Drill Pipe Rotation Effects on Frictional Pressure Losses in Slim Annuli. SPE-member Abstract The effect of rotation on the frictional pressure loss in an annulus has been studied experimentally. A direct comparison with results obtained with a 3D CFD (computational fluid dynamics) code has been performed for laminar flow. Experimental results for three fluids are presented. In this paper we will focus on two effects of rotation in a slim hole annulus. The increase in the frictional pressure loss with high rotation rates for low viscosity fluids which is caused by the onset of centrifugal instabilities. The reduction of the frictional pressure loss with rotation for high viscosity shear thinning fluids. Introduction Within the last decades there has been done a significant amount of work with the objective of predicting the frictional pressure loss for axial flow in annuli. In the oil and gas well drilling industry, especially when drilling slim hole wells, this topic is of the greatest importance as described by Marken et al. There are several works where the frictional pressure loss has been studied using real wells, thus restricting the controlled conditions of their experiments. These studies concluded that applying rotation to the inner cylinder in the annulus yielded an increase in the frictional pressure loss of the flow. This is in contradiction to the results obtained by Walker et. al. which found experimentally that flow is enhanced with drill string rotation. The reduced frictional pressure loss resulting from helical flow in annuli has also been discussed for a wider range of non-Newtonian fluids. A reason why the studies by Walker et. al. found enhanced flow is that their shear thinning fluids were quite viscous. Furthermore, they studied fairly narrow annuli. Any centrifugal instabilities were therefore suppressed and enhanced flow was observed. McCann et. al. used an especially designed slim hole flow loop and found that the frictional pressure loss for power law fluids increases with increased pipe rotation in turbulent flow and decreases with increasing pipe rotation in laminar flow. They also found a significant decree in the frictional pressure loss for power law fluids with increasing eccentricity. This decrease for power law fluids in laminar flow has been calculated numerically by Haciislamoglu et al. where a correlation for the calculation of Recc, the ratio between the frictional pressure loss with eccentricity and without eccentricity, is provided. Several other authors have studied the axial flow of non-Newtonian fluids in eccentric annuli. Chandrasekar has reviewed centrifugal instabilities. Appearance of centrifugal instabilities on axial flow results in increased frictional pressure losses. This was studied in detail by Simmers et. al. where the axial flow without inner cylinder rotation was laminar. Numerical simulations of centrifugal instabilities have been performed by Majumdar et al., Lockett et al. and a feasibility study was performed in [18]. In the study by Majumdar et al. the fluid was Newtonian and no axial flow was present. In [11] and other publications by the same authors, axial flow is present and effects of eccentricity are commented. They focused on the effect of centrifugal instabilities on cutting transport.
The application of horizontal drilling technique to improve production performance from elected tight chalk reservoirs in the Danish sector of the North Sea has shown to be technically feasible and economically viable. Maersk Oil and Gas has drilled and completed three horizontal wells with horizontal drainhole sections ranging from 1000 feet to 3000 feet and with displacement of some 9000 feet from the wellhead platform slot. The essential early planning aspects leading to evaluation and solution of preferred options are discussed. Modifications to the approach adopted as experience is gained and a generalised overview of problems, solutions and costs is included. INTRODUCTION Industry reports, in 1985, of successful cementation of a casing string in a horizontal well revived our interest in what we had reluctantly shelved a decade previously. A successful casing/liner cementation was considered a pre-requisite for a multiple fracture completion. The drilling of our first horizontal well, MFB-14, commenced in March 1987 and two more, MFB-15 and MFB-13, have been drilled and completed since then. While comparisons are difficult, and perhaps subjective, it is of some interest to note that of a total of 41 wells producing from our Dan Field, some 25% of total production comes from the 3 multi-fractured horizontal well completions. Described below are the initial technical considerations, the evaluation of and resultant changes to the initial programmes and suggested studies and developments of new techniques and tools which we believe will improve the benefits deriving from application of the horizontal drainhole concept in suitable reservoirs. RESERVOIR CONSIDERATIONS Reservoir studies were carried out to quantify the potential benefits of both open drainhole horizontal wells and multiple fractured horizontal wells in tight chalk reservoirs. The conclusions on the relative merits of horizontal wells in tight chalk reservoirs and the Dan Field in particular can be summarised as follows: Unfractured Horizontal Well A feasibility study on possible applications of horizontal wells in the Dan field concluded that a non-stimulated horizontal well would yield a productivity equal to a successfully propped fraced deviated well while the well cost would be higher. The PI improvement for a matrix acidized horizontal well compared with an optimally fractured conventional well is only marginal, however. in multi-phase fluid reservoirs where a gas cap and/or bottom aquifer is present, a matrix acidized horizontal well could be beneficial because breakthrough of the gas-water is delayed as a result of the reduction in drawdown. This was studied in detail for Danish chalk reservoirs, including Dan and it was concluded that in the low permeability Danish chalk reservoir coning would still be inevitable for realistic production rates and that no significant improvement in gas-oil or water-oil ratios could therefore be expected although the overall oilrate and recovery would still benefit from the PI improvement.
A model to predict the pressure loss for slim hole drilling has been constructed. The model, which is constructed by theoretical and numerical analysis and experimental measurements, incorporates the effect of eccentricity, drillstring rotation and rheology. Introduction Slim-hole drilling has been pursued in the last decade as a mean to drill exploration wells with a minimum of logistic support. Slimming down the well design will also give a cheaper well. However, the technique will bring new technical challenges, such as the correct estimation of ECD and kick detection. In a conventional well 90 % of the standpipe pressure originates from friction in drillstring and drill bit. In a Slim-hole well 90 % of the standpipe pressure is due to friction in the annulus. Correct estimation of the frictional pressure loss is crucial for estimating ECD, and hence also an important issue for well control.
Different philosophies exist for how to design cementing jobs in order to achieve the best possible displacement. This is due to the fact that the process is complex and that it often is difficult to measure the degree of displacement in a well. The trend towards extended reach wells and slim hole wells gives additional challenges when trying to achieve good displacement. A large amount of high quality displacement experiments have been performed in a 4m long laboratory scale loop. Laminar and turbulent flow were considered and densities, rheologies, inclination and eccentricity were varied during the experiments. In all the experiments the displacement efficiency was accurately measured. The experimental displacement data has been analyzed with statistical methods. The results from these analysis and additional simulation results have been used to develop a correlation based displacement model. This model is based on some physics since relevant non dimensional parameters are used in the correlation. This correlation gives a fast prediction of the displacement efficiency and is an efficient engineering tool for optimizing the displacement efficiency. Modeling of the displacement process is complicated due to fully three dimensional geometry and flow of non-Newtonian fluids with different rheologies and densities. The displacement process has been modeled and simulated using a general three dimensional flow program. Results from the simulations have been compared against the experimental results. Results from simulations are found to compare well for the cases considered. The general flow simulator is based on basic physical laws. This enables accurate prediction of displacement efficiency at field conditions. Introduction Investigators have performed laboratory experiments in order to study the displacement process in detail. Tehrani et. al. did experiments for laminar conditions in an annulus formed by two pipes. They found that when covering a wide range of parameter space. the complexity of the displacement process did not allow for maIling straight forward global rules for improving the displacement efficiency. Silva et. al. performed displacement experiments in an annulus formed by an inner pipe and an artificial permeable formation. A complete cementing operation was performed including pumping of a drilling fluid with cuttings, spacer, washer and cement. The cement was allowed to set and the section was cut in slices for visual inspection. They found that the axial velocity component as a function of the radial distance in the annulus should be as flat as possible in order to achieve the best displacement. Lockyear et. al. and Ryan et. al. observed that a necessary condition for efficient displacement is that the pressure gradient has to exceed the combined forces due to drilling fluid yield stress and the density difference between cement and drilling fluid. Attempts have been made to use analytical methods to model the displacement process. Flumerfelt investigated laminar displacement in a vertical concentric annulus within the parallell plate approximation. Nguyen et. al. studied displacement in a concentric horizontal annulus. These investigations are of limited value because of the assumptions done in order to obtain analytic solutions. Haut et. al. and Graves et. al. computed displacement of one non-Newtonian fluid by another with higher density in a vertical, concentric annulus. Results from the simulations illustrated the temporal evolution of vortices and instabilities. Szabo and Hassager studied the displacement of one Newtonian fluid by another with higher density in a vertical annular geometry. Both analytical and numerical methods were used to study the displacement process.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractKristin is a HP/HT field developed on Haltenbanken offshore mid-Norway. The Kristin development consists of 4 templates with a total of 12 subsea wells. The inclination through the reservoir ranges from 28 to 85 degrees. The reservoir at approx. 4600mTVD (15092 ft) has an initial pore pressure corresponding to 1.96sg EMW (16,36 ppg) and a temperature of 172°C (342°F). With a water depth of approx. 360m (1181 ft), a MW of 2.05sg (17,11 ppg) is needed to be able to maintain a riser margin. Three different drilling fluid systems have been used in the reservoir section: 1) Cs/K-COOH clear brine system. 2) Invert emulsion HP/HT OBM. 3) Invert emulsion HP/HT OBM with ultra fine weight particles. Challenges such as ECD management, hole stability, formation damage, weight material sag and operating on subsea HP/HT wells during harsh winter conditions had to be addressed both in the planning and the operational phase. In this paper the background for selection of the drilling fluid is briefly described and especially the rationale behind using three different systems. The paper highlights operational experiences to illustrate how the drilling fluid systems influenced and coped with the challenges of drilling subsea, high angle HP/HT wells. The paper provides a discussion of the pros and cons of the different fluids systems. Finally the paper identifies some of the challenges that lie ahead as the production has started and the reservoir starts to deplete.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.