OA17464A

OA17464A - Cement slurry compositions and methods.

Info

Publication number: OA17464A
Application number: OA1201500337
Authority: OA
Inventors: Clara Carelli; Jesse C. Lee; Syed A. Ali
Original assignee: Prad Research And Development Limited
Priority date: 2013-02-26
Filing date: 2014-02-26
Publication date: 2016-12-30

Abstract

A cement slurry composition is described as having cement, water, and organic polymeric particles. The composition also includes non-ionic surfactants, which may contain ethoxylate groups or contain both ethoxylate groups and propyxlate groups in the hydrophilic part. The non-ionic surfactant acts to disperse the hydrophobic polymeric particles in the slurry and to reduce or prevent foaming. The cement slurry composition is prepared and then pumped into the subterranean well and placed in a zone of the subterranean well. Time is then allowed for the cement slurry composition to set into a solid mass in the zone.

Description

CEMENT SLURRY COMPOSITIONS AND METHODS

BACKGROUND

The statements in this section merely provide background information related to the présent disclosure and may not constitute prior art.

The présent disclosure relates generally to compositions and methods for treating or completing a subterranean well having a borehole. More particularly, the disclosure relates to cernent slurry compositions for cementing a subterranean well and, in the alternative, methods for subterranean well complétions and\or cementing a subterranean well having a borehole. The présent disclosure also relates to a method of preparing a cernent slurry composition having polymer particles as additives and/or reducing foam in such cernent slurry composition.

In a typical well cementing operation, a cernent slurry is prepared at the surface and then pumped into the subterranean well through a liner or casing to fill the annulus between the casing and borehole wall. Once the slurry sets, the cernent may provide a number of functions, including providing zonal isolation and ségrégation, corrosion control, and structural support. A properly prepared slurry and set cernent form a strong, nearly imperméable seal around the casing.

Generally, the cernent slurry should hâve relatively low viscosity to facilitate pumping and maintain effectively constant rheological properties during both préparation at the surface and delivery into the well and the target zone. Assuming the cernent slurry is properly prepared and delivered to the target zone, the properties of the set cernent will dépend primarily on the components of the slurry and the additives included in the slurry composition. Ideally, the properly placed cernent will develop high compressive strength in a minimum of time.

In recent years, organic polymeric particles hâve been employed as additives in the cernent slurry to achieve or enhance certain cernent properties. Generally, the addition of the polymeric particles leads to improved joining of the slurry constituents, which may help achieve increased strength and high durability characteristics, among other things. The hydrophobie character of the particles may, however, also présent some undesirable issues. In particular, mixability and foaming problems may be observed in the polymer-modified cernent slurry.

In the field, cernent slurries are often prepared using the continuous mixing method, also known as mixing on-the-fly. Solid blends are mixed with water and liquid additives by using a jet mixer.

The jet mixer generates a regulated flow of solids that créâtes a void to draw a dry powder component (due to a venturi effect) into the mix. Unfortunately, the drawing action also draws and entrains air in the slurry. If allowed to stabilize, excess air in the slurry can lead to densely packed air bubbles collecting and then forming at the slurry surface, i.e., foaming. Excessive entrained air and foam can adversely affect the slurry design. For example, it can alter the slurry composition and performance, including deviating from optimal slurry density or increasing slurry viscosity. Such conditions may also cause pumping problems and inefficiencies. Operators attempt to mechanically remove as much of the entrained air from the slurry before pumping, usually through further mixing. However, for slurries contaîning a large amount of hydrophobie polymer particles, such de-aerating efforts often fall short of removing enough ofthe entrained air from the slurry to avoid slurry quality issues or pumping problems. To mitigate foaming problems in cernent slurry préparations, different traditional measures are available. Anti-foam and defoamer additives may be added to the slurry to prevent or minimize foaming. Separator equipment may also be used in conjunction with traditional slurry mixers to mechanically remove the entrained air from the slurry. For example, the SIurryAirSeparator device from Schlumberger Ltd. employs a hydrocyclone mechanism to separate and remove entrained air from the cernent slurry. As another option, the slurry may be transferred to a large tank for batch mixing. Much of the remaining entrained air may be removed from the slurry. While any of the aforementioned options may be effective in reducing entrained air and foam in the slurry, the employment of these options is not always feasible. For example, operating time and cost associated with using additional equipment or additives may not be acceptable or the equipment may not be readily available in some field locations. Also, some of these measures hâve proven less than satisfactory in reducing entrained air and foam under certain operating conditions. Thus, there remains a need for methods and\or compositions that reduce, eliminate, or prevent air entrainment and foaming conditions in cernent slurries for wellbore complétions.

SUMMARY

The présent disclosure is directed to cernent slurry compositions having polymeric particles. Embodiments relate to methods of preventing or controlling foaming in cernent slurry préparations or cernent operations. Further embodiments relate to methods for cementing or completing a subterranean well comprising a borehole.

In one aspect, a cernent slurry composition is provided having cernent, water, and organic polymeric additives (such as hydrophobie organic polymer particles like rubber particles). The composition also includes non-ionic surfactants. In various embodiments, the non-ionic surfactant is a non-ionic surfactant contaîning ethoxylate groups, non-ionic surfactants contaîning both ethoxylate groups and propyxlate groups, alkoxylates, including alkoxylates containing proplylene oxides, and alkoxylates containing butylène oxide.

In another aspect, a method is described for cementing a subterranean well comprising a borehole. The method entails preparing a cernent slurry composition comprised of components including cernent, water, polymer particles, and a non-ionic surfactant and pumping the cernent slurry composition into the subterranean well and placing the composition in a zone of the subterranean well. Time is then allowed for the cernent slurry composition to set into a solid mass in the zone.

In another aspect, a method is described for reducing foam génération in a cernent slurry composition having hydrophobie organic polymer particles therein for introduction into a subterranean well. The method includes preparing a dry blend including cernent and organic polymer particles, preparing a water solution, and adding a non-ionic surfactant into the water solution. A continuous mixing method is then employed to mix the dry blend in the water solution, whereby the non-ionic surfactant acts to disperse the polymer particles in the solution and to reduce foaming.

BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments may be understood with the appended drawings.

FIG. 1 is a graphical illustration displaying contact angle measurements for various aqueous solutions containing different concentrations of non-ionic surfactants;

FIG. 2 is a graphical illustration displaying the relative volume increase over time for various aqueous solutions after mixing; and

FIGS. 3 shows photographs of a water solution containing rubber particles.

DETAILED DESCRIPTION

At the outset, it should be noted that in the development of any such actual embodiment, numerous implémentation - spécifie decisions must be made to achieve the developer’s spécifie goals, such as compliance with system related and business related constraints, which will vary from one implémentation to another. Moreover, it will be appreciated that such a development effort might be complex and time consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. In addition, the cernent slurry composition used/disclosed herein can also comprise some components other than those cited. In the summary and this detailed description, each numerical value should be read once as modified by the term “about” (unless already expressly so modified), and then read again as not so modified unless otherwise indicated in context. Also, in the summary and this detailed description, it should be understood that a concentration range listed or described as being useful, suitable, or the like, is intended that any and every concentration within the range, including the end points, is to be considered as having been stated. For example, a “range of from 1 to 10” is to be read as indicating each and every possible number along the continuum between about 1 and about 10. Thus, even if spécifie data points within the range, or even no data points within the range, are explicitly identified or refer to only a few spécifie points, it is to be understood that inventors appreciate and understand that any and ail data points within the range are to be considered to hâve been specified, and that inventors possessed knowledge of the entire range and ail points within the range.

As described herein, cernent slurry compositions (and methods of préparations) are provided in which organic polymeric particles and non-ionic surfactants are included as additives. The cernent slurry compositions include a suitable amount of cernent and water to make up the base slurry composition, with particular considération for an optimum balance of mechanical strength in the set cernent and idéal viscosity and quality of the slurry. The organic polymeric particles are provided to achieve or enhance a desired property in the slurry or ultimately, in the set cernent. The non-ionic surfactants are provided to reduce or eliminate entrained air and foaming which would otherwise be encouraged due to the presence of the largely hydrophobie organic polymeric particles.

As used herein in the context of alleviating entrained air or foam génération issues in the cernent slurry, the term “ reduce” or “reducing” also means to eliminate, prevent, minimize, or otherwise mitigate the presence or formation of entrained air or foam in the slurry. In accordance with the présent disclosure, methods are described that may address the issue by causing entrained air or foam to dissipate or escape from the slurry and/or prevent and discourage formation or accumulation by impacting the conditions that may encourage such formation or accumulation, for example. In respect to foaming, the described methods and compositions may be characterized as incorporating de-foaming or anti-foaming tendencies, or both.

In preferred embodiments, the cernent slurry composition generally comprises about 10% to 50% by weight cernent or cementious material and about 5% to about 40% by weight organic polymer particles. Further, in these preferred embodiments, the cernent slurry composition comprises about 0.05% to about 0.5% by weight non-ionic surfactant. In yet further compositions, particularly those with increasing amounts of additives (including hydrophobie organic polymer particles), the amount of non-ionic surfactant in the cernent slurry composition may be as high as about 5% by weight. In other preferred compositions, particularly those with minimum amounts of hydrophobie polymer particles and other additives, the amount of nonionic surfactant may be as low as about 0.005% by weight.

In a method of cementing a well bore, a cernent slurry composition is first prepared at the surface. Préparation of the cernent slurry composition preferably entails preparing a dry blend of ail the solids including the polymeric particles and a wet blend that includes fresh water and the nonionic surfactant. More additives may be included in the blends as generally known in the art and/or required by the particular cementing operation and wellbore conditions. The dry blend is then added to the wet blend in a standard mixing procedure, using, for example, a jet mixer in a single pass operation and at standard mixing speed and time to sufficiently incorporate ail the solids into the mixture. In suitable préparations, the mixing speed was maintained at about 4000 rpm for about 2 minutes. At the end of two minutes, no foaming was observed in the cernent slurry.

After mixing, the cernent slurry composition may be pumped into the well bore. The cernent slurry is typically delivered into the wellbore, filling the annulus between the drilled hole and the casing string. In place, the cernent slurry is allowed to cure and harden. Once set, the cernent attains the mechanical properties intended of the design, including high strength. The set cernent also provides an imperméable seal about the casing.

The slurry compositions described herein may employ any one of the types of cernent traditionally used for well complétions. These include the more commonly used Portland cernent that is produced from limestone and either clay or shale. Most preferably, the cernent will meet the chemical and requirements of the American Petroleum Institute and conform with one of the API cernent classifications. In any event, it should be understood that the type and formulation of the cernent used in an application will dépend on several factors, including the conditions expected downhole and the spécifie purposes or objectives of the cementing operation.

The addition of polymeric particles or fibers to cernent slurries has been employed in the prior art to achieve or enhance certain properties in cernent slurry or set cernent. In general examples, the addition of the polymers enhances the joining of the various slurry constituents and improves the mechanical and durability characteristics of the set cernent. The présent description deals primarily with organic polymeric particles. For example, in U.S. Patent Applic. Publ. US 2012/0312535, latex particles are described as being used in the design of self healing or self repairing cernent Systems. These cernent Systems can adapt to compensate for changes or faults in the physical structure of the cernent. In further examples, organic polymer particles hâve been used as additives in cernent slurries to achieve higher flexural strength and toughness, or to improve vibration damping, or to create a seal in the slurry that blocks gas migrations.

Generally, the methods and compositions described herein may employ a variety of hydrophobie particles to achieve a particular purpose or property, and then select a non-ionic surfactant to include in the slurry composition to address potential issues brought on by the sélection of hydrophobie particles. In preferred embodiments described herein, organic polymer particles are employed, which hâve been observed to be largely hydrophobie. In selecting a surfactant to join the hydrophobie particles in the slurry mix, considération include whether the surfactant will be stable in the slurry and whether it might negatively impact the performance of the organic polymer particles and/or the cernent slurry composition. In addition to the use of rubber particles described herein, methods and compositions according to the présent disclosure may employ some of following organic particles: poly(acrylic); poly(acrylonitrile); poly(acrylamide); maleic anhydride polymers; Polyamides; Polyimides; polycarbonates; Polymers made from diene monomers; saturated and unsaturated polymers containing ester functionality in the main polymer chain, such as poly(ethylene terephthalate) (PET); polyurethanes’Poly(propylene glycol); Fluorocarbon polymers; Polyethylene, polypropylene, their copolymers; Polystyrène; Poly(vinyl acetal); Poly(Vinyl) polymers; Poly(Vinylidene) Chlorides; Poly(vinyl acetate); Poly(Vinyl Ether) and poly(Ketone); Gilsonite; Graphite; Coals; and Wax. In certain preferred compositions, the amount of hydrophobie organic polymer particles is roughly 25% by weight of solid blend, which is relatively high, and in further embodiments, may be about 35% by weight of solid blend.

As discussed above, the presence of a large amount of organic polymer particles in the cernent slurry can lead to foaming issues. The hydrophobie nature of the organic polymer particles tends to stabilize the interfaces between air and the surfaces of the polymer particles, which, in time, causes a transformation of the entrained air and air bubbles into stable foam. In the field, it becomes impérative to alleviate this foam condition prior to introduction of the cernent slurry into the well. In accordance with the présent description, non-ionic surfactants are also added to the cernent slurry to help reduce the amount of entrained air in the polymer-modified slurry and alleviate foaming conditions.

Surfactants are organic compounds that contain both hydrophobie groups (the tails) and hydrophilic groups (the heads). Surfactants diffuse in water and adsorb at interfaces between air and water or oil and water. The insoluble hydrophobie tail may extend out of the bulk water phase, e.g., into the oil phase, while the water soluble head remains in the water phase. The alignment of the surfactants at the surface modifies the surface properties of water at the water\oil or water\oil interface. The class of surfactants selected and employed in the presently described compositions is a non-ionic surfactant, which is characterized by a hydrophobie group or head that does not contain a net charge. In the bulk aqueous phase, surfactants form aggregates characterized by a hydrophobie group or tail that form the core and hydrophilic heads that typically surround the core and contact the surrounding liquid. The hydrophiliclipophilic balance or HLB value of the surfactant is a measure of the degree to which the surfactant is hydrophilic or liphophilic, as determined by the relative sizes of the hydrophilic groups and hydrophobie groups.

Generally, selected non-ionic surfactants are soluble in water and exhibit chemical stability in the cernent slurry composition ( i.e., very high pH and strong ionic strength). Use ofthe selected surfactant in the cernent slurry composition will also promote wettability of hydrophobie particles and a low foam génération or good defoaming effect, combined with dispersion of the hydrophobie particles in the solution. Preferably, as shown further below, the non-ionic surfactant selected contains both ethoxylate and propoxylate groups in the hydrophilic part. Other suitable non-ionic surfactants include fatty alcohol alkoxylates that contain moles of propylene oxide or butylène oxide. This class non-ionic surfactants offer increased wettability results with a defoaming effect, when the température of application is above their cloud point.

Applicants hâve established that when such non-surfactants are used as cernent slurry additives in conjunction with hydrophobie organic polymer particles, the presence of foam in the cernent slurry after mixing is substantially reduced. In accordance with the présent disclosure, selected nonionic surfactants are added to the cernent slurry composition and, when mixed, increase the surface tension between water and air (or other types of gases), thereby, destabilizing foam (de-foamer) or preventing the formation of foam (anti-foam). The surfactant tendency to de-foam will dépend on several parameters: surfactant chemistry and structure; ratio between hydrophobie and hydrophilic part (generally, higher hydrophobicity means lesser foaming tendency); surfactant quantity; and the rate of absorption on a surface.

Moreover, without the addition of the non-ionic surfactants, air bubbles would stabilized by the hydrophobie particle surface and accumulate between the particles. This would lead to a stable aggregation of particles and air bubbles, which, among other things, alter cernent slurry density spécifications and prevent proper mixing of the organic polymer particles. The selected nonsurfactants act as a wetting agent that effectively reduces the surface tension between the hydrophobie particles and water. This subsequently reduces the amount of air trapped at the particle surface and promûtes the dispersion of the hydrophobie particles in water. This dispersion improves the mixability of the cernent slurry containing the polymeric particles, and also reduces the slurry’s tendency to retain entrained air. As a resuit, the presence of foam in the slurry during préparation is reduced and the cernent slurry may be pumped into the well without further deaerating techniques.

The concentration of surfactant added in the cernent slurry composition is dépendent on the slurry formulation. More particularly, the preferred surfactant concentration will be largely dépendent on the amount of hydrophobie particles added to the composition and the surface area presented by the particles. Greater amounts and larger surface areas will warrant higher concentrations of surfactant to address mixability issues. It is noted that a given concentration of smaller particles in a cernent slurry will présent a greater total surface area than the same concentration made up of larger particles in the same cernent slurry, and thus, require a higher concentration of surfactant. In one sense, methods and compositions according to the présent disclosure allow for the use of not only greater concentrations of hydrophobie organic polymers in the slurry, but a greater number of polymers, which may be independently advantageous. In certain preferred compositions, the amount of hydrophobie particles is roughly 25% by weight of solid blend, which is relatively high, but in some cases, this number can reach 35%.

Thus, in one aspect, the présent disclosure provides methods of cementing and cernent slurry préparation that allow higher concentrations of hydrophobie particles to be added to the slurry without encountering mixability and foaming issues. The inclusion of increased concentrations of hydrophobie particles will impart désirable or enhanced properties on the cernent slurry or set cernent that would not hâve been previously attainable. For example, with increased concentrations of certain polymeric particles, the cernent slurry would swell more and achieve relatively greater volume, and be lighter, more flexible, elastic, lighter - ail désirable properties. These improved properties would not be achieved, however, if slurry mixability were an issue.

It is well known to those skilled in the relevant art that a variety of other components and additives may be included in the cernent slurry compositions. These include fluid loss additives, set retarding agents, dispersing agents, lightweight extenders, and the like. Slurry compositions described or experimented in this disclosure reveal some of these additives (see e.g., Tables 1, 2 and 3 below). The inclusion of these additives and their effect on the non-ionic surfactant, the hydrophobie particles, and the cernent slurry, in general, may be a relevant considération in the sélection of the types and amounts of non-ionic surfactants for the cernent slurry composition.

To commence a preferred method of cementing or well completion, according to the présent teachings, a solids or dry blend of cernent and additives is prepared. The cernent may be one of the various types in accordance with the API classes and suitable for the cementing application and with the various additives intended. In this embodiment, the additives include organic polymer particles, such as rubber particles, that hâve been selected to increase the flexural strength and ductility in the set cernent. An aqueous solution is also prepared beginning with fresh water at an amount required for a suitable slurry composition and including one or more additives. In one embodiment, the additive mixed into the water is a non-ionic surfactant such as an octylpehenol ethoxylate (Triton X-45 or Triton X-102 from Dow Chemical Co. in Houston, Texas) or an ethoxylate\propoxylate (Tregitol minfoam 2X from Dow Chemical Co.). The dry blend, containing ail the solid additives is added to the water solution using a jet 5 mixer, for example, to make the desired cernent slurry. For more précision control, the blends may be batch mixed by circulating in a large tank and using a batch mixer.

As with most cernent slurry préparations, the goal ofthe mixing process is to obtain a consistent slurry with the proper amount of additives and water, and at the target density. The optimum cement-water ratio is generally a balance between achieving maximum strength at complété 10 hydration and having sufficient water volume to lower the viscosity of the slurry to pumpable

Ievels. The viscosity must be reduced to facilitate pumping the cernent slurry through the long narrow annulus of the wellbore.

Table 1 présents the components of a cernent slurry composition in accordance with one embodiment. The slurry contains a cernent additive to prevent annular migration of gas into the 15 cernent slurry during critical hydration period. The cernent additive is a suspension of polymer microgels, which form an imperméable filter cake that blocks gas migration. In this preferred composition, the non-ionic surfactant is an alkoxylate surfactant.

Table 1: Cernent Slurry Composition

Job Type	Casi	Depth	6000	TVD	6000
	ng			feet		feet
BHST	150		BHCT	115	BHP	3500
	degF			deg		psi
				F
Starting	80		Time	00:3	Heatin	1.05
Temp.	degF		to	3	g Rate	degF/m
			Temp.	hr:m		in
				m
Starting	450		Time	00:3	Schedu	9.5-3
Pressure	psi		to	3	le
			Pressu	hr:m
			re	m
Compositi
on
Slurry	15.74	Yield	1.12	Mix	3.76
Density	Ib/gal		ft3/sk	Flui	gal/sk

	55.0	Porosi	45.0 %	Slurr	FUTUR
Solid Vol.	%	ty		y	-G
Fraction				type

Code	KJîohcértt< t ration^	'-T^îlBteîisse'W'isi
Cernent		100lbof	Blend	2.61
Blend		BLEND		g/cm3
Fresh	2.92		Base Fluid
Water	gal/sk
Gas	0.589		Additive
migration	gal/sk
control
additive
Anti-foam	0.050		Antifoam
agent	gal/sk
Liquid	0.100		Dispersant
dispersant	gal/sk
Non-ionic	0.100
surfactant	gal/sk

EXAMPLES

It should be recognized that the examples below are provided to aid in a general understanding of the présent teachings. The examples should not be construed so as to limit the scope and application of such teaching to the content of the examples. It is noted that rubber particles were selected as the organic polymer particles in some of the examples and the experiments partly because rubber particles are frequently used as an additive in cernent slurries for well complétions and those skilled in the relevant art are likely to be familiar with the usage. In any 10 case, the sélection of rubber particles is provided to facilitate description only, and, the présent description’s focus on such use should not be deemed limiting of the proposed concepts and teachings. The proposed compositions and methods are also applicable to cernent slurry compositions employing other hydrophobie polymer particles to achieve or enhance certain properties in the slurry or set cernent.

The experiments were generally set out to show the effect of different surfactants on the wettability of rubber particles in water solutions. For these experiments, several non-ionic surfactants were selected for inclusion in a cernent slurry composition. Each of the selected surfactants is a product made commercially available by the Dow Chemical Company in

Houston, Texas. The nonionic surfactants include the following: Triton-X45, Triton X-102 and Tergitol MinFoam 2X. The characteristics of these products are reported in Table 1. The first two surfactants are octylphenol ethoxylate molécules which differ by the size of the hydrophilic head: Triton x-45 contains 4.5 moles of ethyleneoxide (EO) while 12 EO moles are présent in

Triton X-102. As a resuit, the two surfactants hâve a different hydrophilic-liphophilic balance:

the HLB value is -10 for Triton X-45 while it is -14 for Triton X-102. The third surfactant has a different chemistry and contains both ethoxylate and propoxylate groups in the hydrophilic part.

As reported in the Table 2, the non-ionic surfactant Tergitol MinFoam 2x présents an intermediate HLB value (~12) and a much lower CMC (24 μΜ).

Table 2: Properties of Three Non-lonic Surfactants Investigated

y Surfactant	Triton X-45	Triton X-102	Tergito I MinFoa m
Chemistry	Octylphe nol Ethoxyla te EO moles: 4.5	Octylph enol Ethoxyl ate EO moles: 12	Ethoxy late Propox y late
HLB	10	14	12
CMC (μΜ)	136	267	24
Surface Tension (dynes/cm ) 1% in water at 25 degC	29	36	21

Example 1:

The aim of a first experiment was to evaluate the effect of the selected surfactants on wettability, i.e., on the wettability of a surface of a polymer particle. For each selected surfactant, several water solutions each containing different amounts of the surfactant were provided, including a first control solution that contained 0% surfactant concentration. The contact angle for each solution was measured using a Tracker tensiometer from Teclis. Because the measurement of contact angles on powders présents some experimental difficulties, contact angle measurements were carried out on rubber bands.

The results obtained are provided in the graph of Figure. 1, where the average measured contact angle is plotted as a function of the surfactant weight concentration in water for the different solutions tested. As shown, the value of the contact angle for a water solution without surfactant is 110 degrees. This measurement for the first solution confirms the poor wettability of the polymer surface. For the water solutions containing a concentration of one of the surfactants, wettability in respect to the rubber surface is considerably improved. As îllustrated by Figure 1, the contact angle decreases as the amount of surfactant in the solution is increased from 0.01% to 0.04% by weight. At 0.04% concentration, the contact angle for each solution is reduced to the neighborhood of about 25 degrees.

The results of this experiment show that the addition of the non-ionic surfactants to the water solutions improves the wettability of the water solution in respect to a rubber surface. The experimental results suggest, therefore, that the inclusion of the non-ionic surfactants to a cernent slurry composition that incorporate rubber particles will improve the wettablity of the water solution-rubber particle interfaces.

Example 2:

To evaluate the degree to which air is entrained by the selected surfactants during mixing, a sériés of foaming tests were conducted. A Warring blender was used to mix 200 mL of water solutions containing two different concentrations of surfactants, 0.04% and 0.1%. To reproduce the same mixing speeds used in standard API procedures for cernent slurries, the solutions were first mixed at 4000 révolutions per minutes (rpm) for 35 seconds and subsequently at 12000 rpm for the same period of time. After mixing, the volume of each of the solutions was measured as a function of time to détermine the quantity of air bubbles generated during mixing and retained in the solution.

On the graph of Figure 2, the ratio between the volume measured after mixing, Vaft_er._mixing, and the initial volume, V_o, is plotted as a function of time for solutions containing 0.04% of surfactants. For each of the three surfactants tested, the ratio V_after-mixingA/o is highest right after mixing, at t=0, and then generally decreases with time. This suggests that air bubbles are présent in the solutions after mixing and that an initial foam is generated, which results in an increase in the volume of the solution. The graphs indicate further that the ratio V_afte_r.mixing/Vo generally stabilizes after an initial time period, meaning that air bubbles collapse and the foam dissipâtes.

Figure 2 suggests that, for the surfactant Tergitol MinFoam, the amount of air entrained in the solution is less of a problem as the initial volume, V_o, is relatively low and more importantly, the solution returns to initial volume after only a few minutes. That is the air bubbles in the solution collapses soon after mixing and the foam generated at mixing dissipâtes relatively quickly. In contrast, the solution with Triton X-102 appears to generate quite a bit more air bubbles during mixing and tends to maintain the bubbles more so than the other solution. In fact, this solution maintains a volume increase of more than 40% even after 20 minutes.

Water solutions were then provided with higher concentrations (0.1%) of the same surfactants and mixed as before. At t=0, the amount of foam observed in each of the water solution having the Triton surfactants was higher than as observed at the lower concentration (0.04%). For the solution containing Tergitol MinFoam atthe higher concentration, the amount of foam observed was comparable to the amount observed in the solution containing the lower concentration of the non-ionic surfactant. For each of the solutions having the higher concentration of surfactant, the rate at which the volume of solution decreased with time corresponded well with what was observed at the lower concentration. In other words, more foam is generated initially, but the foam dissipâtes in the same manner as observed for solutions with the lower concentration of surfactant.

Example 3:

The purpose of a further experiment was to détermine the effect of the addition of the surfactant on the dispersion of rubber particles in water, and on the mixability of a cernent slurry. Figure 3 provides two depictions of a column of a water solution incorporating additives in the form of hydrophobie rubber particles. The first depiction A, on the left, shows the water solution exhibiting two clearly distinguishable phases: a rubber particle phase and a water phase. In the second depiction B, to the left of the first, the hydrophobie rubber particles hâve been mixed directly in a water solution containing 0.04% of Tergitol MinFoam. In clear contrast to the first solution without the surfactants, a single phase is observed indicating good, homogeneous dispersion of the polymeric particles in the water solution. This dispersion remained stable for more than 48 hours.

This example establishes, therefore, that the addition of the selected non-ionic surfactants renders the hydrophobie rubber particles to readily disperse in the water solution. This suggests, as well, that the addition the non-ionic surfactants in cernent slurry incorporating hydrophobie polymer particles will encourage dispersion of the polymer particles in the solution and good mixability of the cernent slurry composition.

Example 4:

In order to détermine the effect of the presence of the surfactant on the mixability of a cernent slurry, a slurry design containing rubber particles was studied. In a preliminary base test, the slurry was mixed following the laboratory procedure. The dry blend, containing ail the solid additives including an antifoam additive, was added to the liquid phase while mixing at 4000 rpm and the time required to fully incorporate the solids was measured. More than 5 minutes were required in this case.

The, a nonionic surfactant, Tergitol MinFoam, was added to the water solution at a concentration of about 0.1% by weight. Also, the antifoam additive was removed from the formulation, to isolate possible entrainment of air caused by the surfactant. After the new design was mixed following the same procedure, the mixed solution was observed to be without foam. The time required to incorporate the solid was about 2 minutes in this case, which is considerably a shorter period that what was required in the first case. This establishes that the addition of the non-ionic surfactant improves the mixability of the cernent slurry and as compared to use of the antifoam additive, is more effective in penetrating foam génération.

Table 3: Slurry Design Comprising Rubber Particles

DRY PHASE 'Jf'·	(total = 657.8 g)	SVF= 55.0 %
Code		Concentration		Mass
				(g/600mL)
		Blend Total = 657.8 g
G	34.7	BVOB 366.54
cernent
Rubber	24.0	% BVOB	95.04
Additive	26.3	BVOB	65.07
1		%
Additive	15.0	% BVOB	131.18

2 WET PHASE ... _ _r f ,	(total = 269.3 g )
·<-.· Code . * ... V	Concentration - ·. ri] j.èab .. *f ¹ s JpA	MassA’· Y- /'b (^brnL) r
Antifoam	4.44 L/tonne VBWOC	1.63
Cernent dispersant	1.00 L/tonne VBWOC	0.45
FRESH.WATER	of 407.40 L/tonne Blend	267.2

BVOB: By Volume Of Blend - VBWOC: Volume by weight of Cernent

Although various embodiments hâve been described within respect to enabling disclosures, it is to be understood the dîsclosed embodiments are not limiting. Variations and modifications that would occur to one of skill in the art upon reading the spécification are also within the scope of 5 the disclosure, which is defined in the appended claims.

What is claimed is:

Claims

What is claimed is:

1. A cernent slurry composition comprising :

cernent;

water;

organic polymer additives; and a non-ionic surfactant.
2. The cernent slurry composition of claim 1, wherein the organic polymer additives are organic polymer particles and wherein the non-ionic surfactant has a hydrophilic group that contains ethoxylate groups and propoxylate groups.
3. The cernent slurry composition of claim 1, wherein the organic polymer additives are organic polymer particles and wherein the non-ionic surfactant is an octylphenol ethoxylate.
4. The cernent slurry composition of claim 3, wherein the non-ionic surfactant contain between about 4.5 moles to 12 moles of ethyleneoxide.
5. The cernent slurry composition of claim 3, wherein the hlb value of the non-ionic surfactant is between about 10 and about 14.
6. The cernent slurry composition of claim 1, wherein the organic polymer additives are rubber particles and the non-ionic surfactant contains ethoxylate groups and has an hlb value between about 10 and 14.
7. The cernent slurry composition of claim 1, wherein the non-ionic surfactant is selected from the group of non-ionic surfactants consisting of: non-ionic surfactant containing ethoxylate groups; non-ionic surfactants containing both ethoxylate groups and propyxlate groups; alkoxylates containing propylene oxides; and alkoylates containing butylène oxide.
8. The cernent slurry composition of claim 1, wherein the organic polymer additives are rubber particles.
9. The cernent slurry composition of claim 1, further comprising:

an anti-foam agent; and a dispersant.
10. The cernent slurry composition of claim 1, wherein the organic polymer additives are présent at a concentration of between about 5% to about 40% by weight and the non-ionic surfactant is présent at a concentration of between about 0.005% to about 5% by weight.
11. The cernent slurry composition of claim 10, wherein the non-ionic surfactant is présent at a concentration of between about 0.05% to about 0.5% weight and the cernent is présent at a concentration of between about 10%to about 50% by weight.
12. A method of cementing a subterranean well comprising a borehole, comprising: preparing a cernent slurry composition comprised of components including cernent, water, polymer particles, and a non-ionic surfactant;

pumping the cernent slurry composition into the subterranean well and placing the composition in a zone of the subterranean well; and allowing time for the cernent slurry composition to set into a solid mass in the zone.
13. The method of claim 12, wherein the non-ionic surfactant includes non-ionic surfactants containing ethoxylate groups and propyxlate groups in the hydrophilic group.
14. The method of claim 12, wherein preparing the cernent slurry composition includes, preparing a dry blend containing the cernent and organic polymer particles, preparing a wet blend containing the water and the non-ionic surfactant, and mixing the dry blend and wet blend at a cernent to water ratio suitable to make a base slurry.
15. The method of claim 14, wherein preparing the cernent slurry composition includes employing a jet mixer to mix the dry blend and the liquid blend in continuous mixing mode.
16. The method of claim 12, wherein the polymer particles are rubber particles and the non-ionic surfactant contains ethoxylate groups.
17. The method of claim 12, further comprising, prior to preparing the cernent slurry composition, providing a non-ionic surfactant selected from the group of non-ionic surfactants consisting of: non-ionic surfactant containing ethoxylate groups; non-ionic surfactants containing both ethoxylate groups and propyxlate groups; and combinations thereof.
18. The method of claim 12, wherein preparing the slurry composition includes providing amounts of the cernent, polymer particles, and non-ionic surfactant to produce a cernent slurry composition having between about 5% to about 40% by weight of the polymer particles and between about 0.05% to about 0.5% by weight of the non-ionic surfactant.
19. A method of reducing foam génération in a cernent slurry composition having hydrophobie organic polymer particles therein for introduction into a subterranean well, the method comprising:

preparing a dry blend including cernent and organic polymer particles;

preparing a water solution;

adding a non-ionic surfactant into the water solution; and using a continuous mixing method to mix the dry blend into the water solution, whereby the non-ionic surfactant acts to disperse the polymer particles in the solution and to reduce foaming.
20. The method of claim 19, wherein the polymer particles are rubber particles and the non-ionic surfactant contains both ethoxylate groups and propyxylate groups in the hydrophilic part, the non-ionic surfactant being added to constitute between about 0.05% to about 0.5% by weight non-surfactant in the cernent slurry composition.

ABSTRACT