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PRODUCTION OF OIL AND GAS

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After oil and gas found, appraisal drilling need to be done to ... This fracture extend outward from well bore into formation therefore increase permeability ... – PowerPoint PPT presentation

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Title: PRODUCTION OF OIL AND GAS


1
PRODUCTION OF OIL AND GAS
2
Production Phase
  • Once petroleum found well drilled operation
    enters production phase
  • After oil and gas found, appraisal drilling need
    to be done to check for commercial viability
  • Important to test formation to ensure profit and
    determine proper rate of extraction
  • New well begins production, a potential test is
    run determine most oil and gas to be produced
    in a 24 hr period
  • Most efficient recovery (MER) rate based on
    most oil and gas can be extracted for a sustained
    period of time without harming formation
  • Some well under enough pressure do not need
    pumping system. Only install Christmas tree or a
    series of valves and pipes at the surface to
    produce oil and gas

3
  • Most well require some kind of lifting method
    depending on depth of well and whether the well
    has multiple completion
  • Most common method is rod pumping
  • When oil and gas reach surface they are separated
  • Gas is sent to processing plant
  • Sediment and water from oil is removed then oil
    is transported to refinery

4
Glossary of Terms
  • Formation
  • Refers to either a certain layer of the earths
    crust or a certain area of layer.
  • It often refers to the area of rock where a
    petroleum reservoir is located
  • Christmas Tree
  • Series of pipes and valves system for controlling
    the flow of oil from a well
  • Due to high underground pressures, the oil was
    naturally lift by gas or air thus no additional
    pumps needed

5
  • MER (Most Efficient Recovery)
  • MER rate based on most oil and gas that can
    extracted for a sustained period of time without
    harming the formation
  • Generally, most well cannot work 24 hrs, 7 days a
    week could damage formation
  • Multiple Completions
  • Drilling single well at several different depth
    in formation
  • Reason increase production from a single well

6
Field Production
  • Primary Recovery (Natural Methods)
  • 1st method of producing oil from a well
  • Solution gas drive
  • pressure inside reservoir relieved when well
    punctures and gas trapped in oil forms bubbles
  • Bubbles grow, exert pressure push oil to well and
    up to surface (20-30)
  • Gas cap drive
  • If contain gas cap, drill well directly into oil
    layer gas cap expand
  • Expanding gas pushes oil into well (40)
  • Water drive scenario
  • Water layer press against oil layer
  • Water pushes oil towards surface and replace it
    within the pores of the reservoir rock
  • Highest recovery up to 75

7
  • Secondary Recovery
  • Used to enhance or replace primary techniques
  • Water flooding
  • Additional injection well is drilled into the
    reservoir
  • Pressure water injected
  • Water displaces the oil in reservoir
  • Mechanical Lift
  • Reciprocating or plunger pumping called
    horsehead
  • Pump barrel lowered into well on 6 inch string
    steel rod (sucker rods)
  • Up and down movement force oil up to tubing

8
  • Tertiary Recovery
  • When 2nd recovery no longer effective
  • Thermal Process
  • Steam Flooding steam injected, heats oil to
    flow readily
  • in-situ combustion (fire flooding) air
    injected, a portion if oil ignited , combustion
    front moves away from air injection well toward
    production well
  • CO2 injection
  • CO2 injected, mix with oil reduces forces that
    hold oil to pores, allows easily displace by
    injected water
  • Chemical recovery
  • Inject polymer into water phase of reservoir
    trap, large molecule add bulk to water, water
    thicken, wash oil from pores
  • Sometimes surfactant added to reduce force water
    to solid

9
  • Improvement of formation characteristic
  • To aid 3rd recovery because production drop
  • Acidizing
  • Injecting acid into a soluble formation (exp
    carbonate) to dissolve rocks
  • Enlarge the existing voids and increase
    permeability
  • Hydraulic Fracturing
  • Inject a fluid into formation under significant
    pressure to enlarge existing fracture and create
    new fracture
  • This fracture extend outward from well bore into
    formation therefore increase permeability

10
Petroleum Production System
  • Petroleum hydrocarbon production involve 2
    districts
  • Reservoir a porous medium with a unique storage
    and flow characteristic
  • Artificial structures includes well, bottom hole,
    surface gathering, separation and storage
    facilities
  • Production Engineering - attempts to maximize
    production in a cost effective way
  • Appropriate production technology and method
    related directly with other major area of
    petroleum engineering such as formulation
    evaluation, drilling and reservoir engineering
  • Petroleum Hydrocarbon
  • Mixture of many compounds petroleum and natural
    gas
  • Mixture depending on its composition and
    conditions of P and T occur as liquid or gas or
    mixture of 2 phase

11
Reservoir Engineering Fundamentals
  • Porosity
  • Define Porosity Total pore volume in the rock
    sample
  • Total rock sample volume (solidpore)
  • Mathematically
  • Range of porosity 0.1 to 0.3
  • Use reservoir core to measure porosity
  • Limitations
  • Rock sample must be large enough to obtain many
    sand grains and many pores to be representative
  • Features sample has a different type of pore
    space from sandstone

12
  • Fluid Saturation
  • Water saturation, Sw Volume filled by water
  • Total pore volume
  • Oil saturation, So Volume filled by oil
  • Total pore volume
  • If oil and water is the only fluid present, Sw
    So 1
  • In most oil fields Sw tends to increase as
    porosity decrease
  • Typical value of Sw 0.1 to 0.5
  • Free gas also present in oil pools,
  • Free gas saturation, Sg Volume filled by free
    gas
  • Total pore volume
  • 3 factors should always be remembered conceiving
    fluid saturation
  • It vary from place to place in reservoir rock Sw
    higher in less porous sections due to gravity
    segregation of the gas, oil and water

13
  • Vary with cumulative withdrawal oil produced
    replace by water or gas
  • Oil and gas saturation frequently expressed in
    terms of HC-filled pore space.
  • Pore space fV
  • HC-filled pore space SofV SgfV (1-Sw)fV
  • Therefore,
  • Oil saturations,
  • Gas saturations,

14
Example One of the most important determinations
for an oil accumulation is the volume of oil in
place. Suppose that in geological evidence is
known that the area extent of an oil reservoir is
2 million sqft and that the thickness of the bay
zone is 30 ft. If the sand porosity and water
saturation are 0.2 and 0.3, respectively, how
much oil is present? Solution Volume of bay
2,000,000 ft3 x 30 ft 6x107ft3 Total pore
volume 0.2 x 6x107 12x106 ft3 Then SwSo1
So 1 - 0.3 0.7 Total oil volume 0.7 x
12x106 8.4x106 ft3
15
  • Permeability
  • Measurement of the ease with which fluid flow
    through the rock
  • A function of a degree of interconnection between
    pores in the rock
  • The concept was introduced by Darcy in a
    classical experimental work from both petroleum
    engineering and ground water hydrology
  • The flow rate can be measured against pressure
    (head) for different porous media
  • The flow rate of fluid thru specific porous
    medium is linearly proportional top head
    difference btw the inlet and outlet and
    characteristic property of the medium, thus
  • u kDP
  • Where k permeability and is a characteristic
    property of
  • the porous medium

16
  • Suppose a cylindrical sample (core) of a porous
    rock is fully saturated with liquid of viscosity
    m.
  • Experimentally for a particular rock sample the
    expression
  • Darcy Equation
  • where k is constant
  • Q will increase a k increases, the higher the
    value of k the more readily will liquid flow
    through the core

l
A
Q
P1
P2
17
  • If in flow rate contain two fluid (oil and
    water), free gas is not present then,
  • If Q (cm3/s), m (cp), l (cm) A (cm2), and P1 and
    P2 (atm), the value of k in Darcy is
  • 1 Darcy 10-8 cm2

18
  • Oil Gravity
  • Commonly expressed in degree API
  • The terms heavy, medium and light crude cover
    approximately the ranges 10 to 20o, 20 to 30o and
    over 30o API, respectively
  • Instantaneous Water/Oil Ratio (WOR)
  • Homogeneous formation produce only oil and water
    (no free gas) then
  • The pressure drop in oil may differ slightly from
    that in the water owing to effect of capillary
    forces, so dividing the equations above, results
    in

19
  • At the surface
  • Or from above equation
  • (surface)
  • Where Bo is oil formation volume factor
  • Bo is defined as ratio of the volume of oil (plus
    the gas in solution) at reservoir T and P to the
    volume of oil at standard conditions (so-called
    stock-tank oil)

20
  • Instantaneous Gas/Oil Ratio (GOR)
  • Homogeneous formation producing only oil and gas
    (no water production, although water may be
    present in the formation)
  • Where the pressure drop across the distance dl is
    the same for both fluid, if capillary forces are
    neglected. Dividing
  • Stock-tank oil rate will be qo/Bo, and surface
    free gas rate qg/Bg. In addition to free gas
    produced from the formation, each barrel of
    stock-tank oil will release a volume Rs of gas,
    then the total surface gas/oil ratio is

21
  • At the surface
  • Therefore
  • (surface)
  • Productivity Index
  • Bottom hole flowing pressure - producing pressure
    (Pwf) at the bottom of the well
  • The difference btw this and the well static
    pressure (Ps) is

22
  • Ratio of producing rate of the well to its draw
    down is called Producing Index.
  • If the rate q (bbl/day) of stock-tank liquid and
    draw down (psi), the productivity index (J) is
    defined as
  • (bbl/day/psi)
  • Productivity index is based on the gross liquid
    rate (oil rate water rate)
  • Specific productivity index, Js is the number of
    barrel (gross) of stock-tank liquid
    produced/day/psi/ft net thickness
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