Wells – Processes – Cementing – plugging or consolidating
Reexamination Certificate
2001-08-30
2002-06-11
Suchfield, George (Department: 3672)
Wells
Processes
Cementing, plugging or consolidating
C166S300000, C175S072000, C507S219000, C523S130000
Reexamination Certificate
active
06401817
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improved compositions for sealing subterranean zones and methods of utilizing the compositions.
2. Description of the Prior Art
In the drilling of oil and gas wells using the rotary drilling method, drilling fluid is circulated through the drill string and drill bit and then back to the surface by way of the well bore being drilled. The drilling fluid maintains hydrostatic pressure on the subterranean zones through which the well bore is drilled and circulates cuttings out of the well bore. During such drilling, subterranean vugs, fractures and other highly permeable zones are often encountered whereby the drilling fluid circulation is lost into the zones and drilling operations must be terminated while remedial steps are taken. Also, when a subterranean zone is penetrated containing fluids under pressure which exceeds the hydrostatic pressure exerted on the zone by the drilling fluid, formation fluid crossflows and/or underground blow-outs can and often do occur.
Heretofore, a variety of compositions have been developed and used for combating lost circulation, crossflow and underground blow-out problems. However, such compositions have often been unsuccessful due to delayed and inadequate viscosity development by the compositions. For example, a variety of compositions containing hydraulic cement or the like have been used in attempts to stop lost circulation. The lost circulation is usually the result of encountering weak subterranean zones that contain natural fractures and/or are fractured by drilling fluid pressures and rapidly break down. When a cement or other slow setting composition is squeezed into the zone, the delay in developing high viscosity allows the sealing composition to be diluted and displaced into the zone whereby it bypasses the fractures and vugs causing the lost circulation. The same type of problem often occurs when crosslinked hydrated gels and other similar sealing compositions are utilized.
Thus, there are needs for improved compositions and methods of sealing subterranean zones using the compositions whereby the compositions develop ultra high viscosities in a few seconds or minutes and thereafter harden into firm but resilient sealing masses.
SUMMARY OF THE INVENTION
Improved compositions and methods of using the composition for sealing subterranean zones are provided which overcome the deficiencies of the prior art and meet the needs described above. The sealing compositions and methods are particularly suitable for sealing subterranean zones containing drilling fluids formed of oil, water containing divalent cations and/or water-in-oil emulsions, known in the art as inverted emulsions.
A first sealing composition of this invention for sealing zones containing oil or water based drilling fluids is basically comprised of water, an aqueous rubber latex, an organophilic clay, sodium carbonate, an epoxy resin and a hardening agent for the epoxy resin. The composition can also include one or more latex stabilizers, dispersing agents, biopolymers, defoaming agents, foaming agents, emulsion breakers, fillers, rubber vulcanizing agents and the like.
A second sealing composition of this invention for sealing subterranean zones containing oil or water based drilling fluids is basically comprised of an aqueous rubber latex, a latex stabilizing surfactant, an epoxy resin and a hardening agent for the epoxy resin.
A third inventive sealing composition for sealing subterranean zones containing water based drilling fluids is basically comprised of a water swellable clay, a silane coupling agent, an epoxy resin and a hardening agent.
When the first and second sealing compositions described above contact oil, water containing divalent cations or oil-water emulsions in a well bore, the rubber latex is destabilized whereby the rubber is precipitated thereby forming the sealing composition into a viscous mass. When the sealing composition includes an organophilic clay, the organophilic clay simultaneously reacts with the oil to instantly form an ultra-high viscosity rubbery mass. The third sealing composition described above includes a water swellable clay which forms the composition into a viscous mass when it contacts water. The viscous masses formed by the sealing compositions remain in the zones to be sealed until the epoxy resin in the sealing compositions is hardened by the hardening agent which forms the compositions into firm but resilient sealing masses which retain their shape, have compressive strength and effectively seal the subterranean zones.
The methods of this invention basically comprise the steps of preparing a sealing composition of this invention, introducing the sealing composition into a subterranean zone to be sealed and allowing the sealing composition to form a firm but resilient sealing mass in the subterranean zone.
It is, therefore, a general object of the present invention to provide improved compositions for sealing subterranean zones and methods of using the compositions.
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
As mentioned above, in the drilling of wells, subterranean zones are often encountered which contain high incidences of natural vugs and fractures. As a result, drilling fluid circulation is often lost which requires the termination of the drilling and the implementation of remedial procedures which are often of long duration and high cost. Such remedial procedures have heretofore involved the placement of hardenable compositions such as Portland cement compositions or crosslinked stiff gels and the like in the lost circulation zone. However, as mentioned above, because such compositions require considerable time to harden or gel, successful plugging of the zone often does not take place. In addition to drilling fluid loss circulation zones, zones containing pressurized fluids can be encountered which cause gas, oil and/or water crossflows that dilute and wash away sealing compositions. Also, underground blow-outs at low to high formation fluid flow rates can take place.
The present invention provides improved compositions for sealing subterranean zones and terminating the loss of drilling fluid, crossflows and/or underground blow-outs. The compositions are particularly suitable for use in wells containing oil, water containing divalent cations and/or water-in-oil emulsions. When a composition of this invention contacts oil or water containing divalent cations in the well bore, it instantly forms a viscous sealing mass. As the viscous sealing mass is displaced through the well bore, it enters and seals vugs, fractures and other highly permeable zones through which fluid is lost. Upon entering such zones, the viscous sealing composition is retained in the zones long enough for the epoxy resin therein to harden and form a firm but resilient sealing mass which retains it shape, has compressive strength and effectively seals the zones.
The sealing compositions of this invention are self diverting and plug multiple weak zones in a single well treatment. When a well contains a crossflow or underground blow-out, the sealing compositions plug all the lower pressure weak zones penetrated by the well bore and as the pressure in the well bore is increased, the crossflow or blow-out zone is also plugged. The resulting sealed well bore achieved by the sealing compositions of this invention can hold higher drilling fluid weights and the sealing compositions produce a wedging effect in plugged fractures that increases the integrity of the entire sealed formation or zone.
A first sealing composition of the present invention is basically comprised of water, an aqueous rubber latex, an organophilic clay, sodium carbonate, an epoxy resin and a hardening agent for the epoxy resin. The aqueous rubber latex present in the composition is caused to destabilize by oil
Chatterji Jiten
Cox Ricky A.
Cromwell Roger S.
Dennis, Jr. John L.
Griffith James E.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Roddy Craig W.
Suchfield George
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