The Study Of The Borehole Environment Effects On The Response Characteirstics Of The Tiraxial Array Induction Logging Tool In Thevertical Well

Resistivity is a key parameter to analyze the lithology, estimate the hydrocarbonsaturation，and evaluate the oil and gas reservoir. The tiraxial array induction tool is a newtype of induction logging tool It not only can measure both the hoirzontal resistivity andvertical resistivity, but also obtain the dip and azimuth information. It is a significant methodto identify the shale, thin interactional low resistivity reservoir and suitable for the vertical,deviated and horizontal wells. It has a broad application in oil field with low porosity, lowpermeability, and low resisitvity. Tool design, measuirng theory and data processing of thetiraxial array induction are very complicated. There are many problems to be solved. The basictheory and the borehole environment effects on the response characteirstics of the triaxialarray induction logging tool in the vertical wells are studied in detail by the COM SOLfinite-element sotfware. The results provide the theoretical guidance for the development ofthe tiraxial induction array tool. It has a theoretical and practical importance. The contents ofthe research are divided into five aspects.Firstly, the configurations and measuring pirnciples of both array induction logging MITand tiraxial arary induction logging are introduced. The numeircal computation technology ofthe triaxial array induction logging response in the vertical wells based on the COMSOLfinite-element sotfware is studied. Then solved problems include the gird division, the addingsource to model, the method of calculating the receiver signal, the setting of the solver and soon.The second part researches the influence of the fiber glass radius and two ends metal onthe hoirzontal received signal of the triaxial array induction. The effect of the fiber glass radiusand the filler in ifber, two ends metal length and distance on measurements are computed andanalyzed. The results show that the fiber glass reduces the eddy current between transmittercoil and receiver coil, and at same time the received signal of horizontal coil is big. Theinfluence of metal length on each sub array can be neglected, and the influence of two endsmetal on received signal is related to surrounding formation conductivity and the absoluteerror is approximately proportional to the conductivity. When the distance between the metal and its nearest coil is greater than0,3m, the influence of metal on each sub array measuringsignal can be neglected.The third part is the research of the hoirzontal coil induction logging boreholeenvironment effects. Firstly, we study borehole effects in a water tank by3D numeircalsimulation. The response characteirstics of eight hoirzontal sub-arrays are computed andanalyzed when the borehole parameters are changed such as well diameter, tool position, mudand formation conductivity, and then compared with the normal borehole model response. Theresults show that the sub-array1,2,3,4are more seirously inlfuenced by well radius, mud andformation conductivity. These phenomena consist with the normal borehole model. Boreholeeffects of sub-array5，6,7decrease gardually. There are certain difference with ideal model.The longest sub-array has a great difference with the response of the normal borehole model.When the tool is eccentric, due to the eccentirc effect and the skin effect，the boreholeresponse becomes abnormal. The inlfuence in the water tank is greater than the normalborehole model. Secondly, the influence of invasion and shoulder to the measured signal arecomputed and analyzed Changing invasion radius, layer thickness and shoulder influence. Theresults show that the effect of the invasion radius on each subarray is different. The effect has aobvious increase when the shoulder conductivity is greater than0,5S/m. The Layer thicknessalso has some influences on each subarray.In part four, the distirbution characteirstics of the electromagnetic field are investigatedby drawing lines of electirc current and magnetic ifeld in vertical wells. Calculate theresponses of some models in part two and part three. Consider factors including two endsmetal, layer resistivity and thickness, invasion and shoulder. The analyzing results show theeddy current generated by phenomena of relfection and transmission on the interface ofdifferent conductivities according to the conductivity. At same time, the magnetic ifeld lineschange with the change of the current lines. When the source is in different position, themagnetic field distirbution is different. The magnetic field distirbution in water tank is morecomplicated, the mud conductivity has a little effect on itIn the last part，we research the response of array induction logging when tool is deviated.Change the tool position in target formation. The dip angle is changed from0to90degree.The results show that the measured signals change with the position, dip and conductivity ofdifferent areas. The change characteirstic is a more complicated.