Combined with core and thin section observation,CT scan,image logging interpretation,the characteristics of structural fracture of Keshen5 gas pool in Kuqa depression of Tarim Basin were quantitatively characterized;the origin and validity of structural fracture were analyzed;and the spatial distribution regularity of structural fracture was predicted by numerical simulation of tectonic stress field.The results show that the structural fractures of Keshen5 gas pool are mostly high dip angle or upright ones and highly filled by calcite,in which the apertures distribute at 0-0.4 mm;microscopic fractures,in which the apertures mostly distribute at 20-30 μm,include grain-crossed fracture and mineral grain crack;in vertical,intensively developed sections and undeveloped sections of structural facture have the regularity of interphase distribution;there are three periods of structural fractures formed in Cretaceous,Paleogene and Neogene-Quarternary,respectively,in which the 3rd period of structural fracture is one of the key factors for industrial gas pool finally formed in Keshen5 area;palaeo-tectonic stress field determines the system characteristics and quantity of structural fractures,and the levorotatory shearing stress along boundary faults results in that the direction of tectonic stress and structural fractures changes from ～EW at southwest to ～SN at northwest of the anticline;present tectonic stress field generally would not form new fractures,but affects the effectiveness of pre-exist fractures;the high position of anticline has low linear density of structural fracture,but high aperture,porosity and permeability,therefore,the average gas production capacity of single well is also high correspondingly;in vertical,with the deepening of depth,the linear density of structural fracture increases while the effective aperture decreases,which means that the integrated development extent reduces;the controlling effect of unconformity on structural fracture validity is restricted within about 70 m.%综合采用岩芯及薄片观察、岩芯CT扫描及成像测井解释等方法,对塔里木盆地库车坳陷克深5气藏的构造裂缝进行了定量表征,在此基础上分析了构造裂缝的成因与有效性,并基于构造应力场数值模拟法对构造裂缝的空间分布规律进行了预测.结果表明:克深5气藏的构造裂缝以高角度和直立裂缝为主,岩芯裂缝开度为0～0.4 mm,多被方解石充填,微观裂缝包括矿物颗粒的穿粒缝和破裂纹,开度为20～30 μm;单井纵向上具有构造裂缝密集发育段和不发育段相间分布的特征;克深5气藏主要发育白垩纪、古近纪和新近纪—第四纪3期构造裂缝,其中第3期构造裂缝是克深5区块工业规模气藏形成的关键因素之一;古构造应力场决定了构造裂缝的组系特征和数量,沿边界断层的左旋剪切应力造成了构造应力方位和构造裂缝走向由背斜西南部的近EW向过渡为东北部的近SN向;现今构造应力场不产生新的构造裂缝,但会降低先存裂缝的有效性;背斜高部位的构造裂缝线密度较低,但开度、孔隙度和渗透率等较高,单井平均天然气产能相应也较高,纵向上随深度增加,构造裂缝线密度增大而有效开度减小;不整合面对构造裂缝有效性的控制作用主要局限在距不整合面约为70 m的范围内.
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