What is a strong waterdrive reservoir?
What is water drive?
Why does a waterdrive yield a lower terminal pressure?
How does water influx affect fractional oil recovery?
What is a moderate aquifer?
Which type of waterdrive encircles the reservoir?
How to diagnose an active aquifer?
See 4 more
About this website
What is a depletion drive reservoir?
A depletion drive reservoir is characterized by a rapidly increasing gas–oil ratio from all wells, regardless of their structural position. After the reservoir pressure has been reduced below the bubble point pressure, gas evolves from solution throughout the reservoir.
What is gas drive reservoir?
Solution gas drive is a mechanism by which dissolved gas in a reservoir will expand and become an energy support to produce reservoir fluid. Solution gas drive has other name, such as dissolved gas drive or depletion drive.
What is undersaturated reservoir?
As we discussed in Lesson 2, an undersaturated oil reservoir is defined as a reservoir in which the initial pressure is greater that the bubble-point pressure of the crude oil. This results in a single, liquid hydrocarbon phase in the reservoir.
What is drive mechanism in reservoir engineering?
In addition to rock and fluid properties, drive mechanisms—which describe the source of energy for moving fluids into, through and out of a reservoir—also determine how fluids move within the reservoir. The primary natural drive systems are water drive, solution-gas drive, gas-cap drive and gravity drive (Figure 1).
How do I find my water drive reservoir?
Strong waterdrive reservoirs are characterized by a slow or negligible pressure decline. Thus, a slower-than-expected pressure decline can help indicate a waterdrive. Material-balance calculations are important to help identify and confirm a slower-than-expected pressure decline.
What is Edge water Drive?
In an edge water drive, the aquifer is located on the flanks of the reservoir and the water moves upward along the reservoir dip.
What is saturated and undersaturated reservoir?
Saturated: Reservoir pressure ≤ bubble point of oil. For an undersaturated reservoir no free gas exists until the reservoir pressure falls below the bubblepoint. In this regime reservoir drive energy is provided only by the bulk expansion of the reservoir rock and liquids (water and oil).
What are the different types of oil reservoirs?
The reservoirs are classified according to the initial state of the fluids in the reservoir in three broad categories, including oil, gas-condensate, and gas reservoirs.
Why is Pvt important?
Pressure, volume temperature (PVT) and reservoir fluid phase behaviour examinations provide important information that enables oil and gas organisations to predict the performance of fluids through all stages of recovery.
What is the function of drive mechanism?
Drive mechanisms serve as opening and closing mechanisms. With a drive mechanism, the parallel contact stroke is generated manually, ensuring precise, reliable contacting. Drive mechanisms are delivered without a mounting plate, without gas pressure springs, and without bearing blocks.
What is active water drive?
The term active water drive refers to the water encroachment mechanism in which the rate of water influx equals the reservoir total production rate. Active water-drive reservoirs are typically characterized by a gradual and slow reservoir pressure decline.
Which is the most efficient drive mechanism?
Waterdrive is the most efficient drive mechanism, followed by gasdrive and gravity drainage. Reservoir-drive mechanisms are also called natural drives.
What is a volumetric reservoir?
Conversely, volumetric reservoirs are reservoirs in which hydrocarbon PV does not change during pressure depletion. Because waterdrive reservoirs involve water influx into the reservoir, they also are referred to as water-influx reservoirs.
What is compaction drive?
A drive mechanism in a weak zone that displaces fluid by reducing the overall volume of the formation.
What is gas cap?
The gas cap, also known as the fuel filler cap, is a simple but important component that is found on the vast majority of road going cars and trucks. Their purpose is simple; to prevent dirt, debris, and dust from entering the gas tank, as well as providing a reliable seal.
What is bubble point pressure in reservoir?
Bubble point pressure (Pb) is one of the critical reservoir fluid pressure–volume–temperature (PVT) properties. It is the pressure at which the first bubble of the gas comes out of the oil solution.
Reservoir drive mechanisms - AAPG Wiki
A strong water drive provides very good pressure support from the aquifer (100% voidage replacement) with minimal pressure drop at the wellbore.
Behavior and Control of Natural Water-drive Reservoirs
Abstract. Methods are presented for measuring and comparing "degree" of waterdrive, and for observing the control that rate of withdrawal exerts overdecline of reservoir pressure.Degree of water drive is studied from pressure-production curves of 10reservoirs; the method used to present these comparatively is to convertcumulative oil production from barrels to percentage of ultimate. Degree ...
The gas recovery of water-drive gas reservoirs - ResearchGate
Hydrocarbon reservoirs are primary produced based on their initial pore pressure (Gong and Rossen 2018). However, due to the interplay of geological, physical, and economic limits, it is often ...
Water-drive reservoir | Article about water-drive reservoir by The Free ...
An oil or gas reservoir in which pressure is maintained to a greater or lesser extent by an influx of water as the oil or gas is removed.
Water Drive Gas Reservoirs: Uncertainty in Reserves Evaluation From ...
Abstract. The use of the material balance equation to estimate the volume of hydrocarbons originally present in a reservoir, whose producing mechanism is partly due to water drive, has been discussed in the literature by several authors. There is no general agreement upon the possibility of obtaining reliable results by this method. Gas reservoirs in contact with an active aquifer are ...
Drive mechanisms and recovery - AAPG Wiki
Solution gas drive. In a solution (or dissolved) gas drive reservoir, the oil-bearing rock is completely surrounded by impermeable barriers. As the reservoir pressure drops during production, expansion of the oil and its dissolved gas provides most of the reservoir's drive energy ().Additional energy is obtained from the expansion of the rock and its associated water.
What are the two driving forces in a combination drive reservoir?
Two combinations of driving forces can be present in combination- drive reservoirs. These are (1) depletion drive and a weak water drive and; (2) depletion drive with a small gas cap and a weak water drive. Then, of course, gravity segregation can play an important role in any of the aforementioned drives. Combination-drive reservoirs can be ...
How much oil is in a combination drive reservoir?
A combination-drive reservoir contains 10 MMSTB of oil initially in place. The ratio of the original gas-cap volume to the original oil volume, i.e., m, is estimated as 0.25. The initial reservoir pressure is 3000 psia at 150°F. The reservoir produced 1 MMSTB of oil, 1100 MMscf of 0.8 specific gravity gas, and 50,000 STB of water by the time the reservoir pressure dropped to 2800 psi. The following PVT is available:
Why do gas cap reservoirs flow longer?
Well behavior: Because of the effects of gas cap expansion on maintaining reservoir pressure and the effect of decreased liquid column weight as it is produced out of the well, gas cap drive reservoirs tend to flow longer than depletion drive reservoirs.
Why are gas cap reservoirs rate sensitive?
Therefore, gas cap drive reservoirs are rate sensitive, as lower producing rates will usually result in increased recovery.
How to identify a gas cap drive reservoir?
Gas cap drive reservoirs can be identified by the presence of a gas cap with little or no water drive as shown in Figure 4.3. Due to the ability of the gas cap to expand, these reservoirs are characterized by a slow decline in the reservoir pressure. The natural energy available to produce the crude oil comes from the following two sources:
What is the most common type of drive mechanism?
The most common type of drive encountered, therefore, is a combination-drive mechanism as illustrated in Figure 11-13.
Can you apply a material balance to a combination drive reservoir?
It is rarely possible to apply a material balance to a combination drive reservoir and determine the OOIP, the gas cap size, and the aquifer influx. There are three sources of reservoir energy and only one material balance equation, so the problem is usually indeterminate.
What is reservoir drive?
The reservoir drive mechanism supplies the energy that moves the hydrocarbon located in a reservoir container toward the wellbore as fluid is removed near the wellbore. There are five common drive mechanisms: One type usually dominates, but drive types can occur in combination.
How does a strong water drive work?
A strong water drive provides very good pressure support from the aquifer (100% voidage replacement) with minimal pressure drop at the wellbore. The aquifer water expands slightly, displacing the oil or gas from the reservoir toward the borehole as pressure drops around the borehole. This mechanism exists only where the aquifer is of equal or better quality than the reservoir and has a much larger volume than the reservoir (about 10 times) or is in communication with surface recharge. A strong water drive is more effective in oil reservoirs than in gas reservoirs. On a semi-log plot of production decline, the curve tends to be flat.
What is the energy that drives oil to the wellbore?
In oil reservoirs with little or no water drive, reservoir energy to drive the oil toward the wellbore can be supplied by expansion of the oil due to gas expanding in solution. This is a solution gas (or dissolved gas or depletion) drive.
What is partial water drive?
A partial water drive results where an aquifer has poorer quality in terms of pore geometry or has limited volume. When the water support diminishes, the hydrocarbon production rate drops more rapidly than in a reservoir with a strong water drive and recovery is reduced.
Why does reservoir fluid pressure increase?
As reservoir fluid pressure declines, the pressure on the solids, or net confining pressure (P nc ), increases because pore fluid pressure carries less of the weight of the overburden. Some reservoirs respond to the increase in P nc by the collapse of the pore space. This can be an efficient way to expel hydrocarbons.
How does gravity drain oil?
In gravity drainage, oil drains downward through a reservoir under the influence of gravity. This requires high vertical permeability or steeply dipping beds and thus is common in fractured reservoirs. Efficiency can be surprisingly high (75%+), especially where beds have steep dip, the oil has low viscosity, and the oil draining from the top of the column is replaced by exsolved gas.
Where is rock drive common?
Rock drive is common in shallow reservoirs or in reservoirs with unconsolidated sediments. It can also be expected to occur where porosity has been held open by high fluid pressures. Good examples of high pressure and unconsolidated reservoirs are some Danian Chalk reservoirs of the North Sea.
Reservoir Characterization
Djebbar Tiab, Erle C. Donaldson, in Petrophysics (Fourth Edition), 2016
The Components of a Gas Storage Facility
A storage reservoir almost always contains some water and may have an active water drive. When dry gas from the pipeline is injected into the storage reservoir, liquid water from the formation will evaporate into the injected gas. The gas will then have too much water to be pipeline quality gas. The gas must be dehydrated on the withdrawal cycle.
Performance of Oil Reservoirs
Tarek Ahmed, Paul D. McKinney, in Advanced Reservoir Engineering, 2005
Water Influx
Tarek Ahmed, D. Nathan Meehan, in Advanced Reservoir Management and Engineering (Second Edition), 2012
Water Influx
Based on the degree of the reservoir pressure maintenance provided by the aquifer, the natural water drive is often qualitatively described as:
Water Influx
Based on the degree of the reservoir pressure maintenance provided by the aquifer, the natural water drive is often qualitatively described as:
Oil Recovery Mechanisms and The Material Balance Equation
The reservoir pressure decline is usually very gradual. Figure 11-9 shows the pressure-production history of a typical water-drive reservoir. It is not uncommon for many thousands of barrels of oil to be produced for each pound per square inch drop in reservoir pressure.
Where does water drive energy come from?
Drive Mechanisms. The energy for a waterdrive system comes from a connected aquifer. As hydrocarbons are extracted, the aquifer expands, and water migrates to replace the moved oil or gas. This water may come from below, a bottomwater drive, or it may come from surrounding sources, an edgewater drive.
What is the overburden of a reservoir?
The overburden—layers of rock and soil above a reservoir— weighs upon the rocks and fluids and affects temperature and pressure within the reservoir. Over geologic time, forces in the reservoir equilibrate and establish the formation pore pressure, which is the primary energy source for moving fluids through a formation.
How do formation drives work?
Figure 1. Formation drive mechanisms. Waterdrive systems (left) rely on water from a connected aquifer to replace produced oil. Gas cap drives (middle left) are energized by expanding gas that fills the voids that occur after liquids are removed. Gas in the saturated oil of a solution-gas drive system (middle right) comes out of solution after the reservoir pressure drops below the bubblepoint. Gravity, or combination drive systems (right), have gas, oil and water layers. As the oil is produced, the gas/oil contact drops as the gas cap expands, and the oil/water contact rises.
How do hydrocarbons get to the surface?
Producing hydrocarbons, bringing them from downhole reservoirs to the surface , in an efficient and cost effective manner can be a challenge for E&P companies. In order to efficiently produce those hydrocarbons, reservoir engineers must understand the reservoir drive—the mechanism that moves hydrocarbons out of the rock pore spaces and into the wellbore. Understanding a field's active drive system or systems helps operators develop production strategies that maximize the recovery factor—the percentage of oil or gas that is brought to the surface compared with what was originally in place.
What causes fluids to segregate?
Gravity will cause fluids to segregate according to fluid density, such that the typical order of fluids in a reservoir is gas on top, oil and then water at the bottom. If pressure disequilibrium occurs, fluids will move from regions of high pressure to those of low pressure.
Why does water rise faster in a well?
As the contact rises , water may reach the producing interval in the well. Accelerated movement caused by large pressure differentials around the wellbore may cause water near the well to rise faster. This phenomenon—referred to as coning—can cause early water production from high flowrate wells (Figure 2).
What is a combination drive?
Combination drive systems are common and are mixtures of two or more primary drive systems. Although another drive mechanism—rock compaction drive—is rare, it is an important factor in a few major fields around the world. Figure 1. Formation drive mechanisms.
What is a strong waterdrive reservoir?
Strong waterdrive reservoirs are characterized by a slow or negligible pressure decline. Thus, a slower-than-expected pressure decline can help indicate a waterdrive. Material-balance calculations are important to help identify and confirm a slower-than-expected pressure decline.
What is water drive?
Waterdrive (or water drive) petroleum reservoirs are characteristically bounded by and in communication with aquifers. As pressure decreases during pressure depletion, the compressed waters within the aquifers expand and overflow into the petroleum reservoir. The invading water helps drive the oil to the producing wells, ...
Why does a waterdrive yield a lower terminal pressure?
The waterdrive yields a lower terminal pressure because lower gas saturations are realized at a given pressure . The example water and solution-gas drives yield final pressures of 471 and 613 psia, respectively.
How does water influx affect fractional oil recovery?
Fig. 1 shows the effect of water influx on a plot of pressure vs. fractional oil recovery. The initial reservoir pressure is 2,000 psia. Waterdrive and solution-gas-drive performances are compared. This figure shows that water influx consistently improves the fractional oil recovery at a given pressure. Alternatively, the waterdrive maintains a higher pressure at a given recovery.
What is a moderate aquifer?
A moderate or weak aquifer is one in which the water recharge rate is appreciably less than the reservoir’s fluid withdrawal rate. These reservoirs are called partial waterdrives and they are characterized by pressure declines greater than a complete waterdrive but less than a volumetric reservoir.
Which type of waterdrive encircles the reservoir?
Peripheral waterdrive -- the aquifer areally encircles the reservoir, either partially or wholly,
How to diagnose an active aquifer?
The reservoir pressure distribution also can help diagnose an active aquifer. For peripheral-water and edgewater drives, higher pressures tend to exist along the reservoir/aquifer boundary while lower pressures tend to exist at locations that are more distant. A pressure contour map is sometimes helpful to identify pressure disparities.
