Controlled Solubility Phosphates--A Versatile Solution To Oilfield Scale Problems

Abstract

Abstract Water flooding has focused attention on the problem of scale in producing wells. Four reasons why scale forms are discussed. A new theory which will help explain the severe scale build-up that occurs in many producing wells at the time of water breakthrough is presented. A recently developed family of scale preventives - the controlled solubility phosphates - are described chemically and physically. Factors which influence the performance of these unique phosphates in oilfield brines are evaluated in terms of laboratory test data. Case histories of producing wells treated with controlled solubility phosphates are summarized. The importance of bottom-hole temperature, the role of produced-fluid mineral characteristics and the value of knowing down-hole flow conditions are pointed out. Economic considerations well known to engineers and production men are used to compare the cost of conventional treatment and the cost of the new controlled solubility phosphate scale-prevention approach. Introduction General acceptance of the artificial water drive as a secondary producing mechanism for the recovery of oil has made many petroleum engineers and production men extremely "water conscious" during the last few years. Scale and corrosion problems of a type seldom encountered in primary production soon become evident as leases are placed under flood. In attempting to find solutions to these newly created problems, the oil industry has learned that standard municipal and industrial water-treatment practice is going to be of little value. The reason for this is that, until the oil industry started to emphasize water flooding and the conditioning of produced fluids, no one had ever attempted to make use of water of as poor quality as that now being handled by many secondary-recovery operators. The need for processing brines saturated with corrosive gases, scale-forming minerals and insidious microbiological growths has opened up a completely new field of water-conditioning technology. This paper deals with scale in oilfield brines. Factors which influence the formation of scale are discussed along with how petroleum engineers can get the most out of a unique family of chemicals which will effectively prevent scale.