时域电磁法多分量储层在线监测

Reservoirs of submersible electric pump wells are conducted online monitoring during enhanced oil recovery processes such as waterflooding, it can timely master the dynamic changes of the reservoir, identify displacement fronts, analyze and evaluate displacement effects. In order to pass electromagnetic signals through the casing, utilizing the advantages of power supply and cables in submersible pump wells to magnetize the casing, reducing the relative permeability close to vacuum’s, when magnetic saturation is reached, the casing will no longer absorb magnetic field energy and excitation signals applied by the transmit probe can easily pass through the casing. On this basis, the electromagnetic probes and electrode pairs are respectively arranged in the wellbore, additionally, the electrode pairs and the casing are composed of line sources, according to the sensitivity of the time domain electromagnetic method to the reservoir conductivity, the response characteristics of the reservoir are detected from both magnetic and electric fields by electromagnetic probes and line sources respectively. The detection of the magnetic field using a three-component probe is conducive to detecting the orientation of the displacement front; The detection of the electric field utilizes the good conductivity of the metal casing to effectively improve the detection performance of the secondary field and improve the signal to noise ratio. Through the combination of electric field and magnetic field, monitoring the change course of reservoir conductivity over time, tracking and identifying displacement fronts in the process of enhanced oil recovery such as waterflooding, gas injection, polymer injection, etc.

对注水驱油等强化采油过程中潜油电泵井的储层进行在线监测，及时掌握储层的动态变化情况，识别驱替前沿，分析和评价驱替效果。为了使电磁信号穿过套管，利用潜油电泵井中设有电源和电缆的有利条件，对套管进行磁化，使相对磁导率降低到接近于真空的磁导率，达到磁饱和后，套管将不再吸收磁场能量，由发射探头所施加的激励信号可方便地穿过套管。在此基础上，分别在井筒内布局电磁探头和电极对，并由电极对与套管组成线源，依据时域电磁法对储层电导率敏感的特点，由电磁探头和线源分别从磁场和电场两个方面探测储层的响应特性。磁场的探测采用三分量探头，有利于探测驱替前沿的方位；电场的探测利用了金属套管良好的导电性，以有效地提高二次场的探测性能，提高信噪比。通过电场和磁场的相互结合，监测储层电导率随时间的变化历程，跟踪和识别注水、注气、注聚等强化采油过程中驱替前沿的推进情况，为注采工艺的调整和优化提供依据。

该项目研究时域电磁法多分量储层在线监测技术，计划通过电磁多分量获取的信号，确定驱替前沿的距离和方位，掌握驱替效果及储层的动态变化情况，提高生产井套后储层探测性能。在获得国家自然科学基金资助后，该项目进展顺利。完成了储层电磁激励理论模型的建立、一次场求解和储层响应特性研究，包括套管、水泥环和地层等非均质性的校正、电磁探头的参数优化、电源模块的设计以及套后电阻率均匀性的识别。项目已建立时域电磁法生产井储层在线监测的理论和模型、电磁探头发射与接收参数优化设计方法，可为生产井套后储层监测和评价提供理论支撑。在上述研究基础上，针对微弱信号检测问题，研究了瞬态电磁测试信号噪声抑制方法以及驱替前沿定位识别方法，包括自适应相干积累方法、基于经验模态分解方法的噪声抑制方法以及基于环形阵列的储层监测方法。先后设计了偏心阵列、多发射阵列、合成阵列等系统，并先后获得西安市鄂邑区科学技术局项目以及多个石油公司合作项目。其中，项目组设计的套后储层监测仪器获第七届中国研究生能源装备创新设计大赛国家一等奖以及第八届中国国际“互联网+”大学生创新创业大赛陕西赛区省级银奖。