贵州织金北部三叠系含水层中浅层高烃地下水成因及其环境意义

发布时间：2018-06-10 06:36

本文选题：原生高烃地下水 + 水岩烃相互作用　；参考：《中国地质大学》2017年博士论文

【摘要】：高烃地下水是指地下水中总石油类浓度超过0.05mg/L(地表水环境质量标准(GB3838-2002)Ⅲ类水质标准)的地下水。按成因分为次生及原生高烃地下水。不同于次生高烃地下水,原生高烃地下水是在天然环境中形成,会极大的消减地下水受纳有机烃类的能力并引发一系列环境问题。在历时五年对贵州织金北部地区三叠系浅层含水层水质监测过程中,发现区内大部分作为饮用水源的地下水中石油类浓度长期超过0.05mg/L,而痕量的次生有机物,不能形成长期大范围高烃地下水现象,指示原生浅层高烃地下水的存在。本文运用室内外实验相结合的方法,主要开展两方面进行研究:1、贵州三叠系地层生烃潜力探究;2、地层中有机质向浅层地下水环境中迁移转换途径探究。具体研究内容及成果主要体现在以下四个方面:A.“补”——三叠系浅层原生高烃地下水的来源研究区三叠系地层具备一定程度释烃能力。通过对区内三叠系下统永宁镇组(T1yn)至上统须家河组(T3x)地层的沉积环境、古生物类型、化学组分、生烃潜力及生物标志物特征分析,发现区内三叠系地层沉积过程整体呈现海相逐渐向陆相转变的特点,存在多个海进与海退旋回。不同时期地层生烃潜力不一。永宁镇组四段(T1yn4)及关岭组三段(T1g3)地层具备相对较高的生烃潜力,岩性均以白云岩或灰质白云岩为主,有机质母源以海相低等生物为主,存在陆源碎屑输入,大部分形成于还原性环境。其次为关岭组二段(T2g2)地层,岩性以灰岩为主,有机质母源主要受海相藻类输入,偶见陆源碎屑输入,形成于还原性环境。永宁镇组三段(T1yn3)、关岭组一段(T2g1)及法郎组(T2f)地层的生烃潜力较低。须家河(T3x)地层为陆相沉积,生石油烃潜力极小。B.“径”——水岩烃相互作用释烃理论水岩中有机质同源。有机质进入地下水的可能途径包括溶蚀释烃及抽提释烃。根据研究区各地层生烃潜力差异及水文地质条件特征,针对不同含水层、深度及补径排区进行地下水质监测,分析地下水中元素组分、氢氧同位素、锶同位素、次生有机物及对比水岩中生物标志物特征。结果显示研究区内地下水矿物元素改造基本来自背景地层,存在较强的水岩相互作用。岩石及地下水中正构烷烃在重碳区分布规律极为相似,指示有机质同源,而轻饱和烃难以在地下水中检出,主要由其理化性质决定,饱和烃碳数越小,越不易进入浅层地下水环境。C.“排”——生烃潜力层释烃能力及主驱动力岩层溶蚀程度是释烃作用的主要驱动力,抽提释烃在溶蚀释烃基础上进行,对释烃有一定的促进作用。野外溶蚀试验及室内物理模型结果发现地层释烃量与溶蚀量呈正比,且永宁镇组四段(T1yn4)地层呈现“陡变”规律,指示其为有机质“储层”,而关岭组三段(T2g3)地层呈现“缓变”规律,指示其为有机质“生油层”。虽然抽提释烃模型中,释烃量远高于溶蚀释烃模型,但在天然环境中,地下水中有机质浓度低,抽提释烃作用微弱。在假设条件:(1)以地下水系统为单位;(2)系统内富水性均一;(3)系统内不存在大型集中式管道;(4)地下水中矿物元素来源于背景地层;(5)不考虑地下水流动对总石油类浓度稀释富集作用;(6)岩层释烃全部进入地下水中,且在地下水中均匀分布的情景中,估算大龙井-以冲沟岩溶地下水系统总石油类浓度。结果显示,基于地下水中矿物组成估算浅层地下水中总石油类浓度约为0.05~0.50mg/L,接近野外实测值。基于野外溶蚀试验数据估算浅层地下水中总石油类浓度约为4.60mg/L大于实测最大值,此方法仅适用于岩石溶解受裂隙溶解控制,且溶蚀试验切块的裂隙发育具有代表性时,具有一定可靠性。D.“应用”——金沙小区三叠系含水层原生高烃地下水预评价金沙小区主要出露三叠系地层,总出露面积占36.92%,主要生烃潜力层为永宁镇组四段(T1yn4)及关岭组三段(T2g3)。在假设条件:(1)以地下水系统作为一个单元;(2)排泄区地下水中钙镁离子全部来源于水岩交换作用;(3)仅考虑水岩交换程度同水岩接触时间有关;(4)不存在集中式径流管道;(5)当地下水中总石油类浓度达到0.04mg/L时,认为系统内可能出现浅层原生高烃地下水现象的前提下,结合金沙小区地形坡度及地貌特征,对其三叠系含水层进行原生高烃地下水战略评价,认为浅层原生高烃地下水可能在小区南部,中部,西北及东北部,特别在地形坡度较缓的灰岩分布区和岩层较为破碎的白云岩分布区,当水中Ca2+、Mg2+浓度分别达9.15mg/L和5.45mg/L时,有可能出现原生高烃地下水现象。
[Abstract]:High hydrocarbon groundwater refers to the groundwater in the groundwater with total oil concentration exceeding 0.05mg/L (surface water environmental quality standard (GB3838-2002) III water quality standard). It is divided into secondary and primary high hydrocarbon groundwater according to the cause of origin. Different from secondary high hydrocarbon groundwater, the primary high hydrocarbon groundwater is formed in the sky environment and will greatly reduce the groundwater acceptance. The ability of organic hydrocarbons and triggering a series of environmental problems. During the monitoring of the water quality of the shallow aquifers of the Triassic in northern Zhijin, Guizhou, during the last five years, most of the petroleum concentration in the groundwater, which was used as a source of drinking water, was more than 0.05mg/L for a long time, and the trace secondary organisms could not form a long-range high hydrocarbon underground. Water phenomenon indicates the existence of primary shallow high hydrocarbon groundwater. In this paper, two aspects are mainly carried out by the combination of indoor and outdoor experiments: 1, the exploration of hydrocarbon generating potential of the Triassic strata in Guizhou; 2, the migration and transformation of organic matter in the shallow groundwater environment. The specific content and results are mainly reflected in the following four A. "supplement" - the source of the Triassic shallow primary high hydrocarbon groundwater, the Triassic strata of the Triassic have a certain degree of hydrocarbon release. Through the sedimentary environment, paleontology, chemical composition, hydrocarbon potential and biomarker characteristics of the strata of the upper Triassic Yongning group (T1yn) in the upper Triassic Xujiahe Formation (T3x), the characteristics of the hydrocarbon generation potential and biomarkers are analyzed. The sedimentary process of the Triassic System in the present area is characterized by the gradual transformation of marine facies to the continental facies, and there are many marine and regressive cycles. There are different hydrocarbon potential in different periods. The four section of Yongning Town Group (T1yn4) and the three section of Guanling formation (T1g3) have relatively high hydrocarbon generating potential, and the lithology is dominated by dolomite or gray dolomite. The parent source is mainly marine lower organisms, and most of them are detrital input, most of which are formed in reductive environment. The second is the two section of Guanling formation (T2g2), and the lithology is mainly limestone, and the organic parent source is mainly imported by marine algae. It is found in the reductive environment. The three segment of Yongning Town Group (T1yn3), and the first section (T2g1) of the Yongning group (T2g1) and The hydrocarbon generation potential of the formation of the franc group (T2f) is low. The Xujiahe (T3x) stratum is continental deposit, and the potential of the petroleum hydrocarbon potential is minimal.B. "diameter" - the organic matter of organic matter in the water rock release theory of water rock hydrocarbon interaction. The possible ways for the organic matter to enter the groundwater include dissolution and extraction and extraction of hydrocarbon. According to the difference of hydrocarbon potential potential differences and water in the area of the study area According to the characteristics of geological conditions, the groundwater quality monitoring is carried out in different aquifers, depth and filling area. The elements of elements, hydrogen and oxygen isotopes, strontium isotopes, secondary organic matter and the characteristics of biomarkers in water rocks are analyzed. The results show that the transformation of underground water minerals in the study area is basically from the background strata and has strong water. The distribution of n-alkanes in rock and groundwater is very similar in the heavy carbon region, indicating that the organic matter is homologous, and the light saturated hydrocarbons are difficult to detect in the groundwater. It is mainly determined by its physicochemical properties. The smaller the number of saturated hydrocarbons, the more difficult it is to enter the.C. "row" of the shallow groundwater environment, the hydrocarbon generation capacity of the hydrocarbon potential potential layer and the main driving force. The degree of dissolution of the rock layer is the main driving force of hydrocarbon release. The extraction and release of hydrocarbon on the basis of dissolution and hydrocarbon release has a certain promotion effect on hydrocarbon release. In the field, the results of field dissolution test and indoor physical model found that the amount of hydrocarbon release is proportional to the amount of dissolution, and the four section of Yongning group (T1yn4) shows a "steep change" rule, indicating that it is organic. The three section (T2g3) of the Guanling formation shows a "slow change" rule, indicating that it is an organic "raw oil layer". Although in the extraction of hydrocarbon model, the amount of hydrocarbon release is much higher than that of the dissolved hydrocarbon model, but in the natural environment, the concentration of organic matter in the groundwater is low and the extraction and release of hydrocarbons is weak. (1) the groundwater system is the unit; 2) the water rich uniformity within the system; (3) there is no large centralized pipeline in the system; (4) the mineral elements in the groundwater are derived from the background strata; (5) no consideration is given to the concentration and enrichment of the total oil concentration by the groundwater flow; (6) the rock hydrocarbon release into the groundwater is all into the groundwater, and the great Longjing - gully rock is estimated in the situation of the uniform distribution of the groundwater. The results show that the total petroleum concentration in shallow groundwater based on the mineral composition of underground water is estimated to be about 0.05~0.50mg/L, close to the field measured values. Based on the field test data, the total petroleum concentration in shallow groundwater is estimated to be about 4.60mg/L greater than the measured maximum, and this method is only suitable for rock. When dissolution is controlled by fissure dissolution and the fracture development of the dissolution test block is representative, it has a certain reliability.D. "application" - the pre evaluation of the primary high hydrocarbon groundwater in the Triassic aquifer of Jinsha district is mainly exposed to the Triassic strata, the total exposed area is 36.92%, the main hydrocarbon potential layer is the four segment of Yongning Town Group (T1yn4). And the three section of the Guanling formation (T2g3). In the assumption condition: (1) the groundwater system is used as a unit; (2) the calcium and magnesium ions in the groundwater in the drainage area are all derived from the water rock exchange; (3) only the water and rock exchange degree is related to the contact time of the water rock; (4) there is no centralized runoff pipeline; (5) when the concentration of the total oil in the groundwater reaches 0.04mg/L, Considering the possibility of shallow primary high hydrocarbon groundwater in the system, combining the terrain slope and geomorphic characteristics of the Jinsha residential area, the strategic evaluation of the primary high hydrocarbon groundwater in the Triassic aquifers is carried out. It is considered that the shallow primary high hydrocarbon groundwater may be in the south, middle, northwest and northeastern part of the residential area, especially in the gentle slope of the terrain. The distribution area of rock distribution and rock strata is relatively broken dolomite. When the concentration of Ca2+ and Mg2+ in water reaches 9.15mg/L and 5.45mg/L, it is possible to appear the phenomenon of primary high hydrocarbon groundwater.
【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P641

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