陕甘宁盆地中部气田奥陶系碳酸盐岩储层溶蚀及充填作用特征

DISSOLUTION AND INFILLING OF THE ORDOVICIAN CARBONATE ROCK RESERVOIRS IN THE GAS FIELDS IN THE CENTRAL PART OF THE SHAANXI-GANSU-NINGXIA BASIN

关键词:  奥陶系  碳酸盐岩  蚀溶作用  充填作用  储集空间

Key words:  Ordovician  carbonate rock  dissolution  infilling  storage space

摘要:

陕甘宁盆地中部气田产于奥陶系顶部古风化壳碳酸盐岩储集体中,碳酸盐岩储集空间的形成是不同期次的溶蚀作用和充填作用相互作用的结果。根据盆地发展演化阶段不同,大致可以分出四期:第一期为近地表早期成岩溶蚀作用与充填作用(O₁);第二期为风化壳岩溶作用及充填作用(O₂-C₁);第三期为浅埋藏期溶蚀作用与充填作用(C₂);第四期为深埋藏期溶蚀作用与充填作用(P-Q)。化学充填作用形成的自生矿物主要有方解石、白云石、粘土矿物、石英,石膏等.根据充填顺序,地球化学特征等的不同,判别了自生矿物生成顺序及期次。最后论述了不同期次溶蚀作用和充填作用对储集空间形成的建设与破坏作用。

Abstract:

The gas fields in the central part of the Shaanxi-Gansu-Ningxia Basin occur in the car-bonate rock reservoirs in the weathered crust on the top of the Ordovician strata.The stor-age spaces of the carbonate rocks resulted from the interaction of multistage dissolution and infilling,which may be divided into four stages on the basis of the development and evolution.(1) The near-surface early diagenetic dissolution and infilling (O₁);(2) the disso-lution and infilling of the weathered crust (O₂-C₁);(3)the shallow burial dissolution and infilling (C₂),and (4)deep burial dissolution and infilling (P-Q).The formation orders and stages of the chemically precipitated authigenic minerals such as calcite,dolomite,clay min-erals,quartz and gypsium have been distinguished in terms of the study of their infilling or-ders and geochemical properties.Finally,the present paper has dealt with the constructive and destructive effects of dissolution and infilling in different stages on the formation of the storage spaces.