Abstract

The development of new drilling technologies like extended reach drilling (ERD) or slimhole drilling and the reinforcement of environmental legislations require new adaptation of water based formulations. Good lubricating properties of the mud that would minimize any risk of differential pressure sticking of the pipe are of major impact on the efficiency of drilling operations.

A biodegradable and non toxic ester based lubricating formulation has been developed that significantly reduces torque and pipe drag. Efficiency of the lubricant has been confirmed by an extensive testing under strictly controlled laboratory conditions simulating actual drilling conditions. The lubricant is very efficient on many different water based formulations, even containing high content of salts or solids, cases where classical lubricants are usually poorly efficient. The ester based lubricant is also very efficient for low solids formulations used for slimhole drilling. It is readily dispersible in water based muds and does not affect mud rheology nor filtration behavior nor any other mud property; in some cases its addition may even improve the filtrate loss reduction. Furthermore this highly efficient additive is completely biodegradable and non ecotoxic. Field tests carried out in Africa, north sea and US have largely confirmed the laboratory results presenting, for instance, a torque reduction of more than 40%.

Introduction

Environmental constraints concerning drilling fluids require new formulations that are non toxic for replacing mineral oil based muds. Water based muds are good candidates but new drilling conditions (deep drilling, slimhole drilling, extended reach drilling, multilateral drains) rise specific technical problems in particular concerning lubrication and risk of differential pressure sticking. When drilling long sections of highly deviated wells large friction between the drill pipe and the wall will increase torque and power required to rotate the drill pipe and the stress on the drill pipe. It could also interfere with running the pipe in and out of the hole. As a consequence good lubricating properties of the mud will improve greatly drilling operation efficiency.

An joint research programme has been undertaken by IFP and FINA for developing a new performant and non toxic lubricant in order to increase drilling rates in operations using water based muds. The major goal set forward when starting the ester based lubricant R and D programme was to achieve superior performance combined with full ecological and human safety.

This paper describes extensive laboratory tests and also results from field tests showing the performances of the ester based lubricant for reducing torque and pipe drag when using water based muds. P. 539^

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