摘要
"双峰系统"结构碎屑岩中随着泥质含量(V_(sh))从0到100%的变化过程中,岩石的孔隙度先降低,后增加。在V_(sh)较低及较高时,岩石的孔隙度会出现两个高峰,但岩石渗透率却随V_(sh)的增加而一直降低。因此出现的两个孔隙度高峰分别对应高孔高渗砂岩及高孔低渗泥页岩。该现象可以由砂-泥质颗粒充填模型进行合理解释。通过对川西三叠系须家河组须五段地层的致密砂岩及泥页岩进行物性、声学测试、大量薄片观察统计及测井分析,认为该地层碎屑岩具有明显的"双峰系统"结构特征,在V_(sh)约为35%时,岩石物性最差。所研究泥页岩中微裂缝较为发育,这是造成其物性相对较好的重要原因。由于所研究碎屑岩地层砂泥岩频繁互层,岩性变化较快,常规自然伽马方法并不能准确评价地层岩石V_(sh),采用三孔隙度模型对地层V_(sh)进行预测,取得了较好的评价效果,平均绝对误差为6%。该研究对陆相致密碎屑岩储层评价、岩石力学研究及工程施工设计等方面均有一定参考价值。
“Bimodal system” structure means the atmosphere that with the increase of shale content from 0 to 100% of clastic rocks , rock porosity first decrease and then increase . There are two rock porosity peaks when the shale content is low and high. But the rock permeability reduces continuously with the increase of shale content. Then the two rock porosity peaks correspond high porosity and high permeability sandstones and high porosity but low permeability shales. This phenomenon can be well interpretated using the sand- shale grains filling model. By physical property and acoustic testing, thin sections observation and statistics and logging analysis of the sandstone and shale of Triassic Xujiahe group Xuwu section in the Western Sichuan Basin, it is found out that this clastic strata has obvious “Bimodal system” structure. When the Vsh is about 35%, the rock petrophysical properties are the worst. Microfractures are developed in the study shales, which is an important cause that shales’ physical properties are relatively good. Because sandstones and shales are interbed frequently, and their lithologies change quickly, conventional natural gamma ray methods can not accurately evaluate Vsh of the study rocks. In this paper , we adopt three porosity model to predict the formation Vsh , and a better evaluation effect is obtained,with the average absolute error is 6%. The study in this paper has certain reference value in continental tight clastic rock reservoir evaluation, rock mechanics research and engineering construction design etc..
出处
《科学技术与工程》
北大核心
2016年第22期28-35,共8页
Science Technology and Engineering
基金
国家科技重大专项(2016ZX05037)资助
关键词
“双峰系统”
陆相致密碎屑岩
泥质含量
实验分析
三孔隙度模型
“Bimodal system”
continental tight clastic rock
shale content
experimental analysis
three porosity model
