应力环境对克拉苏构造带盐下储层的影响

摘要

相同挤压背景下的相邻井区,由于区域应力的差异,造成了构造形态的不同,而构造形态又影响了地应力的分布.克拉苏构造带储集层白垩系巴什基奇克组储层非均质性强,构造位置间产量差异大,研究表明储层除了受沉积相控制外,地应力的大小及方向对储层的影响较大.基于挤压的应力环境将克拉苏构造带自北向南以克拉苏断裂为界分为斜向挤压区及水平挤压区.斜向挤压区的水平挤压应力、水平应力差、垂向应力较水平挤压应力区小.为了进一步验证测量应力值的准确性,利用离散元数值模拟的方法,以地震解释模型为基础,以实钻资料为约束,对构造演化过程中的断裂发育及应力、应变的分布特征进行了研究.模拟结果表明,水平挤压区与斜向挤压区的垂直应力相差较小,但水平挤压区的水平挤压应力较强,高出斜向挤压区30％～50％.强水平挤压应力对储层的影响具体体现在:储集层物性、储集空间、裂缝发育程度.代表斜向挤压区的克拉段,水平挤压应力小,储集层物性高,溶蚀现象显著,储集空间以原生孔隙为主,裂缝欠发育;水平挤压区的克深段,储集空间以粒间溶蚀扩大孔,粒内溶孔为主,储集层孔隙度低,岩性致密,裂缝极其发育,从微观薄片、岩心、FMI成像、微地震检测上均能发现大量规模性的裂缝,规模性裂缝极大地增强了克深段的储层连通性,提高了储集层渗流能力,保证了其在超过6000 m高应力储集层中仍存在日产百万方天然气的稳产高产井.%There are different structural patten between adjacent well areas under same compression background affected by the different regional stress.However,the structural form also affects the distribution of in-situ stress.Reservoirs of the Bashijiqike Formation in Kelasu thrust belt have strong reservoir heterogeneity,and there are large differences in yield between structural positions in this belt.Research shows that the reservoir is influenced by the magnitude and direction of in-situ stress in addition to the control of sedimentary facies.The Kelasu tectonic belt is divided into oblique compression zone and horizontal compression zone from north to south according to the size and direction of compression stress.The measured stress data show that the oblique compression zone has lower horizontal compression stress,lower vertical stress,and smaller horizontal stress difference than the horizontal compression zone.In order to further verify the accuracy of the measured data,the development of faults,the distribution characteristics of stress and strain in the process of tectonic evolution is simulated using the method of discrete element numerical simulation,based on the seismic interpretation model and constrained by the real drilling data.The result shows that the horizontal compression zone is slightly different from the oblique compression zone in vertical stress,but the horizontal compression zone has stronger horizontal compression stress,about 30％ ～50％ higher than the oblique compression zone.The effect of stress on the reservoir of strong horizontal compression is embodied in reservoir physical property,reservoir space and fracture development degree.The Kela segment which represents the oblique compression zone has low horizontal compression stress,high reservoir physical property,significant erosion phenomenon,less fracture and the reservoir space is dominated by primary pore.The Keshen segment which represents horizontal compression zone has low porosity of reservoir,cracks are extremely developed and the reservoir space is dominated by dissolution enlarge hole,intragranular dissolution pore.A large number of cracks from micro thin,core,FMI imaging,micro seismic detection can be found.The existence of cracks can enhance the connectivity of reservoir and improve the seepage capacity of reservoir.Therefore,it ensures that high and stable production wells in the deep,such as wells of one million cubic meters natural gas output per day in the high stress reservoir over 6000 m deep.