Well cementing method using HMHPG filtrate reducer

Details Well cementing method using HMHPG filtrate reducer Well cementing method using HMHPG filtrate reducer

1998-03-31

2001-07-10

Bagnell, David (Department: 3673)

Wells

Processes

Cementing, plugging or consolidating

C166S283000, C106S823000, C106S730000

Reexamination Certificate

active

06257336

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates in particular to operations conducted as a means of exploiting subsoil deposits containing hydrocarbons. More specifically, the invention describes a method of controlling fluid loss by filtration in a geological formation when cementing a well with clinker.
BACKGROUND OF THE INVENTION
When a clinker cement is placed in contact with a porous geological formation, an aqueous element of the clinker tends to penetrate the pores of the formation. This is generally referred to as filtration. This quantity which is lost from the clinker compound is referred to as filtration loss or filtrate. It is desirable to limit this loss, particularly of water, from a clinker, since any such loss will alter its physical-chemical properties, for example its rheological properties. The characteristic which allows it to be pumped may be seriously affected or its setting capacity might be altered due to a decrease in the amount of water needed to bring about the various chemical reactions causing it to set and these factors are clearly detrimental to the cementing operation in the well as well as to the mechanical properties of the cement once it has set. This filtration through a porous formation also incurs the risk of destabilising the walls of the well or clogging geological production or potential production zones. Additives specific to clinker cements which act as filtrate reducers, are therefore incorporated with the clinker cements as a means of restricting filtration, for example by reducing the filtration speed, especially by reducing the permeability of the cake formed on the well walls.
Clearly, these filtrate reducer products used with clinker cement will depend on the composition of the clinker in terms of how high the solid content is and in view of the fact that the clinker by definition undergoes a physical-chemical change along the formation during the setting process. In addition, it is desirable that the cake formed due to filtration will do virtually nothing to damage the mechanical bond of the cement with the wall of the well.
Numerous filtrate reducer products for clinker cements are known in the profession. Finely divided mineral particles may be used, for example, or water-soluble polymers such as the sulphonated derivatives of polyacrylamide or HEC (hydroxyethyl cellulose). However, the polymers used in the profession are very sensitive to the high temperatures which can be encountered at subsoil level, and thus lose their initial properties.
SUMMARY OF THE INVENTION
The present invention therefore relates to a method implemented in a bore drilled through at least one geological formation of a certain permeability, whereby a clinker cement is moved through said well. During the method, filtration through the walls of said well is limited as the clinker is being cemented by adding a given quantity of at least one derivative of a hydrophilically and hydrophobically modified galactomannan.
In one embodiment, the derivative is hydrophobically modified hydroxy propylated guar.
The hydrophilically modified galactomannan may be hydrophobically modified by fixing, on the oxygens, radicals having the general formula (1):
where
A=a linear or branched oxyalkylenic O—C
p
H
2p
group where p is 2 to 4, n=0 to 30; m=0 or 1 where m may not be zero unless n is zero,
R=a linear or branched (hydrophobic) alkyl radical, which may or may not be ethylenically saturated, having between 10 and 32 carbon atoms, preferably between 12 and 30 and more particularly between 18 and 28.
The molecular mass of the modified galactomannan may be less than 2000000 dalton and preferably within the range of between 50000 and 1600000 dalton.
The clinker may include other polymers of the polysaccharide type or synthetic polymer selected from the group comprising scleroglucan, derivatives of the hydroxy ethylated cellulose type (HEC), CMC, Guar gum and the derivatives of polyacrylamide.
The invention also relates to a clinker cement to be applied in a well bored through at least one geological formation of a certain permeability, the clinker containing a given quantity of at least one derivative of a hydrophilically and hydrophobically modified galactomannan.
The filtrate of this clinker may be controlled by adding a given quantity of at least one derivative of hydrophilically and hydrophobically modified glactomannan.
In one embodiment, the derivative may be hydrophobically modified hydroxy propylated guar.
The viscosity of the clinker may be essentially controlled by adding at least one polymer selected from the group comprising xanthane, scleroglucan, wellane, hydroxy ethylated cellulose (HEC), CMC, gum of guar and the polyacrylamides or their derivatives.
The invention also relates to a filtrate reducing additive for clinker cement, the additive containing a given quantity of at least one derivative of hydrophilically and hydrophobically modified galactomannan.
Galactomannans are polysaccharides essentially consisting of galactose and mannose units. They are produced from the endosperm of leguminous seeds such as guar, carob and suchlike.
In particular, guar gum is a natural polymer made up of monomeric units of D-mannose linked to one another by 1-4 bonds forming the main chain on which units of D-galactose are branched by 1-6 bonds. This derivative is functionalised to render it hydrophilic by reaction with an alkylene oxide of 2 to 4 carbon atoms or by reaction in the presence of monochloroacetic acid. The hydrophilic substituents are selected from the group comprising hydroxethyl, hydroxypropyl, hydroxybutyl, carboxymethyl. This derivative is functionalised to render it hydrophobic by reaction with an epoxyalkane and/or alkene, or alkyl and/or alkenyl glycidyl ether in a basic medium, by means of the method described in document U.S. Pat. No. 4,960,876, for example, whereby from 0.001 t 2% of functions (1) can be grafted.
The products obtained thereby (HM guar) can be used as they are or purified by a process of extraction in organic solvents or in a mixture of water and organic solvent in order to remove certain impurities.
Water-soluble HM guar can be prepared from a derivative of guar gum by chemically incorporating a long chain corresponding to the radical given in formula (1).
The hydrophobic functions are grafted onto the hydrophilic chain by functions of the type
where A=a linear or branched oxyalkylenic O—C
p
H
2p
group where p is 2 to 4, n=0 to 30; m=0 or 1 where m may not be zero unless n is zero,
These functions of the “spacer” type enable the hydrophobic groups to be separated from the main chain.
The number of hydrophobic units varies from 0.00001 to approximately 0.02 substituents per unit of anhydroglucoside, preferably between 0.00005 and 0.01 and is more especially efficient between 0.0001 and 0.001 substituents per unit of anhydroglucoside.
The HM guar polymer may have a molar substitution rate per hydrophilic unit of 0.7 and preferably between 0.7 and 4, the molar ratio between the hydrophilic and hydrophobic substituents being within the range between 35/1 and 400000/1. The hydrophilic unit may be of the hydroxyethyl, hydroxypropyl, hydroxybutyl type or a carboxylated substituent. The hydrophobic unit may be of the alkyl, linear or branched alkylenyl type having from 10 to 32 carbon atoms. The hydrophobically modified hydroxy propylated guar is referred to here as HMHPG.
The efficiency of the polymers used for the purposes of the present invention exhibit at least an improvement as a means of controlling filtration as compared with the known synthetic acrylic polymers in particular. In addition, however, the polymers of the invention are natural products and have the specific advantage of being bio-degradable and compatible with the relatively stringent laws governing environmental protection. Compared with the other natural polymers conventionally used, the polymers of the invention exhibit a good capacity to control the filtration of clinker cements.
The applicant has demonstrate

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