An Innovative Model For Drilling Fluid Hydraulics

Abstract

Abstract The hydraulic system plays an active role during drilling operations. Its proper design can accelerate the drilling effort and lower the overall well cost. It is very important to predict the exact pressure distribution along the well and the circulating temperature distribution in the fluid. This paper describes an innovative hydraulic computer program developed in Agip. The program calculates the rheological parameters of drilling fluid based on the viscometer readings. The rheological models of Newton, Bingham, Power law and Herschel-Bulkley are considered. The program calculates also the temperature profile of drilling fluid and takes into account the temperature effect on the rheological parameters, when available viscometer readings at different temperatures. The use of Herschel-Bulkley model and the temperature effect estimation improve the flow modelling capability during drilling fluid circulation and permits to better study and quantity the influence of hydraulic parameters, thus allowing better planning. It will be also considered case histories with comparison of calculated and field data coming from Agip ultradeep wells experience. Introduction The most important effects of hydraulic system on the well are:–control subsurface pressures;–evaluate pressure increases in the wellbore during mud circulation;–remove cuttings from the well; minimise hole erosion due to the mud washing action during circulation;–increase penetration rate;–size surface equipment such as pumps;–provide a buoyant effect to the drillstring and casing;–control surge pressures created by lowering pipe into the well;–minimise wellbore pressure reductions from swabbing when pulling out of hole the pipe. P. 77