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This paper is to be presented at the Mechanical Engineering Aspects of Drilling Production Symposium in Fort Worth, Tex., on March 23–24, 1964, and is considered the property of Society of Petroleum Engineers. Permission to publish is hereby restricted to an abstract of not more than 300 words, with no illustrations, unless the paper is specifically released to the press by the Editor of the Journal of Petroleum Engineers or the Executive Secretary. Such abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in JOURNAL OF PETROLEUM TECHNOLOGY or SOCIETY OF PETROLEUM ENGINEERS JOURNAL is granted on request, providing proper credit is given that publication and the original presentation of the paper.

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, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract

Lost circulation problems during cementing operations can be reduced or eliminated if the hydrostatic pressure during the cementing operation is no greater than it is during the drilling operation. This pressure balance can be achieved in practice by use of a new cementing process. The LVO Cementing Process involves the placing of a slug of regular drilling mud lightened with nitrogen ahead of the cement slurry. The buoyancy effect of this "fluffy" mud is greater than the added weight of the cement slurry compared to normal drilling mud. Approximately 200 jobs have been done. Results are 95 per cent successful. The procedure is now standard in northwestern Oklahoma.

Introduction

The desirability of obtaining good primary cement jobs is unquestioned. In the past, this has often been impossible when trying to set and cement casing through zones of known "lost circulation". Cementing problems can be reduced or eliminated if the hydrostatic pressure during the cementing operation is no greater than it is during the drilling operation. This pressure balance can be achieved in practice by nitrifying a portion of the mud column above the cement slurry. Attempts have been made over the past several years to reduce the weight of the cement column by reducing the density of the cement slurry. However, any cement slurry is still considerably heavier than the drilling mud normally used and although-the problem may be relieved somewhat by a "tailored" cement slurry, a simpler and less expensive solution is now available.

THE BASIC PRINCIPLE

The basic principle in the LVO Cementing Process [LVO is Livingston's stock symbol] is that the combined weight of the cement column, preceded by a slug of "fluffy" mud [nitrified] and the un-nitrified mud cap is equal to or less than the hydrostatic pressure of the drilling mud used during drilling operations. Attached for the use of the field engineer is a nomenclature chart and a simplified calculation sheet used in northwestern Oklahoma, West Texas and the Gulf Coast. The field hookup is simple and can be made by the cementing service company and nitrogen supplier on short notice.

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