VISCOSIFICATION AND FOAMING OF POLYACRYLAMIDES

Abstract

Embodiments of the invention relate to a method for treating a subterranean formation, comprising forming a fluid comprising polyacrylamide and a biopolymer and introducing the fluid to a subterranean formation wherein the polyacrylamide and biopolymer are selected to form the fluid with a longer foam half life and a higher viscosity than if only one polymer were selected. Embodiments of the invention relate to a method for treating a subterranean formation, comprising forming a fluid comprising polyacrylamide and a biopolymer and introducing the fluid to a subterranean formation wherein the polyacrylamide does not alter biopolymer crosslinking.

Description

PRIORITY

This application claims priority to U.S. Provisional Patent Application Ser. No. 61/330,048, filed Apr. 30, 2010, entitled, “Viscosification and Foaming of Polyacrylamides,” and incorporated by reference herein in its entirety.

FIELD

Embodiments of the invention relate to methods and compositions of fluids for use in the oil field services industry. Specifically, embodiments relate to fluids containing polyacrylamide.

BACKGROUND

The constraints on gas handling capacity have resulted in shutting-in a significant number of high gas-oil-ratio (GOR) wells. In most cases, the workover objectives involve plugging the invaded gas zones to produce from another zone and restore oil production. One major problem in naturally-fractured carbonates is the reduction of the crude oil production due to the water and gas breakthrough. Numerous solutions take into account several parameters for gas shut off treatment design. Some of these parameters are: determination of the type of system that fits best the well-reservoir conditions, treatment volume, average fissure/fracture width and number of fissures to be plugged. However, another problem is the best placement technique for the sealing system in the gas zone.

Few techniques have been developed to address the gas breakthrough in naturally-fractured carbonates, so it is a matter that has yet to be widely discussed and researched.

The main challenges faced for gas and water shut-off treatments include:

• • Poor cement behind the production liner.
  • Low reservoir pressure and massive fractures resulting in loss circulation.
  • Uncertainty with fracture volumes estimation.
  • Treatment execution under sub-hydrostatic conditions.

SUMMARY

Embodiments of the invention relate to a method for treating a subterranean formation, comprising forming a fluid comprising polyacrylamide and a biopolymer and introducing the fluid to a subterranean formation wherein the polyacrylamide and biopolymer are selected to form the fluid with a longer foam half life and a higher viscosity than if only one polymer were selected. Embodiments of the invention relate to a method for treating a subterranean formation, comprising forming a fluid comprising polyacrylamide and a biopolymer and introducing the fluid to a subterranean formation wherein the polyacrylamide does not alter biopolymer crosslinking.

FIGURES

FIG. 1 is a chart that shows foam half life and stability of 3.1 wt % acrylamide sodium acrylate copolymer (A1) with varying concentrations of duitan gum and ammonium C6-C10 alcohol ethoxysulfate surfactant.

FIG. 2 is a chart that shows selecting the foaming agent (Formulation No. 1 —3.1% A1+Acetic acid+crosslinker)+Foaming surfactant.

FIG. 3 is a chart that shows formulation No. 2 (5.2% A1+Ac+substituted acrylamide polymer).

FIG. 4 is a chart that shows different acrylamide sodium acrylate copolymer (A1) wt % concentrations—3.1%, 5.2% and 6%.

FIG. 5 is a chart for formulation No. 2 (5.2% A1+Ac+substituted acrylamide polymer)+0.5 (vol) % surfactant D+0.5 (vol) % surfactant I.

FIG. 6 is a chart of polymer solutions foamed with 0.5% surfactant D.

FIG. 7 is a chart of formulation No. 1 (3.1% A1+Ac+substituted acrylamide polymer+G1) with different hydration time after adding G1 polymer.

FIG. 8 is a chart of formulation No. 1 with different concentration of diutan gum*.

FIG. 9 is a chart of rheology behavior on Fann-35 as a function of shear rate.

FIGS. 10A and 10B show G1 polymer effect on the setting time performance of acrylamide sodium acrylate copolymer and substituted acrylamide polymer fluids.

FIG. 11 is a series of photos showing in situ static foam pictures taken from left to right at 7 minutes, 1 hour and 3 hours in the view cell.

DESCRIPTION

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

The statements made herein merely provide information related to the present disclosure and may not constitute prior art, and may describe some embodiments illustrating the invention.

Embodiments of the invention create a seal in the gas producer zone to trap the gas, trying to avoid or minimize the damage in the crude oil producer zone. Foaming a polyacrylamide-based water control system, becomes one of the best alternative to propose. However, as lab testing has shown over time, polymers by themselves are not capable to maintain a stable foam before reaching the setting time of the system.

For that reason, after an extensive number of tests it has been found that the addition of a biopolymer to the hydrated polyacrylamide considerably increases the gel viscosity and the foam half life without affecting the performance of the system before curing.

The polyacrylamide may include polyacrylamide, grafted polyacrylamide, modified polyacrylamide, polyacrylamide hybrids, hydrophobic polyacrylamide, hydrophilic polyacrylamide, acrylamide sodium acrylate copolymer, and/or any combination thereof. In some embodiments, the polyacrylamide is selected for its molecular weight. In some embodiments, the polyacrylamide has a molecular weight of about 5 to about 15 mM. In some embodiments, the polyacrylamide has a molecular weight of about 200 to about 500K.

The biopolymer may include diutan xanthan, guar and/or a combination thereof.

In some embodiments, the biopolymer crosslinking is not altered by the presence of the polyacrylamide. That is, the fluid has similar viscosity or other rheological properties it would have if no polyacrylimide.

In our lab, some tests have been carried out to evaluate the feasibility of foaming the sealing gel system, which surges as one of the best ways for placement of the sealing system in the gas producer zone. The foamed gel consists of a crosslinked polyacrylamide solution—in both the rigid and flowing versions—plus a surfactant, foamed in a mixer at high-shear rate. The foamed gel is created by means similar to those used for aqueous foam generation, where the major difference between foamed gels and aqueous foams is that the external phase of the foamed gel crosslinks, greatly enhancing the mechanical stability of the foam system. According to lab tests, the polyacrylamide maintains the foam stable for short time, so it becomes necessary the addition of a polymer that aids in increasing the foam half life. Through a couple of lab tests, it was found that polymer of different identity such as guar gum is capable of increasing the foam half life by increasing the viscosity of the crosslinked polyacrylamide solution without affecting the performance of the setting time of the system. So far, on the flowing gel, it has been observed that the flowing gel is more robust when the guar gum is added into the crosslinked polyacrylamide solution.

One major problem of gas shut off is the placement of crosslinked polyacrylamide—such as acrylamide sodium acrylate copolymer and a substituted acrylamide polymer gel is ensuring that the gel is injected into and stays in the gas-bearing zone, until set. For this reason, stable foam is required which requires the optimization of the foam half life and foam quality to allow the system to set and prevent it slumping into the pay zone. It has proved difficult to create stable foam using nitrogen with a polyacrylamide fluid and conventional foaming agents. However, by adding a second polymer to the fluid it is possible to greatly increase the foam half life and the viscosity of the polyacrylamide solution. This is considered to be the result of the second polymer (guar or a biopolymer) greatly increasing the low shear apparent viscosity of the fluid. The increased low shear viscosity indicates a synergy between the polyacrylamide and the second polymer (Table 1 and 2).

TABLE 1
Viscosity and foam half life of Acrylamide Sodium Acrylate Copolymer
(A1) with and without the addition of Guar (G1).
	Fluid Composition - Viscosity (cP)
		3.1 wt %		5.2 wt
		A1 +		% A1	0.1
	3.1 wt	0.2 wt	5.2% wt	0.15 wt	wt %	0.2 wt
Shear Rate	% A1	% G1	A1	% G1	G1	% G1
5.1 sec−1	50	400	200	500	~	~
(cP)
10.2 sec−1	50	300	150	450	~	50
(cP)
170 sec−1	36	126	150	279	6	18
(cP)
511 sec−1	36	91	133	211	4	12
(cP)
Foam Half	15′	82′	36′31″	69′	13′43″	28′14″
Life

TABLE 2
Viscosity using Acrylamide Sodium Acrylate Copolymer
(A1) with Diutan gum and Guar (G1) polymer
	Apparent viscosity
	5.1 sec-	10.2 sec-	170 sec-	511 sec-
	1 (cP)	1 (cP)	1 (cP)	1 (cP)
3.1 wt % A1	50	50	36	36
3.1 wt % A1 + 0.2 wt % Guar	400	300	126	91
3.1 wt % A1 + 0.7 wt %	2800	1600	198	115
Diutan gum
3.1 wt % A1 + 0.42 wt %	1400	800	138	90
Diutan gum
3.1 wt % A1 + 0.25 wt %	800	500	102	72
Diutan gum
0.42 wt % Diutan gum	1400	800	60	25
0.25 wt % Diutan gum	600	350	27	13

Foamed fluids comprised of A1 with Diutan gum have a foam half life greater than five (5) hours. The most stable foam being when there is the greatest degree of interaction between the two polymers (FIG. 1).

FIG. 1 shows the foam half life and stability of 3.1 wt % Acrylamide Sodium Acrylate Copolymer (A1) with varying concentrations of Duitan gum and Ammonium C6-C10 alcohol ethoxysulfate surfactant.

1. 0.7 wt % Duitan gum+0.5 vol % Ammonium C6-C10 alcohol ethoxysulfate surfactant

2. 0.7 wt % Duitan gum+1.0 vol % Ammonium C6-C10 alcohol ethoxysulfate surfactant

3. 0.25 wt % Duitan gum+0.5 vol % Ammonium C6-C10 alcohol ethoxysulfate surfactant

4. 0.42 wt % Duitan gum+0.5 vol % Ammonium C6-C10 alcohol ethoxysulfate surfactant

Laboratory testing on foam has shown that the waring blender is not the appropriate equipment for foam generation since the mixing is not uniform with the highest shear occurring at the bottom of the blender jar. For that reason, a Silverson mixer—L4RT model—was used for foam testing, since a more uniform foam mixture is achieved as the mixer paddle can move homogeneously throughout the foam.

The procedure for the foaming test is shown below:

Gel Mixing

• • Place the appropriate volume of water into the blender jar
  • Put the polyacrylamide (Acrylamide Sodium Acrylate Copolymer) into the waring blender and start mixing at around 2000 rpm for not less than one (1) hrs.
  • Add the activator and mix for 20 min and then add the crosslinker and continue mixing for about 20 minutes.
  • The guar gum polymer is added as last additive and mixed for 1.5 hrs or 2 hrs. Through lab testing it has been demonstrated that the right hydration of the polyacrylamide is very important for the development of the viscosity of the lineal gel and reproducibility of the results. Leaving the fluid (polymer+activator+crosslinker) overnight has been the best way to get better and reproducible results on the viscosity and the foam half life.
  • It is a good practice to measure the viscosity for each polyacrylamide and guar gum—crosslinked solution each time after mixing

Foaming Testing in the Laboratory

• • Take 100 mL (101 g) of the crosslinked polyacrylamide solution and put it into a graduated beaker (2000 mL) of polypropylene and agitate on a magnetic stirrer.
  • Add the surfactant-foaming agent at the desired concentration to the solution and mix for one (1) minute. In general, no foam is generated on this stage
  • Mix the solution at 4000 rpm for 3 minutes, using a Silverson Mixer—LV 4RTmixer. Try to get the full high shear around 15 sec±5 sec. The beaker should be rotated and moved up and down to ensure uniform mixing.
  • Measure and record foam height based on the graduated scale on the beaker
  • Measure the half-life of the foam (time required for 50 mL of the liquid to drain off the foam after the mixer is shut off) using a stop watch

Foam quality is calculated by using the following relationship:

Foam quality=(Foam Height−100 mL)/(Foam Height)*100%

Laboratory Results

TABLE 1
Formulations of the crosslinked Polyacrylamides - A1 (Acrylamide
Sodium Acrylate Copolymer) with (Hexamethylenetetramine)
crosslinker and Acetic acid (Ac) pH control
Fluid	Water	A1	crosslinker	Acetic acid
system	(%)	wt %	wt %	(Ac) wt %
1	96.2	3.1	0.21	0.21
2	94.0	5.2	0.21	0.21
3	90.1	6.0	0.21	0.21

TABLE NO. 2
Evaluation of Foaming surfactants and stabilizers with a Acrylamide
Sodium Acrylate Copolymer (A1) with Hexamethylenetetramine crosslinker and Acetic acid
(Ac) pH control
	A1(%) +		Vol.
Fluid	Ac +	Foaming surfactants (vol %)*	Initial	Foam		Quality of
system	Crossliner	and polymer stabilizers (wt %)*	Vol (cc)	Volume (cc)	Half-Life	Foam (%)
1	3.1	D (0.5%)	100	650	15′	84.6
2	3.1	D (1%)	100	1000	17′	90.0
3	3.1	D (2%)	100	1220	16′07″	91.8
4	3.1	AEP (0.5%)	100	800	15′51″	87.5
5	3.1	AEP (1%)	100	1180	16′15″	91.5
6	3.1	AEP(0.75% + D (0.25%)	100	1180	16′00″	91.5
7	5.2	D (0.5%)	100	320	36′31″	68.8
8	5.2	D (1%)	100	550	34′00″	81.8
9	5.2	B (1%)	100	550	31′45″	81.8
10	5.2	B (2%)	100	250	18′12″	60.0
11	5.2	D (1%) + I(1%)	100
12	5.2	D (0.5%) + I(0.5%)	100	350	36′23″	71.4
13	5.2	AEP(0.5%) + I(0.5%)	100	375	26′00″	73.3
14	5.2	D (0.5%) + I(0.5%) + 0.15 wt % G1		300	69′27″	66.7
15	5.2	D (0.5%) + I(0.5%) + 0.05 wt %	100	320	53′00″	68.8
		G1
16	6	D (0.5%)	100	300	50′00″	66.7
17	3.1	D (0.5% + I(0.5%) + 0.24 wt % G1	100	300	73′43″	66.7
18	3.1	0.24 wt % G1 + 0.5% D	100	375	82′31″	73.3%
19	3.1	Same as #18 @ 180° F.	100	375	37′09″( )	73.3%
20	—	0.12 wt % G1 + 0.5% D	100	1150	12′43″	91.3
21	—	0.12 wt % G1 + 1% D	100	1200	11′38″	91.7
22	—	0.24 wt % G1 + 0.5% D	100	1000	26′14″	90
23	3.1	Same as test #18 with 30 min	100	375	70′	73.3
		hydration G1
24	3.1	Same as test #18 13 hrs after	100	375	95′	73.3
		addition of G1
25	3.1	0.24 wt % G1 + 2% C	100	200	55′	50
26	3.1	0.24 wt % G1 + 5% C	100	300	171′	66.6
27	3.1	0.24 wt % G1 + 10% C	100	300	125′	66.6
28	3.1	0.24 wt % G1 + 1% D + 3% C	100	200	20′	50
29	3.1	0.24 wt % G1 + 1% MS + 1% D	100	280	37′	64.2
30	3.1	0.24 wt % G1 + 1% MS + 2% C	100	350	85′	71.4
31	3.1	0.24 wt % G1 + 1% F	100	300	65′	66.6
*Description of foaming surfactants and stabilizers used
AEF: Alcohol Ether Phosphate
A = Ethoxylated branched C11-14, C13-rich alcohols and Ethoxylated 4-nonylphenol
B = Cocamidopropyl Betaine
C = Dicoco Dimethyl Ammonium Chloride
D = Ammonium C6-C10 alcohol ethoxysulfate
E = Linear/Branched C11 Alcohol Ethoxylate (8 EO)
F = Amphoteric alkyl amine
G = Sodium tridecyl ether sulfate
H = Mixture of Ethoxylated alcohols
I = Mixture of Polyglycols, Oxyalkylates, and Methanol
MS = Mutual Solvent
G1 = Guar polymer
Testing with: water + 1% SA1 + 0.2% crosslinker + 1.8 vol % Phenyl Acetate + 0.3 vol % Ac + 5 gpl D
			Vol.	Foam H.
No.		Vol. Fluid1	Foam (cc)	Life	Foam Quality (%)
31		100	720	36′40″	86
32	Con 0.24 wt % G1	100	475	100′	78.9
(Hexamethylenetetramine) crosslinker and Acetic acid (Ac) pH control
indicates data missing or illegible when filed

SA1 Substituted Acrylamide Polymer—

Below are some graph that simplify the obtained results

The FIGS. 2 and 3, show that the foam is more stable with the Surfactant D and that it is not necessary to increase its concentration above 0.5 vol % FIG. 2: Selecting the foaming agent (Formulation No. 1 —3.1% A1+Acetic acid+crosslinker)+Foaming surfactant

FIG. 3: Formulation No. 2 (5.2% A1+Ac+substituted acrylamide polymer).

TABLE 3
here
	Fluid Composition - Viscosity (cP) fluid nucleus
	0.12 wt %
	G1 0.5%
	D surfactant	0.24 wt % G1 + 6.9% D
	5.2% A1	3.2% A1 +		80° F.	80° F.	71° C.
	3.1%	3.1%/A1 +	5.2%	0.18 wt %	0.05 wt %	6%		Formed		Formed	Formed
Shear Rate	A1	0.24 wt % G1	A1	G1	G1	A1	Lineal	fluid	Lineal	fluid	fluid
5.1 sec−1 (cP)	50	400	200	500	200	200	~	300	~	500	400
10.2 sec−1 (cP)	50	300	150	450	250	450	~	250	50	600	350
170 sec−1 (cP)	36	126	150	279	204	378	6	108	18	153	84
511 sec−1 (cP)	36	91	133	211	165	216	4	64	12	72	41
Foam Half Life	15′	82′	36′31″	69′	53′	30′	13′43″	~	28′14″	~	~
indicates data missing or illegible when filed

TABLE 4
here
							L400 + HE1		1 h	2 h	3 h	13 h
5.1 sec−1 (cP)	—	100	300	400	550	500	400	200	550	600	600	600
10.2 sec−1 (cP)	—	100	250	300	350	300	250	125	350	450	450	491
170 sec−1 (cP)	15	69	120	120	129	129	98	90	150	165	165	165
511 sec−1 (cP)	10	56	85		95	93	76	68	101		115	115
Foam IL-Life	—	—	—	—	—	—	—		—	—	—
indicates data missing or illegible when filed

FIG. 4 is a chart that shows different acrylamide sodium acrylate copolymer (A1) wt % concentrations—3.1%, 5.2% and 6%. Increasing the polyacrylamide concentration decreases foam quality but increases foam half life

FIG. 5 is a chart for formulation No. 2 (5.2% A1+Ac+substituted acrylamide polymer)+0.5 (vol) % surfactant D+0.5 (vol) % surfactant I. This shows increased concentrations improves foam stability bur decreases slightly the foam quality.

FIG. 6 is a chart of polymer solutions foamed with 0.5% surfactant D. Good foam quality and poor foam stability for both the linear gel with G1 (guar) and for A1(Acrylamide Sodium Acrylate Copolymer). However when both polymers (Acrylamide Sodium Acrylate Copolymer+Guar) are combined the foam stability increases.

FIG. 7 is a chart of formulation No. 1 (3.1% A1+Ac+substituted acrylamide polymer+G1) with different hydration time after adding G1 polymer.

FIG. 8 is a chart of formulation No. 1 with different concentration of diutan gum*.

FIG. 9 is a chart of rheology behavior on Fann-35 as a function of shear rate.

The hydration level of both polymers plays a very important role for foam stability. Better and more reproducible results are achieved when the polyacrylamide solutions is hydrated for extended period of time prior to adding the G1 guar polymer.

FIGS. 10A and 10B show G1 polymer effect on the setting time performance of acrylamide sodium acrylate copolymer and substituted acrylamide polymer fluids. No major change was seen. Reaching the hard Set Time of both system was faster upon addition of G1. Also, the gel looked more robust when G1 was included in the formulation.

Photos of 3.1 wt % Acrylamide Sodium Acrylate Copolymer and 1 wt % Acrylamide Sodium Acrylate Copolymer illustrate the performance.

Foaming Evaluation with Diutan Gum

Base fluid 3.1 wt % A1+0.21 wt % substituted acrylamide polymer+0.21 wt % Ac+0.5 vol % D

FIGS. 8 and 9 show how the rheology is depending of the polymer or polymer combination used. The +symbol mean that the fluid contains A1+substituted acrylamide polymer+Ac+Surfactant D at the concentration shown above. FIG. 8 shows results for Formulation No. 1 with different concentration of Diutan gum* and FIG. 9 shows results for Rheology behavior on Fann-35 vs Shear rate.

High foam stability with the addition of the Diutan gum. 5 hrs with not drainage observed.

• • *Concentrations of Diutan gum and surfactant
  • 1. Base fluid+0.7 wt % Duitan gum+0.5 vol % Ammonium C6-C10 alcohol ethoxysulfate surfactant
  • 2. Base fluid+0.7 wt % Duitan gum+1.0 vol % Ammonium C6-C10 alcohol ethoxysulfate surfactant
  • 3. Base fluid+0.25 wt % Duitan gum+0.5 vol % Ammonium C6-C10 alcohol ethoxysulfate surfactant
  • 4. Base fluid+0.42 wt % Duitan gum+0.5 vol % Ammonium C6-C10 alcohol ethoxysulfate surfactant

Setting Time of Acrylamide Sodium Acrylate Copolymer when Adding Diutan Gum

No much difference on the setting time with and without Diutan. However, the Diutan impart elasticity on the consistency of the system. The picture with Diutan shows how the bubbles are after the system reaches its hard set time, not fluid drainage.

Evaluation of Surfactants with Diutan Gum and a Acrylamide Sodium Acrylate Copolymer

Composition (Active Components) of Surfactants

Base fluid formulation: 3.1 wt % Acrylamide Sodium Acrylate Copolymer + 0.21 wt %
substituted acrylamide polymer + 0.53 wt % Acetic acid + Diutan gum variable
Test	Diutan	Foam		Vol. Initial	Foam		Foam Quality
No.	wt %	agent	% BVol	(cc)	Volume (cc)	Half-Life	(%)
1	0.8 gpb	D	0.5%	100	280	18 hrs = 0 cc	64
2	0.42 wt %	D	0.5%	100	355	5 hrs = 0 cc	71.8
						14 hrs = 47%
3	0.25 wt %	D	0.5%	100	390	5 hrs = 0 cc	74.4
						14 hrs = 67%
4	0.25 wt %	C	5%	100	300	2.5 hrs	66
5	0.25 wt %	C	2%	100	350	1 h45′	71.4
6	0.25 wt %	C	2% +	100	260	1 h15′	61.5
			MS
7	0.25 wt %	A	0.5%	100	170	—
8	0.25 wt %	A	2%	100	300	5 hrs = 30%	66
9	0.25 wt %	F	0.5%	100	220	6 hrs = 0 cc	54.5
10	0.25 wt %	F	2%	100	360	6 hrs = 25%	72.2
11	0.25 wt %	F	0.5%	100	350	6 hrs = 0 cc	71.4
12	0.25 wt %	B	0.5%	100	250	—	63.0
13	0.25 wt %	B	2%	100	490	5 hrs = 0	79.6
						7 hrs = 40%
14	0.25 wt %	B	1%	100	350	5 hrs = 0	71.4
						7 hrs = 30%
15	0.25 wt %	E	0.5%	100	180	—	44.4
16	0.25 wt %	G	0.5%	100	180	—	44.4
Base fluid formulation: 3.1 wt % Acrylamide Sodium Acrylate Copolymer + 0.21 wt %
substituted acrylamide polymer + 0.53 wt % Acetic acid + 0.25 wt % Diutan gum contaminated
with Cantarell Crude Oil
				Vol.		Foam
		Foam		Initial	Foam Volume	Quality
	Crude (%)	agent	% BVol	(cc)	(cc)	(%)	Half-Life
18	5	D	0.5%	100	390	74.4	20 min = 60%
19	5	F	2%	100	370	73.0	1.5 hrs = 45.2%
20	5	G	0.5%	100	370	73.0	6 hrs = 70%
							7 hrs = 68%
21	10	G	0.5%	100	370	73.0	2 hrs = 70.3
							4 hrs = 60.7
							5 hrs = 52.2
22	15	G	0.5%	100	340	70.6	4 hrs = 70.6
							5.5 hrs = 23
23	5	B	2	100	500	80.0	3 hrs = 78.4
							4 hrs = 58
24	10	B	1	100	350	71.4	0 hrs = 70.6
							6 hrs = 70.6
25	20	B	1	100	340	70.6	7 hrs = 70.6
							8 hrs = 62.5
A = Ethoxylated branched C11-14, C13-rich alcohols and Ethoxylated 4-nonylphenol
B = Cocamidopropyl Betaine
C = Dicoco Dimethyl Ammonium Chloride
D = Ammonium C6-C10 alcohol ethoxysulfate
E = Linear/Branched C11 Alcohol Ethoxylate (8 EO)
F = Amphoteric alkyl amine
G = Sodium tridecyl ether sulfate
H = Mixture of Ethoxylated alcohols

Foam Stability at Temperature

A fluid formulated as follows 3.1 wt % Acrylamide Sodium Acrylate Copolymer+0.7 wt % Diutan gum+1.0 vol % Cocamidopropyl Betaine was evaluated further in a circulating foam loop at 100° C. using nitrogen. The hexamethylenetetramine was not included to prevent gelation during the test. The foam was formulated at a quality of 72%. A constant shear rate of 100 s⁻¹ was maintained throughout the test except for three shear ramps where the shear rate was reduced to 75, 50 25 and then increased to 50, 75 and 100 s⁻¹. Table 1 shows the calculated power law parameters, for the foam versus elapsed time. Clearly the foam maintains its viscosity and its shear thinning properties with only minor changes over the test time of 3.5 hours. The rheology trace is included in FIG. 11. Pictures of the foam segregated in a view cell are shown in FIG. 11. In situ static foam pictures taken from left to right at 7 minutes, 1 hour and 3 hours in the view cell. FIG. 11. In situ static foam pictures taken from left to right at 7 minutes, 1 hour and 3 hours in the view cell. No drainage was seen during the 3.5 hour test time. No drainage was seen during the 3.5 hour test time.

Some coarsening of the foam is evident, but the foam has no drainage over the 3.5 hour test time.

TABLE 1
Power law parameters for foam test
Elapsed Time,	Temperature,
hr:min:sec	° C.	n′	K′,	R2
1:14:32	100.3	0.435	0.0120	0.977
2:28:36	101.2	0.449	0.0974	0.987
3:25:40	101.3	0.456	0.0888	0.992

The preceding description has been presented with reference to some illustrative embodiments of the Inventors' concept. Persons skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structures and methods of operation can be practiced without meaningfully departing from the principle, and scope of this invention. Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.

Furthermore, none of the description in the present application should be read as implying that any particular element, step, or function is an essential element which must be included in the claim scope: THE SCOPE OF PATENTED SUBJECT MATTER IS DEFINED ONLY BY THE ALLOWED CLAIMS. Moreover, none of these claims are intended to invoke paragraph six of 35 USC §112 unless the exact words “means for” are followed by a participle. The claims as filed are intended to be as comprehensive as possible, and NO subject matter is intentionally relinquished, dedicated, or abandoned.

Claims

1. A method for treating a subterranean formation, comprising:

forming a fluid comprising polyacrylamide and a biopolymer; and

introducing the fluid to a subterranean formation;

wherein the polyacrylamide and biopolymer are selected to form the fluid with a longer foam half life and a higher viscosity than if only one polymer were selected.

2. The method of claim 1, wherein the polyacrylamide comprises polyacrylamide, grafted polyacrylamide, modified polyacrylamide, polyacrylamide hybrids, hydrophobic polyacrylamide, hydrophilic polyacrylamide, acrylamide sodium acrylate copolymer, and/or any combination thereof.

3. The method of claim 1, wherein the polyacrylamide is selected for its molecular weight.

4. The method of claim 3, wherein the polyacrylamide has a molecular weight of about 5 to about 15 MM.

5. The method of claim 3, wherein the polyacrylamide has a molecular weight of about 200 to about 500K.

6. The method of claim 1, wherein the biopolymer is diutan.

7. The method of claim 1, wherein the biopolymer is xanthan.

8. The method of claim 1, wherein the biopolymer is guar.

9. The method of claim 1, wherein the biopolymer crosslinking is not altered by the presence of the polyacrylamide.

10. A method for treating a subterranean formation, comprising:

forming a fluid comprising polyacrylamide and a biopolymer; and

introducing the fluid to a subterranean formation;

wherein the polyacrylamide does not alter biopolymer crosslinking.

11. The method of claim 10, wherein the polyacrylamide comprises polyacrylamide, grafted polyacrylamide, modified polyacrylamide, polyacrylamide hybrids, hydrophobic polyacrylamide, hydrophilic polyacrylamide, acrylamide sodium acrylate copolymer, and/or any combination thereof.

12. The method of claim 10, wherein the biopolymer is diutan.

13. The method of claim 10, wherein the biopolymer is xanthan.

14. The method of claim 10, wherein the biopolymer is guar.

15. The method of claim 10, wherein the polyacrylamide is selected for its molecular weight.