Wells – Processes – Cementing – plugging or consolidating
Reexamination Certificate
2001-02-21
2001-11-27
Suchfield, George (Department: 3672)
Wells
Processes
Cementing, plugging or consolidating
C166S295000, C166S300000, C166S902000, C405S129350, C405S266000
Reexamination Certificate
active
06321841
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to improved methods of sealing pipe strings in well bores penetrating subterranean corrosive fluid disposal zones.
2. Description of the Prior Art
Hydraulic cement compositions are commonly utilized as sealants in well completion operations whereby strings of pipe such as casing and liners are sealed in well bores. In performing such operations, 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 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.
Corrosive waste fluids such as salt water, acidic materials, caustic materials, organic materials, chemical byproduct materials and the like are often disposed of by injecting them into disposal wells. Such disposal wells penetrate subterranean formations which accept large volumes of waste fluids and are naturally separated from other subterranean formations. When a disposal well is completed whereby a string of steel pipe is cemented in the well bore utilizing a hydraulic cement composition, both the set cement and steel pipe are often subjected to severe corrosion. A result of such corrosion in disposal wells can be that the waste fluids leak into and contaminate formations containing useful fluids such as hydrocarbons or potable water.
In order to prevent the corrosion of metal pipe strings in disposal wells, it has heretofore been the practice to seal the pipe strings in the well bores with hardenable epoxy resin sealing compositions. The epoxy resin sealing compositions utilized have been highly resistant to degradation by acids and other corrosive fluids which reduces the corrosion of metal pipe strings and the chances that corrosive fluids will find their way to the surface or into other subterranean locations. However, the hardened epoxy resin sealing compositions have often lacked sufficient resiliency as well as the necessary bond strength to resist loss of pipe and/or formation bond and cracking or shattering as a result of pipe movements caused by expansion, contraction, impacts or shocks. In addition, the epoxy resin sealing compositions utilized heretofore have been intolerant to contact with water. That is, the epoxy resin sealing compositions have contained epoxy resins which are incompatible with water whereby when the compositions are contacted with water, premature hardening of the compositions or other adverse conditions result. Consequently, the epoxy resin sealing compositions have heretofore required the use of oil based pre-flushes and displacement fluids to prevent contact of the compositions with water. The use of such preflushes and displacement fluids is costly and time consuming. Also, even when oil based pre-flushes and displacement fluids are used, water contact with the epoxy resin sealing compositions often takes place causing problems or failures in the sealing operations.
Thus, there are needs for improved methods of sealing pipe strings in disposal wells whereby corrosion resistant, hardenable epoxy sealing compositions are utilized which are compatible with water and also have the resiliencies and high bond strengths required to withstand pipe movements without failure.
SUMMARY OF THE INVENTION
The present invention provides improved methods of sealing a pipe string in the well bore of a disposal well that penetrates a subterranean corrosive fluid disposal zone which meet the needs described above and overcome the deficiencies of the prior art. A method of the invention is basically comprised of the following steps. A pumpable, water compatible, corrosion resistant, hardenable epoxy sealing composition is prepared which can be displaced by or otherwise contacted with water or a water containing fluid without the occurrence of premature hardening or other adverse result comprised of a hardenable epoxide containing liquid and a hardening agent for the epoxide containing liquid. Thereafter, the epoxy sealing composition is placed in the annulus between a pipe string and the walls of a well bore penetrating a subterranean corrosive fluid disposal zone and allowed to harden therein.
In order to reduce the cost of completing a disposal well in accordance with this invention, the portion of the pipe string within the subterranean zone in which corrosive fluids are to be disposed of is sealed with the epoxy sealing composition of this invention while one or more other portions of the pipe string are sealed with a less expensive hydraulic cement composition. Thus, another improved method of the present invention is comprised of the following steps. A pumpable, water compatible, corrosion resistant, hardenable epoxy sealing composition is prepared and a hydraulic cement sealing composition is also prepared. The hydraulic cement sealing composition is displaced with the epoxy sealing composition into and through the annulus between a string of pipe and the portion of the well bore penetrating the subterranean corrosive fluid disposal zone. The displacement is stopped when the epoxy sealing composition spans the annulus between the string of pipe and the portion of the well bore penetrating the subterranean corrosive fluid disposal zone and the displaced hydraulic cement composition spans the annulus between the string of pipe and another portion of the well bore. Thereafter, the hardenable epoxy sealing composition is allowed to harden and the hydraulic cement sealing composition is allowed to set.
The hardenable epoxy sealing compositions of this invention comprised of a water compatible, hardenable epoxide containing liquid and a hardening agent can also include a particulate filler and one or more organosilane compounds which provide bond strength to the hardened composition.
It is, therefore, a general object of the present invention to provide improved methods of completing corrosive fluid disposal wells.
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 present invention provides improved methods of completing disposal wells, i.e., methods of sealing pipe strings in a well bore penetrating a subterranean zone into which corrosive fluids are to be disposed of (hereinafter referred to as a “subterranean corrosive fluid disposal zone”). In accordance with the present invention, a pumpable, corrosion resistant, hardenable epoxy sealing composition which can be displaced by or otherwise contacted with water or a water containing fluid without the occurrence of premature hardening or other adverse result is utilized. Upon hardening, the epoxy sealing composition can withstand the effects of contact with corrosive fluids as well as pipe movements due to expansion, contraction, impacts, shocks and the like.
In accordance with a method of this invention, a pumpable, water compatible, corrosion resistant, hardenable epoxy sealing composition which hardens into a resilient solid impermeable mass is prepared, placed in the annulus between a pipe string and the walls of a well bore penetrating a subterranean corrosive fluid disposal zone and allowed to harden therein. The hardenable, corrosion resistant, epoxy sealing compositions which are useful in accordance with this invention are comprised of a water compatible, hardenable epoxide containing liquid or a mixture of such liquids and a hardening agent for the epoxide containing liquid. The hardenable epoxy sealing compositions are compatible with water so that they can be displaced by or otherwise contacted with water with
Chatterji Jiten
Cromwell Roger S.
Eoff Larry S.
King Bobby J.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Roddy Craig W.
Suchfield George
LandOfFree
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