Stratigraphy and hydrocarbonsStratigraphy and hydrocarbons

ERTH 1010 & 1100

DepositionDeposition

This simple example shows how the deposited strata is both spatial and temporal changing.

With increasing time, deposits record these changes.

General rulesGeneral rules

• Sediments are largely associated with water• Supermarine - streams, rivers, lakes• Marine - Shore, shelf, basin• High energy - steep drainages and wave

action - sands or coarser• Low energy - ponded water: lakes, lagoons,

basins, shallow drainages - silts and clays• Relatively free from terrigenous (continental)

clastic particles - good for life - carbonates

Energy changesEnergy changes

Faster flow

Slower flow

Deposition changes with location in a stream

As a stream makes a bend, water flow increases on the outside of the curve - erodes.

Inside the curve, deposition.

Oxbow lakesOxbow lakes

Meandering rivers may change channels (during flooding). This may strand former channels.

Catskill deltaCatskill delta

General relationshipsGeneral relationships

In the shoreline environment

The source of clastic particles is dominated by the land (delivered by streamflow)

Wave-sediment energies are typically greatest nearshore

Organisms prefer less silty waters - are abundant in shelf waters.

Forces along shoreForces along shore

Sedimentary environments are complex. Water energy is in the driver’s seat, but fluid dynamics is difficult to constrain.

Courtenay, Vancouver Is., B.C.

Barrier IslandsBarrier Islands

Mustang Is., TXMustang Is., TX

Adjacent to Corpus Christi, Mustang Island is a condo-haven, sport fishing port, and petroleum service port.

Hurricane free for 25 years!

Barrier islandsBarrier islands

Barrier islands are nothing more than loose sand - transient on short time scales.

Deposits in sectionDeposits in section

Shallow seafloorShallow seafloor

Shallow water can be a boon to life - carbonate formation

Corals are example of autotrophic -hetrotrophic symbiosis.

Sunlight helps feed the organism.

Thatcher Park, NYThatcher Park, NY

South of Albany - one of the world’s best examples of the shallow sea environment.

Helderberg group (largely carbonates).

Deltas and timeDeltas and time

Deltas form from low energy distribution of stream-borne sediments. With continued deposition, deltas extend outward into the basin.

Hydrocarbon formationHydrocarbon formation

• Biogenic deposition• Soft parts versus hard parts• Soft parts made of carbohydrates, fats,

proteins (C-O-H with P and N)• Preservation requires low oxygen (reducing

environments) remove O to get C-H

• The environments that produce materials that will become hydrocarbons are those that offend the average nose!

Small amounts

Largely in clastic sediments and rocks

Largely organic

Yet greatly important in everyday life – oil is one of the biggest drivers of first world

economies.

Even if you don’t own a car – all of the clothes you wear and the food you eat was transported to you.

Small amounts

Largely in clastic sediments and rocks

Largely organic

Yet greatly important in everyday life – oil is one of the biggest drivers of first world

economies.

Even if you don’t own a car – all of the clothes you wear and the food you eat was transported to you.

CH (Hydrocarbon)CH (Hydrocarbon)

Largely organic material - piles of dead plants and animals.

Compressed and heated over time.

Reducing (no extra O) conditions (chemical or biochemical).

Largely organic material - piles of dead plants and animals.

Compressed and heated over time.

Reducing (no extra O) conditions (chemical or biochemical).

Q: what type of rocks are being formed in the above diagram?

The start…The start…

Oil’s originsOil’s origins

Oil and originsOil and origins

Hydrocarbon takes time to “cook”

But more importantly, it needs a way to accumulate - move from the source region into an area from which it can be economically extracted.

Hydrocarbon takes time to “cook”

But more importantly, it needs a way to accumulate - move from the source region into an area from which it can be economically extracted.

Organic material that may produce petroleum is called Kerogen.

For a given temperature, kerogens made of buried algae yield more petroleum than leafy, woody, or peat materials

Organic material that may produce petroleum is called Kerogen.

For a given temperature, kerogens made of buried algae yield more petroleum than leafy, woody, or peat materials

Q: which organic material yields the most petroleum?

Kerogen MaterialKerogen Material

CrackingCracking

The process of making hydrocarbon involves several steps – obviously not all organic matter becomes oil and gas.

Specific conditions with respect to heating and low oxygen levels are required.

The process of making hydrocarbon involves several steps – obviously not all organic matter becomes oil and gas.

Specific conditions with respect to heating and low oxygen levels are required.

What is being made?

C-H from C-H-O molecules.

Methane (CH4) to asphaltenes

Cn, n is 1 to 60, increasing n changes state.

In CH4, n is 1.

What is being made?

C-H from C-H-O molecules.

Methane (CH4) to asphaltenes

Cn, n is 1 to 60, increasing n changes state.

In CH4, n is 1.e.g. Straight-chain parafins

n = 1-4 gas

n = 5-16 liquid

n > 16 solid

e.g. Straight-chain parafins

n = 1-4 gas

n = 5-16 liquid

n > 16 solid

Hydrocarbon general usage names

Oil: predominantly liquid hydrocarbon

Natural gas: predominantly gas hydrocarbon

Coal: Hydrocarbon with substantial amounts of other material (e.g. oxygen-organics)

Hydrocarbon general usage names

Oil: predominantly liquid hydrocarbon

Natural gas: predominantly gas hydrocarbon

Coal: Hydrocarbon with substantial amounts of other material (e.g. oxygen-organics)

Paraffins (Arkanes) CnH2n+2

Cycloparaffins (Cycloalkanes) CnH2n

Aromatics (Arenes) CnH2n-6

Olefin (Alkenes) CnH2n-2

Asphalitics (N, S, and O)

Paraffins (Arkanes) CnH2n+2

Cycloparaffins (Cycloalkanes) CnH2n

Aromatics (Arenes) CnH2n-6

Olefin (Alkenes) CnH2n-2

Asphalitics (N, S, and O)

Q: which hydrocarbons burn more efficiently?

Petroleum nomenclaturePetroleum nomenclature

Oil is not very soluble in water (vice-versa) because of their different molecular structure.

Oil is not very soluble in water (vice-versa) because of their different molecular structure.

Water and oil are largely separate in nature – oil floats on water.

Water and oil are largely separate in nature – oil floats on water.

Q: why does oil float on water?

Seismic surveyingSeismic surveying

Reflection SeismologyReflection Seismology

Generating your own mini-earthquakes

Collect the reflected signal with a series of small seismometers (geophones).

Do the math to stack the data

Do the math to spatially distribute the raypaths as a time function

Do the math to convert travel time into depth

Make a geologically reasonable interpretation of significant reflectors

Seismic SurveyingSeismic Surveying

Offshore exploration requires most work be done at the surface (on floating vehicles)

The seismic waves travel through the water.

Seismic imagingSeismic imaging

North SeaNorth Sea

Production drilling requires ability to crush and remove rock using a drill. The bit is supported by large segments of pipe, extended sequentially with increasing depth. A highly specialized fluid (mud) is used to float out rock fragments and lubricate stem and bit.

Production drilling requires ability to crush and remove rock using a drill. The bit is supported by large segments of pipe, extended sequentially with increasing depth. A highly specialized fluid (mud) is used to float out rock fragments and lubricate stem and bit.

DrillingDrilling

Drilling offshoreDrilling offshore

When oil is finally encountered it may be under some pressure - however, this pressure is released over time. Eventually, the oil must be pumped out of the rock pores.

When oil is finally encountered it may be under some pressure - however, this pressure is released over time. Eventually, the oil must be pumped out of the rock pores.

Additional treatments, such as “hydrofracking” and gas injection may help to maintain production levels.

Additional treatments, such as “hydrofracking” and gas injection may help to maintain production levels.

From Hunt, 1979

Crude oil is a mixture of hydro carbons – some oxidize easier than others.

Distillation separates hydrocarbons into groups – from light hydrocarbons in gasoline to heavy in motor oil

Crude oil is a mixture of hydro carbons – some oxidize easier than others.

Distillation separates hydrocarbons into groups – from light hydrocarbons in gasoline to heavy in motor oil

RefiningRefining

HydrocarbonsHydrocarbons

We’ve previously seen viscosity increase in earth materials as a function of polymerization.

Note a similar effect in these refined materials based on crude oil.

Recall that some petroleum generation uses gas to “chase out” sluggish oil. That gas is CO2, typically removed from natural gas.

Recall that some petroleum generation uses gas to “chase out” sluggish oil. That gas is CO2, typically removed from natural gas.

We might be able to pump the CO2 released at power plants into these former oil reservoirs for long term storage.

We might be able to pump the CO2 released at power plants into these former oil reservoirs for long term storage.

BPBP

SequestrationSequestration

EnergyEnergy

SourcesSources

Oil is not everywhereOil is not everywhere

There is more gasThere is more gas

Natural gas is somewhat easier to find, particualrly in North America

However, gas is difficult to transport.

Gas wells generally have to be connected to a pipeline.

Compressing gas into a liquid is expensive and energy intensive

ANWRANWR

WhereWhere

How muchHow much

HydrocarbonsHydrocarbons

Coal and contentCoal and content

MiningMining

MiningMining

FossilsFossils

Coal in North AmericaCoal in North America