Amanda Barlow


Blog Post created by Amanda Barlow on Feb 11, 2017

Part 10


With this being the final article in the Offshore Oil and Gas PEOPLE series, I thought it a good idea to list all the roles that will have been covered in the 10-part series. This is by no means an exhaustive list of everyone you are likely to find working on an offshore drilling rig but they are the key roles that you will always find on every rig. There are many more specialists that work in offshore drilling operations but they are too numerous to mention in the scope of these articles.





This article will cover the key personnel who are the operating oil and gas company’s representatives on the rig during drilling operations. Some may be salaried employees of the energy company while others will be contracted specialists who report directly to the operating company. We’ll start with the head honcho of the offshore operations, the Company Man (Wellsite Manager), and work our way down the pay scale – which is not an indication of level of responsibility or workload but rather the higher degree of specialization required to perform the role. Please don’t quote me on this order though, because pay scales differ considerably from one contract to another and depending on boom or bust times in the industry. Some of these people (if they are lucky enough to still have a job) would possibly be on 50% less now (February 2017) than what they were getting paid in February 2015.




The company man, or more commonly used these days is the title wellsite manager (WSM), is the point of contact on the rig for the operating company. He has absolute responsibility over all personnel, financial, technical and performance aspects of the drilling program and the rig being contracted to carry it out. Nothing is supposed to get done on the rig without the company man knowing about it. If any well control barriers are compromised in any way, he needs to know about it immediately. It’s pretty fair to assume that whenever you hear the company man being paged over the rigs PA system by a supervisor, shit has probably just hit the fan somewhere on the rig!


All major drilling decisions moving forward of any point in the program will generally be made in consultation with the drilling superintendent in the head office onshore and any specialists required, but ultimately any immediate action responses are the responsibility of the company man.


There will always be a dayshift company man and nightshift company man with the day company man being the most senior of the two. If there are any major changes to the plan, or emergency situations arise overnight then the night company man will wake the day company man to brief him on what has happened and get advice on how he wants the situation to be handled. While the day WSM will spend most of his shift sitting in front of a computer or on conference calls in the office, the night WSM will spend more time on the drillfloor or in the doghouse overseeing the drilling operations. One of the two will always be present on the drillfloor during critical well control operations and also during cementing operations because of the process safety implications of the procedure.


Wellsite managers come from a variety of backgrounds but one thing is for sure – they have usually all lived and breathed offshore oilfield all their lives and have done the hard yards to get where they are. The two most common career paths are via the roughneck-driller-toolpusher route or the drilling engineer route. Occasionally you’ll come across a WSM that started out as a geologist or some other profession but it’s more likely they used to be a driller or a drilling engineer. The longer and harder their career progression then the more respect they generally earn from the crew under their command. A “young” ex-drilling engineer who has never worked outside an air-conditioned office will never earn quite the same level of respect as that given to an old driller who has spent 30-40 years of his life “on the tools” and sweating it out over decades of hard yakka on a rig.


The “day” WSM will nearly always have had to earn his stripes by first working as a “night” WSM. They are two very distinct positions. With nearly every other role on a rig the dayshift and nightshift crew interchange with each other but this is generally not the case with the company man, except in unusual circumstances.


The day WSM will quite often be a salaried employee of the operating company and be heavily involved in the planning and preparation stages of the drilling campaign back in the office, long before a rig is ever mobilised to the drilling location. He needs to know every stage of the drilling plan and know what all the other workers on the rig are meant to be doing at all stages of the operation. Many company men would have worked a wide variety of offshore drilling roles throughout their career and be very familiar with many of the specialist operations. The night guy will commonly be a contracted worker.


The day WSM is one of the few people who generally get their own cabin. The night WSM sometimes has his own room also but more often would share with the logistics guy, or someone else who only works dayshift. With space being a premium on any rig, all 2-man cabins generally house a dayshift person and a nightshift person so they are always likely to have a room to themselves while off-tour.




The drilling engineer is the company man’s eyes and ears on the rig. He will generally spend a lot of time in the doghouse with the driller and toolpusher and physically oversee all aspects of the well operations so he can report back to the WSM. There is generally only one drilling engineer on the rig at any one time, working on dayshift (0600-1800hrs) unless operations otherwise dictate.


Other duties the Drilling Engineer is responsible for include (but definitely not limited to): 

  • Closely monitoring day-to-day operations and reporting back all findings and observations to the WSM.
  • Collecting and analyzing data relating to all stages of the drilling operations.
  • Performing, recording and disseminating results of “after action reviews” after all key stages of the operation.
  • Keeping track of all costs accrued through the drilling of the well.
  • Working closely with all on-site specialists in order to keep up-to-date on all developments that may have an impact on drilling activities.
  • Making sure that drilling operations comply with statutory and regulatory requirements, with respect to health and safety, emergency procedures and disaster recovery.
  • Continually revising and updating the forward plan and projected timings of the well operations so the logistics coordinator and third-party service providers can accurately prepare equipment in a timely manner.


Drilling engineers will generally have completed some sort of engineering degree prior to being employed by an oil and gas company. Initial training and development is primarily facilitated through graduate development schemes, which involve gaining hands-on work experience through multiple rotations offshore and in-house training sessions. Career progression is mainly driven by individual performance, professional expertise and attainment of professional qualifications.




The wellsite geologist is the source of all operational geological information on the rig and is responsible for all geology related administrative wellsite activity. They are the exploration department’s eyes and ears on the rig and as such, have to make sure that all possible geological and drilling information is gathered in a concise and timely manner. While the WSG works in close cooperation with the company man on the rig he is not actually under his authority. Instead, the WSG reports directly to the “Operations Geologist” who is the “shore based” intermediary between the geologist on the rig and the geology team in town who will be analyzing all the data. The unusual chain of command for disseminating key official geological data from the wellsite geologist follows this line of reporting:


WSG (rig) => Operations Geologist (town) => Drilling Superintendent (town) => Company Man (rig)


While the wellsite geologist is required to immediately notify the company man of any pertinent drilling and geological information, the company man generally cannot act on the information until the town-based drilling superintendent has officially confirmed it. The WSG will report all key geological and drilling data to the operations geologist immediately as it comes to hand. It is then the responsibility of the “ops geo” to disseminate this information to all members of the onshore geology and drilling teams who need to know the information for decision-making. All key drilling decisions are made in collaboration with every department involved in the drilling of the well to ensure that well control barrier criteria are met and any decisions made will not compromise the integrity of the well or process safety systems.


At commencement of drilling, when the well will be drilled “riserless” with no cuttings coming to surface, there will often only be one WSG on the rig. There may be two or even three casing strings run before the riser is finally run and drilled cuttings are brought to the surface. The WSG will be needed during these stages of drilling to confirm that suitable geological formations have been intersected in order to successfully set casing. This task is commonly referred to as “calling casing point”. It is critical that the casing shoe for the conductor and surface casing is set deep enough to withstand pressure from a “kicking” formation further down. Surface casing is run to prevent caving of weak formations that are encountered at shallow depths. The WSG needs to identify when a competent formation is intersected to ensure that the formation at the casing shoe will not fracture at high hydrostatic pressure, which may be encountered later in the drilling of the well. Because there are no drilled cuttings coming to surface all geological data is interpreted from one, or a combination of both, of the following sources:

  • Drilling parameters such as ROP and torque when there are no LWD (Logging While Drilling) tools in the BHA (Bottom Hole Assembly).
  • Real time Gamma Ray and/or Resistivity data from downhole LWD tools.


Once the surface casing has been set and the BOP and riser are run to the seabed, all drilled cuttings will then be circulated to the surface, which means the days get a whole lot busier for the WSG. From this stage on there will generally be two WSG’s operating back-to-back 12-hour shifts.



As the acting representative for the operating company’s geology team, the wellsite geologist will have the following responsibilities:

  • Evaluating offset data before the start of drilling
  • Analyzing, evaluating and describing formations while drilling, using cuttings, gas, formation evaluation measurement while drilling (FEMWD) and wireline data
  • Comparing data gathered during drilling with predictions made at the exploration stage;
  • Advising on drilling hazards and drilling bit optimisation
  • Making decisions about suspending or continuing drilling. Ultimately, it’s the wellsite geologist’s responsibility to decide when drilling should be suspended or stopped.
  • Advising operations personnel both on the rig and in the onshore operations office about any pertinent geological or drilling information as it arises.
  • Supervising mudlogging, MWD/LWD and wireline services personnel and monitoring quality control in relation to these services.
  • Keeping detailed records, writing reports, completing daily, weekly and post-well reporting logs and sending these to appropriate departments.
  • Maintaining up-to-date knowledge of LWD and MWD tools and status of all equipment onboard and in transit to make sure the equipment is available and in working order when it is needed.


In expected HPHT (high pressure high temperature) wells it is critical the WSG can identify (and immediately communicate) any identifying signs of increases in pore pressure. These can include the following telltale signs:

  • Changes in flow rate and active mud system volumes. If the formation pressure becomes higher than the hydrostatic pressure being exerted by the circulating drilling fluid then the mud will become “underbalanced” and the well will “kick”. If this kick isn’t detected early enough then a catastrophic blowout could occur.
  • Presence of “cavings” coming over the shakers. When drilling over-pressured shales, it is common for the formation to undergo stress relief causing chips of rocks to cave from the borehole wall. These overpressure “cavings” tend to be larger than normal cuttings and may be concave or propeller shaped.
  • Increase in ROP (rate of penetration) and volume of cuttings. A pressure transition zone will make drilling easier because of the trapped water reducing compaction and the increase in pore pressure reducing differential pressure, allowing cuttings to be released more easily into the mud stream.
  • Changes in LWD data, in particular resistivity and sonic, density and neutron.
  • Changes in drilling parameters, especially torque, drag and overpull. This can be due to deterioration of borehole integrity causing an increase in volume of cuttings and cavings in the circulating mud.
  • Rise in background gas level, changes in the composition of the gas, or presence of “connection” gas, which is a result of swabbing downhole hole when the pumps are turned off to make a connection (add another stand of drillpipe).
  • Changes in pump pressure. An influx of gas into a well may reduce the density of the drilling fluid and therefore it will require less pressure to circulate the drilling fluid.
  • Change in properties of mud.
  • Changes in downhole temperature. Generally there will be slight decrease in temperature immediately above the over-pressured zone and then a steady increase with depth at a higher rate than in the normally pressured zone above.


If the wellsite geologist identifies any potentially hazardous changes in the drilling, the driller and company man must be notified immediately, and then the operations geologist will be notified. If a potentially dangerous situation is recognized then the drilling will be stopped immediately while the company man either makes a decision on what to do next or waits for official instructions from the drilling superintendent in town on how to proceed.


The wellsite geologists spend most of their time working in the mudlogging unit (like the hardworking one in the photo below!), which is where all the monitoring equipment for the rig is located and also where the mudloggers/sample catchers will deliver the cuttings samples for them to inspect and describe. All rock cuttings are inspected under a microscope and a detailed description written for every sample that is generally collected in composite 5, 10 or 20 m intervals.




Cuttings Descriptions

The cuttings descriptions need to be very detailed and follow an industry standard format that includes (but is not restricted to) the following observations:

  •  Rock types and percentage of each found in the sample
  • Color
  • Texture
  • Grain or crystal size
  • Sphericity, roundness and sorting of sandstone grains
  • Type of cement and/or matrix
  • Any fossils or accessory minerals
  • Presence of hydrocarbon indications, such as fluorescence or “show”
  • Estimate of porosity




A detailed well log is created combining all the cuttings information, LWD and MWD data and drilling parameter data, and submitted along with a daily report every 24 hours. When the WSG finishes the shift and hands over to the next shift they have to have all of the reporting and samples descriptions up-to-date at the time of them handing over.


To become a wellsite geologist, you’ll need a degree in geology or possibly even chemistry, geochemistry or geophysics. There is no formal wellsite geologist qualification, but you would need to obtain knowledge in areas such as wellsite and offshore safety management, wellsite operations, formation evaluation of wireline, FEWD logs, and risk assessment before starting as a WSG. Most WSG’s start their offshore career working as a mudlogger, MWD engineer or mud engineer and gain knowledge in the fields that a WSG is responsible for. They also need to possess supervisory skills, the ability to work well under pressure and the ability to quickly make decisions.


As most wellsite geologists work as independent consultants and are employed on a contracting basis, it’s up to them to handle their own career progression. Any wellsite geologists who progress beyond this position will generally move into an operations geologist role, with a few even moving up into company man positions.


While a wellsite geologist might earn a lot per day there is little job security, and quite often no permanent rotation. They may only get flown onto the rig the day before drilling operations begin and flown off again immediately after the well is completed or wireline logging is completed. The date of your arrival and departure is quite often only known within days of it occurring so long term social commitments are impossible to plan. You can either expect to have to fly out to the rig at very short notice or have unplanned months without any work…or even years, as the case is for many now!




The drilling fluids engineer, who is most commonly referred to as the mud engineer, or just the mud man, is the person responsible for ensuring the drilling fluid properties are within designed specifications.


The drilling fluid (mud) is a vital part of drilling operations and has the following functions:

  • Provides hydrostatic pressure on the borehole wall to prevent uncontrolled production of reservoir fluids.
  • Lubricates and cools the drill bit
  • Carries the drill cuttings up to the surface
  • Forms a "filter-cake" on the borehole wall to prevent drilling fluid invasion into the formation
  • Provides an information medium for well logging
  • Helps the drilling by fracturing the rock from the jets in the bit.


One of the most important mud properties is the mud weight (density). If the mud weight exceeds the fracture pressure of the formation, the formation may fracture and large quantities of mud can be lost to it, in a situation referred to as lost circulation. If the mud weight is too low it will have a hydrostatic pressure that is less than the formation pressure. This will cause pressurized fluid in the formation to flow into the wellbore and make its way to the surface. This is referred to as a formation "kick" and can lead to a potentially deadly blowout if the invading fluid reaches the surface uncontrolled.


To maximize the effectiveness of these tasks, the mud contains carefully chosen additives to control its chemical and rheological properties. For the technically minded, the drilling mud is usually a shear thinning non-Newtonian fluid of variable viscosity. When it is under more shear, such as in the pipe to the bit and through the bit nozzles, viscosity is lower which reduces pumping-power requirements. When returning to the surface through the annulus it is under less shear stress and becomes more viscous, and hence better able to carry the rock cuttings. Bentonite is commonly used as an additive to control and maintain viscosity, and also has the additional benefit of forming a mud-cake (also known as a filter cake) on the borehole wall, preventing fluid invasion into the formation.

Barite is commonly used to increase the mud weight to maintain adequate hydrostatic pressure downhole in order to avoid a kick and ultimately a blowout from uncontrolled production of formation fluids. The mud pits at the surface have their levels carefully monitored, since an increase in the mud level indicates a kick is taking place, and may require shutting in the well and circulating heavier weighted drilling mud to prevent further formation fluid or gas production. The drilling mud must be chemically compatible with the formations being drilled; in particular the salinity must be chosen so as not to cause clay swelling or other problems. Offshore rigs typically use synthetic oil-based mud although water-based mud is also sometimes used.


Prior to drilling a well, a mud program will be worked out according to the expected geology, in which products to be used, concentrations of those products, and fluid specifications at different depths are all predetermined. As the hole is drilled and gets deeper, more mud is required, and the mud engineer is responsible for making sure that the new mud to be added is made up to the required specifications. The chemical composition of the mud will be designed so as to stabilize the hole.


As drilling proceeds, the mud engineer will get information from other service providers such as the mudlogger about progress through the geological zones, and will make regular physical and chemical checks on the drilling mud. The viscosity and density are frequently checked. As drilling proceeds, the mud tends to accumulate small particles of the rocks that are being drilled through, and its properties change. It is the job of the mud engineer to specify additives to correct these changes, or to partially or wholly replace the mud when necessary.


Mud engineers come from a varied background, with many having no formal tertiary qualification but rather have had offshore drilling experience within one of the many other roles found on an offshore drilling rig. It’s common to find mudloggers with a geology background transferring into the higher-paid role of the mud engineer.


Prior to working on his own, the junior mud engineer will have attended a special training course and will spend time working with a senior mud engineer to gain experience. The least experienced mud engineer will commonly work permanently on nightshift with the experienced mud man working days so he can communicate with the company man and onshore drilling support team. The derrickman and roughnecks are assigned to help the mud man whenever he needs assistance with altering the mud properties or any other pit-related work. With the mud being one of the key process safety barriers in the drilling process the mud engineers are always kept busy monitoring it.


Drilling fluids operations are often contracted to service companies, with the largest four companies for mud services being M-I SWACO (A Schlumberger Company), Baroid Drilling Fluids (Halliburton Oilfield Services), Baker Hughes Drilling Fluids, and Weatherford International Drilling Fluids.




Many offshore drilling operations will have a HSE representative within the drilling contractor crew (commonly referred to as the Rig Safety and Training Coordinator or RSTC) and also the operating company will have their own health and safety representatives. There may be a nightshift and dayshift or just the one person who works mostly dayshift, except when needed if there is a safety incident overnight. They can be either an employee of the operating oil and gas company or a contract worker.


The responsibility of the HSE coordinators is to ensure that all tasks on the rig are completed in accordance with company and regulatory requirements by using approved procedures and permits.

Safety reps normally come from quite varied backgrounds, with many having worked other roles within the drilling industry or sometimes even come from a military background. A background as a rig worker is most advantageous because they would then have a competent knowledge of the tasks performed on the rig as well as all the equipment being used. This knowledge would make investigations and report writing of incidents a lot easier.


As well as the unofficial duties as the rig psychologist, auditor, mentor, deckhand, and personal problem advisor, the HSE coordinator also has to fulfill the following official tasks:

  • Monitor the safe operation of all workers on the rig
  • Participate in key project management activities e.g. HAZIDs and HAZOPs
  • Provide management system documentation development and implementation
  • Incident investigation
  • OHS auditing
  • Conduct weekly safety meetings and disseminate incident investigation findings from other areas within the industry


With the industry becoming increasingly heavily regulated the safety rep will be kept busy filling in paperwork and completing safety audits in between investigating incidents and report writing. He will also quite often work out of an office that is close to the company man’s office and has a coffee machine, so it’s the obvious place to kill time while waiting for the morning meetings to start.




The last role to be covered in this series of articles is the drilling (and materials) logistics coordinator. The DLC is responsible for coordination of all materials, personnel movements and logistics support for the rigs operations. Key responsibilities are:

  • Liaise with key personnel for timely provision of personnel, services, equipment and materials
  • Liaise with key onshore supply operations personnel for the load-out and back-load of equipment and materials
  • Coordinate storage, maintenance, record keeping and reporting of all the company's and contractor equipment on the rig.


The DLC will commonly work out of the same office as the company man, or close to it, so he can communicate all material and people movements and current state of operations in order to provide timely logistics advice to service providers and rig crew. There is generally only one onboard at any one time, working dayshift hours unless otherwise needed.


A background in rig operations through either working as a member of the drilling or deck crew, or as a service provider is advantageous, as they will need to know the name of, and be able to identify every part needed on the rig. Their backgrounds are generally quite varied, as it is not a position that requires a formal certification.


final photo




That concludes this series of articles, and while it was by no means an exhaustive list of roles performed in offshore drilling operations it covered the main ones. I hope you have a better understanding now of the main roles performed in offshore drilling operations and the people who carry them out.


You can find the rest of the series of articles in Offshore Oil and Gas PEOPLE here: Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8 and Part 9. A compilation of all parts of the series will soon be available in a paperback and eBook format. Watch this space for further details!


book cover 


Amanda Barlow is a wellsite geologist in the offshore oil and gas industry with a field-based geology career spanning over three decades. As well as being a recreational marathoner who has run over 40 marathons in 16 different countries she is also a published author of two books: “Call of the Jungle – How a Camping-Hating City-Slicker Mum Survived an Ultra Endurance Marathon through the Amazon Jungle” and also “An Inconvenient Life – My Unconventional Career as a Wellsite Geologist”. You can connect with her through the Pink Petro community, LinkedIn: or through her Facebook page: