fluvio-lacustrine (clay) deposits and local hydrogeological conditions. However, after the mainshock, the subsidence rate significantly increased to ?15 and ?12 cm/year during early post-seismic (108 days) and post-seismic (2015–2016) period, respectively. Based on a spatial analysis of the subsidence rate map, the entire basin uplifted during the co-seismic period has started to subside and become stable during the early-post-seismic period. This is because of the elastic rebound of co-seismic deformation. However, interestingly, the localized areas show increased subsidence rates during both the early-post- and post-seismic periods. Therefore, we believe that the large co-seismic deformation experienced in this basin might induce the local subsidence to increase in rate, caused by oscillations of the water table level in the clay layer.     

四川盆地下古生界硅质页岩层系中硅质来源及其对有机质保存的影响初探

四川盆地下古生界两套硅质页岩层系是其重要的页岩气产层,五峰组—龙马溪组硅质含量与TOC及含气量呈正相关性,暗示硅质矿物对该地区页岩气的生成具有重要意义。但硅质来源复杂,且存在后期硅质流体的注入。因此,本文在总结前人的研究成果基础上,对四川盆地寒武系底部硅质岩系与五峰组—龙马溪组硅质岩系的硅质特征进行了详细的岩石学分析,揭示了3种硅质来源特征：①同沉积无机硅质流体;②生物硅;③后期无机硅质流体。其中寒武系底部以同沉积无机硅质流体与生物硅来源为主,同沉积硅质流体导致有机质快速石化埋藏,有机质内部结构及形态保存较好;五峰组—龙马溪组硅质来源以后期无机硅质流体与生物硅来源为主,有机质在保存过程中受硅质流体的影响很小,有机质腐泥化作用充分,内部结构和形态多数保存较差。该研究初步揭示了两套页岩层系的硅质发育岩石学特征,及其对有机质保存的影响,期望能为四川盆地两套页岩气储层差异性提供新的思路与基础地质数据。     

Sedimentology of the continental end‐Permian extinction event in the Sydney Basin,eastern Australia

Upper Permian to Lower Triassic coastal plain successions of the Sydney Basin in eastern Australia have been investigated in outcrop and continuous drillcores. The purpose of the investigation is to provide an assessment of palaeoenvironmental change at high southern palaeolatitudes in a continental margin context for the late Permian (Lopingian), across the end‐Permian Extinction interval, and into the Early Triassic. These basins were affected by explosive volcanic eruptions during the late Permian and, to a much lesser extent, during the Early Triassic, allowing high‐resolution age determination on the numerous tuff horizons. Palaeobotanical and radiogenic isotope data indicate that the end‐Permian Extinction occurs at the top of the uppermost coal bed, and the Permo‐Triassic boundary either within an immediately overlying mudrock succession or within a succeeding channel sandstone body, depending on locality due to lateral variation. Late Permian depositional environments were initially (during the Wuchiapingian) shallow marine and deltaic, but coastal plain fluvial environments with extensive coal‐forming mires became progressively established during the early late Permian, reflected in numerous preserved coal seams. The fluvial style of coastal plain channel deposits varies geographically. However, apart from the loss of peat‐forming mires, no significant long‐term change in depositional style (grain size, sediment‐body architecture, or sediment dispersal direction) was noted across the end‐Permian Extinction (pinpointed by turnover of the palaeoflora). There is no evidence for immediate aridification across the boundary despite a loss of coal from these successions. Rather, the end‐Permian Extinction marks the base of a long‐term, progressive trend towards better‐drained alluvial conditions into the Early Triassic. Indeed, the floral turnover was immediately followed by a flooding event in basinal depocentres, following which fluvial systems similar to those active prior to the end‐Permian Extinction were re‐established. The age of the floral extinction is constrained to 252.54 ± 0.08 to 252.10 ± 0.06 Ma by a suite of new Chemical Abrasion Isotope Dilution Thermal Ionization Mass Spectrometry U‐Pb ages on zircon grains. Another new age indicates that the return to fluvial sedimentation similar to that before the end‐Permian Extinction occurred in the basal Triassic (prior to 251.51 ± 0.14 Ma). The character of the surface separating coal‐bearing pre‐end‐Permian Extinction from coal‐barren post‐end‐Permian Extinction strata varies across the basins. In basin‐central locations, the contact varies from disconformable, where a fluvial channel body has cut down to the level of the top coal, to conformable where the top coal is overlain by mudrocks and interbedded sandstone–siltstone facies. In basin‐marginal locations, however, the contact is a pronounced erosional disconformity with coarse‐grained alluvial facies overlying older Permian rocks. There is no evidence that the contact is everywhere a disconformity or unconformity.     

渤海湾盆地南堡凹陷南部深层沙一段优质碎屑岩储层特征及成因机制

利用岩芯、薄片、扫描电镜和分析化验等资料,对南堡凹陷南部深层古近系沙一段（沙河街组一段）优质碎屑岩储层特征进行了分析并揭示其成因机制。研究表明：①南堡凹陷南部沙一段优质碎屑岩储层属于低孔中渗储层,发育原生孔隙、次生孔隙和微裂缝;②沙一段沉积期处于强水动力沉积环境,辫状河三角洲前缘水下分流河道砂体普遍发育,岩性主要为中粗砂岩、含砾砂岩和砂砾岩等粗岩性,岩石类型主要为岩屑长石砂岩,石英、岩浆岩岩屑等刚性组分含量高,储层在强压实作用下仍保留了局部原生残余粒间孔,部分刚性组分强压条件下形成微裂缝;③沙一段与东三段为区域不整合接触,大气水的酸性流体在成岩初期以及烃源岩成熟之后产生的有机酸在成岩后期通过油源断裂和不整合面进入储层,造成长石、易溶碎屑等组分溶蚀形成次生孔隙,溶蚀作用不仅增加孔隙空间,而且扩大喉道宽度。结论认为：粗岩性和高刚性颗粒含量为原生孔隙的保存提供了物质基础;油源断层、不整合面为酸性流体的进入提供路径,促进了次生孔隙发育。     

陇中盆地及周边地区主夷平面演化与高原隆升

陇中盆地及周边地区是青藏高原向北东方向扩展的最前缘部位,其地貌演化过程的研究对于深入理解高原的隆升与扩展过程具有重要意义。鉴于夷平面在探讨高原隆升年代、幅度和过程方面的可靠性,首先总结陇中盆地及周边地区夷平面相关研究的前期成果,并结合最新年代数据,确定了不同区域主夷平面的发育和解体年代;再利用古河道拟合等方法定量评估了相关夷平面的隆升量;最后探讨了主夷平面的性质及其隆升过程。研究发现,陇中盆地及周边的地区的高海拔低起伏地貌面是被抬高的先存夷平面;不同区域主夷平面的发育与解体时间整体同步,它们自晚渐新世开始发育,并于晚中新世8~6 Ma左右解体;模拟结果表明,美武高原主夷平面自晚中新世以来相对陇中盆地隆升了约1 400~1 600 m,并且早更新世以来的隆升速率明显大于晚中新世-早更新世时期。     

浅水三角洲沉积体系与储层岩石学特征

浅水三角洲已经成为当前沉积学研究和油气勘探的重点领域,浅水三角洲常规和非常规砂岩储层中发现了丰富的油气资源。鄂尔多斯盆地中—古生界发育大型浅水三角洲沉积,结合岩芯、测井、分析化验等资料,对盆地西部地区山1—盒8段浅水三角洲的母岩特征、沉积充填、砂体展布与储层岩石学特征进行研究,为研究区常规砂岩储层和致密砂岩油气勘探提供地质依据。分析表明,研究区南部和北部砂岩重矿物组合相似,以锆石和白钛矿为主。综合La/Yb-REE与Dickinson三角图解、稀土元素配分模式和碎屑锆石定年分析认为,北部物源主要来自盆地西北部阿拉善古陆太古界和元古界花岗岩、片麻岩、石英砂岩,向南影响到陇东地区北部;南部物源主要来自盆地南部北秦岭地区太古界、元古界花岗岩、片麻岩和片岩,向北影响陇东地区中南部。山1段发育曲流河三角洲,盒8段发育辫状河三角洲,孤立型与垂向叠置型水下分支河道砂体是主要的砂体类型。盒8段沉积时期,古湖泊可能萎缩;南北物源形成的三角洲在研究区中部环县东南一带交汇混合。砂岩类型主要为岩屑质石英砂岩、石英砂岩和岩屑砂岩,结构成熟度中等—较差。砂岩成岩改造强烈,水—岩反应复杂,压实作用是储层致密化的主因,多期胶结作用使砂岩的孔喉结构变得十分复杂。孔隙类型以微米—纳米级的岩屑溶蚀孔、剩余粒间孔和高岭石晶间孔为主,整体上属于非常规致密砂岩储层。砂体分布与“甜点”预测是研究区致密油气勘探的关键。