Unconformable eroded thickness recovery by cycle analysis method

FAN Jie; JIANG Youlu; CUI Xiaojun; ZHU Jianfeng; CHEN Xingxia

Abstract：As an essential part in the study of basin structural evolution and hydrocarbon accumulation,the eroded thickness recovery is significant in the assessment of hydrocarbon generation,migration and preservation.Based on previous studies and wave theory,a cycle analysis method taking the variation tendency of deposition rate as research object was put forward.It presumes that there are approximate sine waves between strata deposition rate and geologic ages;the period,wave crest and wave trough all satisfy the linear gradient changing rule.By spectral analysis of wave cycles,the deposition rate of the erosion period was obtained.Then the original strata thickness was derived by the discrete sum of deposition rate to time,so as to calculate the unconformable erosion thickness.The cycle analysis method was applied to a case analysis of Longfengshan area,Changling faulted depression,Songliao basin to recover the erosion thickness of Denglouku formation (K1d) and Yingcheng formation (K1yc) single wells.Then the self-verification method,mudstone sonic log interval method and homogenization temperature of fluid inclusion method were applied to calculate the original strata thickness and erosion thickness.The results show that the calculation errors by cycle analysis and other three methods are all within 10％,indicating that the new method is practical and accurate.