Wells – Processes – Cementing – plugging or consolidating
Reexamination Certificate
2002-12-16
2003-12-30
Marcantoni, Paul (Department: 1755)
Wells
Processes
Cementing, plugging or consolidating
C166S293000
Reexamination Certificate
active
06668929
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 subterranean formations 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 not 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 Typically, after a well bore is drilled to total depth, the drill pipe and drill bit are withdrawn from the well bore and the drilling fluid is left in the well bore to provide hydrostatic pressure on permeable formations penetrated by the well bore thereby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 during the cementing process.
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. Also, slag-containing settable spotting fluids are intolerant to cement 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 will avoid well cementing problems of the types described above at subterranean temperatures above 90° F.
SUMMARY OF THE INVENTION
By the present invention, methods of using oil-based settable spotting fluids in well cementing and oil-based settable spotting fluid compositions are provided which meet the above described needs and overcome the deficiencies of the prior art. The methods of cementing a pipe string in a well bore containing oil-base drilling fluids basically comprise the following steps. An oil-based settable spotting fluid is prepared comprising an oil external emulsion which comprises oil, water and an emulsifying surfactant; a hydraulically settable component; and a de-emulsifying surfactant for de-emulsifying the oil-external emulsion when the emulsion is cured. The settable oil-based spotting fluid composition is pumped into the annulus between the pipe string and the walls of the well bore to displace at least a portion of the oil-based drilling fluid out of the annulus. A cement composition is pumped into the annulus whereby the oil-based drilling fluid and the settable spotting fluid are displaced except for portions of the settable spotting fluid which remain in fractures or other permeable zones therein. Thereafter, the cement composition in the annulus and any settable spotting fluid composition remaining in the fractures or other permeable zones therein are allowed to set into hard impermeable masses.
The oil-based settable spotting fluid compositions of this invention for use in cementing wells and subterranean formations basically comprise the following components: an oil external emulsion comprising oil, water and an emulsifying surfactant; a hydraulically settable component; and a de-emulsifying surfactant for de-emulsifying the oil-external emulsion when the emulsion is cured.
The 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
Preferred methods of this invention for cementing well bores or subterranean formations containing oil-base fluids basically comprise the following steps. An oil-based settable spotting fluid is prepared comprising an oil external emulsion which comprises oil, water and an emulsifying surfactant; a hydraulically settable component; and a de-emulsifying surfactant for de-emulsifying the oil-external emulsion when the emulsion is cured. The settable oil-based spotting fluid composition is pumped into the annulus between the pipe string and the walls of the well bore to displace at least a portion of the oil-based drilling fluid out of the annulus. A cement composition is pumped into the annulus whereby the oil-based drilling fluid and the settable spotting fluid are displaced except for portions of the settable spotting fluid which remain in fractures or other permeable zones therein. Thereafter, the cement composition in the annulus and any settable spotting fluid composition remaining in the fractures or other permeable zones therein are allowed to s
Chatterji Jiten
Dennis, Jr. John L.
Griffith James E.
King Bobby J.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Marcantoni Paul
Roddy Craig W.
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