水平井及斜度井声波测井响应正演模拟研究（英文）

发布时间：2018-08-24 09:25

【摘要】：常规声波测井解释方法建立在各向同性地层中的垂直井基础之上,对各向异性地层中的水平井和斜度井并不适用。在水平井和斜度井的钻井过程中,岩屑会溅到井壁并最终在井壁底部形成一层薄岩屑层。同时,高速层和各向异性也可能会影响声波时差的测量。本文采用结合了Hybrid-PML的交错网格时域有限差分方法(SGS-FDTD),研究阵列声波仪器在各向异性介质中的水平井和斜度井条件下,不同因素对测得时差所带来的影响。模拟结果揭示了声波时差在高速层,薄岩屑层,井斜角,层厚,各向异性等不同影响因素下的相应规律。我们发现当波长远小于井壁与高速层的距离时,能够准确测得目的层时差;然而在两者处于同一量级时的近场条件下,几何声学理论不再适用;当井眼底部存在岩屑层时,费马原理依旧适用,对真实时差测量没有影响;在各向异性地层环境下,井斜角的增大使得测得时差由垂直向时差逐渐趋近于水平向时差;对于特定源距的声系,仪器在目的层中所移动的距离超过一定距离时,方可获得薄层时差值。基于不同井斜角和不同各向异性大小均匀TI地层模型的模拟结果,绘制了时差估计图版,可以对任意井斜角和各向异性比的模型进行时差的定量估计。通过对不同声系和不同弹性参数的模拟实验,证明了这种时差估计方法对TI地层中的水平井和斜度井准确有效。
[Abstract]:The conventional acoustic logging interpretation method is based on vertical wells in isotropic formations and is not suitable for horizontal wells and deviated wells in anisotropic formations. During the drilling process of horizontal and inclined wells, the cuttings will splash into the well wall and eventually form a thin layer of cuttings at the bottom of the wellbore. At the same time, the high-speed layer and anisotropy may also affect the measurement of acoustic moveout. In this paper, the staggered grid finite-difference time-domain (SGS-FDTD) method combined with Hybrid-PML is used to study the effects of different factors on the measured time difference under the conditions of horizontal wells and inclined wells in anisotropic media. The simulation results reveal the corresponding rules of acoustic moveout under different influence factors such as high speed layer thin cuttings well angle layer thickness anisotropy and so on. We find that when the wavelength is much smaller than the distance between the borehole wall and the high speed layer, the time difference of the target layer can be accurately measured. However, under the condition of the same order of magnitude, the geometric acoustics theory is no longer applicable, and when there is a cuttings layer at the bottom of the borehole, The Fermat principle is still applicable and has no effect on the real time difference measurement. In anisotropic formation, the increase of well inclination angle makes the measured time difference approach to horizontal time difference from vertical to vertical. For the acoustic system of specific source distance, The thin-layer time difference can be obtained when the distance of the instrument in the target layer exceeds a certain distance. Based on the simulation results of uniform TI formation model with different well inclination and anisotropic magnitude, a time difference estimation chart is drawn, which can be used to quantitatively estimate the time difference of the model with arbitrary well inclination and anisotropic ratio. Through the simulation experiments of different acoustic systems and different elastic parameters, it is proved that this time difference estimation method is accurate and effective for horizontal and inclined wells in TI formation.
【作者单位】：油气资源与探测国家重点实验室中国石油大学(北京);地球科学学院 Khalifa
【基金】：supported by National Natural Science Foundation of China(No.41204094) Science Foundation of China University of Petroleum,Beijing(No.2462015YQ0506)
【分类号】：P631.81;TE243

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