鄂尔多斯盆地长7段有机地球化学参数对致密油动用效果的响应

Response of organic geochemical parameters of Chang 7 member to the effect of tight oil utilization in Ordos Basin

致密油层压裂效果及油气动用情况的评价指标和判识手段一般具有地区适用性。选取热解参数S1/ST、PI值与饱和烃分子组成参数∑C20-/∑C21+、∑三环/∑五环、Pr/n C17、Ph/n C18对水平井开发目标层位长72亚段及相邻层位长71亚段和长73亚段进行比对,分析其实施压裂后致密油的动用效果。结果显示,参数∑C20-/∑C21+、∑三环/∑五环的比值存在明显分异;Pr/n C17、Ph/n C18参数也敏感地反映了原油直链和支链烷烃分子的差异渗流特征,表现为分子结构简单的轻组分相对含量在目标层位中明显降低。综合各有机地球化学指标特征,认为目标层位长72亚段的致密油受到优先动用,但采出程度不大。研究结果为鄂尔多斯盆地致密储层油气动用层位的精细判识提供了有效的敏感参数。

The evaluation index and identification methods of the tight oil fracturing and oil-gas utilization differentiate with different areas.This study extracted pyrolysis parameters S1/ST,PI and saturated hydrocarbon molecular composition parameters∑C20-/∑C21+,∑tricyclic/∑pentacyclic,Pr/n C17and Ph/n C18for comparison between the target horizon Chang 72and neighboring horizons Chang 71and Chang 73.The result indicates that there is an obvious variation in∑C20-/∑C21+and∑tricyclic/∑pentacyclic.Meanwhile,Pr/n C17and Ph/n C18sensitively reflect the difference in percolation characteristics of linear and branched alkane.The above organic geochemical parameters are consistently conducted as follows:the relative content of light components with simple structure is significantly reduced in the target layer.Collaborative analysis of multiple organic geochemical parameters showed that the dense oil of the target horizon(Chang 72)was used preferentially,but it is not used much.This study believes that the characteristics of the organic geochemical parameters of tight reservoirs can provide a basis for the fine identification of the use of tight oil.