二元同位素测温技术及其在白云岩储层成因研究中的应用——以塔里木盆地中下寒武统为例

作为近年来新兴的实验技术,二元同位素(D47)测温技术已被应用于碳酸盐岩成岩环境的研究中。简要介绍了二元同位素测温技术的原理及应用方法,并以塔里木盆地中下寒武统白云岩为例,优选11块样品,测试其D47值和白云石的碳氧同位素,并计算出样品的成岩温度和古流体的δ~(18)O值。综合分析认为:样品中,颗粒白云岩形成于低温准同生—浅埋藏环境,成岩流体为海水;细晶白云岩为深埋藏成岩环境中原岩受到了高温重结晶作用的改造,成岩流体为地下热卤水;孔缝中的白云石胶结物是深埋藏成岩环境富镁热卤水沉淀作用的产物。研究证明二元同位素测温技术可以较好地恢复白云岩的成岩温度,减少储层成因的多解性,它为今后储层成因研究提供了一种新的手段和依据。

Clumped Isotope Thermometry and Its Application in Dolomite Reservoir: A Case Study of the Middle-Lower Cambrian in Traim Basin

The technology of clumped isotope(D47) thermometry has been applied in the study of the diagenetic environment of carbonate rock as a new experimental technique in recent years. The paper introduces the principle and application method of the clumped istope thermometry. Taking the middle-lower Cambrian dolomites in Tarim Basin as an example, 11 samples were chosen to test D47 value and carbon and oxygen isotope of dolomites, and further, to calculate the diagenetic temperature and δ18O of paleofluids. According to the comprehensive analysis, the diagenetic environment of different types of dolomites is different, and the diagenetic fluid is different too. The granular dolomite formed in low-temperature penecontemporaneous-shallow buried environment, and the diagenetic fluid is seawater. The fine-grained dolomite is formed in the deep-buried diagenetic environment, and the original rock is subjected to high-temperature recrystal ization, and the diagenetic fluid is underground thermal brine. The dolomite cements in the pores or fractures are the products of the precipitation of Mg-rich thermal brine in a deep-buried diagenetic environment. It is proved that the clumped isotope thermometry can obtain the diagenetic temperature of dolomite more effectively and reduce the multi-solution of reservoir genesis, which provides a new means and basis for the future study of reservoir genesis.