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.

Hole Cleaning during Drilling Oil and Gas Wells: A Review for Hole-Cleaning Chemistry and Engineering Parameters

“…Berg et al developed a fowchart for ensuring efective displacements for wellbore cleanliness of open holes and cased holes prior to running completion by depending on nephelometric turbidity units (NTUs), which are a measure of the opacity of the fuid used for displacements. Te main indication of fuid cleaning efectiveness during wellbore cleaning displacement is no remaining drilling mud in the top of the upset connections [173]. Njobuenwu and Wobo conducted an experimental study and concluded that the ES of an oil-based drilling fuid decreases as the concentration of modifed bentonite (organophilic clay) increases.…”