鄂尔多斯盆地长9烃源岩发育与排烃效率

鄂尔多斯盆地长9优质烃源岩主要集中在志丹—英旺地区,但目前仅在志丹地区发现了典型长9源岩所生原油。对源岩排烃效率的定性和定量研究表明,英旺地区长9烃源岩排烃效率明显低于志丹等其他地区,仅为44%,其余地区平均为82%。排烃效率低应是英旺地区长9原油勘探未能取得突破的重要原因。沉积埋藏史和测井资料研究证实,与其他地区相比,英旺地区地质时期所经历的最大埋深明显较小,由此造成源岩孔隙度较高,残留烃量较大,导致英旺地区排烃效率低。另外,与志丹地区相比,英旺地区单位源岩生烃量较小,由此会造成其残烃量相对较高,这也是造成英旺地区排烃效率较低的一个原因。

Development and Hydrocarbon Expulsion Efficiency of Source Rock in 9th Member of Yanchang Formation,Ordos Basin

The good quality source rock of 9th member,Yanchang Formation,is mainly distributed in Zhidan-Yingwang area,Ordos basin.But the typical oil from source rock of the 9th member has been only found in Zhidan area.Therefore the expulsion efficiency of hydrocarbon from source rock of the 9th member was researched qualitatively and quantitatively in this paper.The result indicates that the expulsion efficiency of hydrocarbon from source rock of the 9th member in Yingwang area is obviously lower than those of other areas(e.g.Zhidan area).It is only 44%,and the average value of those of other areas is 82%.The low expulsion efficiency of hydrocarbon should be an important reason that no breakthrough has been made in the exploration of oil from source rock of the 9th member in Yingwang area.The research of burial history and logging data proves that,compared with other areas,the biggest buried depth of Yingwang area in geologic time is less than those of other areas,which causes high porosity and preservation ability of hydrocarbon.This is the primary reason for the low expulsion efficiency of hydrocarbon of Yingwang area.In addition,compared with Zhidan area,the hydrocarbon generation amount of Yingwang area is relative little,and the residual hydrocarbon amount is relative much consequently,which is the other reason that the expulsion efficiency of hydrocarbon from source rock of the 9th member in Yingwang area is low.