Assigment 1 Oilspill Report

8/9/2019 Assigment 1 Oilspill Report

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Thesis statement :

Physical transport, dissolution, emulsification, oxidation, sedimentation, microbial

degradation and aggregation are processes of oil spills in the marine environment.

Objectives:

1. To define what is an offshore blowout.2. To list and explain the different types of blowout and explain how they occur.3. To elucidate the various processes of oil spillage in the marine environment as

outlined in the thesis statement.. To identify laws and regulations for accidental oil spills.!. To list mitigating and recovery measures employed by some companies.

Chapter 1INTRODUCTION


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This pro"ect see#s to probe into the environmental issues associated with the drilling phase

of the oil and gas industry. Petroleum drilling is the primordial step in the success of oilfield

exploration. This success is based, the important details derived from geological formations

and, good reservoir conditions. Thus, the paramount drilling ob"ectives are as follows: to

obtain approval for drilling from all relevant regulatory bodies, reach the target safely in the

shortest possible time and at the lowest possible cost, with re$uired additional sampling and

evaluation constraints dictated by the particular application. %rilling the wellbore is the first

and the most expensive step in the oil and gas industry. &xpenditures for drilling represent

2!' of the total oilfield exploitation cost and are concentrated mostly in exploration and

development of well drilling. (n the 1))*+s, drilling operations represented about 1*.) billion,

compared with !.2 billion - P(, 1))1/, the total cost of 0 petroleum industry exploration

and production - hod"a, et al. 2*11/.

s of conse$uence, the drilling phase is of paramount economic importance in the recovery

of hydrocarbons. il plays a vital role in society, in that its derivatives serves as feedstoc# for

several consumer goods and as such, it has become the most dominant energy source for

man#ind to date.

4ontrary to aforementioned benefits of hydrocarbons, it dispense and sustains a significant

number of ha5ards to our environment and conse$uently endangers the global ecology.

6ithin this context, the most widespread and dangerous conse$uence of the oil and gas

industry activities is pollution. Pollution is associated with virtually all activities throughout the

stages of oil and gas production from exploratory activities to refining. 6astewaters, gas

emissions, solid waste and aerosols generated during drilling, production and refining are

responsible for most of the pollution. ne such pollutant due to human interference is oil

spills. n oil spill happens when li$uid petroleum is released into the environment by vehicle,

vessel or pipeline. (t happens on a large scale and is mostly seen in water bodies. (t

happens due to human negligence and is a ma"or form of pollution. The source of the spillare many. 4rude oil can be released by tan#ers on land. (n water bodies, the spill occurs due

to drilling rigs, offshore oil platforms and wells -%5ulhelmi, 2*1!/. The common denominator

in all of them is that, the damage caused by oil spills is permanent and ta#es a long time to

clean up.

7owever, precautionary conciliatory measures have been underta#en by both governments

and ma"or oil and gas companies to find ways in reducing this phenomena. 6hilst,

simultaneously, see#ing sustainable development for the oil and gas industry. ome of these

measures will be further discussed in this report as mitigation measures that are employed


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by ma"or oil and gas companies, as well as this report will see# to list pertinent laws and

regulations implemented by local and foreign regulating bodies in response to this pervasive

phenomena.

8urthermore, oil and gas ma"or companies such as hell, have implemented the mechanicalcontainment and recovery mechanism as a mitigation measure in response to oil spills.

Thus, scope of this report is to evaluate environmental ha5ards associated with the drilling

phase in the oil and gas industry, focusing on offshore oil spills in the marine environment.

8urthermore, to list laws and regulations that were enacted in response to such occurrences

and provide alternative mitigation measures that can be employed in the oil and gas industry.

Methodology:

This report see#s to address the ha5ards of oil spills, by providing a thorough evaluation of the potential environmental impacts of each ha5ards mentioned in the thesis statement.

8urthermore, to highlight specific laws and regulations that were designed and implemented

by both local and international regulating bodies in response to environmental pollution due

to oil spills. lso, to focus on specific precautionary and mitigation measures that were

developed and enforced to ensure environmental protection whilst bolstering sustainable

development of the oil and gas industry.

The analysis of this report relied principally on second hand information ta#en from varioussources9 such as scientific "ournals, newspapers, and environmental reports from regulating

bodies -.i.e. & , &P etc./. To this end, the general approach was to obtain reliable up;to;

date information on $uantities of oil entering the marine environment from reliable and

reputable sources. This presented a limitation in the methodology, since accessing reputable

data was not a simple tas#. 8or example, few countries had organi5ations with reliable

databases, thus this report relied significantly on data available from roup of &xperts on the cientific spect of arine &nvironmental

Protection 2**?/


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Machinery space discharges4.1.2

4.1.2.2Drillings discharges

Produced water discharges4.1.3

Air emissions (V !s4.1.4 "

Plat#orms

$ells

%&P ' perational4.1

discharges

igs

%&P ' Pipeline discharges4.3

And spillages

%&P) perational discharges &

accidental spills

%&P ' Accidental spillages4.2

4.3.2Accidental releases

perational discharges4.3.1

IV

8igure 1 below shows a general frame wor# for evaluating sources of oil spills from sea

based activities -=oint >roup of &xperts on the cientific spect of arine &nvironmental

Protection 2**?/


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The actual blowout source reservoir is far from the target reservoir

Therefore, if a blowout included one or two of the above characteristics, but in fact had a

deeper depth than 1,2** m -3,)** ft/, it could be classified as a shallow gas blowout.

Ca#ses o% shallo" gas blo"o#t

The li#elihood for losing the primary barriers during operations are discussed in table 2.1.

Table 2.1 list the experiences caused for losing well control. &xperience had showed that

shallow gas blowout fre$uency is approximately 2.3 times higher during exploration drilling

that during development drilling. The listed fre$uencies are based on all the drilled wells, not

only for wells drilled in areas with shallow gas.

Table 2.1 showing barrier failure causes for shallow gas drilling blowouts -7olland 2*11/.

Table 2.1 shows, most primary barrier failures are related to too low hydrostatic head. Poor

cement and formation brea#down were the causes of three other primary barrier failures. 8or

the sa#e of brevity, these reasons were not discussed in depth. Two blowouts caused by

poor cement occurred after the casing operation and during drilling. nly a limited amount of

gas was flowing. 8or the formation brea#down incident, gas was observed at the sea floor

after the A P has been run.


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$"abbing

wabbing is the dominant cause of losing the hydrostatic barrier and hence leading to

shallow gas blowouts. wabbing creates a suction in the wellbore which may induce well

fluids out of the formation, creating a #ic#. wabbing is usually caused by pulling thedrillstring too $uic#ly out of the well. pproximately *' of the shallow gas blowouts in

development wells and 2*' of shallow gas blowouts in exploration wells were caused by

swabbing -7olland 2*11/.

Deep"ater blo"o#ts

The main difference in blowout barriers -when drilling the deeper part of the well compared

to the shallow part/ is usually that two blowout barriers exist during DdeepE drilling. The

primary barrier is the drilling mud, and the secondary barriers are the mechanical devicesdesigned for closing in the well annulus -a A P/ or the drillpipe. 6hen a mechanical barrier

is activated during a #ic# situation, the well pressuri5es. This re$uires that the formation

fracture gradient be sufficiently high so that the pressure can be confined until the

hydrostatic control is regained. (f the formation fracture gradient is too low, an underground

blowout or a blowout outside the casing may result.

Ca#ses o% Deep drilling blo"o#t

This section focuses on the causes of Fdeep+ drilling blowouts. ince barriers normally shouldbe present while drilling, this section is divided into two main parts. The first part covers the

causes of losing the primary barrier, mainly the hydrostatic control of the well. The second

part covers the causes of losing the secondary barriers, mainly the topside barriers.

&oss o% the primary barrier

6hen the primary barrier is lost, a well #ic# results. Table 2.2 lists experienced primary

barrier failure causes for the #ic#s resulting in blowouts.


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Table 2.2 showing Primary barrier failure for deep %rilling blowouts -7olland 2*11/

The relative distribution of causes of losing the primary barrier is rather similar to the shallow

gas blowout as shown in table 1.1. s seen in table 1.2, deep drilling blowouts occur

approximately twice as fre$uently during exploration drilling as during development drilling.

The main reason for losing the primary barrier during DdeepE drilling is that the hydrostatic

pressure becomes too low. (n addition to this, DdeepE drilling blowout was caused by poor

cement, one by a barrier failure in the well test string, and one by a malfunctioning tubing

plug.

The incident listed with poor cement was also listed with too low hydrostatic head as thecause for losing the primary barrier. %uring a cement s$uee5e "ob, gas propagated to a

neighbouring well. poor cement "ob and a failed casing valve in the neighbouring well

caused a blowout through an intermediate or outer annulus. ther factors that could

contribute to a significant reduction of hydrostatic pressure are as follows:

wabbing0nexpected high well pressure@too low mud weight(mproper fill up -similar to swabbing/%rilling into a neighbouring well.


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nnular losses -as causes of the well #ic# were only reported once for deep drilling

blowout.Trapped gas

&oss o% secondary barrier

Table 2.3 shows lists of causes for losing the secondary barrier -7olland 2*11/

s shown in table 2.3, three blowout were listed with string safety valve not available as

the failed secondary barrier. 8or the development drilling blowout this was assumed to

be the caused because, while lowering scarper and mule shoe, the well blew through the

drill stem. 8or one of the exploration drilling blowouts, the elly valve was 3.? m -12 ft/

in the air and could not be closed due to high differential pressure. 8or other explorationwell blowout, the drillstring safety valve could not be closed because coiled tubing was

running through the valve -7olland 2*11/. Two blowouts were listed with failed to stab

Kelly valve as the cause for losing the secondary barrier. (n both incidents, stabbing the

valve against the flow was impossible. ne of these two stabbing attempts was with a

top drive. fter failing to stab, the crew unscrewed one stand at the drill floor and

attempted to stab the elly valve, which also failed. The blind;shear rams were closed to

control the surface flow for both incidents.


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8igure3.1b showing behaviour and fate of oil spills in the marine environment

-%epartment of Pathology ntario Heterinary 4ollege 0niversity of >uelph 1)BB/.


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8igure 3.1c showing general timing of oil weathering process.

(hysical transport )$preading* . The distribution of oil spilled on the sea surface occurs

under the influence of gravitation forces. (t is controlled by oil viscosity and the surface

tension of water. nly ten minutes after a spill of 1 ton of oil, the oil can disperse over a

radius of !* m, forming a slic# 1*;mm thic#. The slic# gets thinner -less than 1 mm/ as oil

continues to spread, covering an area of up to 12 #m2. %uring the first several days after

the spill, a considerable part of oil transforms into the gaseous phase. Aesides volatile

components, the slic# rapidly loses water;soluble hydrocarbons. The the more viscous

fractions ; slow down the slic# spreading - tanislav 2*11/.

il released at or near the sea surface will first be affected by spreading as shown in

figure 3.1c below. (f discharged below the surface, it must rise through the water column

before it can form an oil slic#. 0nder such conditions, oil droplets form and disperse, and

the lower molecular weight components dissolve. 6hen oil is released on the sea

surface, it spreads hori5ontally in an elongated pattern oriented in the direction of the

prevailing wind and surface water currents. The centre of the mas of the slic# may move

at a rate of approximately 3' of wind speed with a 2* to 3* degree shift to the right due

to coreolis force.

Dissol#tion . ost oil components are water;soluble to a certain degree, especially low;

molecular;weight aliphatic and aromatic hydrocarbons. Polar compounds formed as aresult of oxidation of some oil fractions in the marine environment also dissolve in


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seawater. 4ompared with evaporation, dissolution ta#es more time. 7ydrodynamic and

physicochemical conditions in the surface waters strongly affect the rate of the process.

+m#lsi%ication . 6hen oil enters the environment from spills, ruptures, or blowouts itundergoes a continuous series of compositional changes that are the result of a process

#nown as weathering. %uring this physical;chemical process, lighter oil components

photo;oxidi5e to the atmosphere, while heavier oil components typically mix with water to

form a viscous emulsion that is resistant to rapid weathering changes. Thus, it is slower

to degrade, more persistent in the environment than non;emulsified oil, and more li#ely

to enter the water column. The oil emulsion+s viscous character poses a threat to marine

vegetation through covering and smothering surfaces with which it comes in contact. (f

the oil emulsion enters the water column and reaches the benthic 5one, it may cause

permanent damage to root systems, inhibiting the plants+ ability to regenerate.

&mulsified oil cannot effectively be recovered by s#imming technologies or absorbent

booms, chemically dispersed, or burned.

(n addition to emulsification, oil in the >ulf of exico also was dispersed through natural

physical processes, as well as through interactions with chemical compounds. The net

effect of both natural and chemical dispersion was that much of the oil was transformed

into tiny droplets with diameters less than 1** microns. uch droplets face significantflow resistance from the water column in their effort to rise to the surface. They are

trapped in the deep >ulf environment until degraded by bacteria and are more li#ely to

interact with marine life. This dispersed oil is diluted as it moves away from the wellhead.

ome components dissolve into the water column and are available for fairly rapid

biodegradation, while more refractory components are only slowly degraded by

microorganisms. Aecause the concentration of the dispersed oil is far lower than the

concentration of dissolved oxygen in deep >ulf waters, oxygen depletion to levels that

could harm marine fauna have not been observed - tanislav 2*11/.

O,idation . olar radiation acting on oil in the water generates photochemical reactions

which yield new, mostly polar organic compounds. The compounds, although in low

concentrations affect toxicity and behaviour of the spilled oil. The primary mechanism of

photo;degradation is photo;oxygenation yielding such reaction products as peroxides,

aldehydes, #etones, alcohols, and fatty acid which tend to be more water;soluble and

toxic than the un;oxidi5ed parent compounds. The process also yields high molecular

weight by;products that are not soluble in either oil or water -%epartment of Pathology

ntario Heterinary 4ollege 0niversity of >uelph 1)BB/.


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%irect photolysis reactions, not re$uiring molecular oxygen, are $uantitatively the most

important mechanism of light;induced transformation. The tendency toward direct

photolysis increases with increasing molecular weight of polycyclic aromatic

hydrocarbons. 8or example, the half;life of naphthalene -two rings/ in surface fresh water

in sunlight e$uivalent to *I < latitude in mid;summer is ?1 hours, compared to a half;life

of eight hours for phenanthrene -three rings/, and *.! hours for ben5o-a/pyrene -five

rings/. Aecause light intensity decreases rapidly with depth, rate of photolysis of aromatic

hydrocarbons in the water column also decreases with depth.

t high latitudes, the rate of photolysis is greatly diminished due primarily to the reduced

intensity and daily duration of solar irradiance during the winter -see figure 3.2 below/. t

C*I < latitude, there is an approximately ten;fold decrease in the rate of photolysis of

ben5o -a/ pyrene between =une and %ecember. Photolysis rates of some compounds,such as ben5o -b/ thiophene and carba5ole, are more sensitive to light intensity than

others such as ben5 -a/ anthracene and ben5o -a/ pyrene.

8igure 3.2 showing annual variation in half ; life -t !* / of ben5o a pyrene dissolved in near;

surface water at the northern latitudes -%epartment of Pathology ntario Heterinary

4ollege 0niversity of >uelph 1)BB/.


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8igure 3.2 showing annual variation in half ; life -t !* / of ben5o a pyrene dissolved in near;

surface water at the northern latitudes -%epartment of Pathology ntario Heterinary

4ollege 0niversity of >uelph 1)BB/.

$edimentation- 7eavier fractions of oil eventually deposit in bottom sediments andpersist for a long time. edimentation may occur by: 1/ adsorption of droplets on

suspended particles and transport them to the bottom, 2/ stranding or beaching of oil,

followed by adsorption onto sediments or erosion of hardened oil from substrates and

subse$uent transport to subtidal sediments, and 3/ direct sin#ing of heavy or weathered

oils. uspended particles interact with spilled oil in two ways. They physically collide and

adhere to dispersed droplets, and adsorb and partition dissolved hydrocarbons from the

water phase. ma"or variable in adsorption appears to be the concentration of

suspended particulate matter, especially clay, in the water column. The greater thesuspended sediment load, the more oil may be absorbed and transported to the bottom

of the seabed. pproximately 12* to 3** mg of petroleum may adsorb to each #ilogram

of suspended clay -%epartment of Pathology ntario Heterinary 4ollege 0niversity of

>uelph 1)BB/. 6eathered oil may become heavier than seawater and sin#. The process

is enhanced as the density of water is lowered by influx of freshwater as runoff or from

melting ice. (n areas of significant down welling, as in a polyna at the edge of an ice

sheet, sin#ing water may carry oil droplets to the bottom. dditional oil may be fixed onto

biological particles, particularly 5ooplan#ton faecal pellets.

Microbial degradation . arine bacteria and fungi play an important role in degrading

and removing petroleum hydrocarbons from surface slic#s, the water column, and

surficial sediments. icrobial degradation begins a day or so after the spill and continues

as long as hydrocarbons persist. Jate of degradation is related to oxygen concentration,

temperature, nutrients, salinity, the physical state and chemical spill site -%epartment of

Pathology ntario Heterinary 4ollege 0niversity of >uelph 1)BB/.

Aiochemical processes of oil degradation with microorganism participation includeseveral types of en5yme reactions based on oxygenases, dehydrogenases, and

hydrolases. These cause aromatic and aliphatic hydrooxidation, oxidative deamination,

hydrolysis, and other biochemical transformations of the original oil substances and the

intermediate products of their degradation.

8ollowing an oil spill, all hydrocarbon components and classes are degraded

simultaneously, but at widely different rates by indigenous water column and sediment

microbiota. Kow molecular weight n;al#anes in 41* to 422 chain length range are

metaboli5ed more rapidly, followed by iso;al#anes and higher molecular weight n;


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al#anes, olefins, monoaromatics, P 7, and highly condensed cycloal#anes, resins and

asphaltenes. Thus, as oil weathers through a combination of physical, photochemical,

and biodegradative processes, it loses low molecular weight components and becomes

enriched in higher molecular weight more complex saturates, naphtheno;aromatics,

P 7, resins, and asphaltenes.

Temperature significantly affects the process of degradation. The half;life for microbial

degradation of phenanthrene at an initial concentration of 2! Lg@K in seawater is ?) days

at 1B* 4 and 11,*** days at 2 * 4. imilarly, that for ben5 -a/ anthracene at an initial

concentration of 2.! mg@#g in sediment is 11** days at 1! * 4 and 21,*** days at * 4.

The reliance on temperature was postulated by 6a#eha et al -1)B!, 1)BC/ who showed

that in summer conditions biodegradation was more important that volatili5ation in

removing toluene, octadecane, and decane from the water column9 under winter conditions, their contributions were reversed. Aecause both processes are mar#edly

diminished at low environmental temperatures, the light fractions of crude and refined

petroleum are very persistent in the rctic environments, especially winter when low light

intensity inhibits photo;oxidation -%epartment of Pathology ntario Heterinary 4ollege

0niversity of >uelph 1)BB/. &ven though biodegradation is a relatively slow process, it is

more sluggish in winter conditions than in summer.

.ggregation . il aggregates in the form of petroleum lumps, tar balls, or pelagic tar can

be presently found both in the open and coastal waters as well as on the beaches. They

derive from crude oil after the evaporation and dissolution of its relatively light fractions,

emulsification of oil residuals, and chemical and microbial transformation. The chemical

composition of oil aggregates is rather changeable. 7owever, most often, its base

includes asphaltenes -up to !*'/ and high;molecular;weight compounds of the heavy

fractions of the oil.


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Chapter /

&a"s and reg#lations

The following are a list treaties that are adopted by Trinidad and Tobago from the rthur

Kittle (nternational (nc. 2*** with regards to protecting the environment from oil spills:

4onvention on


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Alowout preventers were designed and tested to withstand the maximum expected pressure.

They activate automatically in the event of a power failure on a drilling platform.

Recovery meas#res:

echanical containment and recovery. (f a spill does occur, the rapid containment andrecovery of oil at or near the source is the first goal. echanical s#immers can be used to

remove oil from the water surface and transfer it to a storage vessel. #immers wor# most

efficiently on thic# oil slic#s: floating barriers, #nown as oil booms, are used to collect and

contain spilled oil into a thic#er layer. variety of designs for s#immer and booms have been

adapted for rctic sea conditions and several have been proven to wor# well.

4apping and 4ontainment dome. hell has commissioned the building of a subsea

containment system that involves capturing and recovering hydrocarbons at source in theunli#ely event of a well control incident in the shallow waters off las#a. This recovery

method has proved effective in shallow water. The containment system is designed to

capture and recover oil and gas from an undersea well in the event of failure by the blowout

preventer. The recovered oil would be transferred to a surface processing facility for

separation of oil, gas, and water - hell 4ompany (nc 2*11/.

Concl#sion:

The discovery of hydrocarbons has in no doubt improve the standard of living for man#indexponentially, as a result of this, hydrocarbons is still the dominant source of energy.

8urthermore, at present it is the most sort after source of energy, because of its intrinsic

economic value. (n addition, even though other alternative energy sources are emerging, at

present they cannot meet the world+s demand for energy. Thus, it is predicted that the

demand for hydrocarbons will still dominate for at least fifty more years.

7owever, amid of these benefits, hydrocarbons have simultaneously and progressively

contribute significantly to adverse weather patterns such as global warming. oreover,

offshore oil spills generated from oil rig blowouts poses imminent threat to the marine

ecosystem. s such, international treaties and regulating bodies have enacted laws and

regulations to prevent and mitigate the impact of this phenomena on the marine habitat.

To ensure that ma"or companies are held responsible for their offshore operations, it is

recommended, that regular audits and inspections should be performed by the appropriate

regulating bodies to ensure adherence to the law.


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+i,liographyDepartment o# Pathology ntario Veterinary !ollege -ni ersity o# /uelph. 10 .

Synthesis of E ects of oil on Marine Mammals. Ventura) Department o#Interior Minerals Management cience.

olland Per. 2511. O shore blowouts.Causes and control. ouston) /ul#Pu,lishing !ompany.

6oint /roup o# %7perts on the cienti8c Aspect o# Marine %n ironmentalProtection. 2559. Estimates of Oil entering the marine environment. :ondon) International Maritime rgani;ation.

a ) !ascio.

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Assigment 1 Oilspill Report