Reducing the Salinity of the Produced Water from Oil Field Using Activated Carbon Extracted from Waste Date Kernel

spontaneous imbibition test for sandstone core


‫التمور‬ ‫نواة‬ ‫من‬ ‫المستخرج‬ ‫المنشط‬ ‫الكربون‬ ‫باستخدام‬ ‫المياه‬ ‫ملوحة‬ ‫لتقليل‬ ‫حديثة‬ ‫دراسة‬
After more than a century of petroleum production, different of petroleum fields are approaching the ends of their residual oil saturation.The residual of an oil usually undergoes three periods where different techniques are used to increase the crude oil production at maximum levels which are primary, secondary and EOR (Zhang, Gao, and Xue 2020; Elsharafi 2018; Samba and SYIHAB, n.d.; Green and Willhite 1998).These techniques are mainly aimed to serve a common purpose which is reducing the residual oil saturation which results in improvement of the displacement efficiency and improvement of the ultimate oil recovery.One of those techniques is low salinity water injection, many challenges about the low water salinity in the order to reduce the salinity with low cost.The challenges started at 1967 by Bernard, the study has presented about improvement in the recovery of oil by low or reduced salinity water (Bernard 1967).In 2000, Tchistiakov has presented about the interaction between the cation and clay which it is related to the low water salinity.In this study, only some cations are attached to the clay surface as an adsorbed layer, while others are free, forming a diffuse ionic layer, some distance away from the clay surface.The balance between thermal motion of the cations and electrostatic attraction can control the distribution and concentration of the free cation (Tchistiakov 2000).The low salinity challenges continuously until 2004.Where, Webb was presented about the low water salinity and has proved that the low water salinity can reduce the residual oil saturation.Thus, the oil recovery has increased (Webb, Black, and Al-Ajeel 2004).Consequently in 2008, Lager and others have shown that the oil molecules are attract on surface due to the clay negative charge by divalent cations.Where, the positive charges (ions) in calcium (Ca2+) or magnesium (Mg2+) helps to hold the oil molecules on the clay particles.During the low saline water injection, the monovalent ions, exchange with the divalent cations attract the oil droplet.Thus, the oil droplet will be free to move forward (Lee et al. 2010).Additional study in 2010 by Lee and others.Where, they have presented about the electric double layer, they noticed that the electric double layer has an outer diffuse layer (negative ions) and an inner adsorbed layer (positive ions).During the low salinity water containing less ions, the double layer is less compact, and the oil release from the clay surface is inhibited (Lee et al. 2010).Also in 2010, Austad and others has noticed that the negative charge on the clay due to role of clay minerals often characterized as cation exchange material (Austad, RezaeiDoust, and Puntervold 2010).Based on the literature, many challenges are at stake for low salinity projects.In this paper, we have moved step more and check how to find a way to reduce the salinity of formation water with economic method.Thus, the activated carbon extracted from date kernel has been decided to be used in this study.Generally, the date kernel has been used as treatment for the oil fields in 2021 by Udeagbara and others (Udeagbara et al. 2021).However, the date kernel used as a fiber material not as activated carbon.This study consider as the first study that used the activated carbon extracted from waste date kernel, in order to reduce the salinity of the formation water in the oil fields.The overall project plan of the present work is shown in figure 1

Second Stage of Activated Carbon Preparation
The non-activated carbon is activated by using a chemical such as zinc chloride (ZnCl2), sulfuric acid (H2SO4), and sodium hydroxide (Na OH).The second stage of activated carbon preparation was carried out as the following: (i) A (10 g) of non-activated charcoal sample was add to a mixture of (H2SO4 (3N) and the ZnCl2 (3N) in 50 ml of distilled water).(ii) A non-activated carbon mixture was exposed to boiling temperature (100Cº) for a period time of 3 hours.Thus, the activated carbon was formed.(iii) The formed activated carbon was filtered (iv) The collected sample of activated carbon was washed using a distilled water for a several times and after each washing process, a pH was measured using a pH measurement device.The required pH value was 7. (v) In order to dry, the activated carbon, the samples were inserted in drying oven at temperature of (105 ºC) for a period time of 24 hours.The activated carbon samples were ready for a reservoir water treatment.

2.2
Core Samples Preparation The Core Samples Preparation has been done typically to the following procedures: 1. Clean all the samples.2. Drying the samples and weight each sample.3. Saturate the cores with distilled water and weight each sample.4. Measure the bulk size of each sample.5. Measure the pore size.6. Measure porosity.7. Drying the core sample and weight each sample again.8. Saturated cores with oil and weight each core.9. Measure the OOIP for each core.

Pore Volume of Sandston Core Samples Results
The volume of fluids type, which inter to pore volume of sandstone reservoir core samples were calculated.Table 1 showing the results of pore volume with reservoir water.Table 2 showing the results of pore volume with reservoir oil.

Bulk Volume of Sandstone Core Sample Results
The bulk volume of sandstone reservoir core samples at different volumes were calculated using the cylinder volume base.Table 3 shows the bulk volume of sandstone core samples.

Porosity of Sandstone Core Sample Results
The porosity was obtained by dividing the pore volume by the bulk volume.Table 4 show the porosity of sandstone core samples.
According to the obtained results, the maximum porosity of core sample in reservoir was 19.6% at sample C-103.

Original Oil in Place (OOIP) in Sandstone Core Results
Table 5 shows original oil in place (OOIP) of sandstone core samples, the cores samples were saturated with oil with density of 0.797 g/cc.
Based on the obtained results, the maximum OOIP of sandstone core sample was 11.29 cc at sample C-103.

Reservoir Water Analysis after the Treatment Process
Table 7 shows the results of reservoir water analysis after the treatment process.The activated carbon proved it is ability to reduce the salinity until 2000 ppm.The particles size 0.125 mm was given the lowest salinity.The synthesis activated carbon has ability to adsorb the dissolved salts.The percentage of activated carbon also play an important factor to adsorb ability.The effect of activated carbon on adsorption of dissolved salts depends on size of activated carbon.However, the activated carbon has negative charge and based on Coulomb law, the static electric forces for charges that has different charges are attract with each other while the static electric forces that has same charges repel each other.Thus, two negative charges repel one another, while a positive charge attracts a negative charge.The attraction or repulsion acts along the line between the two charges.Thus, the negative charges will adsorb the positive charges in the water solution.

Spontaneous Imbibition Test 3.3.1 Effect of Formation Water, Time, and Temperature on the Oil Recovery of Core Samples
The spontaneous imbibition test was done by the formation water (untreated water), and the used sample was (C-101).At the beginning the temperature was about (27°C) for a period time of 24 hours, the oil extraction rate (OER) was (0.24%).By increasing the temperature to (45°C) for a period of 72 hours, (OER) was increased to (10 %).
The test was carried out for another 72 hours at 55 o C, the recovery factor was at (22.31 %).Finally, the temperature was raised to (70 °C) for 72 hours and (OER) was (46.8 %). Figure 3 shows the effects of reservoir water (untreated) on the oil recovery for sandstone core samples as function of time and temperature.The spontaneous imbibition test was done by the reservoir water treated by activated carbon with size of 0.250 mm, and the used sample was (C-102).At the beginning, the temperature was about (27 °C) for a period time of 24 hours and the oil extraction was about 0.14 %.Continuously, the oil extraction rate (OER) was 16 % by increasing the temperature to (45 °C) for a period of 72 hours.Then the test was carried out for addition 72 hours at the 55 0 C, the OER was (34.13 %).Finally, the temperature was raised to (70 °C) for 72 hours and (OER) was (68.87%).Figure 4 shows the effects of reservoir water treated by activated carbon (0.250 mm) on the oil recovery for sandstone core samples in relation to time and temperature.
(ii) Second Scenario; Reservoir Water was Treated by Activated Carbon (0.125 mm) The spontaneous imbibition test was done by the reservoir water treated by activated carbon with size of 0.125 mm, and the used sample was (C-103).At the beginning, the temperature was about (27 °C) for a period time of 24 hours.Thus, the oil extraction rate (OER) was (0.40 %).By increasing the temperature to (45°C) for a period of 72 hours, the OER was increased to (20%).Then the test was carried out for more addition 72 hours at 55o C, in this case the OER was (38.13 %).Finally, the temperature was raised to (70 °C) for 72 hours and the OER was 70.4 %. Figure 5 shows the effects of reservoir water (treated) on the oil recovery for sandstone core samples as function to time and temperature.The spontaneous imbibition test was carried out by the reservoir water treated by activated carbon with size of 0.063 mm, and the used sample was (C-104), starting temperature was at (27 °C) for a period time of 24 hours, the OER was (0.32 %).Increasing the temperature to (45 °C) for a period of 72 hours, the OER was 10.01 %, then the test was carried out for addition 72 hours at the same temperature, in this case the OER was 24.01 %.Finally, the temperature was raised to 70°C for 72 hours and the OER was 53.10 %. Figure 6 shows the effect of reservoir water (treated) on the oil recovery for sandstone core samples in relation to time and temperature.

Comparison between the Effects of Oil Recoveries (Sandstone Rocks)
The spontaneous imbibition test of sandstone samples was performed by untreated reservoir water and treated reservoir water at different volumes of activated carbon, using different temperatures and different interval times.Figure 7 shows the comparison in terms of oil extraction.The extraction of oil in spontaneous imbibition test using the sample (C-101) which was carried out using a natural reservoir water (untreated reservoir water) with low rates despite the slight, the recovery was increased gradually when a different temperature was applied.The maximum oil extraction reached (46.8 %) at temperature (70 °C).Using the smaller size of 0.063 mm of activated carbon on the sample (C-104) gave the low recovery than other activated carbon sizes.However, the Activated Carbon (0.125 mm) has given the highest recovery factor compared with other scenarios.In additional, all the treated water setarious have given better recovery factor compared with untreated formation water.(ii) Activated carbon with a volume of (0.125 mm) has the highest efficiency as it gave the highest rate of oil recovery compared to volume (0.250 mm).While volume of (0.063 mm) had the lowest oil recovery rate; (iii) The overall conclusion is that the reservoir treated water with activated carbon is slightly better compared to the natural reservoir water (untreated reservoir water) in terms of oil recovery.

Figure 1 .
Figure 1.The Overall Project Plan 2. Experiments Procedure 2.1 Activated Carbon Preparation 2.1.1.First Stage of Activated Carbon Preparation (i) Date kernels were washed several times using distilled water until the color of the water becomes clear as shown in figure 2.a.(ii) Dates kernels were placed in burning oven at 400ºC for a period of 24 hours.The kernels were completely burned and their color were changed to dark black as shown in figure 2.b. (iii) After that, the Dates kernels were grounded into fine powered parts as shown in figure 2.c.(iv) The grounded kernels were washed several times using distilled water as shown in figure 2.d.(v) The grounded particles were put in drying oven at 105ºC for a period of 24h as shown in figure 2.e.(vi) After that, the grounded powders were classified into three different size (0.250, 0.125, 0.063) mm, the resulted samples as shown in figure 2.f were a non-activated carbon.

Figure 2 .
Figure 2. Carbon Activation First Stage

Figure 3 .
Figure 3. Effects of Reservoir Water (Untreated) on Oil Recovery of Sandstone Core Samples Related with Time and Temperature 3.4.2Effect of Treated Formation Water, Time, and Temperature on the Oil Recovery of Core Samples (i) First Scenario; Reservoir Water was Treated by Activated Carbon with size 0.250 mm.The spontaneous imbibition test was done by the reservoir water treated by activated carbon with size of 0.250 mm, and the used sample was (C-102).At the beginning, the temperature was about (27 °C) for a period time of 24 hours and the oil extraction was about 0.14 %.Continuously, the oil extraction rate (OER) was 16 % by increasing the temperature to (45 °C) for a period of 72 hours.Then the test was carried out for addition 72 hours at the 55 0 C, the OER was (34.13 %).Finally, the temperature was raised to (70 °C) for 72 hours and (OER) was (68.87%).Figure4shows the effects of reservoir water treated by activated carbon (0.250 mm) on the oil recovery for sandstone core samples in relation to time and temperature.(ii) Second Scenario; Reservoir Water was Treated by Activated Carbon (0.125 mm) The spontaneous imbibition test was done by the reservoir water treated by activated carbon with size of 0.125 mm, and the used sample was (C-103).At the beginning, the temperature was about (27 °C) for a period time of 24 hours.Thus, the oil extraction rate (OER) was (0.40 %).By increasing the temperature to (45°C) for a period of 72 hours, the OER was increased to (20%).Then the test was carried out for more addition 72 hours at 55o C, in this case the OER was (38.13 %).Finally, the temperature was raised to (70 °C) for 72 hours and the OER was 70.4 %.Figure5shows the effects of reservoir water (treated) on the oil recovery for sandstone core samples as function to time and temperature.

Figure 4 .
Figure 4. Effects of Reservoir Water Treated with Activated Carbon (0.250 mm) on Oil Recovery of Sandstone Core Samples Related with Time and Temperature.

Figure 5 .
Figure 5. Effects of Reservoir Water Treated with Activated Carbon (0.125 mm) on Oil Recovery of Sandstone Core Samples Related with Time and Temperature.(iii)Third Scenario; Reservoir Water was Treated by Activated Carbon (0.063 mm) The spontaneous imbibition test was carried out by the reservoir water treated by activated carbon with size of 0.063 mm, and the used sample was (C-104), starting temperature was at (27 °C) for a period time of 24 hours, the OER was (0.32 %).Increasing the temperature to (45 °C) for a period of 72 hours, the OER was 10.01 %, then the test was carried out for addition 72 hours at the same temperature, in this case the OER was 24.01 %.Finally, the temperature was raised to 70°C for 72 hours and the OER was 53.10 %.Figure6shows the effect of reservoir water (treated) on the oil recovery for sandstone core samples in relation to time and temperature.

Figure 6 .
Figure 6.Effects of Reservoir Water Treated with Activated Carbon (0.063 mm) on Oil Recovery of Sandstone Core Samples Related with Time and Temperature

Figure 7 .
Figure 7.Comparison between Oil Recoveries for Sandstone Cores.

4 .
Conclusions and Future Recommendation 4.1 Conclusions (i) The oil recovery rates are highly related to the applied temperature, meaning that the oil recovery rates are directly proportional to the temperature.

1 Reservoir Water Analysis Before the Treatment ProcessTable 6 .
Shows the results of reservoir water analysis before the treatment process.The formation salinity was at 2400 ppm.