A New Organic Fluid-Loss-Control Additive for Oilwell Cements

Abstract

A new organic fluid-loss additive for neat and gel cement slurries has been developed for use in squeeze operations to provide controlled dehydration of the slurry and, thus, fewer job failures. In addition, this additive provides greater fill-up behind pipe, even in highly porous formations. This material is compatible with bentonite materials and all portland cements, and it does not retard cement setting times of Class A cements or adversely affect the physical characteristics of the set cement. It acts as a thinner for high-gel cements, facilitating their application. It is effective over a wide range of well conditions and should provide improved control of cementing treatments. It is believed that this additive may permit the adaptation of neat portland slurries and permanent completion techniques to conventional squeeze-cementing operations.

Introduction

During the past 15 years, many advances have been made in oilwell cement formulations and application techniques. Recent cement technology has been directed toward "tailor-made" cement systems that achieve low slurry weight, minimize mud contamination, improve pumpability and provide other properties which help overcome the multitude of problems involved in current cementing operations.

One property of conventional neat portland or retarded cement slurries which has merited considerable study has been filtration control. Particular emphasis has been placed on developing adequate testing equipment and procedures which will simulate temperature and pressure conditions encountered during a well cementing operation. Various additives or admixes, developed to impart low filtration characteristics to cement slurries, have lost favor since development of more rigorous but realistic testing procedures. Good agreement now exists between the many different research organizations, so that the current tests developed by API Committee constitute a realistic yardstick by which newly developed additives can be evaluated properly. Also, cement systems employing these additives can be used in actual field operations with a greater certainty of success than ever before.