10. Reservoir Engineering Flashcards
Why is porosity important?
Porosity does NOT have any significant impact on fracturing. It is used for forecasting reserves of hydrocarbons and to see if economically fisable.
What is the relation of grain size vs. Porosity in sandstone?
Dependent on orientation/packing/sorting not grain size
What’s primary porosity and why is it important in sandstone?
Formed duriing Deposition. Can be intergranular or intragranular. In sandstones intergranular is typical and connects pores through throats. Sandstone is most prevalent
What’s secondary porosity and why is second porosity important in carbonates?
Formed within reservoir after deposition as a subsequent or separate porosity system. Can be a result of chemical leeching, biological/mechanical breakdown of minerals
Define saturation
Amount of fluid per unit volume; Tell how much we coould possibly recover
Define OOIP/OGIP
Original Oil In Place/Original Gas In Place
What is typical reservoir fluid?
Crude oil systems, natural gages, reeservoir water systems
List typical oil properties
bubble-point pressure, oil formation volume factor, crude oil viscosity
List typical gas properties
Specific gravity
What is critical pressure and temperature?
Beyond critical point liquid and gas exist at same time; Critical temperature all three phases co-exist
List and compare 5 typical reservoir fluids
Black Oil, Volatile Oil, Retrograde Gas, Wet Gas, Dry Gas;
Explain phase diagram
Go from 1 to 8
Define permeability
the ability to flow fluid; ability to flow a fluid of one ccentipoise viscosity at a rate of one cubic centimeter per second at a prerssure drop of one atmosphere per centimeter
Darcy’s equation for linear flow
k=
Compare permeability vs. Pore size
you can have large pores that are not connected
Compare permeability vs. Porosity
more porosity means possibly better permeability
Explain Absolute/Effective/Relative permeability
absolute permeability only has one fluid, effective permeability is 1 phase if more than 1 phase is present, relative is effective over absolute permeability
Understand Darcy’s Equation for PSS flow
considers average reservoir pressure, average reservoir radious, volume factor, and skin
Define drive mechanism
Usually pressure difference is how hydrocarbon is moved; Can be done by expansion or invasion; unsaturated oil (above bubble point) expands and invads original oil bearing reservoir
List the most common drive mechanism
water?
What is the reservoir pressure conditions for solution gas drive?
P r > Pb; Pr is reservoir and Pb is bubble point
What is the reservoir pressure conditions for gas cap drive
Pr<Pb
What is the benefit for water drive?
The oil being produced is replaced by water, keeping the pressure constant if the replacement of produced oil and gas by water influx is close to 1:1; Delta P will be almost constant
What problem might associate with water drive and gas drive
After initial “dry” oil produced, water may be produced as volume of oil in reservoir decreases.
