Investigation of the effect of the Reservoir Rock Compressibility on Oil Recovery Factor during Gas Injection

A type of EOR, secondary production includes water flooding and gas injection. Normally, gas is injected into the gas cap and water is injected into the production zone to sweep oil from the reservoir. A pressure-maintenance program can begin during the primary recovery stage


‫الغاز‬ ‫حقن‬ ‫أثناء‬ ‫الزيت‬ ‫استخالص‬ ‫عامل‬ ‫على‬ ‫المكمنية‬ ‫الصخور‬ ‫انضغاطية‬ ‫تأثير‬ ‫دراسة‬
The downward displacement of oil by gas injection in a reservoir result in very high oil recovery efficiencies [1].The success of this technique stems from the continuity of the oil phase provided by the bulk films of oil in all pore space invaded by the gas under conditions of positive oil spreading coefficients and the gravity stabilized oil bank moving toward the production well.Gas injection is a common EOR method for increasing oil recovery factor.It is an economical method, especially in cases where the injection gas for such gas injection project is easily available [2].Gas injection has become one of the most investigated methods for enhanced oil recovery in unconventional reservoirs.[3].In the common methods of water and gas injection, high and unsuitable mobility ratio within the injected fluid and the oil in the reservoir leads to viscose fingering and reduction of sweep efficiency [5].Pressure maintenance by gas injection in gas cap is one of the well-established methods for improving the ultimate recovery [4].Hydrocarbon gas injection is one of the major EOR methods.Hydrocarbon gas has some similar properties with the oil in reservoir, which has no damage to the formation [6].Normally, gas is injected into the gas cap and water is injected into the production zone to sweep oil from the reservoir as shown in the figure 1.A pressure-maintenance program can begin during the primary recovery stage, but it is a form or enhanced recovery.

Fig. 1: Gas Injection & Water Injection Research Objectives:
The objective of this study is: 1.The main objective of this project is to investigating the effect of the reservoir rock compressibility on oil recovery factor during gas injection.2. By using ECLIPES Software program, we model the data and find out the best prediction of gas injection that is suitable for the available data and field.

Research Problem Statement:
The problem statement of this study is: 1.As the reservoir produces oil and gas under primary conditions, which lowers the pressure of the reservoir.2. A gas injection is required to reenergize or "pressure up" the reservoir.
Eclipse Software: It has been recognized that an efficient way of understanding and possibly resolving these problems arise on this study is by using a reservoir simulation which is ECLIPSE.Reservoir simulation is a combination of physics, mathematics, reservoir engineering and computer programming.It is to develop a tool to predict reservoir performance under various operating conditions.

RESERVOIR PROPERTIES:
Relative Permeability: Figure 2 and 3 show data obtained from a laboratory test conducted on a reservoir core saturated with crude oil and initial connate water.The crude is displaced from the core by immiscible gas and water.In reservoir simulation using a black oil simulator, the laboratory-generated relative permeability must be adjusted to account for the interaction and mixing that are taking place between the injected gas and oil.table shows that the reference depth of the well is 3280, and through it the pressure and temperature of the well are measured.The contact of water with oil 3937, and it is defined as the highest depth in the reservoir and the depth of the oil.The contact of water with oil 3937, and it is defined as the highest depth in the reservoir and the depth of the oil.Gas in oil 3280, and it is defined as the minimum level in the tank, its contact and depth.The initial tank temperature is 70 degrees.Reservoir Rock Properties: The reservoir rock contains pores and throats, creating flow path and an accumulating system for hydrocarbon and also consist of a sealing mechanism for prohibiting hydrocarbon penetration to surface layers.Table 3 shows the reservoir properties of this reservoir.Field Wells: Table 4 shows the number of wells that have been drilled, which were seven production wells and three gas injection wells.The first well was drilled in 2022 and the last well was drilled in 2024.In August 2024, gas injections began.

RESERVOIR MODEL:
Well Location Model: Figure 4 shows the distribution of the locations of the injection wells and the production wells.
Initial Gas Saturation Map: Figure 5 shows the percentage of gas saturation from the lowest value to the highest value in the first layer.Where the least saturation was 12% and the most saturation was 63%, which indicates the percentage of gas saturation before production.
Initial Oil Saturation Map: Figure 6 shows the percentage of oil saturation from the lowest value to the highest value.Where the least saturation was 24% and the most saturation was 76%, and this explains the percentage of oil saturation before production in the first layer.5 shows the start date of production for seven wells, the beginning of production from 1-11-2022 to 1-5-2024, and the end of production for seven wells on 11-12-2060.Field Oil and Gas Production Rate at Primary Recovery: Figure 8 shows the amount of oil produced from 2022 to 2060 through several wells.The figure shows that the x-axis represents the time from 1-11-2022 to 11-12-2060, and the y-axis represents the amount of oil production per day for seven wells.We notice from this figure that the amount of increased production decreases after a period of time.Also, Figure 8 shows the amount of gas production in the reservoir in X axis that represents the time from 1-1-2022 to 1-1-2060, and the y-axis represents the amount of gas production in the field that is 62000 MSCF\DAY.Gas Injection: Table 6 shows the amount of gas injection in the field, where then choose 12 cases to find out the best gas injection rate, case #1, then inject 1500000 SCF/DAY, in case #12, then inject 18,000,000 SCF/DAY for each injection well.Through these tests, the best gas injection rate is known.into the injection wells Field Oil Production Rate at Gas Injection: This figure shows the amount of oil production increase when gas is injected, where the axis represents the time from 1-11-2022 to 1-1-2060, and the y-axis represents the amount of oil production when gas is injected.

Field Oil Recovery Factor at Gas Injection:
This figure shows the total oil production from the reservoir when the gas is injected, in the x axis representing the time from 1-11-2022 to 1-1-2060.
Field Pressure Factor at Gas Injection: This figure shows the pressure in the reservoir and its impact on gas injection 5Through this figure, we notice when the amount of gas injection increases, the pressure increases gradually, the x-axis represents the time from 1-11-2022 to 1-1-2060, and the y-axis represents the pressure in the field.

Gas Saturation at Gas Injection:
This figure shows the percentage of gas saturation when injecting gas, and the percentage of saturation from 12% to 97%, and the percentage of gas saturation increases when injecting gas.7. The lower the compressibility value of the rock, the lower the value of the oil production rate.The higher the compressibility value of the rock, the higher the rate of oil production.Figure 28 shows the percentage of water saturation.It is noticed that at the side of the injection wells of (108,109,110), the percentage of water saturation is less as a result of the increase in gas injection, it is on (Scale12%).It is also noticed that the more gas is injected, the lower the water saturation rate.shows the percentage of gas saturation, and we notice in the injection wells (108,109,110) in the sides of the wells, the color is red as a result of increased gas injection, and usually the red color represents the (97% Scale) The more gas is injected, the higher the gas saturation rate.8 shows the final results of the effect of compressibility of rocks for the four cases of: oil recovery factor, total amount of produced oil production, total amount of produced gas production, field pressure, water cur, and amount of produced water production.Comparison of Oil Recovery Factor at different Rock Compressibility: From the figure below, it is clear that the relationship between the oil recovery factor and the compressibility of rocks is a direct relationship.First case #1 (0.577).Second case #2 (0.578).Third case #3 (0.579).Fourth case #4(0.580).

Comparison of Field Oil Production Total at different Rock Compressibility:
From the figure below, it is clear that the relationship between the total amount of oil produced and the compressibility of rocks is a direct relationship.First case #1 (146727760).The second case #2 (147216350).The third case #3 (147704850).Fourth case #4 (148193870).

Fig. 7 :
Fig. 7: Initial Water Saturation Map PRIMARY RECOVERY: Table5shows the start date of production for seven wells, the beginning of production from 1-11-2022 to 1-5-2024, and the end of production for seven wells on 11-12-2060.Table5: Base Case at Primary Recovery

Fig. 8 :
Fig. 8: Field Oil Production and Field Gas Production Rates Vs.Time at Primary Recovery

Fig. 9 :
Fig. 9: Field Oil Recovery Factor, Water Cut, and Pressure Vs Time at Primary Recovery SECONDARY RECOVERY:

Fig. 10 :
Fig. 10: Field Oil Production Rate Vs.Time at Gas Injection Field Water Cut at Primary Recovery Gas Injection: This figure determines the amount of water produced.The more the amount of

Fig. 17 :
Fig. 17: Oil Saturation Mao at 2070 at Gas Injection ROCK COMPRESSIBILITY RESULTS: Field Oil Production Rate at different Rock Compressibility: Figure 18 shows the rate of oil production when rocks are compressed in four different solutions.The x-axis represents the time from 1-11-2022 to 1-12-2060.The Y axis represents the rate of oil production under the compressibility effect of rocks.The red color represents the first case (3 * 10 ^-6), indicating that the lowest value of compressibility of rocks.The green color represents the fourth case (6*10^-6), the highest value of compressibility of rocks as shown in the table7.The lower the compressibility value of the rock, the lower the value of the oil production rate.The higher the compressibility value of the rock, the higher the rate of oil production.Table 7 :Rock Compressibility

Field
Gas Production Rate at different Rock Compressibility:Figure19shows the rate of gas production when rocks are compressed in four different solutions.The x-axis represents the time from 1-11-2022 to 1-12-2060.The y axis represents the rate of gas production under the compressibility effect of rocks.The green color represents the first case (3 * 10 ^-6), indicating that the lowest value of compressibility of rocks.The violet color represents the fourth state (6*10^-6), the highest value of compressibility of rocks.The lower the compressibility value of rocks, the lower the rate of gas production.As the compressibility value of the rock increases, the rate of gas production increases.Field Oil Recovery Factor at different Rock Compressibility:Figure20shows the oil recovery factor when the rock is compressed in four different solutions.The x-axis represents the time from 1-11-2022 to 1-12-2060.The Y axis represents the oil recovery factor under the compressibility effect of rocks.The red color represents the first case (3 * 10 ^-6), indicating that the lowest value of compressibility of rocks.The green color represents the fourth case (6*10^-6), the highest value of compressibility of rocks.The lower the compressibility value of the rock, the lower the value of the oil recovery factor.As the compressibility value of the rock increases, the oil recovery factor increases.

Fig. 22 :
Fig. 22: Field Water Cut at different Rock Compressibility Field Water production rate at different Rock Compressibility: Figure 23 shows the amount of water produced when rocks are compressed in four different solutions.The x-axis represents the time from 1-11-2022 to 1-12-2060.The Y axis represents the amount of water produced by the compressibility effect of rocks.The violet color represents the first case (3 * 10 ^-6), indicating that the lowest value of compressibility of rocks.The blue color represents the fourth state (6*10^-6), the highest value of compressibility of rocks.The lower the compressibility value of the rocks, the lower the value of the amount of water produced.As the compressibility value of the rock increases, the amount of water produced increases.

Fig. 23 :
Fig. 23: Field Water Cut at different Rock Compressibility Field Water Production Total at different Rock Compressibility: Figure 24 shows the total amount of water produced when rocks are compressed in four different solutions.The x-axis represents the time from 1-11-2022 to 1-12-2060.The Y axis represents the total amount of water produced by the compressibility effect of rocks.The violet color represents the first case (3 * 10 ^-6), indicating that the lowest value of compressibility of rocks.The blue color represents the fourth state (6*10^-6), the highest value of compressibility of rocks.The lower the compressibility value of the rocks, the lower the value of the total amount of water produced.As the compressibility value of the rocks increases, the total amount of water produced increases.

Fig. 24 :Fig. 25 :
Fig. 24: Field Water Production Total at different Rock Compressibility Field Gas Production Total at different Rock Compressibility: Figure 25 shows the total gas production when rocks are compressed in four different solutions.The x-axis represents the time from 1-11-2022 to 1-12-2060, and the y-axis represents the total gas production at the impact of compressibility of rocks.The pink color represents the first case (3 * 10 ^-6), indicating that the lowest value of compressibility of rocks.The green color represents the fourth state (6*10^-6), the highest value of compressibility of rocks.The lower the compressibility value of the rocks, the lower the value of the total gas production.The higher the compressibility value of the rocks, the greater the value of the total gas production.Oil Saturation at different Rock Compressibility:Figure26shows the percentage of oil saturation.It is noticed that at the side of the injection wells of (108,109,110) the presence of the blue color as a result of the gas entrainment ranging from 0% to 76%.It is also notices that the more we increase the gas injection, the less oil saturation percentage becomes.

Fig. 26 :
Fig. 26: Oil Saturation at different Rock Compressibility Gas Saturation at different Rock Compressibility: Figure 27shows the percentage of gas saturation, and we notice in the injection wells (108,109,110) in the sides of the wells, the color is red as a result of increased gas injection, and usually the red color represents the (97% Scale) The more gas is injected, the higher the gas saturation rate.

Fig. 31 :
Fig. 31: Comparison of Field Gas Production Total at different Rock Compressibility Comparison of Field Pressure at different Rock Compressibility: From the figure below, it is clear that the relationship between field pressure and rock compressibility is direct.First case #1 (618,529).Case #2 (618,812).The third case #3 (619.102).Case #4 (619,390).

Table 1 :Initial Reservoir Properties
Reservoir Fluid Properties: It is plays a key role in the design and optimization of injection and production strategies and surface facilities for efficient reservoir management as shown in the Table2.

Table 2 :
Reservoir Fluid Properties