三肇凹陷青山口组地层压力分布特征评价及其石油地质意义OA

In the Songliao Basin,the Qingshankou Formation of the Sanzhao Depression is an excellent source rock that significantly influences the distribution of tight oil in the underlying Fuyu oil layer.However,research on the distribution characteristics and genetic mechanisms of overpressure remains relatively scarce.To clarify the developmental characteristics,dominant controls,and hydrocarbon geological implications of overpressure in the Qingshankou Formation of the Sanzhao Depression,well-logging data were first corrected using the TOC correction method.Subsequently,three primary pressure prediction methods were analyzed.Combining three diagnostic methods for overpressure genesis,we defined the distribution characteristics,genetic mechanisms,and dominant controls of overpressure.Finally,the relationship between overpressure in the Qingshankou Formation and the distribution of favorable zones in the underlying Fuyu oil layer was examined.These findings demonstrate that Eaton's method constitutes the optimal approach for current pressure evaluation in the Sanzhao Depression.Following TOC correction,the pressure evaluation accuracy achieved a 10%increase compared with the pre-correction results.The pressure distribution characteristics revealed moderate overpressure development in the Qingshankou Formation of the Sanzhao Depression,with maximum pressure coefficients of 1.3.The core area of the depression constituted the primary overpressure development zone.A synthesized analysis employing an integrated well-log interpretation,acoustic velocity-density crossplots,and Bowers'method confirmed that hydrocarbon generation expansion constitutes the primary genesis of overpressure in the Qingshankou Formation.By examining the relationships between overpressure and factors such as burial depth,source rock thickness,sand-mud ratio,and faults,it was found that formations with greater burial depths and thicker source rocks generated larger amounts of hydrocarbons.This leads to a greater overpressure caused by hydrocarbon generation and expansion,resulting in a positive correlation between burial depth,source rock thickness,and overpressure.Conversely,thicker sandstones and positions closer to faults are unfavorable for the preservation of hydrocarbon fluids,ultimately leading to a negative correlation between the sand and mud ratio,faults,and overpressure.Combined with the distribution characteristics of the Fuyu oil layer,this study explored the controlling effects of overpressure,sandstones,and faults on the distribution of tight oil in the Fuyu layer.This study aimed to lay the foundation for subsequent studies on the enrichment and accumulation of tight oil.