Oil and Gas Flashcards
What are fossil fuels?
Hydrocarbon deposits resulting from high pressure-temperature transformation by earth stresses of plant and animal (plankton) remains
What are some types of conventional fossil fuels?
Coal, light oil and natural gas
What are some non-conventional fossil fuels?
Heavy oil, tar sands,oil shales
gas shale, gas hydrates, coalbed methane
When does OPEC forecast that oild demand will plateu?
2040 - 109.3 million barrels a day
How much oil is there in the world?
3000 billion barrels ultimate
1000 billion bbl produced
1300 billion bbl in reserves
YTF - 400-700 bllion bbl
What does YTF stand for?
Yet to find
What is the global production of oil?
67 million barrels a day from 850, 000 wells
How many fields are in the middle east?
150
produce 17 million barrels a day of oil
What does E&P stand for?
exploration and production
What is exploration?
The process of finding new, previously undrilled oil and gas accumulations.
What do we need to identify to find oil and gas accumulations?
- new sedimentary basins
- understanding source/ resevoir seal distribution
- Identifying new prospects and leads
- drilling exploration wells to prove-up new reserves/ resources
- mainly involvy geology and geophysics
What is production?
The process of appraisal, development planning and resevoir management (‘production’) in order to produce and sell oil and gas
What needs to be identifyed for production?
- Field appraisal: resevoir and fluid types, reserves volumes
- devlopment planning: platforms, wells, pipelines, depletion etc.
- fluid production, injection, depletion, improved/ enhanced recovery etc.
- mainly involves geology, geophtsics and petroleum engineering
What was involved in the oil industry in the 90s?
Upstream:
(exploration, development and production)
Midstream:
(Intermediate processing: LNG, GTL, upgrading
Downstream:
(refining, transportation, distribution, storage, retailing)
Pipeline and marine
How do we look for oil?
- start with sedimentary basins
- look for world class source rocks
- generation and migration
- resevoir
- trap
What do we look for in world class source rocks?
7 geological intervals well known from global studies
What do we look gor in oil generation and migration?
- sufficient heat flow and major structural elements
What do we look for in a resevoir?
- thick permeable sandstones and carbonates
- the major deltas and carbonate platforms through geological time
What do we look for in a trap?
- Giant structures sealed by mudstones or salt
What is a trap?
A geological structure affecting the resevoir rock and caprock of a petroleum system allowing the accumulation of hydrocarbons in a resevoir
What are the two kinds of traps?
- stratigraphic or structural
Describe a trap?
A capping layer, with a later of oil and gas underneath, a laer of water, and then rock and source rock. The source rock emite oil and gas with heat, which comes from the crust, and the migration of oil to the surface is throgu buoyancy
What makes a good resevoir?
A porous, poorly graded later of rocks
What happens in maturation?
Kerogen is converted into petroleum
What forces petroleum up?
Overpressure due to volume expansion
What temperature is required for the source rock to become petroleum?
between 100-150 C
What are the different types of traps?
- anclinal (upside down V)
- Fault trap (geological shift, causing il, gas and water to be trapped
- unconformity trap (layer of rock over the top of the trap,
As we can’t actually dig under the surface to see the traps, how do we find them?
- surface geology
- potential fields methods
- reflection seismic
What is involved in surface geology surveying?
Assume that the structure in the subsurface is realted to the strucutre at the surface
- extremely succesfil in ‘the old days’
- nowadays helped by satellite imagery
What is involved in potential field methods of surveying?
Mostly gravity, magnetics and electro magnetics
measure trends and anomalies
- rather imprecise, allowing only to see major structural features (basins and highs)
- often used in initial stages of exploration to select areas to be covered with seismic data
What is involved in reflection seismic surveying?
imaging the subsurface by reflected sound waves. Can use explosives, compresed air, vibrators, ‘thumpers’
- onshore and offshore, easier offshore
- most important imaging/ detection tool, which has been phonmenally improved in accuracy over the past decades due to advances in computing
- nowadays can directly producce ‘geological cross-sections’ of the earth
- sometimes oil and gas can be seen directly on seismic data
How is a sedimentary basin found from the air?
a sedimentary basin will have a drop in magnetic field
What is reflection seismic?
- visalises contrasts in acoustic properties, harder and softer rocks
- hardness is called ‘acoustic impedance’
- it’s the product of density and velocity of the rock
- oil and gas filled porosity tends to make the rock softer (then water filled porosity) and is therefore potentially visible on seismic
What is the problem with reflection seimsic surveying?
- low resolution due to the wavelengths of the signals used
How is reflection seismic data aquired?
- Source is triggered - acoustic waves into ground
- signals are digitally recorded and processed
- resulting “data” when properly processed can reflect the structure of strata in the subsurface
How are land seismic surveys done?
geophones (seismic sensors) are laid out along the survey line
line of explosives are placed in a shot hole a few feet below the surface or a vibroseis source is used
- the vibrator is a metal plate whch is mounted on a truck and vibrated at precise frequencies
How are land surveys done on mountains?
using geophones is the best way, cementing them in yields the best results
dyamite causes too much damage
How are marine seismic surveys done?
offshore seismic sensors (hydrophones) are towed within long streamers by a boat
air guns serve as the energy source for this
How does a drilling system work?
It is a closed loop, where mud is injected into the bored holes.
The mud has several functions
- Water or oil based
- choice dependent on conditions
What is the purpouse of mud in drilling?
- well control
- cleaning the hole
- cutting agent
- hole stability
- formation evaluation
How do we design a well?
- we case off the hole and reduce the hole size as we go down
this redueces the risk of hole collapse - instability that usually increases with open hole itme - prevent fracture failure at shallower depths as a result of high weight mud
- to siolate overpressured zones which could lead to well control problems
what are the different tpes of drilling rigs?
- land rigs 8-70k a dayup to 9000m depth
- semi-subs 60-180 k a day
2250 m of water - jack-ups 30-300k a day <50m of water
- drill ships (3000m of water ) $1 mil a day
Critical issues from the macondo well?
- poor/ absent cement job
- 1400 psi presure on the drill line when displacing mud with sea water (should have been 0 or -ve)
- failure of BOP to function correctyl
- no effective well capping in place for this water depth
How was the macondo well problem fixed?
a ‘top hat’ that sat on top of the well
How much oil, in how long was discharged into the see from macondo?
152 days, 4.9 billion barrels
