瞬变电磁法井间油气储层识别

Cross-well is the main area of residual oil, and the key of improving recovery efficiency is to precisely locate and accurately recognize the reservoir.Aiming at the area formed by open hole well and adjacent casing well, the transient electromagnetic Emission and Receiver System(ERS) uses open hole as emission,and casing well as receiver. the whole space time-domain electromagnetic detection and reservoir recognition theory model is built,The analytical solution Combining numerical solution method is used, the formation resistivity is inversed,so the reservoir distribution can be recognized. Design method for ERS is as follows: in order to use the features of emission well and receiver well,impose transient electromagnetic signal on the magnetic dipole in the emission well,receive formation output signal throughthe electric dipole and magnetic dipole in the receiver well, at the same time improve the signal-to-noise ratio through parameter optimization.The advantages of this method are good resistivity sensitivity, the long detection distance ,which features can be described by time. Compared to other methods, which has obvious advantage on the aspect of exploration environmental adaptability,geological problem flexibility,object resolution. The main content of this project contains: the ERS parameter optimization,analysis of casing influence factor,inversion and test technology research of reservoir features. The expectation results are as follows: Modeling for a cross-well detection system, theory model for reservoir recognition and inversion theory for cross-well.

井间是剩余油分布的重要区域，对井间储层的准确识别和精确定位是提高采收率的关键。本项目针对裸眼井和相邻套管井构成的区域，采用裸眼井发射、套管井接收的方式构建瞬变电磁发射与接收系统，建立井间时域电磁探测和储层识别理论模型，采用解析解和数值解相结合的方法，反演出表征地层属性的电阻率，进而识别储层的分布情况。发射与接收系统的构建方法是：在发射井中给磁偶极子施加瞬变电磁信号，在接收井中通过磁偶极子和电偶极子接收地层响应，以利用发射井和接收井的特点，通过对偶极子参数的优化来提高信噪比和探测距离。其优点是对电阻率敏感，探测距离大且距离特性可以用时间来描述，对勘探环境的适应性、地质问题的灵活性以及目标的分辨率等方面比其他方法有明显的优势。项目的主要研究内容包括发射与接收系统的参数优化、套管影响因素的分析、储层特性的反演和实验研究。预期成果是井间探测系统的构建方法、储层识别的理论模型和井间储层的反演理论。

井间是油气资源分布的重要区域，井间油气储层的准确识别是提高采收率的关键。经过注水开发后只能采出地下总储量的30%左右，约70% 的原油仍然残留在井间成为剩余油，这些剩余油储量对于增加可采储量和提高采收率是一个巨大的潜力。本项目以瞬变电磁信号作为发射信号，建立电偶极子和磁偶极子的物理、几何模型，分析发射和接收偶极子的线圈匝数、长度、直径等结构参数和发射信号的持续时间、周期、电流等物理参数对探测性能的影响，以井眼直径及其允许的空间作为约束条件，得到发射与接收系统的参数。通过本项目的基础性研究，形成了一种井间电偶极子和磁偶极子的物理和几何模型设计方法；分析了套管对电磁信号的影响，通过理论建模得出影响套管磁导率的主要因素，得出了磁化前后所能达到的探测性能，研制了磁化装置，采用较小的激励电流，实现了对套管的磁化处理，该方法为大斜度井、水平井等无法使用磁化机构的复杂井筒的电磁探测提供有效的方法。