基于蒙特卡洛方法的高分辨率中子测井技术研究

发布时间：2018-05-24 09:18

本文选题：蒙特卡洛 + 商分辨率　；参考：《浙江大学》2015年硕士论文

【摘要】：本文基于放射性测井中经常使用的蒙特卡洛方法,采用蒙卡模拟软件MCNP,建立补偿中子测井模型,通过大量粒子的模拟计算,研究了纵向分辨率与源距的响应关系；不同近、远源距组合下对探测器计数率,计数比,孔隙度灵敏度等影响情况；不同探测器尺寸对计数率,计数率比值及孔隙度灵敏度的影响；不同屏蔽材料的屏蔽效果。确定了中子测井纵向分辨率与源距成线性关系,对于采用双源距比值求取孔隙度的补偿中子测井来说,纵向分辨率主要取决于长源距,大小基本与长源距的长度基本一致。高分辨率中子探测器结构的设计主要考虑了计数率,纵向分辨率和孔隙度灵敏度等因素,长源距应尽量短,长短源距间隔应尽可能大,结合工程实际,确定合适的源距,探测器尺寸。分析了对中子测井孔隙度产生影响的各个因素,然后利用数值模拟的方法对井眼环境的影响进行了校正,包括井径,泥饼,井眼间隙,挖掘效应,岩性校正和泥浆矿化度校正,对各个影响因素做出了校正图版。经过现场实验验证,仪器重复性一致性良好,与传统补偿中子仪器的分辨率只有0.6米左右相比,纵向分辨率得到明显提高,分层能力更强。
[Abstract]:Based on Monte Carlo method often used in radioactive logging, this paper uses Monte Carlo simulation software MCNP to establish a compensated neutron log model. Through the simulation of a large number of particles, the response relationship between the longitudinal resolution and the source distance is studied, and the influence of the counting rate, the count ratio and the porosity sensitivity under the combination of different near and far source distance is influenced. The influence of the size of the detector on the counting rate, the ratio of counting rate and the sensitivity of porosity, the shielding effect of different shielding materials, the linear relation between the longitudinal resolution and the source distance of the neutron log is determined, and the compensation neutron log which uses the ratio of the double source distance to the porosity is determined mainly by the long source distance and the size. The design of the structure of high resolution neutron detector mainly considers the counting rate, the longitudinal resolution and the porosity sensitivity. The long source distance should be as short as possible and the distance between the long and short source distance should be as large as possible. In combination with the engineering practice, the appropriate source distance and the detector size are determined. The porosity of the neutron log is analyzed. The influence of the borehole environment is corrected by numerical simulation, including well diameter, mud cake, hole clearance, excavation effect, lithology correction and mud mineralization correction. The correction chart is made for each influence factor. After field experiments, the repeatability of the instrument is good and the traditional compensation is well compensated. The resolution of the neutron instrument is only about 0.6 meters, and the vertical resolution is obviously improved and the stratification ability is stronger.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.817

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