The Job of A Mudlogger

Mudlogging is one of the many important activities during drilling, especially in exploration drilling. Third-party service providers make up about half of the workforce on an offshore rig. With so many hi-tech and specialized operations being performed at all stages of the drilling operations it’s imperative that experts in their field perform these tasks.

The job of the “mudloggers” is to monitor the drilling operations from the time the well is spudded to the time the well is safely drilled, tested and secured for either production or abandonment.

“Mudlogger” is the generic term used to describe the field specialists who monitor the well and also collect samples for the geologist. The career progression for a mudlogger is to generally start as a sample catcher while they learn about the drilling operations, then progress to a mudlogger and with further experience, become a data engineer.

Sample Catchers

Dedicated sample catchers aren’t always part of the team but they often get “thrown in” as a complementary part of the mudlogging services. They don’t need to have any prior experience in working offshore or as a mudlogger, so it’s a very good entry-level job and is generally the starting position for a graduate geologist (or anyone else) who wishes to work offshore. Although you don’t need to be a geologist to be a sample catcher, most of them will be and will go on to get trained as a mudlogger.

Sample catching is without a doubt the least glamorous and lowest paid of all jobs on the rig…but you have to start somewhere! The role of a sample catcher is to provide the most basic geological data acquisition on the rig and to assist with all general activities when possible. The main duties of the sample catcher are:

  • Ensuring that representative geologic samples are caught throughout the drilling or reaming phases of the well program. This is done by collecting cuttings (drilled rock) samples, from the proper “lagged” (explained below) depths and at the proper intervals as required for evaluation. These samples are collected off the shale shakers, screened and washed, divided into correct portions, and packed into sets for the Client, partners, and government agencies. They may also have to assist in core recovery and packaging as required.
  • Preparing a clean “cuttings” sample on a sample tray for the wellsite geologist and mudlogger, who will then examine it under the microscope and describe the lithology of the drilled formation.
  • Assisting mudloggers and data engineers to perform regular and frequent calibration checks of instruments, perform normal routine maintenance of sensors and other equipment and also assist logging crew with rig-up/rig-down procedures.


A shale shaker


The sample catcher reports directly to the mudlogging crew who will ensure his duties are performed correctly. This may include on-the-job training as required. They work out of the mudlogging unit, which is always close to the shale shakers and these are generally one or two levels below the drill floor.

The shale shakers are vibrating screens that separate the drilling fluid from the drilled rock cuttings. The “shaker house” is a very noisy place and double hearing protection must always be worn. There will be multiple shakers to accommodate the large volume of cuttings that can be produced when the drilling rate of penetration is high (i.e. they are drilling fast!). It’s a very “dirty” job and multiple layers of personal protective equipment need to be worn to prevent skin contact with the drilling mud, which can cause serious skin inflammation.


Mudloggers and Data Engineers (DE)

Mudloggers and data engineers are responsible for gathering, processing and monitoring information pertaining to drilling operations. They don’t only collect data using specialist data acquisition techniques – they also collect oil samples and detect gases using state-of-the-art equipment.

The information amassed by these guys is analyzed, logged and then communicated to the team that is responsible for the physical drilling of the well. Without the help of the mudlogger, the drilling operations would be less efficient, less cost-effective and much more dangerous. The mudlogger is vital for preventing hazardous situations, such as well blowouts.

They also provide vital assistance to wellsite geologists and write detailed reports based on the data that is collected. Being an entry-level position, employees will be given a mixture of ‘on-the-job’ training and expert in-house training courses, which cover different aspects of drilling operations. A major part of the training will focus on the use of specialist computer software.

Typically, you will need a degree in geology to start a career as a mudlogger. However, candidates with degrees in physics, geochemistry, chemistry, environmental geoscience, maths or engineering may also be accepted.

Along with the sample catchers and data engineers, the mudloggers work out of the mudlogging unit, which is a pressurized sea container-type of office, which is positioned close to the drill floor and shaker house.

The unit will have an air-lock compartment when you first enter it so as to maintain the positive pressure within the unit whenever somebody leaves or enters the unit.

This is the main control room for monitoring the drilling operations and is full of sophisticated and delicate equipment and computer systems. Positive pressure needs to be maintained to ensure the air pressure inside the container is higher than that of the outside area to prevent contamination of sensitive monitoring equipment – and also to ensure the safety of the crew working inside the unit should the outside air become contaminated through uncontrolled releases of hydrocarbons from the well.


A mudlogging unit


One of the most important tasks of the mudlogger is to oversee the collection of not only geological samples but also mud and gas samples from the well during drilling operations. To be able to do this accurately they have to know the exact “lag time” (or “bottoms-up time”) that it will take for the drilled cuttings or mud and gas to arrive at the surface after being drilled and circulated up the outside of the drill hole (annulus) while suspended in the drilling mud. The lag time maybe a few minutes in a shallow hole or as much as several hours in deep wells with low mud flow rates. To be able to work this time out accurately there are many factors that have to be taken into consideration. The lag time depends on:

  • the annular volume fluid
  • flow rate, which in turn requires knowledge of:
  • dimensions (internal diameter (ID) and outside diameter (OD)) of surface equipment, drill string tubular, casing and riser.
  • mud pump output per stroke, pumping rate, and efficiency.

While the computer’s software will work this out automatically, the calculated value may be incorrect if the operator has entered erroneous or incomplete values for the pipe or hole dimensions, or if the hole is badly washed out. This has to be monitored very carefully to avoid catching mud, gas and cuttings samples at incorrect depths.


The mudloggers and DE’s monitor the drilling operations via a series of sensors that are placed at various locations around the drill floor, pit room, and shaker house.

The main drilling and mud parameters that are recorded are: hook movement, weight on hook, standpipe pressure, wellhead pressure, rotary torque, pump strokes, RPM, mud pit levels, mud density, mud temperature, mud resistivity, and mudflow.

These parameters are monitored in real-time and any deviances from the expected normal values must be immediately reported to the driller. The DE will view and monitor all the drilling parameters on a screen as shown below.

drilling parameters-amanda
A drilling parameter screen


The five most important monitoring tasks that the mudlogger and DE must watch out for are:

  • Rate of penetration increase, which could indicate they have drilled into a reservoir formation
  • Mud pit volume gain or loss, which could indicate the well is taking a kick, or losing fluid into the formation
  • Mudflow rate change
  • Mud density variation
  • Indication of oil or gas.

The mudlogging unit is a very confined workplace and there may be up to several people working in there at any one time, especially if it’s a “combo” unit, which houses the mudloggers, MWD engineers and possibly also the directional drillers.

Generally (but not always), the same service provider company performs all of these roles so it is quite common for data engineers to progress into a role as an LWD/MWD engineer. Other common career progressions for mudloggers/data engineers are as a wellsite geologist or drilling fluids engineer (mud engineer).

inside a mudlogging unit - amanda
Inside a mudlogging unit

The complete list of responsibilities of the mudloggers is too exhaustive to detail in this article but the above-mentioned roles are the main ones. Like most jobs on the rig, daily reports are a big part of the data engineer’s responsibilities.

The mudloggers report directly to the wellsite geologist, who are generally working in the mudlogging unit alongside them. Because the mudloggers are required to monitor the drilling operations from the commencement of drilling they will always be employed on a permanent rotating roster, which is generally 4-weeks on, 4-weeks off.

This article was written by Amanda Barlow, a wellsite geologist and published author of “Offshore Oil and Gas PEOPLE – Overview of Offshore Drilling Operations” for a beginner guide to working in offshore drilling operations, and “An Inconvenient Life – My Unconventional Career as a Wellsite Geologist”

Another great book you may want to read if you like to get an overview of oil exploration, drilling and production is “The Story of Oil and Gas”: How Oil and Gas Are Explored, Drilled and Produced”.



Geothermal Plants near a Volcano

Geothermal plants can be safely situated near a volcano, says Dr. Roland Horne, Thomas Davies Barrow Professor in the School of Earth Sciences and Senior Fellow at the Precourt Institute for Energy at Standord University.

You can read the outstanding article from Stanford University titled Geothermal at the foot of Kilauea on this and on the recent volcano eruption of Mt. Kilauea in Hawaii at

In this article, Dr. Roland Horne discusses geothermal energy in the face of natural hazards and a way to tap the earth’s heat far from volcanoes in the future.

I highly recommend you read the article that I mention above. In this article you can also watch the awesome lava flow from a fissure of Mt. Kilauea on May 19, 2018 and learn about Stanford University’s School of Earth, Energy & Environmental Sciences.

Digital Rock Physics – Core Analysis Using Digital Technology

Offshore oil and gas processing platform,

In the last decade, there has been an important breakthrough in how petroleum engineers and geoscientists obtained oil and gas reservoir rock properties.

Traditionally, reservoir rock properties or petrophysical properties such as porosity, pore size distribution, effective and relative permeability, capillary pressure, water saturation and other reservoir parameters are determined from Special Core Analysis (SCAL), electric logs and well pressure transient tests. In recent years, a new method in determining rock properties using Digital Rock Physics (DRP) has gained serious attention from petroleum engineers, petro-physicists and geoscientists.

What is digital rock physics? Digital rock physics is also referred to as digital core analysis. In this measurement method, high-resolution digital images of the rock pores and mineral grains of selected reservoir core samples are made and analyzed. These images are usually 3D digital X-ray micro-tomographic images. The rock properties are then determined using numerical simulation at the pore scale.

The significant benefit of this new DRP technology is now a large number of complex reservoir parameters can be determined faster and more accurately than the traditional laboratory measurements or well testing methods.

Using the DRP technology to determine the rock properties, oil and gas companies can now analyze their reservoir capacity and performance more accurately and sooner during the field evaluation and development phase. This, in turn, allows them to develop and manage their reservoirs more efficiently and economically.

Source – Digital Rock Physics for Fast and Accurate Special Core Analysis in Carbonates – A Chapter in New Technologies in the Oil and Gas Industry – By  Mohammed Zubair Kalam

Gas Handling, Conditioning and Processing

This gas handling, conditioning and processing course is designed and presented by Dr Maurice Stewart to teach you how to design, select, specify, install, test and trouble-shoot your gas processing facilities.

This gas handling, conditioning and processing course has been attended by thousands of oil and gas professionals since Dr Maurice Stewart began teaching it more than 20 years ago. Dr Stewart is a co-author of a widely acclaimed “Surface Production Operations: Design of Gas Handling Facilities” along with Ken Arnold.

By attending this course, participants will:

1. Know the important parameters in designing, selecting, installing, operating and trouble-shooting gas handling, conditioning and processing facilities.
2. Understand the uncertainties and assumptions inherent in designing and operating the equipment in these systems and the limitations, advantages and disadvantages associated with their use.
3. Learn how to size, select, specify, operate, maintain, test and trouble-shoot surface equipment used with the handling, conditioning and processing of natural gas and associated liquids such as separators, heat exchangers, absorption and fractionation systems, dehydration systems, refrigeration, low temperature separation units, JT plants and compression systems.
4. Know how to evaluate and choose the correct process for a given situation.

Course Content

In this 5-day course, Dr Maurice Stewart will cover the following topics:
• Fluid properties, basic gas laws and phase behaviour
• Well Configurations, surface safety systems (SSS) and emergency support systems (ESS)
• Gas Processing systems, selection and planning
• Water-hydrocarbon phase behaviour, hydrate formation prevention and inhibition
• Heat transfer theory and process heat duty
• Heat exchangers: configurations, selection and sizing
• Gas-liquid separation and factors affecting separation
• Types of separators and scrubbers, and their construction
• Gas-liquid separators and sizing
• Liquid-liquid separators and sizing
• Three phase separator sizing
• Pressure vessels: the internals, mechanical design and safety factors
• Separator operating problems and practical solutions
• Gas compression theory, compression ratio and number of stages
• Compressor selection: centrifugal compressors vs. reciprocating compressors
• Vapor recovery units, screw compressors and vane compressors
• Compression station design and safety systems
• Performance curves for reciprocating compressors
• Absorption process and absorbers
• Adsorption process and adsorbers
• Glycol gas dehydration unit design and operation
• Glycol unit operating variables and trouble shooting
• Glycol selection and glycol regeneration
• Acid gas sweetening processes and selection
• Fractionation, refrigeration plants, expander plants and J-T plants
• Process control and safety systems

Course Materials

Participants will receive the following course materials:
1. The 3rd Edition of Volume 2 of the widely acclaimed “Surface Production Operations: Design of Gas Handling Facilities” written by Ken Arnold and Dr Maurice Stewart. This textbook continues to be the standard for industry and has been used by thousands since its first printing over fifteen years ago.
2. A comprehensive set of lecture notes for after course reading and reference
3. An extensive set of practical in-class “case study” exercises developed by Dr Stewart that will be used to emphasize the design and “trouble-shooting” pitfalls often encountered in the industry.

Who Should Attend

• Facility engineers, production engineers, design and construction engineers, team leaders, operations engineers, maintenance team leaders/engineers and other personnel who are or will be responsible for the designing, selecting, sizing, specifying, installing, testing, operating and maintaining gas handling facilities, gas plant facilities and gas pipelines.
• Experienced professionals who want to review or broaden their understanding of gas handling, conditioning and processing facilities and gas pipeline operation and maintenance.
• Professionals with little to moderate experience with the handling or processing of natural gas and associated liquids.

If you like to receive a pdf file of this course outline, please contact us.

Registration Information

Course date: November 25-29, 2019
Location: Singapore
Tuition: US$4500

Registration Form

If you or your people want to attend this course, please register HERE.

Contact information

About Dr. Maurice Stewart

Maurice Stewart - LDI Training Dr. Maurice Stewart, PE, CSP, is a Registered Professional Engineer and Certified Safety Professional with over 40 years of experience in international consulting, trouble-shooting oil, water and gas processing facilities; and leading safety audits, hazards reviews and risk assessments.

He is internationally respected for his teaching excellence and series of widely acclaimed textbooks in the areas of designing, selecting, specifying, installing, operating and troubleshooting:

  • Oil and water handling facilities
  • Gas handling, conditioning and processing facilities
  • Facility piping and pipeline systems
  • Gas dehydration and sweetening facilities
  • Pumps, compressors and drivers
  • Instrumentation, process control and safety systems
  • Oil and gas measuring and metering systems

Dr. Stewart is the author of several new textbooks related to oil and gas processing facilities; and he is one of the co-authors of the SPE Petroleum Engineering Handbook.  He has authored and co-authored over 90 technical papers and contributed to numerous conferences as a keynote speaker. Dr. Stewart has taught over 60,000 professionals from more than 100 oil and gas related companies in 90 countries.

Dr. Stewart serves on numerous international committees responsible for developing or revising industry Codes, Standards and Recommended Practices for such organizations as ANSI, API, ASME, ISA, NACE and SPE. He is currently serving on the following American Petroleum Institute (API) committees: API RP 14C, RP 14E, RP 14F, RP 14G, RP 14J, RP 500 and RP 75. He has developed and taught worldwide short courses for API related to Surface Production Operations. In 1985, he received the National Society of Professional Engineers “Engineer-of-the-year” award.

Dr. Maurice Stewart holds a BS in Mechanical Engineering from Louisiana State University and MS degrees in Mechanical, Civil (Structural Option) and Petroleum Engineering from Tulane University and a PhD in Petroleum Engineering from Tulane University.  Dr. Stewart served as a Professor of Petroleum Engineering at Tulane University and Louisiana State University.

Here are the most frequently requested Dr. Maurice Stewart courses:

  • Oil and water handling facilities
  • Gas handling, conditioning and processing
  • Production safety systems
  • The new API RP 14C and API RP 17V
  • Plant piping and pipeline systems
  • Oil and gas project management
  • Pumps, compressors and drivers

If you are interested in having an inhouse course with Dr. Maurice Stewart, please contact LDI Training at

Production Safety Systems

A 5-day course by Dr. Maurice Stewart incorporating the new 2017 8th Edition of API RP 14C, the new API RP 17V 1st Edition, API RP 14J, API RP 500/505, API RP 520/521/2000, IEC 61508-2 and IEC 61508-3.

This intense Production Safety Systems course presents a systematization of proven practices for providing a safety system for onshore and offshore production facilities. Thousands of oil and gas professionals have attended this course since it was offered by Dr. Maurice Stewart more than 20 years ago.

This production safety systems course has been updated to reflect the changes provided in the new API RP 14C and the API RP 17V. In this course, you will learn the latest concepts, methods and practices that will make your facility operationally safe.

What You’ll Learn

• Provisions for designing, installing and testing both safety and non-marine emergency support systems (ESSs) on both onshore and offshore production facilities.
• Concepts of a facility safety system and outline production methods and requirements of the system.
• Guidance on how safety analysis methods can be used to determine safety requirements to protect common process components from the surface wellhead and/or topside boarding valve and for subsea systems including all process components from the wellhead and surface controlled subsurface safety valve (SCSSV) to upstream of the boarding shutdown valve. (Note: The shutdown valve is within the scope of API RP 17V for gas injection, water injection, gas lift systems and chemical injections.)
• The importance of “Safety Concept,” “Safety Reviews,” and “EB-HAZOPs.”
• A method to document and verify process safety system functions, i.e., safety analysis function evaluation (SAFE chart).
• Design guidance for ancillary systems such as pneumatic supply systems and liquid containment systems.
• A uniform method of identifying and symbolizing safety devices.
• Procedures for testing common safety devices with recommendations for test data and acceptable test tolerances.
• The Principles of Safe Facility Design and Operation, specifically, how to Contain Hydrocarbons, Prevent Ignition, Prevent Fire Escalation and Provide Personnel Protection and Escape.
• The Principles of Plant Layout Partitioning and how to partition a plant into Fire Zones, Restricted Areas and Impacted Areas thereby minimizing the Risk to Radiation, Explosion, Noise and Toxicity.
• How to determine Electrical Hazardous (Classified) Locations and determine what Electrical Equipment should be installed in these locations,
• The purpose of Surface Safety Systems, specifically, the Emergency Shut-down System, Emergency Depressurization System, Fire and Gas Detection Systems and High Integrity Protection Systems,
• The Objectives, Types, Location and Placement of Fire and Gas Detection Systems.
• The Objectives, Types and Performance of Active and Passive Fire Protection Systems.
• The Function, Types, Selection and layout of Vent, Flare and Relief Systems to minimize the effects of Radiation, Flammable Gas Dispersion and Toxic Gas Dispersion.
• The function and design considerations of Liquid Drainage Systems
• How to determine piping “spec breaks”.
• How to evaluate workplace and operating/maintenance procedures for “hidden” hazards.
• How to effectively design facilities and work areas to reduce human errors and improve performance.

Course Content

• Principles of safe facility design
• Ignition prevention
• Fire escalation prevention
• Personnel protection and escape
• Installation layout
• Electrical installations in hazardous (classified) areas
• Safety systems
• Pressure ratings and Specification breaks
• High Integrity Pressure Protection Systems (HIPPS)
• Safety system and ESS bypassing
• Onshore gathering station safety systems
• Fire and gas detection systems
• Active and passive fire protection
• Relief, vent and flare systems
• Liquid drainage systems
• Electrical Area Classification

Who Should Attend

This workshop is specifically targeted for professionals and engineers who are involved in safety or production operations and who want to:

1. Develop a better understanding of the effectiveness of existing Production Safety System initiatives at existing oil and gas facilities.
2. Appreciate the main steps contemplated in the Safe Design of a plant or facility,
3. Better understand the scope and functioning of the various safety related equipment installed onshore, offshore and subsea.
4. Review or broaden their understanding of how to conduct a safety analysis, Experience-Based HAZOP and how to install electrical equipment in hazardous (Classified) locations.
5. Other professionals who want to develop a better understanding of how to conduct a Safety Analysis, EB-HAZOPs and install electrical equipment in hazardous (Classified) locations.

Course Materials

• Each participant will receive a comprehensive set of worksheets and checklists to aid them in conducting a safety analysis
• Each participant will receive a comprehensive set of lecture notes for after course reading and reference
• An extensive set of practical in-class “case study” exercises specially designed by Dr. Maurice Stewart that emphasizes the design and “trouble-shooting” pitfalls often encountered in the industry.

If you like to receive a pdf file of this course outline, please contact us.

Registration Information

Course date : December 10-14, 2018
Location : Singapore
Tuition : US$4500

Registration Form

If you or your people want to attend this course, please register HERE.

Contact information

LDI Training Pte Ltd
369 Holland Road #02-04
Singapore 278640

Email :
Website :

The New API 2017 RP 14C and API RP 17V


In 2017, API published the new 8th Edition of API RP 14C and created the new 1st Edition of API 17V for subsea applications.

Here are the major modifications of API RP 14C and the new guidelines provided in API RP 17V:

1. The API RP 14C, new 8th Edition “Analysis, Design, Installation, and Testing of Safety Systems for Offshore Production Facilities” was developed in coordination with the new First Edition of API RP 17V “Recommended Practice for Analysis, Design, Installation, and Testing of Safety Systems for Subsea Applications”.

2. Changes in safety system technology.

3. Additional guidance for facility safety systems as they have become larger, more complex and moved into deeper water.

4. Added requirements include an extensive emphasis on the performing of hazards analysis due to increased flow rates, pressures, temperatures, and water depth.

5. Better alignment with API Standard 521, “Pressure-relieving and Depressuring Systems”.

6. Additional requirements for pumps and compressors greater than 1000 HP and reference to API 670.

7. Additional requirements to protect against backflow and settle-out pressures.

8. New address on low-temperature hazards.

9. Enhancements on open deck Fire and Gas detection placement and sensor type.

10. Extensive emphasis on performing hazards analysis to include the introduction of the Prevention vs. Mitigation concepts.

11. Additional annex to cover topside High-Intensity Pressure Protection Systems (HIPPS).

12. Additional annex to cover Safety System By-passing.

13. Additional annex to cover Logic Solvers.

14. Additional annex to cover Remote Operation.

Since the API RP 14C and API RP 17V are critically important for the safety of your offshore and subsea facilities, please share this information with your company’s managers, supervisors, engineers and safety personnel who need to:

1. Develop a better understanding of the modifications of the 2017 edition of API RP 14C and the newly created API RP 17V

2. Appreciate the main steps contemplated in the Safe Design of onshore, offshore and subsea applications

3. Better understand the scope and functioning of the various safety-related equipment installed onshore, offshore and subsea.

If you want to understand the new API RP 14C and API RP17V to keep your production facilities safe, Dr. Maurice Stewart conducts a 5-day course – Production Safety Systems – that incorporates the new API RP 14C and API RP 17V.

This article is written by Dr. Maurice Stewart.

For more information about the course, please contact