11

Chapter 2 Chapter 2

Petroleum Geology and Petroleum Geology and ReservoirsReservoirs

(( 石油地質及儲油層石油地質及儲油層 ))20082008

ReferencesReferences石油地質及儲油層 石油地質及儲油層 (Petroleum Geology and (Petroleum Geology and

Reservoir)Reservoir)Textbook 1 Fundamentals of Petroleum, Petroleum Extension

Service, The University of Texas at Austin, Austin, Texas,1979.

– – chapter 1chapter 1

Textbook 2 Archer, J. S., and Wall, C.G., Petroleum Engineering

—principles and practice, Graham & Trotman, MD, 1986.

– – chapter 2chapter 2

TextBook 3 Donohue, D.A.T., and Lang K.R., A First Course in

Petroleum Technology, International Human Resources Development Corporation, Houston,1986

– – chapter 4.1; 4.2chapter 4.1; 4.222

33

Petroleum Geology Petroleum Geology

(( 石油地質石油地質 ))

Geology (Geology ( 地質地質 ))

------ 研究研究 (1)(1) 地球的歷史及構造地球的歷史及構造 (2)(2) 記錄在岩石的生物記錄在岩石的生物 (( 命命 )) 形式形式

Petroleum Geology(Petroleum Geology( 石油地質石油地質 ))

------ 研究地質以預測石油累積之處所研究地質以預測石油累積之處所

44

地球的形成及構造地球的形成及構造 地球的形成 地球的形成 —— 4040 ～～ 5050 億年前由宇宙塵億年前由宇宙塵

(Cosmic dust)(Cosmic dust) 的凝結而成的凝結而成

地球內部大構造 地球內部大構造 —— Core--- heavy (4,400 miles)Core--- heavy (4,400 miles) Mantle--- Lighter (1,800 miles)Mantle--- Lighter (1,800 miles) Crust--- 10~30 milesCrust--- 10~30 miles

55

地球內部大構造地球內部大構造

Core-- heavy (4,400 Core-- heavy (4,400 miles)miles)Mantle-- Lighter (1,800 Mantle-- Lighter (1,800 miles)miles)Crust--- 10~30 milesCrust--- 10~30 miles

66

地球表面的變化 地球表面的變化 -- Rock cycle-- Rock cycle

Magma( 岩漿 )

Igneous rocks( 火成岩 )

Sediments( 沉積物 )

Sedimentaryrocks

Metamorphicrocks

地球內部 Water vapor and gases

Primeval( 初期的 )Atmosphere( 大氣 )

地殼冷卻

地殼收縮變形而皺摺

噴出 形成

heat

heatpressure

erosion

erosion

pressurecementation

erosion

下雨

Cool

77

沉積岩的分類沉積岩的分類

ClasticClastic ChemicalChemical OrganicOrganic OtherOther

ConglomerateConglomerateSandsonteSandsonteSiltstoneSiltstoneShaleShale

CarbonateCarbonate EvaporiteEvaporite PeatPeatCoalCoalDiatomiteDiatomiteLimestoneLimestone

ChertChert

LimestoneLimestoneDolomiteDolomite

GypsumGypsumAnhydriteAnhydriteSaltSaltPotashPotash

碎屑岩碎屑岩 化學岩化學岩 有機岩有機岩 其他其他

礫岩礫岩砂岩砂岩粉砂岩粉砂岩頁岩頁岩

碳酸鹽碳酸鹽 蒸發岩蒸發岩 泥炭泥炭煤煤矽藻土矽藻土石灰岩石灰岩

角岩角岩

石灰岩石灰岩白雲石白雲石

石膏石膏硬石膏硬石膏鹽岩鹽岩碳酸鉀碳酸鉀 ((鉀化鉀化合物合物 ))

88

Reservoir Rock (Sedimentary Rock)

Reservoir RockProrsity

Permeability

Sandstones (SiO2)

Carbonates Limestones (CaCO3)

Dolomites (CaCO3, MgCO3)

99

地球的歷史地球的歷史

寒武紀寒武紀 (Cambrian)(Cambrian) 【【約約 5.55.5 億年前億年前】】開始在海開始在海洋裡有大量的生物洋裡有大量的生物 (( 生命生命 ))

在寒武紀之前為前寒武紀在寒武紀之前為前寒武紀 (Precambrian)(Precambrian)

地質年代自寒武紀開始地質年代自寒武紀開始 > > 地質代年表地質代年表 (Geologic Time Scale)(Geologic Time Scale)

泥盆紀泥盆紀 (Devonian)(Devonian) 時期時期【【約約 3.33.3 億年前億年前】】陸上陸上有大量植物及動物有大量植物及動物

1010

Geological Time ScaleGeological Time Scale

1111

地層年代表地層年代表

1212

1313

Petroleum accumulationPetroleum accumulation(( 石油累積石油累積 ))

Petroleum reservoirPetroleum reservoir(( 石油油藏石油油藏 ;; 油藏油藏 ;; 油層油層 ))

Petroleum accumulationPetroleum accumulation 必須具備必須具備

(1)Oil (1)Oil ＆ ＆ gas gas 之來源之來源 (2)(2) 具有孔隙具有孔隙 (porosity)(porosity) 及滲透率及滲透率

(permeability)(permeability) 之之 Reservoir RockReservoir Rock

(3) (3) 要有要有 trap(trap( 封閉封閉 )) 以阻擋流體的流動以阻擋流體的流動

1414

石油的來源石油的來源

1515

石油的來源石油的來源

－石油來自沈積岩的有機物質－石油來自沈積岩的有機物質 －海洋裡大量的生物不停的，緩慢的掉落到海底。－海洋裡大量的生物不停的，緩慢的掉落到海底。 雖然在掉落的過程中，有部分被吃掉或被氧化掉，雖然在掉落的過程中，有部分被吃掉或被氧化掉， 但另部份但另部份 (( 動物或植物動物或植物 )) 掉落海底而埋在沼澤或泥濘之掉落海底而埋在沼澤或泥濘之 海底海底 －海底繼續被－海底繼續被 Sand(Sand( 砂砂 )) ，， Clay(Clay( 黏土黏土 )) 及及 debrisdebris 等沈積等沈積

物埋沒物埋沒 一直到幾千英呎一直到幾千英呎 －沈積物的壓力開始作用。－沈積物的壓力開始作用。 細菌由殘餘的有機物質中，用掉氧而分解物質，細菌由殘餘的有機物質中，用掉氧而分解物質， 使其僅存碳及氫使其僅存碳及氫 －在高度的壓力及重量的地層影響之下，－在高度的壓力及重量的地層影響之下， ClaysClays 變成變成 Shales → Shales → 石油產生石油產生

1616

Petroleum formation requires Petroleum formation requires that organic source clays that organic source clays become mature by subjection to become mature by subjection to pressure and temperature.pressure and temperature.

1717

石油形成的重要條件石油形成的重要條件

225℉ < temperature < 350℉ 225℉ < temperature < 350℉ 有利條件有利條件

temperature < 150℉ temperature < 150℉ 不可能形成石油不可能形成石油

temperature > 500℉ temperature > 500℉ 有機物質碳化，有機物質碳化， 不能形成石油不能形成石油

1818

Generation of gas and oilGeneration of gas and oil

1919

2020

In In geologygeology and and oceanographyoceanography, , diagenesisdiagenesis is any chemical, is any chemical, physical, or biological change physical, or biological change undergone by a undergone by a sedimentsediment after its after its initial deposition and during and after initial deposition and during and after its its lithificationlithification, exclusive of surface , exclusive of surface alteration (weathering) and alteration (weathering) and metamorphismmetamorphism. .

2121

CatagenesisCatagenesis can refer to: can refer to: Catagenesis (geology)Catagenesis (geology) –– The The crackingcracking

process in which organic process in which organic kerogenskerogens are broken down into are broken down into hydrocarbonshydrocarbons; ;

Catagenesis (biology)Catagenesis (biology) –– Retrogressive evolution, as Retrogressive evolution, as contrasted with contrasted with anagenesisanagenesis. .

2222

MetamorphismMetamorphism can be defined as can be defined as the solid state recrystallisation of the solid state recrystallisation of pre-existing pre-existing rocksrocks due to changes in due to changes in heat and/or pressure and/or heat and/or pressure and/or introduction of fluids i.e without introduction of fluids i.e without melting. There will be melting. There will be mineralogicalmineralogical, , chemical and chemical and crystallographiccrystallographic changes changes

2323

Prolonged exposure to high temperatures, or Prolonged exposure to high temperatures, or shorter exposure to very high temperatures, may shorter exposure to very high temperatures, may lead progressively to the generation of lead progressively to the generation of hydrocarbon mixtures characterized as hydrocarbon mixtures characterized as condensates, wet gases and gas.condensates, wet gases and gas.

The average organic content of potential source The average organic content of potential source rocks is about 1% by weight.rocks is about 1% by weight.

The Kimmeridge clay, the principal source rock for The Kimmeridge clay, the principal source rock for North Sea oil average about 5% carbon (~7% North Sea oil average about 5% carbon (~7% organic matter) with local rich streaks greater organic matter) with local rich streaks greater than 40%.than 40%.

The hydrogen content of the organic matter The hydrogen content of the organic matter should be greater than 7% by weight for potential should be greater than 7% by weight for potential as an oil source.as an oil source.

2424

It is a rule of thumb that for each It is a rule of thumb that for each percentage point of organic carbon in percentage point of organic carbon in mature source rocks, some mature source rocks, some 1300~1500 cubic meters of oil per 1300~1500 cubic meters of oil per kmkm22-m (or 10~40 barrels of oil per -m (or 10~40 barrels of oil per acre-ft; or 56-225 ftacre-ft; or 56-225 ft3/ 43560 ft/ 43560 ft3) of ) of sediment could be generated.sediment could be generated.

(12~52 : 10,000) (1:833 ~ 1:200)(12~52 : 10,000) (1:833 ~ 1:200)

It is not, however, necessarily true It is not, however, necessarily true that all the oil generated will be that all the oil generated will be expelled or trapped in porous rock.expelled or trapped in porous rock.

2525

石油移棲石油移棲

石油形成( in source rock)

Traps ＆ Reservoir RocksMigration

經過 porous bed 有 permeability

由於 Compaction of Source bed and ……….

The migration process involves two main stages, The migration process involves two main stages, namely from the source rock and then through a namely from the source rock and then through a permeable system.permeable system.

2626

Migration of petroleum Migration of petroleum -- -- from the source rockfrom the source rock

2727

Migration of petroleum Migration of petroleum

-- -- from the source rockfrom the source rock ** Capillary effect** Capillary effect

** Microfractures ** Microfractures Since the generation of petroleum is Since the generation of petroleum is

accompanied by volume changes which can lead accompanied by volume changes which can lead to high local pressures, there may well be an to high local pressures, there may well be an initiation of microfractures which provide an initiation of microfractures which provide an escape route into permeable systems such as escape route into permeable systems such as sedimentary rocks or fault planes.sedimentary rocks or fault planes.

The source rock microfractures are believed to The source rock microfractures are believed to heal as pressures are dissipated.heal as pressures are dissipated.

2828

Migration of petroleum Migration of petroleum ----through a permeable systemthrough a permeable system

** Fluid potential gradient or gravity effect** Fluid potential gradient or gravity effect

In the permeable system the transport In the permeable system the transport occurs under conditions of a fluid potential occurs under conditions of a fluid potential gradient which may take the hydrocarbon gradient which may take the hydrocarbon to surface or to some place where it to surface or to some place where it becomes trapped.becomes trapped.

It might be assumed that less than 10% of It might be assumed that less than 10% of petroleum generated in source rocks is petroleum generated in source rocks is both expelled and trapped, as shown in both expelled and trapped, as shown in the example of Fig. 2.5. the example of Fig. 2.5.

2929

3030

Petroleum traps(Petroleum traps( 石油封閉石油封閉 ))

The characteristic forms of petroleum The characteristic forms of petroleum trap are known as trap are known as

structural traps(structural traps( 構造封閉構造封閉 ) and ) and

stratigraphic traps(stratigraphic traps( 地層封閉地層封閉 ),),

with the great majority of known with the great majority of known accumulation being in the former accumulation being in the former style.style.

3131

地質構造（地質構造（ Geological StructuresGeological Structures ））

Erosion － SedimentationUplift － wearing down

Upper crust movement

Upward

downward

Fault

Normal

Reverse

Thrust

Lateral

Strata or bed Unconformity－ disconformity－ Angular unconformity

FoldsArches (or upfold) → anticlines

Traughs (or downfold) → synclines

Important to petroleum accumulation

3232

Figure 1.12. Two general kinds of unconformities are disconformity (A) and angular unconformities (B) and (C).

造山運動之應力所造成

沉積過程所造成

Figure 1.13. Basic hydrocarbon reservoirs are structural and / or stratigraphic traps.

3333

封閉 (traps)

封閉 (traps)Structural traps － an arched upper surfaceStratigraphic traps---up-dip termination of porosity (permeability)

Structural traps

Anticline trapFault trapDome and plug trap

Stratigraphic traps

Unconformity trapsLenticular trap

Disconformity

Angular unconformity

Combination traps

3434

Cap rock and fluid Cap rock and fluid distributiondistribution

Impermeable rocks provide seal above Impermeable rocks provide seal above and below the permeable reservoir rocks.and below the permeable reservoir rocks.

At equilibrium conditions, the density At equilibrium conditions, the density differences between the oil, gas and differences between the oil, gas and water phases can result in boundary water phases can result in boundary regions between them known as fluid regions between them known as fluid contacts, i.e. gas-oil and oil-water contacts, i.e. gas-oil and oil-water contacts.contacts.

3535

Structural trap ( 構造封閉構造封閉 )) -- AnticlineAnticline

Longitudinal view of a typical anticline. The oil cannot escape upward because of the impervious shale bed above the oil sand; neither can it travel downward because of the water that is associated with an accumulation of this type.

Anticlines －Of the many types of structural features present in the upper layers of the earths crust that can trap oil, the most important is the anticlines － the type of structure from which the greater part of the word’s oil has been produced. Anticlines are upfolds of beds in the earth’s crust, and, when the proper conditions are present, oil accumulates within the closure of there folds.

3636

Structural trap-- Anticline Anticline

Lateral, or end view, of a typical anticline.

Plan view of a typical anticline, showing locations of longitudinal view A-B and lateral view C-D.

3737

Structural trapsFigure 1.7. Schematic cross section shows deformation of earth’s crust by bucking of layers into folds

Figure 1.8. Simple kinds of folds are symmetrical anticline (A), plunging asymmetrical anticline (B), plunging syncline (C), and dome with deep salt core (D).

Figure 1.9. Simplified diagram of the Milano, Texas, fault.

3838

Structural traps– dome & anticline

Figure 1.15. Oil accumulates in a dome-shaped structure (A) and an anticlinal type of fold structure (B). An anticline is generally long and narrow while the dome is circular in outline. (Courtesy of American Petroleum Institute)

3939

4040

Structural traps -- faultsFigure 1.10. Simple kinds of faults are normal (A), reverse (B), thrust (C), and lateral (D).

Figure 1.11. Variations of normal and reverse faulting are rotational faults (A) and upthrust faults (B).

4141

Structural traps

Figure 1.14. Common types of structural traps

4242

Structural trap – fault & anticline

Figure 1.17. Shown in map view, fault traps may be simple (A) or compound (B).

Figure 1.16. Gas and oil are trapped in a fault trap-a reservoir resulting from normal faulting or offsetting of strata. The block on the right has moved up from the block on the left, moving impervious shawl opposite the hydrocarbon-bearing formation. (Courtesy of American Petroleum Institute)

4343

Stratigraphic trapsStratigraphic traps(( 地層封閉地層封閉 ))

4444

Figure 1.12. Two general kinds of unconformities are disconformity (A) and angular unconformities (B) and (C).

造山運動之應力所造成

沉積過程所造成

Figure 1.13. Basic hydrocarbon reservoirs are structural and / or stratigraphic traps.

4545

Stratigraphic trapsStratigraphic traps

Unconformity － Disconformity － Angnlar unconformity Pinctout

Sand lenses

Changes in sedimentation

4646

Figure 1.22. Oil is trapped under an unconformity. (Courtesy of API)

Figure 1.23. Lenticular traps confine oil in porous parts of the rock. (Courtesy of API)

4747

Stratigraphic trapStratigraphic trap

An example of a stratigraphic trap where the oil zone pinches out.

A stratigraphic trap where sand lenses are interspersed in a shale bed. The shale acts as a permeability barrier

4848

Stratigraphic TrapsStratigraphic Traps

A stratigraphic trap where changes in sedimentation act as a permeability barrier.

An angular unconformity as an oil trap. The flat-lying shale bed above the oil zones acts as a permeability barrier.

4949

Stratigraphic trapsStratigraphic traps

Stratigraphic Stratigraphic traps result traps result when a when a depositional depositional bed changes bed changes from permeable from permeable rock into fine-rock into fine-grain grain impermeable impermeable rock (Fig. 2.8).rock (Fig. 2.8).

5050

5151

Combination trapsCombination traps

Many reservoirs exist as the result of Many reservoirs exist as the result of a combination of structural and a combination of structural and stratigraphic features.stratigraphic features.

In the Viking Graben area of the In the Viking Graben area of the northern North Sea, the Brent Sand northern North Sea, the Brent Sand reservoirs are characteristically reservoirs are characteristically faulted deltaic sands truncated by faulted deltaic sands truncated by the Cretaceous unconformity.the Cretaceous unconformity.

5252

5353

ReservoirsReservoirs

Reservoir(Reservoir( 儲油層儲油層 ))

We may define a reservoir as an accumulation of We may define a reservoir as an accumulation of hydrocarbon in porous permeable sedimentary rock.hydrocarbon in porous permeable sedimentary rock.

The accumulation, which will have reached a fluid The accumulation, which will have reached a fluid pressure equilibrium throughout its pore volume at pressure equilibrium throughout its pore volume at the time of discovery, is also sometimes known as a the time of discovery, is also sometimes known as a pool.pool.

A hydrocarbon field may comprise several A hydrocarbon field may comprise several reservoirs at different stratigraphic horizons or in reservoirs at different stratigraphic horizons or in different pressure regimes. different pressure regimes.

5454

5555

FieldField

An area consisting of a single reservoir or multiple reservoirs all grouped on, or related to, the same individual geological structural feature and/or stratigraphic condition. There may be two or more reservoirs in a field that are separated vertically by intervening impermeable rock, laterally by local geologic barriers, or both. The term may be defined differently by individual regulatory authorities.

5656

Reservoir(Reservoir( 儲油層儲油層 ))

A subsurface rock formation containing an A subsurface rock formation containing an individual and separate natural individual and separate natural accumulation of moveable petroleum that accumulation of moveable petroleum that is confined by impermeable is confined by impermeable rocks/formations and is characterized by a rocks/formations and is characterized by a single-pressure system.single-pressure system.

5757

Reservoir(Reservoir( 儲油層儲油層 ))

具有商業價值的石油具有商業價值的石油 (( 及天然氣及天然氣 )) 地層地層 ----reservoirreservoir ，所需具備之條件，所需具備之條件

(1)(1) 合適之地層形貌 合適之地層形貌 (Shape/Configuration- (Shape/Configuration- traps)traps)

(2)(2) 頂蓋層 頂蓋層 (cap rock, rock seal)(cap rock, rock seal) (3)(3) 儲油層之面積儲油層之面積 (area)(area) 大大 (4)(4) 儲油層之厚度儲油層之厚度 (thickness)(thickness) 大大 (5)(5) 儲油層之孔隙率儲油層之孔隙率 (porosity)(porosity) 大大 (6)(6) 儲油層之含水飽和度儲油層之含水飽和度 (water saturation)(water saturation) 小小 (7)(7) 儲油層之滲透率儲油層之滲透率 (permeability)(permeability) 大大

5858

原油現地藏量原油現地藏量Original oil in place (OOIP)Original oil in place (OOIP)

OOIP = A * h * OOIP = A * h * * (1-S * (1-Sww)* 1/B)* 1/Boo

wherewhere A=A= 儲油層之面積儲油層之面積 (area)(area) h=h= 儲油層之厚度儲油層之厚度 (thickness)(thickness) == 儲油層之孔隙率儲油層之孔隙率 (porosity)(porosity)

SSww = = 儲油層之含水飽和度儲油層之含水飽和度 (water (water saturation)saturation)

Bo = Bo = 石油地層體積因子石油地層體積因子 (oil formation(oil formation volume factor)volume factor)

5959

原油現地藏量原油現地藏量Original oil in place (OOIP)Original oil in place (OOIP)

OOIP = 7758* A * h * OOIP = 7758* A * h * * (1-S * (1-Sww)* 1/B)* 1/Boo

wherewhere OOIP = OOIP = 原油現地藏量原油現地藏量 , STB, STB

A=A= 儲油層之面積儲油層之面積 (area), acres(area), acres h=h= 儲油層之厚度儲油層之厚度 (thickness), ft(thickness), ft == 儲油層之孔隙率儲油層之孔隙率 (porosity), fraction(porosity), fraction SSww = = 儲油層之含水飽和度儲油層之含水飽和度 (water saturation), fraction(water saturation), fraction BBoo = = 石油地層體積因子石油地層體積因子 (oil formation volume factor) (oil formation volume factor) , bbl/STB, bbl/STB

1 acres = 43560 1 acres = 43560 ftft22

1 bbl = 5.61458 ft1 bbl = 5.61458 ft33

6060

資源量及蘊藏量定義資源量及蘊藏量定義

資源量資源量 (Petroleum Resources(Petroleum Resources ， 或 ， 或 ResourcesResources ， 或 ， 或 Total Total

Petroleum in place Petroleum in place ， 或 ， 或 Original oil in place Original oil in place ))

在一區域或礦區所存在的石油（含天然氣）之總在一區域或礦區所存在的石油（含天然氣）之總量，稱為資源量。量，稱為資源量。

蘊藏量蘊藏量 (Petroleum Reserves(Petroleum Reserves ，或 ，或 Reserves )Reserves )

在一已知區域或礦區中，自某一時間點開始，依在一已知區域或礦區中，自某一時間點開始，依據當時的經濟條件據當時的經濟條件 (E)(E) 、工程技術、工程技術 (F)(F) 、及地、及地質條件質條件 (G)(G) 下，在可預見的未來所能採收的石油下，在可預見的未來所能採收的石油（含天然氣）之量稱為蘊藏量，或最終採收量。（含天然氣）之量稱為蘊藏量，或最終採收量。

ResourcesResourcesThe term “resources” as used herein is intended The term “resources” as used herein is intended to encompass all quantities of petroleum to encompass all quantities of petroleum (recoverable and unrecoverable) naturally (recoverable and unrecoverable) naturally occurring on or within the Earth’s crust, occurring on or within the Earth’s crust, discovered and undiscovered, plus those discovered and undiscovered, plus those quantities already produced. quantities already produced.

Further, it includes all types of petroleum whether Further, it includes all types of petroleum whether currently considered “conventional” or currently considered “conventional” or “unconventional” (see Total Petroleum Initially-in-“unconventional” (see Total Petroleum Initially-in-Place). (In basin potential studies, it may be Place). (In basin potential studies, it may be referred to as Total Resource Base or Hydrocarbon referred to as Total Resource Base or Hydrocarbon Endowment.)Endowment.)

6161

Total Petroleum Initially-in-PlaceTotal Petroleum Initially-in-Place

• Petroleum Initially-in-Place is the total Petroleum Initially-in-Place is the total quantity of petroleum that is estimated to quantity of petroleum that is estimated to exist originally in naturally occurring exist originally in naturally occurring reservoirs. reservoirs.

• Crude Oil-in-place, Natural Gas-in-place Crude Oil-in-place, Natural Gas-in-place and Natural Bitumen-in-place are defined and Natural Bitumen-in-place are defined in the same manner (see Resources). (Also in the same manner (see Resources). (Also referred as Total Resource Base or referred as Total Resource Base or Hydrocarbon Endowment.)Hydrocarbon Endowment.)

6262

ReservesReserves

6363

Reserves are those quantities of petroleum anticipated to be commercially recoverable by application of development projects to known accumulations from a given date forward under defined conditions.

Reserves must further satisfy four criteria: They must be discovered, recoverable, commercial, and remaining (as of a given date) based on the development project(s) applied.

6464

6565

6666

Reserves (Reserves ( 蘊藏量蘊藏量 ))

Reserves = OOIP * recovery factorReserves = OOIP * recovery factor

where OOIP = A * h * where OOIP = A * h * * (1-S * (1-Sww) * 1/B) * 1/Boo

recovery factor (recovery factor ( 採收因子採收因子 ) )

= f( k, E, P, T = f( k, E, P, T ……))

k = permeability (k = permeability ( 滲透率滲透率 ))

6767

The setting for hydrocarbon accumulation The setting for hydrocarbon accumulation

is a sedimentary basin that has provided is a sedimentary basin that has provided the essential components for petroleum the essential components for petroleum reservoir occurrence, namelyreservoir occurrence, namely (a) a source for hydrocarbons, (a) a source for hydrocarbons, (b) the formation and migration of petroleum,(b) the formation and migration of petroleum, (c) a trapping mechanism, i.e., the existence of (c) a trapping mechanism, i.e., the existence of

traps in porous sedimentary rock at the time of traps in porous sedimentary rock at the time of migration and in the migration path.migration and in the migration path.

The discovery of oil by exploration well The discovery of oil by exploration well drilling in some of the worlddrilling in some of the world’’s sedimentary s sedimentary basin is shown in Figs. 2.1 and 2.2basin is shown in Figs. 2.1 and 2.2

6868

Exploration Showing a Good Success Rate

23 March 2006 - A strong reflection of New Zealand's prospectivity for oil and gas has been shown by the substantial lift in exploration wells drilled since 2000, and particularly in the past two years. A strong reflection of New Zealand's prospectivity for oil and gas has been shown by the substantial lift in exploration wells drilled since 2000, and particularly in the past two years.

In his keynote presentation to the New Zealand Petroleum Conference, which had a record attendance of more than 520 of which many were from overseas, Associate Energy Minister Harry Duynhoven said a total of 149 wells were drilled in the past six years, of which 74 were wildcats.

In the past 24 months 69 wells were drilled. The Minister said that of the total 74 wildcats there were 12 discoveries, indicating a success rate of about 16%.

Exploration Success Rate

6969

現今的石油鑽井很安全；很多國家都有制定法令以保護地表及地下之自然環境。

在七個探勘井中會有一口具有生產利潤的生產井

對於不具生產價值的井，必須用水泥及泥土將井口封閉起來

7070

7171

Lower right line (0.1 103 m3 oil / km2 ) / (100 willcat wells/104 km2 ) = 104 m3 oil / willcat well = 6.289*104 bbl3 oil / willcat well

Upper left line (10 103 m3 oil / km2 ) / (1 willcat well/104 km2 ) = 108 m3 oil / willcat well = 6.289*108 bbl oil / willcat well

7272

7373

Lower right line (0.01 106 m3 oil discovered / willcat ) / (1 106 m3 oil discovered/ successful wildcat ) = 1% successful wildcat / willcat

Upper left line (0.1 106 m3 oil discovered / willcat ) / (0.1 106 m3 oil discovered/ successful wildcat ) = 100% successful wildcat / willcat

7474

7575

Reservoir fluids and pressureReservoir fluids and pressure

From a petroleum engineering From a petroleum engineering perspective it is convenient to think perspective it is convenient to think of sedimentary basins as of sedimentary basins as accumulations water in areas show accumulations water in areas show subsidence into which sediments subsidence into which sediments have been transported.have been transported.

7777

Reservoir fluids and pressureReservoir fluids and pressure

Reservoir fluidsGasOilwater

Water ─ connate water(connate interstitial water)

Free water~Aquifer

Bottom water

Edge water

Gas Solution gas

Free gas

7878

Fluid pressures in a hydrocarbon Fluid pressures in a hydrocarbon zonezone

7979

Pressure gradient equationPressure gradient equation In a water column representing vertical pore fluid In a water column representing vertical pore fluid

continuity, the pressure at any point (Pcontinuity, the pressure at any point (Pxx) is ) is approximated by the relationshipapproximated by the relationship

PPxx = X = X ．． GGww

or Por Pxx = X = X ．． GGw w + C+ C

where X = the depth below a reference datum where X = the depth below a reference datum (such (such

as sea level)as sea level)

GGww = the pressure exerted by unit height of = the pressure exerted by unit height of water, or pressure gradientwater, or pressure gradient

GGww = f (T, salinity) = f (T, salinity)

GGww = 0.433 psi/ft (or 9.79 kpa/m) for fresh water = 0.433 psi/ft (or 9.79 kpa/m) for fresh water

GGww = 0.44 psi/ft (10 kpa/m) ~ 0.53 psi/ft (12 kpa/m) = 0.44 psi/ft (10 kpa/m) ~ 0.53 psi/ft (12 kpa/m) for reservoir water system for reservoir water system

8080

Hydrocarbon pressure regimesHydrocarbon pressure regimes

In hydrocarbon pressure regimesIn hydrocarbon pressure regimes

psi/ftpsi/ft

psi/ftpsi/ft

psi/ft psi/ft

45.0)( waterdD

dP

35.0)( oildD

dP

08.0)( gasdD

dP

8181

Pressure gradient rangesPressure gradient ranges

In reservoir found at depth between 2000 In reservoir found at depth between 2000 m SS and 4000 m SS, we might use a m SS and 4000 m SS, we might use a gradient of 11 kpa/m to predict pore fluid gradient of 11 kpa/m to predict pore fluid pressures around 220 bars to 440 bars. pressures around 220 bars to 440 bars.

1 bar = 105 pascal (N/m2)1 millbar = 102 pa1psi = 6895 pa14.7 psi = 101,353 pa = 101.3 Kpa = 101.3 hectpa (hpa)

8282

Fluid pressures in a hydrocarbon Fluid pressures in a hydrocarbon zonezone

8383

8484

Reservoir pressure

Reservoir pressureNormal pressure

Abnormal pressure － Artesian effect

8585

Abnormal hydrostatic pressure Abnormal hydrostatic pressure ( No continuity of water to the surface)( No continuity of water to the surface)

[=] psia[=] psia

Normal hydrostatic pressureNormal hydrostatic pressure

c = 0 c = 0

Abnormal (hydrostatic) pressureAbnormal (hydrostatic) pressure c >> 0 → Overpressure (Abnormal high c >> 0 → Overpressure (Abnormal high

pressure)pressure) c << 0 → Underpressure (Abnormal low c << 0 → Underpressure (Abnormal low

pressure)pressure)

CDdD

dPP water 7.14)(

8787

8888

Conditions causing abnormal fluid Conditions causing abnormal fluid pressurespressures

Conditions causing abnormal fluid pressures in Conditions causing abnormal fluid pressures in enclosed water bearing sands includeenclosed water bearing sands include

Temperature change ΔT = +1℉ → ΔP = +125 Temperature change ΔT = +1℉ → ΔP = +125 psi in a sealed fresh water systempsi in a sealed fresh water system

Geological changes Geological changes –– uplifting; surface erosion uplifting; surface erosion Osmosis between waters having different Osmosis between waters having different

salinity, the sealing shale acting as the semi salinity, the sealing shale acting as the semi permeable membrane in this ionic exchange; permeable membrane in this ionic exchange; if the water within the seal is more saline than if the water within the seal is more saline than the surrounding water the osmosis will cause the surrounding water the osmosis will cause the abnormal high pressure and vice versa.the abnormal high pressure and vice versa.

8989

9090

9191

9292