钻杆偏心情况下的随钻声场理论与实验研究

Acoustic logging while drilling is a key technology for the exploration and development of complex reservoirs. In applications, the complex movement of dill pipe will hardly make the tool centralized. However, most of the current studies about acoustic logging while drilling focus on the case when the drill pipe is centralized. It is necessary to study the logging response for the eccentric tool, which is closer to the real drilling environment and will be helpful for the new tool design and data processing. To understand the wave-field for acoustic logging while drilling with the eccentric drill pipe, numerical methods such as parallel FDTD and FEM will be developed for numerical simulations of the acoustic logging while drilling with the eccentric drill pipe. Furthermore, acoustic measurements about the acoustic logging response from the eccentric drill pipe case will be done based on the existing scaled acoustic logging-while-drilling measurement system. Then the effects on the wave-field from sand and shale formation and the tool with different eccentric case will be considered in the study. Based on the studies, the basic of the theory and experiments about the acoustic logging response when the tool is off-center will be set up. And the characteristic of wavefield will be illustrated. We hope to develop an effective scheme to quantify the effects of tool eccentricity on acoustic logging-while-drilling measurements which could provide critical information for geo-steering. And then the data processing and interpretation flow for the acoustic logging-while-drilling with the eccentric drill pipe can be developed. The research results would pave a way for the development of acoustic logging tool and data processing and interpretation.

随钻声波测井是复杂油气藏勘探与开发的关键技术之一，钻杆钻进时的复杂运动使钻杆难以严格居中。现有的研究主要关注钻杆居中时的随钻声场，研究钻杆偏心情况下的随钻声场更符合随钻声波测井的真实环境。本项目拟从数值模拟和物理实验的角度开展如下研究：（1）建立适合钻杆偏心情况下的随钻声场的数值模拟计算方法；（2）利用现有的随钻声波测井实验设备，实现缩比的钻杆偏心情况下的多极子随钻声波测量；（3）研究砂岩及泥岩地层中、在钻杆偏心程度不同时的随钻波场及探测系响应特征。旨在建立钻杆偏心时随钻波场理论和实验基础，揭示钻杆偏心时随钻波场的分布特征及传播规律；建立基于声波测井资料的定量评价钻杆偏心程度的方法；开发钻杆偏心时的测量数据校正算法；完成钻杆偏心时的随钻声波测井资料处理解释流程。研究成果将为我国随钻声波测井仪器的自主研发及资料处理解释奠定理论基础。

地质导向技术是可以确保钻头在目标层位了安全、准确、高效地钻进。该技术需要实时掌握井下钻头位置和井周速度结构的准确信息。然而复杂的钻井环境，如钻井噪声、钻杆的存在及其复杂运动，会使在钻井的同时获得这两个关键参数十分困难。本项目通过改进数值模拟代码和改造物理实验模型，研究了钻井环境下的声波波场特征，考察了声源频率、岩性、钻杆性质、及钻杆偏心程度对声波全波波场及探测系响应特征的影响。建立了钻杆偏心时随钻波场理论和实验基础，揭示了钻杆偏心时随钻波场的分布特征及传播规律。提出了利用方位全波形相位差来精准定位钻头位置的方法。建立了井筒岩石声学划分新方案，对慢地层的横波速度，提出了新的测量模式（低频偶极子测量模式），增强了信噪比，实现纵波和横波速度的同时测量。对快地层纵波测量，提出采用高阻抗的钻杆材料替换现有的钢钻杆，避免了刻槽，实现地层纵波速度直接测量，保障了钻井安全与效率。针对钻杆偏心带来的地层速度测量的误差，提出了一种方位全波形加权平均的数据校正方法，可将这种测量误差控制到4%以内。