川东北长兴组——飞仙关组古原油成藏的孔隙度门限  

Porosity Threshold for Paleo-Oil Accumulation of Changxing—Feixianguan Formations in the Northeastern Sichuan Basin

作　　者：余新亚 李平平[1] 邹华耀[1] 王广伟[1] 

机构地区：[1]中国石油大学(北京)地球科学学院,北京102249

出　　处：《地质学报》2014年第11期2131-2140,共10页Acta Geologica Sinica

基　　金：国家科技重大专项(编号2011ZX05005-003-009HZ);中国石油科技创新基金研究项目(编号2011D-5006-0104);国家自然科学基金项目(编号41103020)资助的成果

摘　　要：近年来,在四川盆地二叠系、三叠系海相碳酸盐岩层系中发现了如普光、龙岗、元坝等多个大中型、高孔高渗气田,且天然气主要为古油藏原油裂解气.在油源充足的条件下,孔隙度成为了控制古原油成藏的关键因素,讨论古原油充注的孔隙度门限,尤其对于致密碳酸盐岩储层是否发生古原油的聚集具有指导意义.川东北地区长兴组-飞仙关组礁滩相储层发现了大量的固体沥青,岩石薄片镜下观察到这些固体沥青主要分布于亮晶鲕粒灰岩的粒间孔隙中、结晶白云岩的晶间孔中以及残余鲕粒白云岩的铸模孔中,极少发现沥青充填之后的胶结物.本研究定量统计了沥青含量与现今面孔隙度来恢复视古孔隙度,分别讨论现今面孔隙度、视古孔隙度与沥青含量的关系,确定了视古孔隙度门限,最后经过压实作用校正得到了古原油成藏的孔隙度门限.研究结果揭示,沥青含量与现今面孔隙度无线性关系.而与视古孔隙度有着较明显的正相关关系,当视古孔隙度大于一定值时,沥青含量显著增加;川东北长兴组-飞仙关组碳酸盐岩储层古原油成藏的孔隙度门限值为6.4％～7.4％（平均6.8％）.In recent years, the Permian and Triassic marine carbonate strata of Sichuan Basin have been found to host many medium-size, high porosity and permeability gas fields, such as Puguang, Longgang, Yuanba, with natural gas mainly being oil cracking gas. Porosity becomes a key factor in controlling paleo-oil accumulation on condition that the oil source is sufficient. Discussion of threshold value of paleo-oil charging has guiding significance, especially for the tight carbonate reservoir. A large amount of solid bitumen was discovered within Changxing Feixianguan Formations reservoir in northeastern Sichuan basin. Cross section observation indicates that the solid bitumen mainly fills interparticle pores of sparry oolitic limestone pores, crystalline dolomite intergranular pores and residual oolitic dolomite moldic pores, and no post-bitumen cements have been observed. In this study, the solid bitumen content and present porosity were quantified, and their sum was approximately visual paleo-porosity. The relationship between bitumen content and present porosity, bitumen content and visual paleo-porosity were discussed, respectively, and the visual paleo-porosity threshold was determined. Finally, the porosity threshold for paleo-oil accumulation was obtained using correction after compaction. The results reveal that solid bitumen content was irrelevant to present porosity, while a positive relationship with visual paleoporosity. When paleo-porosity excesses a certain value, bitumen content increases significantly. The porosity threshold value of Puguang gas field Changxing and Feixianguan Formations, Yuanba gas field Feixianguan Formation and Jiannan gas field Feixianguan Formation is around 6. 4% - 7. 4% with an average of 6.8%.

关 键 词：孔隙度门限 视古孔隙度 沥青含量 压实作用 川东北 

分 类 号：P618.13[天文地球—矿床学]