Development and Field Use of Fibre-containing Cement
Authors: van Vliet J.P.M. , van Kleef R.P.A.R. , Smith T.R. , Plompenb A.P. , Shell N.V. Turkse , Kuijvenhovenc C.A.T. , van Quaresma V. , van Raiturkar A. , Schoenmakers J.M. , van Arentzd B. 
Published: October 2008

Abstract
Fibre-containing cement was initially developed as a high-strength material that could be used to line a borehole. During the development work several relatively simple and cheap spin-off applications of fibre cement were identified, such as the use of fibre cement in cement plugs for borehole stabilisation and as a lost circulation material. A number of Shell?s operating companies are already applying fibre cement for these purposes in the field. This paper presents the development of the borehole-lining technique and also describes the other field applications of fibre cement.

1. Introduction
A layer of a high strength material applied to the wall of a borehole can offer a means to seal off problematic hole sections during the drilling of a well. In this way the troubles caused by, for example, unstable formations(such as shales, coal and salts), differential sticking and lost circulation can be remedied. A borehole lining can eliminate the need for setting an intermediate casing string and thereby make it possible to drill longer sections of hole, resulting in a substantial reduction of the costs of drilling and casing a well, The borehole-lining concept is outlined in Fig. 1.
A theoretical analysis of a lined borehole shows that the lining material must have a reasonable tensile strength and must be sufficiently ductile. Ordinary Portland cement, as used in casing cementations, has good compressive strength but relatively poor tensile strength. Extensive laboratory strength tests showed that the right strength characteristics could be elicited from Portland cement if it is reinforced with synthetic fibres. The composite fibre/cement material also exhibited adequate resistance to wear and fragmentation when brought intocontact with a rotating drillstring.
During the development of fibre cement for borehole lining, several relatively simple and cheap spin-off applications of the material were identified. For example, it could be used in plugs for borehole stabilisation and as a lost circulation material. When fibre cement is used asshoe cement, it prevents cement debris from falling onto the bottom-hole assembly (BHA) after the shoe track has been drilled out. This may save the BHA from getting stuck.
This paper presents the development work for the borehole-lining technique, and describes the field uses of fibre cement so far. A batchwise technique for lining a borehole with fibre cement has been field tested. Fibre cement plugs for borehole stabilisation have shown their value in shale and coal sections. And fibre-cement slurries have cured heavy circulation losses encountered during drilling and cementing of casing strings in limestone formations.

2. Development of a borehole lining material
Initial theoretical work on the concept of a borehole liningfocused on the strength characteristics of the liningmaterial required to give the borehole a certain resistance against burst and collapse. Calculations were performed using a model of a 1500-m-deep borehole drilled in cohesion less sand. The burst strength of the lined borehole was derived as a function of the material parameters of the lining material, such as its tensile strength and shear modulus, and a lining thickness parameter.