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开鲁盆地奈曼凹陷奈1区块九佛堂组地层水地球化学特征与油气保存条件 |
赵兴齐1,陈践发2,程锐3,刘武生1,李西得1,易超1,张字龙1,朱鹏飞1,郭望4
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(1.核工业北京地质研究院中核集团铀资源勘查与评价技术重点实验室,北京 100029;2.中国石油大学油气资源与探测国家重点实验室,北京 102249;3.延长油田股份有限公司,陕西延安 717600;4.中国地质调查局西安地质调查中心,陕西西安 710018)
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摘要: |
基于实际测试资料,统计分析奈曼凹陷奈1区块九佛堂组21口井地层水的水型、矿化度及特征系数在平面及纵向上的变化特征,并探讨研究区地层水地球化学特征与油气的保存及分布关系。结果表明:该区地层水是以阴阳离子分别为HCO3-和(Na++K+)为主的NaHCO3型水,地层水矿化度低;研究区地层水矿化度主要受控于断层的分布,靠近断层的油气井中地层水矿化度明显较远离断层的油气井中的高,主要是由于该区深部的高矿化度地层水经断层及其他运移通道运移至浅层,并与浅层地层水混合所致;地层水化学组分及离子特征系数随深度的变化表现为稳定型、正相关型和负相关型3种变化类型;纵向上,地层水的Cl-浓度、r(Cl-))/r(Mg2+)及r(Ca2+))/r(Mg2+)都随埋深的增加而增大,而HCO3-浓度及r(Na+))/r(Cl-)均随埋深的增加而减小,表明奈1区块九佛堂组地层水现今总体上处于封闭的流体动力环境,有利于油气的聚集与保存;平面上,靠近凹陷中心的奈1块油气井中地层水r(Na+))/r(Cl-)及r(SO42-)×100)/r(Cl-)明显较奈3块及其以西地区偏低,而r(Cl-))/r(Mg2+)及r(Ca2+))/r(Mg2+)明显偏高,表明奈1块地层封闭条件好,更有利于油气藏的形成与保存;研究区断层有效沟通了烃源层与储集层,为浅层次生油气藏的形成提供了必要条件;靠近凹陷中心的奈1块是该区油气勘探的重要领域,且主干断裂和浅层分支断裂发育带是浅层次生油气藏勘探的重要区域。 |
关键词: 地层水 地球化学特征 油气保存条件 奈1区块 奈曼凹陷 开鲁盆地 |
DOI:10.3969/j.issn.1673-5005.2015.03.006 |
分类号::TE 122.2 |
基金项目:大型盆地能源矿产资源综合调查评价项目(资[2014]03-016-044) |
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Geochemical characteristics of formation water and hydrocarbon preservation of Jiufotang Formation in Nai 1 block of Naiman sag, Kailu Basin |
ZHAO Xingqi1, CHEN Jianfa2, CHENG Rui3, LIU Wusheng1, LI Xide1, YI Chao1, ZHANG Zilong1, ZHU Pengfei1, GUO Wang4
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(1.CNNC Key Laboratory of Uranium Resources Exploration and Evaluation Technology in Beijing Research Institute of Uranium Geology, Beijing 100029, China;2.State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China;3.Yanchang oilfield Company Limited, Yan 'an 717600, China;4.Xi 'an Center of Geological Survey, China Geological Survey, Xi 'an 710054, China)
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Abstract: |
On the basis of a large number of test data, the plane and vertical variations of formation water type, salinity and characteristic coefficient in 21 wells of Jiufotang Formation in Nai 1 block, Naiman sag were analyzed statistically. Meanwhile, the relationship between geochemical characteristic of formation water and conservation of oil and gas was investigated. The results show that the formation water with lower salinity belongs to NaHCO3- type water, which is dominated by HCO3- and (Na++K+). The salinity of the formation water is mainly controlled by the distribution of faults in plane. And the salinity of the formation water near the faults is obviously higher than that of the formation water far away from the faults. This is because the formation water with higher salinity in this deep block is transported to the shallow level via faults and other channels, which is mixed with the formation water in the shallow level. The chemical composition and characteristic coefficient can be divided into three types along with the variation of depth, which are stable type, positive correlation type, and negative correlation type. Vertically, the concentration of Cl-, the rate of r(Cl-)/r(Mg2+) and the rate of r(Ca2+)/r(Mg2+) increase with depth increasing, whereas the concentration of HCO3-and the rate of r(Na+)/r(Cl-) decrease with depth increasing. This indicates that the formation water of Jiufotang Formation in Nai 1 block has been conserved in a relatively isolated dynamic environment, which is suitable for oil and gas conservation. In plane, the levels of r(Na+)/r(Cl-) and r(SO42-)/r(Cl-) near the Nai 1 block of the sag center are lower than those of wells in Nai 3 block and the western, while the levels of r(Cl-)/r(Mg2+), r(Ca2+)/r(Mg2+) are higher. This infers that the seal condition of Nai 1 Block is more favorable to oil and gas accumulation. Source rock and reservoir can be connected by faults efficiently, which is suitable for the formation of shallow secondary reservoirs. Nai 1 block near the center of sag can be regarded as the perspective field of area. And principal faults and shallow subsidiary faults are also the interests of secondary reservoirs. |
Key words: formation water geochemical characteristics hydrocarbon preservation condition Nai 1 block Naiman sag Kailu Basin |