Post on 21-Apr-2015
TEKNOLOGIPEMROSESAN HIDROKARBON
K03CARA TERDAPATNYA HIDROKARBONCARA TERDAPATNYA HIDROKARBON
Akumulasi hc, reservoir, migrasi, batuan reservoir lapisan penutup perangkapreservoir, lapisan penutup, perangkap
D W h diDr. WahyudiDept. Ocean Engineering, ITS
SurabayaSurabaya
1. CARA TERDAPATNYA HIDROCARBON
• Di permukaan bumi:– Sebagai rembasan (seeps or seepages) seperti danau atau sumber atau Sebagai rembasan (seeps or seepages), seperti danau atau sumber atau
seperti pasir yang dijenuhi oleh HC• Lapisan yang mengandung HC terpotong karena erosi• Berasosiasi dg patahanBerasosiasi dg patahan• Berasosiasi dengan mudvolcano
• Di dalam kerak bumi (earthcrust):– Sebagai suatu akumulasi: penjenuhan batuan oleh HC (merupakan
satu2nya cara terdapatnya HC yg mempunyai arti ekonomi)– Dalam jumlah kecil disebut sebagai tanda2 minyak (oil shows) penting g g
dalam eksplorasi– Dalam jumlah akumulasi komersiil: dalam jumlah cukup besar untuk
diproduksi secara umum• Tergantung kualitas dan kuantitas reservoir• Faktor ekonomi dan politik• Harga minyak dunia
1. CARA TERDAPATNYA HIDROCARBONdi permukaan
Lapisan Tanah (permeable)
Lapisan Penutup
Rembasan
Lapisan Penutup
Lapisan Reservoir LapisanBatugaram
Lapisan
Basement
Rembasan
LapisanReservoir
RembasanRembasan
Lapisan
Lapisan Penutup LapisanReservoir
LapisanReservoir
Akumulasi komersiil
• Jika lapisan mengandung HC dapat diproduksi secara menguntungkan, yaitu jika jumlah yang dihasilkan dapat di d k d d t d t t bi diperdagangkan dengan pendapatan yang dapat menutup biaya eksplorasi dan produksi serta memberi laba.
• Faktor yang mempengaruhi:Faktor yang mempengaruhi:– Harga minyak di pasaran bebas– Jumlah cadangan yang terdapat dalam akumulasi.– Produktivitas reservoir.– Biaya eksplorasi, eks[loitasi, produksi.– Pajak dan biaya lain.
2. Reservoir, oil field & oil province• Oil poolOil pool
– HC yang menjenuhi reservoir dan berada dalam sistem tekanan yang sama
• Oil FieldOil Field– Area yang di bawahnya terdapat akumulasi HC dalam beberapa oil pool
dan terdapat dalam gejala geologi yang sama. Gejala geologi yang sama bisa dalam hal struktur geologi atau stratigrafinya.g g g y
• Giant oil field: lapangan minyak yang mempunyai cadangan > 500 juta barel. E.g.: Ghawar oil field (Arab Saudi), Minas (Sumatera Tengah), Kirkuk (Irak)
• Oil Province– Sering juga disebut oil basin (cekungan minyak), biasanya merupakan
cekungan sedimen. Tetapi tidak selalu cekungan sedimen mengandung HC.Oil i (d h i k) d l h di j l h il l d – Oil province (daerah minyak) adalah area di mana sejumlah oil pool dan oil fieldberkelompok dalam lingkungan geologi yang sama.
2. Reservoir• Reservoir HCReservoir HC
– Akumulasi HC selalu terdapat di reservoir. Reservoir adalah wadah/container tempat HC berkumpul. Cara terakumulasinya harus memenuhi beberapa syarat yang merupakan unsur pentingreservoir HC, yitu:
• Batuan reservoir• Lapisan penutup
P k HC• Perangkanp HC
• Batuan reservoir (reservoir rock)– Lapisan batuan sebagai tempat yang dijenuhi HC. Batuan reservoir harus
d b lporous dan permeabel.
• Lapisan penutup (cap rock)– Lapisan yang tidak permeabel yang terdapat di atas suatu reservoir
menghalangiminyak & gas keluar dari reservoir.
• Perangkap reservoir (oil trap)– Unsur pembentuk reservoir yang bentuknya sedemikian rupa sehingga p y g y p gg
lapisan dan penutupnya merupakan bentuk konkav ke bawah dan menyebabkan HC berada di bagian atas reservoir.
Reservoir Rocks
• Any rock formation, in suitable stratigraphic position,• possessing both porosity and permeability necessary
both to contain and to yield oil, or gas, or both, in i l titicommercial quantities.
• Any rock capable of performing these function is a reservoir rockreservoir rock.
• Lapisan batuan sebagai tempat yang dijenuhi HC. Batuan reservoir harus porous dan permeabel.p p– Sandstone reservoir, carbonates reservoir, fractured rocks
reservoir
MigrationFormation of the OilfieldFormation of the Oilfield
• Obviously the world’s oil is not all • Obviously, the world s oil is not all generated from source rock shales
• Oil (& gas) migrates from the source, through carrier beds and accumulates in gthe reservoir
• Source bed → 1st carrier = primary • Source bed → 1 carrier = primary migration
• Carrier → reservoir = secondary migration
Primary MigrationPrimary Migration
• HypothesesHypotheses
– 1. Migration of hc’s in clay compaction water
– 2 Migration by molecular solution in water2. Migration by molecular solution in water
– Migration in micellar solution
Migration in gas charged solution– Migration in gas charged solution
– Migration via micro-fracturing of source rocksrocks
– Diffusion along kerogen network
• Arguable that all of these process are in • Arguable that all of these process are in operation
Secondary MigrationSecondary Migration
Oil t b bl f ti h • Oil must be capable of continuous phase flow
• Capillarity – NB the oils capillary pressure must exceed the reservoirs
displacement pressure (reservoirs normally fluid filled)
Once in the Reservoir Rock
• Availability of continuous pore spaces allows y p pcontinuous flow
• Physical requirements for secondary migration Physical requirements for secondary migration are:
1 Adeq ate s ppl of h drocarbons– 1. Adequate supply of hydrocarbons– 2. Adequate continuous migration pathways– 3. Adequate pressure gradient to drive
migration
Main Mechanisms of Secondary Mi tiMigration
Mi i b d i• Migration by water drive
• Migration by gas flushing
• Fracture-bound migration
BuoyancyBuoyancy
• Difference in densities between H2O andDifference in densities between H2O and oil = main mechanism of secondary migrationmigration
• All crude oils float on saline water, nearly all on freshwaterall on freshwater
• Thus, oil tends to migrate upwards through th h i tthe heavier water
• Subject to a buoyant force (Pb)
Buoyant ForceBuoyant Force
• Oil displaces equal volume of waterOil displaces equal volume of water• Pb = difference between weight of
displaced water and emplaced oil: vectordisplaced water and emplaced oil: vector force directed vertically upwardsP diff i b t t• Pb = difference in pressure between water phase and oil phase
• Pb = Pw - Po
Gas Flushing
• 2 fluids of different densities try to occupy the same trap
• Heaviest fluid is displaced as lighter one moves above itmoves above it
Trapping MechanismsTrapping Mechanisms
Fundamental Types of Trap• Convex trap reservoirs• Permeability trap reservoirs• Pinc-hout (end of stratum) trap reservoirs• Fault trap reservoirs• Piercement (diapir) trap reservoirs
Types of Petroleum TrapsTypes of Petroleum Traps (A) A simple fold trap (B) fossilized coral reef (C) fault trap (D) salt dome( )
Convex Trap ReservoirsConvex Trap Reservoirs
• Formed by folding or differentialFormed by folding or differential thicknesses of strata and due to convexity alone:alone:– Porosity extends in all directions beyond the
reservoirreservoir– Reservoir is surrounded by water (edge
water)water)
Permeability Trap ReservoirsPermeability Trap Reservoirs
• Form due to changes in reservoir powerForm due to changes in reservoir power• Reservoir partly defined by edge water
and partly by a permeability barrierand partly by a permeability barrier
Pinchout Trap ReservoirsPinchout Trap Reservoirs
• Formed by lenticular structures (e g reefs)Formed by lenticular structures (e.g. reefs)• Periphery defined by edge water and the
pinchout of the reservoir bedpinchout of the reservoir bed
Fault Trap ReservoirsFault Trap Reservoirs
• Periphery is defined partly by edge waterPeriphery is defined partly by edge water and partly by a fault boundary
Piercement Trap ReservoirsPiercement Trap Reservoirs
• Formed by diapirs or volcanic necksFormed by diapirs or volcanic necks• Reservoir defined by edge water and a
piercement contactpiercement contact
By Far the Commonest Method of Describing Traps Is Based on Origin
• Structural Traps: formed by faulting of folding as the result of structural activityas the result of structural activity
• Non-structural traps: stratigraphic pinch outs, permeability traps…p y p