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  Method of servicing a wellbore with a sealant composition comprising solid latexUSPTO Application #: 20070111901Title: Method of servicing a wellbore with a sealant composition comprising solid latex Abstract: A method of servicing a wellbore comprising placing a sealant composition comprising solid latex into the wellbore. (end of abstract)
Agent: Craig W. Roddy Halliburton Energy Services - Duncan, OK, US Inventors: B. Raghava Reddy, Ronald E. Sweatman, Chris L. Gordon USPTO Applicaton #: 20070111901 - Class: 507221000 (USPTO) Related Patent Categories: Earth Boring, Well Treating, And Oil Field Chemistry, Well Treating, Contains Organic Component, Organic Component Is Solid Synthetic Resin, Resin Is Polymer Derived From Ethylenic Monomers Only (e.g., Maleic, Itaconic, Etc.) The Patent Description & Claims data below is from USPTO Patent Application 20070111901. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is related to commonly owned U.S. patent application Ser. No. 10/______, [Attorney Docket No. 2005-IP-017357U1] entitled "Sealant Compositions Comprising Solid Latex," filed on the same date as the present application and incorporated by reference herein. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] Not applicable. BACKGROUND OF THE INVENTION [0003] 1. Field of the Invention [0004] This invention relates to servicing a wellbore. More specifically, it relates to the use of solid latex in wellbore servicing fluids. [0005] 2. Background of the Invention [0006] Natural resources such as gas, oil, and water residing in a subterranean formation or zone are usually recovered by drilling a wellbore down to the subterranean formation while circulating a drilling fluid in the wellbore. After terminating the circulation of the drilling fluid, a string of pipe, e.g., casing, is run in the wellbore. The drilling fluid is then usually circulated downward through the interior of the pipe and upward through the annulus, which is located between the exterior of the pipe and the walls of the wellbore. Next, primary cementing is typically performed whereby a cement slurry is placed in the annulus and permitted to set into a hard mass (i.e., sheath) to thereby attach the string of pipe to the walls of the wellbore and seal the annulus. Subsequent secondary cementing operations may also be performed. [0007] Fluids used in servicing a wellbore may be lost to the subterranean formation while circulating the fluids in the wellbore. These fluids may enter the subterranean formation via various types of leak-off flow paths in permeable zones such as depleted zones, zones of relatively low pressure, lost circulation zones having naturally occurring fractures, weak zones having fracture gradients exceeded by the hydrostatic pressure of the servicing fluid, and so forth. As a result, the service provided by such fluids is more difficult to achieve. Also, the loss of such fluids increases the cost of the overall operation due to the prolonged rig time required, the fluids being relatively expensive, and possibly a need to install additional casing. [0008] There are a variety of methodologies for combating drilling fluid circulation losses. Such methodologies may involve adding loss prevention materials to the drilling fluid itself and continue the drilling process or pump fluid until fluid circulation is restored or may involve the use of a two-stream process. In a two-stream process, two fluid streams are introduced to the loss circulation area, for example by pumping one stream down the drillstring and one stream down the annulus, or alternatively via sequential pumping down the drillstring, annulus or both. These streams when mixed downhole near the loss circulation zones combine to rapidly form a viscous mass, which is designed to prevent further loss of drilling fluid into the fractures. [0009] When such methods are successful in mitigating drilling fluid circulation losses, the operators have two options for follow-up operations. Their first option is to temporarily stop the drilling operation, case the well bore and cement the casing before resuming further drilling. This may result in a reduced well bore diameter from that point forward resulting in a smaller than planned pipe across the production intervals. During production, these reduced production pipe string diameters induce high friction pressures that restrict or limit production rates and negatively effect well production economics. This practice is adapted when the loss circulation sealant is not strong enough to withstand hydrostatic pressure of the drilling fluid if drilling is resumed without casing the well bore. The second option is more economical during the well construction phase and more profitable during the production phase. The second option involves using a loss circulation sealant that provides sufficient strength and reinforcement to the loss circulation zone so that it can withstand hydrostatic pressure from further drilling without resorting to casing the wellbore. This strengthening process is often referred to as increasing the Wellbore Pressure Containment Integrity (WPCI). This will not only save the cost of installing the extra casing or liner pipe strings, but it will also allow well completion with the planned well bore diameter that is required to achieve the expected production rates. In some cases, it will also lead to a wider than planned well bore diameter which after well completion and suitable stimulation operations, may facilitate increased production rates. The second option is a process referred to as a "Drill Ahead" process in the industry and in the later sections of this application. A "Drill Ahead" process and associated methods for introducing WPCI compositions into a wellbore to seal subterranean zones are described in U.S. Pat. No. 6,926,081B2, and in U.S. patent application Ser. No. 10/350,429 entitled "Methods of Improving Well Bore Pressure Containment Integrity" and filed on Jan. 24, 2003, which are incorporated by reference herein in their entirety. [0010] Sealant compositions for use in fluid circulation losses may contain modifiers to enhance the mechanical properties of the sealant. Latex emulsions, which may contain a stable water-insoluble, polymeric colloidal suspension in an aqueous solution, are commonly used in sealant compositions to improve the properties of those compositions. For example, latex emulsions are used in cement compositions to reduce the loss of fluid there from and to reduce the cement's permeability to gas thereby substantially increasing the cement's resistance to gas flow from a gas-bearing formation. Latex emulsions are also employed to reduce the brittleness and improve the flexibility of sealant compositions; otherwise, the compositions may shatter under the impacts and shocks generated by drilling and other well operations. For example, with regard to fluid circulation loss, a two-stream process has been used where the first stream may be the drilling fluid itself or a designed fluid containing key ingredients while the second stream may comprise a latex emulsion. This process has found good commercial success in combating drilling fluid circulation losses especially in the case of oil-based muds (OBM). [0011] The use of latex emulsions for combating drilling fluid circulation losses has some disadvantages. In the case of the two stream processes, preparing the latex-containing stream is operationally cumbersome and requires mixing an aqueous latex fluid, an aqueous stabilizing liquid surfactant and a dry solids blend prior to placing in a wellbore. This operation requires storage of two fluid components and a dry solid component. Also, there can be a substantial costs incurred for the shipping, storing and handling of latex emulsions. Furthermore, latex emulsions and the aqueous stabilizing surfactants present potential spill and leak related health, safety and environment (HSE) hazards. Frequently, it is operationally preferred and more cost effective to design cement slurries that use all solid components so that a single dry blend can be made in a bulk blending facility and transported to the field location where it is mixed with water prior to pumping. Use of aqueous latex emulsion requires more complex mixing operations. [0012] Given the foregoing problems it would be desirable to develop a method of reducing the costs and HSE hazards associated with the use of latex in sealant compositions. Furthermore, it would be desirable to develop a method of preparing sealant compositions with latex that is operationally facile. BRIEF SUMMARY OF SOME OF THE PREFERRED EMBODIMENTS [0013] Disclosed herein is a method of servicing a wellbore comprising placing a sealant composition comprising solid latex into the wellbore. [0014] The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0015] Disclosed herein are sealant compositions comprising a solid latex. Such compositions may additionally comprise cement. Such compositions may additionally comprise an organophilic clay, one or more viscosifiers, or combinations thereof. In various embodiments, the sealant composition comprises a solid latex and cement; alternatively, a solid latex, cement, and an organophilic clay; alternatively, a solid latex, cement, and one or more viscosifiers; alternatively a solid latex, cement, an organophilic clay and one or more viscosifiers; alternatively solid latex and organophilic clay; alternatively solid latex and one or more viscosifiers; or alternatively a solid latex, organophilic clay, and one or more viscosifiers. In various embodiments, the sealant composition comprising a solid latex may be contacted with one or more other fluids prior to, during, after, or concurrently with being placed down hole, for example contact with an oil based mud (OBM), a water based mud (WBM), an aqueous fluid containing a pH increasing material, or a combination thereof. [0016] The sealant composition can be used for any purpose, for example as loss circulation fluids, fracture sealants, zonal isolation fluids, and cementing fluids. In an embodiment, the sealant composition may be used to service a wellbore that penetrates a subterranean formation. It is to be understood that "subterranean formation" encompasses both areas below exposed earth and areas below earth covered by water such as ocean or fresh water. Without limitation, servicing the wellbore includes positioning the sealant composition in the wellbore to isolate the subterranean formation from a portion of the wellbore; to support a conduit in the wellbore; to plug a void or crack in the conduit; to plug a void or crack in a cement sheath disposed in an annulus of the wellbore; to plug an opening between the cement sheath and the conduit; to prevent the loss of aqueous or non-aqueous drilling fluids into loss circulation zones such as a void, vugular zone, or fracture; to be used as a fluid in front of cement slurry in cementing operations; to seal an annulus between the wellbore and an expandable pipe or pipe string; or combinations thereof. [0017] In an embodiment, the sealant composition comprises a solid latex, a reconstituted solid latex or combinations thereof. Herein a "solid latex" refers to latex which is a free flowing particulate material that is substantially dry or free of fluid. Solid latexes may be prepared by removing water from any emulsion polymerized polymer systems such as those to be described herein. Methods of removing the water from emulsion polymerized polymer systems are known to one of ordinary skill in the art and include without limitation techniques such as spray drying. Herein a "reconstituted solid latex" refers to a latex solution or emulsion, typically a stable emulsion, that is prepared from a solid latex. Herein "reconstituting" refers to the process of resuspending or solvating a solid latex in a suitable fluid. Aqueous fluids such as fresh or salt water and/or nonaqueous fluids such as diesel, kerosene, mineral oil, esters, linear and poly alpha-olefins, or combinations thereof may be used to resuspend the solid latex and form a stable latex emulsion. A reconstituted solid latex is formed from dry latex particles, which is in contrast to a liquid latex emulsion that is formed by emulsion polymerization in which the polymer particles have remained in a liquefied state and have not undergone a dry, particulate state. [0018] An emulsion polymerized latex system may comprise monomers that include polar monomers and non-polar monomers such as ethylenically unsaturated carboxylic acids (e.g., acrylic acid), vinyl nitrile (e,.g., acrylonitrile), aromatic and aliphatic olefins and dienes, or combinations thereof. For example, the solid latex may comprise latex formed from monomers that include, without limitation, vinyl aromatic monomers (e.g., styrene based monomers), ethylene, butadiene, vinylnitrile (e.g., acrylonitrile), olefinically unsaturated esters of C.sub.1-C.sub.8 alcohol, ethylenically unsaturated carboxylic acids, or combinations thereof. In some embodiments, non-ionic monomers that exhibit steric effects and that contain long ethoxylate or hydrocarbon tails may also be present. Other suitable types of solid latexes may be prepared from colloidally stabilized or alkali swellable latexes as disclosed herein. Suitable emulsifying surfactants may be included during the polymerization phase to obtain a stable emulsion. An example of a solid latex includes without limitation RHOXIMAT PSB 150 latex powder which is a styrene butadiene copolymer resin in powder form commercially available from Rhodia Corporation, Cranbury, N.J. [0019] In an embodiment, the solid latex is prepared from a colloidally stabilized latex emulsion. As used herein, "colloidally stabilized latex emulsion" refers to a latex comprising polymer particles suspended in an aqueous solution and at least one protective colloid for providing stabilization to the colloidal polymer emulsion. Protective colloids known in the art may be employed in the colloidally stabilized latex emulsion. Examples of suitable protective colloids include, but are not limited to, partially and fully hydrolyzed polyvinyl alcohols, cellulose ethers such as hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, starch and starch derivatives, and carboxymethyl cellulose, natural and synthetic gums such as gum tragacanth and gum arabic, polyacrylic acid, acrylates, poly(vinyl alcohol)co(vinyl amine) copolymers, and combinations thereof. Continue reading... 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