随钻瞬变电磁波测井三维远探测方法基础研究

Electromagnetic Logging While Drilling means a lot to geosteering and formation evaluation. However, the 3D deep detecting method and theory still need further researches. In this project, on the basis of the multi-core CPU and GPU parallel approach, by combining with time-domain adaptive hp finite element method, a 3D numerical algorithm of transient electromagnetic logging is established using transparent truncated boundary and multi-level preconditioner. By optimizing the pulse transmitting sequence patterns of transient electromagnetic wave and the antenna layout, the combination characteristics of antenna component signal and the signal synthetic method of transient electromagnetic logging are analyzed. By combining the multi-component time-domain signal measurement and broadband-domain signal processing of antenna array, the response characteristics and the sensitivity of transient electromagnetic frequency-domain distribution and time-domain decay to the geology anomalies with different position, size, and resistivity contrast are simulated. Simultaneously, methods of extracting and separating scattered wave from time and frequency spectra are proposed to determine the spatial configuration of abnormal body. In addition, according to water sink model and analog formation loops, the abnormal body measurement environment is structured for transient electromagnetic signal measurement. Finally, the detecting methods of anomalous body around wellbores for transient electromagnetic logging while drilling are proposed, which provide the apparatus development and the detecting of “looking ahead” and “look around” with theoretical and experimental basics.

随钻电磁波测井在地质导向和地层评价中具有重要作用，但在三维远探测方面，亟需在理论和方法进行深入研究，才能满足油气勘探开发的迫切需要。本项目针对随钻瞬变电磁波测井，采用CPU与GPU细粒度协同并行处理，结合时域透明截断边界及多水平预条件子，建立瞬变电磁波时域自适应hp有限元数值计算方法；优选瞬变电磁波脉冲发射序列模式和天线布置，分析天线分量信号组合特性，研究瞬变电磁波测井信号合成方法；结合天线阵列多分量时域信息测量与宽频域信息处理，模拟不同位置、尺度、电阻率对比度下的井旁异常体瞬变电磁波测井响应，分析其频域特性及时域衰减对井周异常体的敏感性，研究时域和频谱下散射波的提取和分离方法，确定井周异常体空间位形；构建以水槽模型与模拟地层环结合的井周异常体测量环境，测量脉冲瞬变电磁波信号。最终提出随钻瞬变电磁波测井的井旁异常体识别方法，为随钻电磁波测井仪器研发及钻前/井周远探测提供理论基础与实验依据。

随钻电磁波远探测技术对提升地质导向能力、进行油气藏的高效开发以及规避钻井风险具有重要意义，而现有的频率域电磁波测井方法普遍存在源距过长、资料处理困难等缺点。①本项目解决了频率域多分量感应/随钻方位电磁波测井的快速正反演问题，采用降维策略与滑动开窗相结合的方法，将复杂地质结构的3D正演简化为多个1D层状介质的正演，基于正则化Levenberg-Marquardt算法和多初值模型，实现了随钻方位电磁波测井资料的快速处理与地质结构的成像，同时为瞬变电磁波测井方法的研究提供了基础和对比。②创建了随钻瞬变电磁波测井的短源距环视、前视远探测新技术：基于“烟圈”理论，研究瞬变电磁波的井周传播特性，证明瞬变电磁波测井的远探测能力；构建瞬变多分量电磁波测井的环视边界探测模式，探测范围可达数十米，同时具备方位敏感性测量能力；通过研究线圈系的阵列布置方式，提取时间域散射场，构建瞬变电磁波测井的前视边界探测模式，可以提前数十米探测到钻前地质构造。③形成了适用于瞬变多分量电磁波测井信息的“伪反演”处理方法，研究发现地层坐标系下交叉分量随时间的衰减速度要远大于同轴/共面分量的衰减速度，由此提出了一种计算相对倾角和各向异性系数的时间域“代数”方法，对该方法的实用性分析表明，倾角的确定稳定高效，有重要的实际应用价值；此外，仪器到地层边界的距离与界面信号观测时刻之间的线性关系可用于仪器与界面距离的快速确定；瞬变多分量电磁波测井提前数十米确定倾角和距离的能力，有助于实现油藏尺度的地质导向。④研发了瞬变电磁波测井实验仪和模拟实验系统，利用圆柱体水槽配合不同浓度的NaCl溶液模拟不同电阻率地层环境，采用导电膜建立边界探测模型，通过开展物理模拟实验，验证了瞬变电磁波测井探测方法的正确性。