Cost-Effective Gas Control: A Case Study of Surfactant Cement

Abstract

Abstract Gas migration during primary cementing has been the subject of numerous studies and is well documented in referenced literature. Methodologies to predict gas flow potential have been devised and various systems have been offered to prevent the phenomenon. However, high cost associated with these systems has made them unattractive for many well candidates having marginal potential for gas flow. This prompts the possibly unsafe choice between merit and economics. With this in mind, a cost effective slurry was developed, incorporating surfactant to prevent annular gas flow. Surfactant cement is a conventional slurry to which a foam generating surfactant is added. Originally developed in 1973 by the Institute Francais du Petrol, surfactant cement has been utilized in several applications worldwide. Surfactant immobilizes formation gas by converting it to a highly viscous low mobility foam. The addition of surfactant also lowers a slurry's surface tension, thereby preventing bubbles from coalescing and becoming mobile. The combination of these two mechanisms combined with thoughtful slurry design will greatly reduce the risk of annular gas flow after cementing. The purpose of this paper is to illustrate, via case study, the cost effectiveness of surfactant cement when used for gas control purposes. A brief overview of annular gas flow causes, conventional aspects of gas control slurry design, and description of surfactant gas control mechanisms are also presented.