Use of elastomers to produce gels for treating a wellbore

Abstract

A method of treating an earthen formation that includes introducing a first amount of a first blocked isocyanate in a liquid phase into the earthen formation; introducing a second amount of a second blocked isocyanate in a liquid phase into the earthen formation; the second blocked isocyanate group having a lower unblocking temperature than the first blocked isocyanate group; introducing at least one active hydrogen compound into the earthen formation; and contacting the first and second blocked isocyanates and the active hydrogen compound to form an elastomeric gel. The combination of two blocked isocyanates provides a synergistic effect so that the curing time can be optimised in a manner unexpected from the properties of the individual blocked isocyanates.

Claims

1. A method of treating an earthen formation, comprising: introducing a first amount of a first blocked isocyanate in a liquid phase into the earthen formation; introducing a second amount of a second blocked isocyanate in a liquid phase into the earthen formation; wherein the ratio of the volumes of the first blocked isocyanate to the second blocked isocyanate is within the range of 4:1 to 1:4; wherein the second blocked isocyanate has a lower unblocking temperature than the first blocked isocyanate; introducing at least one active hydrogen compound into the earthen formation; and contacting the first and second blocked isocyanates and the active hydrogen compound to form an elastomeric gel, wherein the ratio of the first amount of the first blocked isocyanate to the second amount of the second blocked isocyanate is selected such that the second amount of the second blocked isocyanate added decreases the curing time of the formed elastomeric gel.

2. The method as claimed in claim 1, wherein the first and second blocked isocyanates and the active hydrogen compound are injected simultaneously.

3. The method as claimed in claim 1, wherein the first and second blocked isocyanates and the active hydrogen compound are injected sequentially.

4. The method as claimed in claim 1, wherein the first and second blocked isocyanates independently comprise a backbone formed from at least one of a toluene diisocyanate (TDI) monomer unit and an isocyanurate (IPDI) monomer unit.

5. The method as claimed in claim 1, wherein the first blocking group's unblocking temperature is between 110-150 C.

6. The method as claimed in claim 1, wherein the unblocking temperature of the first and second blocked isocyanates are within 50 C. of each other.

7. The method as claimed in claim 1, further comprising introducing at least one organometallic catalyst into the earthen formation.

8. The method as claimed in claim 1, further comprising introducing at least one additive into the earthen formation selected from a group consisting of a plasticizer, a filler, a rheological additive, an accelerator, a retardant, and an adhesion promoter.

9. The method of claim 1, wherein the treatment is at least one selected from a group consisting of wellbore strengthening treatments, loss control material treatments, water shutoff treatments, and zonal isolation treatments.

10. The method as claimed in claim 1, wherein the first and second blocked isocyanates independently comprise a blocking group selected from a group consisting of methylethylcetoxime (MEKO), diethyl malonate (DEM) and dimethylpyrazole (DMP) and -Caprolactam.

11. The method as claimed in claim 10, wherein the first and second blocked isocyanates independently include a blocking group selected from a group consisting of dimethyl pyrazole and -Caprolactam.

12. The method as claimed in claim 1, wherein the first and second blocked isocyanates react with the active hydrogen compound to form one of polyurethanes and polyureas.

13. The method as claimed in claim 12, wherein the first and second blocked isocyanates react with the active hydrogen compound comprising an amine to form a polyureas.

14. The method as claimed in claim 1, wherein the first amount is greater than the second amount.

15. The method as claimed in claim 14, wherein the second amount is 5-45 wt % of the total amount of the first and second blocked isocyanates.

16. The method as claimed in claim 15, wherein the second amount is 10-20 wt % of the total amount of the first and second blocked isocyanates.

17. The method as claimed in claim 1, wherein the first and second blocked isocyanates are mixed together before being introduced into the earthen formation.

18. The method as claimed in claim 17, wherein the first and second blocked isocyanates and the active hydrogen compound are injected simultaneously.

19. The method as claimed in claim 17, wherein the first and second blocked isocyanates and the active hydrogen compound are injected sequentially.

20. A method of treating an earthen formation, comprising: introducing a first amount of a first blocked isocyanate in a liquid phase into the earthen formation; introducing a second amount of a second blocked isocyanate in a liquid phase into the earthen formation; wherein the second blocked isocyanate has at least a 10 C. lower unblocking temperature than the first blocked isocyanate; introducing at least one active hydrogen compound into the earthen formation; and contacting the first and second blocked isocyanates and the active hydrogen compound to form an elastomeric gel, wherein the ratio of the first amount of the first blocked isocyanate to the second amount of the second blocked isocyanate is selected such that the second amount of the second blocked isocyanate added decreases the curing time of the formed elastomeric gel.

Description

(1) Embodiments of the invention will now be described, by way of example only, and by comparison with examples out with the scope of the present invention; all with reference to the figures in which:

(2) FIG. 1 is a plot showing a viscosity profile of DP9C/142 blended with DP9B/1915 showing the Increase in viscosity due to crosslinking when DP9B/1915 de-blocks;

(3) FIG. 2 is a plot showing the viscosity profile for DP9C/142 blended with a higher concentration of DP9B/1915 resulting in short cure time; and,

(4) FIG. 3 is a plot showing a viscosity profile on consistometer with DP9C/142 blended with DP9B/1915 at 212 F.

COMPARATIVE EXAMPLES

(5) DP9C/142 is a blocked isocyanate (BI) commercially available from Baxenden Chemicals Limited and is traditionally used in the paints and coating industry. It is formed from a TDI-aromatic backbone and the blocking group is -Caprolcatam. The TDI-aromatic backbone is normally provided as a blend of 2,4 and 2,6 isomers.

(6) It has an unblocking temperature in the range of 212-248 F (100-120 C.). The formulas for the backbone monomer unit (2,6 isomer) and blocking group are set out in formulas 1 and 2 respectively.

(7) ##STR00003##

(8) Various experiments were performed on DP9C/142 (and no other blocked isocyanates) but the cure times at 212 F (100 C.) were longer than the preferred cure times. Accordingly experiments were conducted with catalysts TIPA and EDA separately but the gel started to form only after around 1100-1200 minutes which remains less than the preferred cure time. A variety of other catalysts were then tried but none reduced cure times to their preferred duration. Other catalysts tried were zinc 3,3,5,5-tetramethylhexanoate, zirconium neodecanoate, 1,2 dimethyl imidazole, 1,4 dimethylpyrazole, diazobicyclo-undec-7-ene, triethanolamine, tetraethylene pentamine, magnesium oxide, triethylene tetramine, dibutyl tin dilaurate, triethylene diamine and dimethylamin-1-propylamine.

EXAMPLES

(9) In accordance with the present invention, combinations of two blocked isocyanates (Bls) were analysed. The first combination was DP9C/142 supra with DP9B/1915. DP9B/1915 is a blocked isocyanate commercially available from Baxenden Chemicals Limited. It is formed from IPDIcycloaliphatic backbone and the blocking group is dimethylpyrazole. It has an unblocking temperature in the range of 122-158 F (50-70 C.). The formulas for the backbone monomer unit and blocking group are set out in formulas 3 and 4 respectively.

(10) ##STR00004##

(11) To prepare the samples, 3.5 mls of solvent were added to 3.5 mls DPnB. The blocked isocyanates were added, hot rolled for 10 minutes at 212 F. (100 C.), then 3 g of molecular sieve, 0.5 ml of water and 1.9 mls JEFFAMINE T3000 (a polyetheramine available from Huntsman, www.huntsman.com) were added. The results are shown in table 1.

(12) TABLE-US-00001 TABLE 1 Obs @ Obs @ Obs @ Obs @ Sample DP9C/142 DP9B/1915 1 hr 3 hrs 4.5 hrs 72.5 hrs Hardness (g) 1 3.1 liq liq Liquid set 4584 (Comparative) 2 2.5 0.6 liq liq viscous @ set 4283 4.5 hrs 3 2 1.1 set @ set set set 4202 50 mins 4 1.5 1.6 set @ set set set 2944 40 mins
Thus it an be seen from the figures in table 1 that the samples 2, 3 and 4 (in accordance with the present invention) all set or are viscous before the pure, comparative sample 1. As a result of the results set out in table 1, large scale testing was carried out on a combination of 2.6 ml DP9C/142 with 0.5 ml DP9B/1915 at 212 F (100 C.). The results were plotted as a viscosity profile and are shown in FIG. 1. This shows composition to start gelling at around 377 minutes, which is much less than the comparative examples, and notably do not use any catalyst to speed up the gellation time, whereas the comparative samples do, which started to gel at 1,100-1,200 minutes.

(13) A further test was performed with an increased concentration of the lower temperature de-blocking isocyanate (DP9B/1915) compared to the higher temperature de-blocking isocyanate (DP9C/142) (1:2.1) and the composition started to gel at around 1 hour. The results were plotted as a viscosity profile and are shown in FIG. 2.

(14) FIG. 3 shows the cure rate for three different blend compositions.

(15) Whilst not being limited by theory, it is thought that the specific BI in this case, DP9B/1915 is releasing its de-blocking group (3,5-dimethylpyrazole) and that this blocking group is itself behaving like a catalyst (1,4-dimethylpyrazole is a catalyst used for PU systems). However further work with different blends has shown that blending of different BIs with a range of de-blocking temperatures can also give the formulator greater control over cure times. The following results illustrate this point.

COMPARATIVE EXAMPLES

(16) Three different blocked isocyanates were analysed individually for their cure times at 248 F (120 C.). DP9B/1915 and DP9C/142 as detailed above, as well as DP9B/1916. DP9B/1916 is a blocked isocyanate commercially available from by Baxenden Chemicals Limited. It is formed from IPDIcycloaliphatic backbone and the blocking group is eCaprolactam. It has an unblocking temperature in the range of 284-320 F (140-160 C.). The formulas for the backbone monomer unit and blocking group are set out in formula 3 and formula 2 above respectively.

(17) Each blocked isocyanate as provided in a solvent and the composition of the solvent is given in table 2 below.

(18) TABLE-US-00002 TABLE 2 Composition of single-system BI compositions Product DP9B/1916 142 DP9B/1915 Blocked Isocyanate 5 5 5 Base Oil 3.5 3.5 3.5 DPnB 1.5 1.5 1.5 T3000 5 5 5 Water 0.5 0.5 0.5 MS 3 3 3

(19) The results to determine the curing time for these isocyanates is shown in table 3 below.

(20) TABLE-US-00003 TABLE 3 Obs @ Obs @ Obs @ Obs @ Obs @ Results 1 hr 2 hr 3 hrs 4 hrs 20 hrs DP9B/1916 liq liq liq liq set DP9C/142 liq liq liq liq set DP9B/1915 set set set set set
As can be seen from table 3, the set times for DP9B/1916 and DP9C/142 respectively is at 20 hours whereas the lower temperature DP9B/1915 5is set at 1 hour.

(21) Whilst the DP9B/1916 and DP9C/142 samples are effective for their intended downhole application, the cure time is longer than optimal and this restricts the particular applications for which it can be used.

EXAMPLES

(22) Three combinations of the above BIs were analysed in accordance with the present invention. Their compositions are set out in table 4 below.

(23) TABLE-US-00004 TABLE 4 combination compositions Product Combination 1 Combination 2 Combination 3 DP9B/1916 2.5 2.5 0 DP9C/142 2.5 0 2.5 DP9B/1915 0 2.5 2.5 Base Oil 3.5 3.5 3.5 DPnB 1.5 1.5 1.5 T3000 5 5 5 Water 0.5 0.5 0.5 MS 3 3 3

(24) The various compositions were maintained as a homogenous mixture when the gels set, which in itself was surprising as they were expected to separate out into globules and set according to their individual properties. Table 5 shows the setting times for the different 5 combinations.

(25) TABLE-US-00005 TABLE 5 Obs @ Obs @ Obs @ Obs @ Obs @ Results 1 hr 2 hr 3 hrs 4 hrs 20 hrs Combination 1 liq liq liq liq set Combination 2 liq v. viscous set set set Combination 3 liq v. viscous set set set
Thus it can be seen from the above results that the combination of DP9B/1915 and DP9B/1916 (combination 2) set after 3 hours and is very viscous after 2 hours, compared with pure DP9B/1916, which is liquid at 4 hours. Similarly the combination of DP9B/1915 and DP9C/142 (combination 3) set after 3 hours and is very viscous after 2, whereas DP9C/142 itself set after up to 20 hours.

(26) It could not be deduced from the results set out table 5 whether combination 1, a blend of DP9B/1916 and DP9C/142, set before the DP9B/1916 sample because of time restrictions in the lab. Further testing was this carried out an increased temperature, 284F (140 C.) using a composition set out in table 5 below and the results are shown further below in table 6 and table 7.

(27) TABLE-US-00006 TABLE 6 Base Oil 3.5 DPnB 1.5 Water 0.5 T3000 5 MS 3

(28) TABLE-US-00007 TABLE 7 Over Peak Obs @ Obs @ Obs @ Obs @ weekend Hardness Depth Sample DP9B/1916 DP9C/142 90 mins 210 mins 420 mins 480 mins (72 hrs) (g) (mm) 1 5 0 liq liq liq liq set OS 19.8 2 4 1 liq liq liq liq set 2358 18 3 3 2 liq liq liq viscous set 2100 20 4 2 3 liq liq very set set 931 20 viscous 5 1 4 liq very set set set 748 20 viscous 6 0 5 liq set set set set 285 20
Thus it can be seen that the combination of DP9C/142 and DP9B/1916 does set before that of DP9B/1916 itself.

(29) Accordingly by choosing a combination of BIs, the curing period can 5 be optimised and so be used for each specific application as required. Moreover a further advantage of certain embodiments is that.

(30) While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.