| In the oil and natural gas exploration and development of underground resources, the nature of the resistivity of the reservoir are the base for evaluation whether the formation are oil-bearing strata, including gas, oil or water-bearing layer, and it is the important parameters of evaluating oil and gas saturation. In horizontal and deviated wells, curve of logging has changed because borehole dot not cross through vertically the formation. The successful application of the traditional relationship and the response of various calibration plate do not be applied, the staff did not know to explain logging curve and can not extract information related to stratigraphy, formation evaluation conclusions is difficult to get right. Actual production need is urgent to the response characteristics of induction logging and electromagnetic wave logging in horizontal wells. This article has been made because evaluation of horizontal wells is needed in oil and gas exploration and development. It can help explained staff of well logging to correctly understand curve shape and calibration plate, enhance formation evaluation of horizontal well in line with the rate of horizontal wells at the same time can reduce the overall oil and gas exploration and development costs and risks, improve economic efficiency, the practical value of this article is self-evident.The problem of induction logging and electromagnetic wave logging in horizontal wells, because azimuthal symmetry of the geometric model is broken and medium is non-uniform, the analytical method can not solve it, three methods is use of finite difference, finite element method, integral equations and numerical mode-matching, etc. Because it is three-dimensional problem in horizontal wells, and the electric and magnetic fields are vectors, vector finite element method for tetrahedral elements is used. Compared to the finite difference and numerical mode-matching, the most significant advantages of the finite element method are able to adapt to the complex geometry. In previous work, whether analytic or numerical algorithm algorithms have to simplify the physical model greatly, the actual process of logging equipment often eccentric, eccentric or eccentric invasive, whereas the finite element method is particularly adapted to the geometric situation of induction logging and electromagnetic wave logging at the horizontal wells.Finite element method is a sophisticated method to calculate the electromagnetic field in the complex medium. There are many successful works to calculate tool response of induction and electromagnetic wave logging in two-dimensional axisymmetric formation. Because of the complexity of the formation, the three-dimensional finite element method must be to adopt. According to the characteristics of formation structure in horizontal wells, measurement methods and equipment structure of induction and electromagnetic wave logging tool, the mathematical and physical model simulating measurements response dual-induction and electromagnetic well logging are built in the horizontal wells. Vector element of tetrahedral used to overcome the shortcomings of node-based finite elements, such as the pseudo-solution problem, SSOR-BICG used for solving equations procedures also improve speed and stability.The basic principles of induction logging can be using the role of double coil to illustrate: transmitter was passed alternating current, the receiver receive the induction electromotive force in the process of logging, which are effected by the formation. Coil placed in inhomogeneous media and the conductivity isσ, when the frequency of transmitter CT isωand the current is I, the transmitter produce an alternating electromagnetic field in the surrounding medium, known as first field, it excitated alternating current namely eddy current in conductivity medium. Eddy current line is concentric circles as the central axis of coil. Eddy current give rise to alternating electromagnetic field, called the secondary field, it produce induced electromotive force in the receiving coil, measurements of induction log is the induced electromotive force generated by the secondary field in the receiving coil. Dual-induction logging instruments are composed of three transmitter coils and eight receiving coils, it measure two curves that are deep-induction resistivity and medium-induction resistivity, which share three transmitter coils. Three receiving coils of deep induction and five receiving coils of medium induction are connected in series, Transmitter excitated AC current 20kHz, Alternating current generated in the formation alternating electromagnetic field which generated induced current in the conductive medium. The induced current in formation produce induced electromotive force in the receiving coil, the size of induced electromotive force is rate of conductivity in the formation medium. Adjust the coil spacing, number of turns and series direction, to offset the direct coupling signal to obtain purpose of the desired characteristics of the measurement. Electronic devices receive induced electromotive force measurement on coil and calibrate apparent resistivity. Analysis of the geometric factor showed that induction logging measurements have distinct characteristics, measured value of tool anywhere is co-contribution of upper and down formation. Contribution measured of deep and medium induction at the measuring point is 50 percent from up and down one meter thickness formation, Ninety five percent of the contribution for medium induction and deep induction at the measuring point are form 5-meter thickness formation and 10 meter thick formation respectively. When frequency of excitation current is 20 KHz, measuring instrument has good detection depth, depth of deep induction is 1.5-1.8 meters and medium induction is 0.5-0.7 meters for measuring electrical conductivity, at the same time the contribution of formation have the linear superposition. the detection characteristics of equipment decide that the interface layer was not clear for apparent resistivity at the thin layer, the response of amplitude is low at thin reservoir. When dip angle is zero, two-dimensional axisymmetric results are compared to verify the correctness of the method. The apparent resistivity is evaluated as the tool ascends the borehole. Seven different dip (150, 300, 450, 500, 550, 600 and 750) angles are considered. The results showed that with the increase in the angle of apparent resistivity the curves changes widely, the apparent resistivity is abrupt change in dipping bed boundaries. When it is the same dip angle, the apparent resistivity of deep induction is less than medium induction. When there is with the impact of invasive (low invasive), apparent resistivity of deep induction and medium induction have been decreased by the influence of the invasion, and abruption has been vanished. In models of horizontal well, first of all equipment passing through the two bed layers model is calculated, because apparent resistivity of medium induction is close to resistivity of formation equipment surround, when the apparatus pass through the interface layer, two curves of deep and medium induction apparent resistivity are cross, and the intersection is at high resistance layer. After multi-layer interface, the interface reaction layer can be in sight, but the interface was not clear, the response rate is low in thin layers. At the three-layer model, the apparatus separately from the layer boundaries, with a radius of invasion, thickness, etc. were studied, and finally produced invasive plate calibration. In distance from the layer boundary example, when the resistance in middle bed layer was lower than the surrounding rock's, the apparent resistivity of deep and medium induction are almost not affected greatly in middle bed layer. With the increasing of resistivity middle layer, it is impacted significantly by wall rock. Although the physical model is axisal non-symmetry, but the formation model is symmetry so that two curves of apparent resistivity is also about the symmetry about the boundary layer. In the horizontal wells low invaded has been considered mainly, with the increase in radius of the invaded zone, apparent resistivity decrease rapidly, when the radius arrive at a value, the apparent resistivity is same as resistivity of invasion zone. From the impact of the thickness it is shown that apparent resistivity reduces gradually with thickness of layer increasing. In contrast, when resistivity of middle layer is greater than wall rock, along with the increasing of thickness, apparent resistivity gradually increase near the resistivity of middle layer. Through the study of distance from the border and thickness, the resistivity measured in horizontal well can be corrected; the real information of formation can get it.Method of electromagnetic wave logging is different form the induction logging, electromagnetic wave logging measure mainly the phase shift and attenuation when spread in the media, in the non-magnetic medium, when the frequency is million hertz, the phase difference and amplitude attenuation depends primarily on the size of medium resistivity. The use of phase difference and attenuation measured can calculate apparent resistivity. Transmitter of Electromagnetic wave logging tool is passed alternating current, the phase difference and amplitude attenuation received by the two receivers are concerned with the resistivity nearby borehole. In uniform layer the phase difference and amplitude ratio of the corresponding relationship to the conductivity calibration, can be converted to apparent resistivity the corresponding formation. Transmitter excitated electromagnetic wave that spread in the formation, changes of the phase difference and amplitude ratio can determine characteristics of formation. This article elaborated on the principle of electromagnetic logging measurements, and derived the scale method. Analysis of phase difference, amplitude attenuation and apparent resistivity of the calibration chart we can see that resistivity of decay corresponding to formation is smaller dynamic range, and phase changes is more sensitive to formation resistivity, so this paper make use of phase difference to calculate apparent resistivity. To validate the computational efficiency and accuracy, the model was tested in a uniform medium with a resistivity and the dip angle of beds is 150. The relative error is less than 2%. The apparent resistivity is calculated as the tool ascends the borehole. Seven different dip (150, 300, 450, 500, 550, 600 and 750) angles are considered. The results showed that with the increase of the angle, apparent resistivity are impacted by the boundary of formation, when the frequency is 2MHz and angle is 750, the apparent resisitivity in boundaries is even larger than resisitivity of the middle bed. It's shown that the invasion reduces the apparent resistivity in the center bed. Abrupt changes of apparent resistivity in dipping bed boundaries are reduced. In another situation, the response of electromagnetic wave tool crossing five layers formation, in the shoulder beds, the apparent resistivities are almost equal to the true resistivities. The apparent resistivities of middle three beds are less than the true resistivities. Although there are five layers in this example, the present method gives a reasonable result. Through analysis horizontal well model we can see through model, the frequency of electromagnetic wave logging is higher than induction logging and it have high-resolution, especially 2MHz electromagnetic is sensitive to layer interface, but also, it is that this characteristic can be used by LWD and Geosteering. Through the study of distance from the border and thickness, the resistivity measured in horizontal well can be corrected; the real information of formation can help to correct calibration plate.A lot of works in this dissertation need improve constantly. The physical model should be much closer to actual physical model of logging, for example the size of drill collar and the groove of the situation in logging while drilling should be considered. Furthermore the stability and speed of the finite element method also need improve further.
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