裂缝内钻井液的漏失规律研究

Leakage laws research of drilling fluid in fracture reservoir

舒刚 孟英峰 李红涛 贾红军 严俊涛 李海旭

SHU Gang MENG Yingfeng LI Hongtao JIA Hongjun YAN Juntao LI Haixu

油气藏地质及开发工程国家重点实验室?西南石油大学，四川成都　610500

State Key Lab of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China

为了揭示裂缝性漏失宏观规律和缝内微观流动特征的机理，通过室内实验研究了压差、缝宽、钻井液黏度变化时平板型光滑裂缝的漏失规律，结合CFD数值模拟分析了天然裂缝面的起伏粗糙特征对漏失的影响，讨论了影响漏失各个因素的特点。研究表明：缝宽和压差是决定漏失速率的关键因素，漏失速率对钻井液黏度的敏感程度相对较弱；裂缝面的整体起伏使其在局部对顶接触是一般裂缝形成有效流道的主要原因，而形成微裂缝有效流道的主导因素则是微凸体的分布与形态特征；天然裂缝面存在局部接触，从而引起液体流动阻力增大、流道变得更加曲折，漏失速率减小。该研究成果为裂缝性地层的漏失评价、堵漏材料优选、井漏控制提供了一定的理论依据。

To disclose the mechanism of macro laws of fractured lost circulation and microscopic flow character in fracture, the lost circulation laws through smooth fracture while pressure differential, fracture width and drilling fluid viscosity changing were studied by experimental method, and the effect of undulating rough features of natural fracture surface to lost circulation laws was analyzed through CFD simulation. Then the features of influence factors to lost circulation were discussed. The results indicated that the dominant factors affecting leakoff rate were fracture width and pressure differential, and drilling fluid viscosity was a weak factor. The overall undulating of fracture surface making it contacted locally was the main reason of forming effective flow path, while the dominant factors forming effective flow path for micro fracture was the distribution and shape features of asperities. Natural fracture surfaces contacted partially, resulting in flow resistance increase, flow path being more tortuous, so the leakoff rate decreased. It provided a theoretical basis for lost circulation evaluating, leakoff shutoff material selecting, and lost circulation controlling.