利用叠前弹性参数反演储层参数

塔中北斜坡带TZ45—ZG8井区下奥陶统鹰山组碳酸盐岩储层的主控因素为沉积环境及断裂,储层类型主要可分为孔洞型、裂缝型、裂缝—孔洞型和洞穴型4类,储层在地震剖面上多呈强振幅串珠状反射结构,表现为层状反射、星点状反射、断陷式反射3种地震反射特征。岩石物理分析及叠前AVO反演结果表明:纵波阻抗及密度对储层响应最为敏感,下奥陶统鹰山组储层表现为低纵波阻抗与低密度值;当储层含有油气时,远炮检距叠加数据振幅明显强于近炮检距叠加数据振幅,流体因子表现为高值,P.G属性剖面上表现为明显的正、负异常;当储层含水或被泥充填时,远、近炮检距叠加数据振幅变化不明显,流体因子相对储层含油气时值偏低,P.G属性剖面在储层段只有负异常。本文在岩石物理分析及AVO模型正演的基础上,通过叠前弹性参数反演预测储层的分布,通过叠前AVO分析预测流体的性质,提高了储层预测的精度。

Reservoir parameter inversion with prestack elastic parameter

Sedimentary environment and fracture are the master factors in areas of Well TZ 45 and Well ZG 8 of North Slope of Tazhong.The carbonate reservoir in Lower Ordovician Yingshan Formation could be divided into four types: hole type,fracture type,fracture-hole type and cavernous type.These types of carbonate reservoirs present strong bead-shaped reflections on seismic sections and seismic reflection patterns could be classified as layered reflection,dotted reflection and faulted reflection.Our petrophysical analyses and prestack AVO modeling indicate that P-Wave impedance and density are the most sensitive to reservoir response.The reservoir characteristics in Lower Ordovician Yingshan Formation are low wave impedance and low density.When the reservoir contains oil and gas,far offset amplitude is stronger than the near offset amplitude,and it correlates to high fluid factor and positive and negative abnormal on P·G attribute profile.When the reservoir contains water or mud,neither the far offset amplitude nor the near offset amplitude do not change significantly.Fluid factor is low,and P·G attribute profile shows only negative abnormal.Reservoir prediction has been improved by predicting the reservoir distribution with prestack elastic parameter inversion,and the fluid characteristics with prestack AVO analysis.