一种识别异常中子、密度孔隙度测井曲线新方法:以中东W油田Mishrif储层为例

A New Method for Identifing Abnormal Neutron and Density Logging Curves:An Example from Mishrif Reservoir in the Middle East W Oilfield

测井曲线质量检查是储层测井评价必不可少的一个环节。在评价中东W油田Mishrif储层的过程中,声波曲线频率图峰值都近似一致,但相邻几十口井的密度曲线测量值偏高,中子曲线测量值偏低,密度和中子曲线交会所得到的孔隙度比声波计算的孔隙度要小,在井数较多的情况下利用频率图来检查曲线质量是个巨大的耗时工程。基于此,研究了一种自动识别异常中子、密度曲线的新方法,即利用中子、密度曲线重构一条新曲线,通过该曲线与正常声波曲线之间的距离大小来自动识别具有异常曲线的井,结果表明当该值大于或等于0.4时,中子、密度曲线正常,反之则异常。在自动识别异常曲线之后,结合曲线在测井道上的刻度与响应特征,根据前人校正的不足又提出了新的校正方法,引入新的校正公式,将异常中子、密度曲线校正到正常的位置,校正后的中子、密度曲线交会得到了合理的总孔隙度。

Quality inspection of logging curve is a necessary part in the reservoir evaluation.The peak frequencies of sonic cures are approximately consistent,but the density value is on the high side and neutron curve is on the low during the evaluation of the Mishrif reservoir of the Middle East W Oilfield.However,to check the quality of the curves in the case of more wells is a huge time consuming project.Hence,a quick method that checks abnormal density and neutron logging curve is proposed to reconstruct a new curve by combining density and neutron logging curve,then calculating the distance between new curve and the sonic curve to automatically identify abnormal curves.The result shows that when the value is equal to or greater than 0.4,the curve is normal,abnormal conversely.A new calibration method is proposed and a new correction formular is introduced because of the inadequacies of the previous calibritions combining the scale and response characteristics of the logging curve after the automatic identification of abnormal curves.In this way the abnormal neutron and density logging curve is adjusted to the normal position and the reasonable total porosity is obtained.