应用伽马测井曲线小波变换计算粒度参数

伽马测井曲线包含了储层的粒度信息,采用二进制小波变换对伽马测井曲线处理可以提取粒度参数。通过分析不同粒度区间单位体积含量(以Udden-Wentworth方案为标准)与伽马测井曲线变换后信号的幅度、频率之间关系,考虑测井仪器探头测量速率造成的采样间隔的影响,建立求解不同粒度区间体积含量的递归方程组。将获得不同粒度区间的绝对体积转化为相对体积含量,按照Trask或Folk-Ward公式,计算粒度中值、平均粒度、分选系数、偏度、峰度。选择塔里木盆地大北地区DB101等4口井51个取样点进行方法适用性和可靠性验证,此方法的计算结果与筛选法相比,各项参数误差均在允许接受范围内。与国内外同类方法相比,此方法在信息来源、耗时、成本方面的要求均有所降低。

Application of Gamma Curves Wavelet Transform to Calculate Grain Size Parameters

The information on grain size of reservoirs from gamma logging curves can be obtained and the grain size parameter can be extracted based on the dyadic wavelet transform.Considering the influence of sampling intervals caused by the measurement rate of logging tools,an algorithm for solving the system of recurrence equations concerning volume fraction in different kinds of grain size distributions was presented through analyzing the content by volume in different kinds of grain size distribution and the relationship between range and frequency of signal which was extracted after gamma logging curves changed.On the basis of this algorithm,the absolute volume content in different kinds of grain size distribution can be transformed into the relative volume fraction.Then the grain size parameters can be calculated including the median grain diameter,the average particle size,the sorting coefficient,the skewness and the kurtosis according to Trask or Folk-Ward formulae.Four wells like DB101 in Dabei area of Tarim Basin were selected to verify the applicability and reliability of this method.Moreover,compared with the sieve method,all kinds of parameter errors are within an acceptable range.The advantage of this method is that it can reduce the demand for the source of information,timing consuming and cost in contrast to the similar methods at home and abroad.