【作者】 李梅；

【导师】 楼章华； 姚根顺；

【作者基本信息】 浙江大学 ， 水工结构工程， 2011， 博士

【摘要】 黔南桂中坳陷海相地层原始成藏条件优越,后期经历了加里东期、海西期、印支期、燕山期和喜山期等多期构造运动,具有多期生烃、多期运聚成藏、多期改造、多期散失等特征,为典型残留盆地,现今油气保存条件破坏严重。论文在分析黔南桂中地区盖层特征和构造作用、岩浆活动对油气保存条件影响的基础上,从流体化学-动力学角度,系统研究了水文地质地球化学特征与油气保存条件之间的关系,恢复了黔南桂中坳陷海相层系油气保存条件的演变规律,提出了一套实用的油气保存条件综合评价指标体系,完善了残留盆地油气保存条件综合评价理论和方法。利用该指标体系对黔南桂中坳陷油气保存条件进行综合分级评价,优选出相对有利勘探区,为今后油气勘探指明了方向。论文主要取得以下成果认识：(1)通过宏观、微观相结合的方法对黔南桂中坳陷盖层封盖能力进行综合评价,结果表明：下寒武统牛蹄塘组、中下志留统翁项组和中下泥盆统泥质岩是黔南桂中坳陷的区域盖层。黔南坳陷下寒武统牛蹄塘组和中下志留统翁项组泥岩盖层在黔南坳陷尤其是南部的长顺凹陷连续分布且深埋于地下,属Ⅱ-Ⅲ类盖层,封盖能力中-好；中下泥盆统泥岩盖层在黔南坳陷南部的长顺凹陷、桂中坳陷西北部和东部地区累计厚度超过600m,属Ⅱ-Ⅲ类盖层,封盖能力中-好；下石炭统盖层残留分布,与上泥盆统盖层互相配合补充形成有效的Ⅰ-Ⅱ类局部盖层,封盖能力好。(2)黔南桂中坳陷内部尤其是黔南坳陷西南部及桂中坳陷中西部地区,深大断裂不发育,构造变形强度弱,利用Ro、包裹体均一温度数据恢复的燕山-喜山期剥蚀厚度相对较小,累计厚度在3500m以下,构造作用对其油气保存条件破坏影响相对较弱；地震活动影响也较弱,且几乎不受岩浆和成矿热液活动的影响。(3)根据研究区断裂发育、温泉分布及温泉水温度数据等估算现今大气水下渗深度,黔南桂中坳陷外围如黔中隆起和黔东北地区、桂东北、桂东南和桂西南地区,大气水下渗深度在1000m以上,水文地质开启程度较高；坳陷内现今大气水下渗深度基本在800m以内,水文地质开启程度相对较低。结合钻井地层水及油气地球化学测试数据分析推断,黔南桂中坳陷内浅于800m地层受现今大气水下渗作用影响强烈,处于自由交替带,油气保存条件差；800m以下地层受大气水下渗影响逐渐减弱,处于交替阻滞带,油气保存条件逐渐变好；交替停滞带可能埋深在2000-3000m以下。因此,黔南桂中坳陷中浅部油气保存条件较差,深层是油气勘探的主要目的层；(4)黔南桂中坳陷海相地层古流体在形成和演化过程中曾遭受古大气水下渗影响。通过方解石脉稳定碳氧同位素和包裹体均一温度测定,恢复了黔南桂中坳陷海相地层古大气水下渗深度。计算结果表明,黔西-平坝-南丹-河池一带古大气水下渗深度最小,约为1600m左右,向周缘地区逐渐增大,都匀-三都-罗城连线以东地区及象州-都安南部地区古大气水下渗深度较大,在2200-3600m之间；(5)在研究区沉积、构造演化史分析的基础上,恢复了研究区古流体动力场的演化过程以及油气成藏、保存的演变规律。黔南桂中坳陷在加里东期和海西期烃源岩进入大量生油期,是黔南桂中地区主要的油藏成藏期；印支期构造活动较弱,原油裂解形成天然气,是该地区主要的天然气藏成藏期。加里东运动和燕山-喜山运动均较强烈,剧烈的抬升剥蚀作用对研究区油气藏产生破坏,但由于志留纪油气生成规模有限,加里东运动对黔南坳陷早期油藏的破坏作用有限,燕山-喜山运动是黔南桂中地区油气藏主要的调整破坏期；(6)通过研究黔南桂中坳陷构造活动、地层流体化学-动力学特征,结合南方四川盆地、南盘江、十万大山、中下扬子等地区油气保存特征,从流体角度将南方海相油气保存单元划分为8种基本类型。黔南桂中坳陷现今属典型的构造破坏残留型盆地,部分地区属于抬升剥蚀-大气水下渗破坏型或剥蚀暴露破坏型油气保存单元类型；(7)在系统研究黔南桂中坳陷现今流体化学-动力学、古流体地球化学特征及流体动力场演化过程的基础上,综合分析了黔南桂中坳陷水文地质地球化学特征与油气保存条件之间的耦合关系,结合研究区盖层特征、构造作用和岩浆活动特征,提出了一套实用的油气保存条件综合评价指标体系；依据该指标体系,对黔南桂中坳陷油气保存条件进行综合分级评价,认为黔南坳陷南部的长顺凹陷和桂中坳陷中西部的忻城地区油气保存条件相对较好；纵向上,好的油气保存条件可能要到2000-3000m以下地层；坳陷内的低潜微幅、低幅构造可能有利于天然气成藏、保存。更多还原

【Abstract】 The original reservoir-forming conditions of marine strata in Qiannan-Guizhong depression were superior, however, it was seriously destroyed after several tectonic movements, such as Caledonian、Hercynian、Indosinian、Yanshan and Himalayan. It is now typical residual basin, which is characterized by multistage hydrocarbon generation and migration, formation of reservoir, reconstruction and dispersion and so on. Based on the analysis of cap rock features in Qiannan-Guizhong area and the influences of tectonism and magmatism, the relationship between hydrological-geochemical characteristics and hydrocarbon preservation conditions was systematically studied through the view of fluid chemical-dynamics. Therefore, the evolution discipline on hydrocarbon preservation conditions of marine strata in Qiannan-Guizhong depression was reverted. Moreover, the comprehensive evaluation theory and method in regard to hydrocarbon preservation conditions of residual basin were improved, and a practical evaluation index system for hydrocarbon preservation conditions was proposed to assess that of Qiannan-Guizhong depression, so that the beneficial storage area was found, giving direction for future exploration of oil and gas. Results as following were drawn during this research:(1) The sealing ability of cap rock in Qiannan-Guizhong depression was evaluated synthetically through both macroscopic and microscopic study. Results show that the Lower Cambrian Niutitang Formation, Middle- Lower Silurian Wengxiang Formation and Middle- Lower Devonian argillaceous rock are regional cap rocks of Qiannan-Guizhong depression; The Lower Cambrian Niutitang Formation, Middle- Lower Silurian Wengxiang Formation argillaceous cap rock distributed continuously and deeply buried in Qiannan depression, especially the Changshun sag, areⅡ-Ⅲtype cap rock, with middle-good sealing capability; The total thickness of Middle- Lower Devonian argillaceous cap rock in Changshun sag of southern Qiannan depression and the northwest and eastern areas of Guizhong depression is above 600 m. Middle- Lower Devonian argillaceous rock also areⅡ-Ⅲtype cap rock, and with middle-good sealing capability; Lower carboniferous cap rock is of residual distribution, however, it can form an effectiveⅠ-Ⅱtype local cap rock in coordination with Upper Devonian argillaceous cap rock.(2) The Qiannan-Guizhong depression, especially the southwest of Qiannan depression and the middle-west of Guizhong depression, is tectonic stable area with no deep faults. low tectonic deformation strength, and small Yanshan and Himalayan erosion thickness of 3500m accumulatively, recoveryed by vitrinite reflectance(Ro) and homogenization temperature of fluid inclusions. So the hydrocarbon preservation conditions were not obviously destroyed by tectonic activity. Also they were not obviously impacted by earthquake, and hardly influenced by magma and ore-forming hydrothermal activities.(3) Based on the study of faults development, distribution and temperature of hot spring, the present meteoric water infiltration depth can be estimated. That of Qiannan-Quizhong margin, e.g. Qianzhong uplift, northeast of Guizhou, northeast, southeast and southwest of Guangxi, is above 1000m, with high hydrogeology open degree, while the present meteoric water infiltration depth in depression interior is below 800m. and with low hydrogeology open degree. Combining with the analysis of drilling well formation water and hydrocarbon geochemical test data, following conclusions are proposed:Strata of depression interior, which was shallower than 800m, was strongly impacted by meteoric water infiltration, and should be free water exchange zone, having poor hydrocarbon preservation conditions; Influence on strata deeper than 800m, called exchanging-retarded zone, became weaker. The hydrocarbon preservation conditions turn into good gradually as the depth increase; The exchanging-stagnant zone should be deeper than 2000-3000m. Therefore, the superficial strata of Qiannan-Guizhong depression have poor hydrocarbon preservation conditions, and deep strata are the target of exploration.(4)The formation and evolution process of paleofluid in marine strata of Qiannan-Guizhong depression was impacted by meteoric water infiltration. Through the analysis of stable carbon and oxygen isotopes of calcite veins and homogenization temperature of fluid inclusion, the ancient meteoric water infiltration depth was recovered. Calculated results show that the infiltraion depth in Qianxi-Pingba-Nandan-Hechi area was about 1600m, and gets deeper in peripheral area; the infiltration in east of Duyun-Sandu-Luocheng and the south area of Xiangzhou-Du’an was deeper, with the value between 2200 and 3000m.(5) The evolution process of paleofluid dynamic field and hydrocarbon accumulation-preservation conditions was reconstructed by the deeply study of deposition, tectonic evolution history of Qiannan-Guizhong depression. During the Caledonian and Hercynian, source rock of Qiannan-Guizhong depression began to generate oil in large quantities. Caledonian and Hercynian were the main oil accumulation stages for Qiannan-Guizhong area, while Indosinian was the main gas accumulation stages as the persistently weak tectonic activity. Caledonian and Yanshan-Himalayan movements were all intense, seriously destroyed the oil and gas reservoir of study area, however, as the size of Silurian oil generation was small, the Early Paleozoic reservoir in Qiannan depression was damaged to a certain extent by Caledonian movement, but that of Qiannan-Guizhong depression was mainly destroyed during Yanshan-Himalayan.(6) The type of southern marine hydrocarbon preservation unit was classified through the study of tectonic activity, geofluid chemistry-kinetics features of Qiannan-Guizhong depression, combining with the characteristics of hydrocarbon preservation in Sichuan Basin, Nanpanjiang, Shiwandashan, middle and lower Yangtze region. The Qiannan-Guizhong depression is now a typical residual basin destroyed by tectonic activity, while some part belongs to uplifting-meteoric water infiltration damaged type or denudation exposed type.(7) The coupled relationship between hydrogeological and geochemical characteristics and the hydrocarbon preservation conditions in Qiannan-Guizhong depression was studied based on the systematical analysis of the present hydrogeology and geochemistry-dynamics, the geochemical characteristics and dynamic field evolution of paleofluid. Then combined with caprock development situation, tectonic and magmatic activity in research area, a practical evaluation index system for hydrocarbon preservation conditions was proposed. Based on that index system, the hydrocarbon preservation conditions in Qiannan-Guizhong depression was comprehensively assessed:Changshun sag in the southwest of Qiannan depression and Xincheng area in the middle-west of Guizhong depression, have relatively good hydrocarbon preservation conditions; The strata deeper than 2000-3000m vertically also have nice hydrocarbon preservation conditions; The deeply buried gentle anticline and low amplitude structure in depression may be suitable for accumulation and preservation of gas.更多还原