Fast Inversion And Application Of Logging-While-Drilling Resistivity Measurements In High-Angle And Horizontal Wells

Logging-While-Drilling(LWD)is widely used in real-time geological guidance and reservoir evaluation while drilling in high-angle wells/horizontal wells,but its detection ability is limited.It is the trend and inevitable requirement of LWD to further expand the detection ability of electromagnetic logging tools and make up for the gap between logging scale and geophysical resolution.Accurate measurement of reservoir anisotropic resistivity and real-time acquisition of formation interface are very important for geological guidance while drilling and fine reservoir evaluation.Traditional LWD logging is sensitive to anisotropy because of its high resolution and high angle.It has been widely used in reservoirs with relatively clear geological structure.However,there are still some problems as follows:(1)shallow detection depth,there was no azimuth detection ability;(2)serious separation of apparent resistivity curves at different detection depths due to the influence of formation adjacent formation interface,relative dip angle and anisotropy;(3)serious separation of apparent resistivity curves at different detection depths.The apparent resistivity value of anomalous resistivity is much larger than the true value of formation.Therefore,accurate inversion of real resistivity information is one of the key problems to be solved in real-time geological guidance and reservoir evaluation.First of this paper briefly introduces the principle of traditional electromagnetic logging-while-drilling,and the numerical simulation response characteristics of traditional electromagnetic logging-while-drilling tool in the downhole environment of high inclined wells/horizontal wells,and further analyses its influencing factors,which provides technical support and theoretical guidance for the widely used geological guidance technology in fixed wells and the fine evaluation of reservoirs after drilling.And then,the processing method of electromagnetic logging-while-drilling in infinite thickness formation is discussed in detail.The Gauss-Newton method and regularization parameter selection method are introduced in detail.The iteration format of Gauss-Newton algorithm and the automatic iteration update method of regularization parameters are deduced systematically.The complex practical problems and irreducible problems in the inversion process of electromagnetic logging while drilling in highly inclined wells/horizontal wells are pointed out.A series of simplified inversion strategies and constrained optimization strategies are proposed based on beam optimization inversion theory.Based on the previous chapters,at last we established a set of fast inversion techniques for electromagnetic logging while drilling in high-angle wells and horizontal wells,and verifies the stability and applicability of the inversion algorithm through a series of numerical simulations.Finally,the electromagnetic logging while drilling data of two horizontal wells are processed,and good inversion results are obtained,which shows the practicability of the inversion technology.