CA1054358A - Sand control method employing asphaltenes - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
This invention relates to a method for treating wells completed in subterranean formations which contain unconsolidated sand particles, so as to form a permeable barrier which will permit the flow of liquids therethrough while restraining the flow of the unconsolidated sand particles into the well bore. The method comprises saturating sand adjacent the well bore to be treated with petroleum having a high asphaltic content and optionally thereafter contacting the asphaltic petroleum with a solvent capable of solubilizing non-asphaltic fractions of the petroleum and precipitating or causing deposition of the asphal-tic or bituminous portions of the petroleum. A heated fluid such as steam is thereafter injected into the formation to cause solidification of the asphaltic materials which effectively binds the sand grains together to form a porous mass which will effectively restrain the movement of sand particles in the well bore upon subsequently placing the well on production. Suitable hydrocarbon materials for causing precipitation of the asphaltic or bituminous portions of the petroleum include liquid paraffinic hydrocarbons such as butane, pentane, or hexane, N-methyl-2-pyrrolidone and furfurel. Steam or a mixture of steam and non-condensable gas such as nitrogen, or mixture of steam and air are then injected into the formation to dehydrate and otherwise solidify the precipitated asphaltic material.

Description

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~AC~GROUMD OF ~-E INVENTION
Field of the Invention This invention pertains to a method for treating wells pene-trated and completed in subterranean ea-rth formations, and more pa-rti-cularly to a method for treating a petroleum containing formation in the immediate vicinity of the well so as to stabilize unconsolidated sand and prevent their migration in-to or away from the well. Still more -particularly, this invention pertains to a method for treating such wells with granular materials saturated with bitumen or bituminous or asphaltic petroleum, contacting the material with a low molecular weight asphaltic or paraffinic hydrocarbon or N-methyl-2-pyrrolidone or furfural to cause precipitation of asphal-tg and then introducing steam to solidify the t bitumen and bind the sand grains together. ; ~ -Prior Art and _ackg~_und Recovery of formation fluid such as petroleum from a subter-ranean formation is frequently difficult when the su~terranean formation is comprised of one or more incompetent or unconsolidated sand layers ~ ;
or zones. The sand particles in the incompetent or unconsolidated sand zone move or migrate into the well bore during recovery of formation fluids from that zone, or sand particles move away from the well during injection of secondary or tertiary recovery fluids into the formation.
`l In the instance of recovering the fluid from the formation, the movement of sand into the well bore can cause the well to cease production of fluids therefrom. Also, small sand particles can plug sm~ll openings and porous masses formed clround the well bore for the purpose of re-straining the flow of sand, such as screens or slotted liners which are frequently placed in wells for thi6 purpose. Not only can fluid pro-duction be reduced or even stopped altogether~ if sand particles flow through the well to the surface~ considerable mechanical problems can 30 result fron passage of abrasive sand pa~ticles throuc~h pumps and other mechanical devices.

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~ 5~358 Many techniques have been described in the prior art for pre-venting or decreasing the flow of s~nd into well in a course of petroleum production, including the use of sand screens, fil-ters, perforated or slotted liners, etc. around the well. These prior art attempts have been successful in some limited instances, but have not al~ays been entirely satisfactory for a number o:F reasons. Mechanical devices usually restrain only the larger particle sand and are not completely effective for the purpose of restraining or preventing the flow of fine particles from the formation into the well and ultimately to the surface. Further-. . .
10 more, the devices interfere with various -types of completions and work over operations.
Recently, there have been introduced into the market place by numerous oil field companies, chemical compositions which bond -the sand ~',?, grains together with a resinous plastic material to form a permeable mass which effectively restrains the flow of sand particles from the formation. mese methods involve injecting into a sand pack around a ,.~, :, well bore, a polymerizable, resinous material, which is later caused to polymerize so as to consolidate forma-tion sand or sand packed around the well for that purpose, to form the desired permeable barrier.
.~ ' , 20 Numerous difficulties have been encountered in commercial applica-tion and use of this technique, including the difficul-ty of achieving the even polymerization of the resinous material to the degree necessary to consolid~te the sand pa~ticles while still main-taining the necessary permeability so tha-t pe-troleum or other fluid may pass -therethrough.
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FurthermLre, the resinous materials are expensive. Recently, many tertiary recovery techniques involving the in~ection of steam or other fluids into -the formation for -the purpose of mobilizing viscous petro-leum, and this has imposed a still greater burden on sand consolidation techniques, and has particularly caused problemsi with the plastic con 30 solidation techniques which are sensitive to the high temperature, high , , .

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pH aqueous fluids freguently employed in such processes. The resinous materials are frequently dissolved or degraded by contact with the hot alkaline fluids used in tertiary recovery processes.
In view of the foregoing discussion, it can be appreciated that there is a substantial, unfulfilled need for a sand control method capable of preventing the flow of ~
unconsolidated sand particles into a well bore during periods ~ -of oil recovery or away rom a well bore during periods of 10 injection of fluids thereinto. More particularly, there i.s a ~ -need for inexpensive, reliable method of consolidating sand .9 in a formation having an appreciable quantity of unconsolidated sand/ which will result in the formation of a .~! permeable mass that will not be adversely affected by -;j 15 subsequent contact with high temperature, alkaline fluid such I as steam or caustic. ~`~
`',9 By the method of the present invention one is able to treat underground formations so as to effect the solidation of granular materials such as sand or gravel into a permeable mass which will effectively restrain the movement of unconsolidated sand particles, which permeable mass will not be appreciably degraded by subsequent contac-t with hot alkaline fluids such as steam and/or caustic, and generally avoid many of the disadvantages of prior art methods, both mechanical and chemical.
SUMMARY OF THE INVENTION
This invention comprises a method of treating a subterranean unconsolidated sand in petroleum-containing forrnations penetrated by at least one well, said well being in fluid communication with a subterranean formation, for the ,~ .

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1~5~358 . purpose of forming a permeable barrier around the WPll to restrain the movement of sand particles while permitting the ~ :
passage of petroleum therethrough, comprising:
a. introducing a predetermined quantity of 5 granular material whose particle size is from 10-80 mesh, ;:
into the well bore adjacent to the ormation; `~
b. introducing bituminous petroleum into the granular material;
. c. introducing an asphalt precipitating solvent selected from the group consisting of parafinic hydrocarbons having from 3-10 carbon atoms, furfural, N-methyl-2- :
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~ pyrrolidone, and mixtures thereof; and `1~ d. introducing a heated fluid into the granular ;, material at a temperature of at least 250~F to solidify the ~;j 15 precipitated solvent.
Z~ In another e~bodiment, the prbsent invention comprises a method of treating a subterranean, asphaltic ~i bituminous petroleum-containing formation, which formation contains unconsolidated sand, said formation being penetrated `"
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by at least one well in fluid communication with the -~ subterranean formation, for the purpose of forming a sand ~ restraining permeable barrier, comprising~
,.~! a. introducing an asphalt-precipitating solvent ~ :
selected from the group consisting of parafinic hydrocarbons having from 3-10 carbon atoms, furfural, N-methyl-2-pyrrolidone and mixtures thereof; and b. introducing a heating fluid into the formation to heat the formation contacted by the asphaltic precipitating solvent, to solidify the asphalt on the sand ~ :
grains, so that a barrier is formed around the well bore. The ., ~
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:,, ~ S~358 heated gaseous fluid may be steam, air, nitrogen and mixtures thereof at temperatures of at least 250F.
.; We have discovered that a permeable mass may be ., formed, which permeable mass is relatively insensitive to thermal fluids and can be employed in connection with thermal recovery processes, involving the precipitation of asphaltic :~
material from asphaltic petroleum such as bituminous . petroleum, onto sand grains located around the well bore by introduction of a suitable asphalt precipitating ~olvent into the vicinity of the well bore, after which a hot fluid such as steam is introduced to volatilize the solvent and other ' volatile fractions : . - -' , :, , ;
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. , ! ' ' ' . . ' , ,~ ,. ' ~ 10~4358 existing in the vicinity of the well bore and harden the asphaltic material to fonm a permeable, competent mass, bonding the sand grains together. In some application such as, for example, tar scmd deposits, naturally occurring unconsolidated sand and naturally occurring bitumin-ous petroleum may be utilized as the reactants. In other applications, the well bore may be enlarged and suitable sand or other granular material packed into the well bore around the production tubing~ The sand is then saturated with asphaltic or bituminouis petroleum by several means. m e asphalt precipitating solvent is -then introduced into the mixture of sand and asphaltic petroleum which causes deposition or pre- ~
cipitation of the asphaltic material onto the sand grainO Steam is ~ -then introduced into the zone to volatilize certain fractions remaining and to solidify the asphalt or bitumen so as to effectively bind the sand grains together. Suitable solvents for causing deposition of :?
- the asphaltic material include liquid aliphatic or paraffinic hydro-carbons such as pentane, hexane, etc., as well as N-me-thyl-2-pyrrolidone or furfural. The steam which is introduced into the precipita-ted asphalt and sand zone may be saturated or super heated, and optionally I may contain a non-condensable gas such as nitrogen or air to aid in `1 20 maintaining the desired permeability. The permeable solid thus formed iæ mechanically stable~ permits petroleum or other ~ormation fluids to flow therethrough~ and resists the de-trimental ef~ect of hot alkaline fluids which may be employed in sub equent oil recovery operations.
i BRIEF DESCRIPTION OF THE DRAWING
The attached drawing illustrates a well in a -tar sand deposit being æubjected to the method of our invention for forming a sand restraining, permPIable maæs around -the well bore.

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''"''' ' ~(~543S8 D~AILED DESCRIPTION OF THE INVENIION AND DESCRIPlION
; OF THE PREFERRED EMBODIMENTS
Briefly, the process of our invention comprises the folloT~ing steps, which will be described more fully below:
1. Positioning the sand in the well bore and 2. Saturating the sand with bituminous, asphaltic petroleum

3. Introduction of the asphalt precipitating solvent into :; :
the sand-bitumen mass, and

4. In-troduction of steam into -the bitumen-sand mass to cause `~ 10 solidification of the bitumen or asphaltic material to bind the sand grains together. , I. Plac~in~ the sand in -the well bore According to one aspect of our invention, the sand naturally occurring in the formation, such as for example, in a tar sand deposit, ~ :
~ may be utillzed for the sand in the formation of the sand restraining, e permeable mass according to the process of our invention. Accordingly, ~: ,. . . . .
one embodi~ent of the process of our invention involves simply intro-ducing an asphaltic or bituminous petroleum into an unconsolidated sand naturally occurring in the formation *o s~tura-te or essentially saturate the same with asphaltic or bituminous petroleum.
In many applications of the process of our invention, the subterranean formation does not contain adequate sand for use in the formation of the permeable barrier, or else ~he sand particle size or . ,~ , .
o-ther characteristics are not suitable for use in the formation of the barrier. In those cases it is necessary to introduce sand into the 'J~ formation for the ~Irpose of forming the permeable barrier.
There are several methods for placing the granular material adjacent the formation in which the sand restraining permeable mass is ::
to be formed. In one embodiment of the process of our invention, a minor amount of the formation adjacent the well to be treated is re-' moved by washing with water or other suitable fluid or by under-reaming ;: :

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to form a small cavity in the immediate vicinity of the well bore. After a suitable amount of material has been removed the-refrom, the tubing string or other well hardware is placed in the well~ and sand or gravel is placed inrto the well bore. One suitable method for accomplishing this is to form a slurry of the granular material in water or some other suitable fluid and pump the slurry into the well bore.
The above described procedure may better be understood by reference to the at-tached figure, in which tubing 1 having perforations nea-r the lower end thereof 2 is contained in well casing 3. The forma-tion material is removed adjacent the petroleum forma-tion to form a cavity 4 which extends outward a small distance from the well bore.
~ . . , ; The granular material is slurried in fluid; for example, the sand m~y be slurried in water or water containing other agents, and iniected into the annular space 5 between tubing 1 and casing 3O The slurry then passes through the bottom of the annular space, and then through slots - 2 into the production well bore where it is pumped to the surface of ~ -~
~- the earth through the tubing. m e granular material fîlters against the formation and also against the perforations 2 in the production tubing 1, forming a closely packed mass 6 which consists essentia1ly of the granular material packed tightly together. This process is continued until the ~ass of granular material e~tends to a point above the top of the perforations 2 and preferably some distance thereabove so that if any shrinkage occurs in subsequent treatment steps, the -cavity adjacent perforations 2 will still be completely filled with granular material.
If the sand restraining permeable mass is to be formed from sand or other granular material other than naturally occurring into the ~ormation, the optimum results are obtained at the sand particles size meet certain specific requirements. The sand or other granular ma-terial ; 30 should be selected frc~l the broad range of from about 10 to about 80 . . , :-' ; , : ', - . , , , ,, : , : : ~ .
, , l~S4~358 mesh, and preferably should be closely spaced within that broad range - so that the larger particle sizes utilized are no more than approximately twice the smalles-t particle sizes employed. For example, sand in the range of 10 to 20 mesh, or 20 to 40 mesh, or 40 to 80 mesh, may be i utilized effectively. The reason for this optim~m size is that sand particles coarser than about 10 mesh when bonded together according to the process to be described in detail below~ result in the formation of a permeable mass whose low channels or pore sizes are so great that fine sand particles can move freely -therethrough in the production well.
Very fine sand particles, i.e. those particles finer than about 80 - mesh, are unsuitable because the resultan-t barrier had insufficient ~ -~
permeability to permit the flow of formation fluids -therethrough. From this discussion it can be apprecia-ted that the type of sand present in the formation which the permeable barrier is to restrain the movement ;
of will to some degree influence the especially preferred particle size of the sand to be introduced into -the formation. Thus if very fine ~ , sand is present in the formation, -then the best result will be attained using sand within the finer range, i.e. from about 40 to about 80 mesh.
Si~ilarly, higher production rates can safely be attained in formations ~ 20 whose naturally occurring sand is relatively coarse by means of using - the coarser sand grains within the specified range, such as for example ~':J 10 to 20 mesh or 20 to 40 mesh sand.
:, II. Introduction of -the Asphaltic or Bituminous Petroleum Into the Sand j According to one aspect of our invention, the asphaltic or -i bituminous petroleum naturally occurring in a formation may be utilized as the source of the asphaltic material to form the sand restraining permeable mass. That is to say, if the naturally occurring formation petroleum is highly asphaltic or bituminous, this m~y be u-tilized as a i part or all of the asphaltic petroleum or formation of the permeable mass. In some instances it is not necessary to add any additional , : , , , :, ., . , "
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;', . , ~, ~f~59~3S~3 asphaltic petroleum, whereas in others it may be necessary to increase the asphaltic petroleum saturation within this portion of the formation im~fedia-tely adjacent to the well to be treated, so that a stable barrier may be for~ed.
When it is desirable to enlarge the cavity and introduce sand rather -than use naturally oacurring formation sand, it will generally be necessary to also introduce the asphaltic or bituminous petroleum.
It should be realized that asphaltic or bituminous petroleum is generally , .
very viscous, and so ordinarily cannot be simply pumped into the sand pack. The viscosity of bituminous petroleum such as is found in tar sand deposits, for example, is in the range of millions of centipoise at formation tem~ferature. The viscosity-temperature relationship of such 1 petroleum is exceedingly sharp, however, and the viscosity of tar sand J material drops to a value of only a few centipoise at about 300F.
Accordingly, one method of introducing the bitumin~us petroleum into the , sand pack is simply to heat the petroleum to a -temperature of at least 200F and preferably around 300F, so as to make the bituminous petro-leum pumpable, and introduce the hot bituminous petroleum into the sand pack. It is preferable to preheat the sand pack to a similar temperature, so that the petroleum will not cool too rapidly, and thus the sand pack may be saturated uniformly into -the desired depth away from -the -~f well bore. Ihe sand pack may ba conveniently preheated by passing a i heated fluid ~uch as steam through the sand pack prior to introduction , of a heated bituminous pe-troleum into the sand pack.
Another method for coating the granular material with bitu-minous petroleum involves the formulation of an oil-in-water em~lsion which has a much lower viscosity than the petroleum itself. The desired emulsion may be formed by mixing a quantity of bituminous petroleum with water, the ratio of oil to water being from about 1.0 to about .01 and preferably about .10 The formulation of the emulsion : ~, , . .,. :

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is aided by inclusion of a small arnount of an alkalinity agent such as sodi~m hydroxide in the water. Generally from about .01 to about 1 p~rcent by weight sodium hydroxide is satisfactory for this purpose.
After the bituminous petroleum and water emulsion has been formulated, it may easily be pumped down the tubing and/or annular : space between the tubing and casing, into the granular material adjacent -to the perfora-tions in the production tubing. The sand pack should be throughly sa-turated with the bitumen and water emulsion. An acid such as hydrochloric acid or sulfuric acid may then be introduced into the ~;~ 10 saturated sand pac]c to "brea]c" the emulsion or resolve it into its separate phases. The volume of acid needed to treat the emulsion- -saturated sand pack will generally be from about 1 percent to about 50 ~; .
percent of the volume of emulsion presen-t. The concentration of acid may be from about 1 percent to about 10 percent by weight. When the ;~ acid contacts the emulsion and resolves i-t in-to its phases, the viscous - bituminous petroleum deposits on the sand grains, and the water phase ~` may easily be displaced out of the pack either into the formation or into the well bore and produced to -the surface of the earth :- .
Still another method for saturating -the sand pack with bitu~
minous petroleum comprises forming a solution of the bituminous petroleum and a suitable solvent such as benzene, toluene and naphtha so as to form a low viscosity solution, and then pump the solution into the sand pack through -the tubing or annular space or both. A suitable gas such as air~ nitrogen or carbon dioxide or natural gas may then be passed through the sand or gravel pack to vaporize the solvent, leaving the viscous petroleum deposited on the sand or gravel. The vaporization -~ ~nay be accelerated if an inner gas such as nitrogen is hea-ted to a -temperature well above the boil.ing point of the solvent prior to passing the gas through the sand pack.

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11~5~3~8 III. sphalt Precipitating Solvent Injection After the asphaltic or bituminous pe:troleum has been placed in the pore space of the sand or granular material pack adjacent the well bore, a solvent capable of solubilizing the non-asphaltic or non-bituminous fraction of the petroleum, and causing precipitation or ~i deposition of the asphal-tic or bituminous fraction of the petroleum on the granular material grains should be introduced into the formation.
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The solvent may be a low molecular weight hydrocarbon, preferably a paraffinic hydrocarbon having from three to ten carbon atcms such as , .
; 10 pentane or hexane. The paraffinic hydrocarbon should be introduced into the fo~mation under temperature and pressure condi-tions which will result in it entering the sand pack in a liquid form. Accordingly, the temperature should be below about 250 and preferably about 150, in order to insure that it is essentially all in the liquid phase of the temperature existing in the sand pack being treated. In deeper deposits, which can tolerate higher injection pressures, lower mole-cular weight paraffinic hydrocarbons such as bu-tane or even propane , .~
~ may be utilized effectively, so long as the temperature and pressure . -at which the materials are injected are such that the fluid will enter .~ 20 the formation as a liquid.

; Another suitable asphalt preci~itating solvent for use is N-methyl-2-pyrrolidone whose formula is as folYows:

~'! H2 ~ - H2 H2 ~ \ = (N-methyl-2-pyrrolidone) .. ~, N~

'i This material should similarly be introduced into the formation in the .,.
fonm of a liquid, in orcler to insure that it effectively precipitates most o~ the bituminous or asphaltic material present in the sand pack.

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Still another solvent suitable for use in the process of our invention for the purpose of precipitating asphalt is furfural, whose fcrmLla is as follows:

H - C - C - H
I - I ~o H - C C - C' \0/ ~

A mixture of any two or mDre of the above materials may also ., .
be used effectively ~o precipitate the asphaltic or bitu~inous petroleum ~raction of the petroleum.
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IV. lidifi~ation of the Asphalt or Bitumen ~^ After the asphaltic or bituminous fraction of the petroleum has been precipitated by suitable trea~ent as described im~ediately above~ the ~lnal phase of the process for fcrming the sand controlled permeable barrier is to intrGduce a heated fluid, preferably a heated ~` gaseous fluid into the sand pack to vaporize volatile materials present and solidify the asphaltic or bituminous ~aterial. Steam is an especially Freferred fluid for this purpose, since it is inexpensive and readily i . .
available, and equipment for generating steam~will frequently be , aYailable in the oil field f~r the thermal recovery stimulation process , 20 to b~ applied 1ater. : . ~

- Eit~ r satura*ed or super heated stean may be u-tilized in ~ ~ -~his step, althou~h ordinarily the preferred e~bodiment will be to .. . . .
utilize saturated steam because it is less expensive and quite satis-fact~ry fcr this purpose. So lo~g as the temperature of the sand pack is raised to at least 250F, the desired solidification o~ the deposited asphalt will be achieved. It is pre~erred that the steam tenperature be at least 300F in order to e~fectively solidify the asphaltic mater~
ials in a reasonably short period of ti~e. Ordi~arily, the t~ne re-. . .
~uir2d for the solidification step will b2 inversely related to the temperature. Thus, if lower temper~ture fluids are util;zed to heat :, , ~ , .
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IL~5~358 and solidify the asphaltic material, a longer period of time will be required. If the steam is at least 300F, the desired solidification occurs within only a few hDurs. Ordinarily frQm about 1 to about 12 hours is sufficient to solidify the deposited asphaltic material.
though longer exposure to steam wQll not be detrimental to the process~
and may be utilized if desired, there is no particular advantage to in- -jecting stean into the sand pack for any period of time longer than is necessary to achieve the desired solidification of the asphaltic ~aterial~.
~ny other heated gaseous material m~y be utilized for the solidification step. For example, air or nitrogen or any other suitable gas may be heated to a temperature of around 300F-and passed throu~h the sand pack to effectively solidify the asphaltic materials and ~ind the loose sand grains together.
V. Field Exa~ple me process of our invention may better be understood by .
reference to the following pilot field e~ample, which is offered only as a preferred illustrative embcdiment,~and is not intended~to ~e : .
limitative or restrictive of our invention.
A tar sand deposit is to be subjected to steam emLlsification drive. A well is drilled into the tar sand deposit~ which is located under an overburden wXose thickness is about 300 feet and the tar sand , deposit thickness is around 75 feet. I~e tar sand deposit im~ediately adjacent to the well is under-r~ned to create a cavity approxima+.ely 3 feet in d~neter extending the full 75 foot thickness of the tar sand ,:.i, -deposit. A casing is run to the top o~ thé tar sand deposit and a production tubing string is run to the bottom of the tar sand deposit.
Perforations are ~ormed over the full 75 foot interval, since it is ,! desired to introduce fluids essentially uniformly into the tar sand , interval.
A slur~y is f~rmed of 40 to 80 mesh Xrac sand in WRter~ and . this slurry is pum~ed into the annular space. Water is pumped from -the , ,

5~358 prcduction tubing, to cause the sand grains to pack closely around the perforated production tubing and to form there~y a dense sand pack which substantially fills the cavity around the well. This is continued until ~; calculations indicate that the sand pack is about 1 foot above the top of the perforaticn.
Prior to introduction of the bituminous pe-troleum, steam at a temperature of 300F is pumped into the production tubing to contact the sand pack and heat the sand grains contained therein near a te~Pera-ture near 300. Passage of s-team therethrough for a~out 2 hours is sufficient to heat the sand grains.
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A quantity of bituminous petroleun obtained ~rom the tar sand ~aterial similar to that found in the ~orm~tion is heated to a tem~era-~
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ture of 300F and introduced into the production s~ring, where it ~lows ~ ~ -out ~hrough the per~orations and saturates the sand grains. Since the -porosity of the sand pack is approximately 20 percent, the volume to be -saturated with bituminous petroleum is - (7) x 1r x 75 x .20 = 105 cubic feet, which is the amount of bituminous petroieum to be introduced into the tubing string to i ~ saturate the sand pack. Approximately 10 percent excess is utilized to . :~
~ assure that good contact between all of the sand and bituminous ~etrc- ;
~ leum is achieved.
: ~ : Air i5 slowly passed dowr. the production tubing to cool the bituminous petroleum and sand to about lOn prior to the next step, so ~hat the asphalt participating solvent will not be vaporized upon ;~
~ontacting the hot ma~erial. ~ -, ,v . . . .
Hex~ne is chosen as the asphalt precipitating solvent, since it is not de~ired to exceed the overburden-related pressure limitation -:, . , - , and since it is necessary that the solvent enter ~his sand pack in a ~ uid forn. Approximately S0 gallons of hexane is pumped slowly into ; 30 the injection tubing. During this time the annular space is closed off .
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50 the hexane with portions of the petroleum dissolved therein will enter the formation rather than pass back up the tubing. After the hexane has been pumped into the sand pack, steam at a temperature of 325 is introduced into the sand pack for approxImately 6 hours so as to solidify the precipitated asphalt, to bind the sand grains together and form the desired permeable mass for sand con-trol purposes~
me well treated according to the above discussion is utilized -as the production well and the su~sequently a~plied steam-emulsification drive process, and no problems are encountered in connection with move-ment of unconsolidated sand into the well bore, and further th~t the perm~able mass formed in accordance with the above described procedure is not affected by subsequent contact with steam and caustic.
VI. Experimental Section - me following laboratory e~periments were performed to verify the operability and determine the effectiveness of the process of our .. . . .
invention. A linear laDoratory cell approximately 7 inches in length and 1.4 inches in diameter was packed with a sample of athabasca tar sand to a density of 1.8 grams per cubic centimeter. A total of 145 cubic centimeters of liquid normal butane was injected into the sand 20 pack in 5 slugs averaging 29 cubic centimeters per slug, each slug - being depleted by normal butane vapor pressure. Steam at a temperature of 294F was then introduced into the cell to displace the oil. After ,. . .
~J ~ ~. . cGmpletion of this experiment, the conterlts of ~he cell was examined and i~ was noted that the 3 inches into the cell from the point of , , . ~
injection was consolidated by dark precipitate~, and the portion imme-di tely adjacent to the injection well was very well consolidated and p:¢me3ble.
us we have disclosed and demonstr~ted that a sand controlling perneable .mass may be ~orn~lated by contacting a mixture of sand and - 30 asphaltic or bituminous petroleum, which may be naturally occurring or - ~
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10~i4358 may be placed in the well bore for the purpose of formLng the permeable mass, by contacting same with an effective asphalt precipitating solven-t such as a l;quid paraffinic hydrocarbon~ as well as with furfural or N-methyl-2-pyrrolidone, and thereafter introducing steam or any other hsated fluid mto the zone for the purpose of dehydrating and solidify-ing the asphaltic material. The asphaltic material binds the sand grams together, orm mg a permeable mass which wlll effectively restrain the flow of sand into the well bore during periods of recovery of fluid -: :
~ therefrom.

,- 10 Whils our invsn~ion has been disclosed in te~ns of a number :
of illustrative embodiments, it is not so limited since m ny variations thereof will be apparent to persons skilied in the art without departing from the true spirit and scope of our invention. Similarly, while ~;~` reactions and mechanisms have been proposed to explain the benefits re-sulting fron the application of the process of our invention, it is not ~ necessarily hereby repres~nted that these are the only or even the '~A, , principal reactions and mechanisms occurring9 and we do not wish to be ~', , , ~ ' .
bound by any particular mechanism or reaction. It is our intention ~ ~
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that our inven~ion be limited and restricted only by those limitations and restrictions as appear in the claims appended immediately hereinafter :, . . : , .
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Claims (13)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of treating a subterranean, unconsolidated sand and petroleum containing formation penetrated by at least one well, said well being in fluid communication with the subterranean formation, for the purpose of forming a permeable barrier around the well to restrain the movement of sand particles while permitting the passage of petroleum therethrough, comprising:
(a) introducing a pre-determined quantity of granular material whose particle size is from 10 to 80 mesh, into the well bore adjacent the formation;
(b) introducing bituminous petroleum into the granular material;
(c) introducing an asphalt precipitating solvent selected from the group consisting of paraffinic hydrocarbons having from 3 to 10 carbon atoms, furfural, N-methyl-2-pyrrolidone, and mixtures thereof; and (d) introducing a heated fluid into the granular material at a temperature of at least 250°F and to solidify the precipitated asphalt.

2. A method as recited in Claim 1 wherein the granular material is sand.

3. A method as recited in Claim 1 wherein the particles size of the largest sand grain contained therein is not more than twice the particle size of the small sand grain contained therein.

4. A method as recited in Claim 1 wherein the particulate matters introduced into the well bore by forming a slurry of particulate matter and fluid and pumping the slurry into the well, so that the particulate matter forms against the face of the formation.

5. A method as recited in Claim 1 wherein the asphalt precipitating solvent is hexane.

6. A method as recited in Claim 1 wherein the asphalt precipitating solvent is pentane.

7. A method as recited in Claim 1 wherein the asphalt precipitating solvent is furfural.

8. A method as recited in Claim 1 wherein the asphalt precipitating solvent is N-methyl-2-pyrrolidone.

9. A method as recited in Claim 1 comprising the additional initial step of removing a portion of the formation immediately adjacent to the well bore to form a cavity.

10. A method as recited in Claim 9 wherein the formation material is removed by washing with a liquid.

11. A method as recited in Claim 9 wherein the formation is removed by mechanical reaming.

12. A method of treating a subterranean, asphaltic or bituminous petroleum containing formation, which formation contains unconsolidated sand, said formation being penetrated by at least one well in fluid communication with the subterranean formation, for the purpose of forming a sand restraining permeable barrier, comprising (a) introducing asphalt precipitating solvent selected from the group consisting of paraffinic hydrocarbons having from 3 to 10 carbon atoms, furfural, N-methyl-2-pyrrolidone and mixtures thereof; and (b) introducing a heating fluid into the formation to heat the formation contacted by the asphaltic precipitating solvent, to solidify the asphalt on the sand grains, so that a barrier is formed around the well bore.

13. A method of treating a subterranean formation penetrated by at least one well to form a permeable, sand restraining solid barrier around the well, said formation containing unconsolidated sand and petroleum having appreciable bituminous or asphaltic content, comprising:
(a) introducing a liquid asphalt precipitating solvent selected from the group consisting of paraffinic solvent having from three to ten carbon atoms, furfural, N-methyl-2-pyrrolidone, and mixtures thereof; and (b) introducing a heated, gaseous fluid selected from the group consisting of steam, air, nitrogen and mixtures thereof at a temperature of at least 250°F to solidify the precipitated asphalt.