UNCONVENTIONAL HYDROCARBON

By-Swapnil PalIMT Geological Technology

• Known for a long time and was easy to exploit for use in small quantities.

• In southern California oil was mined from the early 1860s to the 1890s because the heavy oil would not flow to the wells.

• Tar sands are sandstone reservoirs which have been filled with oil at shallow depth <2 km (<70–80◦C) so that the oil has become biodegraded. Reservoir rocks which have been buried more deeply and then uplifted before the oil migration may be sterilized at higher temperatures and are less likely to be biodegraded.

HEAVY OIL AND TAR SANDS

INTRODUCTION

• Tar sand contains asphaltic oil rich in asphaltenes and resins. It has a high content of aromatics and naphthenes compared to paraffins, and a high con-tent of nitrogen, sulphur and oxygen (NSO).

• Most of the hydrocarbon molecules have more than 60 carbon atoms and the boiling point and viscosity are therefore very high.

• The viscosity of the biodegraded oil is very high and the oil must be heated so that the viscosity is reduced before it can be produced by drilling wells.

HEAVY OIL AND TAR SANDS

INTRODUCTION

• Heating of reservoir. heating can be achieved by

soaking the reservoir with injected steam. This is called cyclic steam injection.

burn some of the oil in the subsurface.

heat the oil electrically, possibly powered by a nuclear reactor to reduce the CO2 emissions from burning oil to produce heat.

• Freezing the ground at a distance from the well.

HEAVY OIL AND TAR SANDSMETHODS OF EXTRACTION

Oil are also extracted from tar sand. The tar sands in Alberta, Canada

(Athabasca) of Middle Cretaceous age (Aptian, 100 million years) contains 1.7 trillion bbl (270×109m3) of bitumen in place, comparable in magnitude to the world’s total proven reserves of conventional petroleum.

The oil (tar) is very viscous and may be denser than water (API<10). Only about 20% is close enough to the surface to be economically mined and the rest must be heated in place. A cubic meters of oil, mined from the tar sands, needs 2–4.5 m3 of water.

Oil may be extracted by steam-assisted gravity drainage (SAGD).

TAR SAND

HEAVY OIL RECOVERY METHODS

Primary Recovery Method

Cold EOR

Thermal Production Method

THERMAL OIL RECOVERY

Cyclic Steam Stimulation (CSS)

Steam Assisted Gravity Drainage (SAGD)

CYCLIC STEAM STIMULATION

Stage 1: High pressure steam injected Stage 2: Major portion of reservoir is thoroughly saturatedStage 3: Production phase When production phase declines, another cycle of stream injection begins.

STEAM ASSISTED GRAVITY DRAINAGE (SAGD)

2 horizontal wells are drilled.

Injected steam forms a “steam chamber”.

Steam and gases rise filling the void left by oil.

The condensed water and crude oil or bitumen is recovered to the surface by pumps

STEAM ASSISTED GRAVITY DRAINAGE (SAGD)

2 horizontal wells are drilled.

Injected steam forms a “steam chamber”.

Steam and gases rise filling the void left by oil.

The condensed water and crude oil or bitumen is recovered to the surface by pumps

IL SHALE

SALIENT FEATURES

• They are not oils!

• They are usually mudstones and shale, with a high organic content (TOC), which have not been buried deeply enough to become sufficiently mature for most of the hydrocarbons to be generated.

• The can produce oil after undergoing crushing and pyrolysis.

OIL SHALE

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Oil Shale Resources V/s Oil Reserves

GEOLOGY

• Organic rich sedimentary rock, belongs to sapropel fuel group.• Oil shale vary in mineral content, chemical composition, age,

type of kerogen.• Low solubility in low-boiling organic matter and generates

liquid organic product on thermal decomposition.• They differ from bitumen-impregnated rock, humic coals and

carbonaceous shale. • Maturation of oil shale does not exceed meso-catagenetic.

OIL SHALE EXTRACTION

• Oil shale must be mined.• After excavation, oil shale

must undergo retorting.• Then it undergoes the

process of pyrolysis.

Clayey rock

Crushing

pyrolysis

Shale Oil

OIL SHALE EXTRACTIONPROBLEMS

o This process adds two extra steps to the conventional extraction process.

o Oil shale presents environmental challenges as well.

o There's also the matter of the rocks.

Clayey rock

Crushing

pyrolysis

Shale Oil

OIL SHALE EXTRACTIONSOLUTION

o Royal Dutch Shell Oil Company has come up with In Situ Conversion Process (ICP).

o The rock remains where it is.o holes are drilled into an oil

shale reserve and heaters are lowered into the earth.

o The kerogen seeps out which is collected on-site and pumped to the surface.

OIL SHALE EXTRACTIONSOLUTION

Freeze Wall

GAS HYDRATES

WHAT ARE THEY?

Gas hydrates are crystalline solids almost like ice, consisting of gas (mostly methane) surrounded by water.

It is stable at high pressures and low temperatures.

When gas hydrates dissolve (melt) one volume of gas hydrate produces 160 volumes of gas.

The source of the methane is mostly biogenic, from organic rich sediments, but gas hydrates may also fill the pores in sand beds.

During the glaciations gas hydrates were more widespread than now and occurred also beneath the seafloor in basins like the North Sea.

Gas hydrates are potentially a very important source of gas.

FEW SALIENT POINTS ABOUT GAS HYDRATES

• Hydrates store immense amounts of methane, with major implications for energy resources and climate, but the natural controls on hydrates and their impacts on the environment are very poorly understood.

• The immense volumes of gas and the richness of the deposits may make methane hydrates a strong candidate for development as an energy resource.

• Results of USGS investigations indicate that methane hydrates possess unique acoustic properties.

• Methane, a "greenhouse" gas, is 10 times more effective than carbon dioxide in causing climate warming.

FEW SALIENT POINTS ABOUT GAS HYDRATES

• USGS investigations indicate that gas hydrates may cause landslides on the continental slope.

COAL BED METHANE

INTRINSIC PROPERTIES OF AFFECTION GAS PRODUCTION

• Porosity: 0.1-10%• Adsorption Capacity: 100-

800 SCF/ton• Fracture Permeability• Thickness of formation and

initial reservoir pressure

Coal cleats

Butt cleats

Face cleats

SALIENT FEATURES

• Coal is the major source of methane gas.

• Coal is a low permeability reservoir. Almost all permeability is due to fractures, which in coal are in form of cleats and joints.

PRODUCTION & EXTRACTION

• Coal beds are an attractive prospect for development because of their ability to retain large amounts of gas

• The amount of methane in a coal deposit depends on the quality and depth of the deposit.

• In CBM development, water is removed from the coal bed (by pumping), which decreases the pressure on the gas and allows it to detach from the coal and flow up the well.

• In the initial production stage of coal bed methane, the wells produce mostly water.

• Depending on the geological conditions, it may take several years to achieve full-scale gas production. Generally, the deeper the coal bed the less water present, and the sooner the well will begin to produce gas.

PRODUCTION & EXTRACTION

• The amount of water produced from most CBM wells is relatively high compared to conventional gas wells because coal beds contain many fractures and pores that can contain and move large amounts of water.

• CBM wells are drilled with techniques similar to those used for conventional wells.

• As with conventional gas wells, hydraulic fracturing is used as a primary means of stimulating gas flow in CBM wells.

• The methane desorption process follows a curve (of gas content vs. reservoir pressure) called a Langmuir isotherm.

• As production occurs from a coal reservoir, the changes in pressure are believed to cause changes in the porosity and permeability of the coal. This is commonly known as matrix shrinkage/swelling.

PRODUCTION & EXTRACTION

The potential of a particular coal bed as a CBM source depends on the following criteria: High Cleat

density/intensity. Maceral composition. A high vitrinite composition

is ideal for CBM extraction, while inertinite hampers the same.

SHALE GASThe game changer!

INTRODUCTION

Shale gas refers to natural gas that is trapped within shale formations. Organic-rich shale which have been buried to depths where most of the oil and gas has been generated and expelled may nevertheless contain considerable amount of gas.

The gas remaining in these shale is present in very small pores and may also be partly adsorbed on remaining organic matter or its residue (coke) and on clay minerals.

The shales have been uplifted and may therefore have small extensional fractures, but they must be hydro fractured by water injection to increase the permeability.

EXTRACTION

• The gas deposits are usually found in rocks that have low permeability, ruling out the possibility of regular drilling.

• The most commonly used method is called fracking (hydraulic fracturing).

• As opposed to vertical drilling for traditional gas, in this case horizontal drilling is carried out. 

• What “changed the game” was the recognition that one could “create a permeable reservoir” and high rates of gas production by using intensively stimulated horizontal wells.

TWO MAJOR DRILLING TECHNIQUES ARE USED TO PRODUCE SHALE GAS

Horizontal DrillingHorizontal drilling is used to provide greater access to the gas trapped deep in the producing formation. First, a vertical well is drilled to the targeted rock formation. At the desired depth, the drill bit is turned to bore a well that stretches through the reservoir horizontally, exposing the well to more of the producing shale.

Hydraulic FracturingIt is a technique in which water, chemicals, and sand are pumped into the well to unlock the hydrocarbons trapped in shale formations by opening cracks (fractures) in the rock and allowing natural gas to flow from the shale into the well. When used in conjunction with horizontal drilling, hydraulic fracturing enables gas producers to extract shale gas at reasonable cost.

CONCLUSION

• Conventional oil production has peaked and is now on a terminal, long-run global decline. However, contrary to conventional wisdom, which many embraced during back-to-back oil crises in the 1970s, oil is not running out. It is, instead, changing form—geographically, geologically, chemically, and economically.

• We are approaching the end of easily accessible, relatively homogeneous oil, and many experts claim that the era of cheap oil may also be ending.

• Many new breeds of petroleum fuels are nothing like conventional oil. Unconventional oils tend to be heavy, complex, carbon laden, and locked up deep in the earth, tightly trapped between or bound to sand, tar, and rock. Unconventional oils are nature’s own carbon-capture and storage device, so when they are tapped, we risk breaking open this natural carbon-fixing system. Generally speaking: the heavier the oil, the larger the expected carbon footprint.

CONCLUSION

From extraction through final use, these new oils will require a greater amount of energy to produce than conventional oil. And as output ramps up to meet increasing global demand for high-value petroleum products, unconventional oils will likely deliver a higher volume of heavier hydrocarbons, require more intensive processing and additives, and yield more byproducts that contain large amounts of carbon.