Checking Paraffin Deposition By Crystal Growth Inhibition
Authors: Knox John , Waters A.B. , Arnold B.B. 
Published: December 2007

Publication Rights Reserved

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and considered for publication in one of the two SPE magazines with the paper.

Paraffin deposition on producing equipment and in flow lines has plagued the industry since early days. Many procedures have been devised to aid in removal or prevention of this problem, however, most have limitations.

A unique and economical technique for checking paraffin deposition on metal surfaces is presented. Laboratory investigations indicated that certain chemicals changed the manner in which paraffin crystalized from solution.

Field applications substantiating these findings are reposed along with different methods of applying the material. Paraffin deposition has been successfully checked under varying well conditions in several geographic locations.

Introduction

Paraffin has been an enigma of the petroleum industry almost from the day the first well was put on production. Annually, millions of dollars are spent on this problem. Nature and occurrence of paraffin deposits have been studied extensively and literature is available on the subject dating back as far as 1865. Patent literature is rife with products designed to remove and prevent paraffin deposition. Materials described as paraffin inhibitors have been reported.

Reistle's article on paraffin deposition, published in 1932, has become a classic reference in this field and is regarded as one of the most complete and thorough studies ever presented. In spite of this and other subsequent contributions, the problem of paraffin deposition has remained far from a solution.

Nature and Extent of Problem

A paraffin problem has been defined as any predominantly organic deposit which hampers the production of crude. This rather broad definition is required by the complex and variable chemical compositions of field deposits. Studies have revealed that many deposits contain rather large amounts of normal paraffin hydrocarbons and some asphaltic material.

Shock, Sudberry and Crockett reported that paraffin problems are widespread geographically and occur in almost every area where oil is produced. A recent survey of 69 areas in 19 states conducted by the authors showed 59 areas, representing 18 states, reporting paraffin problems. Percentage of incidents might be low in this type survey because many producers say they have no paraffin problem when in reality only a more or less routine procedure has been worked out for keeping the wells on production at a cost that can be tolerated. Other operators have tried so many remedies they do not want to discuss the problem further.

Removal Techniques

Numerous procedures have been devised to aid in the removal of paraffin deposits. In general. these may be classified as (1) methods that remove the paraffin mechanically by the use of scrapers and abrasives, (2) those that involve chemicals such as solvents, surfactants or liquid petroleum gases, and (3) those that use heat such as hot oil treatments and bottom hole heaters. Many hidden costs are involved in most of these procedures such as down time, lost production, wasted oil, and possible damage to producing, equipment. Because of these expenses, the economic life of the well may be shortened.

Recently, considerable effort has been devoted to developing methods of inhibiting paraffin deposition. Most of these utilize changes in surface properties of well equipment while others involve materials characterized as crystal poisons. The latter are thought to poison the surface of paraffin deposits, thus preventing additional deposition.