“Strive to be ambitious without forsaking your principles…”
INTERVIEW COORDINATED BY SATINDER CHOPRA
Cheran Mangat is a geophysicist who has worked in North America and international arenas. She is a highly motivated individual who likes to use geophysical tools and technologies to make significant contributions to the bottom line. Having worked as an explorer, geophysical interpreter, development geophysicist, and stratigrapher, she has seen it all. On being asked for an interview, Cheran was quite supportive, and that led me to ask her a wide range of questions. The following are excerpts from the interview.
Cheran, please tell me something about yourself.
I am a third generation Sikh from Uganda, East Africa. My family came to Canada as refugees in the late 1970s during the unforeseen political instability in Uganda. It was quite a troubling time for many of the citizens that were forced to leave. All their assets were confiscated by the government, and they left without any personal belongings.
As a result, I saw my parents, who were in their 40’s, starting with nothing and having to work really hard to make ends meet, having left behind a life of luxury. Their education was completed in Africa and India, and it wasn’t recognised, so they had to requalify. To put it mildly, it was quite a struggle, and that is what inspired me to get a good education and what led to my drive and ambition. I was lucky enough to get opportunities in my career that I could only dream of. We lived in the UK and Canada. I completed my degree in geophysics from the University of Calgary.
Having relocated from the UK to Calgary, it was tough juggling a full-time job and raising two young children. My husband was commuting from the UK as he was busy with his dental surgery practice, and we were not sure how long we would be in Calgary. I had to be a “SuperMum” but it all worked out well in the end. I sure developed my organisational skills in the process! Our son is a business graduate from the University of British Columbia, working in Toronto, and our daughter is studying to become a Doctor of Veterinary Medicine.
Please tell me about your work experience.
My first position after graduation was in seismic processing for Spectrum Energy (UK). I worked my way up to manage their special projects team, which involved land and marine AVO-compliant processing and inversion studies for many oil and gas companies. This is where I developed my interest for quantitative interpretation (QI), taking seismic interpretation to the next level. I wanted to focus in this area, and this is when I moved to Fugro-Jason UK (FJ).
They had a brilliant training program for deterministic and geostatistical inversion. I became well-versed with running the Jason Geoscience Workbench (JGW)., which not only has inversion algorithms, but a whole suite of tools for integration of all the disciplines (G&G, petrophysics and engineering) to mitigate the risk for oil and gas exploration and development.
I would like to acknowledge my mentors, because this is where I learnt the most about QI and the integration of all available information into the geological model. I have 16 years of experience using their software for characterization of conventional, shale, heavy oil SAGD, and deep-water reservoirs in basins from all over the world.
I am skilled in running deterministic/stochastic post- and pre-stack inversions for 2D, 3D and 4D seismic surveys, structural interpretation, identifying, evaluating, and appraising drilling locations through quantitative interpretation, using seismically derived properties for probabilistic analysis and pay predictions, and integrating seismic properties into predictive reservoir models for simulation and history matching.
After working in the UK office for three years, I was relocated to the FJ Calgary office in a technical role, then offered the position of heading up their Canadian operations. This is where I developed my leadership, sales, and marketing skills. Fugro-Jason was the best company I worked for; it was like being in a big, happy family.
After nine years at FJ, I was offered an exciting position at GeoGlobal Resources (GGR), in Calgary. I moved companies because I wanted to increase my experience and be hands-on in deep water exploration, even though I really missed working for FJ. My focus at GGR was on their East Mediterranean and Indian assets. Here, I coordinated and managed multiple exploration license blocks, requiring regional and prospect mapping to generate probable reserves estimates for acquired acreage. We generated field development plans for an exploration project with a very large drilling budget. I was given an opportunity to quality control pre-stack depth migration (PSDM) processing on deep water prospects below a thick Messinian salt, resulting in greater than 90% depth accuracy at target level. This was an amazing opportunity, not only in terms of the technical experience I acquired, but also because of the people I met and worked with from all walks of life. Working in Israel and working closely with our partners was something I could not have even imagined. What an adventure – I absolutely loved every minute of it!
From there, I moved to Husky Energy, in their heavy oil thermal business unit. This was quite a challenging and interesting position. Many of my colleagues and management were disillusioned with the concept of 4D seismic analysis and didn’t believe it added any value. I knew that something completely outside the box was required to succeed in this role. Educating the non-believers and selling a “new” solution was the most challenging task, as this involved selling the solution to the powers above me, and to my peers. At Husky, I provided geological and geophysical technical support for multiple programs and prospects to facilitate investment decisions to improve oil recovery. I also promoted the use of advanced geophysical techniques and shared innovative knowledge through presentations to senior management and multi-disciplinary technical forum groups. Accordingly, I was honoured to be given the designation of a Subject Matter Expert in Geophysics.
On one of Husky’s SAGD projects, I initiated and successfully implemented an innovative time-lapse (4D) model for SAGD reservoir management to identify and predict steam chamber development, resulting in maximized recovery rates and optimized well placements. This time-lapse workflow was developed within the Jason Geoscience Workbench by the R&D team in The Netherlands. I worked closely with them to test it on a “real” dataset. The results from this study and the deterministic pre-stack inversion helped in providing a better understanding of the reservoir and, in turn, the integration of all the new information helped increase production 5-fold over three years. From my perspective, Husky was a real technical success on many levels!
After leaving Husky, I joined a start-up oil and gas company, Axial Exploration, and currently hold a seat on the Board of Directors. Here, my role involves advising and guiding the executive management in the strategy and direction of the company.
In your early school years, were you always interested in science? Did you know you were headed into science?
Yes, my skill set was more in sciences than arts. I took various courses to determine my strengths, which were in biology, chemistry, mathematics, physics, and believe it or not, psychology. At one time I thought of being a doctor and then specialising, but the length of the program put me off straight away! I knew I wanted to work with people in an office environment and where I might get the opportunity to travel and work with people from different cultures. I researched a few other disciplines but, in the end, settled for geophysics.
What differences in work culture did you perceive from the companies that you worked with?
The work culture was very different between the first three companies and Husky, not only from the perspective of the nature of the business, but because all four companies were from different countries. In terms of working for a service company, in my opinion, one tends to have a broader vision for solving problems. I personally found that working in a large oil company, there were more constraints with respect to introducing new concepts and ideas for geophysics. The main role at an oil company is to acquire seismic, process it, interpret it to produce structural maps and well locations and run a few attributes on the back of it. The geologists in some business units may or may not use the seismic interpretation trend in their geological model. Integration is something that really needs to be encouraged.
What continued to inspire you in your jobs?
Learning all the time and discovering how the disciplines tie together. I am passionate about reservoir geophysics. I was always looking at applying new technologies and coming up with new ways to solve problems. I like “thinking outside the box” and not having cookie cutter recipes to follow and apply to every project. I believe most of the large reservoirs have been discovered, and now we are dealing with complex reservoirs. Something different and unique is required to be successful. The companies I worked for encouraged the freedom to think and apply new technologies and workflows. This contributed to the success I had working on the different projects.
You have had a successful career in the industry. Can you distill the essence of your experience and tell us how you see it?
I think it was important to get some experience in seismic processing, even though I did not want to spend my entire career in this area of geophysics. This helped me in my later years when I had to oversee the processing of seismic data, and in identifying processing problems for interpretation and seismic inversion. The majority of my career was in reservoir geophysics. There is so much more we can do besides structural interpretation and generating seismic attributes for exploration, development, and production. I believe QI is essential. In simplistic terms this entails extracting rock properties from seismic inversion, then making predictions about reservoir properties such as lithology, porosity and fluids. This can be applied in characterising thin reservoirs, understanding complex geological systems, delineating hydrocarbons left in place, 4D seismic analysis, etc. In the end, the geological model dictates well placement. Technology has come a long way, and I don’t just mean incorporating structure maps into the model. The rock properties extracted from seismic can also be integrated into the model, along with the probabilities calculated from rock properties.
What have been your aspirations as an exploration or development geophysicist?
It is important to utilise all the tools available, to be successful in your objectives. Thinking outside the box is a brilliant skill that needs to be applied regardless of the project at hand. What I aspired for was to be the best at whatever I chose to do. Looking back, I can say that I am happy with the technical and economical successes I have had, whether it was wildcat drilling of deep wells off the coast of Israel; consulting for other offshore plays, which started off as exploration and led up to the development of the field; and lastly, contributing in reservoir characterisation studies to help other professionals in achieving their objectives.
What accomplishments are you most proud of?
I can think of many!!
I am proud of the new 4D seismic analysis workflow that was tested on a SAGD play, that helped to increase production 5-fold. This really was a technical success. Also, the results from the simultaneous inversion on the same play increased our understanding of the reservoir. The outputs of these processes were integrated into the geological model successfully, which the reservoir engineer used for reservoir simulation. I truly believe the integration of all disciplines was the reason for the success of this play.
I am also quite pleased at being involved in the drilling of two wells off the coast of Israel. Not only were we responsible for the technical aspects of the project, but also in helping investors understand how the whole process works and the risk elements involved. Effective communication was vital to this role due to their inexperience in oil and gas exploration – this was their first project.
Having mastered the Jason Geoscience Workbench, I think for anyone, is a huge accomplishment, and also being involved in testing new ideas and methodologies on real data. Moving from a technical role to a business development manager was quite the challenge, and I really did not think I would have the ability for sales and marketing. A piece of advice to my fellow colleagues is that, if given an opportunity that may be outside of your current skill set, please take it. Doing something different might uncover hidden talents!
I absolutely love my new role on the Board of Axial Exploration.
Your career is far from over, but looking back, would you do have done anything differently?
No, I wouldn’t want to change anything in terms of my experience and the opportunities that landed in my lap. I just wish I had more time to work on the blocks GGR had in India. The plays were very challenging.
In my opinion, multi-disciplinary teams still do not recognise the benefits of geophysics, namely reservoir geophysics and quantitative interpretation. When I worked for FJ, it took a lot of patience and effort to prove to oil company senior management the advantages of applying advanced geophysical techniques to understand their reservoirs more fully. I also believe 4D seismic analysis should be common practice these days. I would love the opportunity to advise the decision makers of oil and gas companies as to the geophysical processes they should invariably follow before they drill wells, and of course, the processes would have to be tailored to each basin.
What geophysical techniques have you incorporated into your interpretation for exploration/development of hydrocarbons? Of course, that would depend on the objective at hand, say delineation of thin sandstone reservoirs, determination of porosity zones, reservoir compartmentalization, etc., but you could cite some instances?
The starting point is of course, structural interpretation and the use of seismic attributes to give you an initial understanding of the geology. The next step that I would take would be to cross-plot seismic rock properties (i.e., P-impedance, density, S-impedance, etc.) from the logs to see if inversion will work, whether post-stack, pre-stack or geostatistical inversion is needed, and if one can characterise the reservoir based on the seismic resolution. Post-stack inversion only yields acoustic impedance. The pre-stack or simultaneous inversion algorithm I have experience with uses full Zoeppritz equations and sparse spike methodology with sophisticated low frequency modeling techniques to quantitatively integrate well log elastic rock properties and AVA seismic to produce calibrated, quantitative rock property volumes. This method simultaneously provides key reservoir properties P-impedance, S-impedance, density, VP/VS, λρ and μρ, through the inversion of partial angle stacks.
The requirement for density estimation this way is that seismic data should have been acquired with long offsets, which then translate into larger angles of incidence (greater than 40/45 degrees). Even when density is determined this way, seismic interpreters remain skeptical about the accuracy of such density estimations due to the deteriorating signal quality and the increasing residual noise level on the far traces. Density determined from multicomponent seismic data is expected to be superior, as the requirement on long offsets or large angles of incidence is relaxed when joint PP-PS impedance inversion is performed.
Once you have extracted seismic rock properties from deterministic inversion, you can then make predictions of the reservoir properties such as porosity, lithology, and fluids, and can get a more accurate visual on reservoir compartmentalisation. You can take this one step further by estimating rock and fluid probabilities from, for example, the P-impedance and VP/VS results from inversion. This process uses Bayesian inference to determine the probabilities of occurrence of geologic facies from seismic properties.
In order to delineate thin reservoirs beyond the seismic bandwidth, geostatistical inversion would be the method I would use. Geostatistical inversion is a technique that simultaneously incorporates all field data, including well logs, core, and seismic into an analysis that results in multiple, highly detailed and realistic models, each of which honours all data known about the reservoir. These models are built from pre-stack or full stack data, are accurate near and away from wells, have realistic detail beyond the seismic bandwidth, and together provide more accurate estimates of uncertainty and bias, than other methods. The models produced are typically lithofacies, porosity and permeability models. The geostatistical inversion method that I have experience with uses an algorithm known as Markov Chain Monte Carlo (MCMC).
You have led a multi-disciplinary team involved in quantitative interpretation (QI). A couple of questions here. First, what do you think are the essentials of a good manager, and second, what were some of the workflows adopted for QI aimed at addressing specific objectives?
The most important traits of a good manager are to have open and honest communication with your team, be an active listener, be flexible/adaptable to the business needs, and be supportive. Building emotional intelligence is important, especially when you are leading a diverse and multi-disciplinary team. Every team member should feel respected and valued. It is important to help team members feel empowered by recognising their ideas, work and unique qualities.
Regarding the workflows for QI, at FJ, we had a process we followed for each study we were undertaking to see if inversion would work and what specific techniques would address the objectives. For example, if the rocks for a certain reservoir could be characterised by just P-impedance, then a prestack inversion was not run. This was the case on some of the carbonate plays.
You have spent a fair bit of time playing with stochastic and deterministic pre-stack impedance inversion. The main workhorse for such inversion is simultaneous inversion, and stochastic inversion is attempted only for specific projects where multiple realizations are desired. Could you share with us your impressions about these applications, and tell us where the latter scenario is mostly desired?
Yes, I have used both types of inversion on many projects. As we know with seismic data, we are working with interfaces. Seismic inversion is the process of transforming seismic reflection data into a quantitative rock-property description of a reservoir. The first step in any inversion process is to determine if you have enough separation of the rock properties, at seismic frequencies. If this step fails, then inversion is not going to add any additional information to your play. The second step would be to run a simultaneous inversion to understand the reservoir, which of course is at seismic frequencies, resolving the thicker bodies. I would then proceed to run a geostatistical (stochastic) inversion over the areas where one wants to delineate the thinner rock layers, and it can be run at well frequencies if required, however the uncertainty would be higher.
The geostatistical inversion I have experience with is within the JGW, where seismic and well information is used to run the inversion. Depending on when the solution converges, you can generate anywhere from 10-20 realisations. I have never had to generate more than 20 realisations on any of the plays I have worked with. The reason for multiple realisations is because it generates several possibilities of lithologic bodies of varying thickness. From here, one can calculate probabilities such as P10, P30, P50, etc. for thin reservoirs. With deterministic inversion, probabilities of the facies can also be generated.
I had the opportunity of attending one of your presentations on the economic benefits of seismic inversion and 4D analysis on a SAGD heavy oil play in Alberta. Please tell us about the challenges you faced in that project, how you addressed them, and the outcome.
I came into the project at a stage when oil production numbers from this field were at an all-time low. As mentioned earlier, I knew there was a new workflow that had been developed within JGW and this play would be the perfect test. Not only was this a technical challenge, but selling this concept to everyone involved was another thing altogether.
This new workflow involved updating the time-lapse low frequency model in a data-driven manner in time-lapse inversion. Details of this workflow can be found in the paper that was published in the December 2015 issue of The Leading Edge, entitled “Updating the low-frequency model in time-lapse seismic inversion: A case study from a heavy-oil steam-injection project”.
Looking at it in a simplified manner, the idea behind 4D in SAGD operations is that we record surveys over the same field during different stages of injection and production, to delineate steam effects. Since everything else remains the same, through subtraction, we can determine the changes in saturation and rock matrix of the reservoir, which in turn affect the seismic or acoustic properties. Time-lapse pre-stack inversion can be useful for quantifying production parameters such as temperature and pressure or the development and extent of the steam chambers. Rock physics modelling for building an accurate petro-elastic model is essential to the 4D process. The petro-elastic model basically mimics the reservoir conditions at the time the monitor survey was recorded, and encompasses the effect temperature has on seismic parameters, namely VP and VS. At this point, we integrate simulation results, seismic, and log data. The common fluid substitution model used in the industry is by Biot-Gassmann. However, in heavy oil, this is not valid because it assumes fluids are mobile. In heavy oil the bitumen or oil is solid, therefore for accuracy, shear, and density changes need to be considered. As a result, for this case study, the Ciz and Shapiro fluid substitution model was used. This petro-elastic model was then used for the low frequency component and for interpreting the final 4D results.
The benefits from this study were: a) 4D seismic analysis was able to illustrate the steam conformance along the SAGD pairs, b) it highlighted areas of low permeability in the reservoir, which will prevent steam penetration, c) it identified compartmentalisation and mapped permeability pathways, barriers and baffles, d) there was good correlation of the 4D results with measured field data, e) it allowed a better understanding of the reservoir’s behaviour for future well placement, and f) it provided insight to the operating strategy for some of the wells.
How was your experience during characterization of the Duvernay? Did you make significant use of seismic data in that work for understanding the formation better and for optimum future well placement? Please share with us whatever you remember for that project.
Again, my go-to technique would be running a deterministic and/or geostatistical inversion. Here, you would want to understand how seismic rock properties relate to Young’s Modulus and Poisson’s Ratio. What you are trying to highlight in shale plays is the brittleness of the rocks. Lambda-rho and Mu-rho is the domain I would use to analyse the Duvernay, as a starting point.
In the past, a commitment to learning was a desirable personal trait, but gradually it was realized as a necessity for career growth. There is also an awareness that the best training and finest credentials depreciate, if not continuously updated. How much time and money do you feel a company needs to devote to technical training of its employees?
I think the company should invest in routine technical training and the development of an individual’s soft skills. As the business environment grows more competitive, it is important to improve your employees’ performance in a dynamic marketplace. Employees are a business’s most valuable asset, and investing in their career growth is critical in a company’s long-term development and success.
Did you ever get involved in volunteer work?
I was an Executive Member of the CSEG Doodletrain, Recorder and Luncheon Committees, the CSEG Executive Committee Director of Communications and the Secretary for the Chief Geophysicists Forum. I have also been involved in APEGA’s Mentorship program since 2017.
Outside of industry, I am an avid supporter of breast cancer research. I was involved with an NGO called The Calgary Circle which is affiliated with Annie Lennox’s The Circle NGO out of the UK, for the prevention of human trafficking.
What hobbies and pursuits do you enjoy outside of work?
My favourite pastime is going for long walks daily with my two dogs. In addition, I love hiking, swimming, reading, entertaining, and travelling. I enjoy cooking and trying new recipes, but I always like to add my own little twist. I have become quite creative with my recipes! Now that I have more time to pursue other interests, I have taken up winemaking. I created my own label called ‘“Hers”, Timeless, Elegant, and Inspiring’. I have completed the first level certification as a sommelier, which takes a few years. Hopefully I will get to complete the whole program. I have also realised that I have a talent for painting!
What words of advice would you have for fresh talent about to enter our profession?
Work in a lot of different areas of geophysics to see what you like the best. You will come across many challenges throughout your career. Be true to yourself and your values. Work hard and learn as much as you can, not only about geophysics but also other disciplines, as integration is key to success. It is important to develop soft skills and be a team player. Strive to be ambitious without forsaking your principles. If you are unhappy with the company culture, then move on, because a toxic environment is not a healthy place to work. Lastly, try and get some international experience to become a well-rounded professional.
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