约束最小二乘法在低含油饱和度油藏评价中的应用

Application of Constrained Least-Squares-Algorithm Evaluation for Low Oil Saturation Reservoirs

A井区八道湾组低含油饱和度油藏的孔隙结构、岩电关系复杂,导致测井评价中传统阿尔奇公式计算的流体饱和度精度较低。为实现饱和度的精确计算,以阿尔奇公式计算电阻率误差为目标函数,将需要设定m、n值的传统阿尔奇公式计算转化为信赖域方法求解,通过带m、n值约束的非线性最小二乘法计算出储层的含水饱和度。在实际测井资料的处理解释中,根据基于m、n值约束的流体饱和度计算结果判别的油水层,与试油结论较为吻合,解释符合率达85%以上。研究结果表明,该文提出的方法可精确计算流体饱和度,适用于低含油饱和度油藏的含水饱和度计算。

The complex pore structure and petroelectric relationship of the Badaowan formation reservoir in block A lead to the low accuracy of fluid saturation calculated by traditional Archie’s formula in log evaluation.In order to achieve the accurate calculation of saturation,the resistivity error calculated by the Archie’s model is used as the objective function,the traditional Archie’s formula calculation that needs to set the m and n values is transformed into the trust region method to solve.Then a nonlinear least squares optimization algorithm calculation with the m and n value constraints is used to calculates the water saturation of the reservoir.In the processing and interpretation of actual logging data,the oil and water layers identified by the fluid saturation calculation results based on the constraints of m and n values are in good agreement with the oil testing conclusions,and the interpretation coincidence rate is over 85%.The research results show that the method proposed can accurately calculate the fluid saturation and is suitable for the calculation of water saturation in low oil saturation reservoirs.