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文章首先在钻井液循环停止时井眼温度物理模型的基础上建立了数学模型，并用拉普拉斯变换法求得了热传导方程的解；然后，根据热传导方程的解建立了通过非线性反演法用电测的井眼温度来估算原始地温的数值方法；最后对地温估算模型进行了敏感性分析并研究了电测井眼温度对原始地温估算准确性的影响。建立的原始地温估算法不仅可以估算原始地层温度，而且还可估算：①钻井液循环停止时的钻井液温度；②热扰动半径；③垂直于井眼的地层热导率；④钻井液循环停止后加热井眼内钻井液的效率系数。使用该方法所需参数，一个是钻井液循环停止后测得的随时间变化的井眼温度，要求至少有两个以上的测量温度；另一个是循环停止时的地面钻井液温度。计算结果表明：在任何情况下都能准确估算原始地层温度和钻井液循环停止时的钻井液温度，而热扰动半径、热导率与钻井效率系数能粗略估计。

METHOD OF ESTIMATING INITIAL FORMATION TEMPERATURE BY ELECTRIC LOG HOLE TEMPERATURE

A mathematical model of initial formation temperature was set up on the basis of the physical model of hole temperature at the moment of no drilling fluid circulation, and the solution of thermal conduction equation was acquired by Laplace transform; then a numerical method of estimating initial formation temperature by electric log hole temperature through nonlinear inversion algorithm was obtained in light of such a solution; and then the sensitivity analysis of the formation temperature estimation model was carried out and the influence of the number of electric log hole temperatures on the accuracy of estimating initial formation temperature was studied. By use of the method, not only the initial formation temperature but also the following four parameters can be all estimated, i.e ① the drilling fluid temperature at the moment of no drilling fluid circulation; ②the thermal disturbance radius; ③the lateral formation heat conductivity; and ④ the efficiancy factor of heating drilling fluid in borehole at the moment of no drilling fluid circulation. The two kinds of temperature value are required in order to use the method: one is the borehole temperature value being changed with time, Which was measured for more than two times after the drilling fluid circulation had been stopped; and the other is the surface drilling fluid temperature value measured at the moment of no drilling fluid circulation. The calculation results indicated that the initial formation temperature and the drilling fluid temperature in borehole at the moment of no circulation can be accurately estimated in any conditions, but the thermal disturbance radius, heat conductivity and drilling efficiency factor may be roughly estimated only.(Financed by the opening up project (No.PLN9904) of the State Laboratory of Oil and Gas Reservoir Geology and Exploitation)