塔里木盆地玉北地区奥陶系储层构造裂缝定量预测

THE QUANTITATIVE PREDICTION OF STRUCTURAL FRACTURES IN ORDOVICIAN RESERVOIR IN YU-BEI AREA,TARIM BASIN

在应用有限元法对塔里木盆地玉北地区不同裂缝发育期古构造应力场进行数值模拟的基础上,根据岩石破裂准则及应变能守恒,构建裂缝参数与构造应力间定量模型,开展储层裂缝定量预测。研究结果表明:玉北地区奥陶系储层内部裂缝以构造缝为主,其发育受构造位置控制作用明显,主要在加里东晚期—海西早期及海西晚期发育,加里东晚期—海西早期裂缝密度主要介于0.04～0.2条/m之间,海西晚期裂缝密度主要介于0.2～2.0条/m之间,且海西晚期构造运动对早期裂缝改造作用明显,受海西晚期构造运动改造,早期裂缝开启性明显提高,裂缝开度平均提高78.6%;加里东晚期—海西早期及海西晚期两期裂缝继承性发育区,裂缝发育程度及开启性高,更有利于油气运移与聚集,为油气富集有利区。

Based on the finite element method,the numerical simulation of the paleo tectonic stress field in different fracture development stages in Yu-bei area was carried out.Further more,according to the rock failure criterion and strain energy conservation,the fracture parameters were calculated based on the quantitative relationship between the stress and fracture.The results show that the fractures in Ordovician reservoirs in Yu-bei area are mainly structural fractures,and their development are obviously controlled by the structural position.The structural fractures mainly developed in late Caledonian-early Hercynian and late Hercynian period.The fracture density is dominant between 0.04~0.2 strip/m in late Caledonian-early Hercynian,and between 0.2~2.0 strip/m in late Hercynian.The stress in late Hercynian has an obvious influence on the early fractures.With the influence of structural movement in late Hercynian,the aperture increased obviously by 78.6%on average.The fractures developed both in late Caledonian-early Hercynian and late Hercynian have high density and aperture,which are more favorable for hydrocarbon migration and accumulation as potential oil and gas enrichment area.