CA1056147A - Method of consolidating subterranean formations using diluted resins - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A method of consolidating incompetent subterranean formation surrounding a well wherein a liquid resin diluted with a two-part diluent is injected into the formation and is followed by an overflush liquid to extract the diluent but leave the resin on the sand grains. The two-part diluent comprises a first component miscible with the resin and a second component immiscible with the resin but miscible with the first component and the overflush liquid.

Description

~C~5~7 1 aACKGROUND OF TH~ INVENTION

2 ~leld o~ the Inventlon

3 This invention relates to a method for consolidating subterrnnean orm~tLons uslng dilute~ resln and over~ sh 0118 to extract the resln dLLu~3n~. In one a~pect, lt relates to the use of an improved dlluent for 6 reslns used ln such operations.
7 Description oE the Prior Art 8 The use of resins as a sand control means in oil wells, gas 9 wells, water wells, and similar boreholes has long been employed. The plastic consolidation treatmen~s, as t~ey are co~monly called, involve the 11 inJection of a liquId resin lnto the formation and thereafter causing the ~2 resin to cure to an ~nusi~1e state. The resin cements the sand grains 13 together forming a permea~le c~nsolidated sheath around the wellbore. In 14 order to ~e successul, the consolidation treatment must not only provide a hi8h strength in the consolidated interval, but must retain a high percentage 16 of formatiQn permeabilit~ t~rough w~ich the produced fluid can flow. ~ ~ ;
17 In cer~aln types of treatments, adequate permeability can be 18 achieved onl~ by the use of an overflush liquid which functions to remove 19 resin ~rom t~e pore space.
Oppos~ng mechanisms are involved In t~e overflushing process:
21 resin must b~ removed to provide permeability but sufficient resin must be 22 left on the sand grains to provIde adequate consolidation strength. An 23 improper halance of these two conditions wIll result in the failure of the 24 consolidation treatment.
T~e pro~lem o achlevIng t~e proper balance of permeability and 26 strength in t~e treated interval ~èn an oil overflush ls used is even more 27 difficult in res~n6 ~hich employ diluents. These resins, exe~plified by ~8 epox~ resins, are availa~le only as viscous liquids or sol~ds. In order to 29 handle and in~ect t~ese resins in~o t~e ormation, ~hey ~us~ be diluted 3Q with a suitaU e d~luent. Moreover 9 since the sequential in~ection of the 31 treating fluids normally exhi~its a progressively increasing viscoslty ~in -2- ~ ~

1(~5~ 7 1 the order of in~ection~ to ~rovide favorable mobility ratios, high resin 2 vLscosities will result in even higher viscosities of the following liquids 3 nnd, con~sequ~ntly, still more dificulty in~ec~lng the required overfl-lsh oLI..
Wi~h dJ.luted res~ns, the overflushing liquld must selectlvely 6 cxtrAc~ the dllu~n~ ~rom ~he resin. If substantial amounts oE the diluent 7 are left ln the resin, the resin, upon cuTing, will not attain sufflcient 8 compressive strength for the purposes of sand consolidation treatments.
9 Thus, merely displacing t~e diluted resin Prom pore space to provide per-meaBilit~ is w~oll~ unsatisfactor~.
11 It might Be thought that an ePfective single comp~nent resin 12 dil.uent could be thoroughly extracted from the resin by simply overflushing 13 ~ith a larger guantity oP overPlush oil. However, this practice has short-14 comings. La~qoratory tes~s have shown that the use of large amounts of the lS overPlush oIl wlll adversely a~ect compressive strength of the consolidated 16 interval, Large amounts of t~e solu~le diluent render the resin slightly 17 soluble in t~e overflush liquid. Thus, large amounts of overflush oil 18 will~ either by erosion or by dissolution, remove su~stantial amounts of 1~ resin from the sand grains, with tae result that there is insufficient resin left on tae sand grains to provlde a high strength consolidated 21 interval.
22 In summar~, the resin diluent must simultaneously ~e effective in 23 reducing res-in viscosity and be easil~ extTactable ~y the overflush liquid.
24 Unfortunatel~, resin diluents that have been used in the past either exhibit good vlscosit~ reduction propertles or good extract~ility ~y t~e overflush 2~ uid, aut not 60th oP t~ese important propeTties.
27 An example of one common diluen~ used with epoxy resins is ethyl 28 acetate. ~See "Consolidation o~ Silty Sands with an Epoxy Resin Overflush 2~ Process" b~ E. H. Ricaard~on et al., pu~lished in Journal of Petroleum Technolog~, September, 1~70.2 T~is diluent is readily extractable by the 1.

31 overflush oil ~ut it is only maderately effective in reducing the viscosity ~5~47 L of a liquid epoxy reqin. Relatively large amounts of athyl acetate are 2 requlred to reduce the resin viscoslty sufEiciently to permlt easy in~ectlon :~ lnto ~hc formatlon. Illgh dllu~ons result ln lower resin retentLon and, , th~reEore, lower strength.
S ~nother diluent commonly used with epoxy resins ls acetone ~see 6 U.S. Patent 3,612,1812. Acetone is more effective in reduclng resln vis-7 cosit~ than is ethyl aceta~e, ~ut unfortunately it is not easily extracted 8 by the overflush oll. In order to permit removal of substanti~l amounts of 9 acetone by t~e extraction process, its concentration is normally limited to about fifteen ~eight percent in the resin solution. This reduces the resin 11 viscosity to onl~ about ~0 centipoises, which, as noted above, is unsuitable12 for many treatments.
13 Reactive diluents such as propylene 02ide, styrene oxide, octylene14 oxide, and the lik~ have also been proposed for use with epoxy resins tsee V.S. Patent 3,176,7~8~. Except Eor propylene oxide, most of the reactive 16 dilllents are not particularly effective in reducing resin viscosity.
17 ~ropylene oxide, whIle an effective viscoslty reducer, is extremely hazardous 18 to use ~ecause it is kno~n to react spontaneously with many common chemicals1~ such as copper qr ~rass to form explosive acetylides.
2Q Plastic sand consolidation treatments which rely on the use of 21 dilute resins and diluent extractants have been widely used over the years 22 and have proven satisfactory as a sand control technique. However, it is 23 ~elieved that they have not re~lized their full potential in developing 24 long life and highly permea~ility consolida~ions. It is believed that one of the ma~or pro~lems wit~ these syste~s is due to the type of diluents 26 commonly emplo~ed~

27 SUMMARY OF TH~ INV~NTION
2S T~e plastic sand consolidation method of the present invention 29 employs an i~proved resin diluent that not only exhibits good viscosity 3Q reduction but also is readily extracta~le by the overflush liq~id. Briefly, . . . . .

~5~

the invention contemplates the sequeutial injection :Lnto a subterranean formation of n resin solution whlch contains a two-pa~t diluent followed by the lnjectlon of n dlluent e~tracting pore openlng li(luid (l.e. over-~lus~l lL~ id). 'l'he two-part dLluent compllses a substcllltLal nmount o~ a fLrst colllponellt mlsclbLe wlth tlle resin and a substantl~l amo~mt oE a secolld component lmmlscible wlth the resin but mlscible with the first componellt and the overflush liquid.
The two-part diluent is particularly suitable for use in processes which employ epoxy resins, since almost all of these systems use diluents to reduce the viscosity to satisfactory levels. Such systems thus require the diluent to be extracted following placement of the resin solution in the formation.
The concentration of the diluent in the resin should be sufficient to provide the final resin solution with a viscosity of not more than about 30 centipoises at about 72F, and preferably not more than 20 centipoises at about 72F. The concentration of the two-part diluent in the resin will normally be between about 10 and 40 weight percent to achieve the desired level of viscosity reduction. Laboratory tests have shown that the two components of the diluent may be used in various weight ratios ranging from about 1:1 to about 9:1 (resin miscible:resin immiscible).
The preferred weight ratio is from about 1.5:1 to about 4:1. In order to enhance diluent miscibility with the resin, the miscible component pre-ferably constitutes the major weight proportion of the diluent and is present in the resin solution at a concentration not in excess of about 25 weight percent.
The miscible component of the diluent may be those diluents commonly used for resins. For epoxy resins, usable miscible components include acetone, ethyl acetate, ethylene glycol monobutyle ether, dibutyl phthalate, monomeric styrene, and reactive diluents such as propylene oxide, phenyl glycidyl ether, phenolic diluents~ and the like.
The immisible component may include low molecular weight non-_5_ ~356~7 aromatic hydrocarbon liquids. Suitable hydrocarbon llquids include C4-C12 alkanes and alkenes, and C5-C12 cycloalkanes and cycloalkene5, and the - 5a -- .

1~5~ 7 Llkc. Such materiAls are not readily miscible with the resin but are ~ mlcicible ~lth both the typical resln-miscible diluents and the overflu~h 3 olL. ALso ~Isable are middle dLstlllates Oe reEined petroleum whlch lnclude

4 kero~cne, ~n~ oll, dlesel fuels, and the Llke.
The overflush liquid i9 normall~ an oll substantlnlly free of 6 aromatlcs and olefins. White oIls, techn:tcal and industrial grades, are 7 Erequently used as an overflush liquid because these oils are substantlally 8 immiscible with resIns and at least partially miscible with most diluents.
9 In order to enhance diluent extraction, the overflush oil should be miscible l~ with the resin-immiscible component and with at least 5% concentration of 11 resin-miscible component.
12 Laborato~ tests have shown that the use of the two-part diluent 13 in epoxy resins not only provides adequate viscosity reduction but also 14 improves the strength of the consolidated interval. The reasons for the improvement are not full~ understood but are bèlieved due to the ease with 16 which substantial amounts of the diluent are extracted from the resin 17 solution.
18 T~e present invention is descri~ed in detail below with particular 19 emphasis on t~e epox~ resin systems. Agaln, it should be observed that the 2Q principles exemplified a~ the invention are equall~ applicaale to other 21 resin systems that emplo~ a resin solution and diluent extractant in con-22 solidation of inco~petent subterranean formations.

23 DESCRIPTION OF TH~_~REFERRED EMB~DIMENTS
24 Th~ two-part dlluent comprising a resin-miscible component and a resin-immiscible component ma~ be 61ended beore mixing with the resin or 26 the immiscible component ma~ be added to the resin diluted with the miscible 27 component. In eit~er technique for preparing the resin solution, the two-28 part diluant is miscihle with the resin and effectively reduces its viscosity 29 to usable ].a~els.

The total concentration of the diluent in the resin should provide 31 a sufficiently low vlscosit~ to permit inJection into the formation without ~5~i147 ~ :
I rlsklng fracturlng the formatlon. Low viscosity also Eavors we~ting of the 2 sand graLns and capillar~ f]ow ln the pore spaces. Tests have shown thnt 3 v;L~co3ltLes Oe abou~ 30 centipoises or les9 flt 72F are satlsfactory.
4 ItlealLy, howevcr, the resln soluelon should have a vlscoslty of about 20 S cen~Lpolses or less at 72F. The low vlscosity not only enables the resin 6 to ~mleormly invade the interv~l to be treated, it also aids in the handling 7 procedures, Normally the resin is in~ected through a tubing string and 8 into the formation. Highly viscous liquids tend to stick to the interior ~ of the tuBing and are not easily removed ~ trailing liquids. In the lQ treatments which emplo~ separate salu~ions for carrying the resin and the 11 curing agent to the ~ormation, premature mixing of tha curing agent with 12 the resin coating an the pipe can produce a partially polymeri~ed resln 13 tnat tends to plug the well~ore perforations and prevent uniform distribution 14 of the catalyst solution~
The present invention is particularly applicable in epoxy resin 16 systems. Epox~ resins useful for the purpoæe of this invention include the 17 diglycidyl ethers af ~isphenol-A [~isC4-hydroxy phenyl~ dimethyl methane]
18 obtained by the reaction of epichlorohydr~n Cl-chloro-2,3 epoxy propane~
1~ and bisphenol-A in the presence o~ an alkali such as sodium hydroxide or potassium hydroxlde. Similarly, a diglycidyl ether of ~isp~enol-F can be 21 prepared by reacting epichloroh~drin with bisphenol-F [bisC4-hydroxy 22 phenyl~ methane]. A mononucle~r di-or tri-hydroxy phenol such as resorcinol, 23 hydroquinone, pyrocatechol, or phloroglucinol or a polynuclear polyhydroxy 24 phenol such as 4,4-dihydroxy ~iphenyl ~ill produce an epoxy resin when 2~ reacted ~ith a halo~ydrin such as 1,2-dichloro-3-hydroxy propane or dychloro-26 hydrin. Still otaer satisfactary materials include the novolac epoxy 27 resins prepared By tae condensation of a polynuclear phenol with epichloro-2~ hydrin.
29 ~he epoxy resins are cured ~y curing agents Ce.g. hardeners, 3Q activators, or catalysts~. Usa~le curing agents are discussed at length in 31 the literature. Frequently employed curing agents include primary and J~56~7 1 secondar~ amines such as m-phenylenediamine, diethylene eriam~ne, and the 2 Like. Also usable are organic acids &nd acid anhydr:Ldes such as oxalic 3 tlc~(l, phthallc anhy~rlde, and the llke. Tertlary amines such as trl(dlme~hyl-mlnomethyl)phenol ~nd llewLs nclds such as boron triEluoride may also be ~Ise(l as curlrlg agents.
6 The epoxy resins may be applied by an internally-cured method 7 where:Ln a mixture of the resin and the two-part diluent along with the 8 curing agent is in~ected into the formation. An overflush liquid is then used g to displace the resin into the formation in order to impart the desired per-meability to the invaded pore spaces and to extract the diluent. The inter-11 nally-cured epoxy system is described at length in "Consolidation o~ Silty 12 Sands with an Epoxy Resin Overflush Process" supra.
13 Alternatively, the epoxy resins may be placed by an in-situ-cured 14 method wherein the resin dissolved in the two-part diluent is in~ected into the formation followed by the curing agent dissolved in the overflush 16 liquid. The overflush liquid displaces the resin into the formation and 17 imparts the desired permeability to the invaded pore spaces. The curing 18 agent is extracted by the resin in contact with the sand grains. This 19 causes the resin to harden, bonding the sand grains together. An in-situ-cured epoxy treatment is described in "Externally Catalyzed Epoxy for Sand 21 Control" by F. A. Brooks et al., published in Journal of Petroleum Tech-22 nology, June, 197~.
23 As described in detail in the references noted above, the consoli-24 dation treatments, in addition to the resin solution and overflush liquids, may employ other liquids such as pre-acidizlng treatments, preflush solvents, 26 spacer liquids, and the like. ~dditives for the various solutions may 27 includa silane coupling agents, thickening agents, surfactants, and the 28 like.
29 Laboratory Experiments The following laboratory experiments were performed to determine 31 the ability of various diluents to be extracted from the resin solution by ~56'1~7 1 contact with a typical overflush oil. The following three solutions were 2 prepared:
3 Sollltlon ~ o grnms of bisphenol-F resln havLng an epoxy equlvalent ~ wclght of 165 8rams per epoxlde was mlxed wlth 120 grams o~
acetone. The bisphenol-F resln used ln the experlment was a 6 product of Dow Chemical Cotnpany sold as Resin XD-7818.
7 Solutlon B: 480 grams of the bisphenol-F resln was mixed with 120 8 grams of propylene oxide (a reactive diluent).
g Solution C: 480 grams of the bisphenol-F resins was mixed with 120 grams of a two-part diluent comprising 90 grams of acetone 11 (misclble component) and 30 grams of cyclohexane (immiscible 12 component).
13 The following tests were performed on each of the three solutions:
14 (a) 100 milliliter sample of èach resin solution was mixed with 100 milli-liters of an overflush oil which in these tests was a mixture of two substan-1~ tially aromatic-free and olefin-free refined oils sold by Exxon Company, 17 U.S.A. as Mentor 28 and Flexon 766. tb~ The resin solution and overflush 18 oil were permitted to equilibrate at about 72F for about 90 minutes, the 19 lighter overflush oil rising to the top of the beaker. (c) the resin solution was drained off and its viscosity measured at about 72F. (d) A
21 second 100 ml sample of the resin solution was added to the same overflush 22 oil and the mixing, withdrawal of resin solution, and viscosity measurement 23 of the resin solution were repeated. This process was performed for four 24 separate 100 milliliter samples of each resin solution. The purpose of the test was to determine the cumulative effect of the overflush oil in extracting 26 diluent from fresh samples of the resin solution. If the diluent exhibited 27 limited solubility in the overflush oil, the overflush oil would soon 28 become saturated such that the addition of fresh samples of resin solution 2~ would be unaffected when mixed with the overflush oil. This would be reflected by no change in the viscosity of the re~in solution before and 31 after contact with the overflush oil. Table I pr~3ents the results of 32 these te~ts.
f~d e /r7~rK ~ ~

~SG,~4~

2 Viqcos:lty, cp at 72F
3 Solutlon ~ Solution BSolutlon C
~Uesln SollltLon SbeEora mlxlr~ 12.9 14.0 16.3 6Number of ~lxlngs 7 1 19.5 37.6 37.9 2 14.1 19.9 25.3 9 3 13.5 16.3 23.4 4 12.9 1~.2 21.6 11 From Table I, it can be seen that the diluent satlsfactorily 12 reduced the viscosity of each resin solution to less thsn 20 centipoises at 13 72F. The data also show that acetone (Solution A) was extracted to only 14 a limited extent by the overflush oil. The 100 milliliters of overflush oil became almost fully saturated after contact with only the initlal 100 16 mllllliter samples of Solution A. With the propylene oxide diluent, two 17 samples (200 ml) of Solution B were required to saturate 100 ml of over-18 flush oil. The two-part diluent was far more extractable than the other 19 diluents. Note that even after the 100 milliliters of overflush oil contacted 400 milliliters (all four mixings) of Solution C, it still was capable of 21 extracting diluent as reflected by the increase in viscosity from 16.3 to 22 21.6 centipoises.
23 In order to demonstrate the effect of the treatment according to 24 the present lnvention on the compressive strength of the consolidated interval, several consolidated samples were prepared and subjected to 26 compressive strength tests. Five sand samples consisting of about 2200 27 grams of Brazos River sand were packed in rubber tubes 1-1/2 inches in 28 diameter and 48 inches long. The packed tubes were inserted into steel 29 cells and subjected to a confining pressure of 1500 psi. ^ Each sample was evacuated, saturated with brine, flooded with number 2 diesel fuel, and 31 then flushed to residual oil saturation with 500 cc of brine. The tempera-32 ture of the test apparatus was maintained at about 180F and internal fluid 33 pressure was maintained at about 1000 psi.
34 Each sample was consolidated by the sequential injection of the following fluids:

.

~56~47 I (a) Pref]ush ]lquld: 200 ml of ethylene glycol isopropyl ether 2 contalnlng 0.5 welght percent o~ polyvinyLpyrrolidone sold 3 by C~R Corporntlon as PVP Type K90;
/~ (b) Resln Solutlon: 250 ml of a mlxture contalnlng 74.5 welght percent of a blsphenol-F resln sold by Dow Chemlcal Company 6 as XD-7818, 25 weight percent of a diluent, and 0.5 welght 7 percent of a silane coupllng agent sold by Dow Corning as Z-8 6020; and 9 (c) Overflushing Oil: 1200 ml of a mixture containing two refined oils sold by Exxon Company, U.S.A. as Flexon 766 11 (400 ml) and Mentor 28 ~800 ml) containing 3 weight percent 12 of tri(dimethylaminomethyl)phenol, a tertiary amine catalyst 13 sold by Rohm and Haas as DMP-30.
14 Following injection of the various solutions, each sand sample was permitted to cure for about 18 hours. The only difference in the 16 treatments described above was in the type of diluent used in the epoxy 17 solutions. In each of the resin solutions, the diluent concentration was 18 25 weight percent based on the total weight of the solution. The diluents 19 used in the five treatments were (1) acatone; (2) propylene oxide; (3) three parts acetone and two parts cyclohexane; (4) three parts acetone and 21 one part cyclohexane; (5) three parts acetone, and one part pentane. The 22 ratios specified in samples 3, 4, and 5 are weight ratios.
23 All of the treatments produced fully consolidated 48-inch long 24 cores. The five cores were removed from the test apparatus and five ~5 representative samples were taken from corresponding locations in each core 26 were sub~ected to compressive tests. Compressive loadings on the cylindrical 27 samples 1-1/2 inches in diameter and 2 inches in height were gradually 28 increased until the sample cracked. Average compressive strength (at 29 failure) for the five samples of each core are shown in Table II.

~r~ nc.,~

.
:: : . . . .

3 ~5~ 7 2 Dlluent Used~verage Compressive 3 ln Resln SolutlonStren~h ~psi?
ll Core 1 Acetone 3060 Core 2 propylene oxide 3520 6 Core 3 3 parts acetone, 7 2 parts cyclohexane 5340 8 Core 4 3 parts acetone, 9 1 part cyclohexane 4510 Core 5 3 parts acetone, 11 1 part pentane 4700 12 The data in Table II clearly show the superlor re~ults obtained with the 13 two-part dlluent. The data also show that the specific type of resin-14 immlscible component used in the diluent does not appear to be critical.
Note the results wlth cyclohexane and pentane were comparable.
16 The reason for the improved results using the two-part diluent, 17 which as mentioned above was the only dlfference ln the treatment, is 18 believed to be due to the improved extractability of the resin-immiscible 19 component by the overflush oil. This component exhibits high solubility in the overflush oil, so that upon flowing through the core, the overflush oil 21 extracts substantial amounts of the resin-immiscible component from the 22 resin solution. The remaining resin on the sand grain is thus quickly ~ -23 transformed into a highly viscous liquid which further retards resin removal 24 from the sand grains. The two-part dileunt reduces the amount of miscible component required which in turn reduces the mutual solvency of the resin 26 and overflush oil. Moreover, the high solubility of the two-part diluent 27 in the overflush oil reduces the amount of fluid that must be flowed past 28 the resin on the sand grains, and thereby reduces resin removal by erosion 29 or dissolution. It is believed that these are the mechanisms whereby the two-part diluents leave substantially more resin on the sand grains than do 31 the other diluents.

' ' ' , ' , , ~ ': , ' 1~5~7 1 Field Procedure _ 2 The procedure and the specific materials used in performing 3 plastic sand consolidation in accordance with the present lnven~ion can 4 vary within wide ranges and will depend on several factors including type o~ formation, formation conditions, resins employed, and well equipment, to 6 name but a few. One specific procedure for carrying out the invention 7 using an in-situ-cured bisphenol-F epoxy resin system is described below.
8 In most treatments, it ganerally will be preferred to remove the 9 producing tubing (if used) from the well and inserting a workstring for cleanlng out the well and for conducting treating fluids to the formation.
11 The workstring used preferably is a small diameter tubing having internal 12 flush ~oints. Alternately, the fluids may be pumped through the production 13 tubing in a "bullhead" pumplng procedure. The various fluids used in the 14 treatment are usually injected in the follo~ing sequence: ~1) preflush solvent, (2) resin solution, (3) spacer oil, (4) catalyst solution. In 16 some treatments, it is preferred to acidize the formation pr~or to the sand 17 consolidation to prepare the interval for treatment. Typical acids include 18 HF or mixtures of HF with mineral acids such as HCl. Wiper balls or plugs 19 may also be employed ln the spacer oll to insure complete separation of the catalyst solution and the resin solution. In a typical treatment, the 21 pumping sequence, approximate volumes, a~d viscoslties of an in-situ-cured 22 epoxy treatment will be as follows:

24 Volume (gal) Per Foot of 26 Viscosity Formation 27 range (cps) Thickness 28 Example _ _ at about 72~F Treated 29 Preflush Ethylene glycol isopropyl3 to lO 50 to 150 solvent: ether containing from 0.1 31 to 1.0 wt. % polyvinyl-32 pyrrolidone and 0.1 to 1.0 wt.
33 % coupling agent (e.g.
34 ~-~020) ~35~ 7 l Resin Epoxy sold by Dow .Chemical 10 to 30 50 to 90 '~ 2 solution: Company as XD-78l8~ with 3 from 20 to 30 wt. % two-4 part diluent (e.g. 3 parts acetone, one part cyclo-6 hexane) 7 Spacer Refined oil substantially 15 ~o 35 10 to 40 8 oil: aromatic-free and olefin-g free (sold by~Exxon Co., USA as~Mentor 28 and ll Flexon 766) 12 Overflush Refined oil (sold by Exxon 15 to 35 250 to 400 13 Oil Co., USA as Mentor~ 28 and 14 Flexon~766) and from 2 to 4 wt % curing agent (e.g. an 16 amlne sold by Rohm and Haas 17 as DMP-3~
18 The injection rate should be sufficiently low to prevent fracturing of the 19 formation. As a general rule, the liquids are injected at a rate of from about 1 to 4 gallons per minute for each foot of formation consolidated.
21 ~ollowing the pumping of these liquids into the workstring, a 22 displacing oil is normally pumped to insure that all of the overflush oil 23 is injected into the formation. The well i8 then shut in for a period 24 sufficient to permit the resin to cure to an infusible state which normally re~uires about 12 hours.
26 Again, it should be observed that the method of the present 27 invention may advantageously be used in the internally-cured epoxy system, 28 which, as mentioned above, relies on the use of diluents and the extraction 29 of the diluents to achieve high strength consolidated intervals. Other systems, such as phenol-formaldehyde resin systems and furan resin systems, 31 may also employ the two-part diluent. Of course, i~ will be realized that 32 specific materials and procedures may differ somewhat from thos~ described 33 herein. However, the principle exemplified by the two-part diluent in 34 providing low viscositieæ for the resins and exhibiting good extractability by the overflush oil are equally applicable to such systems.

Claims (20)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for the consolidation of an incompetent subterr-anean formation surrounding a well which comprises:
(a) injecting into said formation a liquid resin containing sufficient amounts of a diluent to reduce the resin viscosity to 30 centi-poises or less at about 72°F, said diluent including substantial amounts of a resin-miscible component and substantial amounts of a resin-immiscible component, said resin-miscible component and said resin-immiscible component being mutually miscible; and (b) thereafter injecting a non-aromatic hydrocarbon liquid into said formation to extract diluent from the liquid resin, said liquid being substantially immiscible with said liquid resin, miscible with said resin-immiscible component, and at least partially miscible with said resin-miscible component.

2. A method as defined in claim 1 wherein the liquid resin is an epoxy resin.

3. A method as defined in claim 2 wherein the concentra-tion of the diluent in the epoxy resin solution is between about 10 per-cent and 40 percent by weight.

4. A method as defined in claim 2 wherein the weight ratio of said resin-miscible component to said resin-immiscible component ranges from about 1:1 to about 9:1.

5. A method as defined in claim 3 wherein the resin-miscible component is selected from the group consisting of ketones, esters, glycol ethers, glycidyl ethers, epoxides; and the resin-immiscible component is a nonaromatic hydrocarbon liquid having no more than about 12 carbon atoms per molecule.

6. A method as defined in claim 5 wherein the hydrocarbon liquid is a saturated hydrocarbon having from 4 to 12 hydrocarbon atoms per molecule.

7. A method as defined in claim 6 wherein the hydrocarbon liquid is a C5 to C12 alkane.

8. A method as defined in claim 6 wherein the saturated hydro-carbon is a cycloalkane having from 5 to 12 carbon atoms per molecule.

9. A method as defined in claim 5 wherein the hydrocarbon liquid is an unsaturated hydrocarbon.

10. A method as defined in claim 9 wherein the unsaturated hydro-carbon liquid is a cycloalkene.

11. A method as defined in claim 5 wherein the miscible component is a ketone.

12. A method as defined in claim 11 wherein the ketone is acetone.

13. A method as defined in claim 1 wherein the hydrocarbon liquid contains a curing agent for said resin.

14. A method as defined in claim 1 wherein the liquid resin further includes a curing agent for said resin.

15. In a method for consolidating incompetent subterranean forma-tions wherein a resin solution comprising a liquid resin and a diluent therefor is injected into the formation and thereafter an overflush liquid is injected to extract said diluent, the improvement wherein said diluent comprises a substantial amount of a first component miscible with said resin and a substantial amount of a second component immiscible with said resin but miscible with said first component and said overflush liquid, and wherein the concentration of said diluent in the resin solution is sufficient to provide the resin solution with a viscosity of about 30 centipoises or less at about 72°F.

16. A method as defined in claim 15 wherein the resin is a liquid epoxy and the overflush liquid includes a curing agent for said epoxy resin.

17. A method as defined in claim 15 wherein the resin is a liquid epoxy and the resin solution further includes a curing agent for said epoxy resin.

18. A method as defined in claim 15 wherein the said diluent comprises from about 10 to about 40 weight percent of said resin solution and the weight ratio of said resin-miscible component to said resin-immiscible component ranges from about 4:1 to about 1.5:1.

19. A method as defined in claim 15 wherein the concen-tration of the resin miscible component in the resin solution is less than about 25 weight percent.

20. A method as defined in claim 15 wherein the concen-tration of the diluent in the resin solution is sufficient to provide the resin solution with a viscosity of not more than about 20 centipoises at about 72°F.