Topic 49: Safety issues during drilling operations.

Sergios has made a good start with some of the problems encountered during drilling operation. He has highlighted some of the functions/properties of a drilling mud. I will like to point out some challenges that can be encountered during drilling operation. They are as follows:

• Encountering Shallow Gas Formation can lead to a blowout if uncontrolled.
• Hydrocarbon in the well during drilling: This can lead to a blowout if uncontrolled.
• Hydrocarbon in the well during Coiled tubing operation: This can also lead to a blowout if uncontrolled.
• Encountering an unconsolidated formation (sand) during drilling can cause loss in mud circulation.
• Entrained gas escaping from well into the mud system and shakerhouse.

All these challenges mentioned above if uncontrolled will lead to a blowout.

Some of these safety issues can be tackled through

• Intensive training/ mentoring by competent personnel
• Ensuring the availability of detailed geological and seismic information
• Ensuring the availability of information from offset wells
• Drill the Well On Paper (DWOP) before arriving at the drilling location

Chukwumaijem M Ejimuda

MSC Safety and Reliability Engineering.

Initially I would like to challenge Sergios as mud isn’t really the safety tool, it is the key component for continuing drilling and maintaining cost effective use of time and drill bits. Kill Mud, (mud of a heavy weight) is the safety tool fluid wise, with the utilisation of this and the drilling package, diverter, flare, shale shakers, degasser are all the components required to save lives during an influx. Finally Chuma has defined some of the main threats of a MAH and the mitigations against these threats excellently, I would like to add to his list Human error in drilling, as shown in Macondo, as the key threat to during any drilling as even with the best mud loggers and equipment onboard the human element can still fail.

Dear Colleague,

Regarding Neil claim on his post, as mud cooler engineer for about a year with 6 to 7 offshore operation involvement, I learnt a lot about mud. Mud in fact is used not only to what had pointed out (by Neil and Ejimuda) but also as a safety measure (as to Sergious mentioned), as the mud circulated into the borehole density’s is carefully regulated to exert downward pressure greater than the upward pressure from the formation fluid. 

“Mud may represent 5% to 15% of the total cost but may cause 100% of the problem” [1].

Thus, is is crucial to design mud program that will do as intended and keeping the property constant during drilling. Following are the outline proposed by Schlumberger [1]: 

1. Rheology : to design mud viscosity that not to low as not doing its intended function but not to high to cause friction that will affect the mud circulation.

2. Density    : Density of mud that will prevent caving and keep formation fluid ingressing but not to high to reduce the ROP. 

3. Fluid Loss : Low permeability mud that act as filler to seal between wellbore and formation reducing differential sticking that may damage the formation.

4. Solid contents: Well balanced barite or other weighting agents that will perform its function it transporting cutting from bottomhole yet not to high to act as abrasive and eroding equipments.

5. Mud Properties: Mud shall be designed to anticipate the formation properties to mitigate any adverse reaction from the formation properties and vice-versa.

These may be achieved by looking into the mud ingredient:

1. Weighting agents—such as barite.
2. Clay— Such as bentonite 
3. Polymers—Such as Cellulosic, polyacrylic and natural gum polymers 
4. Thinners—Such as plant tannins, polyphosphates, lignitic materials, lignosulfonates or synhetic polymers.
5. Surfactants
6. Inorganic chemicals—Such as calcium hydroxide, calcium chloride,  sodium hydroxide and potassium hydroxide.
7. Bridging materials—Such as Calcium carbonate, cellulose fibers, asphalts and gilsonites.
8. Lost circulation materials—Such as walnut shells, mica and mud pills containing high concentrations of xanthum and modified cellulose.
9. Specialized chemicals—Scavengers of oxygen, carbon dioxide or hydrogen sulfide are sometimes required, as are biocides and corrosion inhibitors.

In conclusion, its hard to generalize the mud program as different section from a well may have different formation properties and have their own personality [2], let alone from one well to other well.

References:

1. Bloys, B., Davis, N., Smolen, B., Bailey, L., Fraser, L. & Hodder, M. (1994). Designing and managing drilling fluids. Schlumberger Oilfield Review. Vol 6, Issue 2.

http://www.slb.com/~/media/Files/resources/oilfield_review/ors94/0494/p33_43.ashx

2. Graham, B., Reilly, W.K., etc . (2011). The Gulf Disaster ad the Future of Offshore Drilling. Report to the President : National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling. http://www.oilspillcommission.gov/sites/default/files/documents/DEEPWATER_ReporttothePresident_FINAL.pdf 

Dear Anasabdrahman, 

Like Neil just pointed out in his latest post, you have elaborated on the properties of drilling mud but not on the safety of the drilling operation. I want to make one thing clear that without a good mud program, drilling operation will not even commence in the first place but like Neil and I mentioned in our previous posts, are some of the challenges encountered during drilling operation. 

To add to what has been said previously, good well planning and program (which includes the mud program), avoiding human error, reviewing well plan for each section, ensuring mud logger's equipment is safe to act as redundancy, and finally carrying out periodic planned maintenance on safety critical elements. 

I believe these are some of steps to keep a safe drilling operation.

Chukwumaijem M Ejimuda

MSC Safety and Reliability Engineering.

The contaminants during normal
drilling operations mainly include:

1)   
Exhaust. In the drilling phase,
the major contaminants are NOx, CO, CnHm and in the blowdown phase, the major
contaminants contain SO2 and H2S.

2)   
Waste water. It is usually
generated in the cleaning process of drilling platforms and rigs, which is
pretty low quality including COD, SS and petroleum, etc.

3)   
Solid waste. It includes
surplus mud and drilling cuttings.

4)   
Noise. The drilling rigs are
normally high power equipment such as mud pump, diesel engines and so forth
which could cause noise above 100dB.

During drilling
operation, the following major environmental risks exist: 1) Accident blowdown;
2) Uncontrolled blowout; 3) Leakage or collapse of waste water pond; 4)
Contamination of solid waste; 5) Thermal radiation.

In some cases, when there are no uniform well design, the safety measures must be more focussed. It is important that it should have enough measures to prevent a blowout. The first measure is to include heavy fluids that exert a downward pressure which helps prevent blowout. The second measure is to cementplugs and rubber and metal seals which act as a mechanical barrier. If both of these fail, the final method used is the Blow out preventer which seals of the well.

One method which one can use is the Drill On Paper for a safer operation. In this method, the drilling contractors and other operation experts evaluate the conditions and predict whether the well design, the drilling method used and the safety measures adopted are fine enough for the operation. The method also makes sure that every personnel on the rig is completely aware about his duty. By this evaluation, the drilling can be operated safely.

Sreehari Ramachandra Prabhu

One of the major causes of most drilling incidents is human failure. It has been found out that the intervention of Human Factors techniques will reduce the incidence of induced kicks, near misses, lost time incidents and accidents in drilling to some degree. Technological experience and competence is on the high side in recent years hence human factor has to be put into consideration when a change in technology occurs.
The science of human factors is a new field which should be studied. It is only concerned about maintaining a balance between technology and the environment to the capacities and limitations of humans. Human Factor techniques/tools are normally applied to assess behaviours, robustness of working practices and perceptions of safety in drilling.
Some examples of Human Factors tools that could be applied in assessing safety in drilling operations include:
1) Safety Culture Questionnaire (SCQ) which was developed specifically for this project
2) Systematic Human Error Reduction and Prediction Approach (SHERPA)
3) Hierarchical Task Analysis (HTA)
4) Individual Interviews and Focus Group meetings with 86 drilling personnel, on and off the rigs.
5) Sequential Timed Event Plotting Procedure (STEPP)
By actually applying these techniques we can pin point our current position, learn from past occurrence and predicts what the future holds for safety in drilling operation.

Reference
Wilson J A and Stanton N A ”Safety and performance enhancement in drilling operations by human factors intervention” 2001. ISBN 0 7176 2909 0

Reg no: 51231595
Name: Alabi Ochu Abdulraheem

I looked through the opinions posted by my classmates, and found many different views are based on the mud safety. Personally, I think a proporiate mud is not a fluid only used in killing wells, but also has many functions during drilling, like keeping reservoirs undamaged. The main hazards during drilling and completion can be summarized into two aspects: management and technology.

For the managment, it includes the equipment managment, contractor management and operation management. Well equipment maintenance is essential for drilling, especially for offshore due to its high risk and cost. Any failure of equipment like the rig, casing, or anchors of jackup could lead to the disaster. The failure of BOP in the deepwater horizon accident is a paradigm. Meanwhile, contractor management is a challenge for operators when drilling. Poor communication and chaos between operator and contractor could significantly trigger accident. Finally, any operation sacrificing safety to save the cost or shorten the schedule is one of the hazard sources, like the deepwater horizon accident.

Moreover, the technology unmatched with the drilling formation is another safety risk. Providing the targetted reservoir has high temperature and high pressure, inappropriate drilling mud or drilling process could damage the formation, and cause low hydrocarbons output or accident.

As rocks is heterogenous and drilling formation is always unpredictable, advanced technolgoy and well established drilling regulation are necessary. The future challenge is unknow, but we can do more and better in safety managment to reduce the risk.       

Thank you for your response Neil and Ejimuda.

I do agree with the points put forth. In my previous post, I tried to point out that the mud program is the first line of defense and proper design should be considered. There’s a lot other factor contributing to safety of drilling operation, consider the following points: as per Shell Drilling safety manual [1]:

1. Drilling Management System: Where we define role of each personnel and responsibilities, Hazards and effects managements process, planning procedures and lot more
2. Adequate preparation such as site prep, material procured (right tool for the right job) etc
3. Equipment : Maintenance work, equipment in hazardous environment, drilling equipment (Drawwork, pulse dampener for top drive, safety relieve valves ), BOP
4. Operation : Tubular, casing, chemical (Mud, Completion chem, oxy-aset gas etc), H2S danger.

Each of above mention will contribute to safety in drilling. For instant in the wake of Macondo we see the drilling management system failed where the driller wrongly interpret the 1400psi difference between pressure in drill string and kill line. Than we witnessed the failed equipment and system where the BOP doesn’t function as anticipated. Emergency Disconnect System (EDS) also failed but if you go through the report you will find yourself at first of the well kick, the immediate realization was when the mud spewing out from the well onto the rig, than they know that they have a well kick [2].

Meanwhile from International Association of Drilling Contractors, we know that most of problems like differential sticking of drill pipe, gas cutting, formation gas or water influx, and many more wellbore problems can be detected and/or corrected by adjusting the mud properties [ref 3 : section O]. Thus, showing, mud plays to me the significant role in success of a drilling as mention in the IADC drilling manual.

References:

1.Shell HSE. (1995). Drilling Manual. Shell International Exploration and Production B.V.

Available from:

http://www.caldenergine.com/Safety%20in%20Drilling%20Manual.pdf

[Accessed on 30 NOvember 2012]

2. Graham, B., Reilly, W.K., etc . (2011). The Gulf Disaster ad the Future of Offshore Drilling. Report to the President : National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling. http://www.oilspillcommission.gov/sites/default/files/documents/DEEPWATER_ReporttothePresident_FINAL.pdf 

3. 1991-92 Rewrite Subcommittee. (2000). Drilling Manual. International Association of Drilling Contractors. Technical Toolboxes, Inc. Texas. Ver 11th.

In line with anasabdrahman I would like to add some more point hazards and potential risk on drilling operation associated with depth and formation temperature and pressure since deep drilling is more complicated as compare to shallow also offshore drilling operation are more critical than onshore   but main aim is to prevent incident/accidents free operation and to achieve this a lot of technologies are used to control, maintain and monitor each activity and by Proper planning, construction and safe operation are all carried out by specially trained and qualified personnel  to mitigate the impact which  Drilling operations
 For Designing phase before operation all calculation made earlier in designing phase like  Hazop, Hazid, BOP's there are a lot of challenges as rocks are heterogeneous and unpredictable very careful operation is needed specially dealing with Drilling mud, cementing and blow out preventer
For operation the important factor is drilling fluid there are five basic properties of drilling fluid which can be monitored during drilling: Rheology, Density, Fluid Loss, solid content and chemical properties
Mud ingredients properties its own characteristics which choose by formation and depth of ore hole
The first concern should be the employees’ safety before productivity as a single mistake may cause explosion or fire and to ensure safety proper training to individual is also important for safe operation

Faiza Khatri
M.Sc Oil and Gas engineering

Oil and Gas companies spend about $20billion in annually on drilling. Unfortunately not all of the money is well spent. A common  slogan says " STEP BACK 5 BY 5 BEFORE EXECUTING THAT JOB". Lots of risk and danger in the drilling rig. Proper analysis of the job prior to execution could eliminate some risk and reduce the impact of the risk if they were to happen.

Oil drillers work under dangerous conditions. The platform and equipment they work with are normally slippery. The drilling causes vibration and noise. Pipes can move and fall. Tools drop. High-pressure hose connections can fail and whip about, striking workers. There's also a risk of falling when climbing the rig and derrick.

A number of chemicals and unhealthy materials that are present while drilling for oil. These include crude oil, hydrogen sulfide gas (H2S), asbestos, formaldehyde, hydrochloric acid, benzene and heavy metals. Drilling for oil can also produce radioactive waste. This happens when naturally radioactive materials like stones or soil are brought to the surface during the drilling process.

There's always a risk that the pressure control systems will fail and there will be an uncontrolled release of oil. This is known as a "blowout"; if it's not controlled, a well blowout can catch on fire and cause a personnel on the rig dead.

Samuel Kanu

Msc Subsea Engineering

Reference

1.)www.intertek.com/oil-and-gas/offshore-​hazard-risk-assessment

2.) http://www.ehow.com/list_7528914_hazards-drilling-crude-oil.html

Drilling or rotary drilling as it
is sometimes called involves the boring of holes in to the earth crust. This technique
started with the continuous dropping of a long cylindrical pipe or wood (bamboo)
with a sharply pointed bit attached to the end. It was said to have been used
for the first time in 1895 and it became dominant in the 1950's. Due to
technological advancements, drilling operations have moved from the ordinary
boring of vertical wells to horizontal wells (directional drilling), different
during methods like underbalanced drilling, coiled tubing drilling etc

Over the years, during drilling operations
several problems like influx of formation fluid which leads to blowout of the
well if not properly controlled, fishing (i.e. the detachment of the drill
collar from the drill string), poor cementing jobs, drilling into high pressure
high temperature formations etc. The problems encountered are as a result of
lack of data, knowledge and experience of drillers. Since the formations and
rocks drilled into before getting into underground reservoirs are very
unpredictable, regulations and safety measures should be put in place to avert
or reduce to the minimum  the probability
of any accident or mishap happening.

REFERENCES

1)2007, James A. Craig, Drilling Engineering I

2)2009, James A. Craig, Drilling Engineering II

3) www.wikipedia.org

The reason of accident could be classified into two factors.

1. Geologic Factor. At first, we should know pore pressure, breakdown pressure, caving pressure and creep stress of some special formation as important data in well configuration and drilling mud designing. And then, for some special beds like rock salt, evaporate, brea, mudstone, coal and igneous should be learn, because those beds are the birthplace of borehole problem.

2. Engineering Factor. Incomplete, inaccurate geological data or imprecise well design make blowing beds and leaking beds appeared in one naked hole. Treat blowing, then leaking. Treat leaking, then blowing. Ignoring the rule, forgetting the gauge, pull too fast during trip up, press too hard during going down and drill while sticking, those are common cause of borehole problem.

Duo Wu  51230750 

Drilling risers are very dynamic and complex structures that are subject to a range of often extreme environmental and operational effects and forces. Therefore, instruments which monitor drilling risers are used in an effort to maintain their operational integrity. However, despite their important job and even with the substantial consequences of a riser failure there has been some opposition to the idea of monitoring them. Monitoring packages can often be cited as impractical, insufficiently robust and costly.

However, in my opinion they are very important and more research should be done into improving and scaling down the packages so they can be integrated effectively. For example a platform in shallow waters in the Norwegian sector of the North Sea can be subject to all manner of surface (waves) and subsea currents. In shallow water, any motion of the rig results in large angular deflections of the riser; this, in combination with the possibility of wave patterns matching the natural frequency of the riser, raises concerns that the fatigue life of the structure could be dramatically reduced. In this situation the operator needs to fully understand the stresses placed on the riser and enable them to act accordingly before the forces become too great and it fails.

Well kick is an uncontrolled flow of reservoir fluids into the wellbore, and sometimes catastrophically to the surface we call it blow out. Once blow out went wild, it can cause serious result. In addition to resource waste and environment pollution, it may made equipment damage, casualties and well abandonment. What even worse is it may cause fire.

Reasons:
1. Inaccurate data of formation data.
2. Low density of drilling mud.
3. Liquid head of drilling mud decreasing.
4. Swabbing while pulling out.

Lost circulation is the reduced or total absence of fluid flow up the annulus when fluid is pumped through the drillstring. It's a common and serious problem of borehole while drilling. It always decrease subsurface pressure in borehole and cause borehole wall sloughing or blow out.

Reason: Lost circulation happen when drilling mud liquid column pressure higher than formation fracture pressure. One of the factors causing lost circulation is abnormal low pressure of formation breakdown, high porosity or high permeability of formation. Another reason may be wrong operation in drilling like too high density of drilling mud or pumping too fast bit going down too fast.

Lost circulation may happened in formations below:
1. loose or high permeability formation
2. natural fissured formation
3. induced fissured formation
4. cavernous formation

Duo Wu  51230750 

Drilling an oil well from the Beginning to completion is a risky process and as such proper care must be taken to protect both the Employees and the Environment. 

When drilling a well there is the Risk of Kicks which if Proper care is not taken will result in a blowout. While drilling the well the Mud Engineer and the mud logger must take proper readings to enable them know when there is need to increase the weight of the Mud ( Drilling Fluid ) to avoid Kicks. The last Safety barrier in drilling which is the Blow Out Preventer should always be in place and the drilling company should ensure it is 100% Functional. Only trained and Professional personnel should be allowed to carry out sensitive operations in the drilling Rig.

The environment should be well protected from pollutions from the drilling operations; this should be done by not disposing drilling fluids directly to the environment without treatment. After drilling the through the Water aquifer, the zone should be cased and cemented before the drilling of the next session begins and this session should always be drilled with water based mud, this will actually help in preventing the drinking water aquifer from been polluted.  

As my colleagues have already outlined, there are many factors that could potentially cause failure during drilling operations. some of them involve the quality of the fluid used in the drilling operations and others involve the how the operations are conducted.

One of the things that should be avoided during drilling operations is a 'KICK'. According to the  Schlumberger oilfield glossary, "The kick is physically caused by the pressure in the wellbore being less than that of the formation fluids, thus causing flow. ". It is caused either by the mud weight being too low than the hydrostatic pressure exerted on the formation by the fluid column or if the drilled formation has higher pressure than anticipated. [1] . This is very serious because it can result in blowouts if not handled properly.

Infact a blowout resulting from a kick  can cause serious injuries and fatalities to personnel handling the operations. It also has alot of environmental consequences associated with it. However, this risk can be prevented by using a closed loop system[2] or acquiring reliable downhole data that can detect the occurance of high pressures. Once high pressures are detected, there should be appropriate quick response mechanisms to contain the situation.

References

[1]http://www.glossary.oilfield.slb.com/Display.cfm?Term=kick

[2]http://www.drillingcontractor.org/safe-drilling-operations-come-full-cir...

One of the main safety issue faced during drilling is blowout. During blowout hydrocarbon will reach the surface in an uncontrolled manner during drilling operation. There are many effective methods to prevent and control this flow of hydrocarbon. The safety technologies used during drilling operation are, drilling mud, the blow-out preventer, cementing.

Drilling mud is used to control the uncontrolled flow of oil and gas from the well. This is done by injecting mud to the well in a closed circuit. The specific gravity of the drilling mud is calculated with respect to the pore pressure. The hydrostatic pressure produced by injecting the mud will control the formation pressure and prevent the hydrocarbon leakage. Blow-out preventer is an important safety device which is installed at the wellhead. It contains many independently operating shutoff valves. This device helps to seal the well completely during an emergency. Blow-out peventer can operate manually and automatically. Proper cementing is needed to ensure the sae of the borehole. It stabilises and seals the casing sections.

 References

http://www.rwe.com/web/cms/en/614746/rwe-dea/corporate-responsibility/safety-the-environment/safety-during-drilling-operations/

A lot of interesting points made above about the risks faced during the drilling operations, in this post I will talk briefly about  five recommended practices to minimise the risk of losing well control during drilling/workover/intervention operations :

1) Barrier Philosophy : the minimum number and type of barriers to well flow, prior to BOP or Xmas Tree removal for drilling or workover/completion operations should be three barriers : 2 mechanical barriers (as downhole plugs for example)  and 1 hydrostatic barrier (drilling mud / completion brine/kill fluid ). But this is dependent on the  Company policy and the Regulatory body  policy

2) BOP testing: BOP equipment should be tested  at intervals not exceeding 3 weeks ( less when required by the regulatory bodies)

3) Hydrostatic pressure maintenance: Reliable , well flow monitoring practices should be used specially when conducting the cemeting operations

 4) Trip Monitoring: Effective use should be made of mud/trip monitoring equipment with use of appropriate alarms

5) Pressure Management : At all times while shut-in on a kick without circulation, the wellbore pressure should be managed to avoid weak point break down .

Differential sticking is a condition whereby the drillstring cannot be moved (rotated or reciprocated) along the axis of the wellbore. It is important to note that the sticking force is a product of the differential pressure between the wellbore and the reservoir and the area that the differential pressure is acting upon. There are several kinds of sticking and differential sticking is the simplest one. If differential sticking was ignored, other kinds of sticking will happen. So, some appropriate measures should be taken if differential sticking happened in order to avoid combined type sticking which is more difficult to deal with.

Duo Wu  51230750 

1. Differential sticking happen when drilling string in the state of static. Because of that, the vertical and rotary action before sticking won't have additional resistance. For the problem of how long in static states before sticking, that depends on the system, property and drilling string composition of drilling mud. Generally speaking, as short as two or three minutes, dozens minutes at longest. Anyway, after a stay of static at least.
2. Freeze point won't be the bit but drill collar and drill pipe.
3. No sticking, no changes in pumping pressure, balance in import and export flow rate.

Duo Wu  51230750

When sticking happen, the first thing to be considered is to create the conditions for solves the accident easily:

1. Maintain the flow circulation of drilling fluid smoothly. We need to prevent bit port and annulus space from blocking, because it is impossible to inject pipe freezing concentrate if the circulation didn't work. In addition, it will induce the formation of borehole collapse and bridge plug easily. Furthermore, it'll be hard to locate string shot to desired position though the nozzle.

Junks are metal debris lost in a hole. Junk may be a lost bit, pieces of a bit, pieces of pipe, wrenches, or any relatively small object that impedes drilling or completion and must be fished out of the hole. Some of those objects fall to the bottom and block drilling; some of them fall to the position upon the bit or centralizer and became the chief criminal of sticking; some of them fall to the middle of the borehole and block the drilling path. In summary, junk falling is a serious safety problem in drilling operations.

Duo Wu 51230750

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Drilling
operations are carried out in tough and rugged environments, and these
challenges bring safety risk to both the human personnel carrying the
operations and the environment in which the operations are carried out. There
have been various accidents in the industry to show the safety concerns in the
drilling operations. One of the major safety issues in drilling today is
compliance to safety regulation and procedures. Several E&P companies have
come up with programs to ensure adherence to procedures and guidelines during
drilling. Another safety concern is the young generation of personnel coming through
the oil industry. They serve as potential risk to accidents on the rig during
drilling operations. Another safety issue is complacency and refusal to change
to new ideas on safety and the way drilling operations are carried out.

Uhunoma Osaigbovo

Subsea Engineering D/L

Drilling operation is an operation that has a high risk associated with it. There are many safety issues associated with drilling. Some of the risks are discussed in this post.
One of the safety issues is the uncertainty associated with the knowledge of what to expect under the earth surface. There are seismic surveys that attempt to predict what the nature of the earth crust is but the predictions of the surveys are largely approximations. So in drilling there is the chance of encountering unexpected scenarios, some of which can be dangerous.
Another issue of concern to safety is the integrity of the well cement. The cement used in casing the well can get damaged and this can lead to loss of drilling fluid from the well bore into the formation. As the well gets to zones of high pressure and temperature, if the pressure of the formation exceeds the pressure of the mud in the well bore there will be a blowout which can cause serious damage.  Also the casing help protect the underground water from pollution. If the casing is damage, there can be pollution of underground water and this might eventually end up in the houses of people and cause injury to health.

Drilling operations can be considered as an area of high potential risk due to the nature of the operations. The main hazards in drilling operations are related to loss of well stability which could lead to a catastrophic or loss of well control. This event can result in hydrocarbons (gas or oil) or other toxic substances (H2S, C02) reaching the surface in an uncontrolled manner.

There are other risks or issues associated to this type of operations such as: operation of heavy equipment, high pressure fluids handling, chemicals usage, manual handling, which being considered minor in relation to the main risk mentioned above, deserve further consideration as they are considerate in other process installations.

The main hazards associated to loss of well control can be geological, mechanical or related to human factors. Therefore the main focus on drilling operations starts with the understanding of the risk scenarios, implementation of best practices, mitigation plans and technologies and the use of competent personnel. This added to implementation of data gathering and analysis can mitigate any risks presents in the operation.

Implementation of best drilling practices and industry standards for well control are really important to this operation. Those best drilling practices are included in the three following components which allow ensuring well control: the design and use of the right drilling mud, the use of the right blow out preventers for that particular well and the design of the cement. Those three components maintain the well isolated from surface while drilling.

Most of the main caused for major accident in drilling installations have been due to failing to design, use and operate those three components. A very particular example is the Macondo well.

A lot of things can go wrong while drilling a well. Some of the drilling problems include;

• Fish/junk- During drilling, a component of the drill string can get stuck or even break and remains in the well bore. This stucked or broken tool is known as a fish or junk. Special 'fishing' tools are used to remove the junk or fish downhole.
• lost circulation - This is a serious problem that can be encountered when drilling a well. Where the permeability and porosity of the formation being drilled into is very high, the drilling mud flows into the formation without formation a filter cake and also the hydrostatic pressure will be reduced thus allowing an influx of gas or fluid from the formation which may lead to a kick or blow out
• Blow out - This is basically an uncontrolled flow of reservoir fluid into the well bore. It occurs when an over pressured zone is drilled into. The overbalance is lost and drilling mud alongside the reservoir fluid flows to the surface. this is known as a kick. if not properly controlled, will lead to a blow out which is very disastrous as can cause a fire breakout and destroy the drillling rig.

References

1. http://www.petrostrategies.org/Learning_Center/drilling_operations.htm

2. http://www.lloydminsterheavyoil.com/drilling.htm

1.Bit bouncing will happen if it has junks in borehole, drilling pressure increase along with the size of junks in borehole. Pull the bit out of the hole and check the attrition rate of bit.

2.Bit bouncing will happen if the size of junks were small enough like cutter tooth of gear wheel, but the bit will has a great abrasion, especially the PDC bit. Pull the bit out of the hole and check whether it has abrasion or not on the bottom of collar and connection end.

3.If junk fall into the position where has small radius, sticking maybe happened. If junk just fall into the position upon the bit, rising up the bit has resistance but pulling down doesn't. In this case, junk in the borehole always fall from sidewall like gravel or cement.

 Duo Wu  51230750 

During drilling, it is important that hydrocarbons don't get to the surface in an uncontrolled manner. An article I read pointed out three components that could ensure this doesn't happen. They include:
 Drilling mud
 Blowout preventer (BOP)
 Cementing
Drilling mud is continually being injected into the well in a closed loop during drilling operations and this provides the primary form of prevention against reservoir fluids flowing into the well bore. The injected drilling mud bears with it a pressure it exacts on the walls of the borehole which helps in maintaining the pressure gradient from the formation to the wellbore thus decreasing the natural tendency of fluids to flow into the well. Specific detail and careful attention has to be given to the properties of the mud particularly its specific gravity to ensure it is capable of preventing hydrocarbon leakage.
Blow out preventers has been identified to be the most important form of safety during drilling operations. Placed directly at the well heads, it consists of various valves designed to shut off fluid flowing out of the well head in different manners. Many accidents during drilling arose from faulty BOP's. Therefore, to ensure complete safety during drilling, it is mandatory to perform regular BOP checks e.g. pressure tests, amongst others.
Lastly, a competent cementing of the casing string adds to the structural integrity of the wellbore. It isolates and provides a "tear-proof" connection to the surrounding loose rock that is impermeable to gas and fluids. This aids in preventing uncontrollable rise of Hydrocarbon fluids outside the casing as well as damage and corrosion.
These three systems working together could substantially mitigate and remedy risks involved in drilling operations.
References:
http://www.rwe.com/web/cms/en/614746/rwe-dea/corporate-responsibility/sa...
Kuma Mede
51126022

Topic 49: Safety during drilling operations

As we know that the drilling has been entered into the third process. At this time, we alway use the fracture to drilling.

In the process, we always use the liquid pressure or the air pressure. That may lead to a earthquick in the nearby area. But recently, people have developed such process as a long distance control to decrease the risk during drilling and also it may reduce the working strength.

In my opinion, what we need to do is as followed:

1) to establish the the Drilling HSE risk prevention security system and operational mechanism that ensure the implementation of the risk reduction measures;
(2) organizations implement risk prevention and reduction measures the necessary human, financial, equipment and other necessary conditions and means, and to develop the configuration and procurement plans for the protection of equipment, tools;
(3) to identify drilling activities HSE risk that may arise in the construction work of the various stages and processes for the prevention and reduction measures;
(4) the development of emergency response plans to reduce the impact of drilling operations in a variety of dangers and hazards occur;
(5) drilling safety production management measures should be documented to provide that the form of a system and the regulations issued guidance drilling safety production.

Zhang Yanan

ID: 51233945 

MSC IN OIL AND GAS ENGINEERING
UNIVERSITY OF ABERDEEN

One of the major challenges
encountered in drilling is primary well control and to overcome this, the mud used
must provide an over balance that will keep the formation fluid in place so as
to avoid blow out which leads to loss of lives and properties. The well must
therefore be full of mud at all time.  This
mud must possess a good rheology enough to provide hydraulic casing for
well-bore stability and to avoid differential sticking which is a nightmare for
drillers. Some other situation to be avoided while drilling is excessive weight
on bit to avoid buckling the drill string. While in drilling an over pressurized
formation, one must reduce the rate of penetration and if total losses is encountered,
the concept of blind drilling must be adapted (drilling without returns but water
is being pumped to keep the well full)
In case of horizontal and high deviated well, one must avoid dogleg severity or
else you get a key seat which will make it impossible to trip out, thereby getting
all the equipment stuck.

Safety is the very foundation of every drilling operation. Safety issues with drilling operation are caused by the following activities:
1The cyclic nature of drilling is impacting safety. Using poorly trained workers with low motivation and experience to execute drilling projects constitute to this.
2 Site leaders: Communication between the well team leader and well site leader is critical as the breach in communication between them would impact on the drilling operation.
3 Inconsistency of Risk Assessment, risk assessment in drilling operation is the most powerful tool used for guiding decision making, safety standards and procedures and the physical work environment. The failure of this event would the probability that the following would occur;
a. Lost circulation
b. Kick
c. Blowout
The consequence would be the loss of life and properties when risk assessment in drilling operation is inconsistently applied and poorly appreciated and understood.
4 Inconsistency of Physical work: if the standard of the physical work environment is inconsistent, the hazard rates in drilling operation would be high.
Mitigating the threats raised by inadequate safety practises in drilling operation includes;
Installation of BOPs during drilling operation
Designing and retrofitting the rig and equipment to eliminate hazards.
Constant risk assessment should be performed to increase the SIL level of the equipments.
Training the personnel before bring them on board/platform for drilling
I recommend that safety standards and procedures should be in forefront of any drilling operation.

Undeniably, the drilling fluid plays a key role in all deepwater drilling operations. Too often, failure to adequately address mud-related concerns can lead to excessive well costs, unscheduled trouble time, unnecessary high-risk activities, and poor performance. In some cases, the challenging deepwater environment is the primary cause of mud-related problems. In others, the mud is the problem source in the sensitive and often unforgiving setting. Regardless, the concerns are real and potentially serious.

Review of deepwater experience in the Gulf of Mexico (GoM), offshore West Africa, Southeast Asia, and Brazil helped identify the most critical mud-related concerns. Those selected for this top-10 list are

1. Lost circulation,
2. Mud properties (density and rheology),
3. Solids transport (hole cleaning and barite sag),
4. Stuck pipe,
5. Wellbore stability (shale problems and wellbore stresses),
6. Shallow hazards,
7. Gas hydrates,
8. Reservoir productivity (formation damage and evaluation),
9. Environmental issues, and
10. Logistics.

There are few things we all
seem to be forgetting whenever we raise the issue of safety in drilling. There
are safety issues as a result of the cyclic nature of drilling operations. Also
the industry is constantly and quickly growing with its attendant negative
effects on safety which could be either immediate or in the long-term. This
growth creates the need for labour in the shortest possible term. Most often
the newly recruited workforce or even old workforce at all levels of the
company lacks the pre- requisite training, experience and the motivation to meet
the industry’s standards.

There is also the issue of
workforce stress which impart negatively on their concentration thereby
affecting safety in the discharge of their duties. Stress also affects morale. The
cyclic business is also an environment that fails to promote sound, long-term
investment in the physical work environment and the safety culture. I
believe these issues have to be critically looked at with an in-depth analysis in
order to come out with the best working practices to minimize or eradicate it.
By looking at it I mean investing considerably in their wellbeing and also the
training of both new and existing staff.

Bassey, Kufre Peter
M.Sc-Subsea Engineering-2012/2013
University of Aberdeen.

Failures
during drilling operation are commonly  caused by :

Exhaustion from
long shifts, Lack of training, experience, or supervision, Negligence, Rig
collapse;  Contact with power lines or
power sources, Falling object, Slip and fall accident, Cable or lock break, Pipe
tongs slipping, Vibration, Transportation hazards, Exposure to hydrogen sulfide,
Explosion and bowout, Exposure to toxic chemical.

The event of
an accident during drilling can result in severe burns, broken bones facture,
electrocution, dismemberment, amputations, crush injuries etc. Safety should
never be compromised during drilling because its failure will cause a serious
devastating effect on the environment, workers should always wear their
personal protecting equipment (PPE) and safety standard should be strongly
adhered to.Bassey, Kufre Peter
M.Sc-Subsea Engineering-2012/2013
University of Aberdeen.

Earlier comments have emphasized different threats to safety and drilling operation including the risk of a blowout, loss of well control, junk falling etc.

I wish to highlight a salient challenge outlined from Exxon Mobils drill team experience in Qatar operations. Weather conditions in the offshore location getting sometimes up to 50 deg.C places the drill engineers at risk of dehydration and heat exhaustion. Communication among drilling teams is sometimes a challenge as the Engineers are usually pulled from a diversity of nationalities. These have been shown to have a huge effect on drilling operations  has been shown to be a great barrier during drilling operations (Levy et al 2005). Other extreme environmental conditions typical of offshore operations adds a significant risk to the drilling process.

 “The Zechstein Supergroup is a sequence of formations found offshore beneath the North Sea and onshore beneath many coastal European countries, notably the United Kingdom, The Netherlands, Denmark, Germany, and Poland.” (Williamson et al, 1998). The Zechstein creates issues such as Casing Collapse, Loss/gain circumstances, Wellbore losses and gains which have an effect on the overall safety and reliability of a drilling operation.

Reference 

J. Levy; M. Moyer; A. Crawford; D. Musson 2005. “Evolution of the Offshore Drilling Safety Culture”International Petroleum Technology Conference (IPTC), Qatar, November 2005.  

M.D. Williamson; S.J. Murray; T.A.P. Hamilton and M.A. Copland 1998. “A Review of Zechstein Drilling Issues”. SPE Drilling & Completions 1998

A major safety concern with drilling operations is Having a "Kick".

 A Kick is caused by the pressure
in the wellbore being less than that of the formation fluids, thus
causing flow. This condition of lower wellbore pressure than the
formation is caused in two ways. First, if the mud weight is too low,
then the hydrostatic pressure exerted on the formation by the fluid
column may be insufficient to hold the formation fluid
in the formation. This can happen if the mud density is suddenly
lightened or is not to specification to begin with, or if a drilled
formation has a higher pressure than anticipated. This type of kick
might be called an underbalanced kick. The second way a kick can occur is if dynamic and transient fluid pressure effects, usually due to motion of the drillstring or casing,
effectively lower the pressure in the wellbore below that of the
formation. This second kick type could be called an induced kick.[1]

preventing Kicks:

ways of preventing kicks during drilling a well are listed below:

1. is having a proper Well Control measures in place

2.the primary barrier against kicks is the drilling fluid a proper study of the formation is required to determine the formation pressure and prepare adequately weighted"mud" to balnce this pressure,  Drilling fluid engineers must be vigilant and careful to ensure that the pressures reach equilibrium

Reference

1. http://www.glossary.oilfield.slb.com/Display.cfm?Term=kick

2. http://www.rigzone.com/training/insight.asp?insight_id=304&c_id=24

"Everything we hear is an opinion not a fact"

The primary purpose of the Drilling Safety Rule is to clarify and incorporate safeguards that will decrease the likelihood of a blowout occurring during drilling operations. The safeguards address wellbore integrity and well control equipment, and the Drilling Safety Rule focuses on these two overarching issues.

Most of the provisions in the Drilling Safety Rule were identified in the Safety Measures Report that was prepared in the immediate aftermath of the Deepwater Horizon event. A wide range of experts from government, academic institutions, industry, and advocacy organizations were consulted in developing the Report. In addition the draft recommendations were peer reviewed by seven
experts identified by the (US) National Academy of Engineering.

Wellbore integrity

Wellbore integrity provides the first line of defence against a blowout by preventing a loss of well control. It includes the casing and cementing programme and fluid displacement procedures.

Casing and cement and drilling fluids are used to ensure the fluids in a formation do not enter the wellbore during drilling and completion operations. When a well is completed and production begins, the casing and cement continue to prevent uncontrolled flow of fluids into the wellbore. The integrity of the casing and cement are critical to proper well control.

The Drilling Safety Rule will provide greater assurance that operators will follow best cementing and casing installation practices, reducing the risk of a loss of well control.

The Drilling Safety Rule will provide greater assurance that operators will follow best cementing and casing installation practices, reducing the risk of a loss of well control.

Well control equipment

The Drilling Safety Rule also strengthens requirements for blowout preventers (BOPs). In the event of a loss of well control, rig operators use the BOPs to regain control of the well. This is done
by closing the various rams on the BOP stack, which shut off the flow of formation fluids to the surface. Secondary well control system requirements (i.e., ROV intervention capabilities and emergency back-up BOP control systems) ensure that rig operators are able to activate various BOP rams in the event the control system on the rig fails (e.g., loss of power).

Requirements in the Drilling Safety Rule impose new standards to enhance BOP reliability, thereby lessening the possibility of failures that could lead to an uncontrolled blowout and spill with
potentially catastrophic consequences for workers and the environment.

Requirements

1. What must my casing and cementing programs include?

2. What must I include in the diverter and BOP descriptions?

3. What well casing and cementing requirements must I meet?

4. What are the requirements for pressure testing casing?

5. What are the requirements for a subsea BOP system?

6. What are the subsea BOP system requirements for well-completion operations and work over operations?

7. What are the BOP maintenance and inspection requirements?

Reference

www.iadc.org/iadc-hse/iadc-safety-alerts/

www.ngwa.org/Documents/erdsg.pdf

www.onepetro.org/mslib/servlet/onepetropreview?id=00035974

Drilling operation is the heart of exploration for the oil
industry.  Issues of safety are paramount
because an incident during drilling could lead to loss of life, property,
equipment and effect to the environment. 

 Therefore we must take aggressive action to verify the safety
of offshore oil and gas operations, and further tighten oversight of industry’s
practices, and take a careful look at all the questions/concerns arising from disaster’s
in the past.

Also continuous rigorous oversight of industry
drill operations is needed to ensure compliance with all drilling laws and
regulations.

To ensure that measures in  place consisting of targeted inspections
ensuring that tests of BOP (blowout preventer) stacks have been completed,
related records are available for inspection, and that emergency well control exercises
are taking place.
It’s essential that
operators emphasizing that all safety procedures and testing must be conducted
fully and that operators should verify that BOP stacks are properly tested and
configured.

Reference:
http://www.doi.gov/news/pressreleases/Salazar-Launches-Full-Review-of-Of...

Apiambo, Akuro

 SUBSEA ENGINEERING