A Study On Extraction Method Of Formation Conductivity In Deviated Borehole

Taking the formation of layered anisotropic electromagnetic dyadic Greenfunction as a starting point, and then using the theory of the transmission line andrelated research, we has established the formula of one-dimensional layeredanisotropic media magnetic current source dyadic Green function of the analyticmethod in this paper. Introducing instrument constant, and making use of equipmentand stratigraphic coordinate system conversed relationship of magnetic field strengthand its apparent conductivity, then we can calculate the formation conductivity andborehole angle in the tilt wellbore. Finally, we use the forward method and inversionformula to do some numerical simulation, then we discuss the variation of forwardmodeling and inversion results with different parameters such as the formationconductivity、dips and so on.First of all, using the Fourier conversion technology and operator decompose theMaxwell equation, we can decompose the electromagnetic field in frequency field,then we can get two separate waves of horizontal and transverse magnetic, as well asits corresponding transmission line equation. On the basis of this, TE wave and TMwave solutions are obtained through the definition of transmission line the Greenfunction. Also frequency domain electromagnetic dyadic Green function is obtained.Secondly, we can get magnetic current source field dyadic Green function and itsintegral expression, and then we can get the various components of the magnetic fieldand its imaginary part among inclined wells. Then making use of equipment andstratigraphic coordinate system conversed relationship of magnetic field strength, andat the same time, we can also obtain the expression between them. We can obtain theresult of the formation conductivity and borehole angle with the imaginary part ofmagnetic field. We also introduced the instrument parameters, then we can obtain the expression of apparent conductivity in borehole coordinates and we can use apparentconductivity to derive the result of formation information, and then make analysis ofthese two methods.Then we will use the forward method and approximate inversion formula of theformation conductivity and borehole angle in the tilt borehole, then we conduct thespecific numerical simulations, mainly on forward response characteristics of thethree-dimensional sense in the different circumstances and the error between theformation parameters and the true value obtained by the approximate formula and itsvariation.Finally, from the numerical results we can see when the formation conduction islarge, the values of apparent conductivity have a large difference in different spacing.The effect of the instrument from dip is large too, the variation of inclination isclosely related with the coefficient of anisotropy, when the coefficient of anisotropyincreased, the impact of inclination is significantly increased. We also can see whenthe formation conductivity is larger, then the inversion degenerated. The error of thedip·s inversion is always large, especially the range of angle is in3060degree, thequality of inclination is decreased obviously, but when the spacing is larger, it isconvenient to improve the quality of inclination inversion.