金湖凹陷卞东油田灰岩-砂岩混积岩储层应力场模拟及裂缝预测研究

Stress Field Simulation and Fracture Forecast in Lime-sandstone Diamictite Reservoirs of Biandong Oilfield in Jinhu Sag

金湖凹陷卞东油田阜二段储层为湖相灰岩与砂岩混杂沉积的特殊油气储层,该类储层为孔隙与裂缝双重介质储层,裂缝预测研究难度较大。通过应力场模拟来实现该类混积储层的裂缝预测。利用岩心声速法、压裂资料法、声发射法确定了研究区目的层地应力的方向和大小,选择适合目的层的力学参数,通过ANASYS软件实现地应力场模拟,研究区现今地应力场模拟结果显示,卞东油田地应力场中岩石三面受压。在研究区地应力场数值模拟基础上,利用应力场模拟结果参与裂缝参数计算,定量预测现今裂缝参数的空间分布。由于研究区为挤压应力环境的现今应力场,难于产生裂缝,所以研究区储层内发育的裂缝为地质历史时期产生的。古、今裂缝的线密度相同,但开度相差较大,现今裂缝比古裂缝开度要小。裂缝预测检验说明在湖相灰岩与砂岩混积岩储层中利用构造应力场数值模拟来定量表征裂缝具有较好的效果。

The E1f2 reservoir in Biandong Oilfield of Jinhu Sag was a special reservoir with lime-sandstone diamictite deposition.The reservoir was a reservoir with double media of porosity and fracture,and it was difficult for fracture forecasting.The fracture forecasting was performed by the stress field simulation.First,the core acoustic velocity method,fracturing data,acoustic emission method was used to establish the direction and size of stress in the studied area.And the rational mechanics parameters were chosen of the target zone,the ANASYS software was used to simulate the stress field.The results showed that rocks in the area were pressed from three-directions.On the basis of the stress field simulation of the area,the fracture parameters and forecasted distribution of fracture were deployed for quantitatively predicting the spatial distribution of fractural parameters.Because the current stress field was compressional stress field,so new fractures could not be created.So all the fractures were created in paleo-stress field,the current fracture and paleo-fracture had the same density with different apertures,the aperture of the current fracture was less than that of paleo-fracture.The examination of the fracture forecasting shows that better effect is obtained by using the stress field simulation to forecast fracture inthe diamictite reservoirs.