地学前缘 ›› 2008, Vol. 15 ›› Issue (6): 303-311.

• 论文 • 上一篇    下一篇

渝北—川东地区黄龙组古岩溶储层稳定同位素地球化学特征

  

  1. 1成都理工大学 “油气藏地质及开发工程”国家重点实验室, 四川 成都 610059
    2中国石油西南油气田分公司重庆气矿, 重庆 400021

  • 出版日期:2008-06-20 发布日期:2008-06-20
  • 作者简介:郑荣才(1950—),男,教授,博士生导师,沉积学和石油地质学专业。E-mail:zhengrc@cdut.edu.cn
  • 基金资助:

    国家自然科学基金项目(40672073);教育部博士点基金项目(20060616014)

Geochemical characteristics of stable isotopes in paleokarst reservoirs in Huanglong formation in northern Chongqingeastern Sichuan area.

  1. 1State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China
    2Chongqing Gas District of Southwest Oil and Gas Company of CNPC, Chongqing 400021, China

  • Online:2008-06-20 Published:2008-06-20

PDF (PC)

657

摘要：

        石炭系黄龙组碳酸盐岩古岩溶储层是渝北—川东地区最重要的天然气储集类型之一。依据岩溶岩的结构特征,将黄龙组岩溶岩系划分为弱溶蚀岩溶岩、中等溶蚀多孔状岩溶岩、强溶蚀角砾状岩溶岩和强溶蚀交代的次生灰质岩溶岩等4种岩溶岩类型,和淡水方解石与白云石两种胶结物类型。以基质岩为对比参照物,对各类岩溶岩和胶结物的碳、氧、锶稳定同位素分析对比研究结果表明,不同成因类型、溶蚀强度、结构和成分的岩溶岩与胶结物的碳、氧、锶稳定同位素地球化学特征各异,其形成、演化和分布规律明显受古地理背景、流体性质、流体来源以及同位素分馏效应控制。依据岩溶岩系的结构和地球化学特征的差异性,可总结出4个主要特征:（1）伴随岩溶强度加大,δ13C表现向低值方向弱偏移,而δ18O负偏移较强烈;（2）87Sr/86Sr比值出现由渗流活跃潜流带的正偏移,至静滞潜流带转化为强烈负偏移的演化趋势;（3）对应古岩溶系碳、氧、锶稳定同位素演化,古岩溶储层的物性出现由差变好至重新变差的对应变化关系;（4）淡水白云石结晶沉淀过程中可能具有对87Sr有很强“捕获”能力的锶同位素正偏移分馏效应。

关键词: 渝北—川东地区;黄龙组;古岩溶储层;碳、氧、锶稳定同位素;地球化学;岩溶流体

Abstract:

     The carbonatite karst reservoir of Huanglong Formation in the Upper Carboniferous is one of the most important natural gas reservoirs in northern Chongqingeastern Sichuan area Based on the structural features of karst rocks,we divide the paleokarst rock series of Huanglong formation into four types:slightly corroded; medium corroded and porous; strongly corroded and brecciated; strongly corroded and metasomatic secondary greypaleokarst rock; and differentiate two kinds of cements:limniccalcite and limnicdolomite Compared with matrix rocks,we have made a synthetical analysis of the geochemical characteristics of carbon,oxygen and strontium isotopes for different carbonate rocks, karstificated dolostones, karst breccias and carbonate cements The results suggest that the carbonate reservoirs in the formation were formed as a paleokarst in the Late Carboniferous,with different karst products showed by different stable isotopic geochemical characteristics, and that the evolutionary patterns of the isotopes are obviously controlled by the palaeogeographic background,fluid property,fluid sources,as well as isotopic fractional effect Based on the structure and the differences of geochemical characteristics of paleokarst rock series,we sum up their four basic features as follows:(1)with enhancement of karstification,the δ13C shows weak negative deviation and the δ18O shows strong negative deviation; (2)the 87Sr/86Sr ratio presents an evolutionary trend from the positive deviation for the infiltrating fluid belt and the active underflow belt gradually transforming to the strong negative deviation for the inactive underflow belt; (3)corresponding to the evolutionary trend of carbon,oxygen,strontium stable isotopes,the paleokarstreservoir properties changed from bad to good and to worse again; (4)limnicdolomite may have strong ability of “capturing” 87Sr leading to the Sr isotope positive deviation effect in the course of crystallization and deposition

Key words:

northern Chongqingeastern Sichuan area;Huanglong formation;paleokarst reservoir;carbon,oxygen,strontium stable isotopes;geochemistry;karst fluid

中图分类号: