Displacement of Drilling Fluids and Cased-Hole Cleaning: What Is Sufficient Cleaning?

Abstract

TX 75083-3836, U.S.A., fax 1.972.952.9435. AbstractThe need for an efficient displacement of drilling fluids from cased wells prior to installation of completion equipment has been relatively undisputed in the past.Several different fluid systems has been applied as well as a variety of different mechanical tools to achieve what is considered to be a clean well in order to safely run advanced completion equipment in the well. In contradiction to the requirements related to running more advanced equipment in the wells is the fact that several of the fields on the Norwegian shelf are entering the mature phase and tail end production. For these fields the margins are less and a significant focus is put on cost efficient solutions. In many cases, the need for casing cleaning in conjunction with displacement of drilling fluids is questioned.The current paper are reviewing in detail the results from drilling fluids displacement and cased hole cleaning operations performed on 192 wells on the Norwegian continental shelf over the six past years.These wells cover a variety of different completion scenarios where both water based and oil based drilling fluids have been utilised.The results from the survey are presented with a focus on the requirements towards a clean well and the ability to measure the efficiency of the different fluid systems and operational procedures utilised.The paper discuss different casing cleaning requirements versus well completion scenarios and displacement techniques.

Evaluation of Nonreactive Aqueous Spacer Fluids for Oil-based Mud Displacement in Open Hole Horizontal Wells

“…Since acid-free microemulsion fluids are incapable of dissolving OBM solid particles, it is critical that dispersed residual filter cake solids are able to flow through the sand screen completion apertures when used in standalone screen completions. Additionally, the mechanical effects of the displacement process must be optimized for maximum fluid solids removal in the wellbore with final brine returns solids/sediments content < 1% or fluid clarity below 300 Nephelometric Turbidity Units (NTUs) 23 .…”