阵列侧向测井响应的多参数反演

Multi-parameter inversion of array laterolog responses

构建了二维阵列侧向测井多参数反演算法 .建立了侵入过渡带地层模型 ,该模型把径向地层分为井眼、冲洗带、过渡带和原状地层 ,其中过渡带的电阻率线性变化 ,可以较好地描述真实侵入过程的特性 .用修正阻尼最小二乘法对模型中的冲洗带电阻率、原状地层电阻率、冲洗带半径和过渡带半径 4个参数进行了反演计算 .结果表明 ,与传统阶跃模型相比 ,基于侵入过渡带地层模型的反演算法具有较好的稳定性和收敛性 ,减小了解对初值的依赖性 ,抑制了解的分布范围 。

A two-dimensional multi-parameter inversion algorithm for array laterolog is proposed. A four-parameter invaded transitional zone model is established, and in the model, formation is radially divided into four parts of borehole, flushed zone, transitional zone and original formation. The linear variation of the resistivity of the transitional zone realistically describes invasion process. Four parameters (the resistivity of original formation, resistivity of transitional zone, the radius of flushed zone and the radius of transitional zone) are inverted by using modified damped least square method. Compared with traditional step invasion model, the result calculated by this invaded transitional zone model has higher stability and faster convergence rate. This algorithm reduces the dependence of solutions on initial values, constrains the domain of solutions, and enhances the reliability of inversed results.