Meeting the Energy Needs of Tomorrow

- Well Drilling and

Shale Gas Fracturing (‘Fracking’).

Mechanical Engineering

Keith Shotbolt B.Sc. 1962 4th February 2013

Note: Total demand is approximately 220 million tonnes of oil equivalent per year. Oil provides 42% and gas provides 34% + 9% (share of electricity generation), giving a total of 85% for oil and gas. On 24 Jan 2013, Ed Davey, Secretary of State for Energy, said: “Oil and gas will form an integral part of the UK energy mix for decades to come. Over 70 percent of the UK's primary energy demand may still be filled by oil and gas into the 2040s.”

1 tonne of oil equivalent = 11,630 kWh. The energy demand of the average house is around 20,000kWh per annum. Approximately 25% of that is for electricity. UK houses have mainly gas fired heating.

Source: http://www.decc.gov.uk/en/content/cms/statistics/publications/ecuk/ecuk.aspx Table 1.5.

UK Energy Demand Percentage of Total

Year 1970 2010 Future

Coal and coke (exc. Electricity gen.) 29.0 1.3 Further decline

Coal gas 7.5 0.0

Natural gas 2.5 34.0 Imports zero in 2000 - now around 50%

Electricity 11.3 19.0 Increasing

Biomass and Waste 0.0 2.0 Increasing

Oil (Transport, Industry and Heating) 47.0 42.0 Gradually decreasing

Natural gas (methane - CH4) is formed by rotting vegetation, animal digestion, and in stagnant ponds and swamps.

Deep oil and gas deposits were formed from dead animals and plants being covered by layers of sedimentary rock. The sediments consist of small particles which were carried down by rivers from exposed areas of land into the sea. The thickness of sedimentary rock over North Sea oil and gas fields is around 2 to 3 km.

Most oil and gas produced to date has been from relatively permeable, large-grained sandstone or limestone, where the hydrocarbons can flow readily into the wellbores. When the reservoir pressure drops in old wells, production has been increased by acidizing and/or hydraulic fracturing the sandstone to ease release of hydrocarbons. Fracturing or ‘fracking’ was first used in 1947. There will be more detail on that later.

Installed wind power capacity at end of 2012 was 7,800 MW (~14% of 56,000 MW peak demand). There are over 4,200 wind turbines, and the average size is of the latest machines is around 3MW. By 2020, installed wind power capacity could be around 50% of electricity demand, needing approximately 7,000 more turbines. Nuclear Plant Accidents: 1979 – Three Mile Island, USA. 1986 – Chernobyl, Russia.

2011 – Fukushima, Japan.

Electricity Generation Percentage of Total

Year 2010 Future

Natural Gas 47.0 Steady

Coal 28.0 In decline. Drax converting to 50% biomass-fired.

Nuclear 16.0 Accidents - USA, Russia, Japan

Renewables (wind, biomass, hydro) 7.0 Target is 20% by 2020

Oil 1.0

Imports (mainly from France) 1.0

INFRASTRUCTURE. The UK has a vast pipeline network, mainly for the distribution of natural gas (red). The National Grid company is responsible for operation, maintenance and investment of both gas and electricity grids.

History of Natural Gas supplies into Europe

1959 - Discovery of large Groningen gas field in Netherlands

1965 - Discovery of first UK offshore gas field, West Sole

1970-90 - Installation of ten 56-inch gas pipelines from Siberia

1990-2010 - Large gas pipelines installed from Norway and Algeria.

Also, Liquefied Natural Gas (LNG) supplies begin from Qatar and others.

Advantages of using methane as a fuel are that a) it is clean to handle

by pipeline, and b) generates around half the CO2 than an equivalent

amount of energy produced from burning coal.

Western Europe sources most of its natural gas from Russia. Possible routes of future gas lines are shown in blue. A 2005 Study described the importance of Russian gas, see: http://www.centrex.at/en/files/study_stern_e.pdf

Modern gas-fired power stations use the Combined Cycle Gas Turbine (CCGT), which has

an associated steam turbine to extract energy from the hot exhaust gases. One CCGT can

generate up to 500 MW with 70/30 split of gas/steam power.

General Electric (USA), Mitsubishi (Japan), Siemens (Germany) and Alsthom (France) are

competing in this market, and claim up to 60% efficiency on their largest machines.

This new 2400 MW power station at Willington, Derbyshire is proposed by

RWE npower.

There will be four 500 MW CCGT units and four 100 MW open cycle units.

The latter can go from start-up to full power in 10 minutes for rapid response to

change in demand.

Rolls Royce supplies the open cycle type, which are based on aircraft engines.

Costs. Extract from: http://en.wikipedia.org/wiki/Wind_power_in_the_United_Kingdom

A 2004 study by the Royal Academy of Engineering found that wind power cost 5.4

pence per kW·h for onshore installations and 7.2 pence per kW·h for offshore,

compared to 2.2p/kW·h for gas and 2.3p/kW·h for nuclear.

By 2011 onshore wind costs at 8.3/kW·h had fallen below new nuclear at

9.6p/kW·h,

However, offshore wind costs at 16.9p/kW·h were significantly higher than early

estimates mainly due to higher build and finance costs,.

Wind-generated power is a variable resource. The amount of electricity produced at

any time and location depends on wind speeds, air density, and turbine

characteristics.

In June 2011 several energy companies told the government that 17 gas-fired plants

costing £10 billion would be needed by 2020 to act as back-up generation for wind.

The companies said they would require "capacity payments" to make the investment

economic, on top of the subsidies already paid for wind.

From 1970 to 1998, the price of gas in the USA averaged between 2.0 and 2.5 dollars

per 1000 cu.ft.. The country then started to import more LNG, and the price averaged in

excess of 5 dollars per 1000 cu.ft. from 2003 to 2009.

Between 2006 and 2010, shale (fine-grained, laminated and fissile mudstone) gas

production increased from 0.7 trillion to 4.6 trillion cu.ft. per annum. This trend has

continued and both domestic and industrial consumers are benefiting from the reduced

price of gas.

Shale gas developments have been made economic by adapting directional drilling

and fracturing technologies – mainly used offshore until 2005.

Well Drilling.

Access to liquid and gas hydrocarbon fuels is done by drilling a well into

the producing rock stratum.

This process is obviously much easier than sinking a mine shaft to allow

men to mine coal, and then providing transport to market. When I started

at University in 1959, Britain was a coal-based economy for house heating,

electricity generation and railway locomotives.

The first significant gas field in the UK North Sea was not discovered until

1965, and an oil discovery followed in 1969. I was employed in the oil and

gas industry from 1974 to retirement in 2006.

In most cases, the oil and/or gas have sufficient pressure to flow out of the

well and into a gathering pipeline system.

Well Drilling is the foundation of present-day standards of living. This

video 01 shows the basic requirements for drilling a vertical onshore well.

Drilling Safety for Personnel and the Environment depends on:

1. Good Mud Density Control

2. Good Cementing of Casing, and

3. An Effective Blowout Preventer (BOP).

1. Mud is circulated down the drill pipe, through the bit and back up the annulus.

This keeps the bit cool, carries the cuttings back to surface pits, and balances

the pressure of fluids in any stratum or formation.

2. Each casing must be cemented in place to form an effective seal to prevent

one stratum ‘leaking’ into an adjacent stratum. For example, it is not acceptable

for methane to leak into a fresh water aquifer that is, or may be used for

domestic consumption. The casing should be centralised in the hole to ease

cement flow around its circumference.

3. If the drill bit hits a stratum containing high pressure fluids, and the drillers

cannot adjust the mud density to balance the high pressure, the fluids may start

to rise up the well bore. It is essential that fluids are contained in the well and

this is done by closing one or more annular or ram type blowout preventers.

Simplified Video 02 : Basic steps for drilling any hydrocarbon well.

Casing centralisers have bow springs to hold the casing central in the hole as

cement is displaced up the annulus.

Poor centralising can lead to leaks from one stratum to another.

BP’s report (Figure 1) states that the primary reservoir sands extended from 18,051 ft to

18,223 ft. This diagram shows that the hole diameter reduced from 9.875” to 8.5” at

18,126 ft depth – approximately half way through the pay zone.

The annular gap around the 7” casing in the 8.5” hole was only 0.75”, instead of the 1.5”

to 2” recommended by Halliburton, the cementing Contractor. This tight annulus caused a

restriction to mud flow, and a pressure of 3,142 psi was needed to establish circulation.

Details at Bottom of Macondo Blowout well

Rig Deck

Casing String in

Mud-filled Riser

and Well.

Derived Units N ..kg m sec2

bar ..100000N m2

tonne .1000kgf

Density of mud at Macondo well mud ..14.17lbf gal1

=mud 1.698103 .kgf m

3

Density of Steel ..7850kgf m3

Length of Pipe L .18300ft =L 5.578103

m

Pressure at 18,300ft depth P .mud L =P 1.347104

psi =P 928.772bar

Extension of long piece of steel rod or pipe under own weightExt=WL/2AE=density.A.L^2/2.A.E

Pipe Young's ModulusE ..200000N mm2

Relative density of pipe in mud steelinmud mud

Extension of pipe in m ud =steelinmud 6.152103 .kgf m

3Ext

.steelinmud L2

.2 E=Ext 4.693m

Outside diameterD .7 in Inside diameterd .6 in Wall thickness t .0.5 in

Casing String Weight W ...steelinmud

4D

2d

2L =W 226.041 tonne

Casing Yield Stress S .125000psi Pressure to Yield Py ..2 tS

d=Py 1.43610

3bar

Basic Calculations using Macondo Data

This float collar is designed to allow mud to enter as the casing string is lowered downhole. Flow

in the upwards direction will raise the Auto-Fill Ball to its position as shown. After landing the

casing in its wellhead hanger, mud is pumped down the string and the ball settles in its seat at

the bottom of the Tube.

Initially, flow is limited by having to pass through the small circulation port(s). The pump flow

must be increased to above 7 bpm, to induce a pressure drop of around 500 psi, and the entire

Auto-Fill Tube is ejected when its retaining pins shear. After Tube ejection, the two Check Valves

are spring-closed - as required to prevent back flow of cement.

At Macondo, mud circulation down the casing began at the ninth attempt after raising the pump pressure to

3,142 psi. The flow rate of mud did not exceed 4 bpm, which was not sufficient to eject the Auto-Fill Tube. BP’s

procedure stated that 8 bpm was required.

Cementing proceeded a) without flushing the annulus around the shoe track at sufficiently high rate and

duration to ensure full circumferential removal of compressed sediment and good distribution of cement, and b)

without converting the float collar to activate its two check valves to prevent cement backflow.

There was no cementing evaluation log at Macondo, which may have shown it to be inadequate.

Drill pipe was run to 8,367ft ready for mud displacement. During the ‘negative pressure test’, for which there

was no detailed procedure, no flow from the kill line was accepted and 1,400 psi on the drill pipe was ignored.

While displacing the mud with seawater, reservoir fluids rising up the casing should have been detected by

water inflow and mud outflow monitoring before arrival of hydrocarbons at the rig floor, but no reasonably

accurate outflow versus inflow observations were made.

After uncontrolled arrival of oil and gas at the rig floor, the blind-shear rams in the BOP stack failed to close due

to the presence of off-centre drill pipe.

US Gulf of Mexico

Deepwater Horizon rig – 21st April 2010

11 Men Died

What went Wrong?

This diagram shows off-centre drill pipe between the two blind-shear rams (BSRs)

as contact is first made. The upper BSR has blades with a Vee having sides set at

80 degrees to the axis of motion, and providing very little centralising effect. The

lower BSR has its straight blade perpendicular to the motion axis, with no

centralising effect. Neither ram has side extensions to prevent an outer fold of

material being squeezed between the outer ram faces, thus preventing closure.

Macondo Blind-shear Rams

Directional or Deviated Drilling.

In the mid-1970s at BP’s Forties field in the North Sea, a single platform

could drill multiple wells typically tp 3000m below seabed and out to

2000m radius. The hole through the reservoir rock was returned closer to

vertical to aid wireline operations, which depend on gravity.

Mud Motor.

Hydraulic pumps and motors can be manufactured as helical screws, with one less

lobe on the rotor than in the stator.

When drilling the ‘build’ or bend section of the well, the drill string does not rotate,

and the drill bit is turned by a mud motor at the bottom, as shown in this short

video 03. A typical build rate is 6 degrees per 30 m – giving a radius of ~300m.

Perforating the Casing and Improving Flow into the Wellbore.

After cementing the casing through the producing formation (pay zone) a

perforating gun with multiple explosive charges punches holes through the casing

wall.

If the formation has low permeability, flow into the well can be improved by

acidizing or fracturing. This artist’s impression shows fractures expected in a tight

sandstone formation. Run video 04.

Extract from: http://www.netl.doe.gov/technologies/oil-gas/publications/brochures/Shale_Gas_March_2011.pdf

In the 1990s, long sidetrack horizontal wells were drilled into the 25m thick oil

reservoir under the Troll gas field offshore Norway.

This well configuration, with long horizontal portions in the producing formation,

is used for onshore shale gas developments in the USA.

Experience in the USA has shown that mutiple small stages of fracturing over

a longer length cause less damage and are more effective producers than the

earlier wells, which had a shorter horizontal section and fewer perforations.

There follows a video 05 showing shale gas development in Quebec, Canada.

UK Beneficiary of Shale Gas Developments.

KCA DEUTAG is one of the largest international drilling contractors. The company

employs 8,000 staff in more than 22 countries and it had revenue in 2010 of

US$1.34 billion.

KCA DEUTAG is currently the drilling operations contractor on 33 offshore

platforms worldwide and owns and operates a fleet of mobile offshore drilling units

consisting of 3 jack-ups and 3 self erecting tender barges. The company also owns

and operates a fleet of more than 60 land drilling rigs.

The headquarters are in Aberdeen, Scotland. There is an office in Bad Bentheim,

Germany, where the central technical support function is located, and regional

offices in key operational areas - Russia, the Middle East, the Caspian region and

Norway.

UK Beneficiary of Shale Gas Developments.

Hunting PLC is an international energy

services provider that manufactures and

distributes products that enable the

extraction of oil and gas for the world’s

leading companies.

The global "Upstream" activity is co-

ordinated through Hunting Energy Services

with a large presence in North America,

Europe, the Middle East and Asia. The

company owns and develops proprietary

patented products including premium

casing connections, burst discs, make up

processes, coating of threads and mud-

motors.

In strategic locations around the world

Hunting owns and operates plants,

properties and equipment employing people

to serve its global customers with local

services and products.

UK Beneficiary of Shale Gas Developments.

Weir PLC is a leading global engineering solutions provider. It designs,

manufactures and supplies innovative products and expert engineering services for

the minerals, oil & gas and power & industrial markets.

Weir operates on a global scale, with around 50 manufacturing facilities and over

120 service facilities around the world. The business operations are structured

across three sector-focused divisions:

The Oil & Gas division supplies pumps like the one shown above for fracturing

shale gas in the USA. Pressures can reach 1000 bar (100,000 kPa).

Major Concerns about Onshore Drilling and Fracturing:

1. Contamination of Ground and Drinking Water

2. Earthquakes

1. Fluids associated with shale gas developments can be contained provided the

well casing is correctly cemented, and waste water disposal is controlled. Some

contractors have been known to ‘cut corners’ and problems often result. Workers

do not like their activities being watched, but crucial stages must be performed to

standard procedures and specifications. The Macondo blowout is an example of

badly performed and inadequately regulated activities. My own experience of

oilfield Projects often involved four organisations. The Main Contractor, a Project

Management Contractor, a Certifying Authority, and the Owner/Operator.

2. Since 2002, there have been 3 earthquakes in the UK >4.0 on the Richter

scale. The largest was in Dudley measuring 4.7. There have been 19 quakes

>3.0, and each year there are 10 quakes >2.5. Quakes near Blackpool in Spring

of 2011 were 2.3 and 1.5. They were attributed to fracking, which was stopped

pending a thorough investigation. A Study for the Dept of Energy and Climate

Change Study resulted in approval on Dec 13th, 2012 for drilling and fracking by

the company Cuadrilla to continue. Future quakes greater than 0.5 will be noted

and the fracturing will be stopped, pending an investigation of the procedure.

References:

1. http://www.eia.gov/analysis/studies/worldshalegas/

2. http://www.netl.doe.gov/technologies/oil-gas/publications/brochures/Shale_Gas_March_2011.pdf

3. http://og.decc.gov.uk/en/olgs/cms/explorationpro/onshore/cuadrilla_decc/cuadrilla_decc.aspx

4. http://og.decc.gov.uk/assets/og/bo/onshore-paper/uk-onshore-shalegas.pdf

Conclusion. Hydraulic fracturing needs water and sand injected at pressures up to 1000 bar.

The resulting cracks are held open by larger sand grains which increase formation permeability.

Shale gas production has been very successful onshore in the USA, and may be found to be

economically viable in the UK. Geologists have said it is probable that the UK has five times

greater reserves of shale gas offshore than onshore. Other countries, e.g. China, Ukraine and

Poland, have vast onshore shale gas reserves and are proceeding with their development.

Cuadrilla’s exploratory fracking site near Blackpool . Photo Phil Heywood The Guardian