chapter 5 vocabulary reservoir performance Flashcards
Any substance that flows and yields to any force tending to change it shape is a . Both liquids and gases are fluids.
Fluids
the density measure used for petroleum liquids. Expressed in degrees. The higher the______the lighter the liquid. formula for _____ = 141.5/S.G. – 131.5 (S.G. - specific gravity).
API gravity
Defined as hydrocarbons that are in a gaseous state at standard conditions of one atmosphere (14.7 psi) and 60deg F. Included are methane, ethane, propane, and butane.
Petroleum Gases
the minimum saturations of oil, water, or gas in the reservoir that cause the fluid to be a continuous medium, and therefore producible.
Critical saturations
- gas that is in solution in the oil under the initial reservoir pressure and temperature. Under these conditions, the gas is in the liquid state.
Solution gas
the percent or fraction of the reservoirs original oil in place (OOIP) or original gas in place (OGIP) that will be recovered. Expressed in percent.
Recovery factor
is from solely gas reservoirs where no “black” (non-condensate) oil is present.
Non-associated gas
- includes solution gas and gascap gas. They both occur only in association with oil.
Associated gas-
is free gas trapped in the top of the structure above the oil leg.
Gas Cap-
ratio of gas to oil produced or in solution in the reservoir. Units are in ft3 /bbl. or m3 /bbl.
Gas oil ratio (GOR)-
Beta is the factor for the volume change undergone by the reservoir fluids when they are produced. In the case of oil, it is the ratio of the space occupied by a barrel of oil at reservoir conditions to the space occupied by a stock tank barrel (STB) of the oil. Most oils shrink when their solution gas dissipates at the surface and because of the cooler surface condition, so their Betas are greater than 1.
Formation volume factor (B)-
a fluids resistance to flow. The thicker and stickier the fluid. The higher its ______.
Viscosity (u)-
a light hydrocarbon liquid formed by condensation of petroleum compounds that were in the gaseous phase under initial reservoir conditions. It is highly volatile and from clear to a light yellow in color
Condensate
when a reservoir is above its ___ ___ __, it has no free gas—all gas is in solution in the oil. As the reservoir is produced and pressure declines, the _____ _____ ____ is reached. Gas comes of solution, forming a free gas saturation.
Bubble point pressure
is used to refer to all the artificial drive mechanisms such as waterflood, CO2 flood, steam injection, etc.
Enhance recovery- or improved recovery
producing the reservoir using only the natural reservoir energy.
Primary recovery
the initiation of additional recovery processes like waterflooding immediately without waiting for primary depletion.
Pressure maintenance
a process that adds energy to the reservoir following primary recovery. An example is waterflooding a depleted field.
Secondary recovery
follows secondary recovery. For example, CO2 flooding could follow waterflooding, which had followed primary recovery.
Tertiary recovery
know whats there, no two reservoirs behave identically when produced.
Fluid systems
naturally occurring near solid hydrocarbon. Must be mined.
Bitumen
tar or heavy oil, low-shrinking oils (black oils), high shrinking oils (volatile oil), condensate gas, wet gas, dry gas
Fluids
with more lighter ends than bitumen and small amount of gas in solution, it flows sluggishly through the reservoir
Tar or heavy oil
oils viscosity is low enough for it to move through the formation readily, normally commercially producible
Low shrinkage oils (black oils)
because of its low viscosity, volatile oil produces at high rates and it high Rs ( ) results in high good recovery factors
High shrinkage oils (volatile oils
hydrocarbons in reservoir are gaseous at initial conditions. During initial gas production, large quantities of condensate drop out in the surface facilities
Condensate gas
All hydrocarbons are in a gaseous state. When gas is produced, the associated cooling causes condensate to drop out in the surface facilities.
Wet gas
gas is composed primarily of methane with small amounts of ethane, propane, and butane. These reservoirs produce no condensate
Dry gas
most widespread reservoir drives. Four phases 1. Production starts, reservoir pressure declines rapidly to the bubble point. 2. The GOR (gas to oil ratio) dips below the solution GOR for a short period. 3. Gas saturation exceeded. 4. Depleted of it gas
Solution gas drive
have access to aquifers that provide water to replace some or all of volume fluids produced. Provide the highest recovery rates.
Water drive
free gas trapped in the top of the structure above the oil leg
Gas cap drive
pressure depletion of reservoirs.
Gravity drainage
- overpressured reservoirs. North sea chalk fields example of this
Compaction drive
there are no liquid hydrocarbons in the formation. Gas has lower viscosity than oil (
Wet and dry gas reservoirs
initially very profitable, but it can fall off dramatically; loss of revenue from condensate sales; liquid build up in the formation restrict its permeability to gas; good candidate for recycling if found in remote area from the market.
Retrograde condensate gas reservoir
dominant recovery method, used worldwide. Advantages saltwater availability, chemical compatibility, equipment availability, safe non toxic non flammable
Waterflooding
saltwater and oil do not mix.
Fluid displacement
water not oil adheres tightly to the surface of the sand grains.
Wettability
the attraction between a surface and its wetting fluid.
Capillary forces
how much the reservoir rock is actually contacted by the advancing water. It is effected by its mobility ratio.
Sweep efficiency
fluids ease of movement through the reservoir.
Mobility ratio
- five spot pattern- water injected to gently encroach from the perimeters of the field
Injection well patterns
used to inject heat into the formation
Thermal recovery
compressed air is forced down the well providing oxygen to ignite the oil
Fire flooding
- steam injected is used in fields that are 2 ½ acres (shallow wells 200-500ft)
Steam flooding
huff and puff. The most successful thermal recovery.
Cyclic steam flooding
mix with
Miscible
reservoir is flooded with fluid that are miscible the reservoir oil
Miscible flooding
the CO2 combines with the oil, swelling and reducing its viscosity. Used the most
Carbon dioxide flooding
is miscible in crude oil. But lpg is not recovered
Liquefied petroleum gas (LPG)
waste gases from burning oils used.
Flue gas
only at high pressures
Nitrogen
cost is too great to use
Detergents
unpleasant and unsafe to handle
Alkaline (caustic)-
the high cost of chemicals limits commercial application
Mobility ratio improvement
- bacteria used to reduce oil viscosity ( to slow )
Microbial floods
estimated volumes of crude oil, condensate, etc., anticipated to be commercially recoverable from known accumulations
Reserves
can be estimated, must have operational facilities to process and transport the reserves to market.
Proved reserves
can’t estimate; divided in two risk classification; probable and possible
Unproved reserves
because of uncertainties in both the counting and pricing of reserves while they are still in the ground.
Reserves are not assets
Both liquids and gases are
fluids
When there is a gas cap, the reservoir is at
bubble-point pressure
Oil viscosity is measured in
centipoise (cp)
