A Comprehensive Study of the Combined Effects of Drilling Fluid Rheological Properties and Near Wall Turbulence on the Particle Removal From Bed Deposits in Horizontal Wells

点击翻译按钮获取中文摘要

When drilling long horizontal wells, drilled solids tend to settle down on the low side of the wellbore and form a stationary bed. Presence of stationary cuttings bed causes operational difficulties such as pack-off, excessive torque and drag, slow drilling rate, and in severe cases, stuck pipe, lost circulation, and even loss of the well control. Occasionally, drilling must stop to clean the stationary bed, which is an expensive process and must be done in a timely manner. Despite significant progress made in drilling fluids, tools, and field practices, along with more than 50 years of university and industry research, field experience indicates that hole cleaning is still a major problem in most horizontal wells. The primary motivation of this study is the lack of a reliable model for optimizing hole cleaning process. As part of the systematic efforts to develop a unified theory of hole cleaning, a comprehensive research plan is proposed here, which calls for experimental investigation of: i-) the near bed turbulence and how it relates to particle removal from bed deposits ; ii-) how the critical flow rate for the particle removal from bed deposits and bed erosion rate change with drilling fluid shear viscosity, gel strength, elastic stresses and other viscoelastic properties. Hole cleaning experiments will be conducted using a 9m long horizontal flow loop with concentric annular geometry (Outer Pipe ID= 95 mm, Inner Pipe OD= 38 mm). State of the art flow visualization techniques, Particle Image Velocimetry and Particle Tracking Velocimetry, will be used to determine local fluid and solid particle velocities. In addition, a Computational Fluid Dynamic (CFD) simulation study will be conducted to model the cuttings removal from the bed deposits. Specific objectives in this case are to: i-) Develop a CFD model of multiphase solid/liquid flow in horizontal well; ii-) Use the CFD model as a tool for upscaling results from lab to field scale; iii-) Use the CFD model for predicting time required for hole cleaning under given operational conditions and determine best combination of drilling fluid flow rate and rheological properties for minimum hole cleaning time. The number of horizontal wells drilled has dramatically increased over the past decades, however, hole cleaning still remains a challenge especially when drilling long horizontal sections. Efficient hole cleaning strategies need to be developed to reduce time associated with well cleaning. The shorter the hole cleaning time, the more time can be spent on actual drilling and, as a result, the drilling cost can be reduced significantly. Delivering an oil well at lower costs is essential in ensuring accessibility of reserves, which otherwise are not economically sound to exploit. Industry's capacity to operate safely and economically will benefit tremendously from a full-scale experimental and numerical research such as the one proposed in this study.