Development and Performance of Biodegradable Antiscalants for Oilfield Applications

Abstract

Abstract Biodegradable scale inhibitors have been developed that provide excellent inhibition of barium sulfate scale and that meet regulatory requirements for application in the North Sea and in other sensitive marine environments. These inhibitors are in compliance with the " yellow-banded?? classification issued by the Norwegian sector of the North Sea, meeting ecotoxicity, bioaccumulation, and biodegradation standards. Using turbidity and dynamic tube-blocking protocol, the inhibitors have been shown to provide barium sulfate inhibition comparable to their non-biodegradable equivalents. Introduction Deposition of scale on production equipment impairs the production of oil and gas in reservoirs, down hole, surface and injection operations. Scale inhibitors are often a significant portion of the aqueous based chemical stimulation package used in either the stimulation and/or completion of oil/gas wells. Although highly effective, a number of the chemistries used for these applications-polyacrylates, polyphosphonates, and polysulphonates-have low biodegradability and are unable to meet increasingly strict environmental legislation. A series of improved polymeric scale inhibitors have been developed in accord with the ecotoxicity, bioaccumulation, and biodegradablity standards set by the Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR.. These inhibitors are highly effective for control of a variety of alkaline-earth scales and are suitable for use in scaling environments ranging from mild supersaturation to severe conditions where difficult-to-control barium sulfate scales may form. These products perform comparably to their non-biodegradable equivalents while exceeding the standards required for " yellow-banding?? status in oil production for the Norwegian sector of North Sea. Basic polycarboxylic and sulphonated polycarboxylic acid chemistries were used as the basis of the new scale-inhibiting products. The new inhibitors were developed by examination of their scale inhibiting properties relative to conventional polycarboxylates and-in conjunction with biodegradation testing-were optimized with regard to scale inhibition, biodegradability, and price. Characteristics of the chemistries are shown in Table 1. With the increased biodegradability and excellent scale inhibition performance of these range of chemistries, oil and gas producers can control scale in operations while meeting environmental requirements required in the North Sea and other locations around the world. Experimental Details Regulatory Testing The regulatory requirements for ecotoxicological testing for all chemicals used for offshore drilling in the North Sea are specified in the OSPAR guidelines for the North-East Atlantic. These regulations were implemented in 2001 and are intended to harmonize the mandatory control systems for offshore chemicals. The three categories of tests required by OSPAR are:Acute toxicityBioaccumulationSeawater biodegradation (persistence)