基于阵列声波测井的海陆过渡相碎屑岩地层裂缝识别方法

针对海陆过渡相致密碎屑岩地层裂缝测井识别难度大的问题,提出结合Gassmann方程、自适应基质矿物及骨架模量提取方法及DEM理论模型,利用阵列声波测井资料对海陆过渡相碎屑岩地层单井裂缝发育段进行定量识别的方法。研究结果显示,提取的碎屑岩地层岩石基质矿物体积模量Ko分布在13~58 GPa,岩石体积模量Ks和干岩石骨架体积模量Kd略小于Ko;地层岩石基质矿物剪切模量μo分布在5~18 GPa,岩石剪切模量μs略小于μo;利用自适应方法可对地层横波时差进行有效预测,相对误差为3.5%;将采用自适应方法提取的模量参数代入DEM理论模型,可实现对地层裂缝的预测,该方法的识别效果明显好于常规测井、裂缝参数法、多因素概率判别法及R/S法等常规裂缝识别方法。研究表明,提出的新识别方法其计算结果与实际值的吻合度高,裂缝识别结果可靠。 

Fracture Identification Method for Marine-Continental Transitional Clastic Rocks Based on the Array Acoustic Logging

It is much more difficult to identify fractures in marine-continental transitional facies tight clastic rocks from well logging,so a study was proposed to carry out quantitative identification on single-well fracture development sections in marine-continental transitional facies clastic formations by using array sonic logging data, combined with the Gassmann equation, adaptive matrix mineral and skeleton modulus extraction method, and DEM theoretical model. It is shown that the extracted Ko(matrix mineral bulk modulus of clastics)ranges from 13 to 58 GPa, which is slightly higher than Ks (bulk modulus)and Kd (dry rock skeleton bulk modulus), and μo(matrix mineral shear modulus) ranges from 5 to 18 GPa, which is slightly higher than μs (shear modulus). Shear wave time difference can be predicted effectively with relative error 3.5% from adaptive method. Fractures can be predicted by introducing modulus parameters extracted by the adaptive method into the DEM theoretical model, and its coincidence rate is apparently superior to that of the conventional logging method, the fracture parameter method,the multi-parameters probability discriminance method and the R/S method. In conclusion, the newly proposed fracture identification method is reliable, with its calculation results highly coincident with practical value.