Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2001-09-18
2003-02-25
Marcantoni, Paul (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S708000, C106S710000, C106S792000, C106S794000, C166S293000, C507S928000
Reexamination Certificate
active
06524384
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to oil-based settable spotting fluid compositions for use in cementing wells and methods of using the compositions.
2. Description of the Prior Art
Hydraulic cement compositions are commonly utilized in the construction of oil and gas wells. For example, hydraulic cement compositions are used in primary cementing operations whereby strings of pipe 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 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.
A variety of drilling fluids are used in drilling wells. Oil-based drilling fluids are commonly used in applications where the permeabilities of producing formations would be damaged if the formations were contacted by water-based drilling fluids. However, it has heretofore been common place in the industry to use water-based settable spotting fluids which are incompatible with the oil-based drilling fluids and often cause well bore stability problems and damage to the permeability of producing formations.
During the drilling of a well bore, the drilling fluid used is circulated through the drill pipe and drill bit and then upwardly through the well bore to the surface. The drilling fluid functions to lubricate the drill bit and carry cuttings to the surface where the cuttings and gas are removed from the drilling fluid. While drilling fluids are not settable, i.e., they do not set into hard impermeable sealing masses when static, drilling fluids increase in gel strength over time. Typically, after a well bore is drilled to total depth, the drill pipe and drill bit are withdrawn from the well bore and the drilling fluid is left in the well bore to provide hydrostatic pressure on permeable formations penetrated by the well bore thereby preventing the flow of formation fluids into the well bore.
The next operation in completing the well bore usually involves running a pipe string, e.g., casing, into the well bore. Depending upon the depth of the well bore and whether or not problems are encountered in running the pipe string therein, the drilling fluid may remain relatively static in the well bore for a time period up to 2 weeks. During that time, the stagnate drilling fluid progressively increases in gel strength whereby portions of the drilling fluid in the well bore become increasingly difficult to displace.
After the pipe string has been run in the well bore, the next operation performed is usually primary cementing. That is, the pipe string disposed in the well bore is cemented by pumping a cement composition through the pipe string and into the annulus between the pipe string and the walls of the well bore whereby the drilling fluid in the annulus is displaced therefrom by the cement composition. While a variety of techniques have been developed for improving the displacement of the drilling fluid from the annulus, if the drilling fluid has developed gel strength due to remaining static in the well bore for a long period of time, portions of the drilling fluid in the well bore are bypassed by the cement composition. Since the drilling fluid is not settable, i.e., it does not set into a rigid mass, formation fluids enter and flow in the well bore which is highly undesirable.
Heretofore, settable spotting fluid compositions have been developed and used in wells for various purposes including the early displacement of drilling fluids from well bores. However, as mentioned, the settable spotting fluids have been water based and have included blast furnace slag and other hydraulic components which slowly set at relatively low temperatures, i.e., temperatures less than about 90° F. Also, slag-containing settable spotting fluids are intolerant to cement composition contamination, i.e., if well cement mixes with such spotting fluids, the spotting fluids prematurely set. To prevent a slag-containing spotting fluid from prematurely setting, a very strong set retarder must be added to the spotting fluid and the spotting fluid must be separated from the cement composition by a spacer fluid. If intermixing between the cement composition and the set retarded spotting fluid occurs, the cement composition may be prevented from setting by the strong set retarder in the spotting fluid.
Thus, there are needs for oil-based settable spotting fluid compositions which can be utilized in wells drilled with oil-based drilling fluids and avoid well cementing problems of the types described above at subterranean temperatures above 90° F.
SUMMARY OF THE INVENTION
By the present invention, oil-based settable spotting fluid compositions and methods of using the compositions in well cementing at temperatures up to about 200° F. are provided which meet the above described needs and overcome the deficiencies of the prior art. The oil-based settable spotting fluid compositions of this invention are basically comprised of oil, an emulsifying surfactant for emulsifying the oil with water whereby an oil-external emulsion is formed, a de-emulsifying surfactant which in time de-emulsifies the oil-external emulsion when the emulsion is contacted with external water, a hydraulic settable component selected from the group consisting of ASTM Class C or the equivalent fly ash and ASTM Class F or the equivalent fly ash together with a source of calcium, and water selected from the group consisting of fresh water and salt water present in an amount sufficient to form a slurry having a density in the range of from about 12 to about 15 pounds per gallon.
The oil-based settable spotting fluid compositions of this invention are compatible with oil-based drilling fluids. The oil-based spotting fluids are also tolerant to well cement contamination and as a result, the use of set retarders is not required. Further, when displacing an oil-based settable spotting fluid composition of this invention with a well cement composition, a spacer between the spotting fluid and the well cement composition does not have to be utilized, and there is no need to utilize a spacer for improving the spotting fluid displacement since any bypassed spotting fluid will set with time.
The methods of this invention for cementing a pipe string such as casing in a well bore containing oil-based drilling fluid with a cement composition are basically comprised of the steps of preparing an oil-based settable spotting fluid composition of this invention, pumping the settable spotting fluid composition into the well bore to displace at least a portion of the oil-based drilling fluid from the well bore thereby preventing the drilling fluid from remaining in at least a portion of the well bore and progressively increasing in gel strength over time therein, running the pipe string to be cemented into the well bore whereby the pipe string and well bore are at least partially filled with the oil-based settable spotting fluid, pumping and displacing the cement composition through the pipe string and into the annulus between the pipe string and the walls of the well bore whereby the oil-based drilling fluid and the oil-based settable spotting fluid composition in the pipe string and in the annulus are displaced therefrom except for portions of the oil-based settable spotting fluid composition which may remain in fractures or other non-displaced areas in the well bore, and allowing the cementing composition in the annulus and any settable spotting fluid composition remaining in the fractures or other non-displaced areas to set into a hard impermeable mass therein.
It is, therefo
Chatterji Jiten
Cox Ricky A.
Dennis, Jr. John L.
Griffith James E.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Marcantoni Paul
Roddy Craig W.
LandOfFree
Oil-based settable spotting fluid does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Oil-based settable spotting fluid, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Oil-based settable spotting fluid will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3135720