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掌握真实地温梯度对于深入了解易受温压场控制的天然气水合物赋存状态具有重要意义。在南海天然气水合物钻探区获取的地温梯度主要以海底表层的热流探针方式为主,由于海底表层尚未压实,地层物理属性多呈现高渗透性,易受到海底底流影响,导致了部分地温梯度无法推算到较深地层。而另一方面,井下原位温度测量虽然可获取真实的地温梯度,但其经济成本昂贵并且时效性低。为此本研究依据天然气水合物钻探井位单一非平衡态温度测井数据和钻井进程,在前人的数学模型基础上,尝试现场快速恢复地层地温梯度的操作,并利用有限的原位地温梯度进行对比分析。研究结果表明,该方法在一定程度上具有适用性,当测井温度变化率在较均匀层段(例如A-B段),根据测井进程可大致估算具有参考意义的原始地温梯度。但应用该方法时也须谨慎,避免使用测井温度变化率在非均匀的数据段(例如B-c段),因为模型中受到数学条件而忽略的多种不确定因素的权重,在外部参数环境波动较大时有可能增加,从而减弱了模拟过程中时间因子的主要作用量。
Grasping the true geothermal gradient is of great significance for understanding the state of gas hydrate controlled by temperature and pressure field. The geothermal gradient obtained in the South China Sea gas hydrate drilling area is dominated by the heat flow probe of the surface of the seafloor. Because the surface of the seafloor has not been compacted, the physical properties of the formation are mostly highly permeable and vulnerable to the underflow, resulting in the partial geothermal gradient Can not be calculated to deeper strata. On the other hand, underground downhole temperature measurement can obtain the true geothermal gradient, but its economic cost is expensive and its timeliness is low. Based on the previous mathematical models, based on the single non-equilibrium temperature well logging data and drilling process of gas hydrate drilling well, this study attempts to quickly recover the geothermal gradient of formation on site, and utilizes the limited in-situ geothermal gradient For comparative analysis. The results show that this method is suitable to a certain extent. When logging rate of temperature change is in a more uniform interval (for example, section A-B), the original geothermal gradient with reference can be roughly estimated according to the logging process. However, caution should be exercised when applying this method, avoiding the use of logging temperature variability in non-uniform data segments (eg, Bc) because the weights of multiple uncertainties in the model that are subject to mathematical conditions and negligible fluctuations in external parameters Larger time may increase, thus weakening the main role of the time factor in the simulation process.