Wells – Processes – Cementing – plugging or consolidating
Reexamination Certificate
2000-09-29
2002-07-16
Suchfield, George (Department: 3672)
Wells
Processes
Cementing, plugging or consolidating
C106S677000, C106S678000, C106S727000, C106S808000, C106S823000, C166S309000, C507S244000, C507S905000, C524S002000
Reexamination Certificate
active
06419016
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improved methods of cementing in subterranean zones with set retarded foamed and non-foamed cement compositions.
2. Description of the Prior Art
Hydraulic cement compositions are often utilized in cementing subterranean zones penetrated by well bores. For example, such cement compositions are used in primary well cementing operations whereby strings of pipe such as casing 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.
The hydraulic cement compositions utilized for cementing in subterranean zones penetrated by well bores can have densities ranging from high densities, e.g., 28 pounds per gallon to low densities, e.g., 7 pounds per gallon depending upon the fracture gradients of the formations penetrated by the well bores in which the cement compositions are to be placed. In some wells penetrating easily fractured zones or formations, lightweight cement compositions are required to prevent excessive hydrostatic pressure from unintentionally fracturing the zones or formations. In such applications, foamed cement compositions are often utilized having densities in the range of from about 7 to about 13 pounds per gallon. In other applications where the unintentional fracturing of subterranean zones or formations penetrated by the well bores is not a concern, non-foamed cement compositions are utilized having densities in the range of from about 14 to about 28 pounds per gallon.
When foamed or non-foamed cement compositions are utilized for cementing in deep hot subterranean zones, a set retarder must be included in the cement compositions to increase the pumping time of the compositions and prevent premature thickening or setting before placement in the zones to be cemented. Examples of set retarders which have been utilized in non-foamed cement compositions include, but not limited to, lignosulfonates, sulfomethylated lignosulfonates, hydroxycarboxy acids, borates, gluconates, mixtures of sulfomethylated lignosulfonates and hydroxycarboxy acids, carboxymethylcelluloses, acrylic acid/2-acrylamido-2-methyl propane sulfonic acid copolymers and the like. These and other similar set retarders are generally anionic. As a result of being anionic, the set retarders function as dispersing agents in hydraulic cement compositions. When large quantities of such retarders are used to retard the compositions at high temperatures, the cement compositions become so thin that severe settling becomes a major concern. As a result, additional chemical additives have to be added to prevent settling.
The dispersing action of anionic set retarders poses a different problem when used in foamed hydraulic cement compositions. Because of the dispersing action of the set retarders, the foamed cement slurry is thinned which causes the foam to break or significantly decrease in viscosity which in turn prevents the desired low density of the foamed cement composition from being achieved. In order to overcome this problem, it has heretofore been necessary to utilize large excesses of foaming and foam stabilizing surfactants in set retarded foamed cement slurries.
Thus, there are needs for improved methods of cementing in subterranean zones penetrated by well bores using cement compositions which include biodegradable, substantially non-dispersing set retarders.
SUMMARY OF THE INVENTION
The present invention provides improved methods of cementing in subterranean zones penetrated by well bores utilizing foamed or non-foamed cement compositions containing a biodegradable, substantially non-dispersing set retarder comprised of polysuccinimide which meet the needs described above and overcome the deficiencies of the prior art. That is, because of its low anionic character, the polysuccinimide set retarder does not significantly disperse the cement compositions and under the alkaline conditions of the cement compositions, breaks down into completely biodegradable components. The improved methods of this invention utilizing a non-foamed cement composition are basically comprised of the following steps. A cement composition is prepared comprised of hydraulic cement, a biodegradable, substantially non-dispersing set retarder of low anionic character comprised of polysuccinimide and sufficient water to form a slurry. The cement composition is then placed into a subterranean zone and allowed to set into a solid mass therein.
The methods of the present invention utilizing a foamed cement composition are the same as described above for non-foamed cement compositions except that the prepared cement composition is comprised of a hydraulic cement, a biodegradable, substantially non-dispersing set retarder of low anionic character comprised of polysuccinimide, sufficient water to form a slurry, a mixture of foaming and foam stabilizing surfactants present in an amount sufficient to foam and stabilize a foamed cement composition and sufficient gas to form a foam.
It is, therefore, a general object of the present invention to provide improved methods of cementing in subterranean zones penetrated by well bores.
A further object of the present invention is the provision of improved methods of cementing in subterranean zones penetrated by well bores utilizing a foamed or non-foamed cement composition containing a biodegradable, substantially non-dispersing set retarder.
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 methods and cement compositions of the present invention are particularly suitable for performing a variety of completion and remedial procedures in subterranean zones or formations penetrated by well bores. The cement compositions have improved properties in that they include a biodegradable, substantially non-dispersing set retarder of low anionic character which is effective over a broad temperature range and does not cause thinning of non-foamed cement slurries or decreases in the viscosities of foamed cement compositions whereby their densities increase. Since it is often very important that the density of a foamed cement composition be as low as possible, an increase in density can cause adverse cementing results and fracturing of the formation or zone being cemented.
The non-foamed cement compositions useful in accordance with this invention are basically comprised of a hydraulic cement; a biodegradable, substantially non-dispersing set retarder of low anionic character comprised of polysuccinimide; and sufficient water to form a slurry.
The foamed cement compositions useful in accordance with this invention are basically comprised of a hydraulic cement; a biodegradable, substantially non-dispersing set retarder of low anionic character comprised of polysuccinimide; sufficient water to form a slurry; a mixture of foaming and foam stabilizing surfactants present in an amount sufficient to foam and stabilize a foamed cement composition; and sufficient gas to form a foam.
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. Po
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Roddy Craig W.
Suchfield George
LandOfFree
Methods of cementing in subterranean zones does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods of cementing in subterranean zones, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods of cementing in subterranean zones will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2882632