摘要
本文介绍了中子测井响应关系的数学模型及其计算方法和作用。用一个一元三次的函数关系式,能精确描述中子测井地层孔隙度φ与测井值J(计数率、计数率比值或API刻度值)一一对应的关系,其logφ-J响应关系呈“S”形曲线,精度误差≤0.5p.u。该数学模型的系数,通过中子测井模型井的实验数据,采用最小二乘拟合法,由计算机程序求出,并在补偿中子测井、井壁起热中子测井、中子伽玛测井影响因素研究及校正图版绘制中,发挥了重要作用。文中具体介绍了上述三种测井响应函数关系式,并认为可广泛应用于中子测井的量值传递以及仪器刻度和测井资料数学化、标准化中。
A mathematical model for neutron logging response, its computationprocedure and applications are presented. The relationship between formationporosity φ and neutron log measurements J (where J is the counting rateor ratio of counting rate, API calibrated) can be accurately expressed asa third order polynomial with one element. Log φ-J curve is in the shapeof 'S'. The resulted porosity has an error less that 0.5 p.u. By using theleast-squares fit the coefficients of the polynomial are computed from the experimental data obtained in neutron log modelling well. The applicationsof the mathematical model have proved its importance in study of envi-ronmental corrections and developed nomographs of charts for the compensatedneutron log, sidewall epithermal neutron log and neutron-gamma ray log.This paper suggest three response equations of the logs mentioned above andconclude that the mathematical model is applicable to measurement transfer,tool calibration, logging data digitizing and normalizing in neutron log.
