Wells – Processes – Cementing – plugging or consolidating
Reexamination Certificate
2000-10-24
2001-04-24
Suchfield, George (Department: 3672)
Wells
Processes
Cementing, plugging or consolidating
C106S677000, C106S678000, C106S711000, C106S820000, C106S823000, C166S309000
Reexamination Certificate
active
06220354
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to cementing subterranean zones penetrated by well bores, and more particularly, to such methods whereby high strength foamed well cement compositions which are crack and shatter resistant are utilized.
2. Description of the Prior Art
Light weight foamed hydraulic cement compositions are commonly utilized in subterranean well completion and remedial operations. For example, foamed hydraulic cement compositions are used in primary cementing operations whereby pipe strings such as casings and liners are cemented in well bores. In performing primary cementing where light weight cement compositions are required to prevent fracturing of subterranean zones, light weight foamed hydraulic cement compositions are pumped into the annular space between the walls of a well bore penetrating the zones and the exterior surfaces of a pipe string disposed therein. The light weight foamed cement composition is permitted to set in the annular space thereby forming an annular sheath of hard substantially impermeable foamed 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.
Multi-lateral wells have recently been developed which include vertical or deviated principal well bores having one or more ancillary laterally extending well bores connected thereto. Drilling and completion equipment is available which allows multiple laterals to be drilled from a principal cased and cemented well bore. Each of the lateral well bores can include a liner cemented therein which is tied into the principal well bore. The lateral well bores can be drilled into predetermined producing formations or zones at any time in the productive life cycle of the well.
In both conventional wells having single well bores and multi-lateral wells having several well bores, the light weight foamed cement compositions utilized for cementing casings or liners in the well bores must have sufficient strength, resiliency, ductility and toughness to resist cracking or shattering as a result of pipe movements, impacts and/or shocks subsequently generated by drilling and other well operations such as perforating. Set foamed cement in wells, and particularly, a set foamed cement sheath in the annulus between a pipe string and the walls of a well bore often fails by cracking or shattering during drilling and/or perforating operations. When the set cement cracks or shatters, rubble is often produced and the seal between the pipe and the walls of the well bore is lost.
Various types of fibers have been utilized in construction cement compositions heretofore. The fibers have been formed of glass, steel, graphite, polyesters, polyamides and polyolefins. Polyolefin fibers have generally been the most preferred in that they are readily available, are low in cost and have high resistance to corrosion and degradation. Fibrillated net-shaped polyolefin fibers have been found to be particularly suitable for use in construction cement compositions because they resist being pulled out of the set cement. The fibers also function to control shrinkage cracking in the early stages of the cement setting process, and after setting, the fibers provide resiliency, ductility and toughness to the cement composition whereby it resists cracking or shattering. When cracking or shattering does occur, the fibers hold the cracked or shattered set cement together and prevent the formation of rubble.
While fibrillated polyolefin net-shaped fibers have been included in well cement compositions heretofore, problems have been encountered because the fibers have been hydrophobic and are difficult to dry blend with cement. Also, the fibers agglomerate in the dry cement when it is conveyed causing plugging to occur, and when the cement and hydrophobic fibers are combined with mixing water, the hydrophobic fibers form mats which prevent their dispersion into and throughout the cement slurry. The lack of dispersion of the fibers in the cement slurry make it difficult to pump and foam.
Thus, there are needs for improved foamed well cement compositions and methods wherein the cement compositions contain fibrillated fibers which can be easily mixed and conveyed with dry cement and subsequently dispersed in the aqueous cement slurry formed prior to pumping and foaming the slurry.
SUMMARY OF THE INVENTION
The present invention provides high strength, resilient, foamed well cement compositions and methods of cementing a subterranean zone using the compositions which meet the needs described above and overcome the deficiencies of the prior art. The compositions of the invention are basically comprised of a hydraulic cement, hydrophilic fibers present in the composition in an amount in the range of from about 0.1% to about 0.25% by weight of the cement in the composition, water present in an amount sufficient to form a pumpable slurry, a mixture of foamed and foam stabilizing surfactants and sufficient gas to foam the slurry.
The improved methods of cementing a subterranean zone penetrated by a well bore of the present invention are basically comprised of the steps of introducing a high strength, resilient, foamed cement composition into the subterranean zone by way of the well bore comprised of a hydraulic cement, hydrophilic fibers, water, a mixture of foaming and foam stabilizing surfactants and a gas. Thereafter, the foamed cement composition is allowed to set in the zone. The compositions and methods of this invention are particularly suitable i-or cementing a pipe string such as casing or a liner in a well bore utilizing a light weight foamed cement composition whereby the set foamed cement can withstand the formation of perforations therein as well as other impacts and shocks subsequently generated by drilling and other well operations without cracking, shattering or forming rubble.
It is, therefore, a general object of the present invention to provide high strength, resilient, foamed well cement compositions and methods of cementing subterranean zones penetrated by well bores using the cement compositions.
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 present invention provides high strength, resilient, foamed well cement compositions and methods of using the compositions for cementing subterranean zones penetrated by well bores. The high strength resilient foamed cement compositions are basically comprised of a hydraulic cement, hydrophilic fibers, water present in an amount sufficient to form a pumpable slurry, a mixture of foaming and foam stabilizing surfactants present in an amount sufficient to form and stabilize the foamed cement composition and sufficient gas to foam the slurry.
Upon setting, a foamed cement composition of this invention has high strength, resiliency, ductility and toughness whereby it resists cracking and/or shattering as a result of impacts or shocks produced in drilling or perforating operations, stresses created by pipe movements and the like. If cracking or shattering does occur, the pieces formed are held together by the hydrophilic fibers in the foamed cement composition.
A variety of hydraulic cements can be utilized in the foamed well cement compositions of this 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 aluminum content cements, silica cements and high alkalinity cements. Portland cements are generally preferred for use in accordance with the present invention. Portland cements of the types defined and described in the
API Specification For
Anderson Clyde R.
Bennett Billy J.
Chatterji Jiten
Cromwell Roger S.
King Bobby J.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Roddy Craig W.
Suchfield George
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