准噶尔盆地东部石炭系巴塔玛依内山组火山岩气孔充填作用

Study on vesicle filling of Carboniferous Batamayineishan Formation volcanic rocks in eastern Junggar Basin

通过薄片鉴定、电子探针、地质温度计、面孔率等手段对准噶尔盆地东部地区巴塔玛依内山组火山岩杏仁体进行研究。结果表明:火山岩内气孔充填物包括硅质、沸石、绿鳞石、绿泥石、皂石等,杏仁体充填以复成分为主,单成分少见,单成分杏仁体见硅质和绿鳞石杏仁体两种,复成分杏仁体包括石英→沸石、石英→绿泥石、石英→绿鳞石→皂石等10种;气孔内充填的绿泥石形成温度介于84.7~123.6℃,为低温充填,综合分析认为巴塔玛依内山组中基性火山岩气孔充填为后生流体沉淀结晶的结果;气孔充填使巴塔玛依内山组火山岩储层质量明显变差,约94.5%的原生气孔空间完全丧失;充填作用虽然使火山岩储集空间丧失,但是残存的杏仁体内孔、杏仁体收缩孔仍具有一定的储集能力,流体在气孔内沉淀结晶的同时,也伴随着火山岩溶蚀作用的进行,过程中产生的溶蚀孔也在一定程度上对气孔体积的减少起到补偿作用。

In order to identify characteristics, genesis and reservoir significance of vesicle filling, volcanic rocks with amygdules of Carboniferous Batamayineishan Formation were sampled in eastern Junggar Basin. Based on thin section observation, EPMA, geologic thermometer and vesicle filling rate analysis, the amygdules were characterized. The results show that the filling minerals include silica, zeolite, celedonite, chlorite, and saponite. There are two filling models, mono- and multiple component ones. Mono-component amygdules include silica and celedonite ones. 10 types of multiple component amygdules can be recognized, including quartz→zeolite, chlorite→quartz, and quartz→celedonite→saponite. The formation temperature of chlorite at the edge of amygdales is between 84.7 and 123.6 ℃,which indicates a low temperature filling process. The amygdules form from precipitation and crystallization of epigenetic fluid. The quality of volcanic reservoirs becomes worse due to the vesicle filling process. 94.5% of the primary vesicle space is completely lost. Although vesicle filling has such a negative influence on reservoir quality, residual amygdule inner pores and amygdule shrink pores still have some reservoir capability. In addition, the dissolution pores generated by the fluid which participate in the formation of amygdule can also compensate the reduction of vesicle volume to a certain extent.