Pteg 324_lecture 4

Teaching Plan

Course Outline

PRE-UPSTREAM •Operating Agreements

UPSTREAM Exploration and Production • Exploration Operations • Drilling Operations • Completion Operations • Production Operations • Introductory Well Control • Gas Management

•Perforation and Well Activation •Production Tubing and Well Head Assembly •Self Flow and Artificial Methods of Production of Oil/Gas •Separation and Storage •Transportation, Field Processing and Refining •Marketing and Distribution

MID-STREAM • Transportation from producing field to refinery

DOWNSTREAM • Refinery Operations and Marketing

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Production Operations

Self Flow and Artificial Methods of Production of Oil/Gas

Petroleum Production System Petroleum hydrocarbon production involves 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

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Petroleum Production System Appropriate production technology and method is related directly with other major areas of petroleum engineering such as formation evaluation, drilling and reservoir engineering Petroleum Hydrocarbon i. Mixture of many compounds – petroleum and natural gas ii. Mixture depending on its composition and conditions of P and T, occur as liquid or gas or a mixture of the 2 phases

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Christmas Tree

Pipeline to Flow Process and Storage Surface Casing

Cement Intermediate Casing Cement

Production Casing

Completed Oil Well • Water Drive - Hydrostatic pressure pushes oil and gas to surface • Gas-Cap Drive - Expansion of gas under pressure pushes oil to surface

Tubing Completion Fluid Packer

Well Fluids

Cement

• Dissolved-Gas Drive - Gas disseminated in oil; usually requires pumping

Oil or Gas Zone Perforations

American Petroleum Institute, 1986

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Production Operations Once petroleum is found and well is drilled operation enters “production phase” After oil and gas is found, appraisal drilling need to be done to check for commercial viability Important to test the formation to ensure profit and determine proper rate of extraction For a new well to begin production, a potential test is run – to determine how much oil and gas can be produced in a 24 hr period Most efficient recovery (MER) rate – based on how much oil and gas can be extracted for a sustained period of time without harming the formation Some wells are under enough pressure and do not need a pumping system. Only install Christmas tree or a series of valves and pipes at the surface to produce oil and gas College of Engineering Studies

Production Operations Most wells 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

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Production Operations Glossary of Terms Formation i. Refers to either a certain layer of the earth’s crust or a certain area of layer. ii. It often refers to the area of rock where a petroleum reservoir is located

Christmas Tree i. Series of pipes and valves system for controlling the flow of oil from a well ii. Due to high underground pressures, oil can have self flow i.e. naturally lifted by gas or water drives ; thus no additional pumps needed College of Engineering Studies

Production Operations MER (Most Efficient Recovery) i.

MER rate: based on how much oil and gas that can be extracted for a sustained period of time without harming the formation

ii. Generally, most wells cannot work for 24 hrs, 7 days a week – this could damage the formation

Multiple Completions i.

Drilling single well at several different depth in formation

ii. Reason: increase production from a single well

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Reservoir Drive Mechanisms The energy that moves crude oil and natural gas from the subsurface rock to the production well is called the reservoir drive.

Natural Drive Mechanisms Dissolved Gas Drive - 5% to 30% recovery efficiency Natural gas is dissolved in oil at subsurface pressure in the reservoir. When oil is produced from the reservoir, reservoir pressure decreases and dissolved gas bubbles out of reservoir oil. This gas expands in the pore spaces and pushes the reservoir oil through the pores to a production well. College of Engineering Studies

Reservoir Drive Mechanisms

Gravity Drive - 50% to 65% recovery efficiency

Gravity drive is present in all reservoirs; it is simply the gravitational force of the Earth pulling oil downward within the reservoir. Gravity drive can be an important mechanism for a production well located on a flank of a reservoir, or for production over a long time, after the reservoir’s original drive mechanism has been depleted.

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Reservoir Drive Mechanisms

Combination Drive - 20% to 65% recovery efficiency A reservoir may be controlled by a combination of drive mechanisms, both natural and artificial, and dominance of one drive mechanism over another may change, or be altered by enhanced recovery, as production continues and reservoir pressure changes.

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Field Production 1.Primary Recovery (Natural Methods)

This is the first method of producing oil from a well Solution gas drive a. pressure inside reservoir relieved when well punctures and gas trapped in oil forms bubbles b. Bubbles grow, exert pressure push oil to well and up to surface (20-30%)

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Field Production 1.Primary Recovery (Natural Methods)

This is the first method of producing oil from a well Gas cap drive a. If gas cap present, drill well directly into oil layer – gas cap expands

b. Expanding gas pushes oil into well (40%)

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Reservoir Drive Mechanisms Gas Cap Drive - 20% to 40% recovery efficiency Because it is less dense than crude oil and water, natural gas segregates and occupies the higher zones within a reservoir. Natural gas forms a “gas-cap” over fluids and reservoir. As oil is produced, reservoir pressure decreases and natural gas in the gas cap expands and pushes the oil through the reservoir pores to production well. College of Engineering Studies

Field Production 1.Primary Recovery (Natural Methods)

This is the first method of producing oil from a well

Water drive scenario a. Water layer press against oil layer b. Water pushes oil towards surface and replace it within the pores of the reservoir rock

c. Highest recovery: up to 60%

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Reservoir Drive Mechanisms Water Drive - 35% to 60% recovery efficiency Because it is denser than oil or gas, water occupies the lower zones within a reservoir.

As oil is produced, reservoir pressure decreases and underlying water pushes overlying oil upward through the reservoir pores to take the place of produced oil.

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Field Production 2.Secondary Recovery

Used to enhance or replace primary techniques

Water flooding a. Additional injection well is drilled into the reservoir b. Pressure water injected c. Water displaces the oil in reservoir

Mechanical Lift a. Reciprocating or plunger pumping called “horsehead” b. Pump barrel lowered into well on 6 inch string steel rod (sucker rods) c. Up and down movement force oil up to tubing College of Engineering Studies

Artificial Lift If a well will not flow naturally, then it needs to be artificially lifted. This is done by either reducing the hydrostatic head or by using downhole pumps. The main systems used are: – Gas Lift – Electrical Submersible Pumps (ESP) – Beam Pumps – Hydraulic Pumps

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Gas Lift

Side Pocket Mandrel Gas Lift Valve

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Schematic of a gas-lift system

Pressure

FLP

Gradient (reduced)

Gas Injection

Depth

Drawdown P(res)

GASLIFTED WELL

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Downhole Pumps Downhole pumps increase the pressure at the bottom of the tubing to a sufficient amount to lift the liquid stream to the surface, instead of lowering the pressure gradient in the tubing to reduce the bottomhole pressure, as in gas lift

Pressure

FLP

Liquid Gradient

Pump Drawdown P(res)

PUMP LIFTED WELL

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ESPs Electrical Submersible Pumps The pressure is raised by transforming mechanical work into potential energy, that is, pressure. Liquid enters the pump at a given pressure, called suction pressure, and leaves it at a higher pressure, called discharge pressure

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Main components ESP

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Electrical Submersible Pump Oil flows up, through suction side of impeller, and is discharged with higher pressure (the discharge pressure), via the diffuser. The pressure is raised by transforming mechanical work into potential energy, that is, pressure. This is done by Impeller increasing the velocity of the fluid by the impeller and then reducing the velocity back again transferring the energy into Diffuser pressure. EP Learning and Leadership Development

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Beam Pumps

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Hydraulic Piston Pumps

Piston pump is a positive displacement pump Consists of an engine and pump sections Engine is driven by hydraulic power fluid from the surface

Double acting, pumping during upstroke and down stroke

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Hydraulic piston pump

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Selection of Artificial Lift Main considerations include: Reservoir parameters (pressure, PI, water cut, sand, GOR) Well parameters (deviation, completion design) Location (onshore/offshore) Cost Reliability Local experience, availability of resources, workover possibilities, standardization College of Engineering Studies

Selection of Artificial Lift Artificial lift selection is dependent on a wide range of factors. The important point is that you design for artificial lift up front, not just on your well but also the facilities. As far as the well is concerned, you can always do a workover to install artificial lift later in the well’s life. However, on the facilities side, you may need to install extra equipment (compressors, flowlines, cables) and find additional electrical capacity to power the pumps or compressors. Onshore this is less of a problem, but offshore it could be difficult to install an extra generator or compressor. College of Engineering Studies

Producing Wells

Secondary Recovery

Injection Wells

Tertiary Recovery

Of 60% Remaining in Reservoir

Water Gas Steam Chemical Fire

Pumped into the reservoir to force additional petroleum out of the pores in the reservoir rock College of Engineering Studies

Artificial Drive Mechanisms Enhanced Oil Recovery If a reservoir’s natural drive mechanism becomes insufficient in aiding hydrocarbon production, a supplement drive mechanism may be introduced to increase production rate and recovery efficiency.

Water Injection - 5% to 50% recovery efficiency of remaining hydrocarbons Water injection into a hydrocarbon reservoir sweeps the less-dense hydrocarbons through reservoir pore space.

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Field Production 3. Tertiary Recovery When secondary recovery is no longer effective Thermal Process a. Steam Flooding – steam injected, heats oil to flow readily b. in-situ combustion (fire flooding) – air injected, a portion if oil ignited , combustion front moves away from air injection well toward production well

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Artificial Drive Mechanisms

Steam Injection - 25% to 65% recovery efficiency of remaining hydrocarbons Injected steam heats the reservoir hydrocarbons. Some oil is vaporized into gas and some oil is made less viscous. The steam in the reservoir cools and condenses into water, which drives the gas and less-viscous oil toward production wells.

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Field Production 3. Tertiary Recovery When secondary recovery is no longer effective

CO2 injection CO2 injected, mix with oil – reduces forces that hold oil to pores, allows easy displacement by

injected water

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Artificial Drive Mechanisms

Miscible Gas Injection - up to 35% recovery efficiency of remaining hydrocarbons Rich gas which can be dissolved in (i.e., is miscible with) hydrocarbons is injected into the reservoir. As the gas mixes with the hydrocarbons it makes the hydrocarbons more fluid and pushes the more-fluid oil through the reservoir pores.

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Field Production 3. Tertiary Recovery When secondary recovery is no longer effective Chemical recovery i. Inject polymer into water phase of reservoir trap, large molecule add bulk to water, water thicken, wash oil from pores ii. Sometimes surfactant added to reduce force water to solid

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Artificial Drive Mechanisms

Chemical Injection - 25% to 40% recovery efficiency of remaining hydrocarbons Chemicals injected into a reservoir reduce the hydrocarbons’ surface tension from the reservoir rock.

A subsequent flush of injected water into the reservoir sweeps the freed hydrocarbons through the reservoir pores.

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Field Production 4. Improvement of formation characteristic To aid Tertiary recovery because of production drop

Acidizing a. Injecting acid into a soluble formation (exp: carbonate) to dissolve rocks

b. Enlarge the existing voids and increase permeability

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Field Production 4. Improvement of formation characteristic To aid Tertiary recovery because of production drop Hydraulic Fracturing a. Inject a fluid into formation under significant pressure to enlarge existing fracture and create new fracture b. This fracture extend outward from well bore into formation therefore increase permeability

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Revision Aids 14. Briefly explain why it is desirable to use a production tubing to lift crude oil from the reservoir to surface facilities. 15. What are the devices that make up a wellhead assembly, and explain the usefulness of each device. 16.Write short notes on the following primary production methods: (a). Solution gas drive (b). Gas cap drive (c). Water drive 17.(a) Explain why EOR – enhanced oil recovery, may be necessary to bring crude oil to the surface. (b). Describe the principle behind any three EOR methods. College of Engineering Studies