document

Abstract

Formate fluids have unique physico-chemical properties that make them the ideal drilling and completion fluids for challenging well construction projects where extraordinary fluid performance is critical for economic success. They have been used in more than 400 wells across the world since their commercial introduction in 1993.

This paper reviews what has been published in the oilfield literature over the past 12 years about well production rates after drilling and/or completing with formate fluids. The conclusions of the review are a) the special properties of formate fluids facilitate the creation of long high-angle wells that improve reservoir access and inflow area; b) the formates tend to minimize formation damage; c) the use of formate fluids generally delivers wells with productivities that exceed expectations.

The published field case histories clearly show that formate fluids can only show their true performance potential when formulated with low levels of solids. When operators have experimented with the addition of weighting solids to formate fluids the drilling performance has been degraded and the well production rates have been unexceptional or below expectations. 

Some of the information disclosed in the literature opens to question whether the use of linear core flooding is an appropriate laboratory test method for predicting the likely impact of formate fluids on well productivity.

Introduction

“Formate fluids” is the collective name given by the oil industry to aqueous solutions of the alkali metals salts of formic acid. The formates are revolutionary in the sense that they can be used to create solids-free or low-solids drilling and completion fluids with densities of up to 19.2 lb/gal (2.3 SG). High-solids drilling fluids containing formates will have inferior performance and should not be described as formate fluids.

Prior to the discovery of formate fluids it had been impossible to formulate solids-free drilling fluids with densities higher than 12.5 ppg (1.5 SG); the traditional high-density brines were just not compatible with the drilling fluid polymers. At least 400 wells have been drilled and/or completed with formate fluids since their introduction in 1993 and they have been the subjects of more than 30 SPE papers.

The remarkable properties 1-4 of the formate fluids are exploited by the oil industry to drill and complete wells that are optimized in terms of:

• Cost/Value

• Operational Time

• Productivity

• Lifetime

• Environmental impact

• Reduced liability and risk

The formates are particularly valued as drilling and completion fluids in challenging operational environments such as:

• High temperature/high pressure (HT/HP)

• Extreme well configurations (ERD,TTD, CTD)

• Sites of ecological sensitivity