NO20120353A1 - Sonically activated stiffenable mixture and method using the same - Google Patents

Abstract

The present invention relates to a system and method for sonically activating cement slurries. In some implementations, a method of treating an underground formation includes placing a stiffenable mixture including a capsule in a wellbore. The capsule is used to increase the stiffening rate in response to at least sonic signals. A sonic signal is transmitted to at least a portion of the stiffenable mixture to release an activator from the capsule. In some implementations, a mixture for treating an underground formation includes a stiffenable mixture and an activator. The activator is released in response to a sonic signal to initiate stiffening of the stiffenable mixture.

Description

Sonically activated curable mixtures and method of activating such

Technical area

The present invention relates to cementing operations and more specifically to the sonic activation of hardenable mixtures, as well as methods for sonically activating cement mixtures.

Background

Certain well holes, such as certain oil and gas wells, are lined with casing. The casings stabilize the sides of the wellbore. During cementing operations, cement is brought down the wellbore and into the annulus between the casing and the surrounding ground. The cement secures the casing in the wellbore and prevents fluids from flowing vertically in the annulus between the casing and the surrounding ground. Different cement formulations have been made for a range of well conditions which may be above ambient temperature and pressure. When composing a cement formulation, a number of potential mixtures can be evaluated to determine their mechanical properties under different conditions.

Summary

The present invention relates to a system and a method for sonically activating cement slurries. In some implementations, a method of treating a subterranean formation includes positioning a solid base mixture including a capsule in the wellbore. The capsule is used to increase the hardening rate in response to at least sonic signals. A sonic signal is transmitted to at least a portion of the curable mixture to release an activator from the capsule.

The details of one or more embodiments of the invention are presented in the attached drawings and the description below. Other features, objects and advantages of the invention will be obvious from the description, figures and from the patent claims.

In some implementations, a composition for treating a subterranean formation includes a curable composition and an activator. The activator is released in response to a sonic signal to initiate solidification of the curable mixture.

According to one aspect of the present invention, there is provided a method comprising positioning solidifiable mixtures in a wellbore and transmitting a sonic signal in the solidifiable mixture to initiate solidification, using a mechanism directly responsive to the sonic signal.

The method is suitable for solidifying a solidifiable mixture. Thus, in another aspect of the present invention, there is provided a method of solidifying a curable mixture comprising positioning the curable mixture in a wellbore and transmitting a sonic signal into the curable mixture to initiate solidification using a direct responsive mechanism to the sonic signal.

In another aspect, there is provided a method of treating a subterranean formation comprising placing a solidifiable mixture including a capsule in a wellbore, the capsule being used to increase the rate of solidification in response to a sonic signal, and transmitting the sonic signal to the at least a portion of the settable composition to release an activator from the capsule, the activator being configured to increase the rate of setting of the settable mixture.

In a further aspect, there is provided a method of cementing in a subterranean formation comprising placing a cement mixture containing a capsule in a wellbore, the capsule encapsulating an activator configured to increase the rate of solidification of the hardenable mixture and to transmit a sonic signal to at least part of the cement mixture to release the activator from the encapsulating capsule.

In a further aspect, there is provided a composition for treating a wellbore comprising a curable mixture, and either: (i) An activator, the activator being released in response to a sonic signal to initiate solidification of the curable mixture, or (ii) A setting retarder in that the setting retarder responds to a sonic signal to

accelerate hardening of the hardenable mixture.

Thus, in one aspect, the present invention provides a composition for treating a wellbore comprising a curable mixture and an activator, the activator being released in response to a sonic signal to initiate solidification of the curable mixture.

In another aspect, the present invention provides a composition for treating a wellbore comprising a settable mixture and a setting retarder, the setting retarder being responsive to a sonic signal to accelerate setting of the settable mixture.

Description of figures

Figure 1 is an example of a well system for producing fluids from a production zone.

Figures 2a and 2B are examples of cementing processes in a well system of Figure 1.

Figures 3A and 3B illustrate an example of an activation device for activating cement slurry in a wellbore,

Figures 4A and 4B illustrate exemplary processes for releasing activators into cement slurries.

Figure 5 is a flowchart illustrating an example method for activating a deposited cement slurry.

Figure 6 is a flow chart showing an example method of fabricating capsules,

Figures 7A-F show example capsules for activating a cement slurry in the system of Figure 1. Figure 8 is another example well system for producing fluids from a production zone, and Figures 9A-H show example graphs demonstrating the effect of sonic signals on cement slurries. .

Like reference numbers in the different drawings indicate like elements.

Detailed description

The present invention relates to one or more well systems having "on command" cement delivery systems which selectively control solidification of cement slurry. For example, the disclosed system may use sonic irradiation (eg, ultrasound, terahertz) such as in the range of about 20 Hz to 2 MHz, to release activators to initiate or accelerate cement setting (see Figure 1) and/or may use ultrasound to directly to activate or accelerate cement slurries (see Figure 8). In some cases, the described systems may include a cement slurry and capsules that release activators in the cement slurry in response to ultrasound. An activator typically includes any chemical that activates and/or accelerates the setting process of a cement slurry in the described systems. An activator can also slow down or otherwise affect the setting properties of the cement slurry. For example, the described systems may include one or more of the following activators, sodium hydroxide, sodium carbonate, calcium chloride, calcium nitrite, calcium nitrate and/or others. In some implementations, the capsules may include elements that substantially enclose one or more activators and that release the activator in response to at least sonic signals. For example, the sonic signal may break or otherwise create an opening in the encapsulating member to release the one or more activators.

With respect to directly activating cement slurries, the disclosed systems can directly affect the cement slurries using one or more mechanisms responsive to sonic signals. The one or more different mechanisms may include modifying chemical properties, releasing chemicals, modifying physical properties (eg particle size). Update operating conditions (eg pressure, temperature), and/or other mechanisms responsive to sonic signals. For example, the disclosed systems can use sonic signals to directly minimize or otherwise reduce the effect of hydrophobic surfactants, for example, to enable surfactants to enter suspension and/or partially hydrated. In these cases, the described systems can directly activate cement slurries using sonic signals regardless of the introduction or addition of chemicals to the cement slurry. In addition, the systems can include free radical dopants in cement slurries that autocatalytically release free radicals in response to at least ultrasonic signals. Alternatively or in combination, the sonic signals can trigger or otherwise activate a polymerization process in the cement slurry to provide in situ polymerization. In general, the described systems include a cement slurry in an annulus formed between a casing and a wellbore, and once the cement has set it will hold the casing in place. By selectively controlling the solidification of a cement slurry, the disclosed systems may allow the cement properties to be tailored as soon as the cement slurry has been pumped down the wellbore.

Reference is now made to figure 1 where system 100 is a cross-section of well system 100 which initiates or accelerates solidification of cement slurry using encapsulated activators. In the illustrated embodiment, the well system 100 includes a production zone 102, a non-producing zone 104, a wellbore 106, a cement slurry 108, and capsules 110. The production zone 102 may be an underground formation that includes resources (eg, oil, gas, water). The non-producing zone 104 may be one or more formations isolated from wellbore 106 using cement slurry 108. For example, zone 104 may include contaminants that, if mixed with the resources, may require further processing of the resources and/or render production uneconomic uninteresting. Cement slurry 108 can be pumped or selectively positioned in the wellbore 106 and solidification of cement slurry 108 can be activated or accelerated using the capsules 110. In some implementations, the capsules 110 can release activators in response to ultrasound initiated by, for example, a user of system 100. controlling the setting, the user can configure the system 100 without significant interference from the setting of cement slurry 108.

We now turn to a more detailed description of the elements of system 100, where the wellbore 106 extends from the surface 112 to the production zone 102. The wellbore 106 may include a rig 114 which is arranged near the surface 112. The rig 114 may be connected to casing 116 which extends the entire length of the wellbore or a substantial length of the wellbore 106 from approximately at the surface 112 towards the production zone 102 (eg hydrocarbon containing reservoir). In some implementations, casing 116 may extend to near an end station 118 of the well 106. In some implementations, the wellbore 106 may be completed with the casing 116 extending to a predetermined depth near the production zone 102. In short, wellbore 106 extends in a substantially vertical direction down towards the production zone 102. In some implementations, the wellbore 106 may include other parts that are horizontal, inclined or otherwise deviating from vertical.

The rig 114 may be centered over an underground oil or gas formation 102 located below the earth's surface 112. The rig 114 includes a work deck 124 that carries a crane 126. The crane 126 supports a health device 128 to raise and lower tubing strings then a casing 116. Pump 130 is capable of pumping a variety of well mixtures (eg drilling fluid, cement) into the well and includes a pressure measuring device which provides a pressure reading at the pump outlet. Well hole 106 has been drilled through various soil strata, including formation 102. When completing the well drilling, casing 116 is often placed in well 106 to support production of oil and gas from formation 102. Casing 116 is a pipe string that extends down through well hole 106 through which oil and gas will eventually be extracted. A cement or guide shoe 132 is typically attached to the end of the casing string when the casing is lowered into the wellbore. The guide shoe guides the casing toward the center of the hole and can minimize or otherwise reduce problems associated with hitting rock ledges or washouts in the wellbore 106 when the casing is lowered into the well. The guide shoe 132 can be a guide shoe or a float shoe and typically comprises a tapered, preferably projectile-shaped end which is located at the lower end of casing string 116. Guide shoe 132 can be a float shoe equipped with an open bottom and a piston that serves to prevent reverse flow, or U-pipe, of cement slurry 108 from annulus 122 into casing 116 after cement slurry 108 has been placed in annulus 122. The area between casing 116 and the wall of wellbore 106 is known as casing annulus 122. To fill up casing annulus 122 and hold casing 116 in place, casing 116 is usually "cemented" in wellbore 106, which is referred to as "primary cementing". In some implementations, the cement slurry 108 can be injected through one or more ports 134 in the guide shoe 132. The cement slurry 108 can flow through a hose 136 into the casing 116. In some cases where the casing 116 does not extend the entire length of the wellbore 106 to the surface 112, the casing 116 may be supported by an extension hanger 138 near the bottom of a previous casing 120.

In some implementations, the system 100 can activate solidification of cement slurry 108 using capsules 110 during, for example, a conventional, primary cementing operation. In conventional primary cementing operations, the capsules 110 can be mixed into the cement slurry 108 before it enters casing 116 and the cement slurry 108 can then be pumped down the inside of casing 116. For example, the capsules 110 can be mixed with the cement slurry 108 with a density of the range 0.48 - 2.9 kg/l. As slurry 108 reaches the bottom of casing 116, it flows out of casing 116 and into casing annulus 122 between casing 116 and the wall of wellbore 106. As the cement slurry flows up into annulus 122, it displaces any fluid in the wellbore. To ensure that no cement remains on the inside of casing 116, a device called a wiper plug can be pumped with a well maintenance fluid (for example, drilling mud) through casing 116 behind the cement slurry 108. The scraper contacts the internal surfaces of casing 116 and pushes any remaining slurry 108 out of casing 116. When the cement slurry reaches the soil surface 112 and the annulus 122 is filled with slurry 108, pumping is stopped.In connection with pumping cement slurry 108 into the annulus, an ultrasonic signal may be transmitted before, during and/or after pumping is completed to activate the capsules 110. In response to at least the slightest signal, the capsules may release activators that initiate and/or accelerate the solidification of cement slurry 108 in the annulus 122. Some or all of the casing 116 may be attached to nearby base material with hardened cement 202 as illustrated in Figures 2A and 2B. terings, the casing 116 comprises a metal. After solidification, the casing may be configured to carry a fluid, such as air, water, natural gas, or to carry an electrical wire, tubular string, or other elements.

After positioning of casing 116, the solidifiable mixture 108 containing capsules 110 can be pumped down into annulus 122 with a pump truck (not illustrated). While the following discussion will focus on the curable slurry 108 comprising a cement slurry 108, curable slurries 108 may also include other compounds such as resin systems (polymers), curable slurries, conformance fluids, anti-loss of circulation fluids and/or other curable mixtures. Example cement slurries 108 are discussed in more detail below. In connection with the deposition or other positioning of cement slurry 108 in annulus 122, the capsules 110 may release activators to activate or otherwise increase the hardening rate of cement slurry 108 in response to at least ultrasound. In other words, the released activators can activate cement slurry 108 to solidify in annulus 122.

In some implementations, for example, the capsules 110 may release an activator that initiates or accelerates solidification of cement slurry 108. For example, cement slurry 108 may remain substantially in the state of a slurry for a specified period of time, and capsules 110 may activate the cement slurry in response to ultrasound. In some cases, ultrasound can crack, break or otherwise form one or more holes in the capsules 110 to release the activators. In some cases, ultrasound can generate heat that melts one or more holes in the capsules 110. The capsules 110 enclose activators with, for example, a membrane, such as a polymer (for example, polystyrene, ethylene&/vinyl acetate copolymer, polymethyl methacrylate, polyurethanes, polylactic acid, polyglycolic acid, polyvinyl alcohol , polyvinyl acetate, hydrolyzed ethylene/vinyl acetate or copolymers of the aforementioned). The capsules 110 may include other materials that are responsive to ultrasound. In these implementations, the capsules 110 may contain a polymer membrane that ultrasonically breaks down to release the entrapped activators. In some cases, an ultrasonic signal can structurally change the membrane to release activators such as, for example, opening a previously formed gap in the capsules 110. In some implementations, at least one dimension of the capsules 110 can be microscopic, such as in the range of 10 nanometers (nm) to 15,000 nm. For example, the dimensions of the capsules 110 may be on the scale of a few tens to about a thousand nanometers and may have one or more external shapes including spherical, cubic, oval, and/or rod-shaped. In some implementations, the capsules 110 can be shells with a diameter in the range from about 10 nm to about 1000 nm. In other implementations, the capsules 110 may include a diameter ranging from about 15 micrometers to about 10,000 micrometers. Alternatively or in combination, the capsules 110 can be made of metal (for example gold) and/or non-metallic material (for example carbon). In some implementations, the capsules may also be coated with materials to enhance their tendency to be dispersed in cement slurry 108. The capsules 110 may be dispersed in the cement slurry at a concentration of 10<5> to 109 capsules/cm<3>. In some implementations, the capsule shell is selected from the group consisting of polystyrene, ethylene/vinyl acetate copolymer and polymethyl methacrylate, polyurethanes, polylactic acid, polyglycolic acid, polyvinyl alcohol, polyvinyl acetate, hydrolyzed ethylene/vinyl acetate and copolymers thereof.

The released activator may include sodium hydroxide, sodium carbonate, amine compounds, salts containing calcium, sodium, magnesium, aluminum and/or mixtures thereof. The capsules 110 may release a calcium salt such as calcium chloride. In some implementations, the capsules 110 can release a sodium salt such as sodium chloride, sodium aluminate and/or sodium silicate. The capsules 110 may release a magnesium salt such as magnesium chloride. In some examples, the capsules can release amine compounds such as triethanolamine, trippropanolamine, tri-isopropanolamine and/or diethanolamine. In some implementations, the capsules 11 may release the activator in an amount sufficient to solidify cement slurry 108 within about 1 minute to about 24 hours. In implementations including sodium chloride as the released activator, the concentration may range from about 3% by weight to about 30% by weight of the weight of the cement in the cement slurry 108. In implementations including calcium chloride as the released accelerator, the concentration may range from about 0 .5% by weight to about 5% by weight of the weight of the cement in cement slurry 108. In those cases where the hardenable slurry comprises resin, release activator may include amine accelerators for epoxy/novolac resins.

In some implementations, the capsules 110 can rapidly solidify cement slurry 108. As discussed in this document, the term "quick solidified" shall be understood to mean that the initiating solidification of cement slurry 108 occurs within approximately 1 minute to approximately 15 minutes after contact with the released activator. In some implementations, the previously identified activators may rapidly solidify cement slurry 108. Rapidly solidifying activators may include sodium hydroxide, sodium carbonate, potassium carbonate, bicarbonate salts of sodium or potassium, sodium silicate salts, sodium aluminate salts, iron (II) and iron (III) salts (for example, iron ( lll) chloride and iron (lll) sulfate), polyacrylic acid salts and/or others. In some implementations, the following activators can rapidly solidify the cement slurry 108 based on these activators exceeding a specified concentration: calcium nitrate, calcium acetate, calcium chloride and/or calcium nitrite. In some implementations, the capsules 110 can release a solid activator.

In some implementations, cement slurry 108 may include "delayed setting" cement mixtures that remain in a slurry state (eg, resistant to setting or gelling) for an extended period of time. In such implementations, a delayed setting cement slurry 108 may include a cement, a base fluid, and a setting retarder. In these and other implementations, activation can change the state of the cement slurry from delayed to neutral, to accelerated, or to less delayed. Cement slurry 108 may include other additives. The delayed cement slurry 108 typically remains in a slurry state for a period ranging from about 6 hours to about 4 days under well conditions or other conditions. With this said, cement slurry 108 may include components that result in a slurry state for longer or shorter periods of time. For example, cement slurry 108 may be mixed or otherwise made well in advance of positioning the slurry 108 in annulus 122. The delayed setting cement slurry 108 may, in some implementations, include a cement, a base fluid, and a setting retarder. The delayed cement slurry 108 may solidify at a desired time, such as after placement, by activating the capsules 110 to release one or more activators.

With respect to the cement included in cement slurry 108, any cement suitable for use in underground formations may be suitable for use in the present invention. For example, delayed setting cement slurry 108 may contain a hydraulic cement. In general, hydraulic cements typically contain calcium, aluminium, silicon, oxygen and/or sulfur and can harden and harden through reaction with water. Hydraulic cements include, but are not limited to Portland cements, pozzolanic cements, high aluminate cements, gypsum cements, silica cements, high alkali cements and/or Sorel cements. In addition, delayed setting cement slurry 108 may include cements based on shale or blast furnace slag. In these cases, the slate may include glazed schist, raw slate (for example, unburnt slate) and/or a mixture of raw slate and glazed slate. In some implementations, the curable mixture 108 may include a polymer additive comprising at least one monomer, prepolymer, an oligomer, or a short chain polymer that polymerizes in response to the sonic signal.

With regard to base fluid included in cement slurry 108, delayed setting cement slurry 108 may include one or more base fluids such as, for example, a water-based base fluid, a non-aqueous base fluid, or mixtures thereof. Aqueous fluids may include water from any source that does not contain an excess of compounds (e.g., organics, such as tannins) that may adversely affect other compounds in cement slurry 108. For example, delayed setting cement slurry 108 may contain fresh water, salt water (e.g., water containing one or more salts), brine (for example, saturated salt water) and/or seawater. Non-aqueous based can contain one or more organic liquids, such as mineral oils, synthetic oils, esters and/or others. In general, any organic liquid in which aqueous solutions of salts can be emulsified may be suitable for use as the base fluid in delayed setting cement slurry 108. In some implementations, the base fluid exceeds a concentration sufficient to form a pumpable slurry. For example, the base fluid may be water in an amount from about 25% to about 150% by weight of the cement ("bwoc") such as one or more of the following ranges: about 30 to 75% bwoc, about 35 to 50% bwoc , about 38 to about 46% bwoc and/or others.

With respect to setting retarders in cement slurry 108, cement slurry 108 may contain one or more different types of setting retarders, such as, for example, phosphonic acid, phosphonic acid derivatives, lignosulfonates, salts, organic acids, carboxymethylated hydroxyethylated celluloses, synthetic co- and terpolymers comprising sulfonate and carboxylic acid groups and/or borate compounds . And in some implementations, the setting retarders used in the present invention are phosphonic acid derivatives. Examples of setting retarders may include phosphonic acid derivatives commercially available from, for example, Solutia Corporation of St. Louis, Mo. Under the trade name "DEQUEST". Another example setting retarders may include a phosphonic acid derivative commercially available from Halliburton Energy Services, Inc. under the trade name "MICRO MATRIX CEMENT RETARDER". Examples of the borate compound may include sodium tetraborate, potassium pentaborate and/or others. A commercially available example of suitable solidification retarders comprising potassium pentaborate is available from Halliburton Energy Services, Inc. under the trade name "Component R". Examples of organic acids may include gluconic acid, tartaric acid and/or others. An example of a suitable organic acid may be commercially available from Halliburton Energy Services, Inc. under the trade name “HR.RTM. 25.” Other examples of solidification retarders may be commercially available from Halliburton Energy Services, Inc. under the trade names "SCR-100" and "SCR-500". Generally, set retarders in delayed setting cement slurry 108 may be present in an amount sufficient to delay setting in a subterranean formation for a specified period of time. The amount of setting retarder included in cement slurry 108 may be within one of the following ranges: about 0.1 to about 10% bwoc, about 0.5 to about 4% bwoc, and/or others.

In some implementations, cement slurry 108 may not contain a setting retarder. For example, system slurry 108 may contain high alumina cements and/or phosphate cements independent of setting retarder. In these cases, the activators may initiate solidification of the slurry 108. For example, these activators may include alkali metal phosphate salts. High alumina cements may include calcium aluminate in an amount ranging from about 15 to about 45% by weight of the weight of the high alumina cement, Class F fly ash in an amount ranging from about 25 to about 45% by weight of the weight of the high alumina cement, and sodium polyphosphate in an amount in the range of about 5 to about 15% by weight of the weight of the high alumina cement. In certain embodiments of the present invention where a cement mixture comprising a phosphate cement is used, a reactive component of the cement mixture (for example the alkali metal phosphate salt) can be used as an activator.

Figures 2A and 2B illustrate cross-sections of well system 100 including activated hardened cement 202 in at least a portion of the annulus 122. In particular, the capsules 110 released activators into at least a portion of cement slurry 108 to form the hardened cement 202. In Figure 2A, the cement slurry is shown flowing in in annulus 122 through casing 116 and in response to at least one signal, the capsules 110 in slurry 108 have released an activator. In the illustrated example, substantially all capsules 110 in annulus 122 have released activators to form the solidified cement 202 along substantially the entire length of annulus 122. Reference is now made to Figure 2B where cement slurry 108 flowed into annulus 122 through casing 116 and which in response to at least one ultrasonic signal, the capsules 110 in the slurry 108 release activators within a specified location 204. In the illustrated example, region or location 204 is adjacent to zone 102. In other words, the capsules 110 adjacent to zone 102 may release activators and form the solidified cement 202 located in region 204. The ultrasonic signal may be localized to the region identified as 204, and in response to at least the localized signal, the solidified cement 204 is formed. In some implementations, an initial amount of cement slurry 108 may be exposed to a ultrasonic signal so that the setting period becomes substantially equal to a time period for the setting cement slurry 108 to flow to location 204. In these examples, cement slurry 108 may be exposed to the ultrasonic signal as slurry 108 including capsules 110 enters casing 116. As the leading edge of cement slurry 108 begins to solidify, fluid flow through annulus 122 becomes more restricted and may possibly cease. Thus, cement slurry 108 may be substantially prevented from flowing to surface 112 through annulus 122. The remaining portion of cement slurry 108 may solidify in annulus 122 behind the leading edge, as illustrated in Figure 2A, or cement slurry 108 may solidify at a later time as illustrated in Figure 2B. In the latter case, the remaining cement slurry 108 may be exposed to ultrasonic signals at a later time to initiate or accelerate the setting process. Figures 3A and 3B illustrate an example of a capsule 110 in Figure 1 in accordance with certain implementations of the present invention. In this implementation, the capsule 110 is spherical, but may have other shapes as discussed below. The capsule 110 is a shell 302 that encapsulates one or more activators 304 as illustrated in Figure 3B. The capsule 110 releases one or more stored activators 304 in response to at least one ultrasonic signal. For example, the capsule 110 may rupture or otherwise form one or more holes in response to at least one ultrasonic signal. The illustrated capsule 110 is for exemplification only and the capsule 110 may include some, none or all of the illustrated elements without deviating from the scope of the present invention. Figures 4A and 4B illustrate example implementations of the capsules 110 during the release of one or more activators. The capsules 110 may release activators by heating one or more parts to form at least one opening, destroying or otherwise removing one or more parts, and/or other processes. The following implementations are for illustrative purposes only and the capsules 110 may release activators by any, all or none of these processes.

Reference is made to Figure 4A where capsule 110 forms an opening around heat developed from ultrasonic signals. For example, the ultrasonic signals may directly heat the membrane of capsule 110 and/or heat the surrounding cement slurry 108 to a temperature above the melting point. The capsule 110 may be a gold shell which, when vibrated at its natural frequency, melts therein at least a portion of the shell to release entrapped activators. In these cases, the heat generated can melt or otherwise deform the shell to form an opening. In addition to metal membranes, the capsule 110 may be made of other materials, such as a polymer. Reference is made to Figure 4B, where the capsule 110 cracks, tears or forms openings in response to ultrasonic signals. For example, the ultrasonic signal may rupture or otherwise destroy portions of the capsule 110. In some implementations, the ultrasound may create defects in the membrane of the capsule and, as a result, create one or more openings as illustrated.

Figures 5 and 6 are flowcharts illustrating example methods 500 and 600 for implementing and manufacturing devices, including one or more activators. The illustrated methods are described with respect to well system 100 in Figure 1, but these methods can be used by any other systems. Furthermore, well system 100 can use other techniques to perform these tasks. Thus, many of the steps in these flowcharts can take place simultaneously and/or in a different order than the one shown. Well system 100 can also use methods with additional steps, fewer steps, and/or different steps as long as the method remains appropriate.

Referring now to Figure 5, method 500 begins with step 502 where the capsules are selected based at least in part on one or more parameters. For example, the capsules 110 and the contained activators may be based at least in part on the components of cement slurry 108. In some implementations, the capsules 110 may be selected based on well conditions (eg, temperature). At step 504, the selected capsules are mixed with a cement slurry. In some examples, the capsules 110 may be mixed with cement slurry 108 when the truck 130 pumps the slurry into annulus 122. In some examples, the capsules 110 may be mixed with dry cement prior to generating cement slurry 108. Then, at step 506, cement slurry including the capsules 110 may be pumped down the well. In some cases, cement slurry 108 including the capsules 110 can be pumped into annulus 122 at a specified rate. One or more ultrasonic signals are transmitted to at least a portion of the well cement slurry at step 508. Again in the example, the transmitter may be lowered into the casing to transmit signals to a portion of the cement slurry 108. In this example, the transmitted signals may activate the capsules 110 near the shoe 132 to solidify the portion of cement slurry 108 as illustrated in Figure 2B. In some cases, the casing 116 can be moved (eg up/down) to help distribute the activators if desired.

Reference is made to Figure 6 where method 600 begins with step 602 where a first emulsification step takes place. For example, a polystyrene dissolved in CH2CI2 where saturated aqueous CH2CI2 can be emulsified using WS-36 (Sorbitan Monooleate). Then, at step 604, the first emulsion can again be emulsified in a second step. In the example, the first emulsion can be subsequently emulsified in a large volume (for example 10 times excess) of a 2% polyvinyl alcohol solution.

Figures 7A-F illustrate an example implementation of the capsules 110 in accordance with the present invention. In this example, the capsules enclose 110 activators and powerful ultrasound can break the capsules to release the activators on command. The illustrated capsules 110 are polystyrene microcapsules that encapsulate aqueous CaCl 2 . However, the capsules can be made of other materials such as ethylene/vinyl acetate copolymer, polymethyl methacrylate and/or others. In some cases, these types of capsules 110 can be formed using a double emulsion technique. For example, this technique may include a polystyrene dissolved in CH2Cl2 where saturated aqueous CaCl2 was emulsified using WS-36 (Sorbitan Monooleate). This emulsion can then be subsequently emulsified in a large volume (e.g. 10 times excess) of a 2% polyvinyl alcohol solution. The double emulsion was stirred and heated to about 30<9>C to drive off and concentrate the polystyrene and finally form liquid-filled microcapsules. To evaluate these capsules, four different cement slurries were tested and the results are graphed in Figures 7C-F. A retarded slurry, a retarded slurry with CaCl2, a retarded slurry with microcapsules and a retarded slurry with microcapsules treated with "sonication" were evaluated. A 20 kHz supersonic horn was used for 10 minutes at 50% power to treat the "sonicated" sample. Composition and results are listed in tables 1-3 below.

The parameters shown including operating conditions are for illustration purposes only. System 100 may use some, all or none of these values without departing from the scope of the invention.

Figure 8 is another example system 100 that directly activates cement slurry 108 using ultrasonic signals. For example, the ultrasonic transducers 802a and 802b may be attached to the exterior of casing 116 and emit ultrasound to sonically activate the cement slurry. By sonic activation of the cement slurry, system 100 can harden the cement on command. For example, system 100 may solidify cement slurry 108 over a period of time in the range of 1 hour to 1 day. The sonic transducers 802 may directly activate cement slurry 108 using one or more different mechanisms responsive to sonic signals. The one or more mechanisms may include modification of chemical properties, release of chemicals, modification of physical properties (eg, particle size), updating of operating conditions (eg, pressure, temperature), and/or other mechanisms responsive to sonic signals. For example, the sonic transducers 802 can reduce particle size in cement slurry 108 and, as a result, increase the surface area. By increasing the surface area, the solidification process can be initiated, accelerated or otherwise activated. Alternatively or in combination, the sonic signals can increase the pressure and/or temperature and, as a result, initiate, accelerate or otherwise activate the solidification process. In some implementations, the ultrasonic transducers may activate the accelerators in cement slurry 108 and/or deactivate cement retarders in cement slurry 108 to harden the cement on command. For example, the ultrasonic signal transducers 802 can generate ultrasonic or acoustic waves to initiate the solidification process in cement slurry 108 through, for example, selective activation of accelerators in cement slurry 108 such as CaCl2 and/or deactivation of cement retarders in cement slurry 108 such as xylose. In some implementations, cement hydration inhibitors (in relatively low concentration) can act to change the surface energy of tricalcium aluminate, silicate and/or other compounds in cement slurry 108 which can make the compounds more hydrophobic. Transducer 802 may ultrasonically agitate cement slurry 108 to reduce the effect of hydrophobic surfactants that may enable the compounds to enter the solution and/or partially hydrate. The signal transducers 802 may generate ultrasonic signals at a frequency substantially corresponding to resonant conditions for inhibitor neutralization. In some implementations, system 100 may perform frequency adjustment to substantially optimize frequency and power combinations for a given geometry and inhibitor chemistry. In these cases, a user of system 100 remotely controls the initiation of cement hydration. In addition, system 100 may initiate an autocatalytic process. For example, the transducers 802 may generate ultrasonic signals that initiate an autocatalytic free radical release that propagates through the cement slurry 108. In these cases, the process may be initiated from a single point. Cement slurry 108 may include additives (eg, free radical dopants) that release free radical species throughout the slurry 108 in response to at least ultrasonic initiation and hydration.

Figures 9A-H show example graphs demonstrating the effect of sonic signals on cement slurries. In these examples, measurements were made on cement slurries that were sonically activated in comparison with cement slurries that were not sonically activated. In particular, ultrasound was used to accelerate the setting of retarded cement slurries. The cement slurries were retarded using the following three retarders: EDTA, a combination of FDP-C742A and EDTA, and a combination of FDP-C742A and component R. Without exposure to ultrasound, cement slurries were pumped between 6.5 and 80 hours. After exposure to 20 kHz of ultrasound, the pumping times for these slurries were reduced by 40-50%. In addition, a control pumping time was run using pure cement with and without exposure to ultrasound. The ultrasound did not appear to affect the pumping times of the pure cement. Based at least in part on these data, ultrasound appears to affect the retarders and, as a result, can accelerate the solidification process.

Reference is made to Figure 9A where graph 910 plots data for cement slurry comprising 1.97 kg/l (class H cement, neat) operated at 48.9°C and 248 bar for 30 minutes. The cement was not exposed to ultrasound. Graph 910 includes a peak 912 indicating that the pumping time was 2 hours and 23 minutes. Reference is now made to Figure 9B where graph 920 shows data for the same cement slurry as graph 910 including exposure to 20 kHz ultrasound for seven minutes. In this experiment, ultrasound was turned off after 5 minutes due to an increase in the temperature of the cement slurry. The cement slurry was exposed for a further two minutes to ultrasound and cooled. Graph 920 including a peak 922 indicates the pumping time to be 2 hours.

Reference is made to Figure 9C where graph 930 plots data for cement slurry comprising 1.97 kg/l (class H cement), 1% EDTA) operated at 48.9°C and 248 bar for 30 minutes. The cement slurry was not exposed to ultrasound. Graph 930 contains a peak 932 indicating the pumping time to be 7 hours and 45 minutes. Reference is made to Figure 9D where graph 940 plots the same data for the same cement slurry as graph 930 including exposure to 20 kHz ultrasound for 7 minutes (5 minutes on, 2 minutes off, 2 minutes on). In this experiment, ultrasound was switched off after 5 minutes as a consequence of the temperature increase in the cement slurry. The cement slurry was exposed to an additional 2 minutes of ultrasound after it had cooled. The pumping time was 4 hours and 15 minutes.

Reference is made to Figure 9E where graph 950 plots data for cement slurry comprising 1.97 kg/l (class G cement), w/ 35% SSA-1,10,4 SSA-1, 1% CFR-3, 0.8% Halad-200,1.5 l/sk Gascon 469, 1.8% FDP-C742A, 1.8% EDTA, 1.141/sk NF-6) with % as bwoc. The operating conditions were 204 °C and 900 bar for 90 minutes. The cement slurry was not exposed to ultrasound. The pumping time was 6 hours and 46 minutes. Reference is made to figure 6 where graph 960 plots data for the same cement slurry as graph 950 including exposure to 20kHz ultrasound for 15 minutes (10 minutes on, 1 minute off, 5 minutes on). In this experiment, ultrasound was turned off after 10 minutes due to an increase in the temperature of the cement slurry. The cement slurry was exposed to an additional 5 minutes of ultrasound and cooled. The pumping time was 3 hours 15 minutes.

Reference is made to figure 9G where graph 970 plots data for cement slurry comprising 1.97 kg/l (class G cement), w/ 35% SSA-1,10,4 SSA-1.1% CFR-3, 0.8% Halad-200.1.5 l/sk Gascon 469.1.8% FDP-C742A, 0.8% component R, 1.141/sk NF-6) with % in bwoc. The operating conditions were 217 C and 900 bar for 90 minutes. The cement slurry was not exposed to ultrasound. The pumping time of 79 hours. Reference is made to figure pH where graph 980 plots data for the same cement slurry as graph 970 including exposure to 20 kHz ultrasound for 15 minutes (5 minute intervals). The pumping time was 50 hours. The present invention is well adapted to achieve the goals and advantages mentioned as well as other inherent ones. The specific embodiments described above are only illustrative in that the invention may be modified and practiced in various equivalent ways as will be obvious to a person of ordinary skill in the field supported by this description. Furthermore, no limitations are intended for details of construction or design shown here, other than those that appear in the following patent claims. It is therefore obvious that the specific, illustrative embodiments shown may be changed or modified and all such variations shall be considered to be within the scope of the present invention. While compositions and methods are described with terms such as "comprehensive", "comprising" or "including" various components or steps, "mainly consisting of" or "consisting of" the various components and steps may also be used. When a numerical range is indicated by lower and upper limits, any number and any range falling within that range shall be deemed specifically described. In particular, all ranges of values (in the form "about a to about b" or equivalently, "from about a to b", or equivalently "from about a-b") described here shall be understood to represent any number and any range within the wider range of values. Furthermore, all designations in the patent claims have their usual, ordinary meaning unless otherwise explicitly and clearly stated by the patentee.

Claims (57)

1. Method of placing a solidifiable mixture in a wellbore, characterized by transmitting a sonic signal in the solidifiable mixture to initiate solidification using a mechanism that is directly responsive to the sonic signal 2. Method in accordance with patent claim 1, characterized in that it comprises treating an underground formation by placing the solidifiable mixture including a capsule in a wellbore, the capsule being used to increase the solidification rate in response to a sonic signal, and transmitting the sonic signaling at least a portion of the curable mixture to release an activator from the capsule, the activator being configured to increase the rate of setting of the curable mixture. 3. Method in accordance with patent claim 2, characterized in that the treatment is cementation and that the hardenable mixture comprises a cement mixture, the capsule encapsulating an activator and the signal being transmitted to release the activator from the encapsulating capsule. 4. Method in accordance with patent claim 1 or 2, characterized in that the hardenable mixture comprises at least one of a cement mixture, a resin mixture, a hardenable sludge, a "conformance" mixture, or a circulation loss mixture. 5. Method according to claim 1, 2, 3 or 2, characterized in that the mechanism includes activation of an activator or deactivation of a retarder, the activated activator being configured to increase the rate of setting of the settable mixture. 6. Method in accordance with any of the preceding patent claims, characterized in that the solidifiable mixture comprises a free radical "dopant" which autocatalytically releases free radicals in response to the sonic signal. 7. Method in accordance with patent claim 6, characterized in that the hardenable mixture includes a polymer additive, the released, autocatalytic free radicals initiating polymerization of at least part of the hardenable mixture. 8. Method in accordance with any of the preceding patent claims, characterized in that the mechanism includes reduction of particle size in the cement slurry. 9. Method according to any one of the preceding claims, characterized in that the mechanism includes increasing at least one pressure or temperature of the curable mixture. 10. Method according to any one of the preceding patent claims, characterized in that the sonic signal is transmitted at a frequency in the range from about 20 Hz to about 2 Mhz. 11. A method according to any one of the preceding claims, characterized by further comprising determining at least one frequency of transmission of the sonic signal, based at least in part on an inhibitor chemistry of the curable mixture. 12. Method in accordance with any one of the preceding patent claims, characterized in that the sonic signal is an ultrasonic signal. 13. Method in accordance with patent claim 12, characterized in that the ultrasonic signal is transmitted at a frequency in the range from approximately 20 to approximately 2 Mhz, or is mainly centered in said range. 14. Method according to any one of patent claims 1 to 11, characterized in that the sonic signal is an acoustic signal. 15. Method in accordance with patent claim 14, characterized in that the acoustic signal is transmitted with a frequency in the range from approximately 20 Hz to approximately 20 kHz. 16. Method according to any one of claims 2 to 15, characterized in that the capsule is sonically activated. 17. Method according to any one of patent claims 2 to 16, characterized in that the capsule comprises a shell which encloses or encapsulates one or more activators. 18. Method in accordance with patent claim 17, characterized in that the shell comprises a sonically responsive polymer. 19. Method according to any one of patent claims 12 to 18, characterized in that the capsule or each of a plurality of capsules comprises a shell selected from the group consisting of polystyrene, ethylene/vinyl acetate, acetate copolymer, polymethyl methacrylate, polyurethanes, polylactic acid, polyvinyl alcohol , polyvinyl acetate, hydrolyzed ethylene/vinyl acetate and copolymers of the aforementioned. 20. Method according to any one of the preceding claims, characterized in that the solidifiable mixture solidifies in the range from about 1 minute to about 24 hours after reacting with one or said activator. 21. A method according to any one of claims 2 to 20, characterized in that a plurality of capsules are mixed with a cement mixture to an activator concentration of from about 0.5% by weight to about 30% by weight of the cement. 22. Method according to any one of the preceding patent claims, characterized in that the hardenable mixture is a cement mixture comprising a hydraulic cement, a base fluid and a retarder. 23. Method in accordance with any one of the preceding patent claims, characterized in that the hardenable mixture is a cement mixture selected from the group consisting of Portland cement, pozzolan cement, high aluminate cement, gypsum cement, silica cement, high alkali cement and sour cement. 24. A method according to any one of claims 2 to 23, characterized in that at least one dimension of said capsule is from about 10 nanometers to about 10,000 micrometers. 25. A method according to any one of claims 2 to 24, characterized in that said or each capsule comprises a spheroid having at least one dimension in the range from about 5 micrometers (u.m) to about 20 u.m. 26. Method according to claim 2 or 3 or any one of claim 5 to 25, characterized in that the activator is selected from the group consisting of sodium hydroxide, sodium carbonate, amine compounds, salts comprising calcium, sodium, magnesium, aluminum and combinations thereof. 27. Method in accordance with patent claims 2 or 3 or any of patent claims 5 to 25, characterized in that the activator is selected from the group consisting of calcium chloride, calcium nitrite, calcium nitrate, sodium chloride, sodium aluminate, sodium silicate, magnesium chloride and combinations thereof. 28. Method in accordance with patent claims 2 or 3 or any of patent claims 5 to 25, characterized in that the activator is selected from the group consisting of triethanolamine, trippropanolamine, triisopropanolamine, diethanolamine and combinations thereof. 29. A mixture for treating a well, comprising a solidifiable mixture, characterized by comprising either: (i) an activator, wherein the activator is released in response to a sonic signal to initiate solidification of the solidifiable mixture, or (ii) a solidification retarder, wherein the setting retarder responds to a sonic signal to accelerate setting of the settable mixture. 30. Mixture in accordance with patent claim 29, characterized in that the hardenable mixture comprises at least one of a cement mixture, a resin mixture, a hardenable sludge, a conformation fluid or a circulation loss mixture. 31. Mixture in accordance with claim 29 or 30, characterized in that the released activator is configured to increase the setting rate of the settable mixture. 32. Mixture according to any one of claims 29 to 31, characterized in that the curable mixture comprises a polymer additive. 33. Mixture in accordance with patent claim 32, characterized in that the polymer additive comprises at least one monomer, a prepolymer, an oligomer or a short-chain polymer which is polymerized in response to the sonic signal. 34. Mixture according to any one of claims 29 to 33, characterized in that the curable mixture comprises a free radical dopant which autocatalytically releases free radicals in response to the sonic signal. 35. Mixture in accordance with patent claim 34, characterized in that the curable mixture includes a polymer additive, the released autocatalytic free radicals initiating polymerization of at least a part of the curable mixture. 36. A mixture according to any one of claims 29 to 35, characterized in that the sonic signal reduces a particle size in the solidifiable mixture. 37. A mixture according to any one of claims 29 to 36, characterized in that the sonic signal reduces at least one of pressure or temperature of the curable mixture. 38. A mixture according to any one of claims 29 to 37, characterized in that a frequency for transmitting the sonic signal is based at least in part on an inhibitor chemistry of the curable mixture. 39. Mixture according to any one of claims 29 to 38, characterized in that the sonic signal comprises an ultrasonic signal. 40. Mixture in accordance with patent claim 39, characterized in that the ultrasonic signal comprises transmitted at a frequency in the range from approximately 20 kHz to approximately 2 MHz. 41. Mixture in accordance with patent claims 29 to 40, characterized in that the sonic signal comprises an acoustic signal. 42. Mixture in accordance with patent claim 41, characterized in that the acoustic signal is transmitted with a frequency in the range from approximately 20 Hz to approximately 20 kHz. 43. Mixture in accordance with patent claims 29 to 48, characterized in that the activator is enclosed in a shell selected from the group consisting of a polystyrene, ethylene/vinyl acetate copolymer, polymethyl methacrylate, polyurethanes, polylactic acid, polyglycolic acid, polyvinyl alcohol, polyvinyl acetate, hydrolyzed ethylene/vinyl acetate and copolymers of these. 44. Mixture in accordance with patent claims 29 to 43, characterized in that the activator is enclosed in a shell which is a sonic responsive polymer. 45. A mixture according to claim 44, characterized in that at least one dimension of the shell is from about 10 nanometers to 10,000 micrometers. 46. A mixture according to claim 44, characterized in that the shell comprises a spheroid with at least one dimension in the range from about 5 micrometers (um) to about 20 um. 47. A mixture according to claims 29 to 46, characterized in that the activator is mixed with the curable mixture at a concentration in the range from about 0.5 to about 30% by weight of the weight of the curable mixture. 48. Mixture in accordance with patent claims 29 to 47, characterized in that the hardenable mixture comprises a hydraulic cement, a base fluid and a retarder. 49. Mixture in accordance with patent claims 29 to 48, characterized in that the hardenable mixture is selected from the group consisting of Portland cement, pozzolan cement, high aluminate cement, gypsum cement, silica cement, highly alkaline cement and sorel cement. 50. A composition according to claims 29 to 49, characterized in that the curable composition sets in a range from about one minute to about 24 hours after reacting with the activator. 51. Mixture in accordance with patent claims 29 to 50, characterized in that the activator is selected from the group consisting of sodium hydroxide, sodium carbonate, amine compounds, salts including calcium, sodium, magnesium, aluminum and combinations thereof. 52. Mixture in accordance with patent claims 29 to 51, characterized in that the activator is selected from the group consisting of calcium chloride, calcium nitrite, calcium nitrate, sodium chloride, sodium aluminate, sodium silicate, magnesium chloride and combinations thereof. 53. Mixture in accordance with patent claims 29 to 52, characterized in that the activator is selected from the group consisting of triethanolamine, trippropanolamine, triisopropanolamine, diethanolamine and combinations thereof. 54. Mixture in accordance with patent claim 29, characterized in that the sonic signal essentially deactivates the setting retarder. 55. A mixture according to claims 29 to 52, characterized in that the settable mixture sets in a range from about one minute to about 24 hours after the set retarder responds to the sonic signal. 56. Mixture in accordance with patent claim 29, 54 or 55, characterized in that the sonic signal comprises an ultrasonic signal. 57. Mixture in accordance with patent claim 56, characterized in that the ultrasonic signal comprises transmitted at a frequency in the range from approximately 20 kHz to approximately 2 MHz.