致密砂岩层内非均质性及含油下限——以鄂尔多斯盆地三叠系延长组长7段为例  

Heterogeneity and lower oily limits for tight sandstones:a case study on Chang-7 oil layers of the Yanchang Formation,Ordos Basin

作　　者：崔景伟[1] 朱如凯[1] 吴松涛[1] 王拓[1] 

机构地区：[1]中国石油勘探开发研究院,北京100083

出　　处：《石油学报》2013年第5期877-882,共6页Acta Petrolei Sinica

基　　金：国家重大科技专项(2011ZX05001);博士后科学基金(2012M510481)资助

摘　　要：致密油成为世界石油勘探领域一大亮点并显示出巨大勘探潜力,中国致密油分布广且具独特地质特征。通过鄂尔多斯盆地三叠系延长组长7油层组岩心观察,发现层内单砂体级别上存在较强含油非均质性,利用薄片、氯仿沥青抽提、场发射扫描电镜、微米CT、高压压汞、N2气体吸附以及砂岩X射线衍射(XRD),对非均质性砂岩成岩特征、含油性、微观孔喉、孔径分布以及岩石矿物组成进行分析。结果显示:钙质胶结是导致致密砂岩储层非均质性的原因;残留烃含量相差约6倍;致密砂岩均主要发育纳米级喉道(直径<1μm)。根据残留含油量和介孔平均孔径以及含油量与孔隙度的图版,认为介孔平均孔径15nm、孔隙度2%可能是致密油的含油下限,该认识将对非常规致密油的勘探选区和资源量计算提供依据和参考。The tight oil exploration has made a great breakthrough in USA （Eagle Ford, West Bay Basin and Bakken, Willis Basin） and been in the spotlight worldwide for its huge potential prospect. China has a wide distribution of tight sandstones. Through care- ful observations of core samples from Chang-7 layers of the Triassic Yanchang Formation from some dozens of wells in the Ordos Ba- sin, we come to realize that obviously oily heterogeneity exists in these tight sandstones, especially in intrabed single sand body. Dif ferent oily sandstone samples were collected from the Triassic Yanchang Formation for comparison study and analytical techniques in- cluding thin section, chloroform bitumen, field emission SEM, micro-CT, high pressure Hg injection, N2 adsorption and sandstone XRD were performed on them. Diagenetic features, oiliness, microspores and throats, pore size distributions, specific surface areas and mineral compositions of these tight sandstones were obtained. The results show that the heterogeneity of reservoirs may result from calcareous cementation and tight sandstones tend to mainly develop nano-throats （diameter^l/~m）. According to plates of the residual oil content versus the average pore diameter of mesopores and the oil content versus porosity, 15nm of the average aperture of mesopores and 2% of porosity may be regarded as lower oily limits for tight sandstones, and these criteria can provide a reliable reference for exploration target selection and resource assessment of the unconventional tight oil.

关 键 词：鄂尔多斯盆地 延长组长7油组 致密砂岩 储层非均质性 含油下限 

分 类 号：TE122[石油与天然气工程—油气勘探]