神狐海域天然气水合物层分解井中电学监测效果模拟与分析

NUMERICAL EVALUATION OF MULTI-ELECTRODE RESISTIVITY LOGGING MONITORING OF GAS-HYDRATE DECOMPOSITION IN SUBMARINE RESERVOIR IN SHENHU AREA, SOUTH CHINA SEA

为实现天然气水合物开采过程中水合物层分解状态实时监测,基于静电场理论和监测井布设特点设计了一套电极阵列式井中电学监系统。以南海神狐海域天然气水合物远景开采区为研究区,总结归纳水合物开采过程储层分解和电阻率变化特点,构建不同开采阶段储层地质及电阻率模型,模拟利用设计系统对水合物层进行探测,正演计算得到不同装置形式探测电阻率剖面图像,随后对图像进行对比分析,界定该系统对水合物层分解状态的探测能力。研究结果表明,利用偶极装置探测的电阻率和相对电阻率剖面可准确确定不同饱和度水合物层界面位置,水合物分解区范围,分解区边界定位误差可小于0.5m。井中阵列式电学监测系统能够有效进行水合物层分解状态监测,具有良好的应用前景。

In order to real-time monitor reservoir decomposition state during hydrate exploitation,a multi-electrode resistivity logging is designed based on electrostatic field theory and the layout characteristics of monitoring well.The system was applied for a gas-production prospect field in the Shenhu area,of the South China Sea,for which geological models and resistivity models were established for target reservoirs in different production stages,to evaluate the detection capability of hydrate decomposition and its variation.Resistivity sections of different electrode arrays were simulated,and the resistivity sections were compared for the analysis of reservoir decomposition.The results indicate that the resistivity or relative resistivity sections detected by the dipole-dipole array could determine accurately the interface of reservoirs of different saturation degrees and the range of hydrate decomposition,and the error of decomposition zone boundary could reach within 0.5m.Therefore,the multi-electrode resistivity logging could monitor the reservoir decomposition effectively in high resolution and low cost,and its application shall be promising and the research value significant.