Wells – Processes – Cementing – plugging or consolidating
Reexamination Certificate
2002-11-15
2004-03-09
Tsay, Frank (Department: 3672)
Wells
Processes
Cementing, plugging or consolidating
C166S293000, C507S216000
Reexamination Certificate
active
06702021
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to improved drilling fluids and methods of drilling subterranean well bores and sealing pipe strings therein, and more particularly, to such drilling fluids and methods wherein hardenable furan sealant compositions are utilized.
2. Description of the Prior Art
A variety of drilling fluids have been used heretofore in drilling subterranean well bores. The most commonly used drilling fluids are solids-containing water or oil based viscous gels which are often weighted with particulate weighting materials such as barite. The oil based drilling fluids are generally inverted oil-water emulsions containing organophilic clays, weighting materials and other additives. When a well bore is being drilled, the drilling fluid is circulated downwardly through the drill string, through the drill bit and upwardly in the annulus between the walls of the well bore and the drill string. The drilling fluid functions to maintain hydrostatic pressure on subterranean formations penetrated by the well bore and thereby prevent blow-outs and to remove cuttings from the well bore. As the drilling fluid is circulated, a filter cake of solids from the drilling fluid forms on the walls of the well bore. The filter cake build-up is a result of initial fluid loss into the permeable subterranean formations and zones penetrated by the well bore. The filter cake and gelled or partially gelled drilling fluid mixed therewith function to reduce additional fluid loss as the well is drilled.
After the well bore reaches its total depth, the drilling and circulation of drilling fluid are stopped and a string of pipe, e.g., casing, is run into the well bore. After the pipe string is run, the well bore has heretofore been conditioned by circulating drilling fluid downwardly through the pipe string and upwardly through the annulus. The conditioning has been intended to remove filter cake and gelled or partially gelled drilling fluid from the walls of the well bore. Primary cementing operations have then been performed in the well bore. That is, the string of pipe disposed in the well bore has been cemented therein by placing a cement slurry in the annulus and allowing it to set into a hard mass therein. When the cement slurry is run down the pipe and into the annulus, the drilling fluid in the pipe and the annulus is displaced therefrom.
The purpose of cementing the above mentioned string of pipe in the well bore is to provide physical support and positioning to the pipe and seal the annulus. That is, it is intended that the set cement in the annulus will bond to the pipe and to the walls of the well bore whereby the annulus is sealed in a manner which prevents pressurized fluid migration between subterranean zones and formations penetrated by the well bore. However, the sealing of the annulus is often frustrated by filter cake and gelled drilling fluid which remain on the walls of the well bore when primary cementing operations are commenced. That is, when the cement slurry is placed in the annulus and allowed to set therein, thin layers of unconsolidated filter cake solids and gelled drilling fluid often remain between the set cement and the walls of the well bore including the faces of permeable formations or zones containing pressurized fluids. Since the inert layers of unconsolidated solids do not have the physical properties necessary to prevent pressurized fluid migration, such migration takes place by way of flow channels formed through the layers.
While a variety of techniques have heretofore been developed and many attempts to remove filter cake from the walls of well bores and increase the displacement efficiencies of gelled drilling fluids therefrom have been made prior to cementing pipe therein, continuing needs remain for improved drilling fluids, improved methods of drilling and improved methods of sealing pipe in well bores.
SUMMARY OF THE INVENTION
By the present invention, improved drilling fluids and methods of utilizing the drilling fluids for drilling subterranean well bores are provided which meet the needs described above and overcome the shortcomings of the prior art. In addition, the methods of the present invention include the effective sealing of pipe strings in well bores utilizing hardenable furan sealant compositions which are very resistant to chemicals and high temperature environments and provide greatly superior and longer lasting seals between well bores and strings of pipe therein.
The improved drilling fluids of the present invention for use in drilling subterranean well bores are basically comprised of a water base or oil base drilling fluid containing a viscosity increasing material and a hardenable furan sealant composition dispersed therein. When the drilling fluid forms filter cake on the walls of a well bore being drilled, the hardenable furan sealant composition becomes a part of the filter cake and subsequently hardens therein whereby the filter cake is consolidated into a stable solid mass. The consolidation of the filter cake into a solid mass is highly beneficial in that it causes the filter cake to provide greater fluid loss control, to prevent or greatly reduce the occurrence of lost drilling fluid circulation and to prevent or reduce the influx of pressurized formation gas into the well bore during and after a pipe string is sealed therein.
After the well bore is drilled and a string of pipe has been run therein, the string of pipe can be sealed within the well bore by an additional hardenable furan sealant composition that readily bonds to the solidified filter cake and to the string of pipe. Since the hardened furan sealant composition produces a very strong bond to the surfaces of the string of pipe as well as to the solidified walls of the well bore, a greatly superior and longer lasting seal between the well bore and the string of pipe is obtained.
The improved methods of the present invention for drilling a well bore are basically comprised of the following steps. A water or oil based drilling fluid which forms a filter cake on the walls of the well bore as the well bore is drilled is provided which is comprised of a base fluid selected from the group of water or oil, a viscosity increasing material and a hardenable furan sealing composition which becomes a part of the filter cake formed on the walls of the well bore. When the furan sealant composition hardens in the filter cake, the filter cake is consolidated into a stable solid mass. When the well bore being drilled reaches total depth and a string of pipe is run into the well bore, a hardenable furan sealant composition is placed between the pipe and the walls of the well bore and allowed to harden therein.
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
The improved drilling fluids of this invention are basically comprised of water or oil base fluids containing a viscosity increasing material such as bentonite clay or an organophilic clay and a hardenable furan sealant composition dispersed therein. As will be understood by those skilled in the art, the drilling fluid can include other components such as weighting materials and the like.
The hardenable furan sealant composition in the drilling fluid becomes a part of the filter cake formed on the walls of the well bore, and the sealant composition hardens in the filter cake thereby consolidating the filter cake into a stable solid mass. The strength and other properties of the consolidated filter cake are sufficient to prevent or minimize fluid loss from the drilling fluid, lost drilling fluid circulation and the influx of pressurized formation fluids into the well bore during and after a pipe string is sealed therein.
The hardenable furan sealant composition dispersed in the drilling fluid is basically comprised of a curable furan liquid and a silane coupling agent. More preferably the harde
Barton Johnny A.
Isenberg O'Thalla M.
Nguyen Philip D.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Roddy Craig W.
Tsay Frank
LandOfFree
Methods and drilling fluids for drilling well bores and... 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 and drilling fluids for drilling well bores and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods and drilling fluids for drilling well bores and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3216528