Field Applications of ERD Hole Cleaning Modeling

Abstract

SPE/IADC Members Abstract With the ever-increasing measured depths and horizontal displacements in extended-reach (ERD) wells, good hole cleaning remains a major challenge. Recently a hole cleaning model for fluids in laminar flow was presented to the industry. Since its introduction, the model has been used on many occasions to characterize hole cleaning efficiency in post-well analysis, evaluate fluid performance during the drilling of ERD wells, and to predict fluid rheological properties and pump output levels for optimum cleaning in pre-well planning. In this paper, four field applications of the hole cleaning modeling in ERD and deviated wells are discussed. In these cases, the hole cleaning model was used to predict intervals of hole cleaning problems and identify certain ranges of fluid rheological properties that promoted good cleaning. Introduction The hole cleaning model (hereinafter referred to as "the model") utilizes the following to mathematically describe the ability of a drilling fluid in laminar flow to clean drilled cuttings out of a wellbore:–Herschel-Bulkley rheological modeling of drilling fluids - Annular velocity modeling valid for concentric and eccentric drill pipe cases–Particle settling velocity modeling for static and dynamic cases–Lift factors calculated in a vertical plane under the eccentric drill pipe. This hole cleaning model is different from other published models in that it exclusively deals with the area lying immediately below the eccentric drill pipe. This specific annular cross-sectional area is chosen because this is where cuttings bed accumulation begins to occur. In this model, the position of the drill pipe while rotating in the eccentric annulus is the greatest unknown. A particular level of drill pipe eccentricity () is input to cover those situations when the rotating drill string is lifted off bottom. Further complicating things, in a skewed annulus, there are an infinite number of eccentricities at a given angle of deviation. For the high angle situations where the drill string is being rotated, a drill pipe eccentricity level 0.5 is often used. In this model, operational activities that can promote increased hole cleaning on a temporary basis are not taken into account. These activities can include:–Frequency and duration of trips–Application of backreaming–Application of viscous/non-viscous or weighted sweeps–Increased circulation times–Limits on penetration rates This model is purposely constructed to characterize hole cleaning efficiency on a steady-state basis where the hole is being drilled in a rotary (eg, non-sliding) mode. After its development, the model was tested in a number of drilling situations to ensure it was a valid working tool. As part of the validation process, data from Statoil's well Statfjord C-02, a previous world-record ERD well for horizontal displacement, was analyzed according to this model. Concepts learned from this in-depth investigation were then later applied on another Statoil ERD well, Sleipner A-2. P. 287^