物探与化探
物探與化探
물탐여화탐
GEOPHYSICAL AND GEOCHEMICAL EXPLORATION
2015年
1期
186-191
,共6页
激发极化%弛豫时间谱%正则化反演%泥质砂岩%信噪比%奇异值分解
激髮極化%弛豫時間譜%正則化反縯%泥質砂巖%信譟比%奇異值分解
격발겁화%이예시간보%정칙화반연%니질사암%신조비%기이치분해
induced polarization%relaxation time spectrum%regularization method inversion%argillaceous sand%signal-to-noise ratio%singular value decomposition
激发极化衰减谱是一系列单指数衰减的线性叠加，因此可以对衰减谱进行多指数反演，得到的弛豫时间谱可用于储层孔隙结构和渗透性评价，是一种非常有前途的技术。由于实际测井的信噪比相对较低，常规的奇异值分解方法难以获得合理的弛豫时间谱，为此，采用正则化约束，结合奇异值分解，对合成数据和实际测量的衰减谱进行反演，得到连续的弛豫时间谱；同时，讨论了弛豫时间谱的时间常数分布、正则化因子以及信噪比对反演结果的影响。研究结果表明：该方法适用于信噪比较低的实际测量结果的反演，弛豫时间常数的分布点数为32～64较为合适；随着正则化因子的增加，反演结果逐渐变得平滑，存在一个最优的正则化因子，用于获得最为合理的弛豫时间谱；在双对数图中，最优正则化因子随着信噪比的增加而线性降低，因此通过测量结果的信噪比，可以求取最优正则化因子，进而将该技术应用于实际。
激髮極化衰減譜是一繫列單指數衰減的線性疊加，因此可以對衰減譜進行多指數反縯，得到的弛豫時間譜可用于儲層孔隙結構和滲透性評價，是一種非常有前途的技術。由于實際測井的信譟比相對較低，常規的奇異值分解方法難以穫得閤理的弛豫時間譜，為此，採用正則化約束，結閤奇異值分解，對閤成數據和實際測量的衰減譜進行反縯，得到連續的弛豫時間譜；同時，討論瞭弛豫時間譜的時間常數分佈、正則化因子以及信譟比對反縯結果的影響。研究結果錶明：該方法適用于信譟比較低的實際測量結果的反縯，弛豫時間常數的分佈點數為32～64較為閤適；隨著正則化因子的增加，反縯結果逐漸變得平滑，存在一箇最優的正則化因子，用于穫得最為閤理的弛豫時間譜；在雙對數圖中，最優正則化因子隨著信譟比的增加而線性降低，因此通過測量結果的信譟比，可以求取最優正則化因子，進而將該技術應用于實際。
격발겁화쇠감보시일계렬단지수쇠감적선성첩가，인차가이대쇠감보진행다지수반연，득도적이예시간보가용우저층공극결구화삼투성평개，시일충비상유전도적기술。유우실제측정적신조비상대교저，상규적기이치분해방법난이획득합리적이예시간보，위차，채용정칙화약속，결합기이치분해，대합성수거화실제측량적쇠감보진행반연，득도련속적이예시간보；동시，토론료이예시간보적시간상수분포、정칙화인자이급신조비대반연결과적영향。연구결과표명：해방법괄용우신조비교저적실제측량결과적반연，이예시간상수적분포점수위32～64교위합괄；수착정칙화인자적증가，반연결과축점변득평활，존재일개최우적정칙화인자，용우획득최위합리적이예시간보；재쌍대수도중，최우정칙화인자수착신조비적증가이선성강저，인차통과측량결과적신조비，가이구취최우정칙화인자，진이장해기술응용우실제。
The time?domain induced polarization (IP) decay curve is a linear superposition of IP signal from individual pores. It can be transformed to relaxation time spectrum related to the pore structure and can be used to estimate the permeability of the argillaceous sand. So the IP logging is a useful tool for reservoir characterizing. The singular value decomposition (SVD) method can be used to ex?tract the relaxation time spectra from the decay data with high signal?to?noise ratio ( SNR) . This method is unstable and invalid for the practical downhole use because of the noisy decay data. In this study, a method of regularization was applied to extracting continuous IP relaxation time spectra from simulated and real decay data. Influence of the regularization factor, SNR and relaxation time arrangement on the spectra was also discussed. Firstly, for the simulated decay data with noise, the spectra become smoother with increasing regu?larization factor. There is an optimal value which can be used to get the most reasonable spectrum. The optimal factor decreases linearly with increasing SNR on a log?log scale. This relationship can be used to predict the optimal factor from a known SNR. Secondly, the in?fluence of relaxation time arrangement on the spectra shows that the suitable relaxation distribution point ranges from 32 to 64. Finally, the developed algorithm and the prediction of the optimal factor are very suitable for the inversion of the spectra of the real data.
