Simultaneous inversion of four physical parameters of hydrate reservoir for high accuracy porosity estimation

IF 1.8 3区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS
Yuning Yan, Hongbing Li
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引用次数: 0

Abstract

Estimation of the porosity of a hydrate reservoir is essential for its exploration and development. However, the estimation accuracy was usually less certain in most previous studies that simply assumed that there is a linear relationship between the porosity and single-elastic wave velocities or other rock physical parameters, thus affecting the evaluation of the reserves. In the three-phase Biot-type equations that are fundamental to model a hydrate-bearing reservoir, porosity, alongside hydrate saturation, mineral constituent proportions and hydrate–grain contact factor, is non-linearly responded by density, compressional and shear wave velocities. To improve porosity estimation, we propose to invert simultaneously four-parameter (porosity, hydrate saturation, mineral constituent proportions and hydrate–grain contact factor) using an iteratively nonlinear interior-point optimization algorithm to solve a nonlinear objective function that is a summation of the squared misfits between the well log and three-phase Biot-type equation–modelled density, compressional and shear wave velocities. A test in Mount Elbert gas hydrate research well was conducted for the case of a gas hydrate stratigraphic test well where elastic wave velocities, density, porosity and mineral composition analysis data are available. The four-parameter inversion yielded a lower root mean square error for porosity (0.0245) across the entire well-logging section compared to previous estimations from the linear relationship, post-stacked and pre-stacked seismic traces as well as the pore-filling effective medium theory model applied to other well cases. Additionally, the other three parameters demonstrated good agreement with well logs. Inversion tests conducted at three additional hydrate sites also produced accurate results. Consequently, the new method surpasses previous approaches in porosity estimation accuracy.

同时反演水合物储层的四个物理参数,实现高精度孔隙度估算
水合物储层孔隙度的估算对其勘探和开发至关重要。然而,以往的大多数研究都简单地假设孔隙度与单弹性波速或其他岩石物理参数之间存在线性关系,因此估算精度通常不太确定,从而影响储量评估。在作为含水储层基本模型的三相 Biot 型方程中,孔隙度与水合物饱和度、矿物成分比例和水合物-晶粒接触因子一起,与密度、压缩波速和剪切波速呈非线性反应。为改进孔隙度估算,我们建议使用迭代非线性内点优化算法同时反演四个参数(孔隙度、水合物饱和度、矿物成分比例和水合物-晶粒接触因子),以求解非线性目标函数,该函数是测井曲线与三相毕奥特方程模拟的密度、压缩和剪切波速度之间的误差平方和。在埃尔伯特山天然气水合物研究井中进行了一项测试,测试对象是一口天然气水合物地层测试井,该井有弹性波速、密度、孔隙度和矿物成分分析数据。与以前通过线性关系、叠后和叠前地震道以及应用于其他井况的孔隙充填有效介质理论模型进行的估算相比,四参数反演在整个测井剖面上得出的孔隙度均方根误差(0.0245)更小。此外,其他三个参数与测井记录也有很好的一致性。在另外三个水合物地点进行的反演测试也得出了准确的结果。因此,新方法在孔隙度估算精度方面超过了以前的方法。
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来源期刊
Geophysical Prospecting
Geophysical Prospecting 地学-地球化学与地球物理
CiteScore
4.90
自引率
11.50%
发文量
118
审稿时长
4.5 months
期刊介绍: Geophysical Prospecting publishes the best in primary research on the science of geophysics as it applies to the exploration, evaluation and extraction of earth resources. Drawing heavily on contributions from researchers in the oil and mineral exploration industries, the journal has a very practical slant. Although the journal provides a valuable forum for communication among workers in these fields, it is also ideally suited to researchers in academic geophysics.
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