摘要
川东鄂西上二叠统生物礁常有白云岩发育。白云石化的晶间孔和溶孔是礁型气田的主要储集空间。岩石学和地球化学资料表明,礁白云石化为埋藏成因。交代的流体是盐度比海水要高的地层水。在埋藏成岩作用过程中,礁白云岩是多次交代形成的。
The Upper Permian reefs in East Sichuan and West Hubei have undergone complex di-agenesis and extensive dolomitization. It is known that the primary pores have disappeared, but intercrystal pores and vags produced as a result of dolomitization and dissolution are common in hydrocarbon reservoirs. Seven textural types of dolomite have been recognized. Petrography and geochemistry data of these dolomites, including cathode luminescence, X-ray diffraction, trace elements, C and O isotopes and fluid inclusions, suggest that the dolomites in the upper parts of reefs, with low order index, high Sr content, and δ13C = + 0.95 and δ1 O=5.35‰ on average, are products of penecontemporary dolomitization in tidal flats, and the inner dolomites, characterized by high order index, low Sr and Na contents, and δ13C = + 3.13 and δ18O = - 5.9‰ on average, were formed as a result of multi-stage metasomatism in burial diagenetic environments. The fluids responsible for dolomitization are a kind of formation water high in salinity (about 7-8%), which was possibly derived from dehydration of the Upper Permian and Triassic limemud and clay.
出处
《地球化学》
CAS
CSCD
北大核心
1992年第2期158-165,共8页
Geochimica
