欠平衡条件下深侧向测井响应校正方法

A correction method of deep laterolog responses under under-balanced logging condition

欠平衡钻井和欠平衡测井技术对于直接发现和保护油气层、提高单井产能和勘探开发成功率具有非常重要的意义。欠平衡测井时的井口装置与常规测井有很大的差别,需要对双侧向测井仪器的加长电极进行改造,使其长度缩短,以适应井口装置的长度,这一改造使得深侧向测井值明显降低,不能真实反映储集层电性。应用有限元素法计算了欠平衡条件下深侧向电极系系数随加长电极长度的变化规律,即加长电极越长,深侧向电极系系数越小。建立了欠平衡条件下深侧向测井响应的校正方法,并应用实际测井资料验证了校正结果的可靠性。该方法适用于任意长度的加长电极,可直接用于现场测井资料的预处理,校正后的深侧向测井电阻率可用于测井解释建模和油气定量评价。

Unde-balanced drilling and under-balanced logging are very important techniques for directly identifying and protecting hydrocarbon reservoirs and enhancing productivity. The wellhead assembly under under-balanced logging is greatly different from that under conventional logging. Therefore, the length of cable electrode for dual laterolog should be reduced to adapt to the wellhead assembly, which causes the deep laterolog responses to drop, and can not truly reflect the reservoir property. The rule of electrode coefficient varying with the cable electrode length under under-balanced condition has been computed using finite element method, that is, the longer the cable electrode, the smaller the electrode coefficient. The deep laterolog resistivity correction method under under-balanced condition is introduced. Field data examples are used to test the new method, and shows that this method is reliable. This method can be used to any length of cable electrode and can be applied to field pretreatment directly. The corrected deep latcrolog resistivity can be used in logging interpretation and quantitative hydrocarbon evaluation.