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准噶尔盆地腹部深层超压顶面附近(现今埋深4400～6200m,温度105～145℃)砂岩中广泛出现的碳酸盐胶结作用和次生溶蚀孔隙与超压流体活动关系密切.由于超压封闭和释放引起其顶面附近砂岩中的孔隙压力和水化学环境的周期性变化可导致碳酸盐沉淀和易溶矿物溶解过程交替出现.根据腹部地区超压顶面附近深埋砂岩成岩作用、碳酸盐胶结物含量、储集物性、碳酸盐胶结物碳、氧同位素和烃源岩热演化模拟等资料的综合研究表明:含铁碳酸盐胶结物是主要的胶结成分,长石类成分的次生溶蚀孔隙是主要的储集空间类型,纵向上深层砂岩碳酸盐胶结物出现15%～30%含量的地层厚度范围约在邻近超压顶面之下100m至之上大于450m,碳酸盐胶结物出现大于25%含量高值带分布在靠近超压顶面向上的250～300m的地层厚度范围,超压顶面附近砂岩中碳酸盐胶结物含量高值的深度范围也是次生溶蚀孔隙(孔隙度10%～20%)发育带的范围;因晚白垩世以来深部侏罗纪煤系有机质生烃增压作用,导致在超压顶面附近砂岩晚成岩作用阶段深部富含碳酸盐的超压流体频繁活动,所形成的碳酸盐胶结物受到了明显的与深部生烃增压有关的超压热流体和有机脱羧作用的影响;超压流体多次通过超压顶面排放,使得超压顶面附近砂岩遭受了多期酸性流体溶蚀作用过程,形成了次生溶蚀孔隙发育带.
The carbonate cementation and secondary dissolution pores in the sandstone near the deep overpressure in the abdomen of Junggar Basin (present buried depth 4400 ~ 6200m, temperature 105 ~ 145 ℃) are closely related to the activity of overpressure fluid. Periodic changes of pore pressure and chemical environment in the sandstone near the top surface caused by the release can lead to the alternation of carbonate precipitation and dissolution process of the soluble minerals.According to the diagenesis of the deep buried sandstone near the overpressure top in the abdomen area, The comprehensive study on the contents of cements, the reservoir properties, the carbon and oxygen isotopes of carbonate cements and the thermal evolution simulation of source rock shows that the iron-bearing carbonate cements are the major cements, Eroded pores are the main type of reservoir space. The thickness of the formation with 15% ~ 30% content of deep sandstone carbonate cements in the vertical direction is about 100 m above the top of the adjacent overpressure and above 450 m. The carbonate cementation The occurrence of more than 25% of the high value band distribution in the near top of the overpressure 250 ~ 300m stratigraphic thickness range, overpressure top sandstone carbonate cement content in the high value of the depth range Is also the range of secondary dissolution porosity (porosity 10% ~ 20%). Due to the hydrocarbon generation and compression of organic matter in deep Jurassic coal series since the Late Cretaceous, the deep diagenetic stage of sandstone near the overpressure top is rich in carbon The overpressure fluid of acid salt frequently moves and the carbonate cement formed is obviously affected by the overpressure fluid and organic decarboxylation related to the deep hydrocarbon generation and pressurization. The overpressure fluid passes the overpressure top discharge , The sandstone near the overpressure top surface was subjected to a multi-period acidic fluid erosion process, forming a secondary dissolution porosity development zone.