This study presents a novel interpretation model for reservoir characteristics while underbalanced drilling (UBD), by incorporating an unscented Kalman filter (UKF) algorithm in a three-phase variable mass flow model of oil, gas, and liquid. In the model, the measurement parameters are simplified to bottomhole pressure and liquid outlet flow, for decreasing the amount of the computation and time. By taking into account real-time measurements, the permeability and reservoir pressure along the well can be continuously updated. Three cases including single-parameter and double-parameter estimations have been simulated, and the performance is tested against the extended Kalman filter (EKF). The results show that single-parameter estimation of reservoir permeability or pressure achieves superior performance. The filtered values of bottomhole pressure and outlet flow trace the measured values in real time. When a new section of a reservoir is opened, the estimated reservoir permeability or pressure can always be quickly and accurately returned to its true value. However, it is not possible for the double-parameter estimation to obtain good results; its interpretation accuracy is low. UKF is superior to EKF in both estimation accuracy and convergence speed, which further illustrates the superiority and accuracy of the novel interpretation model based on UKF. Benefits from this model are seen in accurate bottomhole pressure and reservoir characteristic predictions, which are of major importance for safety and economic reasons during UBD and follow-up completion operations.

中文翻译：

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基于UKF的欠平衡钻井储层特征实时解释模型

本研究通过在油、气和液体的三相可变质量流模型中加入无迹卡尔曼滤波器 (UKF) 算法，提出了欠平衡钻井 (UBD) 时储层特征的新解释模型。模型中将测量参数简化为井底压力和液体出口流量，以减少计算量和时间。通过考虑实时测量，可以连续更新井沿的渗透率和储层压力。模拟了包括单参数和双参数估计的三种情况，并针对扩展卡尔曼滤波器（EKF）测试了性能。结果表明，单参数估计储层渗透率或压力具有优越的性能。过滤后的井底压力和出口流量值实时跟踪测量值。当油藏的一个新部分被打开时，估计的油藏渗透率或压力总是可以快速准确地恢复到其真实值。但是，双参数估计是不可能得到好的结果的；其解释准确率较低。UKF在估计精度和收敛速度上均优于EKF，进一步说明了基于UKF的新型解释模型的优越性和准确性。该模型的好处体现在准确的井底压力和储层特征预测中，这对于 UBD 和后续完井作业中的安全和经济原因非常重要。当油藏的一个新部分被打开时，估计的油藏渗透率或压力总是可以快速准确地恢复到其真实值。但是，双参数估计是不可能得到好的结果的；其解释准确率较低。UKF在估计精度和收敛速度上均优于EKF，进一步说明了基于UKF的新型解释模型的优越性和准确性。该模型的好处体现在准确的井底压力和储层特征预测中，这对于 UBD 和后续完井作业中的安全和经济原因非常重要。当油藏的一个新部分被打开时，估计的油藏渗透率或压力总是可以快速准确地恢复到其真实值。但是，双参数估计是不可能得到好的结果的；其解释准确率低。UKF在估计精度和收敛速度上均优于EKF，进一步说明了基于UKF的新型解释模型的优越性和准确性。该模型的好处体现在准确的井底压力和储层特征预测中，这对于 UBD 和后续完井作业中的安全和经济原因非常重要。双参数估计不可能得到好的结果；其解释准确率低。UKF在估计精度和收敛速度上均优于EKF，进一步说明了基于UKF的新型解释模型的优越性和准确性。该模型的好处体现在准确的井底压力和储层特征预测中，这对于 UBD 和后续完井作业中的安全和经济原因非常重要。双参数估计不可能得到好的结果；其解释准确率较低。UKF在估计精度和收敛速度上均优于EKF，进一步说明了基于UKF的新型解释模型的优越性和准确性。该模型的好处体现在准确的井底压力和储层特征预测中，这对于 UBD 和后续完井作业中的安全和经济原因非常重要。