鄂尔多斯盆地及周缘地区中二叠统沉积特征*

鄂尔多斯盆地及周缘地区上古生界天然气资源丰富,中二叠统石盒子组是主力勘探层位,明确其沉积相及沉积特征对于该区油气勘探具有重要的意义。在野外剖面踏勘及钻井岩心观察的基础上,对研究区石盒子组地层及岩性特征、沉积相类型及沉积演化等进行系统分析。结果表明: 研究区中二叠统石盒子组主要发育粗粒陆源碎屑岩系。中二叠世研究区仍存在间歇性局部海侵,石盒子组主要以陆相沉积体系为主,包含冲积扇沉积相、河流沉积相、湖泊沉积相、三角洲沉积相等,同时发育障壁海岸沉积体系。研究区自北向南石盒子组依次发育冲积扇、河流、三角洲、滨浅湖等沉积,南缘、西南缘发育浅水三角洲沉积,南缘、东南缘障壁海湾中发育潟湖和障壁沙坝沉积。     

Geochronological Records of Oil-Gas Accumulations in the Permian Reservoirs of the Northeastern Ordos Basin

Geochronology of oil-gas accumulation （OGA） is a challenging subject of petroleum geology in multi-cycle superimposed basins.By K-Ar dating of authigenic illite （AI） and fluid inclusion （FI） analysis combined with apatite fission track （AFT） thermal modeling,a case study of constraining the OGA times of the Permian reservoirs in northeast Ordos basin （NOB） has been conducted in this paper.AI dating of the Permian oil-gas-bearing sandstone core-samples shows a wide time domain of 178-108 Ma.The distribution of the AI ages presents 2-stage primary OGA processes in the Permian reservoirs,which developed in the time domains of 175-155 Ma and 145-115 Ma with 2-peak ages of 165 Ma and 130 Ma,respectively.The FI temperature peaks of the samples and their projected ages on the AFT thermal path not only present two groups with a low and a high peak temperatures in ranges of 90-78℃ and 125-118℃,respectively corresponding to 2-stage primary OGA processes of 162-153 Ma and 140-128 Ma in the Permian reservoirs,but also appear a medium temperature group with the peak of 98℃ in agreement with a secondary OGA process of c.～30 Ma in the Upper Permian reservoirs.The integrated analysis of the AI and FI ages and the tectono-thermal evolution reveals that the Permian reservoirs in the NOB experienced at least 2-stage primary OGA processes of 165-153 Ma and 140-128 Ma in agreement with the subsidence thermal process of the Mid-Early Jurassic and the tectono-thermal event of the Early Cretaceous.Then,the Upper Permian reservoirs further experienced at least 1-stage secondary OGA process of c.～30 Ma in coincidence with a critical tectonic conversion between the slow and the rapid uplift processes from the Late Cretaceous to Neogene.     

东北亚跃进山拼贴带及邻域岩石圈结构特征的地电学证据

为进一步查清东北亚完达山地体与两侧的佳木斯地块、兴凯地块间接触关系以及对跃进山拼贴带域沉积盆地油气条件的控制作用,布设5条MT剖面,计长1104 km.结果显示:(1)研究区地电学结构主要特征为佳木斯地块从中部向南北两方向,这一稳定地块的“高阻核”减薄,兴凯地块的高阻块体自东而西逐渐加深增厚,完达山地体在南部具有较多的高阻块体,向北渐少.(2)完达山地体西南端呈一“牛角”形状范围把佳木斯地块和兴凯地块分开;与原认识的完达山地体、佳木斯地块在同江-宝清-当壁一带贴合的位置相比,从宝清开始向南移至麻山-桦林一带.(3)完达山地体构造成因包括两部分,一是俯冲引起的拼贴,二是软流圈物质的热上涌;佳木斯地块内所存在的“高阻核”边界可能是该地块东界.(4)4个沉积盆地除勃利盆地外,另外3个盆地的基底间或存在规模不大的高阻块,大多范围分布着高导带,对盆地的成烃环境是有利的.     

The distribution rule and seepage effect of the fractures in the ultra-low permeability sandstone reservoir in east Gansu Province,Ordos Basin

To study the impact of the fractures on development in the ultra-low permeability sandstone reservoir of the Yangchang Formation of the Upper Triassic in the Ordos Basin,data on outcrops,cores,slices,well logging and experiments are utilized to analyze the cause of the formation of the fractures,their distribution rules and the control factors and discuss the seepage flow effect of the fractures. In the studied area developed chiefly high-angle tectonic fractures and horizontal bedding fractures,inter-granular fractures and grain boundary fractures as well. Grain boundary fractures and intragranular fractures serve as vital channels linking intragranular pores and intergranular solution pores in the reservoir matrix,thus providing a good connectivity between the pores in the ultra-low perme-ability sandstone reservoir. The formation of fractures and their distribution are influenced by such external and internal factors as the palaeo-tectonic stress field,the reservoir lithological character,the thickness of the rock layer and the anisotropy of a layer. The present-day stress field influences the preservative state of fractures and their seepage flow effect. Under the tec-tonic effect of both the Yanshan and Himalayan periods,in this region four sets of fractures are distributed,respectively assuming the NE-SW,NW-SE,nearly E-W and nearly S-N orientations,but,due to the effect of the rock anisotropy of the rock formation,in some part of it two groups of nearly orthogonal fractures are chiefly distributed. Under the effect of the present-day stress field,the fractures that assume the NE-SW direction have a good connectivity,big apertures,a high permeability and a minimum starting pressure,all of which are main advantages of the seepage fractures in this region. With the development of oilfields,the permeability of the fractures of dif-ferent directions will have a dynamic change.     

Study on the Characteristics of Seismic Activity in the Interior of the Ordos Block

The temporal and spatial distribution characteristics of earthquakes in the Ordos block are studied by using historical earthquake data,instrument data of the regional seismic network around the Ordos block and the historical felt earthquake data,and the relationship between seismicity in the Ordos block and seismicity around the Ordos block is discussed. The result shows that the Ordos block is a typical moderate-strong earthquake active region where many M_S≥5.0 destructive earthquakes have occurred. The temporal and spatial distribution of earthquakes in the Ordos block is asymmetrical. The temporal distribution of earthquakes shows a periodic characteristic and the activity of earthquakes in the southeastern Ordos block is higher than in the northwest Ordos block. The M_S≥5.0 moderate size earthquakes in the Ordos block are controlled by the M_S≥6.0 earthquake around the Ordos block.     

鄂尔多斯白垩系地下水盆地天然水体环境同位素组成及其水循环意义

鄂尔多斯白垩系地下水盆地天然水体的环境同位素组成表明,区内各种地表水体（河流和湖淖）在δ18O和δD图上主要分布在雨水线右侧,其关系线的斜率明显小于雨水线的蒸发线,集中反映蒸发作用对地表水体的影响。盆地内地下水大致集中沿雨水线分布,反映了白垩系盆地内地下水为大气降水成因。盆地南北两区地下水的环境同位素具有明显差异性特点,集中体现了盆地南北两区水循环条件的差异。盆地北区各含水岩组间地下水垂向水力联系比较密切,垂向运动特点比较明显,现代水积极循环带的深度为200 m;南区地下水分层性明显,以水平径流为主,现代水积极循环带的深度为160 m。区内浅层地下水以富氚和高¹⁴C含量为特征,反映为现代水补给;而中、深层地下水则以贫氚和低¹⁴C含量为特征,反映为地质历史时期补给。     

三维地质建模及数值模拟技术在油藏开发中的应用

通过鄂尔多斯盆地油坊庄油田定31井区侏罗纪延长组长1油藏三维精细地质模型的建立,对该区油田地质储量、采油量、含水率和压力等进行了数值历史拟合,摸清该区剩余油的分布规律:剩余油主要分布在构造高部位、沉积主河道注水未波及部位、生产井泄油半径之外和生产井未补孔部位.针对该区剩余油的分布规律制定了新钻调整井和老井侧钻、注采井网完善、采油工艺挖潜3种方法进行开发方案调整,并对调整后的开发技术指标进行了数值模拟预测.     

Microstructural evolution and geologic significance of garnet pyriclasites in the Hoher-Bogen shear zone (Bohemian Massif, Germany)

Ductile extensional movements along the steeply inclined Hoher-Bogen shear zone caused the juxtaposition of Teplá-Barrandian amphibolites, granulites, and metaperidotites against Moldanubian mica schists and paragneisses. Garnet pyriclasites are well preserved within low-strain domains of this shear zone. Their degree of metamorphism is significantly higher than that of the surrounding rocks. Microstructural and mineral chemical data suggest in situ formation of the garnet pyriclasite by dehydration of pyroxene amphibolite at T>750–840°C and P<10–13 kbar including recrystallization-accommodated grain-size reduction of plagioclase and clinopyroxene, nucleation of garnet, and breakdown of amphibole into garnet+clinopyroxene+rutile. Subsequent decompression and retrograde extensional shearing led to the formation of mylonitic epidote amphibolite. The presence of lower crustal and mantle-derived slices within the Hoher-Bogen shear zone supports the view that (a) in Upper Devonian times the Teplá-Barrandian unit was thrust over Moldanubian rocks as a complete crustal unit, and (b) that during the subsequent Lower Carboniferous orogenic collapse, the garnet pyriclasite and metaperidotite were scraped off from the basal parts of the Teplá-Barrandian unit being dragged into the Hoher-Bogen shear zone due to dramatic and large-scale elevator-style movements. Received: 23 March 1999 / Accepted: 25 August 1999