Crude oil exploration

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CRUDE OIL EXPLORATION

Transcript of Crude oil exploration

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CRUDE OILEXPLORATION

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INTRODUCTION TO CRUDE

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DESCRIPTION

CRUDE OIL, COMMONLY KNOWN AS PETROLEUM IS ANATURALLY OCCURRING, TOXIC, FLAMMABLE LIQUIDFOUND IN GEOLOGICAL FORMATIONS AT VARIABLEDEPTHS IN THE EARTH’S CRUST. IT IS COMPRISED OFCOMPLEX MIXTURE OF HYDROCARBONS, ORGANICCOMPOUNDS & SMALL AMOUNTS OF METAL. ALKANESARE THE MAIN HYDROCARBON FOUND IN CRUDE OIL.CRUDE OIL IS A SMELLY, YELLOW-TO-BLACK LIQUID &IS USUALLY FOUND IN UNDERGROUND AREAS CALLEDRESERVOIRS.

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CRUDE OIL COMPONENTS

ON AVERAGE, CRUDE OILS ARE MADE OF THEFOLLOWING ELEMENTS OR COMPOUNDS:CARBON-84%HYDROGEN-14%SULPHUR-1 TO 3%NITROGEN & OXYGEN-LESS THAN 1%METALS-LESS THAN 1%SALTS-LESS THAN 1%

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CATEGORIES OF CRUDE OIL

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CRUDE OIL IS PARTICULARLY CLASSIFIED INTYPES BY THE CONTENT OF SULPHUR AND THEDENSITY OF THE OIL. THESE STANDARDS ARESET BY THE AMERICAN PETROLEUM INSTITUTE.ACCORDING TO THE API, THE GRAVITY OF THEOIL SIGNIFIES THE DENSITY. OILS WITH AGRAVITY OF MORE THAN 40 DEGREES IS CONSIDERED AS LIGHTER OIL, WHILE OIL WITH AGRAVITY OF LESS THAN 20 DEGREES ISCONSIDERED AS HEAVY OIL.

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IT IS ALSO A FACTOR THAT TAGS THE OIL ASSWEET & SOUR. SULPHUR IS AN ACID & MOREAMOUNT OF SULPHUR IN THE OIL,TERMS THE OILAS SOUR & LESS AMOUNT OF SULPHUR TERMSTHE OIL AS SWEET. BUT, MOSTLY, CRUDE OIL ISCLASSIFIED ON THE BASIS OF LOCATION ONLYAS OILS FROM DIFFERENT LOCATIONS HAVEDIFFERENT CHARACTERISTICS & THEY ARE ALSONAMED AFTER THE PLACES OF ORIGIN.

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NORTH SEA CRUDES

API GRAVITY- AROUND 38.5 DEGREES

SULPHUR LEVEL- 0.36%

EXAMPLES: BRENT, FORTIES, OSBERG,NORTH SEA BASKET, EKOFISH, STATFJORD& FLOTTA.

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WEST AFRICAN CRUDES

API GRAVITY- AROUND 35 DEGREES

SULPHUR LEVEL- 0.2%

EXAMPLES:BONNY LIGHT, QUA LBOE,BRASS RIVER, ESCRAVOS, FORCADOS &CABINDA.

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PERSIAN GULF CRUDES

API GRAVITY-AROUND 37 DEGREES

SULPHUR LEVEL-1.08%

EXAMPLES- DUBAI & OMAN ASSESSMENTS,MURBAN, LOWER ZAKUM, QATAR LAND,QATAR MARINE & BANOCO ARAB MEDIUM.

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UNITED STATES CRUDES

API GRAVITY-VARIABLE, AROUND 39.6DEGREES

SULPHUR LEVEL-VARIABLE, AROUND0.24%

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CRUDE OILFORMATION

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CRUDE OIL IS CREATED THROUGH THE HEATING &COMPRESSION OF ORGANIC MATERIALS OVER A LONG PERIOD OF TIME. OIL IS FORMED FROM THE REMAINS OF TINY PLANTS & ANIMALS {PLANKTONS} THAT DIEDIN ANCIENT SEAS BETWEEN 10 MILLION & 600 MILLIONYEARS AGO. AFTER THE ORGANISMS DIED, THEY SANK INTO THE SAND & MUD AT THE BOTTOM OF THE SEA.OVERTHE YEARS, THE ORGANISMS DECAYED IN THE SEDIMENTARY LAYERS. IN THESE LAYERS, THERE WASLITTLE OR NO OXYGEN PRESENT.OVER TIME THIS ORGANIC MATERIAL COMBINED WITH MUD AND WAS THEN HEATED TO HIGH TEMPERATURES FROM THEPRESSURE CREATED BY HEAVY LAYERS OF SEDIMENT. THIS PROCESS, KNOWN AS DIAGENESIS, CHANGES THE CHEMICAL COMPOSITION FIRST INTO A WAXY

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COMPOUND CALLED KEROGEN AND THEN, WITH INCREASED HEAT, INTO A LIQUID THROUGH A PROCESS CALLED CATAGENESIS. SO MICRO-ORGANISMS BROKE THE REMAINS INTO CARBON-RICH COMPOUNDS THAT FORMED ORGANIC LAYERS.THE ORGANIC MATERIAL MIXED WITH THESEDIMENTS, FORMING FINE-GRAINED SHALE, OR SOURCE ROCK.AS NEW SEDIMENTARY LAYERS WEREDEPOSITED, THEY EXERTED INTENSE PRESSURE &HEAT ON THE SOURCE ROCK. THE HEAT & PRESSUREDISTILLED THE ORGANIC MATERIAL INTO CRUDE OIL.THE OIL FLOWED FROM THE SOURCE & ACCUMULATEDIN THICKER, MORE POROUS LIMESTONE OR SANDSTONE, CALLED RESERVOIR ROCK.

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MOVEMENTS IN THE EARTH TRAPPED THE OILIN THE RESERVOIR ROCKS BETWEEN LAYERSOF IMPERMEABLE ROCK, OR CAP ROCK, SUCHAS GRANITE OR MARBLE.

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Exploration: Reservoir Rocks

Earth Science World Image Bank Image #h5innl

• The permeable strata in an oil trap is known as the Reservoir Rock

• Reservoir rocks have lots of interconnected holes called pores. These absorb the oil like a sponge

This is a highly magnified picture of a sandy reservoir rock (water-filled pores are shown in blue)

As oil migrates it fills up the pores(oil-filled pores shown in black)

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ANTICLINE

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HISTORY OF CRUDE OIL

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The history of crude oil dates back to the 3rd or

4th century A.D. when the presence of oil was first discovered in China. The oil that the early Chinese people found to have extremely good medicinal value and was used in the salt form. To extract that oil from under the earth’s crust first oil wells of around 243m were dug up in that region with the help of bamboo poles possessing metal tool at the end. The crude oil was also used for the lighting purpose in Ancient Persia.

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HISTORY OF CRUDE

OIL IN INDIA

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INDIA WAS NOT KNOWN TO THE WORLD IN THE

CONTEXT OF CRUDE OIL & IT’S BY-PRODUCTPRODUCTION. AS LATE AS IN 1889,THE PRESENCEOF OIL IN INDIA WAS DISCOVERED IN DIGBOI INASSAM. 1ST CRUDE OIL REFINERY IN INDIA WAS SETUP IN DIGBOI IN 1901. THEN THE EXPLORATION &PRODUCTION ACTIVITIES WERE LIMITED TO THE NORTH EASTERN PART OF THE COUNTRY. IN 1958 &1974, 2 MORE PLACES FOR CRUDE OIL PRODUCTIONWERE IDENTIFIED NAMELY:CAMBAY ONSHORE BASIN & BOMBAY OFFSHOREBASIN. INITIALLY THE MAJOR INTERNATIONALCOMPANIES WERE GIVEN THE JOB TO EXPLORE

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& PRODUCE OIL IN THE COUNTRY BUT AFTER THESHOCK IN OIL PRICES IN 1973, WHOLE OF THESECTOR WAS NATIONALIZED. THE MAJOR OILRESERVES OF THE COUNTRY ARE SITUATED AT:MUMBAI HIGH {MUMBAI},UPPER ASSAM {ASSAM},CAMBAY {GUJARAT},KRISHNA-GODAVARI BASIN {ANDHRA PRADESH},KAVERY BASIN {TAMIL NADU},NAGALAND &ARUNACHAL PRADESH.

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CRUDE OILEXPLORATION

METHODS

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Exploration: Oil Traps

• SOME ROCKS ARE PERMEABLE AND ALLOW OIL TO FREELY PASS THROUGH THEM

• OTHER ROCKS ARE IMPERMEABLE AND BLOCK THE UPWARD PASSAGE OF OIL

• WHERE OIL RISES UP INTO A DOME (OR ANTICLINE) CAPPED BY IMPERMEABLE ROCKS IT CAN’T ESCAPE. THIS IS ONE TYPE OF AN OIL TRAP.

Impermeable

PermeableDome Trap

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Types of Oil Traps (A)A simple fold trap (B) fossilized coral reef

(B)(C) fault trap (D) salt dome

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GRAVITY SURVEYTHEY ARE PERFORMED TO EXAMINE BEDROCK TOPOGRAPHY UNDER THE EARTH’S SURFACE. IT IS USED TO LOCATE LARGE METALLIC MINERAL DEPOSITS &ALSO CONTACTS BETWEEN GEOLOGIC UNITS OF DIFFERING MASSES & DENSITY. IT IS A FAIRLY COMPLICATED SYSTEM BUT IT IS BASED ON THE PREMISETHAT A TARGET, OIL RESERVE IN THIS CASE, HAS ADIFFERENT DENSITY FROM THE SURROUNDING GEOLOGY.COMPUTER MODELS ARE ONCE AGAIN GENERATED TO DEPICT THE GENERAL AREA WHERE SUCH GRAVITYCHANGES OCCUR.

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SEISMIC SURVEYTHIS TYPE OF SURVEY IS CONDUCTED UTILIZING A SPECIAL TRUCK, CALLED A SEISMIC SOURCE TRUCK,WHICH CREATES SEISMIC WAVES BY ESSENTIALLYVIBRATING. THE WAVES THEN TRAVEL THROUGH THEEARTH’S CRUST & THE WAVE RETURNS ARE MEASUREDBY SOPHISTICATED COMPUTERS TRAVELLING INFRONTOF THE SEISMIC TRUCK. THESE TESTS CAN ALSO BE PERFORMED BY USING DYNAMITE INSTEAD OF A SEISMICTRUCK.THE COMPUTER WILL CALCULATE THE TIMING OF THE RETURNS & WILL THEN BE ABLE TO DRAW GRAPHSCALLED, SEISMOGRAPHS, OF THE TOPOGRAPHY &

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LAYERS OF THE CRUST. BY EXAMINING CHARTS ATRAINED GEOLOGIST WOULD BE ABLE TO IDENTIFY THETRAPS. BY IDENTIFYING THE TRAPS ONE WOULD BELIKELY TO IDENTIFY AN OIL RESERVOIR. MANY SEISMO-GRAPHS CAN BE MANIPULATED BY THE COMPUTER TOPRODUCE 3-D IMAGES OF THE ROCK FORMATIONS.EXTENSIVE MODELING CAN ALSO BE BUILT ALL BYCOMPUTER, BASED ON THE DATA THAT IS RETURNEDFROM THE SEISMIC WAVES.

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REMOTE SENSING Remote Sensing (RS) is the use of aerial photographs to

locate and map surface features. Increasing use of satellite imagery is being made because it shows large areas on the surface of the earth. Even though the photographs are taken from several hundred miles up in space, they are able to show features only a few feet in size. Once an area is selected and the satellite imagery obtained, the exploration geologist utilizes mapping techniques to produce a geologic map (a map that indicates geological structures by using conventional symbols) for the area. The series of lines and arrows indicate the type of structure that exists at the surface. Another type of RS technique uses imagery that was created from a radar looking at the ground called Side Looking Airborne Radar (SLAR).

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The last step in oil exploration is done when petroleum engineers have a test well drilled. This step is important, because even with all the oil exploration methods available it is impossible to determine conclusively that oil is present until a test well is drilled and oil or is actually recovered and verified. Once a geologist clears the project for drilling, a test well is drilled to see if oil is indeed reached in the reservoir. The test drill will be the final preliminary phase prior to permanent drilling of an oil field.

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小田 @ www.iloveppt.org

THANK YOU

BY: PRADNYA NASNODKAR & VINITA NAGVEKAR