Unlocking the potential of graphene oxide as an early strength enhancer for geopolymer well cement in extreme downhole environment

Figures & data

Table 1. Chemical requirement for fly ash Class C and F as per ASTM C618-19 (25).

Chemical compound	Class F	Class C	Fly ash sample
Silicon dioxide + aluminum oxide + iron oxide, minimum %	50	50	64.1
Calcium oxide (%)	< =18.0	> 18.0	16.3
Sulfur trioxide (maximum %)	5.0	5.0	1.6

Table 2. Test matrices determine optimal sodium hydroxide molarity and sodium hydroxide to sodium silicate ratio.

Formulation	Sodium hydroxide molarity (M)	Ratio of sodium hydroxide to sodium silicate
1	6.5	2.30
2	5.0	0.50
3	8.0	2.00
4	6.5	0.20
5	8.0	0.50
6	6.5	1.25
7	6.5	1.25
8	5.0	2.00
9	8.6	1.25
10	6.5	1.25
11	4.4	1.25
12	6.5	1.25
13	6.5	1.25

Figure 1. Pressurized curing chamber.

Figure 2. Result of Compressive Strength Test of Sodium hydroxide Molarity and Ratio of SH/SS from the formulation by using Design Expert.

Figure 3. 2D contour represents the compressive strength results of GO concentration and sodium hydroxide molarity.

Table 3. Compressive strength result for Phase 1.

Formulation	Sodium Hydroxide Molarity (M)	Alkaline Activator Ratio	Compressive Strength (psi)
1	6.5	2.30	3,098
2	5.0	0.50	2,279
3	8.0	2.00	1,432
4	6.5	0.20	2,110
5	8.0	0.50	3,212
6	6.5	1.25	2,176
7	6.5	1.25	2,375
8	5.0	2.00	3,663
9	8.6	1.25	1,304
10	6.5	1.25	2,098
11	4.4	1.25	3,336
12	6.5	1.25	2,158
13	6.5	1.25	2,165

Table 4. Test matrices to determine optimal GO concentration.

Formulations	Sodium hydroxide molarity (M)	Graphene oxide concentration (% bwof)
1	3.0	2.0
2	4.0	1.1
3	4.0	1.1
4	2.6	1.1
5	4.0	2.4
6	4.0	1.1
7	3.0	0.2
8	5.0	2.0
9	4.0	0.0
10	4.0	1.1
11	4.0	1.1
12	5.4	1.1
13	5.0	0.2

Figure 4. 3D surface contour represents the variation of GO concentration and sodium hydroxide molarity to compressive strength.

Table 5. Compressive strength result for Phase 2.

Formulations	Sodium hydroxide molarity (M)	Graphene oxide concentration (%. bwof)	Compressive strength (psi)
1	3.0	2.0	2,707
2	4.0	1.1	2,414
3	4.0	1.1	2,489
4	2.6	1.1	1,257
5	4.0	2.4	2,031
6	4.0	1.1	2,563
7	3.0	0.2	1,738
8	5.0	2.0	1,578
9	4.0	0.0	1,145
10	4.0	1.1	2,141
11	4.0	1.1	2,385
12	5.4	1.1	8,94
13	5.0	0.2	2,463

Figure 5. Desirability and compressive strength chart to find the optimum formulation.

Table 6. Prediction of compressive strength at optimal sodium hydroxide molarity and graphene concentration from Design Expert.

Solution	Predicted mean	Predicted median	Std Dev	SE mean	95% CI low for mean	95% CI high for mean
Compressive Strength	2693.82	2693.82	143.947	118.941	2388.07	2999.57

Table 7. Rheology of the reference design at surface temperature and 60 °C.

RPM	Ambient temperature			60 °C
	Ramp down	Ramp up	Ratio	Ramp down	Ramp up	Ratio
300	48	48	1	35	35	1
200	34	35	1.03	27	29	1.07
100	20	20	1	19	19	1
6	5	5	1	8	8	1
3	4	4	1	7	7	1

Table 8. Rheology of the optimum design (Formulation OP 1) at surface temperature and 60 °C.

RPM	Ambient temperature			60 °C
	Ramp down	Ramp up	Ratio	Ramp down	Ramp up	Ratio
300	47	47	1	27	27	1
200	28	29	1.04	21	22	1.05
100	18	19	1.06	16	17	1.06
6	5	5	1	8	8	1
3	4	4	1	7	7	1

Table 9. Filtrate volume of the reference and optimum design at 60 °C.

Reference design (ml)	Optimum design (ml)
951.5	734.2

Table 10. Thickening time for reference and optimum designs at 90 °C and 3,000 psi.

Bearden consistency (Bc)	Reference design	Optimum design
40	0:41	1:03
70	2:37	3:08
100	2:57	3:25