Dynamic Well Intervention Modeling
- Kenneth Ray Newman (Knewman Engineering)
- Document ID
- Society of Petroleum Engineers
- SPE/ICoTA Coiled Tubing & Well Intervention Conference and Exhibition, 27-28 March, The Woodlands, Texas, USA
- Publication Date
- Document Type
- Conference Paper
- 2012. Society of Petroleum Engineers
- 4.2 Pipelines, Flowlines and Risers, 1.6.9 Coring, Fishing, 1.6.1 Drilling Operation Management, 3.2.2 Downhole intervention and remediation (including wireline and coiled tubing), 1.6 Drilling Operations, 1.14.1 Casing Design, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 1.10 Drilling Equipment, 1.4.4 Drill string dynamics
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A dynamic soft-string finite-element torque and drag model for modeling coiled tubing, wireline and drilling operations in a wellbore has been developed. The model includes the ability to simulate axial and torsional stick-slip for complex dynamic situations such as stall torque, jarring and yo-yoing. This paper documents the equations used to develop this model, compares model results with analytical equations and presents several example simulations performed by the model.
Types of Models
There are many numerical models available for modeling downhole forces and torques for wireline (WL) (which includes slickline, electric line and braided cable), coiled-tubing (CT) and drill-string (DS). The generic term "string?? will be used to refer to a conveyance conduit composed of any of these 3 conveyance methods. These models are often known as torque and drag models, or as tubing forces models, or sometimes well intervention models. Most of these models are "soft-string??, which means the bending stiffness of the pipe is ignored. Some are "stiff-string?? which means the bending stiffness is included in the calculation. Stiff-string modeling is typically much more complex than soft-string modeling. Except in special situations, the bending stiffness of the pipe in the well does not significantly affect the forces in the pipe, and thus the less sophisticated soft-string models are sufficient for most applications. Most soft-string models do contain special calculations for specific stiff-string phenomena such as buckling (and the associated wall contact forces) and bottom-hole assembly (BHA) or tool bending. The special situations in which stiff-string models are required include running pipe in a hole with small clearances (e.g., casing in a torturous open hole), or running around severe bends (e.g., pushing through an elbow in a pipeline).
Most of the models available on the market (both soft-string and stiff string) are "steady-state?? models which means they do not include dynamic forces in their calculations. Steady-state models allow the string to be moving at a certain axial speed and possibly rotating at a certain constant RPM. But they do not consider the acceleration forces which occur when there is a change in speed (axial and/or rotational). Of the models that do perform dynamic simulations (References 2-10), few include the "stick-slip?? phenomena. Stick-slip occurs when a portion of the string stops moving for a short period of time. Once it stops, the force required to overcome static friction is greater than the force required to overcome dynamic friction. When the string begins to move there will be a sudden jerk as the friction force changes from static to dynamic friction. Thus there is often a repeated sticking and slipping instead of smooth, continuous motion.
|File Size||575 KB||Number of Pages||15|