A Study On The Dipping-effect Correction Of An Array Induction Log

With the oil exploration and development needs, highly deviated wells have become an important direction of this field. When the dip angle is greater than30degrees, array induction logging curves will show an abnormal phenomenon in the formation boundary, and inaccurate amplitude of curve in the aim layer. They lead to erroneous results of data processing, so that take many difficulties of oil and gas interpretation and evaluation. This paper studies in detail the signal processing method of an array induction logging MIT in deviated wells. The results have a great practical significance for the application and popularization of MIT instrument in deviated wells.Firstly, induction logging theory of vertical wells and deviated wells is discussed. Array induction logging measurement principle and the geometric factor theory are given. The dipping volumetric geometrical factors and charge geometrical gactors are derived based on the analytical method and the finite difference method, respectively.Secondly, the response characteristics of array induction logs MIT in deviated wells are analyzed in detail. The characteristics of dipping volumetric geometrical factors and charge geometrical factors are analyzed respectively, which based on the analytical method and the finite difference method respectively. Results show that the volumetric geometric factor characteristics of the two methods are same, but charge geometric factor is different. The charge geometry factor which extracted directly from the numerical simulation formation model can describe the charge accumulation effect in the stratum boundary more accurate.The third part is the key part of this paper.Tthe deviated well signal processing theory based on geometric factor is studied in detail. After comparison of the advantages and disadvantages of dipping-effect correction method based on the analytical method dipping-bed geometrical factors and finite difference method dipping-bed geometrical factors, a new method of deviated well signal processing is proposed. The method combines the volumetric geometrical factors calculated from analytical method and charge geometrical factors calculated from finite difference method. It makes full use of the advantages of the two dipping-effect correction methods. The volumetric filter and charge filter are designed. The dip angle changes from0degrees to80degrees. The volumetric filter database is built. The conductivity is from0.001S/m to10.0S/m. The key problems in filter design are solved. They include choosing objective function, converting logging deep, constrainting filter and correcting the skin effect in deviated well. The algorithm which can process the actual logging data is complemented. The rawl measured signal filtered by volume and charge filter can eliminate the dipping-effect and get the same results with vertical well measurement curve.Last, according to the computer simulation for the models with different angle, different layer thickness and different resistivity contrast to confirm the effectiveness of the new method. The results show that the new method can effectively correct the dipping-effect in the measured data with dip angle less than70°The corrected curve and the straight curves coincide very well. Further improving, this method can be applied to the MIT’s deviated wells signal processing.