Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-05-25
2001-01-23
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C166S294000, C166S337000, C523S131000, C523S335000, C524S191000, C524S210000, C524S213000, C524S263000, C524S284000, C524S315000, C524S319000, C528S486000, C528S487000, C528S488000, C528S490000, C528S491000, C528S492000
Reexamination Certificate
active
06177483
ABSTRACT:
The present invention relates to a latex-based setting composition for completion and remedial operations, such as sealing, cementing or isolating, performed in subterranean zones penetrated by a borehole.
BACKGROUND OF THE INVENTION
In the development, completion, and operation of natural hydrocarbon reservoirs, various setting systems are in use.
These systems are used for sealing or cementing the region between metal casing and the formation wall. Other applications include the hydraulic isolation of abandoned or productive zones as described for example in the published International patent application WO-9500739.
The known setting systems are based on either cementitious materials, e.g. cements, particularly Portland cements, blast furnace slag, fly ash/lime mixes and mixtures of these materials, on other ceramic-forming materials, or on polymer materials, such as thermosetting polymers.
Cement-based setting compositions are known for example from U.S Pat. Nos. 4,721,160 and 5,258,072. In some of the known compositions a styrene/butadiene latex is added to the cement in order to impart certain desirable properties, such as fluid loss control, to the composition.
A rubber latex based composition for use in completion or remedial operations in subterranean formations or wellbores is described in the U.S. Pat. No. 5,159,980. The disclosed compositions are comprised of an aqueous dispersion of rubber, a vulcanizing agent and a vulcanization activator. A solid rubber plug or seal is formed therefrom by allowing the compound to vulcanize. The known composition is not thixotropic and therefore not applicable for important operations in horizontal wells.
U.S. Pat. No. 4,649,998 describes a rubber based emulsion for consolidating sand particles. The emulsion also contains an ester which by hydrolysation reduces the pH of the emulsion and thus causes the nitrile rubber to coat the sand grains. The known emulsion is highly specifically designed for sand consolidation and has little use in many other remedial operations, e.g. for plugging formation and the like.
In view of the ever increasing demand for improved well completion and remedial operation techniques, it is an object of the present invention to provide a latex-based setting composition which can be adjusted to a broad range of setting times.
Another object of the present invention is to provide a setting system for wellbore application with improved pumpability. Various well completion and remedial operation require the setting system to be pumpable through small holes, gravel packers, or slotted liners. In particular for coiled tubing, where the diameter of the drill string is small compared to conventional drill strings, the known compositions often suffer a significant frictional pressure drop.
SUMMARY OF THE INVENTION
The above-mentioned objects are achieved by a composition as set forth in the appended claims.
It is regarded as an important feature of the invention that the new composition is latex-based i.e., its main dry component is a latex. Preferably the part of the latex in the dry weight of the composition is larger than 50%, and most preferably larger than 70%.
In contrast to most of the known compositions for use in subterranean zones, the composition in accordance with the present invention is not based on cementitious materials, such as limestone, chalk, marl etc. Some preferred formulations are essentially free from any calcareous additives, though argillaceous components might be added to impart thixotropic properties to the composition. A preferred embodiment of the invention is characterized in that the mean particle size is below 10 microns, preferably below 1 micron. The mean is defined herein as in general statistics. The pumpability of these “solid- free” compositions is significantly improved.
In other known latex-based compositions, such as described in U.S. Pat. No. 5,159,980, a solid rubber plug or seal is formed by a process known as “vulcanization”. The vulcanization process involves the chemical cross-linking of polymer chains by covalent bonding, usually through sulfur bridges. In the present invention the latex-based composition is solidified by a process known as “coagulation”. The coagulation process is caused by a destabilization of the latex emulsion, that leads to an aggregation of the latex particles or colloids without forming a chemical bond between adjacent polymers. Although coagulation is used as the sole, or predominant method, the use of conventional cross-linking as an auxiliary bonding mechanism can be advantageous for applications which require a setting system with a high mechanical strength.
The latex component in the composition can be chosen from any latex material which is capable of forming a solid in a controllable setting time, in particular at high temperatures.
High temperatures in the context of the present invention are defined as temperatures in the range of 40 to
150_C at pressures up to
1000 bar and possibly higher. Suitable latices include natural and synthetic rubbers, in particular anionic variants thereof. For example, natural rubber (cis-1,4-polyisoprene) in most of its modified types can be utilized.
Synthetic polymers of various types can also be used including styrene-butadiene rubber (SBR), cis-1,4-polybutadiene rubber and blends thereof with natural rubber or styrene-butadiene rubber, high styrene resin, butyl rubber, ethylene-propylene rubbers (EPM and EPDM), polychloroprene rubber, nitrile rubber, cis-/tr-1,4-polyisoprene rubber, silicone rubber, chlorosulfonated polyethylene rubber, epichlorohydrin rubber, fluorocarbon rubber, fluorosilicone rubber, polyurethane rubber, polyacrylic rubber and polysufide rubber.
It is also feasible to combine two or more latices so as to provide a composition or blend optimized for a specific operation.
The setting time for a composition in accordance with the invention is at least 2 h and possibly up to 8 h or more. It is seen as a further characteristic feature of the present invention that the composition comprises a pH-reducing agent that is adapted to lower within a pre-determined time period the pH of the latex emulsion to one at which the latex coagulates.
The pH-reducing agent reduces the initially high pH value (>10) of an anionic latex emulsion, thus accelerating and facilitating its coagulation. Suitable agents are slowly reacting acids or buffering materials which stabilize the pH at lower values, preferably between 8 and 9.
Preferred pH reducing reactants can be selected from a group comprising ester or amides of water soluble acids that preferably hydrolyze at moderate rates at reservoir temperatures. Suitable reactants include amides of soluble carboxylic acids, such as formamide, urea, acetamide, dimethyl formamide, 2-chloroacetamide; amides of sulfonic acids, such as methane sulfonamide; inorganic acids amides, such as sulfamide; water soluble esters of water soluble organic acids, such as methyl acetate, methyl gallate, the acetates of alcoholes, glycols, or hydroxy compounds; water soluble and readily hydrolysable organic halides, such as sodium trichloride, methyle iodide, sodium monochloroacetate, or 3-chloro-1-propanol.
The control of the setting time is improved by combining the pH reducing agent with an internal coagulant or latex gelling agent. Usually a coagulant is applied to destabilize the latex emulsion and hence causing the formation of a solid rubber.
Suitable coagulants can be selected from a group comprising sodium or potassium silicofluorides, and ammonium salts, such as ammonium nitrate, chloride, or sulfate. Some of these coagulants are effective at elevated temperatures, i.e., above room temperature. The amount of added coagulants ranges from 1 to 10 weight parts per hundred of dry rubber (phr), preferably from 1 to 5 phr.
It is regarded as an important advantage of the present invention that by adjusting the respective concentration of coagulant and pH-reducing agent it is possible to control the setting time of the composition. Achievable delay times for the setting pro
Davies Stephen N
Maitland Geoffrey C
Tehrani Mostafa A
Nava Robin C.
Niland Patrick D.
Schlumberger Technology Corporation
LandOfFree
Setting composition for well operations does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Setting composition for well operations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Setting composition for well operations will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2552220