Elastomer compatibility study of oil-based and ester-based drilling fluids

Abstract

Elastomers have been widely used in the industry as a sealer and as part of the important accessories to the drilling equipment especially in the bottom hole assembly. The most critical properties of elastomers are their resistance towards chemical substances such as drilling fluids. Drilling fluids are used during drilling operation to provide many functions such as to cool the drill bit, provide lubrication and to remove the rock chips known as cuttings from the bottom hole to the surface. Different types of drilling fluid based such as water based, oil based and synthetic based are commonly used in the oil and gas fields. Oil based and synthetic based drilling fluids have superior performances over the conventional water based drilling fluids especially when drilling deep well with high pressure and high temperature conditions. Oil based drilling fluids; however, has high aromatic content that leads to pollution and higher toxicity level. In this study, new ester based drilling fluids have been used as an alternative and compared with oil based and synthetic based drilling fluids. Several types of esters derived from palm oil, corn oil and rice bran oil aroused in this study. This study focused on the effect of rubber elastomer towards oil based and ester based drilling fluids at various temperatures and exposure periods. Nitrile butadiene rubber (NBR) were compounded and cut into dumb-bell shape. The weights of elastomers were measured and the tensile strength tests were conducted using ASTM D412 protocol. Temperatures of 25, 80 and 125 °C were chosen and the elastomers were exposed to the drilling fluids for one and two weeks. The results revealed that the diesel and sarapar drilling fluids were compatible with NBR elastomer. As a comparison, tensile strength and the volume of swelling for ester based drilling fluids were significantly changed throughout the tests. However, this swelling effect may be suitable to be used as swell packer during production operation.