Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
1999-09-07
2001-04-03
Green, Anthony (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S678000, C106S681000, C106S682000, C106S802000, C106S803000, C106S806000, C106S823000, C166S293000
Reexamination Certificate
active
06210476
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improved foamed cement compositions and methods of using the compositions for cementing wells.
2. Description of the Prior Art
Foamed hydraulic cement compositions are utilized in various applications including in surface construction and in subterranean well completion and remedial operations. For example, foamed cement compositions are used in primary well cementing operations whereby strings of pipe such as casings and liners are cemented in well bores. In performing primary cementing, a cement composition is pumped into the annular space between the walls of a well bore and the exterior surfaces of a pipe string disposed therein. The cement composition is permitted to set in the annular space thereby forming an annular sheath of hardened substantially impermeable cement therein. The cement sheath physically supports and positions the pipe string in the well bore and bonds the exterior surfaces of the pipe string to the walls of the well bore whereby the undesirable migration of fluids between zones or formations penetrated by the well bore is prevented.
In surface construction applications, the cement compositions utilized must often be lightweight. In well applications, the cement compositions must also often be lightweight to prevent excessive hydrostatic pressure from being exerted on subterranean formations penetrated by the well bore whereby the formations are unintentionally fractured. In addition to being lightweight, a foamed cement composition contains compressed gas which improves the ability of the composition to maintain pressure and prevent the flow of formation fluids into and through the cement composition during its transition time, i.e., the time during which the cement composition changes from a true fluid to a hard set mass. Foamed cement compositions are also advantageous because they have low fluid loss properties.
The cement compositions utilized for cementing pipe strings in well bores must develop high strength after setting and also should have sufficient resiliency, i.e., elasticity and ductility, to resist the loss of the cement bond between the pipe and formation. That is, the set cement composition in the annulus between a pipe string and the walls of a well bore often fail due to pipe movements which cause shear and/or compressional stresses to be exerted on the set cement. Such stress conditions are commonly the result of relatively high fluid pressures and/or temperatures inside the cemented pipe string during testing, perforating, fluid injection or fluid production. The high internal pipe pressure and/or temperature results in the expansion of the pipe string both radially and longitudinally, which places stresses on the cement sheath causing it to crack or causing the bonds between the cement composition and the exterior surfaces of the pipe or formation, or both, to fail which allows leakage of formation fluids into or through the well bore.
Stress conditions also result from high pressures which occur inside the cement sheath due to the thermal expansion of fluids trapped within the cement sheath. This condition often occurs as a result of high temperature differentials created during the injection or production of high temperature fluids through the well bore, e.g., wells subjected to steam recovery or the production of hot formation fluids from high temperature formations. Typically, the pressure of the trapped fluids exceeds the collapse pressure of the cement and pipe causing leaks and bond failure. Other compressional stress conditions occur as a result of outside forces exerted on the cement sheath due to formation shifting, overburden pressures, subsidence and/or tectonic creep.
Thus, there are needs for improved cement compositions and methods of utilizing the compositions in wells whereby after setting, the cement compositions form resilient solid masses which have high compressive, tensile and bond strengths sufficient to withstand the above described stresses without failure.
SUMMARY OF THE INVENTION
The present invention provides foamed cement compositions having improved properties upon setting including enhanced resiliency as well as enhanced compressive, tensile and bond strengths. The improved foamed cement compositions of this invention are basically comprised of a hydraulic cement, amorphous silica which has been surface treated with a mixture of organosilane coupling agents, sufficient water to form a slurry, sufficient gas to foam the slurry and a mixture of foaming and foam stabilizing surfactants present in an amount sufficient to facilitate the formation of the foam and stabilize the foamed composition. The organosilane coupling agent mixture used to surface treat the amorphous silica is preferably a mixture of 3-glycidoxypropyltrimethoxy silane and 3-aminopropyltriethoxy silane or a mixture of 3-glycidoxypropyltrimethoxy silane and N-2-(aminoethyl)-3-aminopropyltrimethoxy silane. A 1:1 by weight mixture of 3-glycidoxypropyltrimethoxy silane and 3-aminopropyltriethoxy silane is most preferred.
The improved methods of this invention for cementing in a subterranean zone penetrated by a well bore are comprised of the following steps. A foamed cement composition of the invention is prepared which hardens into a resilient solid mass having high compressive, tensile and bond strengths. The cement composition is placed in the subterranean zone and then allowed to set into a hard solid mass therein.
It is, therefore, a general object of the present invention to provide improved foamed cement compositions and methods.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows.
DESCRIPTION OF PREFERRED EMBODIMENTS
The improved foamed cement compositions of this invention are useful in surface construction applications and are particularly suitable for performing a variety of completion and remedial procedures in subterranean zones or formations penetrated by well bores. The foamed cement compositions have improved properties upon setting, e.g., the compositions have enhanced resiliency and high compressive, tensile and bond strengths.
The foamed cement compositions of this invention are basically comprised of hydraulic cement, amorphous silica which has been surface treated with a mixture of an epoxy organosilane coupling agent and an amine organosilane coupling agent, sufficient water to form a slurry, sufficient gas to foam the slurry, and mixture of a foaming and foam stabilizing surfactants sufficient to facilitate the formation of the foam and stabilize the foamed composition.
A variety of hydraulic cements can be utilized in accordance with the present invention including those comprised of calcium, aluminum, silicon, oxygen and/or sulfur which set and harden by reaction with water. Such hydraulic cements include Portland cements, pozzolana cements, gypsum cements, high alumina content cements, silica cements and high alkalinity cements. Portland cements or their equivalents are generally preferred for use in accordance with the present invention when performing cementing operations in subterranean zones penetrated by well bores. Portland cements of the types defined and described in
API Specification For Materials And Testing For Well Cements
, API Specification 10, 5
th
Edition, dated Jul. 1, 1990 of the American Petroleum Institute are particularly suitable. Preferred API Portland cements include classes A, B, C, G and H, with API classes G and H being more preferred and class G being the most preferred.
The surface of the amorphous silica useful in accordance with the present invention is pretreated with a mixture of epoxy and amine organosilane coupling agents as will be described below. Various forms of synthetic and natural amorphous silicas can be utilized including, but not limited to, fly ash, fumed silica, rice hull ash, natural pozzolana and the like. Of these, fumed silica is
Anderson Clyde R.
Chatterji Jiten
Cromwell Roger S.
McMechan David E.
Reddy Baireddy R.
Dougherty, Jr. C. Clark
Green Anthony
Halliburton Energy Service,s Inc.
Roddy Craig W.
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