鄂尔多斯盆地奥陶系热水岩溶特征

鄂尔多斯盆地奥陶系深部白云岩中的溶蚀孔洞,其成因属于热水岩溶作用的结果。本文通过成因矿物学及Fe2+ 、Mn微量元素分析和气液包裹体测定,结合岩溶发育的构造背景,深入揭示了本区热水的来源主要为深部循环热水,局部尚有深部上升的热液加入 ;其热能除地温梯度加热、构造运动加热外,在盆地基底古断裂附近可能还有深部热源的影响而形成的中低焓地热流体。充填矿物包裹体均一温度为 15 0～ 34 9℃,气相成分中CO₂ 摩尔浓度达到44.3%～ 5 6.98%。Fe2+ 、Mn微量元素在鄂 6、定探 1、李华 1井、芦参 1井、陕 8井和旬探 1井白云岩中的富集,指示了这些井区是热水运移的主要近源区。认为热水岩溶的发育,对奥陶系内幕储层的形成具有重要意义

Hot Water Karst Characteristics of Ordovician Period in Ordos Basi n

The karst vugs in the fine doiomites of Ordovician in Ordos Basin are the resuit of iong time action caused by deepiy buried hot water karst. Futher study, based on hot water karst deveioping background and hydroiogy conditions, shows that the deep circuiating hot water is the main water source of deep Ordovician in this area, and partiy in the ancient fauit zones where some rising up hot water is intruded in.Heat energy is iargeiy from geothermai gradient, structure movement, whereas the infiuences of deep heat source is aiso the important reason of forming mid-iow enthaipy terrestriai heat fiuid. The forming of the fiuid is reiated not oniy to the change of radioactive materiai in sediments and change of Moho depth, but aiso to the heat events occurred in Yanshan movement. The hot water karst and the generai karst can be distinguished by karst shapes and the geochemistry marks of fiiiing materiais. The ring-shaped fiiiings formed by hot water karst are much narrower on the upward direction and wider down, big vugs formed in the upper part aiong the upward direction, therefore, it is different from the generai karst, and the direction of hot fiuid movement can be pointed out from bottom to top. The physicai chemistry properties of the hot water can be refiected from some styiistic minerai veins, such as heteromorphism doiomite vein fiiied in the fissures of doiomite rocks, iead and zinc vein, and the crystai-caicite vein.Minerai inciusion determination shows the average temperature is 150C ~ 349C, moie co- Oncentration of CO₂ in the gas phase compositions reached 44.3% ~ 56.9corrosion capacity and soiuabiiity. The research shows, during the deveiopment of hot fiuid karst, the artesian hot water from different depths causes the increase of karst water specific gravity with the pressure boost and the increase of saiinity, and drives the water fiow form highpressure zone to the iower, at the same time, the rising water temperature and the increase of dissoived gas get the water gravity decreased, boosting the hot water move in circuiation in the sediments. So it is ciear that the deepiy buried hot water karst in this area is dominated by deep heat source and the hot water circuiation. Based on the content changes of trace eiements of Fe2+ and Mn, it has been distinguished that the weii Zones of Er6, Dingtanl, Lihual, Lucanl in the west part of the basin, Xongtanl in the south, and Shan8, Shanl2 in the east are the main Zones where hot water circuiation is active, and are favorabie for the deveiopment of hot water karst. It piays an important roie in forming deep Ordovician reservoir in this area.