Wells – Processes – Cementing – plugging or consolidating
Reexamination Certificate
1999-06-02
2001-01-09
Suchfeld, George (Department: 3672)
Wells
Processes
Cementing, plugging or consolidating
C106S706000, C106S708000, C106S718000, C106S790000, C166S292000
Reexamination Certificate
active
06170575
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention provides cement compositions and methods of cementing within subterranean formations penetrated by well bores wherein the flow properties of one or more dry particulate cementitious materials used therein are improved and wherein the materials can be readily conveyed out of storage tanks and the like.
2. Description of the Prior Art
Cementitious materials are commonly utilized in subterranean well completion and remedial operations. For example, hydraulic cement compositions are used in primary cementing operations whereby pipes such as casings and liners are cemented in well bores. In performing primary cementing, a hydraulic cement composition is pumped into the annular space between the walls of the well bore and the exterior surfaces of pipe 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 in the well bore and bonds the exterior surfaces of the pipe to the walls of the well bore whereby the undesirable migration of fluids between zones or formations penetrated by the well bore is prevented.
Cementitious materials such as hydraulic cements, slag, fumed silica, fly ash and the like having various particle size distributions are often dry-blended and placed in storage tanks. The storage tanks containing the cementitious materials are also often transported by land or sea to locations where the cementitious materials are to be used. During such transportation, the cementitious materials are subjected to vibrations and as a result, the materials are tightly packed under static conditions. One or more of the cementitious materials are often of ultra-fine particle sizes, i.e., sizes in the range of from about 5 to about 100 microns, which causes the tightly packed problem to be more severe. When the cementitious materials are conveyed out of the storage tanks at the locations of use, significant portions of the tightly packed materials are often left in the storage tanks. The incomplete conveying of the materials results in costs for disposing of the materials and increased costs to the person or entity using the cementitious materials.
Cementitious materials have heretofore been treated to make them more flowable. For example, U.S. Pat. No. 2,857,286 issued to Striker on Oct. 21, 1958 discloses a process of treating Portland cement with acetic acid or a water soluble salt of acetic acid whereby the Portland cement becomes more flowable. In accordance with the Striker patent, the treatment of Portland cement with the acid or acetate is carried out either concurrently with, or subsequent to, the grinding of the cement clinker. The acid or acetate can be combined with the cement during grinding or the ground cement can be treated by injecting the acid or acetate into the cement under pressure as a vapor in order to blow the cement and uniformly contact it with the acid or acetate.
U.S. Pat. No. 3,094,425 issued to Adams et al. on Jun. 18, 1963 discloses that most cements compacted by vibration become semi-rigid and will not flow without considerable mechanical effort to break up the compaction. This condition is known as “pack set.” Further, it is stated that it is known that certain polar molecules when added to ground cement will attach to the cement particles and reduce their surface forces. In accordance with the Adams patent, a mixture of calcium acetate and lignin sulfonate is an effective grinding aid and a pack set inhibitor when added to the cement mill and interground with the cement.
U.S. Pat. No. 3,615,785 issued to Moorer et al. on Feb. 2, 1968 discloses a cement grinding aid and pack set inhibitor comprised of polyol and a water soluble salt of an aliphatic acid having no more than 3 carbon atoms.
The above described additives are difficult to handle and must be added to the cement prior to or after grinding. Since commercially available cementitious materials generally do not include such additives, they must be provided, handled and combined with ground cement by the user by spraying, mechanical mixing or other time consuming procedure.
Thus, there are continuing needs for improving the flow properties of dry particulate cementitious materials used in cement compositions for cementing in subterranean formations penetrated by well bores wherein the materials can be readily conveyed out of storage tanks and the like.
SUMMARY OF THE INVENTION
The present invention provides cement compositions and methods of cementing within subterranean formations penetrated by wells, such as oil and gas wells, wherein the flow properties of one or more dry particulate cementitious materials used therein are improved and wherein the materials can be readily conveyed out of storage tanks and the like. Preferred methods are basically comprised of dry-blending a particulate flow enhancing additive comprised of a particulate solid material carrying a flow inducing polar chemical thereon with the cementitious materials, forming a pumpable slurry using the one or more dry particulate cementitious materials having the particulate flow enhancing additive blended therewith, pumping the slurry into a well bore penetrating the subterranean formation, and then allowing the slurry to solidify within the subterranean formation.
The particulate flow enhancing additive of this invention is easily handled, readily dry blended with cementitious materials and enhances the flow properties of the cementitious materials. The presence of the flow enhancing additive in the cementitious materials allows the cementitious materials to be mechanically or pneumatically conveyed out of storage tanks, even when they are tightly packed therein, without leaving significant portions of the cementitious materials in the storage tanks.
A preferred cement composition useful for well cementing comprises a particulate flow enhancing additive dry-blended with one or more particulate cementitious materials selected from the group consisting of hydraulic cements, slag, fumed silica, fly ash and mixtures thereof. The flow enhancing additive is comprised of a particulate solid material selected from the group consisting of precipitated silica, zeolite, talcum, diatomaceous earth and fuller's earth carrying a flow inducing polar chemical thereon which is selected from the group consisting of polar molecule producing organic acids, their salts and acid anhydrides. The weight ratio of solid adsorbent material to flow inducing chemical in the flow enhancing additive is in the range of from about 90:10 to about 10:90, and the flow enhancing additive is blended with the cementitious materials in an amount in the range of from about 0.01% to about 1.0% by weight of the cementitious materials. The cementitious materials having particulate flow enhancing additive blended therewith are preferably mixed with a sufficient amount of water to form a pumpable slurry.
A particularly preferred particulate flow enhancing additive useful in accordance with this invention is comprised of precipitated silica powder having a flow inducing chemical comprised of glacial acetic acid adsorbed thereon. The weight ratio of precipitated silica powder to the glacial acetic acid in the flow enhancing additive is in the range of from about 90:10 to about 10:90, and the additive is blended with cementitious materials in an amount in the range of from about 0.01% to about 1.0% by weight of the cementitious materials.
It is, therefore, a general object of the present invention to provide improved cement compositions and methods of cementing by enhancing the flow properties of dry particulate cementitious materials used therein.
A further object of the present invention is to enhance the rate of oil and gas well cementing by dry-blending a flow additive of the present invention with one or more dry particulate cementitious materials used in the cementing.
Other and further objects, features and advantages
Crook Ronald J.
Fitzgerald Russell M.
Heathman James F.
Reddy Baireddy R.
Sweatman Ronald E.
Halliburton Energy Service,s Inc.
Roddy Craig W.
Suchfeld George
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