Natural Gas Production and Processing: A Comprehensive Overview, Essays (university) of Petrology

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Oil and gas production handbook

An introduction to oil and gas production,

transport, refining and petrochemical

industry

Håvard Devold

I

9 Unconventional and conventional resources and environmental effects

• ISBN 978-82-997886-3-
• 1 Introduction............................................................................................. CONTENTS
• 2 Facilities and processes
• 2.1 Exploration
• 2.2 Production
• 2.2.1 Onshore
• 2.2.2 Offshore
• 2.3 Upstream process sections
• 2.3.1 Wellheads
• 2.3.2 Manifolds and gathering
• 2.3.3 Separation...........................................................................
• 2.3.4 Metering, storage and export
• 2.3.5 Utility systems
• 2.4 Midstream
• 2.4.1 Gas Plants
• 2.4.1 Gas compression
• 2.4.2 Pipelines
• 2.4.1 LNG liquefaction and regasification facilities
• 2.5 Refining
• 2.6 Petrochemical
• 3 Reservoir and wellheads
• 3.1 Crude oil and natural gas
• 3.1.1 Crude oil..............................................................................
• 3.1.2 Natural gas..........................................................................
• 3.1.3 Condensates
• 3.2 The reservoir
• 3.3 Exploration and drilling
• 3.4 The well
• 3.4.1 Well casing..........................................................................
• 3.4.2 Completion
• 3.5 Wellhead
• 3.5.1 Subsea wells
• 3.5.2 Injection...............................................................................
• 3.6 Artificial lift
• 3.6.1 Rod pumps..........................................................................
• 3.6.2 ESP
• 3.6.3 Gas lift
• 3.6.4 Plunger lift
• 3.7 Well workover, intervention and stimulation
• 4 The upstream oil and gas process
• 4.1 Manifolds and gathering
• 4.1.1 Pipelines and risers II
• 4.1.2 Production, test and injection manifolds
• 4.2 Separation
• 4.2.1 Test separators and well test
• 4.2.2 Production separators
• 4.2.3 Second stage separator
• 4.2.4 Third stage separator
• 4.2.5 Coalescer
• 4.2.6 Electrostatic desalter
• 4.2.7 Water treatment
• 4.3 Gas treatment and compression
• 4.3.1 Heat exchangers
• 4.3.2 Scrubbers and reboilers
• 4.3.3 Compressors, anti-surge and performance
• 4.4 Oil and gas storage, metering and export
• 4.4.1 Fiscal metering....................................................................
• 4.4.2 Storage
• 4.4.3 Marine loading
• 5 Midstream facilities
• 5.1 Gathering
• 5.2 Gas plants
• 5.2.1 Gas composition
• 5.3 Gas processing............................................................................
• 5.3.1 Acid gas removal
• 5.3.2 Dehydration.........................................................................
• 5.3.3 Mercury removal
• 5.3.4 Nitrogen rejection
• 5.3.5 NGL recovery and treatment
• 5.3.6 Sales gas specifications
• 5.4 Pipelines
• 5.4.1 Pipeline terminal
• 5.4.2 Gas Pipelines, compressor and valve stations
• 5.4.3 Liquid pipelines, pump and valve stations
• 5.4.4 Pipeline management, control and safety
• 5.5 LNG
• 5.5.1 LNG liquefaction
• 5.5.2 Storage, transport and regasification
• 6 Refining
• 6.1 Fractional distillation
• 6.2 Basic products
• 6.3 Upgrading and advanced processes
• 6.4 Blending and distribution
• 7 Petrochemical.......................................................................................
• 7.1 Aromatics III
• 7.1.1 Xylene and polyester chain.................................................
• 7.1.2 Toluene, benzene, polyurethane and phenolic chain
• 7.1.3 Benzene and styrenic chain, derivatives
• 7.2 Olefins
• 7.2.1 Ethylene, derivatives
• 7.2.2 Propylene, derivatives
• 7.2.3 Butadiene, butylenes, and pygas, derivatives
• 7.3 Synthesis gas (syngas)
• 7.3.1 Methanol based products
• 7.3.2 Ammonia based products
• 8 Utility systems
• 8.1 Process control systems............................................................
• 8.1.1 Safety systems and functional safety
• 8.1.2 Emergency shutdown and process shutdown
• 8.1.3 Fire and gas system
• 8.1.4 Control and safety configuration
• 8.1.5 Telemetry/SCADA
• 8.2 Digital oilfield
• 8.2.1 Reservoir management and drilling operations
• 8.2.2 Production optimization
• 8.2.3 Asset optimization and maintenance support
• 8.2.4 Information management systems (IMS)
• 8.2.5 Training simulators
• 8.3 Power generation, distribution and drives
• 8.4 Flare and atmospheric ventilation
• 8.5 Instrument air.............................................................................
• 8.6 HVAC
• 8.7 Water systems
• 8.7.1 Potable water
• 8.7.2 Seawater
• 8.7.3 Ballast water
• 8.8 Chemicals and additives
• 8.9 Telecom
• 9.1 Unconventional sources of oil and gas......................................
• 9.1.1 Extra heavy crude
• 9.1.2 Tar sands
• 9.1.3 Oil shale
• 9.1.4 Shale gas and coal bed methane
• 9.1.5 Coal, gas to liquids and synthetic fuel
• 9.1.6 Methane hydrates
• 9.1.7 Biofuels IV
• 9.1.8 Hydrogen
• 9.2 Emissions and environmental effects
• 9.2.1 Indigenous emissions
• 9.2.2 Greenhouse emissions
• 9.2.3 Carbon capture and sequestration
• 10 Units
• 11 Glossary of terms and acronyms
• 12 References
• 13 Index...................................................................................................

barrels per day in October, 1861, and the Woodford well on the left came in at 1,500 barrels per day in July, 1862.

The oil was collected in the wooden tank pictured in the foreground. As you will no doubt notice, there are many different-sized barrels in the background. At this time, barrel size had not been standardized, which made statements like "oil is selling at $5 per barrel" very confusing (today a barrel is 159 liters (see units on p. 141). But even in those days, overproduction was something to be avoided. When the "Empire well" was completed in September 1861, it produced 3,000 barrels per day, flooding the market, and the price of oil plummeted to 10 cents a barrel. In some ways, we see the same effect today. When new shale gas fields in the US are constrained by the capacity of the existing oil and gas pipeline network, it results in bottlenecks and low prices at the production site.

Soon, oil had replaced most other fuels for motorized transport. The automobile industry developed at the end of the 19 th^ century, and quickly adopted oil as fuel. Gasoline engines were essential for designing successful aircraft. Ships driven by oil could move up to twice as fast as their coal- powered counterparts, a vital military advantage. Gas was burned off or left in the ground.

Despite attempts at gas transportation as far back as 1821, it was not until after World War II that welding techniques, pipe rolling, and metallurgical advances allowed for the construction of reliable long distance pipelines, creating a natural gas industry boom. At the same time, the petrochemical industry with its new plastic materials quickly increased production. Even now, gas production is gaining market share as liquefied natural gas (LNG) provides an economical way of transporting gas from even the remotest sites.

With the appearance of automobiles and more advanced consumers, it was necessary to improve and standardize the marketable products. Refining was necessary to divide the crude in fractions that could be blended to precise specifications. As value shifted from refining to upstream production, it became even more essential for refineries to increase high-value fuel yield from a variety of crudes. From 10-40% gasoline for crude a century ago, a modern refinery can get up to 70% gasoline from the same quality crude through a variety of advanced reforming and cracking processes.

Chemicals derived from petroleum or natural gas – petrochemicals – are an essential part of the chemical industry today. Petrochemistry is a fairly young

industry; it only started to grow in the 1940s, more than 80 years after the drilling of the first commercial oil well.

During World War II, the demand for synthetic materials to replace costly and sometimes less efficient products caused the petrochemical industry to develop into a major player in modern economy and society.

Before then, it was a tentative, experimental sector, starting with basic materials:

• Synthetic rubbers in the 1900s
• Bakelite, the first petrochemical-derived plastic, in 1907
• First petrochemical solvents in the 1920s
• Polystyrene in the 1930s And it then moved to an incredible variety of areas:
• Household goods (kitchen appliances, textiles, furniture)
• Medicine (heart pacemakers, transfusion bags)
• Leisure (running shoes, computers...)
• Highly specialized fields like archaeology and crime detection

With oil prices of $100 a barrel or more, even more difficult-to-access sources have become economically viable. Such sources include tar sands in Venezuela and Canada, shale oil and gas in the US (and developing elsewhere), coal bed methane and synthetic diesel (syndiesel) from natural gas, and biodiesel and bioethanol from biological sources have seen a dramatic increase over the last ten years. These sources may eventually more than triple the potential reserves of hydrocarbon fuels. Beyond that, there are even more exotic sources, such as methane hydrates, that some experts claim can double available resources once more.

With increasing consumption and ever-increasing conventional and unconventional resources, the challenge becomes not one of availability, but of sustainable use of fossil fuels in the face of rising environmental impacts, that range from local pollution to global climate effects.

An offshore well typically costs $30 million, with most falling in the $10-$ million range. Rig leases are typically $200,000 - $700,000 per day. The average US onshore well costs about $4 million, as many have much lower production capacity. Smaller companies exploring marginal onshore fields may drill a shallow well for as little as $100,000.

This means that oil companies spend much time on analysis models of good exploration data, and will only drill when models give a good indication of source rock and probability of finding oil or gas. The first wells in a region are called wildcats because little may be known about potential dangers, such as the downhole pressures that will be encountered, and therefore require particular care and attention to safety equipment.

If a find (strike, penetration) is made, additional reservoir characterization such as production testing, appraisal wells, etc., are needed to determine the size and production capacity of the reservoir in order to justify a development decision.

2.2 Production

This illustration gives an overview of typical oil and gas production facilities:

Figure 1. Oil and gas production facilities

Although there is a wide range of sizes and layouts, most production facilities have many of the same processing systems shown in this simplified overview:

Figure 2. Oil and gas production overview

Production Wellheads

Production and Test Manifolds

ø

Test Separator

Production Separators 1 stage

2 stage

Water treatment

Gas compressors

LP HP

Metering and storage

Pig Launcher MeterGas

MeterOil

Gas Pipeline

Oil Storage

Crudepump

LauncherPig PipelineOil

LoadingTanker

Injection wells

Injection manifold Water injection pump

Gas injection compressor

Utility systems (selected)

Power Generation

Instrument Air

Potable Water

Firefighting systems

HVAC

Export

Drilling

Mud and Cementing

day GOSP. Product is sent from the plant by pipeline or tankers. The production may come from many different license owners, so metering of individual well-streams into the gathering network are important tasks.

Unconventional plays target very heavy crude and tar sands that became economically extractable with higher prices and new technology. Heavy crude may need heating and diluents to be extracted. Tar sands have lost their volatile compounds and are strip-mined or can be extracted with steam. It must be further processed to separate bitumen from the sand. Since about 2007, drilling technology and fracturing of the reservoir have allowed shale gas and liquids to be produced in increasing volumes. This allows the US in particular to reduce dependence on hydrocarbon imports. Canada, China, Argentina, Russia, Mexico and Australia also rank among the top unconventional plays. These unconventional reserves may contain more 2-3 times the hydrocarbons found in conventional reservoirs. These pictures show the Syncrude Mildred plant at Athabasca, Canada Photo: GDFL Jamitzky/Wikimedia and the Marcellus Shale in Pennsylvania. Photo: GDFL Ruhrfisch /Wikimedia

2.2.2 Offshore

A whole range of different structures is used offshore, depending on size and water depth. In the last few years, we have seen pure sea bottom installations with multiphase piping to shore, and no offshore topside structure at all. Replacing outlying wellhead towers, deviation drilling is used to reach different parts of the reservoir from a few wellhead cluster locations.

Some of the common offshore structures are:

Shallow water complex , which is characterized by several independent platforms with different parts of the process and utilities linked with gangway bridges. Individual platforms include wellhead riser, processing, accommodations and power generation platforms. (This picture shows the BP Valhall complex.) Typically found in water depths up to 100 meters.

Gravity bas e consists of enormous concrete fixed structures placed on the bottom, typically with oil storage cells in a "skirt" that rests on the sea bottom. The large deck receives all parts of the process and utilities in large modules. Large fields at 100 to 500 meters of water depth were typical in the 1980s and 1990s. The concrete was poured at an onshore location, with enough air in the storage cells to keep the structure floating until tow-out and lowering onto the seabed. The picture shows the world's largest GBS platform, Troll A, during construction. Photo Statoil

Compliant towers are much like fixed platforms. They consist of a narrow tower, attached to a foundation on the seafloor and extending up to the platform. This tower is flexible, as opposed to the relatively rigid legs of a fixed platform. Flexibility allows it to operate in much deeper water, as it can absorb much of the pressure exerted by the wind and sea. Compliant towers are used between 500 and 1,000 meters of water depth.

Floating production , where all topside systems are located on a floating structure with dry or subsea wells. Some floaters are:

A variation of the FPSO is the Sevan Marine design. This uses a circular hull which shows the same profile to wind, waves and current, regardless of direction. It shares many of the characteristics of the ship-shaped FPSO, such as high storage capacity and deck load, but does not rotate and therefore does not need a rotating turret. Photo: Sevan Marine

Tension Leg Platform (TLP – left side in picture) consists of a structure held in place by vertical tendons connected to the sea floor by pile-secured templates. The structure is held in a fixed position by tensioned tendons, which provide for use of the TLP in a broad water depth range up to about 2,000m. The tendons are constructed as hollow high tensile strength steel pipes that carry the spare buoyancy of the structure and ensure limited vertical motion.

Semi-submersible platforms (front of picture) have a similar design but without taut mooring. This permits more lateral and vertical motion and is generally used with flexible risers and subsea wells.

Similarly, Seastar platforms are miniature floating tension leg platforms, much like the semi- submersible type, with tensioned tendons.

SPAR consists of a single tall floating cylindrical hull, supporting a fixed deck. The cylinder does not, however, extend all the way to the seabed. Rather, it is tethered to the bottom by a series of cables and lines. The large cylinder serves to stabilize the platform in the water, and allows for movement to absorb the force of potential hurricanes. SPARs can be quite large and are used for

water depths from 300 up to 3,000 meters. SPAR is not an acronym, and is named for its resemblance to a ship's spar. SPARs can support dry completion wells, but are more often used with subsea wells.

Subsea production systems are wells located on the sea floor, as opposed to the surface. As in a floating production system, the petroleum is extracted at the seabed, and is then “tied-back” to a pre-existing production platform or even an onshore facility, limited by horizontal distance or "offset.” The well is drilled by a movable rig and the extracted oil and natural gas is transported by undersea pipeline and riser to a processing facility. This allows one strategically placed production platform to service many wells over a reasonably large area. Subsea systems are typically used at depths of 500 meters or more and do not have the ability to drill, only to extract and transport. Drilling and completion is performed from a surface rig. Horizontal offsets of up to 250 kilometers/ miles are currently possible. The aim of the industry is to allow fully autonomous subsea production facilities, with multiple wellpads, processing, and direct tie-back to shore. Photo: Statoil

2.3 Upstream process sections

We will go through each section in detail in the following chapters. The summary below is an introductory synopsis of each section. The activities up to the producing wellhead (drilling, casing, completion, wellhead) are often called “pre-completion,” while the production facility is “post-completion.” For conventional fields, they tend to be roughly the same in initial capital expenditure.

2.3.1 Wellheads

The wellhead sits on top of the actual oil or gas well leading down to the reservoir. A wellhead may also be an injection well, used to inject water or gas back into the reservoir to maintain pressure and levels to maximize production.