【作者】 钟倩倩；

【导师】 黄思静；

【作者基本信息】 成都理工大学 ， 矿物学、岩石学、矿床学， 2010， 硕士

【摘要】 塔河油田是我国第一个古生界海相大油田,它实现了古生代海相碳酸盐岩油气勘探的重大突破,而奥陶系是其主要的储集层,所以应用地球化学方法研究塔河油田奥陶系储层具有重要的经济意义。笔者在充分利用前人研究成果的基础上,以20口钻井的岩石样品为主要分析对象,运用组分图象统计鉴定,普通薄片和铸体薄片分析,氧、碳同位素分析,锶同位素分析,阴极发光分析,电子探针,微量元素分析,流体包裹体分析等分析测试方法,对塔河油田奥陶系古岩溶储层岩石学特征、地球化学特征,成岩流体的性质及来源、孔洞缝及其充填物的成因等进行了深入系统的研究,得出了如下几点认识:1塔河油田奥陶系的碳酸盐岩岩石类型具有很强的分带性,在良里塔格组、恰尔巴克组、一间房组、鹰山组的岩石类型以灰岩为主,在下奥陶统的蓬莱坝组以白云岩为主。2总体上看,塔河油田奥陶系孔、洞、脉中碳酸盐矿物的δ18O值、δ13C值比灰岩基质低,87Sr/86Sr比值、铁含量、锰含量比灰岩基质高,显示孔洞缝充填物受到了大气淡水的作用。3流体包裹体证据显示塔河油田碳酸盐储层至少经历了六期不同温度、不同盐度、不同密度流体的改造。4利用塔河油田奥陶系不整合面附近的碳酸盐岩、脉方解石和孔洞中方解石中铁锰含量的变化,界定古喀斯特作用的影响深度为130m。5塔河油田共有三个不整合面对发育优质储层具有贡献意义,分别是加里东中期第一幕形成的中上奥陶统恰尔巴克组与其下一间房组间的界面、加里东中期第二幕形成的上奥陶统桑塔木组与良里塔格组间的界面、海西早期形成的石炭系岩层与下伏奥陶系岩层间的区域性角度不整合界面。加里东中期第一幕、第二幕的岩溶产物主要分布于塔河油田南部,上覆的桑塔木盖层使南部加里东中期的岩溶产物在海西期免遭剥蚀而得以保存。海西早期形成的岩溶产物主要分布于塔河油田北部。6将三期不整合面附近的孔洞缝充填物地球化学特征进行比较:加里东中期第一幕岩溶产物具有最低的锰值、锶同位素比值,第二幕岩溶产物其次,海西期岩溶产物最高。第一幕和第二幕岩溶产物的碳同位素比值均比海西期的偏正。以上表明第一幕岩溶产物来源于碳酸盐台地内部,并且暴露剥蚀时间不长,与有机质氧化的关系不大,锶同位素来源于碳酸盐重溶。第二幕只有在桑塔木盖层薄,并且有横切该盖层的大型裂缝同时出现时,良里塔格岩层才会遭受陆源锶的影响、碳同位素也会相应的负偏移;海西期奥陶系碳酸盐与泥盆、石炭系陆相硅铝质岩石同时暴露,受到陆源锶的影响最大,同时因为构造强烈,暴露时间长,受到有机质氧化产生的轻CO2加入的影响,故碳同位素偏负。7塔河油田奥陶系碳酸盐岩不仅遭受表生岩溶的作用,而且遭受埋藏溶蚀的改造。流体包裹体数据表明,不整合面附近的一些孔洞缝充填物是在高温流体甚至热液的作用下形成的。在距离不整合面大于130m的地方,仍然存在孔洞缝及其充填物。通过流体包裹体分析,在塔河西部奥陶系蓬莱坝组存在高温白云岩,为热液成因,这可能与热流体沿塔河西部的大型构造断裂运移有关。8塔河油田经历过加里东中期和海西早期两次构造抬升,鹰山组底部和蓬莱坝组碳酸盐岩由于远离地表而未能发生表生岩溶,一直处于埋藏成岩阶段,但构造抬升会使处于埋藏的鹰山组底部和蓬莱坝组碳酸盐岩发生倒退溶解,这是形成深部孔洞缝的一个重要途径。另外,由于构造抬升运动形成了大量断层,一些热流体会沿着断层向上运移并对碳酸盐岩进行溶蚀,这是形成深部孔洞缝的另一个重要途径。在海西早期之后的印支—燕山期、喜马拉雅期,塔河油田都是处于盆地沉降阶段,现在的埋深是其最大埋深,持续的构造沉降使得岩层的温度一直处于升高状态,即存在正的ΔT,其结果是整个塔河油田奥陶系岩层中储集空间的沉淀封堵。更多还原

【Abstract】 Tahe oilfield is the first big Palaeozoic marine oilfield of China, and it has obtain a breakthrough in Paleozoic Marine carbonate oil and gas exploration. Ordovician carbonates is the main reservoir, so it will make huge economic value to research Ordovician reservoirs in tahe area by geochemical method.Besides learning previous research achievements, author analyzed the rock sample from twenty drilling wells. Concrete analysis methods include carbon isotope analysis, oxygen isotope analysis, strontium isotope analysis, Cathodeluiminescence, electronic probe, trace element analysis and fluid inclusion analysis. Author has get some opinions as follows:1 Rock types of Ordovician carbonates in Tahe area is correlated with era. Limestone Mainly distributed in Lianglitage formation, Qiaerbake formation, Yijianfang formation and Yingshan formation. Dolostone Mainly distributed in Penglaiba formation.2 On the whole, oxygen isotope and carbonate isotope of carbonate minerals in pore spaces or fissures are lower than Ordovician limestone. strontium isotope, iron content and manganese content of carbonate minerals in pore spaces or fissures are higher than Ordovician limestone. It shows that carbonate minerals in pore spaces or fissures were subjected to fresh water.3 Inclusion data shows that at least six types of fluids are involved with Ordovician carbonates in Tahe area.4 The change of iron content and manganese content in calcite vein and calcite in pore is related to the distance with unconformities. Author use the change to define depth of paleokarst influence. The depth of paleokarst influence is 130 meters.5 There are three unconformities which contribute to carbonate reservoirs: the boundary surface of middle-upper Ordovician Qiaerbake formation and Yijianfang formation in Caledonian’s first act, the boundary surface of upper Ordovician Sangtamu formation and Lianglitage formation in Caledonian’s second act, the boundary surface of carbonic rock formation in early Hercynian and Ordovician rock formation. karst product formed in middle Caledonian locates at south of Tahe oilfield, and it isn’t affected by karstification in early Hercynian because of Sangtamu formation. karst product formed in early Hercynian locates at north of Tahe oilfield.6 Manganese content and strontium isotope of the karst product formed in Caledonian’s first act is lowest. Manganese content and strontium isotope of the karst product formed in Caledonian’s second act is lower than the karst product formed in early Hercynian. Carbonate isotope of the karst product formed in Caledonian’s first-second act is higher than the karst product formed in early Hercynian. Form above comparison, we can draw the proper conclusions. The karst product formed in Caledonian’s first act is not correlated with organic, and the time of exposure of it is very short. If the Sangtamu formation is very thin and huge faults cut across the formation, Lianglitage formation will has higher strontium isotope and lower carbonate isotope. In Hercynian, Because Ordovician carbonates and Devonian-Hercynian siallite rocks are both above the ground, the karst product formed in Hercynian has higer strontium isotope. Due to long time’s soluting in Hercynian, the karst product has lower carbonate isotope.7 Ordovician carbonates in Tahe area also suffered buried solution. Inclusion data shows that some carbonate minerals in pore spaces or fissures near unconformities are connected with high temperature fluid even hydrotherm, and that there is high temperature dolomite in Ordovician Penglaiba formation, which might associated with huge fault in west Tahe area.8 Due to far away from unconformities , carbonates in Penglaiba formation and bottom Yingshan formation didn’t suffer epiclastic karst in mid-Caledonian and early Hercynian. But carbonates in Penglaiba formation and bottom Yingshan formation suffer retrograde solubility because of tectonic uplift. The other way to make arbonates in Penglaiba formation and bottom Yingshan formation solubility is fluid moving along faults formed in tectonic uplift. Because Tahe basin subsides all the time after Hercynian, the temperature of rock strata steady increases. Reservoir space in Tahe oilfield has blocked up because of plusΔT.更多还原