鄂尔多斯盆地延长组致密油储集层特征研究

Reservoir characteristics of Yanchang Formation tight oil reservoirs in Ordos Basin

为深入研究分析储层储集特征,通过大量的岩心观察、岩石薄片和室内实验,结合扫描电镜、常规压汞和核磁共振等进行分析。结果表明:鄂尔多斯盆地研究区致密油层页岩中主要矿物为粘土矿物、石英与长石,此外还含少量碳酸盐和黄铁矿。泥质页岩内刚性颗粒的粒度平均值为5.4μm,不存在砂级颗粒,泥级颗粒(≥8)能够占到中颗粒的50%以上。页岩、纹层和含纹层页岩的总有机碳含量(TOC)差异性较为明显,表明页岩的TOC存在较强的非均一性。粉砂质纹层中页岩气所占据的含气孔隙度要比页岩层大,孔隙发育特征主要以粒/晶间孔和粒内孔为主,洗油前孔隙度为0.27%~8.06%,说明变化范围较大,平均2.35%。长7致密油储层大孔至纳米孔孔隙均含油,且微孔至纳米孔孔隙含油饱满。

In order to study and analyze the reservoir characteristics in depth,a large number of core observations,rock thin sections and laboratory experiments were combined with conventional mercury injection and nuclear mag⁃netic resonance to conduct analysis.The experimental results show that the main minerals in the tight oil shale in the Ordos Basin are clay minerals,quartz and feldspar,in addition to a small amount of carbonate and pyrite.The average particle size of the rigid particles in the argillaceous shale is 5.4μm.There are no sand-grade particles,and mud-grade particles(≥8)can account for more than 50%of the medium particles.The differences in TOC among shale,laminar and laminar shale are obvious,indicating that the TOC of shale has strong heterogeneity.The gas-bearing porosity occupied by shale gas in silty laminae is larger than that in shale layers,and the pore develop⁃ment characteristics are mainly granular/intercrystalline pores and intragranular pores.The range of porosity before oil washing is large,from 0.27%~8.06%,with an average of 2.35%.The macropores to nanopores of Chang 7 tight oil reservoirs all contain oil,and the pores from micropores to nanopores are full of oil.