Weimin Zhang is an experienced geophysicist in the Canadian oil patch. Having joined PanCanadian in 1996 after finishing her Masters at UBC, and later remaining with EnCana and the spinoff Cenovus, she has dedicated more than 16 years to her profession. This includes over 12 years direct experience in the oilsands, where she has developed the expertise of applying the geophysical/geological technologies to the Christina Lake oilsand operations. She has gained hands on experience in Crosswell seismic, 3C-3D, 4D, VSP, geostatistical modeling and AVO inversion besides many other interpretation techniques. In particular, Weimin is known to have initiated the application of AVO/LMR technology to both clastic and carbonate plays and went on to develop several favourable drilling prospects and lowering exploration risk. She has proved to be a good team worker and has also gained prominence as a good team leader. She has struck an admirable balance between her productive geophysical career and personal activities that involve her family, friends and her service at the local church. On being approached for this conversation, Weimin agreed without hesitation. She is warm, polite, and full of energy. Following are excerpts from the interview.
Weimin, I would like you to speak a little about your educational background and work experience.
I did my undergraduate study in Exploration Geophysics in China and obtained my M.Sc. degree in Geophysics from the University of British Columbia. I was accepted into a Ph.D. program in the United States at the same time I was offered a summer job with PanCanadian. I accepted the summer position and enjoyed the work and the people so much that I decided to continue to work in industry and pursue a Ph.D. later when I became bored (it seems I have never got to that point). I began working at PanCanadian in May 1996 which later merged with AEC to become EnCana. I began working with Cenovus Energy in December 2009 at the time of the split with EnCana.
You got a Bachelors degree in geophysics from Chengdu Institute of Technology, China in 1992. Could you tell us how you decided to get into geophysics in the first place? What was the defining moment in your case?
My father belonged to almost the first generation of geophysicists in China (he was a physicist and began to work as a geophysicist in the oil fields in 1952). I was exposed to seismic data and velocity analysis when I was about 12-13 years old. I have been interested in math and physics since junior high school. Unlike many girls at the time, I really enjoyed and felt these subjects were easy for me so I performed very well. But I was not sure if I should study theoretical physics or applied physics in the future. At home we had lots of books related to earth science and geology and my father often taught me about it. So I became fascinated by the combination of physics and earth science (which is geophysics) around grade 11-12.
In China, national examinations are held for the entrance into university, and students are given a school list to decide where to go. My teacher was very surprised to see that I selected the College of Geology instead of the more famous universities in China. He asked me to reconsider. Without any doubt, I just thought those wiggle traces were so cool and found it amazing to use them to see rock, oil and gas. I also thought that geophysics was more practical and more useful than theoretical physics or mathematics. It could be used to help find hydrocarbons and contribute to China’s development. Looking back, it seems like a decision strongly influenced by my father but I believe it was a good decision because I have enjoyed doing it everyday.
How did you decide to come to Canada?
When I was in the 2nd year of my undergraduate program, I had some high school classmates attending school in the United States who wrote to me about their great new experiences studying abroad. So I researched information and started the application process for graduate school in North America. By the time I finished my 3rd year, I received acceptance letters from both UBC and the University of Texas for graduate study which would be fully funded for study and living. I did not know where to go. It just so happened that my father’s friend had just visited Canada and told me that Canada was far more beautiful than the U.S. I saw some amazing pictures of the Rocky Mountains and great fall colors in Ontario. I was also fascinated with my supervisor’s, Dr. Ron Clowes’, research on deep seismic to probe the earth’s crust and understand its geological evolution. My undergraduate study in China was exploration geophysics focused on oil and gas. So I decided to come to Canada for an M.Sc. program to open up my mind and then go to the U.S. for Ph.D. studies continuing in exploration.
So, as you were doing your masters at UBC, you worked part time as a processor of Lithoprobe data? How was that experience?
I worked part time for Lithoprobe as my supervisor Dr. Clowes was the director of this National geosciences project. I really enjoyed that work experience and it opened my eyes to the science. I went on a few field trips with other colleagues at Lithoprobe to collect wide-angle reflection and refraction data in Canada and the U.S. I remember there was one huge profile from northern Manitoba to Texas. All of the seismic data was used by graduate students and scientists at the Geological Survey of Canada and the U.S. Geological Survey to study the evolution of the continent. The Lithoprobe seismic data I processed and interpreted has the zone of interest around 6 seconds, with complex structures.
I wrote some programs, like DMO and Karhunen-Loeve transform, in ITA software and customized the algorithms based on the geology and data quality I was working on. I input those programs into our own software library. I was very good and very fast at writing codes. When I was working on Lithoprobe data I found it was so noisy that its interpretation was very challenging. Because of this, I gained great skills in combining seismic data and regional geological studies to understand the subsurface. From Lithoprobe to industry seismic data, I got a broader view of reflection seismic. So I am not afraid of working on “ugly” data.
I remember when I joined Christina Lake oil sands in January 2001 (oil sands was not popular for geophysicists at that time, compared to today), I was told by quite a few geophysicists that this kind of seismic data was not workable because of the noise and lack of strong reflections due to unconsolidated sands, but I always believed that it is possible to pull the geology out of noisy or complicated data due to my experience from Lithoprobe.
In 1996, you joined PanCanadian, which later became EnCana and then Cenovus spun out of it. So you pretty much stayed at the same company. How do you think it has turned out for you?
Everyone is different. Some people like to go to a different company after 5 years. I am very grateful that I was hired by PanCanadian, starting with great training programs and working with great technical people. During the EnCana and Cenovus period, I worked on oil sands assets. Because oil sands is one of the company’s focuses, we receive a budget that permits us to acquire seismic which can be used to help drill vertical strat wells and horizontal production wells with great success. We have lots of oil sands projects with different challenges, and I could transfer from one project to another. I can continue to learn new things and face new challenges every day in the same company. I have received calls frequently from other companies, especially for oil sands projects. I feel Cenovus has a very good work and life balance and I am part of a great team right now. I have worked with many great people in this company. There are too many people I have learned from to list them all. Some are still at Cenvous, while some have moved on to other places.
Who have been some of your mentors?
I was hired by Andrea Kubik and she was my mentor for a month before moving to a management position. Then Dave Mackidd joined PanCanadian and became my mentor. I did lots of AVO modeling on the Nisku in southern Alberta with Dave’s guidance. He taught me many interpretation techniques and taught me how to challenge geologists. Dave is a creative interpreter. When I found that Landmark software was not good enough for my interpretation for a subtle Nisku play, we wrote a new program together for horizon extrapolation. Bill Goodway was my major mentor in the PanCanadian years. I had a lot of great learning experiences from him on both theory and application, in the areas of seismic acquisition and processing including modeling and inversion. I worked on LMR with him for 2 years. His dedication to each project really influenced my attitude towards work. Dave Cooper was our manager and chief geophysicist and gave me lots of direction on what projects to work on. He encouraged me to present LMR technology with Bill inside the company and for us to teach an in-house course on LMR and inversion to geophysicists, geologists and engineers. Dave taught me how to present, especially to non-geophysicists. I am still practicing. Dave is a great geophysicist who inspires and promotes the careers of young geophysicists. I am grateful to have started a great career in industry with PanCanadian.
What personal qualities do you think enabled you to achieve the professional status that you enjoy today? Is it hard work, ambition, or anything else? Do you also think you had a firm grounding in mathematical concepts that has kept you in good stead or is it something else?
I love geophysics and I don’t mind hard work. First of all, I feel you have to like what you are doing daily. Interesting work gets me into the door. Working hard gets my job well done. A firm grounding in mathematical concepts definitely makes my job easier. I don’t need to struggle all the time. It helps me to understand processing technology and helps me to feel comfortable using new technology, which helps contribute to successful drilling.
As it is usually said, North America is the land of opportunities; youngsters come and are game for hard work. Do you think this is true in your case as well? When it comes to hard work, some individuals do believe that taking time off or holidaying is like a hurdle in their race against time. What is your belief on that?
I was sometimes a workaholic in the past. Now I try to maintain a good balance between work and life. I guess we all mature as we age and we begin to realize there are lots of other important things in our life. Success in a career is very important especially for many Chinese (it is in the Chinese culture); however, family is more important. I do feel efficiency is critical for success. By taking time off, I can clear my mind, which helps foster new ideas when I return.
Tell me about Weimin, the person – your habits, your likes/dislikes, etc. …
I am patient in the workplace. I have the perseverance to finish a challenging task. I like to take action rather than engage in mere abstract thinking. I like to start something and finish with a good quality product. I like to be connected to others and I am an open and trusting person. I have many close friends and enjoy making new friends. I love people and care about other people’s needs.
If I were to ask you for your ‘off-thecuff’ assessment, how would you rate yourself on a scale of 1 to 10, in terms of (a) communication skills, (b) willingness to admit mistakes, (c) extempore speaking and (d) awareness about tricks of the trade?
- I think my communication skills are good. I could give 8 out of 10. When I have an issue, I will thoroughly think it through first and then not hesitate to talk to the team geologist, engineer, and technologist. I am able to get the idea across clearly to my colleagues and listeners. I think I am also a very good listener which is an important part of communication.
- “It is not my fault” is a prevalent attitude in our culture. But I don’t feel bad in admitting mistakes as we are all human. I learn from each mistake. Quite often, I spend time reflecting on why I made the mistake and how I can avoid making it the next time. I am honest with geologists and engineers with what I can see and my limitations. If we drill a bad well, I will spend time determining if the seismic itself or my interpretation made the wrong prediction. I will admit if I made a mistake. I had a poor drilling success rate in my first year at PanCanadian. However, I didn’t hide my mistakes to the geologist. I studied very hard and had great success in my second year. I give 9 for that.
- I am not good at speaking on my feet. It could be partially because English is my second language. So I give myself 4.
- I try to stay current and constantly check for updated technology through reading in my spare time. For each new play or project, I usually talk to the geologist and engineer first and then read some papers to determine the most important areas where I can contribute with geophysics. For example, when I worked on the Christina pilot, I knew that the thin mud and mudstone interbeds could act as baffles or barriers to the growth of a steam chamber. Then I spent most of my time studying how to get high resolution seismic and paid less attention to channel detection using spectral decomposition and inversion. So I know the importance of determining priorities and applying different technology to accomplish goals with each different project. I will give myself 9.
Tell us about your contributions to seismic interpretation, as I believe that is what is close to your heart.
I could think about three aspects. One is technology. When I moved into a business unit to start my interpretation career after 2 years working in the processing group, I taught other interpreters using various software how to do log crossplots, seismic modeling, inversion, and looked at prestack gathers besides doing routine work on stacked wiggle traces.
Another part is about quantitative interpretation. The quantitative interpretation of seismic data for rock properties still poses a lot of challenges. I made a lot of effort to use seismically derived attributes to predict reservoir parameters, such as lithology and pore fluids, with a good amount of success.
The third aspect is integration. I believe the key to managing complexity and risk in an oil field is the effective integration of geology, geophysics and engineering. With the encouragement of Bill Goodway and Dave Cooper, I have been interested in the development of integrated workflows since I started at PanCanadian. I used various types of software to integrate geophysics and petrophysical logs, and in recent years I have integrated surface, borehole seismic and geostatistics. I have also worked with rock physics and have recently started with it again to integrate both the data and expertise of geophysics and geology for reservoir characterization.
What has been the most memorable moment in your professional life? Also, tell us about some of the successful landmarks in your geophysical career.
With Bill Goodway’s concept of LMR, I developed a crossplot workflow inhouse in 1997. I also made a “mudstone line” by using some combinations of “Lambda-Rho” (lr) and “Mu-Rho” (mr). Actually in 1998, I had a great case study, which I couldn’t publish. It is the result of my creative and hard work, guidance from Bill Goodway and many other people’s help. PanCanadian said it was “too good to publish externally”; because they wanted to encourage similar work from other geophysicists within PanCanadian before the results became well known. The VP Exploration showed the results to the President, to emphasize the importance of the method and results. Dave Cooper encouraged me to initiate the application of AVO/LMR in PanCanadian on many projects for about 4 years. I had focused on it and had great hands-on experiences with AVO and inversion.
Another landmark was my involvement in acquisition and processing of crosswell seismic. At that time in early 2001 everything was based on reservoir simulation because there was not a great deal of production. My interpretation of crosswell seismic indicated that the growth of steam chambers was being stalled by thin, laterally continuous mudstone and showed the steam chamber movement around the IHS (Inclined Heterolithic Stratification) facies. I used unconventional seismic data to understand reservoir heterogeneity and to obtain information for the prediction of unswept reservoir zones.
Combining crosswell and 3D seismic data, and integrating that with geology and reservoir engineering really provides new insights into reservoir architectures and their impacts on SAGD performance. The early work and sound understanding of the reservoir at Christina Lake helped make it a successful project today. In our first profile, we reached a frequency of 1000 Hz, which made it possible to see mud barriers as small as 50cm, the geometry of IHS, and a very small fault on the Paleozoic surface. I basically interpreted seismic as log scale with such high frequency. However in 2001, the piezoelectric source we used generated from 100 to 1000 Hz, without any lower frequency. The data looked very ringy and quite different than regular seismic. I feel grateful that Guoping Li, who worked in Christina Lake before my time, helped me interpret the first profile. Later, I continued to encourage the contractor to further develop the tool and they developed the EX source that had a lower frequency of 20 Hz. The receivers also developed from fluid-coupled hydrophone receivers to three-component multi-level receiver arrays deployed in the dry well.
What influences you and your work and what are your aspirations for the future?
Curiosity gets me started, but looking for the “truth” in the subsurface drives me in taking the extra steps to work on data. The earth is created perfect and complicated. Subsurface geology is amazing and I always want an in-depth understanding. I believe it is understandable to a certain degree with technology and we need to take some risks. During the stage of monitoring production, it has to follow the principles of physics, like gravity, pressure changes etc. It is fun to observe this.
I don’t simply come to work to earn money and social status. I get excited when I am close to the right answer by checking the drilling results, temperature data and etc. I think that’s probably true for many interpretation geophysicists. I enjoy working as part of a team with other geoscientists and engineers to figure out problems and accomplish goals. As for oil sands, I have been learning a lot from engineers. I am glad I could make contributions to the team and help others.
I believe geophysics is still very valuable even though the amount of exploration work has been reduced greatly. When I first joined Christina Lake we already had more than 30 wells in this section which I was going to work on. So team members were unsure what a geophysicist could bring to the table. After the first year I was glad to hear one of the geologist’s compliment, “Without Weimin’s geophysical work, I can’t drill the well.” I believe in the near future we could be more confident in quantifying reservoir properties and predicting reservoir parameters through the application of rock physics. I plan to focus on this work in the next few years.
I also hope I can be more involved with teaching or mentoring in the future.
There is a certain amount of creativity that is required for doing effective seismic interpretation. Do you agree with that statement?
Yes, I agree with this statement.
I think a seismic interpreter is like a detective. We have to put together many pieces of information. I also think that the ability to integrate is very important for effective seismic interpretation. For example, in reservoir monitoring interpretation, I have to combine all kinds of data together for the most reasonable answer.
Do you think many seismic interpreters lack creativity? What is required to be creative?
Many seismic interpreters may lack creativity today but not because of the lack of the ability to be creative. I think there could be two reasons for this.
First is the lack of time to think. In order to be creative, you have to have enough time to focus on the project and think back and forth. It is not common to have a lot of time to think and figure out innovative ways or non-routine ways in our daily work. Second is the lack of new skills. Now many of us work on oil sands and unconventional resource-plays. It requires new skills beyond the conventional geophysics toolkit to be creative. In the past, we just tied lines and picked horizons, so our creative solutions may have been to find new ways to tie phase and amplitude better, or to create better maps. Now we work with engineers and we have to figure out oil saturation, probability, etc. Inevitably, we have to update our skills to be creative.
You got well versed in applying AVO/LMR technology to clastic and carbonate plays early on in your career. How did this application pan out for you?
As I said earlier, I worked with Bill directly for 2 years on LMR then I continued to use it on my own.
I once worked on a project in southern Alberta utilizing LMR. I submitted the paper to the CSEG in January 1998. In that paper I used LMR inversion and found a way to link log and seismic crossplots. I could separate porous and less porous sand from seismic crossplots with the integration of logs. It was a challenge for quite a few years to separate lithologies using 3D seismic amplitude. I am very proud of my successful application of the technology to solve the real problem.
I presented my work to our senior management. They were all amazed by the seismic result but firmly stated that I couldn’t publish it. Unfortunately I had to call the CSEG to withdraw the paper the day before printing.
Today, I have experience in many different areas. If the log analysis and forward modeling indicate the separation of lithology and fluid from LMR space and we have good data with enough angles, we should achieve lithology discrimination and fluid detection.
My experience with AVO/LMR has strongly led me to the integration workflow of geophysics and geology i.e., by combining petrophysical logs, seismic and core analyses all together. That’s really another great benefit.
I am convinced that LMR technology is a viable means of characterizing reservoirs since I have used it on many projects with a high level of success. When the quality of data is sufficient, I make use of it for both exploration and development. When the gather quality is poor, I have to be very cautious when using this technology. Some people may feel they could just look at gathers and that it is not necessary to use Lamda-Rho, Mu-Rho. I find that inversion results are able to highlight very subtle details than I could not see by eye.
You have been actively involved in the Christina Lake Oilsands project, both its pilot and development phases. Tell us about the project and what technologies you have pressed into service to characterize the McMurray oil sands.
Christina Lake Oil sands is a SAGD project. The main features of the SAGD model for the lateral spread of the steam chamber include thermal conduction ahead of a steady-moving steam-chamber interface, counter current gravity drainage of mobilized bitumen, or heavy oil, and vertical rise of the steam chamber. Field applications of the SAGD process have revealed several issues of considerable importance to recovery performance, including wellbore hydraulics, reservoir heterogeneity, effects of solution gas, and the production of solids. As a geophysicist, my key contribution to the project is to integrate geophysics with geology and reservoir engineering, and to characterize the reservoir heterogeneity and further understand the steam chamber growth through monitoring in the McMurray reservoir. This helps in well placement, resolving production issues, and improving operation efficiency.
I have used 4D, 3C, zero-offset/walkaway/ 3DVSP, Crosswell seismic and Crosswell EM methods, along with many logging programs. I have also used geostatistical modeling to compare with seismic observation. For data analyses I have used inversion, neutral network and spectral decomposition, etc.
When the SAGD pilot was implemented in 2001 at Christina, we had six SAGD well pairs along with observation wells, disposal wells, and were applying all the technology above (at that time, it was world-class geophysical dataset for a quarter-section of land). I am very fortunate to have worked on the project, investigating the reservoir heterogeneity and monitoring the production performance, until 2007.
There is a limitation for each technology. I used them collectively and made a significant contribution to future development planning based off key learnings from the pilot.
Apparently, 4D seismic is being used for reservoir monitoring now. Tell us about the success of this project and the development strategies.
The use of 4D seismic technology for reservoir monitoring has found widespread application within the last 15 years for various reservoir processes, including those involving steam injection. In these cases, analysis of the time-lapse seismic results has enabled an understanding of steam-chamber growth (or lack thereof) and/or steam conformance along the wellbore, and has in many cases resulted in reservoir management decisions which have had a positive effect on production.
Not all recovery processes are suitable for 4D monitoring. Changes in the reservoir have to be large enough to be differentiated seismically at a given seismic resolution.
Our 4D-seismic data demonstrates strong seismic amplitude anomalies around all the horizontal well pairs because of a large decrease in impedance. The steam-chamber effect is well reflected on the 4D seismic data. We observed both vertical and lateral steam chamber variation through 4D, which tied perfectly with observation wells and was consistent with flow-simulation results. Irregular steam chamber growth could result from either the presence of undetected flow barriers in the reservoir or undetermined operational issues. Unfortunately, the surface 4D seismic did not provide sufficient resolution of reservoir lithologies to unequivocally determine if geology was the major contributor to the lack of steamchamber development. It was clear that another technique with higher resolution had to be found. So I have to use crosswell and geostatistical modeling to compensate for the resolution limitations of 4D in order to estimate the vertical and lateral extent of mudstone drapes, IHS, and their impact on production.
After all these years of development, 4D seismic has become a routine program for many companies. Consistent acquisition is still very important, although the data processors have many creative ways to fix problems.
What has been your philosophy towards your professional growth?
I like to understand the basics by taking courses and reading books. I always like to build a strong foundation first then learn step by step. At the same time I will try to learn skills from geologists and engineers by going on field trips and taking reservoir engineering courses for non-engineers. For interpreting geophysicists, I think we really need a broader skill set for solving real problems. I also spend time communicating with university researchers. I have been in touch with Stanford University Rock Physics Program researchers for the last 9 years. We discuss their lab results, rock physics modeling, and inversion. It really challenges me to think more deeply and broadly.
What are your other interests?
I enjoy traveling and experiencing different cultures. Every year we go somewhere in Europe and just stay in one small village to experience the life of the locals. I really enjoy hiking in the mountains and seeing the beautiful lakes and wild flowers. My husband and I go hiking almost every weekend in the summer to promote a healthy body and mind. Recently, we also started enjoying cross-country skiing.
My husband and I are active with a Chinese community church. We spend our spare time organizing events, leading one group, and helping new immigrants from China. It is a big reward to help others.
What would be your message to young entrants who have just taken up geophysics as a profession?
I often find many young entrants think they know everything. I think confidence is very important but you must keep in mind that there are lots of approximations in theory and its application. I would like to remind them to know what you can deliver and know your limits. When we are young, we don’t know what we don’t know! It is good to ask many questions to the senior geophysicists and always try to be a good listener. Also keep an open mind to new technology and be willing to try new ways to solve problems. We often have support staff on our teams but I feel it is great in the beginning not to depend on technologists, but do things by yourself (i.e. get your hands and feet wet). Last but not least, do not be afraid of failure in the beginning of your career.