川西坳陷中段地层水地球化学特征及油气保存条件
发布时间：2018-09-11 20:49
【摘要】：地层水为含油气盆地中流体的重要组成部分,地层水的形成及其活动规律与油气的生成、运聚以及油气藏的形成、保存和破坏有着非常密切的关系。川西坳陷是晚三叠世以来由前陆盆地逐渐发展演化而来的坳陷盆地,沉积了巨厚的晚三叠世-白垩纪地层,已经发现了多套含气层系,在这些含气层中普遍存在高矿化度地层水。在地质历史时期,地层水与围岩和油气之间普遍存在物质与能量的交换,而地层水的地化特征正是这些反应过程的直接记录者,蕴含了许多与油气藏形成和保存相关的信息。本文以须二段、须四段、中侏罗统以及上侏罗统地层水资料为研究基础,详细分析了研究区地层水基本地球化学特征,结合工区地质背景,全面分析了研究区地层水类型的成因及地层水初始来源,并且讨论了研究区水文地质保存条件。首先区分出了研究区气井产出水的性质,通过凝析水与液态地层水的矿化度、日产水量以及水气比的差异,将TDS10000mg/l的水样品定义为凝析水,将TDS≥10000mg/l的水样品定义为地层水,在此基础上,通过对比分析研究区各层系地层水矿化度特征,反映出上三叠统地层水矿化度明显大于侏罗系,上三叠统地层水以卤水为主,侏罗系地层以盐水为主;上三叠统地层中,须二段地层水矿化度大于须四段,侏罗系地层中,中侏罗统地层水矿化度大于上侏罗统,总体上研究区地层水矿化度具有随埋深增加而增加的正常演化特征。通过对研究区地层水类型的分析,工区主要以Ca Cl2型地层水为主,以及少量的Mg Cl2型和Na HCO3型,但在上侏罗统出现较多Na2SO4型,从上侏罗统到须二段,水型由Na2SO4型逐渐过渡到Ca Cl2型,矿化度逐渐增高。地层水中主要阳离子是Na+,主要阴离子为Cl-。不同产层地层水阳离子含量大小关系均表现为Na+Ca2+K+Mg2+,须二段、须四段和中侏罗统地层水中阴离子含量大小关系均表现为Cl-HCO3-SO42-,而上侏罗统地层水中阴离子则表现为Cl-SO42-HCO3-。通过与海洋、湖泊以及河流中微量元素含量的对比,研究区地层水还表现为明显富集微量元素Li、Sr、Ba、Br和Fe,表明研究区地层水经历了一定程度分蒸发作用以及水岩相互作用;并且须家河组地层特别富集Br,其富集原因可能主要来自成岩过程中有机质释放出来的Br。基于详细的地层水地球化学特征,结合区域地质特征,分析了研究区不同类型地层水的成因,结果表明,须二段与须四段少量的高矿化度Na HCO3型水的形成最有可能与烃源岩有机成因的CO2有关;中侏罗统与上侏罗统Na HCO3、Na2SO4型最可能是原生的陆相成因地层水,须二段Na2SO4型水可能是Ca Cl2型水与Na HCO3型水这两类地层水混合而成;须四段Mg Cl2型水更可能是原始海相地层水,而上侏罗统Mg Cl2型水则主要是由下伏须家河组高矿化度Ca Cl2型水与上侏罗统低矿化度Na HCO3型水经混合作用而成;中侏罗统与上侏罗统Ca Cl2型水主要是由下伏须家河组高矿化度地层水经过断层运移而来。通过分析地层水的化学组成特征,现今地层水Na-Cl特征与海水蒸发曲线、淡水蒸发曲线的关系表明研究区须二段、须四段地层水均起源于海水,并且海水蒸发程度较弱,主要表现为低蒸发程度海水的特征;侏罗系地层水主要为陆相大气淡水与上三叠统外来海水的混合水体特征。地层水氢氧同位素特征的分析表明研究区地层水以海水与大气水混合成因水为主,上三叠统地层水为混合水体,相对侏罗系地层水表现为更富海水的特征,少量上三叠统地层水因受地层水与CO2同位素交换的影响而表现出明显的δ18O负漂,呈现出大气水成因特征,但是实际上仍是混合水;侏罗系地层水以混合水体为主,中侏罗统地层水较上侏罗统地层水更富海水组分,少数侏罗系地层水仍保持着大气水的特征。研究区发育优质的盖层条件,主要断层大多数封闭性能都较好,通过地层水化学特征参数,如钠氯系数、脱硫系数?碳酸盐平衡系数?氯镁系数等的组合特征的分析,显示出研究区大部分地层水具有浓缩程度高、变质程度深的特征,侏罗系地层的封闭性较上侏罗统差,特别是上侏罗统出现了较多Na2SO4型地层水,油气保存最条件相对较差;须二段与须四段地层相对更为封闭,更有利于油气保存。
[Abstract]:Formation and activity of formation water are closely related to the generation, migration and accumulation of oil and gas, formation, preservation and destruction of oil and gas reservoirs. Western Sichuan depression is a depression basin evolved from foreland basin since Late Triassic and deposited huge thickness of Late Triassic. In the Permian-Cretaceous strata, many sets of gas-bearing strata have been discovered, in which high-salinity formation water is ubiquitous. In geological history, the exchange of substance and energy between formation water and surrounding rocks and oil and gas is widespread, and the geochemical characteristics of formation water are the direct recorders of these reaction processes, containing a lot of oil and gas. Based on the formation water data of Xu 2, Xu 4, Middle Jurassic and Upper Jurassic, the basic geochemical characteristics of formation water in the study area are analyzed in detail. Combined with the geological background of the work area, the genesis of formation water types and the initial source of formation water in the study area are comprehensively analyzed and discussed. The hydrogeological preservation conditions in the study area are firstly distinguished. Through the difference of salinity, daily water production and water-gas ratio between condensate water and liquid formation water, the water sample of TDS 10000mg/l is defined as condensate water, and the water sample of TDS (> 10000mg/l) is defined as formation water. The characteristics of formation water salinity of each stratum in the study area show that the stratum water salinity of the Upper Triassic is obviously higher than that of the Jurassic, the stratum water of the Upper Triassic is mainly brine, and the stratum water of the Jurassic is mainly brine. According to the analysis of the types of formation water in the study area, the main types of formation water in the study area are CaCl2 type, and a small number of MgCl2 type and Na HCO3 type. However, there are more Na2SO4 types in the Upper Jurassic, from the Upper Jurassic to the Xu2 member, and the water types are Na2SO4 type. The main cation in formation water is Na+, and the main anion is Cl-. The relationship between the cation content of formation water in different formations is Na+Ca 2+K+Mg 2+. The relationship between the anion content in formation water in Xu 2 member, Xu 4 member and Middle Jurassic member is Cl-HCO 3-SO 42-, and that in Upper Jurassic formation water is Cl-. The anions in the water are Cl-SO42-HCO3-. By comparing with the contents of trace elements in oceans, lakes and rivers, the formation water in the study area also shows obvious enrichment of trace elements Li, Sr, Ba, Br and Fe, indicating that the formation water in the study area has undergone a certain degree of evaporation and water-rock interaction, and the Xujiahe Formation is especially enriched in B. Based on the detailed geochemical characteristics of formation water and regional geological characteristics, the genesis of different types of formation water in the study area is analyzed. The results show that the formation of a small amount of high salinity Na HCO3 water in the second and fourth member of Xuzhou Formation is most likely to be related to the source rocks. Mesogenic CO2 is related; Middle Jurassic and Upper Jurassic Na HCO3, Na2SO4 are most likely to be primary continental formation water, and the second member of Xujia Formation Na2SO4 may be a mixture of CaCl2 and Na HCO3; the fourth member of Xujia Formation MgCl2 is more likely to be primary marine formation water, while the upper Jurassic MgCl2 is mainly from lower Jurassic. The high salinity Ca Cl_2 water of the Fuxujiahe Formation was mixed with the low salinity NaHCO_3 water of the Upper Jurassic. The Ca Cl_2 water of the Middle Jurassic and Upper Jurassic was mainly migrated from the high salinity formation water of the underlying Xujiahe Formation through faults. The relationship between freshwater evaporation curves and development curves shows that the formation water of Xu 2 and Xu 4 in the study area originates from seawater, and the evaporation degree of seawater is weak, which mainly shows the characteristics of low evaporation degree seawater. Characteristic analysis shows that the formation water in the study area is mainly composed of mixed genetic water of seawater and atmospheric water, and the upper Triassic formation water is mixed water. Compared with the Jurassic formation water, it is characterized by richer seawater. A small amount of the upper Triassic formation water shows obvious negative drift of delta 18O due to the influence of the exchange of formation water and CO2 isotope, showing the formation of atmospheric water. Jurassic formation water is mainly mixed water, and the middle Jurassic formation water is richer in seawater components than the upper Jurassic formation water. A few of the Jurassic formation water still retains the characteristics of atmospheric water. The analysis of the combination characteristics of the characteristic parameters, such as sodium chloride coefficient, desulfurization coefficient, carbonate equilibrium coefficient and magnesium chloride coefficient, shows that most of the formation water in the study area has the characteristics of high concentration and deep metamorphism. The sealing property of the Jurassic strata is worse than that of the Upper Jurassic, especially the formation water of Na_2SO_4 type, oil and gas. The condition of preservation is relatively poor, and the two and four strata are more closed, which is more conducive to oil and gas preservation.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.13
本文编号：2237801
[Abstract]:Formation and activity of formation water are closely related to the generation, migration and accumulation of oil and gas, formation, preservation and destruction of oil and gas reservoirs. Western Sichuan depression is a depression basin evolved from foreland basin since Late Triassic and deposited huge thickness of Late Triassic. In the Permian-Cretaceous strata, many sets of gas-bearing strata have been discovered, in which high-salinity formation water is ubiquitous. In geological history, the exchange of substance and energy between formation water and surrounding rocks and oil and gas is widespread, and the geochemical characteristics of formation water are the direct recorders of these reaction processes, containing a lot of oil and gas. Based on the formation water data of Xu 2, Xu 4, Middle Jurassic and Upper Jurassic, the basic geochemical characteristics of formation water in the study area are analyzed in detail. Combined with the geological background of the work area, the genesis of formation water types and the initial source of formation water in the study area are comprehensively analyzed and discussed. The hydrogeological preservation conditions in the study area are firstly distinguished. Through the difference of salinity, daily water production and water-gas ratio between condensate water and liquid formation water, the water sample of TDS 10000mg/l is defined as condensate water, and the water sample of TDS (> 10000mg/l) is defined as formation water. The characteristics of formation water salinity of each stratum in the study area show that the stratum water salinity of the Upper Triassic is obviously higher than that of the Jurassic, the stratum water of the Upper Triassic is mainly brine, and the stratum water of the Jurassic is mainly brine. According to the analysis of the types of formation water in the study area, the main types of formation water in the study area are CaCl2 type, and a small number of MgCl2 type and Na HCO3 type. However, there are more Na2SO4 types in the Upper Jurassic, from the Upper Jurassic to the Xu2 member, and the water types are Na2SO4 type. The main cation in formation water is Na+, and the main anion is Cl-. The relationship between the cation content of formation water in different formations is Na+Ca 2+K+Mg 2+. The relationship between the anion content in formation water in Xu 2 member, Xu 4 member and Middle Jurassic member is Cl-HCO 3-SO 42-, and that in Upper Jurassic formation water is Cl-. The anions in the water are Cl-SO42-HCO3-. By comparing with the contents of trace elements in oceans, lakes and rivers, the formation water in the study area also shows obvious enrichment of trace elements Li, Sr, Ba, Br and Fe, indicating that the formation water in the study area has undergone a certain degree of evaporation and water-rock interaction, and the Xujiahe Formation is especially enriched in B. Based on the detailed geochemical characteristics of formation water and regional geological characteristics, the genesis of different types of formation water in the study area is analyzed. The results show that the formation of a small amount of high salinity Na HCO3 water in the second and fourth member of Xuzhou Formation is most likely to be related to the source rocks. Mesogenic CO2 is related; Middle Jurassic and Upper Jurassic Na HCO3, Na2SO4 are most likely to be primary continental formation water, and the second member of Xujia Formation Na2SO4 may be a mixture of CaCl2 and Na HCO3; the fourth member of Xujia Formation MgCl2 is more likely to be primary marine formation water, while the upper Jurassic MgCl2 is mainly from lower Jurassic. The high salinity Ca Cl_2 water of the Fuxujiahe Formation was mixed with the low salinity NaHCO_3 water of the Upper Jurassic. The Ca Cl_2 water of the Middle Jurassic and Upper Jurassic was mainly migrated from the high salinity formation water of the underlying Xujiahe Formation through faults. The relationship between freshwater evaporation curves and development curves shows that the formation water of Xu 2 and Xu 4 in the study area originates from seawater, and the evaporation degree of seawater is weak, which mainly shows the characteristics of low evaporation degree seawater. Characteristic analysis shows that the formation water in the study area is mainly composed of mixed genetic water of seawater and atmospheric water, and the upper Triassic formation water is mixed water. Compared with the Jurassic formation water, it is characterized by richer seawater. A small amount of the upper Triassic formation water shows obvious negative drift of delta 18O due to the influence of the exchange of formation water and CO2 isotope, showing the formation of atmospheric water. Jurassic formation water is mainly mixed water, and the middle Jurassic formation water is richer in seawater components than the upper Jurassic formation water. A few of the Jurassic formation water still retains the characteristics of atmospheric water. The analysis of the combination characteristics of the characteristic parameters, such as sodium chloride coefficient, desulfurization coefficient, carbonate equilibrium coefficient and magnesium chloride coefficient, shows that most of the formation water in the study area has the characteristics of high concentration and deep metamorphism. The sealing property of the Jurassic strata is worse than that of the Upper Jurassic, especially the formation water of Na_2SO_4 type, oil and gas. The condition of preservation is relatively poor, and the two and four strata are more closed, which is more conducive to oil and gas preservation.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.13
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