摘要
分析了金属套管井中有限尺寸线圈的电磁响应特征,讨论了井眼泥浆参数?套管参数和不同线圈尺寸对电磁测井响应的影响,考察了金属套管中电磁测井对地层电阻率变化的灵敏度.径向非均匀介质的模拟计算表明,在套管井中井眼泥浆对电磁测井的影响较大,必须进行校正.在低频条件下,井间测量响应中金属套管与地层的电磁响应是非耦合的,两者可以分离.在套管参数一定时,套管响应与地层的响应的比值近似一个常数.电磁响应对地层电阻变化的灵敏度分析显示,井间电磁测量在储层研究尺度对地层电阻率变化响应灵敏,套管引起的衰减稳定.在其它参数相同的前提下,线圈直径的增大有助于有效电磁响应信号的增强,给大井间距测量提供了可能.不同磁导率金属套管的电磁响应分析表明,电磁测井中,采用非磁性或弱磁性套管要优于一般的铁磁性套管.
The electromagnetic responses of the finite size induction coils were evaluated, and the effects of the borehole mud ,casing pipe and radius of the induction coils were analyzed, the sensitivity of the electromagnetic response to the formation resistivity was checked against the crosshole measurements. It is shown by the numerical results of the radial inhomogeneous model that, the borehole mud has little effects on the electromagnetic responses when compared with that of the casing pipe, hence we can ignore of the mud effect in casing hole environment in crosshole electromagnetic measurements. At low frequency band, the contributions of the casing pipe and the formation to the electromagnetic responses are uncoupling in crosshole electromagnetic configuration, we can separate the formation response from the comprehensive field. In case of the specified parameters of the casing pipe, the ratio of the casing response to that of the formation is almost a constant. Furthermore, the sensitivity analysis of the electromagnetic responses to the formation resistivity indicates that, in crosshole environment, the electromagnetic responses are fairly sensitive to the formation resistivity and the casing pipe attenuation is very stable. By increasing of the transmitter coils＇radius, we can enhance the intensity of the electromagnetic response , and make it feasible of the large stride crosshole measurement. The numerical results of different magnetic permeability of the casing pipe show that in crosshole environments, non-magnetic or low-magnetic steel pipe is superior to magnetic iron pipe.
出处
《地球物理学进展》
CSCD
北大核心
2007年第6期1781-1790,共10页
Progress in Geophysics
基金
中石油物探应用基础研究(04A10102)资助
关键词
金属套管井
有限尺寸线圈
电磁测井响应
cased borehole, finite size coil, electromagnetic logging responses
