OA17088A - Set-delayed, cement compositions comprising pumice and associated methods. - Google Patents

Abstract

A variety of methods and compositions are disclosed, including, in one embodiment, a method of cementing in a subterranean formation, comprising: providing a set-delayed cement composition comprising water, pumice, hydrated lime, and a set retarder; activating the set-delayed cement composition; introducing the set-delayed cement composition into a subterranean formation; and allowing the set-delayed cement composition to set in the subterranean formation.

Description

SET-DELAYED CEMENT COMPOSITIONS COMPRISING PUMICE AND ASSOCIATED METHODS

BACKGROUND

Cernent compositions may be used in a variety of subterranean operations. For example, in subterranean well construction, a pipe string (e.g., casing, liners, expandable tubulars, etc.) may be run Into a well bore and cemented in place. The process of cementing the pipe string in place is commonly referred to as ‘primary cementing. In a typical primary cementing method, a cernent composition may be pumped into an annulus between the walls of the well bore and the exterior surface of the pipe string disposed therein. The cernent composition may set in the annular space, thereby forming an annular sheath of hardened, substantially imperméable cernent (i.e., a cernent sheath) that may support and position the pipe string in the well bore and may bond the exterior surface of the pipe string to the subterranean formation. Among other thlngs, the cernent sheath surrounding the pipe string functions to prevent the migration of fluids In the annulus, as well as protecting the pipe string from corrosion. Cernent compositions also may be used In remédiai cementing methods, for example, to seal cracks or holes In pipe strings or cernent sheaths, to seal highly permeable formation zones or fractures, to place a cernent plug, and the like.

A broad variety of cernent compositions hâve been used In subterranean cementing operations. In some Instances, set-delayed cernent compositions hâve been used. Setdelayed cernent compositions are characterized by remaining in a pumpable fluid state for an extended period of time (e.g., at least about 1 day to about 2 weeks or more). When desired for use, the set-delayed cernent compositions should be capable of being activated whereby reasonable compressive strengths are developed. For example, a cernent set accelerator may be added to a set-delayed cernent composition whereby the composition sets into a hardened mass. Among other things, the set-delayed cernent composition may be suitable for use In well bore applications, for example, where It is desired to préparé the cernent composition In advance. This may allow, for example, the cernent composition to be stored prior to its use. In addition, this may allow, for example, the cernent composition to be prepared at a convenient location and then transported to the job site. Accordingly, capital expenditures may be reduced due to a réduction In the need for on-site bulk storage and mixing equipment. This may be particularly useful for offshore cementing operations where space onboard the vessels may be limited.

While set-delayed cernent compositions hâve been developed heretofore, challenges exist with their successful use In subterranean cementing operations. For example, set-delayed cernent compositions prepared with Portland cernent may hâve undesired gélation issues which can limit their use and effectiveness In cementing operations. Other set-delayed compositions that hâve been developed, for example, those comprising hydrated lime and quartz, may be effective in some operations but may hâve limited use at lower températures 1 as they may not develop sufficient compressive strength when used in subterranean formations having lower bottom hole static températures.

SUMMARY

An embodiment of the présent Invention provides a method of cementing In a subterranean formation. The method may comprise providing a set-delayed cernent composition comprising water, pumlce, hydrated lime, and a set retarder. The method may further comprise activating the set-delayed cernent composition. The method may further comprise Introducing the set-delayed cernent composition into a subterranean formation. The method may further comprise allowing the set-delayed cernent composition to set in the subterranean formation.

Another embodiment of the présent Invention provides a method of cementing in a subterranean formation. The method may comprise providing a set-delayed cernent composition comprising water, pumice, hydrated lime, and a set retarder. The method may further comprise storing the set-delayed cernent composition for a period of at least about 1 day. The method may further comprise adding a cernent set accelerator to the set-delayed cernent composition. The method may further comprise introducing the set-delayed cernent composition into a subterranean formation. The method may further comprise allowing the set-delayed cernent composition to set in the subterranean formation.

Another embodiment of the présent invention provides a set-delayed cernent composition that may comprise water, pumice, hydrated lime, and a set retarder. The set-delayed cernent composition may remain In a pumbable fluid state for a time period of at least about 1 day.

The features and advantages of the présent invention wili be readily apparent to those skilled in the art. While numerous changes may be made by those skilled in the art, such changes are within the spirit of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The présent Invention relates to subterranean cementing operations and, more particularly, in certain embodiments, to set-delayed cernent compositions and methods of using setdelayed cernent compositions in subterranean formations.

Embodiments of the set-delayed cernent compositions of the présent invention may generally comprise water, pumice, hydrated lime, and a set retarder. Optionally, the setdelayed cernent compositions may further comprise a dispersant. Advantageously, embodiments of the set-delayed cernent compositions may be capable of remaining in a pumpable fluid state for an extended period of time. For example, the set-delayed cernent compositions may remain In a pumpable fluid state for at least about 1 day or longer.

Advantageously, the set-delayed cernent compositions may develop reasonable compressive strengths after activation at reiatively low températures. While the set-delayed cernent compositions may be suitable for a number of subterranean cementing operations, they may be particularly suitable for use in subterranean formations having reiatively low bottom hole static températures, e.g., températures less than about 200*F or ranging from about 100° F to about 200* F.

The water used in embodiments of the set-delayed cernent compositions of the présent Invention may be from any source provided that It does not contain an excess of compounds that may undesirabiy effect other components in the set-delayed cernent compositions. For example, a set-delayed cernent composition may comprise fresh water or sait water. Sait water generally may include one or more dissolved salts therein and may be saturated or unsaturated as desired for a particular application. Seawater or brines may be suitable for use in embodiments of the présent invention. Further, the water may be présent in an amount sufficient to form a pumpable slurry. in certain embodiments, the water may be présent in the set-delayed cernent composition in an amount in the range of from about 33% to about 200% by weight of the pumice. ln certain embodiments, the water may be présent in the set-delayed cernent compositions in an amount ln the range of from about 35% to about 70% by weight of the pumice. One of ordinary skill in the art with the benefit of this disclosure will recognize the appropriate amount of water for a chosen application.

Embodiments of the set-delayed cernent compositions may comprise pumice. Generally, pumice is a voicanic rock that can exhibit cementitious properties, ln that It may set and harden in the presence of hydrated lime and water. The pumice may also be ground, for example. Generally, the pumice may hâve any particle size distribution as desired for a particular application, ln certain embodiments, the pumice may hâve a mean particle size ln a range of from about 1 micron to about 200 microns. The mean particle size corresponds to d50 values as measured by particle size analyzers such as those manufactured by Maivem Instruments, Worcestershire, United Kingdom. ln spécifie embodiments, the pumice may hâve a mean particle size in a range of from about 1 micron to about 200 micron, from about 5 microns to about 100 microns, or from about 10 micron to about 50 microns, ln one particular embodiment, the pumice may hâve a mean particle size of less than about 15 microns. An example of a suitable pumice Is available from Hess Pumice Products, Inc., Malad, Idaho, as DS-325 lightwelght aggregate, having a particle size of less than about 15 microns. It should be appreclated that particle sizes too small may hâve mixabllity problème while particle sizes too large may not be effectively suspended ln the compositions. One of ordinary skill in the art, with the benefit of this disclosure, should be able to select a particle size for the pumice suitable for use for a chosen application.

Embodiments of the set-delayed cernent compositions may comprise hydrated lime. As used herein, the term “hydrated lime will be understood to mean calcium hydroxide. The 3 hydrated lime may be included in embodiments of the set-delayed cernent compositions, for example, to form a hydraulic composition with the pumice. For example, the hydrated lime may be included ln a pumice-to-hydrated-lime weight ratio of about 10:1 to about 1:1 or 3:1 to about 5:1. Where présent, the hydrated lime may be included in the set-delayed cernent compositions ln an amount in the range of from about 10% to about 100% by weight of the pumice, for example, in some embodiments, the hydrated lime may be présent in an amount ranging between any of and/or Including any of about 10%, about 20%, about 40%, about 60%, about 80%, or about 100% by weight of the pumice. in some embodiments, the cementitious components présent In the set-delayed cernent composition may consist essentially of the pumice and the hydrated lime. For example, the cementitious components may primarily comprise the pumice and the hydrated lime without any additional components (e.g., Portland cernent, fly ash, slag cernent) that hydraulically set in the presence of water. One of ordinary skill ln the art, with the benefit of this disdosure, will recognize the appropriate amount of the hydrated lime to include for a chosen application. Embodiments of the set-delayed cernent compositions may comprise a set retarder. A broad variety of set retardera may be suitable for use in the set-delayed cernent compositions useful in the présent invention. For example, the set retarder may comprise phosphonic acid, phosphonic acid dérivatives, iignosulfonates, salts, organic acids, carboxymethylated hydroxyethylated celluloses, synthetic co- or ter-poiymera comprising sulfonate and carboxylic acid groups, borate compounds, dérivatives thereof, or mixtures thereof. In certain embodiments, the set retardera used in the set-delayed cernent compositions useful in the présent Invention are phosphonic acid dérivatives, such as those described in U.S. Pat. No. 4,676,832, the disdosure of which Is Incorporated herein by reference. Examples of suitable set retardera Include, among othera, phosphonic acid dérivatives available from Halliburton Energy Services, Inc., of Duncan, Oklahoma, as Micro Matrix® cernent retarder. Generafiy, the set retarder may be présent in the set-delayed cernent composition used ln the présent invention in an amount sufficient to delay the setting for a desired time. ln some embodiments, the set retarder may be présent in the set-delayed cernent compositions in an amount In the range of from about 0.01% to about 10% by weight of the pumice. In spécifie embodiments, the set retarder may be présent in an amount ranging between any of and/or including any of about 0.01%, about 0.1%, about 1%, about 2%, about 4%, about 6%, about 8%, or about 10% by weight of the pumice. One of ordinary skili in the art, with the benefit of this disdosure, will recognize the appropriate amount of the set retarder to include for a chosen application.

As previously mentîoned, embodiments of the set-deiayed cernent compositions may optionally comprise a dispersant. Examples of suitable dispersants Include, without limitation, sulfonated-formaldehyde-based dispersants and polycarboxylated ether dispersants. One example of a suitable sulfonated-formaldehyde-based dispersant that 4 may be suitable is a sulfonated acetone formaldéhyde condensate, available from Halliburton Energy Services, Inc., as CFR^w-3 dispersant. One example of a suitable polycarboxylated ether dispersant that may be suitable Is Liquiment® 514L dispersant, available from BASF Corporation, Houston, Texas, that comprises 36% by weight of the polycarboxylated ether in water. While a variety of dispersants may be used in accordance with embodiments of the présent Invention, polycarboxylated ether dispersants may be particulariy suitable for use In some embodiments. Without being limited by theory, it Is believed that polycarboxylated ether dispersants may synergistically Interact with other components of the set-delayed cernent composition. For example, It is believed that the polycarboxylated ether dispersants may react with certain set retardera (e.g., phosphonic acid dérivatives) resulting in formation of a gel that suspends the pumice and hydrated lime in the composition for an extended period of time.

In some embodiments, the dispersant may be induded in the set-delayed cernent compositions In an amount in the range of from about 0.01% to about 5% by weight of the pumice. In spécifie embodiments, the dispersant may be présent in an amount ranging between any of and/or induding any of about 0.01%, about 0.1%, 0.5%, about 1%, about 2%, about 3%, about 4%, or about 5% by weight of the pumice. One of ordinary skill in the art, with the benefit of this disclosure, will recognize the appropriate amount of the dispersant to include for a chosen application.

Other additives suitable for use in subterranean cementing operations also may be induded in embodiments of the set-delayed cernent compositions. Examples of such additives include, but are not limited to, weightîng agents, lightweight additives, gas-generating additives, mechanical-property-enhancing additives, lost-circulation materials, filtrationcontrol additives, fluid-loss-control additives, defoaming agents, foaming agents, thixotropic additives, and combinations thereof. in embodiments, one or more of these additives may be added to the set-delayed cernent composition after storing but prior to placement of the set-delayed cernent composition into a subterranean formation. A peraon having ordinary skill in the art, with the benefit of this disclosure, will readily be able to détermine the type and amount of additive useful for a particular application and desired resuit.

Those of ordinary skill in the art will appreciate that embodiments of the set-delayed cernent compositions of the présent invention generally should hâve a density suitable for a particular application. By way of example, the set-delayed cernent compositions may hâve a density in the range of from about 4 pounds per gallon (Ib/gal) to about 20 Ib/gal. In certain embodiments, the set-delayed cernent compositions may hâve a density in the range of from about 8 Ib/gal to about 17 Ib/gal. Embodiments of the set-delayed cernent compositions may be foamed or unfoamed or may comprise other means to reduce their densities, such as hollow microspheres, low-density elastic beads, or other density-reducing additives known in the art. In embodiments, the density may be reduced after storing the 5

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composition, but prior to placement ln a subterranean formation. Those of ordinary skiîl in the art, with the benefit of this disclosure, will recognize the appropriate density for a particular application.

As previously mentioned, the set-delayed cernent compositions may hâve a delayed set in that they remain in a pumpabfe fluid state for an extended period of time. For example, the set-delayed cernent compositions may remain in a pumpable fluid state for a period of time from about 1 day to about 7 days or more, ln some embodiments, the set-delayed cernent compositions may remain ln a pumpable fluid state for at least about 1 day, about 7 days, about 10 days, about 20 days, about 30 days, about 40 days, about 50 days, about 60 days, or longer. A fluid is considered to be in a pumpable fluid state where the fluid has a consistency of less than 70 Bearden units of consistency (Bc), as measured on a hightemperature high-pressure consistometer at room température (e.g., about 80’F) in accordance with the procedure for determining cernent thickening times set forth in API RP Practice 10B-2, Recommended Practice for Testing Well Cements, First Edition, July 2005. As set forth in Example 4 below, an example composition was prepared that comprlsed pumice, 20% hydrated lime, 1.4% dispersant (Liquiment® 514L), 1.26% set retarder (Micro Matrix® cernent retarder), and 62% water (ail % by weight of pumice). After 45 days of storage at ambient conditions, the example composition was mixed with 6% calcium chloride by weight of the pumice. At 140*F, the example composition had a thickening time (time to 70 Bc) of 2 hours and 36 minutes and developed 50 psi compressive strength in 9 hours and 6 minutes as measured on an Ultrasonic Cernent Analyzer (UCA), available from Fann Instrument Company, Houston, TX, while maintained at 3000 psi. After 48 hours, the sample was crushed and had a compressive strength of 2,240 psi.

When desired for use, embodiments of the set-delayed cernent compositions may be activated (e.g., by combination with a cernent set accelerator) to thereby set into a hardened mass. By way of example, embodiments of the set-delayed cernent compositions may be activated to set to form a hardened mass in a time period in the range of from about 2 hours to about 12 hours. For example, embodiments of the set-delayed cernent compositions may set to form a hardened mass ln a time period ranging between any of and/or including any of about 2 days, about 4 days, about 6 days, about 8 days, about 10 days, or about 12 days. After activation, the set-delayed cernent composition may develop a 24-hour compressive strength in the range of from about 50 psi to about 5000 psi, altematively, from about 100 psi to about 4500 psi, or altematively from about 500 psi to about 4000 psi. ln some embodiments, the set-delayed cernent composition may develop a compressive strength ln 24 hours of at least about 50 psi, at least about 100 psi, at least about 500 psi, or more. The compressive strengths may determined in accordance with API RP 10B-2, Recommended Practice for Testing Well Cements, First Edition, July 2005, using an UCA at 140° F while maintained at 3000 psi.

Embodiments of the présent invention may inciude addition of a cernent set acceierator to the set-delayed cernent compositions. Examples of suitable cernent set accelerators Include, but are not limited to, calcium chioride, triethanoiamine, sodium silicate, zinc formate, calcium acetate, sodium hydroxide, sodium sulfate, and combinations thereof. The cernent set acceierator should be added to embodiments of the set-delayed cernent composition ln an amount sufficient to activate the extended settable composition to set Into a hardened mass. In certain embodiments, the cernent set acceierator may be added to the set-delayed cernent composition ln an amount in the range of about 1% to about 20% by weight of the pumice. ln spécifie embodiments, the cernent set acceierator may be présent In an amount ranging between any of and/or including any of about 1%, about 5%, about 10%, about 15%, or about 20% by weight of the pumice. One of ordinary skili in the art, with the benefit of this disclosure, will recognize the appropriate amount of the cernent set acceierator to inciude for a chosen application.

As will be appreciated by those of ordinary skiil ln the art, embodiments of the set-delayed cernent compositions of the présent Invention may be used ln a variety of subterranean operations, including primary and remédiai cementing. In some embodiments, a setdelayed cernent composition may be provided that comprises water, pumice, hydrated lime, a set retarder, and optionally a dispersant. The set-delayed cernent composition may be introduced Into a subterranean formation and ailowed to set therein. As used herein, Introduclng the set-delayed cernent composition Into a subterranean formation Includes introduction into any portion of the subterranean formation, including, without limitation, Into a well bore drilled into the subterranean formation, into a near well bore région surrounding the well bore, or into both. Embodiments of the présent Invention may further Include activation of the set-delayed cernent composition. The activation of the set-delayed cernent composition may comprise, for example, addition of a cernent set acceierator to the setdelayed cernent composition.

In some embodiments, a set-delayed cernent composition may be provided that comprises water, pumice, hydrated lime, a set retarder, and optionally a dispersant. The set-delayed cernent composition may be stored, for example, in a vessel or other suitable container. The set-delayed cernent composition may be permitted to remain ln storage for a desired time period. For example, the set-delayed cernent composition may remain in storage for a time period of about 1 day or longer. For example, the set-deiayed cernent composition may remain in storage for a time period of about 1 day, about 2 days, about 5 days, about 7 days, about 10 days, about 20 days, about 30 days, about 40 days, about 50 days, about 60 days, or longer, ln some embodiments, the set-delayed cernent composition may remain in storage for a time period in a range of from about 1 day to about 7 days or longer. Thereafter, the set-delayed cernent composition may be activated, for example, by addition of a cernent set accelerator, Introduced into a subterranean formation, and allowed to set therein.

In primary cementing embodiments, for example, embodiments of the set-delayed cernent composition may be introduced into a space between a wall of a well bore and a conduit (e.g., pipe strings, liners) located in the well bore, the well bore penetrating the subterranean formation. The set-delayed cernent composition may be allowed to set to form an annular sheath of hardened cernent in the space between the well bore wall and the conduit. Among other things, the set cernent composition may form a barrier, preventing the migration of fluids in the weil bore. The set cernent composition also may, for example, support the conduit in the well bore.

In remédiai cementing embodiments, a set-delayed cernent composition may be used, for example, In squeeze-cementing operations or in the placement of cernent plugs. By way of example, the set-delayed composition may be placed in a well bore to plug an opening, such as a void or crack, in the formation, in a grave! pack, in the conduit, in the cernent sheath, and/or a microannulus between the cernent sheath and the conduit.

To facilitate a better understanding of the présent invention, the following exemples of certain aspects of some embodiments are given. In no way should the following examples be read to iimit, or define, the entire scope of the invention.

EXAMPLE 1

The following sériés of tests was performed to evaluate the force résistance properties of comparative cernent compositions comprising pumice and hydrated lime. Three different comparative sample settable compositions, designated Samples 1-3, were prepared using pumice (DS-325 lightweight aggregate), hydrated lime, Liquiment® 514L dispersant, and water, as indicated in the table below. After préparation, the samples were placed in an UCA and cured at 140°F and 3,000 psi for 24 hours. The cured cernent was then removed from the UCA and crushed to yieid the compressive strength values provided In Table 1 below.

TABLE 1

Compressive Strength Tests

Sample		1	2	3
Density	Ib/ga!	14.3	14.3	14.3
Pumlce;Llme Wt Ratio		3:1	4:1	5:1
Pumice	9	400	400	400
Lime	g	134	103	100

Dispersant	g	12	4	13
Water	g	196	187	220
24-Hr Crush Strength	psi	2,240	1,960	2,130

Example 1 thus Indicates that cernent compositions that comprise pumice and lime in a weight ratio ranging from 3:1 to 5:1 may deveiop compressive strengths suitable for particular applications.

EXAMPLE 2

A sampie set-delayed cernent composition, designated Sample 4, having a density of 13.3 Ib/gal was prepared that comprised 500 grams of pumice (DS-325 lightwelght aggregate), 100 grams of hydrated lime, 13 grams of Liquiment® 514L dispersant, 24 grams of Micro Matrix® cernent retarder, and 300 grams of water. The rheological properties of the sampie were measured after storing at room température and pressure for periods of 1 day and 6 days. After préparation, the rheological properties of the sample were determined at room température (e.g., about 80’F) using a Model 35A Fann Viscometer and a No. 2 spring, in accordance with the procedure set forth in APi RP Practice 10B-2, Recommended Practice for Testing Well Cements. The results of this test are set forth ln the table below.

TABLE 2

Vlscoslty Tests

Age of Sample (days)	- Fann Readlngs	Yield Point (ib/100 ft2>	Plastic Vlscosit y (centlpo Ise)
£ ( (	0 c c	2 i (	2 C
1	r 6 0	0 C 2 2	2 i i	1 c			84	238
6	2 C C £	* t 1 c	2 2 £	• : £			122	188

Example 2 thus Indicates that set-deiayed cernent compositions that comprise pumice, hydrated lime, a dispersant, a set retarder, and water can remaln fluid after 6 days.

EXAMPLE 3

A sample set-delayed cernent composition, designated Sample 5, having a density of 13.4 Ib/gal was prepared that comprised 500 grams of pumice (DS-325 lightweight aggregate), 100 grams of hydrated lime, 7 grams of Liquiment* 514L dispersant, 6.3 grams of Micro

Matrix® cernent retarder, and 304 grams of water. The rheological properties of the sample were measured after storing at room température and pressure for periods of from 1 day to 19 days. The rheological properties were measured at room température (e.g., about 80’F) using a Model 35A Fann Viscometer and a No. 2 spring, in accordance with the procedure 5 set forth in API RP Practice 10B-2, Recommended Practice for Testing Well Cements. The results of this test are set forth in the table below.

Table 3 Viscosity Tests

	Fann Readings
Age of	;	2
Sample	C	t
(Days)	0	C	C
	i	r K
1	c	C
	ΓΊ 2	c	C
	A	2	d
2	S	£
	8	2	2
	4	2
5	ri 2	£	C
	c	C	€
	4	2
8	4	7
	Ê	C	C
	t	2
12	2	£	C
	C	2	c
	4	r	c
19	r	4	* 4
	€	£

After 7 days, calcium chloride in the amount indicated in Table 4 below was added to a separately prepared sample of the same formulation as above. The sample was then placed In an UCA and the initial setting time, which is the time for the composition to reach a compressive strength of 50 psi while maintained at 3,000 psi was determined in accordance with API RP Practice 10B-2, Recommended Practice for Testing Well Cements. The initial 15 setting time of the sample was also determined without addition of the calcium chloride. The samples with and without the calcium chloride were heated to a température of 140*F In 30 minutes and then maintained at that température throughout the test.

TABLE 4

Compressive Strength Tests

Age of Sample (Days)	Test Température (°F)	CaCI2 (%bywt of Pumice & Lime)	Initial Setting Time (hr:mln)
7	140	0	no set after 4 days
7	140	10	5:11

Example 3 thus Indicates that the set-delayed cernent compositions that comprise pumice, hydrated lime, a dispersant, a set retarder, and water will not set for a period of at least 19 days at ambient température and over 4 days at 140*F. Example 3 further indicates that sample set-delayed cernent compositions may be activated at a desired time by addition of a suitable activator.

EXAMPLE 4

A sample set-delayed cernent composition, designated Sample 6, having a density of 13.4 Ib/gal was prepared that comprised pumice (DS-325 lightweight aggregate), 20% hydrated lime, 1.4% Liqulment® 514L dispersant, 1.26% Micro Matrix® cernent retarder, and 62% of water (ail by weight of pumice, referred to in the table below as *% bwop). After 45 days In storage at ambient conditions, the sample was mixed with 6% calcium chloride. At 140’F, the sample had a thickening time (time to 70 BC) of 2 hours and 36 minutes and an Initial setting time (time to 50 psi) of 9 hours and 6 minutes as measured using an UCA while maintained at 3000 psi. After 48 hours, the sample was crushed with a mechanical press which gave a compressive strength of 2,240 psi. The thickening time and initial setting time were both determined In accordance with API RP Practice 10B-2, Recommended Practice for Testlng Well Cements. The results of this test are set forth In the table below.

TABLE 5

Age of Sampl e (Days)	Test Temperatur e (•F)	Calcium Chlorld e (% bwop)	Thlckenln g Time (hr:mln)	Initial Setting Time (hr:mln )	48 Hr Crush Strengt h (psi)
45	140	6	2:36	9:36	2,240

Example 4 thus indicates that the set-delayed cernent compositions that comprise pumice, hydrated lime, a dispersant, a set retarder, and water will not set for a period of at least 45 days at ambient température. Example 4 further indicates that sample set-delayed cernent compositions may be activated at a desired time by addition of a suitable activator.

EXAMPLE 5

This example was performed to evaluate the abllity of sodium hydroxide and sodium sulfate to actlvate a set-delayed cernent composition that comprised pumice (DS-325 lightweight aggregate), hydrated lime, Liqulment® 514L dispersant, Micro Matrix® cernent retarder, and water. Four sample set-delayed cernent compositions, designated Samples 7-10, were prepared having concentrations of components as Indicated in the table below. The samples were monitored via an UCA. After the samples were placed in the UCA, the pressure was Increased to 3,000 psi, and the température was increased to 100°F over a 15-minute time period and held for the duration of the test. A portion of the slurry was retalned and poured into a plastic cyîinder to monltor the slurry behavior at room température and pressure. These procedures were repeated for all samples.

Sample 7 was monitored for 72 hours over which time no strength was developed and the slurry was still pourabie when removed from the UCA. The portion kept at room température and pressure was likewise still pourabie after 72 hours.

Sample 8 was prepared using the same slurry design as Sample 7 except that sodium hydroxide was added as an activator. The sodium hydroxide was added In solid form directly to the mixing jar that contained the prepared sample. As can be seen from Table 6, Sample 8, reached 50 psi of compressive strength at 16 hours and 36 minutes. The strength contlnued to build, reaching a maximum of 1,300 psi, when the test was stopped at 72 hours. The cured cernent was removed from the UCA and crushed with a mechanical press which gave a compressive strength of 969 psi. The portion kept at room température and pressure was crushed after 7 days resulting In a compressive strength of 143 psi.

Sample 9 was prepared using the same slurry design as Sample 8 except that sodium sulfate was added as an activator. The sodium sulfate was added in solid form directly to the mixing jar that contained the prepared slurry. Sample 9 reached 50 psi of compressive strength at 67 hours and 29 minutes. The strength continued to build, slowly, reaching a maximum of 78 psi, when the test was stopped at 72 hours. The cured cernent was removed from the UCA and crushed with a mechanical press which gave a compressive strength of 68.9 psi. The portion kept at room température and pressure was stiil too soft to be crushed after 7 days.

Sample 10 was prepared using the same slurry design as Sample 8 except that equai amounts of sodium hydroxide and sodium sulfate were added as an activator. The sodium hydroxide and sodium sulfate were added In soiid form directly to the mixing jar that contained the prepared slurry. Sample 10 reached 50 psi of compressive strength at 22 hours and 40 minutes. The strength contlnued to build, reaching a maximum of 900 psi, when the test was stopped at 72 hours. The cured cernent was removed from the UCA and crushed with a mechanical press which gave a compressive strength of 786 psi. The portion kept at room température and pressure was crushed after 7 days resulting in a compressive strength of 47.9 psi.

The results of these tests are set forth in the table below. The abbreviation *% bwop refers to the percent of the component by weight of the pumice. The abbreviation gal/sk refers to 5 gallons of the component per 46-pound sack of the pumice. The abbreviation RTP refers to room température and pressure.

TABLE 6

Sample		7	8	9	10
Denslty	Ib/gal	13.38	13.38	13.38	13.38
Water	% bwop	61.97	63.60	64.62	64.11
Pumice	% bwop	100	100	100	100
Hydrated Lima	% bwop	20	20	20	20
Dispersant	gal/sk	0.07	0.07	0.07	0.07
Set Retarder	% bwop	0.06	0.06	0.06	0.06
Sodium Hydroxide	% . bwop	—	4	—	2
Sodium Sulfate	% bwop	—	—	4	2
UCA
Temp/Press	F/Psi	100/3000	100/3000	100/3000	100/3000
Initial Set (50 psi)	hnmin	>78	16:36	67:29	22:40
Final Set (100 psi)	hr.min	—	21:08	—	32:44
24 Hr Comp. Strength	psi	—	138.74	—	59.60
48 Hr Comp. Strength	psi	—	711.35	—	331.48
72 Hr Comp. Strength	psi	—	1300	78	900
72 Hr Crus h Strength (UCA)	psi	—	969	68.90	786
7*Day Crush Strength (RTP)	psi	—	143.20	0.00	47.90

Example 5 thus Indicates that sodium hydroxide, sodium sulfate, and combinations of the two can activate the set-delayed cernent compositions, but to varying degrees. The testing showed that both sodium hydroxide and combinations of sodium hydroxide with sodium sulfate activated the cernent compositions to an acceptable level. When compared to the non-activated composition, sodium sulfate activated the cernent compositions, but much less so than the sodium hydroxide or combination of sodium hydroxide and sodium sulfate.

It should be understood that the compositions and methods are described In terms of “comprising, containing, or “including various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components and steps. Moreover, the Indefinite articles a or “an, as used In the daims, are defined herein to mean one or more than one of the element that it Introduces.

For the sake of brevity, only certain ranges are explidtly disclosed herein. However, ranges from any lower limit may be combined with any upper limit to recite a range not explidtly redted, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explidtly redted, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explidtly redted. Additionally, whenever a numerlcal range with a lower limit and an upper limit ls disclosed, any number and any Included range falling within the range are specifically disclosed. In particular, every range of values (of the form, from about a to about b,“ or, equivalently, “from approximately a to b, or, equivalently, from approximately a-b“) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values even if not explidtly redted. Thus, every point or individual value may serve as Its own lower or upper limit combined with any other point or Individual value or any other lower or upper limit, to redte a range not explidtly redted.

Therefore, the présent Invention is well adapted to attaln the ends and advantages mentioned as well as those that are Inhérent therein. The particular embodiments disclosed above are illustrative only, as the présent Invention may be modified and practiced In different but équivalent manners apparent to those skilled In the art having the benefit of the teachlngs herein. Although individual embodiments are discussed, the Invention covers ail combinations of ail those embodiments. Furthermore, no limitations are Intended to the details of construction or design herein shown, other than as described in the daims below. Also, the terms in the daims hâve their plain, ordinary meaning unless otherwise explidtly and clearly defined by the patentée. It ls therefore évident that the particular Illustrative embodiments disclosed above may be altered or modified and ail such variations are considered within the scope and splrit of the présent Invention. If there is any conflict In the usages of a word or term In this spécification and one or more patent(s) or other documents that may be Incorporated herein by référencé, the définitions that are consistent with this spécification should be adopted.

Claims (22)

1. What is claimed Is:

   1. A method of cementing in a subterranean formation, comprising:

   providing a set-delayed cernent composition comprising water, pumice, hydrated lime, and a set retarder;

   5 activa tin g the set-delayed cernent composition;

   Introducing the set-delayed cernent composition into a subterranean formation; and allowing the set-delayed cernent composition to set in the subterranean formation.

   10
2. 2. The method of claim 1 wherein the pumice has a mean particle size in a range of about 1 micron to about 200 microns.
3. 3. The method of claim 1 wherein the pumice and the hydrated lime are présent In a weight ratio of pumice to hydrated lime of about 10:1 to about 1:1.
4. 4. The method of claim 1 wherein the set retarder comprises at least one retarder

   15 selected from the group consisting of a phosphonic acid, a phosphonic acid dérivative, a lignosulfonate, a sait, an organic acid, a carboxymethylated hydroxyethylated cellulose, a synthetic co- or ter-polymer comprising sulfonate and carboxylic acid groups, a borate compound, and any mixture thereof.
5. 5. The method of claim 1 wherein the set-delayed cernent composition further 20 comprises a dispersant
6. 6. The method of claim 5 wherein the dispersant comprises at least one dispersant selected from the group consisting of a sulfonated-formaldehyde-based dispersant, a polycarboxylated ether dispersant, and any combination thereof.
7. 7. The method of claim 1 wherein the set retarder comprises a phosphonic acid

   25 dérivative, and wherein the set-delayed cernent composition further comprises a polycarboxylated ether dispersant.
8. 8. The method of claim 7 wherein the set-delayed cernent comprise has a pumlceto-hydrated-lime weight ratio of about 3:1 to about 5:1, wherein set retarder is présent in an amount of about 0.01% to about 2% by weight of the pumice, and wherein the polycarboxylated

   30 ether dispersant Is présent in an amount of about 0.01% to about 2% by weight of the pumice.
9. 9. The method of claim 1 wherein the set-delayed cernent composition further comprises at least one additive selected from the group consisting of a weighting agent, a lightweight additive, a gas-generating additive, a mechanical-property-enhancing additive, a lost-circulation material, a filtration-control additive, a fluld-loss-control additive, a defoaming agent, a foaming agent, a thixotropic additive, and any combination thereof.
10. 10. The method of claim 1 wherein the set-delayed cernent composition remains in a pumpable fluid state for a time period of at least about 7 days prior to the activating.
11. 11. The method of claim 1 wherein the set-delayed cernent composition remains in a pumpable fluid state for a time period of at least about 30 days prior to the activating.
12. 12. The method of claim 1 wherein the activating comprises adding a cernent set accelerator to the set-delayed cernent composition.
13. 13. The method of claim 1 wherein the set-deiayed cernent composition sets to develop a 24-hour compressive strength of at least about 50 psi as measured using an Ultrasonic Cernent Analyzer at 140T while maintained at 3,000 psi.
14. 14. The method of claim 1 wherein the set-delayed cernent composition is introduced into a well bore penetrating the subterranean formation, the well bore having a bottom-hole s ta tic température of less than about 200°F.
15. 15. The method of claim 1 wherein the set-delayed cernent composition is introduced into an annulus between a wall of a well bore and a conduit disposed in the well bore.
16. 16. A method of cementing in a subterranean formation, comprising:

    providing a set-delayed cernent composition comprising water, pumice, hydrated lime, and a set retarder;

    storing the set-delayed cernent composition for a period of at least about 1 day, adding a cernent set accelerator to the set-deiayed cernent composition; introducing the set-delayed cernent composition into a subterranean formation; and allowing the set-delayed cernent composition to set in the subterranean formation.
17. 17. The method of claim 16 wherein the pumice and the hydrated lime are présent in a weight ratio of pumice to hydrated lime of about 10:1 to about 1:1.
18. 18. The method of claim 16 wherein the set retarder comprises a phosphonic acid dérivative, and wherein the set-delayed cernent composition further comprises a polycarboxylated ether dispersant.

    1 ’l I
19. 19. The method of claim 16 wherein the set-delayed cernent composition further comprises a dispersant.
20. 20. The method of claim 16 wherein the set-delayed cernent composition is stored for a time period of at least about 30 days.

    5
21. 21. A set-delayed cernent composition comprising water;

    pumlce;

    hydrated lime; and a set retarder,

    10 wherein the set-delayed cernent composition will remain In a pumbable fluid state for a time period of at least about 1 day.
22. 22. The method of claim 21 the set-delayed cernent composition further comprises a dispersant