元素俘获能谱在深层致密储层评价中的应用:以松科2井为例

Application of elemental capture spectroscopy in deep tight reservoir evaluation:A case study of well SK-2

松辽盆地沙河子组存在多段气测异常,显示了该地层具有致密气勘探潜力,但研究区深层致密储层非均质性强、厚度薄、互层发育且类型多样。在松科2井常规测井曲线分析基础上,利用元素俘获能谱精细反演矿物组分含量,对地层岩性进行准确识别,并建立了元素交汇图识别出5种类型储层。结合岩石物理实验资料,得到地层的变骨架孔隙度、脆性指数、有机碳含量等储层评价参数,依据气测资料及综合评价指数将储层分为三大类。研究结果表明:沙河子组地层(3730~4500 m)孔隙度主要分布在5%~9%,脆性指数主要分布在45%~60%,临近烃源岩TOC含量普遍较高且累计厚度较大,识别出3798~3831 m、3950~3990 m、4150~4200 m是具有勘探开发潜力的有利致密气层段。利用元素俘获能谱评价致密气储层结果准确,能为深层致密气储层优选及压裂改造提供参考依据。

There are multiple gas logging anomalies in the Shahezi Formation,Songliao Basin,indicating its tight gas potential.However,deep tight reservoirs in the area have strong heterogeneity,thin thickness,interlayer development and various types.Based on the analysis of conventional well log of well SK-2,we used elemental capture spectroscopy(ECS)well logging to finely retrieve the mineral component content for accurate lithology identification,and subsequently identified five types of reservoirs by crossplot analysis.Combined with petrophysical experimental data,we further obtained the reservoir evaluation parameters such as variable skeleton porosity,brittleness index,and organic carbon content,which allowed us to categorize the reservoirs into three groups based on the well logging data and comprehensive evaluation indexes.In the Shahezi Formation(3730-4500 m),the porosity values range between 5%-9%,and the brittleness indexes range between 45%-60%.TOC of adjacent source rock is generally high,with relatively large accumulative thickness,and depth intervals at 3798-3831,3950-3990 and 4150-4200 m show favorable tight gas potential for exploration and development.We demonstrated in this paper that,ECS well logging can accurately evaluate tight gas reservoirs so as to provide a reference basis for fracturing optimization in tight reservoirs.