What is reservoir drive?
How does a strong water drive work?
What is the energy that drives oil to the wellbore?
How does gas expansion work?
What is partial water drive?
What happens when gas is 5-10% free?
Why does reservoir fluid pressure increase?
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What is reservoir drive mechanism?
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: Water drive. Gas expansion. Solution gas.
Which reservoir drive mechanism has the highest recovery factor?
The rate of oil gravity drainage in the reservoir is usually low compared to field production rates. Over time, however, gravity drainage can be extremely efficient and recoveries higher than any of the primary drive mechanisms are possible.
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 depletion drive mechanism?
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 primary recovery mechanism?
Typically, the primary recovery process involves placing increased pressure on the oil within wells in order to force oil to the surface. Mechanical systems, such as rod pumps, are also sometimes used.
What are the typical recovery factors for gas reservoirs?
As noted previously, ultimate recoveries of 80% to 90% are common in volumetric gas reservoirs, while typical recovery factors in water-drive gas reservoirs can range from 50% to 70%.
What is dissolved gas drive?
PetroWiki. A reservoir drive mechanism in which dissolved gas from the crude oil breaks out of solution and provides energy to push the hydrocarbons toward the wellbore.
What is compaction drive?
A drive mechanism in a weak zone that displaces fluid by reducing the overall volume of the formation.
Which drive mechanism involves using miscible gas to transport crude oil to the well bore?
Reservoir Drive Mechanism Recovery of hydrocarbons from Petroleum/oil reservoir. It supplies energy that moves the hydrocarbons located in a reservoir toward the wellbore as fluid is removed near the wellbore.
What are examples of drive mechanism?
Reservoir-drive mechanisms include gasdrive (gas cap or solution gasdrive), waterdrive (bottomwater drive or edgewater drive), combination drive, and gravity drainage. Waterdrive is the most efficient drive mechanism, followed by gasdrive and gravity drainage. Reservoir-drive mechanisms are also called natural drives.
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.
What is volumetric gas drive?
A reservoir drive mechanism provided by the expansion of solution gas in the oil.
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.
How does enhanced oil recovery work?
EOR is a process that increases the amount of crude oil that can be extracted from an oil field. It is usually done by injecting water or gas into a reservoir to increase pressure and force the crude out of the rock.
What are examples of drive mechanism?
Reservoir-drive mechanisms include gasdrive (gas cap or solution gasdrive), waterdrive (bottomwater drive or edgewater drive), combination drive, and gravity drainage. Waterdrive is the most efficient drive mechanism, followed by gasdrive and gravity drainage. Reservoir-drive mechanisms are also called natural drives.
Which drive mechanism involves using miscible gas to transport crude oil to the well bore?
Reservoir Drive Mechanism Recovery of hydrocarbons from Petroleum/oil reservoir. It supplies energy that moves the hydrocarbons located in a reservoir toward the wellbore as fluid is removed near the wellbore.
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.
PEH:Oil Reservoir Primary Drive Mechanisms - PetroWiki
has found success in the use of the heptanes-plus content as a correlating parameter. The inverse of the oil FVF yields a measure of the original oil in place (OOIP) per unit volume of reservoir pore space.
Predicting reservoir drive mechanism - AAPG Wiki
Predicting drive type. Reservoir analysis includes making cross sections, structural maps, and isopach maps.Analyzing nearby producing fields yields the best set of inferential data. This includes (1) making plots of historical oil, gas, condensate, and water production and pressure decline and (2) making cumulative production maps.
Primary drive mechanisms - PetroWiki
Defining primary recovery. Primary recovery should be distinguished clearly from secondary recovery. Muskat defines secondary recovery as "the injection of (fluids) after the reservoir has reached a state of substantially complete depletion of its initial content of energy available for (fluid) expulsion or where the production rates have approached the limits of profitable operation."
Drive Mechanism - an overview | ScienceDirect Topics
Amirhossein Mohammadi Alamooti, Farzan Karimi Malekabadi, in Fundamentals of Enhanced Oil and Gas Recovery from Conventional and Unconventional Reservoirs, 2018. 1.10.5 Gravity Drainage Drive. Gravity drive mechanism is active in both gas cap and water drives, where the differences in densities act as source of energy. The energy is provided by upward liberated gas movement to the primary or ...
What is the drive mechanism of a gas reservoir?
The final drive mechanism associated with conventional gas reservoirs is aquifer drive, or water encroachment. As with oil reservoirs, this drive mechanism occurs when the reservoir is in communication with a water-bearing aquifer. As the reservoir pressure declines, the rock and water in the aquifer expand, and water is expelled from the aquifer and into the reservoir. This encroachment of water into the reservoir provides pressure support.
What are the three drive mechanisms associated with conventional gas reservoirs?
These are: gas expansion (most significant drive mechanism in conventional gas reservoirs); gas desorption (may only be present in certain unconventional gas ...
What is an unconventional gas reservoir?
Unconventional reservoirs are reservoirs with low permeabilities that require special production technologies that allow for economic recoveries of gas. Typically, the threshold to define an unconventional gas reservoir is a reservoir with a permeability less than 0.1 md. Gas expansion is the primary drive mechanism in most conventional gas ...
What happens to the reservoir as the pressure declines?
As the reservoir pressure declines, the rock and water in the aquifer expand, and water is expelled from the aquifer and into the reservoir. This encroachment of water into the reservoir provides pressure support. These last two drive mechanisms may be slightly deceptive as to whether they aid in gas production or not.
What is gas expansion?
Gas expansion is the primary drive mechanism in most conventional gas reservoirs. Again, the analogy of a gas-filled balloon a very appropriate analogy. If a balloon is filled with high pressure gas and the end is opened to the low pressure atmosphere, then gas will expand and exit the balloon. This mechanism is very efficient and commonly results in recoveries as high as 85 percent of the original-gas-in-place.
What is the difference between unconventional and conventional gas?
In this list, I make a distinction between Conventional and Unconventional Gas Reservoirs. Conventional gas reservoirs are reservoirs with sufficiently high permeability to allow for production using conventual well technologies. Unconventional reservoirs are reservoirs with low permeabilities that require special production technologies that allow for economic recoveries of gas. Typically, the threshold to define an unconventional gas reservoir is a reservoir with a permeability less than 0.1 md.
How does a solution gas drive reservoir work?
No free gas exists in the reservoir while the pressure remains above the bubblepoint. The reservoir drive energy is provided only by the limited expansion of the oil, rock, and water. In a saturated reservoir, the reservoir pressure is at the bubblepoint. As soon as oil is produced, the pressure drops and bubbles of solution gas form in the reservoir. This solution gas liberation causes the oil to shrink , but the oil shrinkage is more than offset by solution gas expansion, the primary source of reservoir drive energy below the bubblepoint.
What are the three primary oil reservoir drive mechanisms?
The three primary oil reservoir drive mechanisms are solution gas drive, gas cap drive, and water drive . Reservoir pressure trends and producing gas-oil ratio trends of these three drive mechanisms are shown in Figures 1 and 2, respectively. A combination or mixed drive occurs when two or more of the primary drive mechanisms are present in the same reservoir. A combination drive may also occur when one or more of the primary drive mechanisms are assisted by gravity drainage. Table 1 shows the energy sources and ultimate recovery ranges of the major drive mechanisms.
How does gas cap drive recovery work?
Recovery can also be improved by shutting-in wells when they begin to produce large amounts of gas cap gas. In addition, the produced gas may be returned to the gas cap using gas injection wells located high on structure.
How much oil is recovered from a gas cap drive?
Oil recovery from gas cap drive reservoirs typically ranges from 20 to 40% of the original oil in place. The actual recovery obtained depends on the size of the initial gas cap, the structural geometry of the reservoir, and the way the field is managed.
What conditions are conducive to gravity drainage?
Conditions conducive to gravity drainage include thick reservoirs with high vertical permeabilities or thin reservoirs with steep dips. In a solution gas drive reservoir perforated down dip, gravity drainage can cause released solution gas to migrate upward and oil to flow downward, conserving reservoir energy and increasing recovery to near that of a water drive.
How does water drive improve recovery?
Water drive recovery can be improved by balancing production rates across the field so that the oil-water contact moves up as uniformly as possible. Since water drive is usually more efficient than solution gas drive, in some cases it is possible to increase recovery by producing the reservoir at a rate low enough that the aquifer is able to maintain a high reservoir pressure.
What is the natural energy of a reservoir?
The natural energy of a reservoir can be used to move oil and gas toward the wellbore. Used in such a fashion, these sources of energy are called drive mechanisms. Early determination and characterization of the drive mechanism (s) present within a reservoir may allow a greater ultimate recovery of hydrocarbons.
Where does gas drive come from?
The energy source for gas cap drives comes from expansion of the gas at the top of the reservoir. The gas may be in place when the reservoir is initially produced, a primary gas cap, or it may form as a secondary gas cap, which results from gas migration out of the oil when reservoir pressure drops below the bubblepoint.
Where are solution gas drives found?
Solution gas drives are found in saturated reservoirs, in which the ini-tial pore pressure is above the bubblepoint. As oil is produced, the reservoir pressure drops below the bubblepoint, gas bubbles come out of solution and expand in the oil. Solution gas can also be liberated from water.
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 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.
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 happens to the pressure of a well after drilling?
After a well has been drilled and completed, the wellbore can create disequilibrium, serving as a low pressure conduit toward which fluids in the wellbore will migrate. As oil, gas and water flow into a wellbore, the pressure equilibrium is disturbed near the well.
What is the last drive mechanism associated with oil reservoirs?
The last drive mechanism associated with oil reservoirs is aquifer drive, or water encroachment. If a reservoir is in contact with a water-bearing aquifer, then as the reservoir pressure declines, the rock and water in the aquifer expand and water is expelled from the aquifer and into the reservoir. This encroachment of water into the reservoir ...
What causes a solution gas drive?
Solution gas drive is caused by the solubility of natural gases in crude oils. This was discussed in Lesson 3 and is quantified with the oil property of the solution gas-oil ratio, R s. In undersaturated oil reservoirs, oil is found as a single-phase hydrocarbon fluid at discovery. As wells are drilled and put into production, the reservoir pressure declines (but supported by rock and fluid expansion) until it reaches the bubble-point pressure. At this time, gas comes out of solution and also begins to expand. It is the expansion of the gas that was originally in solution in the oil phase that we refer to as solution gas drive.
What is the driving force for oil production?
As with all gases and liquids in nature (weather fronts, sea and air currents, etc.), crude oil in the reservoir flows from locations of high pressure (the interior of the reservoir) to locations of low pressure (production wells). It is this pressure differential that is the driving force for fluid flow and production from wells. To start our discussion on fluid movement, we will begin with a discussion of the Drive Mechanisms in an oil reservoir. Drive mechanisms are the physical phenomena that occur in the reservoir that help to keep the reservoir pressures high.
Why do fluids expand?
In Lesson 3, we saw that as pressure is reduced the compressibility of the rock and fluids ( Equation 3.17, Equation 3.26, Equation 3.30, and Equation 3.43a) causes the volumes of the oil and water to expand and the pore-volume to shrink (equivalent to the rock grain volume expanding). All of these phenomena cause the pressure to remain higher than it would otherwise have been had they not been occurring (engineering analysis would indicate that if the fluids are expanding and the pore-volume is shrinking, then the in-situ fluids will be displaced to areas of low pressure).
How much recovery does a gas cap drive give?
Gas cap drive can account for up to 30 percent recovery of the STOOIP depending on the size of the original gas cap.
How effective is gravity drainage?
In very thick reservoirs or in highly dipping reservoirs, gravity drainage can be a very effective drive mechanism and may account for up to 40 percent recovery of the STOOIP. In order to be effective, wells must be completed deep in the reservoir and must have a large Oil Column (reservoir depth containing oil) above the completion.
What happens to the gas cap as wells are drilled?
As wells are drilled and put into production, the pressure declines (again, other drive mechanisms may provide support to partially maintain the reservoir pressure), and the gas cap begins to expand. It is the expansion of the gas that was originally free in the reservoir that we refer to as gas cap drive.
What are the energies of a reservoir?
The energies discussed thus far represent "internal" reservoir energies (i.e., energies originally present within the reservoir and its adjoining geological units at the time of discovery). In addition to these energies, there may be important "external" energies (i.e., energies that originate from outside the reservoir).External energies imply the practice of injecting fluids into the reservoir to augment the reservoir’s natural energies. This practice is called pressure maintenance. The two most common injection fluids are compressed water and gas. The resultant action of injected fluids once inside the reservoir is much the same as the fluids originally present. The overall intention of injecting fluids is to add energy to the reservoir to recover more oil or gas than would otherwise be recovered. If gas is injected, it is clear that the intention is to recover more oil than otherwise would be recovered. In addition, the economic attractiveness of this practice relies on the expectation that the additional income derived from the increased oil production will more than offset the additional expenditures and lost or deferred revenues incurred by gas injection. The most common source of gas for gas injection is the gas produced from the reservoir.
Which type of energy is least important to oil recovery?
In ranking the types of energy in order of least importance to oil recovery, the energy of the compressed water and rock originally within the reservoir is probably the least important because of the relatively low compressibilities of water and rock.
Why does oil not expand?
The oil in saturated, black-oil and volatile-oil reservoirs does not expand but contracts during pressure depletion because of the release of dissolved gas. Because the overwhelming majority of expansion-drive reservoirs are gas-drive reservoirs, the term oil-drive reservoir is rarely used.
Why is primary recovery also called pressure depletion?
Primary recovery is also sometimes referred to as pressure depletion because it necessarily involves the decline of the reservoir pressure. This article provides an overview of types of reservoir energy and producing mechanisms (drive mechanisms).
Why is compressed gas important?
Of the energies of the compressed fluids, the effects of compressed gas are undoubtedly the most important because of the greater compressibility of gas. The effects of compressed gas are important even if there is not much free gas initially present, as in the case of an initially undersaturated oil reservoir.
How do gravity forces affect oil recovery?
Gravitational forces can be a major factor in oil recovery if the reservoir has sufficient vertical relief and vertical permeability. The effectiveness of gravitational forces will be limited by the rate at which fluids are withdrawn from the reservoir. If the rate of withdrawal is appreciably greater than the rate of fluid segregation, then the effects of gravitational forces will be minimized.
What is the difference between oil and water in a reservoir?
Water within the reservoir refers to the water that is originally present within the reservoir at the time of discovery. Oil within the reservoir refers to the oil phase that is originally present at discovery or that may form from the condensation of volatilized oil upon pressure release.
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.
How does gas expansion work?
Free gas in a gas reservoir or in the gas cap of an oil reservoir expands to replace produced hydrocarbons. In an oil system, this expansion slows the rate of fluid pressure drop in the reservoir and supports hydrocarbon production. Pressure drops in proportion to the volume of hydrocarbon removed from the reservoir and the quality of the reservoir. Reservoirs with gas expansion drives have, at most, a limited aquifer.
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.
What happens when gas is 5-10% free?
At about 5–10% free gas in the reservoir, the bubbles coalesce and the gas moves toward the wellbore as a separate flowing phase. When this happens, oil production drops and gas production increases rapidly because of the increased relative permeability to gas.
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.