基于HDIL的裂缝性砂岩地层响应特性研究

Study on response characteristics of fractured sandstone formation based on HDIL

由于在裂缝性低孔砂岩地层中,天然微裂缝发育,且高压钻井条件下易导致井筒周边产生人造裂缝,如诱导裂缝,很容易受到泥浆的侵入,且侵入较深(泥浆漏失),导致测得的测井曲线异于一般地质下的测井曲线,因此,为了进一步提高测井解释精度,为测井解释提供理论依据,本文采用HDIL高分辨率阵列感应测井仪器对裂缝响应特性进行研究。利用COMSOL正向建模工具,计算分析泥浆的类型、裂缝的张开度对HDIL高分辨率阵列感应测井仪器响应特性的影响。数值模拟结果表明,不同泥浆体系下,视电导率响应曲线变化趋势是一致的,幅值大小随泥浆电导率等比变化;裂缝张开度越大,响应特性越明显;短子阵列的视电导率曲线会出现“薄层层角现象”,张开度的增加以及泥浆电导率的增加会弱化“层角现象”。

Because in the fractured low-porosity sandstone formation,natural micro-fractures are developed,and under high-pressure drilling conditions,artificial fractures are easily generated around the wellbore,such as induced fractures,which are susceptible to mud intrusion,and the intrusion is deep(mud leakage),resulting in measurement obtained logging curve is different from the logging curve under general geology.Therefore,in order to further improve the logging interpretation accuracy and provide a theoretical basis for logging interpretation,this paper uses HDIL high-resolution array induction logging tool to study the fracture response characteristics.Use the COMSOL forward modeling tool to calculate and analyze the influence of mud type and fracture opening on the response characteristics of HDIL high-resolution array induction logging tools.Numerical simulation results show that under different mud systems,the apparent conductivity response curve changes in the same trend,and the amplitude varies proportionally with the mud conductivity.The larger the crack opening,the more obvious the response characteristic.The apparent conductivity curve of the short sub-array will change.There is a"thin layer angle phenomenon",and the increase in the opening degree and the increase of the mud conductivity will weaken the"layer angle phenomenon".