感应-横向组合测井联合反演及多解性研究

电阻率测井反演问题解的局部收敛性和非唯一性增加了测井解释的难度，影响了实际的应用，把测量原理迥异的感应型和电流型测井结果联合起来反演，是减小这些影响的有效方法，利用经测井理论和反演技术，建立了适用感应－横向组合测井响应的联合演算法，研究了单一的横向测井反演的感应－横向联合反演的局部收敛性、非唯一性及解的偏差，结果表明，联合反演更有利于同时确定地层电阻率、侵入半径和侵入带电阻率，当初值地较大范围内变化时，反演结果均能在真值或真值附近收敛，改善了反演结果的局部收敛性，增加了反演结果的可信度，避免了差异较大乃至相互矛盾的解，现场实例证实了这一结论。

JOINT INVERSION FOR COMBINING INDUCTION- AND DEPARTURE-LOGS

For resistivity logging inversion, local convergence and non unique solutions make logging interpretation become difficulty. Both they have negative effects on field applications. The problems is proposed to be solved by joint inversion through combining induction and galvanic-logging tools that have different measurement principles. A joint inversion algorithm for induction and departure logs is suggested using resistivity logging theory and inversion technique. The local convergence, non-unique solutions, and the deviation are discussed for departure logging inversion and joint inversion respectively. It is indicated that the joint inversion is more reasonable to the estimation of formation resistivity, invasion depth and invasion zone resistivity. The solutions of joint inversion converges to true values of model even though the initial guesses vary within a wide region. Joint inversion technique causes that the local convergence is improved greatly, hence the calculation results become more reliable. The solutions with much difference or contradictious solutions could be avoided by using joint inversion. Field applications proved these conclusions.