Investigating the Impact of the "Tool Joint Effect" on Equivalent Circulating Density in Deep-Water Wells

Abstract

Precise prediction of Equivalent Circulating Density (ECD) is one of the most important challenges during drilling operations. This becomes more vital in deep-water offshore wells in which formation pressure is very close to the fracture pressure. In addition, techniques such as Managed Pressure Drilling (MPD) rely on the precise estimation of frictional pressure losses. Although many theoretical and experimental studies have been conducted on fluid flow through pipes and annuli to predict the pressure losses, majority of them undermine or simply ignore the effect of tool joints. A few studies that take the effect of tool joints into account indicate that it can have significant effect on pressure loss. Therefore, there is a strong need to determine the amount of additional pressure loss caused by the tool joints. This paper presents a Computational Fluid Dynamics (CFD) approach to investigate the effect of tool joint on annular pressure losses. The utilized software package in this simulation study uses Finite Volume methods to solve the problem. The effects of important parameters such as flow rate, mud type, mud weight and mesh size are investigated. The pressure loss in the annuli, with and without tool joint, is obtained and additional pressure loss due to presence of tool joint is calculated accordingly. Simulation results show that the ratio of annular pressure loss with tool joints to the pressure loss without tool joints (α) strongly depends on the flow regime. In Laminar flow, this ratio remains relatively constant, regardless of the type of the drilling fluid. In turbulent flow, it increases rapidly with increasing Reynolds number and can be precisely estimated by the proposed correlation. It has been found that in deep offshore wells and high range of operational flow rate, the additional pressure loss due to tool joints can be as high as 30% of the total frictional pressure loss and must be taken into consideration during ECD calculations.

Modelling the Effects of Temperature and Pressure on Equivalent Circulating Density (ECD) During Drilling Operations Using Artificial Neural Networks

“…Highoose Limited [6] stated that a greater risk of failure in HPHT wells still exist due to the high stress environment (tension and compression), high operating temperatures, high temperature gradients in these wells, chemical action of well fluid constituents enhanced by the elevated temperature encountered downhole etc. Due to the incompressible nature of drilling fluids (liquids), an increase in the downhole wellbore pressure will only have appreciable effect on the drilling fluid rheology at higher pressures, whereas a smaller increase in temperature may cause a decrease in ECD [7,8,9,10,11]. Moreover, one of the critical features of HPHT wells is the existence of narrow drilling windows as well as high bottom hole temperature which poses a number of problems to management of drilling muds at HPHT conditions and well control issues [3].…”

Determination of drilling fluid rheology under downhole conditions by using real-time distributed pressure data

“…For more accurate prediction of annular pressure losses, Computational Fluid Dynamics (CFD) approaches can be applied (Hashemian (2005) and Karimi Vajargah et al (2014)). Since CFD analyses are cumbersome and time-consuming, results are usually generalized and published in terms of correlations.…”

CFD Analysis and Model Comparison of Annular Frictional Pressure Losses While Circulating Yield Power Law Fluids

“…It was a good example of realistic conditions that incorporates various drillstring configurations such as, concentric, partially eccentric and fully eccentric annuli. Karimi Vajargah et al (2014) investigated the effect of tool joint on annular pressure losses by using a CFD approach. They proposed a generalized correlation from the CFD results for the considered geometry.…”