The application of the waterflooding technique in the Waha reservoir requires the injection of water into the oil zone to displace the oil, due to the primary recovery mechanism used in the Waha reservoir. The previous study done concludes that there are two factors that have greatly influenced the flood performance, which are the mobility ratio and the reservoir heterogeneity. Therefore, a numerical approach was used to study the effect of buoyancy ratio and reservoir heterogeneity on waterflood design with the five-point injection model.
Meanwhile, permeability has a major impact on water flood performance in terms of reservoir heterogeneity factor, compared to porosity and thickness. High permeability formation allows the fluid to travel faster and increases the displacement mobility ratio, while low permeability formation allows the fluid to travel more slowly and decreases the displacement mobility ratio. The estimate based on simulated results indicates that the mobility ratio equal to 0.8 (M=O.S) will optimize the flooding performance given the permeability variation of 0.4.
FOPT Total Field Oil Production FOE Field Oil Recovery Factor FWCT Field Oil Water Cut.
INTRODUCTION
- BACKGROUND STUDY
- WAHARESERVOIROVERVIEW
- CONSIDERATION OF WATERFLOODING PROJECT
- PROBLEM STATEMENT
- OBJECTIVES
- SCOPE OF STUDY
- RELEVANCYANDFEASIBILITYOFTHEPROJECT
5] In pressure maintenance, water is injected into the aquifer to maintain pressure for the water drive mechanism. Field observation indicates that the Waha formation is a saturated reservoir, enabling primary recovery by the solvent gas movement mechanism with weak aquifer support (water-conducting). The gas-solution driving mechanism present in the Waha formation is the main driving mechanism used in primary recovery.
According to Thomas (1989), the solution-gas propulsion mechanism is generally considered the best candidate for implementing the waterflooding technique. The hydrodrive mechanism present in the Waha Formation is categorized as a weak hydrodrive mechanism. Thomas (1989) also describes that consideration of the water driving mechanism for flooding depends on the strength of the driving mechanism itself.
Gulick (1998) describes that the low oil recovery achieved by primary extraction is mainly due to the natural propulsion mechanism having low reservoir energy, in addition to reservoir heterogeneity and mobility ratio during the displacement process.
LITERATURE REVIEW
- WATERFLOODING TECHNIQUE
- FIVE SPOTINJECTIONPATTERN
- BUCKLEY -LEVERETT DISPLACEMENT THEORY
- FLUID SATURATION DISTRIBUTION
- BREAKTHROUGH TIME DETERMINATION
- MOBILITY RATIO
- RESERVOIR HETEROGENEITY
This is due to the assumption that the displacement of oil in the flooding process is equal to each other because the distance from the injector to the producer is constant. The mechanism of the waterflood technique in oil displacement is best described by the Buckley-Leverett displacement theory. The fractional flow equation was developed from a combination of the frontal advance equation and Darcy's law.
It is agreed that during oil production, the level of zero capillary pressure increases, creating a tendency for water saturation throughout the reservoir to increase to reach equilibrium. In those cases where the capillary term is neglected, the breakthrough time can be determined from the point where the tangent of the curves. Mobility ratio, M can be adjusted as the mobility of the displacing fluid to the mobility of the displaced fluid.
Assuming that the effective permeability properties of the liquid do not change, the mobility ratio is less than I, indicating that water is more viscous compared to the viscosity of oil. Guliyev (2008) supports Wang (1998) by stating that since the viscosity of water is higher compared to the viscosity of oil, the displacement velocity of water is relatively lower compared to oil. This will result in the oil staying ahead of the water during displacement.
8] Assuming that the fluid properties effective permeability remain constant, a mobility ratio greater than 1 indicates that the oil is more viscous compared to the viscosity of water. Guliyev (2008) supports Wang (1998) by stating that the viscosity of oil is higher compared to that of water, so the velocity of oil during displacement is relatively lower compared to water. 1955) conducted experimental studies on the effect of fluid mobility on surface sweep efficiency resulting from water or gas injection.
Higher areal sweep efficiency can be used to indicate the amount of oil displaced from the reservoir in which it is assumed to be fully produced. 1989) pointed out that lithology has a profound influence on the effectiveness of water flooding in a particular reservoir. 14] In the method, the permeability was plotted against the percentage of the thickness in a log-probability graph, and the permeability variation V was estimated with the formula.
METHODOLOGY AND PROJECT WORK
- DESIGNING AND MODELLING THE BASE CASE
- ESTIMATION OF MOBILITY RATI0
- ESTIMATION OF RESERVOIR HETEROGENEITY
- KEY MILESTONE
Since the area of the Five-Spot Pattern focused on this study is given as 435,600 if,. In terms of thickness, the basic model is designed with three layers of different thickness, as indicated in the characteristics of the Waha reservoir. The formation thickness is 79 feet, with three characteristic layers of thickness from the top: 14 feet, 52 feet, and 13 feet.
In this basic model, the injection well was located in the grid (I, I), while the production well was located in the grid (10, 10). Both the injection and production wells perforate all three layers. l,li I' 1'111 I l''l'ul)mllf. The other parameters used to design the base model are referred to the given Waha reservoir properties which can be referred to in the appendix section.
In order to calculate the mobility ratio, relative permeability was plotted against the water saturation. Using the formula, we can calculate the mobility ratio of our base case model and predict the water viscosity for our study, assuming that the oil viscosity and relative permeability are constant. In order to calculate the reservoir heterogeneity variance, the permeability was plotted against percentage of formation thickness in a log-likelihood graph.
From this graph we can calculate that the permeability deviation using the Dykstra-Parson formula 0.4. To complete the project, student plays an important and crucial role as the researcher, in which full commitment, initiative and efforts are required to complete the tasks. Therefore, supervision and assistance from the supervisor is necessary to ensure that the student is on the right track and timeline.
This can only be achieved through a good and consistent communication between the student and the supervisor, in which the weekly meeting can be used as the best platform for the communication.
RESULT AND DISCUSSION
Next, the FOE versus Time curves were plotted to determine the value of oil recovery achievable with the base model. Based on the breakthrough time, we draw a straight line to determine the oil recovery that can be achieved. The effects of mobility ratio on waterflood performance can be seen by plotting the curves of FWCT versus Time and FOE versus Time for all mobility ratios used in the simulation.
From the curves we can determine the breakthrough time and the oil recovery factor for the other two different mobility ratios. For layer I (k=398md), the breakthrough time and oil produced can be determined for a mobility ratio equal to 0.5 and 2. For layer 2 (k=225md), the breakthrough time and oil produced can be determined for a mobility ratio equal to 0.5 and 2.
For layer 3 (k=95md), the breakthrough time and produced oil can be determined for mobility ratio equal to 0.5 and 2. Simulated results showed that high oil recovery can be achieved by mobility ratio equal to 0.5, followed by mobility ratio equal to I and mobility ratio equal to 2. Based on the equation, mobility ratio equal to 0.5 indicates that the velocity of the oil is double that of the oil.
Since water moves more slowly than oil, the displacement process is similar to piston-like motion (advancement of water will always lag behind oil), in which more oil can be displaced and there is no oil left. The exact mobility ratio to produce this 'optimal' waterflooding performance cannot be determined, but can be estimated at a mobility ratio of 0.8 (based on the behavior of the chart). The effects of reservoir heterogeneity on waterflooding performance can be seen by plotting the FWCT versus time curves and the FOE versus time curves for the two models used in the simulation.
From the curves we can determine the breakthrough time and the oil recovery factor for the homogeneous model. For all layers, the breakthrough time and oil produced can be determined for the homogeneous model. However, due to the higher velocity of the displacement, the mobility ratio value may be increased, due to some oil left behind during the displacement.
Moreover, the maximum volume of oil available in that formation makes changes in the mobility ratio insignificant.
CONCLUSIONS AND RECOMMENDATIONS
Several recommendations can be made in this study to improve the accuracy of this study and provide ideas for future work. The scope of the study should be improved from a quarter of the five-spot pattern to a five-spot pattern. This will improve the accuracy results of our displacement, because in this study it was assumed that one quarter of the five-point pattern is sufficient to superimpose the other three-quarters of the five-point pattern.
The scope of the mobility ratio should be improved, with a greater number of variables in the mobility ratio, instead of just three. This allows research into the behavior of the mobility ratio to be performed, where an exact estimate can be made of the mobility ratio that yields optimal flood performance. The scope of reservoir heterogeneity needs to be improved, with a greater number of variables in the permeability variation, instead of just two.
This testament enable the study of permeability variation to be carried out, in which the exact effect of permeability variation on the ratio of mobility and water inundation can be further studied. Estimates of Undiscovered Oil and Gas in the World's Petroleum Systems: Examples of North Africa and the Middle East. A study of the effect of mobility ratios on model displacement behavior and simple lines to ascertain the permeability fields of permeability media.
A simulation study of surface sweep efficiency versus a function of mobility ratio and aspect ratio for a spaced line flooding pattern.
W AHA RESERVOIR PROPERTIES
