油气储层砂岩样品制冷—加热循环解离技术实验研究

Experimental investigation on sandstone sample disaggregation using a repetitive freezing and thawing technique

制冷—加热循环解离技术(简称冷冻技术)是自生伊利石分离提纯过程中制备黏土悬浮液的一项新技术。利用批量典型样品对该项技术的解离效果及其影响因素进行了详细研究,并与常规湿磨技术进行了系统对比。与湿磨技术相比,冷冻技术既有优越性,也有局限性。优越性主要表现在剔除碎屑钾长石效果略微偏好和实测年龄数值相对偏小方面;局限性主要表现在解离效果变化较大,部分砂岩样品相对较好,部分砂岩样品则相对较差,样品埋深是影响解离效果的最主要因素,炭屑(薄煤层)、泥质含量以及是否含油等对解离效果具有明显控制作用。冷冻技术对于坚硬程度中等的中浅层或中深层砂岩效果较好,具有较好的应用前景;而对于坚硬程度较高的深层或超深层砂岩则效果较差,甚至不宜采用。研究还表明,湿磨仍不失为制备黏土悬浮液的一种行之有效的实用技术,简便快捷并且效果较好,具有较好的应用前景。

A repetitive freezing and thawing disaggregation technique, simplified as freezing technique, is described. The freezing technique is a new method for preparing clay suspension during the separation and enrichment of authigenic illites from reservoir sandstones. The disaggregating effects and the controlling factors have been investigated in detail using typical sandstone samples, and compared with a wet grinding technique, as a conventional disintegration method. Comparing with the wet grinding technique, the freezing technique has advantages and disadvantages. The freezing technique is more effective to avoid detrital potassium feldspar contamination. The obtained authigenic illite K-Ar ages are more reliable as void of detrital contamination. Sample disintegration time is mainly related to porosity and permeability and long disintegration timeframes can be a disadvantage for well cemented sandstone samples. The buried depth of the sandstone samples is the main controlling factor, as well as the shale content and organic content comprising coal seams or residual oil films or bitumen coatings. The experimental results show that the freezing technique can be used to disaggregate less consolidated or medium cemented sandstones mainly related to variable shallow to medium depths ranges. For well cemented and deeply buried sandstones with low porosity and permeability ranges, the method is less suited as long disintegration timeframes of several months or years are required. The experimental results also show that the wet grinding is still a practical and effective technique for preparing clay suspension, with the advantages of easyoperation, celerity and better effects, and has very bright application futures.