多边界非牛顿湍流钻井液信道中连续波信号传输预测理论研究

Continuous wave transmission technology has broad application prospects for transmitting data from downhole sensors to the surface while drilling. The accurate identification of continuous wave transmitted to the surface is critical to the achievement of the technology, and accurate prediction of the signal feature of the surface wave can reduce the identification difficulty and improve recognition accuracy. While there are no theoretical research reports on the continuous wave prediction. To predict the surface continuous wave, an effective transmission model and an accurate signal feature of the downhole continuous wave is needed. The existing research on the generation and propagation of the continuous wave, does not comprehensively consider the impact of non-Newtonian fluid, turbulent flow, and multiple reflection boundaries. Besides, the existing propagation model is difficult to apply for a wider frequency band. The proposed project is to study a propagation and prediction method of the continuous wave in the mud channel considering non-Newtonian fluids, turbulent flow and multiple reflection boundaries. The effects of the frequency, non-Newtonian fluid, turbulent flow and reflection boundaries on the transmission characteristics of the continuous wave signal are explored, and a transmission model is established for a wider frequency band of continuous wave. Based on the model and the optimized rotary valve which is used to generate continuous wave, the effect of the well depth and the reflection boundaries on signal feature of the downhole continuous wave is analyzed, and a feature model of the downhole continuous wave is built. Then, based on the frequency-domain conversion of the transmission model and the signal feature model, the prediction model of the surface continuous wave is established, and the effect of the well depth, the signal frequency and the reflection boundaries on signal feature of the surface continuous wave is studied. This project will propose a propagation and prediction theory on the continuous wave, and provide theory support for the development of continuous wave generator and signal receiver.

钻井液连续波数据传输技术是一种具有广阔应用前景的井下信息数据传输技术，能否正确识别传输至地面的连续波是实现连续波信号传输的关键问题，准确预测地面连续波信号特征可降低其识别难度、提高识别准确度，但目前缺乏连续波信号传输预测的理论研究。要预测地面连续波信号，需确定井下连续波的信号特征及传输模型。已有对连续波产生与传输的研究未综合考虑钻井液的非牛顿湍流特性及多反射边界的影响，且传输模型在信号的高低频状态下表达不统一。本项目基于多边界非牛顿湍流钻井液信道，研究连续波信号传输预测方法。通过分析频率、非牛顿湍流特性及反射边界对连续波传输的影响，建立具有较宽频带适应性的传输模型；结合该传输模型及经优化设计的旋转阀，分析井深与反射边界对井下连续波信号特征的影响，获取信号特征的理论描述；基于井下连续波信号特征及传输模型的频域表达，建立地面连续波信号传输预测模型，揭示井深、信号频率、反射边界对地面连续波信号特征的影响规律，为连续波发生器和地面接收器的研发提供理论依据和技术基础。

钻井液连续波信号传输技术在随钻测量和随钻测井领域将会有非常广阔的应用前景，连续波在非牛顿钻井液传输、衰减和预测是影响连续波信号传输技术应用的关键问题，为此，本项目开展了多边界非牛顿湍流钻井液信道中连续波信号传输预测方法的研究。针对目前连续波传输模型难以适应较宽信号频带的问题，尤其是考虑到非牛顿钻井液湍流流动状态以及钻井液信道多反射边界的特点，将Navier-Stokes方程、质量方程、瞬态流体动力学理论与信号频率对壁面剪切应力的影响规律相结合，建立了非牛顿湍流钻井液信道中具有较宽频带适应性的连续波传输模型，并构建钻头、信号发生器、空气包、泥浆泵等反射边界条件的数值模型。综合考虑连续波旋转阀轴向和径向间隙的影响，结合薄壁孔节流与流体动力学理论，提出了产生正弦压力波的连续波旋转阀优化设计方法，成功研制了能够产生正弦压力波的连续波旋转阀。基于传输模型和旋转阀优化设计方法，深入分析了深井井下连续波信号波形特征的影响，发现：井下连续波幅值随着频率的变化呈周期性变化，其主要受钻头反射的影响，且其变化周期与反射距离呈反比、与波速大小成正比。并基于傅里叶变换理论和传输线理论，构建了井下连续波信号特征及传输模型的频域表达，实现了多边界非牛顿湍流钻井液信道中连续波信号的传输和预测。通过搭建CFD、Matlab与Solidworks联合仿真系统和模拟真实钻井工况的室内实验系统，项目研究过程中所提出的模型和方法均得到了有效的验证。本项目通过研究多边界非牛顿湍流钻井液信道中连续波信号传输模型，实现了具有较宽频带适应性的连续波信号传输衰减的准确分析，并结合连续波波形特征影响规律，有效解决了钻井液连续波在复杂钻井液信道中的传输与预测问题，并为信号发生器和地面接收器的研发提供理论依据和技术基础。