Study On Geo-steering Method Of Directional Electromagnetic Wave Resistivity Logging-while-drilling Tools

The number of horizontal and highly deviated wells are increasing day by day oweing to frequent offshore drilling activities, potential tapping of old blocks and exploration of complex reservoir, which promotes the formation of intense requirement for logging-while-drilling and reservoir geo-steering techniques. The directional electromagnetic wave resistivity logging-while- drilling tool not only is latest technology emerged in the last decade but also possesses azimuth sensitivity which conventional tools are short of. The azimuth sensitivity greatly enhances geo-steering ability of the new tools. Now the large oil-field service companies have launched their commercial directional electromagnetic wave resistivity logging-while- drilling tools, and meanwhile domestic tool is still in research and development stage. Therefore studies on geo-steering method of this new tool is of important significance.In this paper, the response pattern of geo-signals measured by this new tool is researched using magnetic-current-source dyadic Green′s functions in horizontally stratified anisotropic media, and the tool configuration refers to Periscope 15 which belongs to Schlumberger. The relative location between tool and formation boundary can be determined by combining the orientation vector and the change of directional geo-signal, the orientation vector is obtained from the voltage of receiver coil and directs to the conductive shoulder bed. The formation azimuth can be fixed through the gray distribution of azimuthal image made by symmetrical directional data, which is not influenced by formation anisotropy. A crossplot can be manufactured by symmetrical directional attenuation and phase shift, then the tool-to-boundary distance can be evaluated by interpolating the crossplot with real-time date.The symmetrical directional geo-signals will lost sensitivity to formation boundary and be proportional to deviation angle when the transmitter coil and receiver coil are separated by boundary, which provides a method to acquire deviation angle in real time. Another crossplotcan be manufactured by anti-symmetric directional attenuation and phase shift, then the anisotropy coefficient can be estimated by interpolating the crossplot with real-time date,because anti-symmetric directional geo-signals are sensitive to anisotropy and deviation angle.This paper supplies valuable reference to the geo-steering method of directional electromagnetic wave resistivity logging-while-drilling tools.