Libit Cement - A New Lightweight Cement Slurry For The Cementation Of Deep-Water Surface Strings
Authors: Zuiderwijk J.J.M. 
Published: December 2007

This paper was prepared for the SPE-European Spring Meeting 1974 of the Society of Petroleum Engineers of AIME, held in Amsterdam, the Netherlands, May 29–30, 1974. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.

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The cementation of zones with low fracture gradients, particularly in offshore operations, calls for a lightweight cement, to reduce the risk of formation fracturing.

LIBIT-cement, a newly developed lightweight bitumen cement, combines, a low slurry gradient (565 psi/1000 ft) sufficient mechanical strength of the set cement. These properties render LIBIT cement eminently to the cementation of deep-water topholes.

Introduction

Primary cementation of weak zones with neat Primary cementation of weak zones with neat cement slurries often, leads to losses as a result of the formation break-down pressure being exceeded. In such cases a good cementation job i.e. complete fill of the annular space to the desired height, can be realized only by applying a multi-stage cementation process or by using a lightweight cement slurry. However, multi-stage cementation has the drawback that failures may be experienced with D.V. collars, while moreover the cementing time is almost doubled. Since failures and long cementing times are undesirable, especially in offshore operations, the use of lightweight cement slurries should be preferred.

With commercial Pozmix cements, slurries with gradients of the order of 695 psi/1000 ft can be obtained. For operations at greater water depths it is necessary to go to lower densities, e. g. medium/deep sea operations call for slurry gradients of approx. 570 psi/1000 ft.

Such low slurry gradients can be achieved by incorporating diatomaceous earth or bentonite in the cement formulation. Unfortunately, both filler cements have a very poor mechanical strength and definitely do not meet the 500 psi compressive strength level, which is generally accepted by the industry.

This was the incentive for Koninklijke/Shell Exploratie en Produktie Laboratorium, Rijswijk (the Netherlands) to initiate development work on a lightweight cement capable of reaching a compressive strength of 500 psi in 24 hours at 110 degrees F/1600 psi (API curing schedule 2 S). This has resulted in the development of a lightweight cement slurry, so-called LIBIT cement, which is essentially a mixture of oilwell cement and a bitumen powder. The bituminous component of LIBIT cement has been pretreated in order to promote the compressive strength of the hardened promote the compressive strength of the hardened cement.