Nuclear Magnetic Resonance Logging-While-Drilling Response at Formation Boundary
详细信息
- 责任者：Li Xin (State Key Laboratory of Petroleum Resource and Prospecting ; China University of Petroleum ; Beijing 102249 ; China) ; Xiao Lizhi
- 刊名：Chinese Journal of Geophysics
- 出版年：2013
- 卷期：56(8)
- 关键词：核磁测井 ; nuclear magnetic logging ; 随钻测井 ; well logging while drilling
- 页码：p.2862-2869
- 图表：9 illus., 20 refs.
- 分类号：1600
- issnNo：ISSN0001-5733
- isbnNo：CN11-2074/P
摘要
It is of significance to identify properties and boundaries of formation for NMR geosteering and in-situ reservoir evaluation.In this paper,a discretization method and NMR LWD response function are proposed based on drilling trajectory and sensitive-volume-unit contribution concept.Forward numerical modeling and inversion are employed to simulate NMR LWD logging response in different formation cases and factors,such as well deviation angles,formation boundary types,antenna apertures and target formation thicknesses.Quantitative relationships of these factors in certain condition are given here.Significant differences of T2 distributions and porosities can be found in comparison of NMR logging response between vertical wells and deviated wells.It shows that the bigger the deviated angle,the longer the apparent formation thickness and the longer the transitional interval in NMR response of formation boundary.Therefore,the depth of formation boundary cannot be extracted from initial point of transitional part of T2 distribution anymore.Vertical resolution is related to the length of antenna,borehole and tool’s parameters.Besides that,an abnormal ’sandwich’ may be reflected in thin target formation of logging response because of the existence of surroundings effects.These results provide suggestion to NMR LWD applications to improve real time formation identification.
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