| With the development of the petroleum industry, the logging technology of the horizontal well and the high angle deviated well tend to be perfect, but the well log analysis of the horizontal well is still backward in technique. The horizontal well response must be obtained by forward numerical modeling method, not uncomplicated signal processing. This paper researches the low frequency characteristics of the array induction logging instrument MIT in the horizontal well, which is very important for popularizing the utilization of the MIT in horizontal well logging.In this paper, fundamental theory of triaxial finite element is expounded amply and corresponding vectorial finite element equation set is derived. Secondly triple finite element fundamental theory is discussed,and wave equation of magnetic field of magnetic doublet source is expounded.By way of addition,Computing matrix is derived and established using variation principle, which is the same as the tradional method by way of adding coefficient elements to the row and column of coefficient array of equation set to realize package of coefficient elements. Then Real part and imaginary part wave equations is discussed, while symmetrical charactreristic is pointed out which can be used to solve the memory consumption during finite element computation. Put forward a method which is a kind of direct calculation3d magnetic field that is generated magnetic dipole source, which is a different from the traditional method choosing background conductivity that need to separate the background field and second field. Besides detailed computation process of finite element unit matrix is derived, and methods and some new technologies which are related to large sparse-linear equation set is introduced.Second based on common representation models, which are horizontal well of the two layers and three layer formation strata of symmetrical model, studied the response characteristics of the MIT. Based on two stratigraphic model, calculation and analysis the response of array induction logging instrument characteristics of the MIT. Under some influences such as instrument position, and the well diameter, the conductivities of should and mud, and points out that the instrument work in low frequency, its array5,6,7,8detection performance better than the array1,2,3,4. Under the influence of the instrument eccentric results, the response is analyzed, the results indicate that working under condition that the frequency of26.325kHz and the well drive for8in, MIT array1works better than other arrays seriously.At the end of this paper, studied the logging response of array induction logging instrumentMIT under the conditions of mud intrusion, and points out that under the invasion which issymmetrical and it’s conductivity is greater than strata conductivity, the array of1to7are subjectto the influence of different level, with eccentricity increase its conductivity value were differentrate reduce, the greater the degree of eccentric is, the faster of reduce is. Mud intrusionasymmetry, array8performances better than others. |
