随钻方位电磁波测井可提供邻近地层界面的准确位置信息而被广泛运用于实时地质导向钻井,但如何选取合适的反演模型和最优化算法则是决定随钻方位电磁波测井资料反演速度和精度的关键。为此,首先基于降维策略将复杂地层随钻方位电磁波测井资料3D反演问题简化为一系列1D问题,然后探讨不同1D反演模型、反演算法的可行性与反演效果,并给出了两者组合的最优选取方法。数值模拟结果表明,1D反演模型的选取取决于靶层的厚度,而反演算法的选取则依赖于反演模型的层数,即对靶层厚度为4.0 m以上的厚层,应选用单界面反演模型和梯度反演算法组合;当靶层厚度为1.0~4.0 m时,仅需将单界面反演模型替换为双界面反演模型即可提供准确的邻近上、下地层界面;对薄层随钻方位电磁波资料,则需采用多界面反演模型和Bayesian反演算法。图8表1参14
王磊
,
范宜仁
,
袁超
,
巫振观
,
邓少贵
,
赵伟娜
. 随钻方位电磁波测井反演模型选取及适用性[J]. 石油勘探与开发, 2018
, 45(5)
: 914
-922
.
DOI: 10.11698/PED.2018.05.18
Azimuthal electromagnetic logging while drilling (LWD), which is capable of providing accurate position information approaching bed boundary, has been widely applied in real-time geosteering. For the inversion speed and precision of azimuthal electromagnetic LWD data, the key lies in the selection of proper inversion model and corresponding optimization algorithm. In this study, we first simplified the complex three-dimensional (3D) inversion of data into a series of one-dimensional (1D) inversion problems by using the dimensionality reduction scheme. Then, the feasibility and inversion performance of various 1D inversion models and different optimization methods were investigated, and the best combination between the inversion model and inversion algorithm was also obtained. Numerical simulation results show that the selection of 1D inversion model is dominated by the thickness of targeted beds, whereas the determination of inversion algorithm relies on the total layers amount of the inversion model. For the formation with thickness larger than 4.0 m, the single boundary inversion model and gradient optimization method are recommended. When the bed thickness is between 1.0 m and 4.0 m, the two-boundary inversion model instead of the single-boundary one is needed to estimate upper and lower boundaries around the borehole. For the inversion of azimuthal electromagnetic LWD data of thin layers, the multiple- boundary inversion model and the Bayesian algorithm should be employed.
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