摘要
Acoustic and electrical methods are commonly used to evaluate hydrate saturation based on P-wave velocity(Vp)and resistivity,respectively.We evaluate hydrate saturation using petrophysical parameters directly related to the presence of hydrates.Five petrophysical parameters sensitive to hydrate saturation were first analyzed using the equivalent medium rock physical model,logging intersection plots,and petrophysical parameter inversion.The simulated annealing global optimization method was then used to estimate the hydrate saturation profile in the Shenhu Area,China.The petrophysical parameters Vp,λρ,andλμ,which are associated with the rock elastic and shear moduli,are highly sensitive to hydrate saturation for an estimated saturation range of 0.1-0.44.This range is consistent with that obtained from the original well diameter curves.However,the parameters Vs andμρ,which are only related to the rock shear modulus,yield high hydrate saturation estimates of 0.22-0.43 and exhibit some deviations from the real-time data.Owing to its sensitivity,the Poisson’s ratio is least desired for hydrate evaluation among the studied parameters.The sensitivity of hydrate saturation depends on the petrophysical model used for studying hydrate physical properties and storage analysis.
用声学、电学方法评价水合物饱和度是分别基于纵波速度和电阻率的。与天然气水合物储集层直接相关的岩石物理参数被用于评估水合物饱和度,首先基于等效介质岩石物理模型、测井交会图以及岩石物理参数反演结果,分析了5个岩石物理参数对水合物饱和度的敏感程度。然后采用模拟退火全局优化方法估算神狐海域水合物饱和度剖面。与岩石弹性模量(体积模量和剪切模量)有关的岩石物理参数Vp,λρ和λμ对水合物饱和度敏感度较高,水合物饱和度估算范围为0.1-0.44。该结果与基于原始测井曲线的饱和度范围基本一致。然而,仅与岩石的剪切模量有关的参数Vs和μρ估算出了相对较高的水合物饱和度值:0.22-0.43,其与实际数据存在较大偏差。在各岩石物理参数中,泊松比(σ)对水合物饱和度评价结果最不理想,水合物饱和度的敏感性取决于岩石物理模型以及水合物的储集形式。
基金
The study is supported by the National Natural Science Foundation of China(Nos.91958206,41876053)
the National Key Research and Development Plan(2017YFC0307401,2018YFC1405901)
the Fund of Acoustics Science and Technology Laboratory(GK2050260214,GK2050260217,GK2050260218,KY10500180084,KY10500190031,6142108200202)
Fundamental Research Funds for the Central Universities(HEUCFJ180503,201964016).
