New Aspects of Torque-and-Drag Modeling in Extended-Reach Wells

Abstract

The length and inclination of wells have increased significantly the past decades. The record horizontal departure today is about 11 km from the platform. Because of this evolution the number of offshore platforms to drain a field has been significantly reduced. Excessive torque and drag can be critical limitations in extended-reach drilling (ERD). Torque and drag modeling is regarded as an invaluable process to assist in well planning and to predict and prevent drilling problems. It discusses how to use torque and drag calculations and measurements to plan long-reach well profiles, to execute drilling operations that minimize torque and drag effects, to monitor hole cleaning, and to plan jarring operations. Torque and drag models have proven to be useful in all three stages of an extended reach well: planning, drilling and post-analysis. During planning phase the models are used to optimize the trajectory design to minimize the torque, drag and contact forces between drillstring and borehole wall. Used together with monitoring of hole conditions during drilling, T&D models are particularly useful in diagnosing hole cleaning problems, impending differential sticking, and severe doglegs as well as determining the possibility of reciprocating casing during cementing operations. In post-analysis the models help to determine true causes of hole problems that previously were unexplained or attributed to other factors such as mud weight, mud chemistry or problem shales.In this study a general overview on most of the available literature on the subject is presented. Different models that have been developed for torque and drag predictions along with pros and cons of the models will be discussed and the validity will be checked by applying the model for one field case study from an ERD well in North Sea. The field case also demonstrates the challenges and importance of buoyancy effects and well path effects.

Numerical modelling and field experimental validation of the axial load transfer on the drill-strings in deviated wells

“…In order to improve the efficiency of axial load transfer, a great deal of theoretical and experimental works focusing on drill-strings' drag force have been carried out (Mirhajmohammadabadi et al, 2010). In the conventional approach (Johancsik et al, 1984), drill-strings were considered as a cable under tension, the so-called soft-string model, which can be mathematically expressed as…”

The Effect of Different Drilling Fluids on Mechanical Friction

“…An earlier investigation showed that parameters such as mud properties, well trajectory, and the quality of hole cleaning have influence on the mechanical friction. This has been stated by several researchers; [5,6].…”