What is an 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 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 is a volumetric reservoir?

A volumetric dry gas reservoir is completely enclosed by low-permeability or completely impermeable barriers and does not receive pressure support from external sources, such as an encroaching aquifer.

What is gas cap reservoir?

1. n. [Well Completions] The gas that accumulates in the upper portions of a reservoir where the pressure, temperature and fluid characteristics are conducive to free gas. The energy provided by the expansion of the gas cap provides the primary drive mechanism for oil recovery in such circumstances.

What is saturation pressure in reservoir?

A saturated oil reservoir has a bubble point pressure of 2100 psi at 175°F.

What is ordinary black oil?

Black oil is often called low shrinkage crude oil or ordinary oil. Black oils are dark in color indicating the presence of heavy hydrocarbons. It is characterized as having initial gas-oil ratios of 2000 scf/stb or less.

What is Waterdriver mechanism?

1. n. [Well Completions] A reservoir-drive mechanism whereby the oil is driven through the reservoir by an active aquifer. As the reservoir depletes, the water moving in from the aquifer below displaces the oil until the aquifer energy is expended or the well eventually produces too much water to be viable.

What is a depletion drive reservoir?

A Depletion Drive Reservoir is a gas reservoir from which gas is recovered by expansion as the gas pressure falls with the production of gas originally in place. The reservoir can therefore be treated as if it were a closed tank.

What is solution gas 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. … When reservoir pressure reaches a bubble point, oil becomes saturated and free gas will present in a reservoir.

What is meant by a gas cap drive?

1. n. [Enhanced Oil Recovery] A type of reservoir-drive mechanism in which the energy for the transport and production of reservoir fluids is provided by the expansion of gas either in the gas cap or inside the oil phase.

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What is undersaturated oil?

PetroWiki. An oil with less gas than its solubility capacity.

What is gas reservoir engineering?

Gas Reservoir Engineering provides the undergraduate as well as the graduate student with an introduction to fundamental problem solving in gas reservoir engineering through practical equations and methods. Although much oil well technology applies to gas wells, many differences exist.

What is retrograde gas condensate?

The formation of liquid hydrocarbons in a gas reservoir as the pressure in the reservoir decreases below dewpoint pressure during production. It is called retrograde because some of the gas condenses into a liquid under isothermal conditions instead of expanding or vaporizing when pressure is decreased.

What is connate water saturation?

The state is usually achieved by flowing oil or gas through a water-saturated sample, or spinning it in a centrifuge to displace the water with oil or gas. … The related term connate water saturation is the lowest water saturation found in situ.

What is liberated gas oil ratio?

The gas:oil ratio is the volume of gas produced at standard temperature and pressure, in relation to the volume of oil produced at standard temperature and pressure, used as a measurement for reservoir fluids. Gas:oil ratio is defined as the ratio of the respective volumes of liberated gas and residual oil.

What is initial reservoir pressure?

Reservoir initial pressure is pi, and horizontal gas wells produce with a constant gas rate of qsc; From: Development of Volcanic Gas Reservoirs, 2019.

What is reservoir geology?

1. n. [Geology] A subsurface body of rock having sufficient porosity and permeability to store and transmit fluids.

What is the difference between black oil and volatile oil?

The distinguishing characteristic between volatile and black oils is the stock-tank-oil content of their equilibrium gases. Equilibrium gases liberated from volatile oils contain appreciable stock-tank or condensable liquids whereas the gases from black oils contain negligible stock-tank liquids.

What makes a good petroleum reservoir?

Properties of Petroleum Reservoirs Their important properties include pay zone thickness, lithology, rock porosity, rock total compressibility, and rock permeability. These properties affect fluid flow within the reservoir and thus well productivity.

How much oil is recovered from a water drive oil reservoir?

Oil recovery from water drive reservoirs typically ranges from 35 to 75% of the original oil in place.

What is free gas?

Gas that exists in the reservoir in the gaseous phase rather than in solution. As soon as formation pressure drops below the bubblepoint, gas is evolved. This is referred to as free gas while it is in the reservoir.

What is secondary gas cap?

As the reservoir pressure in a solution-gas system falls, liberated gas may migrate to the top of the reservoir, producing a secondary gas cap. If the oil is produced rapidly, gas bubbles may form and expand in the pores of the rocks, which can impede oil flow through the reservoir.

What is gravity drainage?

Gravity drainage is a recovery process in which gravity acts as the main driving force and where gas replaces the voidage volume. In other words, it is a gas/oil displacement in which gravity forces are dominating.

What is compaction drive?

PetroWiki. If pore volume contraction contributes prominently to overall expansion while the reservoir is saturated, then the reservoir is classified as a compaction drive.

What are examples of drive mechanism?

• Water drive.
• Gas expansion.
• Solution gas.
• Rock or compaction drive.
• Gravity drainage.

What is an oil leg?

The overlying gas zone is referred to as a primary gas cap. In addition to free gas, gas caps usually contain connate water and residual oil. The underlying oil column is sometimes referred to as an oil leg. … Producing wells usually are completed only in the oil leg to minimize gas production.

What is free gas initially in place?

Original oil in place (OOIPoriginal oil in place) and original gas in place (OGIPoriginal gas in place) refer to the total volume of hydrocarbon stored in a reservoir prior to production.

Why is Bubblepoint pressure important?

Importance of Bubble Point Pressure Bubble point pressure is the pressure at which the first bubble of the gas will come out of the liquid oil solution (McCain, 1990). … This will affect the oil effective permeability and in turn the oil production will diminish.

What is low shrinkage oil?

Undersaturated black oils, sometimes referred to as “low shrinkage oils,” are single-phase liquid systems that reside in reservoirs with an original temperature that is significantly lower than critical temperature, TC. … The phase diagram for the crude oil is determined by the composition of the crude oil.

What is reservoir pressure?

Reservoir Pressure and Interlayer Pressure Difference Reservoir pressure means the pressure of the fluid in pores and fractures, which reflects the energy of the reservoir and is the power pushing the fluid to move in the reservoir.

How do you increase reservoir pressure?

Secondary recovery: injection of gas or water A “secondary recovery” is required to reenergize or “pressure up” the reservoir. This is accomplished by injecting gas or water into the reservoir to replace produced fluids and thus maintain or increase the reservoir pressure.