川东北部飞仙关组气藏气体组分成因研究

GAS COMPONENTS AND THE ORIGIN IN FEIXIANGUAN FORMATION GAS POOL,NORTHEAST OF SICHUAN

川东北飞仙关组气藏为高含硫、过成熟常压(低压)的超干气藏,其地层在地质历史上经过了深埋藏和高温作用,具备了原油裂解的条件,包裹体资料证明原始气藏含有大量的高烃组分和液态沥青,且不含H2S,确认气藏为原油裂解产物。气藏储层发育在膏盐岩中,原油裂解气与其中的硫酸盐矿物发生热化学还原作用(TSR),消耗了大量的高烃气体,并产生大量H2S和CO2,所以现今气藏表现为高含硫和过成熟特征。硫酸盐岩热化学反应(TSR)生成的H2S和CO2大量溶解在水中,形成大量的酸,其产生的溶蚀作用极大地提高了储集空间,造成了现在气藏压力较低的特点。

In northeast Sichuan Basin, Feixianguan Formation gas pools are rupewr-dry gas ones with lots of H2S, over-matured, and the pressure are normal or lower. The strata were embeded deeply and experienced high temperature in geologic history, the conditions that oil cracked into gas existed. The components of fluid inclusions prove the original Feixianguan Formation gas pool contains a lot C+2 hydrocarbons and liquid bitumen, but no H2S, and prove that the gas pool evolved from crude oil. The there was thermochemical reduction reaction between cracked gas and sulphate, consumed a lot C+ 2hydrocarbons, generated lots of H2S and CO2. So,the gas pool contain lots of H2S, and has over-matured character. TSR generated a lot acid, the acid eroded the reservoir and increased the pore space. Furthermore, a great lot of H2S and CO2 dissolved in water, so, the pressure of gas pool is lower.