PhD opportunities

Seismic subsurface monitoring: impact of the processing steps in the context of a light but continuous monitoring

Thesis proposal

Area of expertiseGéosciences et géoingénierie
Doctoral SchoolGéosciences, Ressources Naturelles et Environnement
SupervisorCHAURIS Hervé
Research unitCentre de Géosciences
ContactHervé CHAURIS
KeywordsEnergy transition, continuous subsurface monitoring, seismic imaging, geophysics
AbstractIn the context of energy transition, subsurface plays an important role for the resources as well as for possible storage solutions. Continuous monitoring is an essential element for a better control, typically for gas storage or CO2 sequestration. Traditionally, a first and dense seismic survey provides a static image of the subsurface. It is very expensive due to the large number of shots and receivers. Different alternatives have been developed for the monitoring part:
1. Repeat the same acquisition, typically only every 2 years for economic reasons;
2. Analyse seismic ambient noise, but receivers should still be deployed and the seismic source cannot be controlled (frequency content, azimuths);
3. Develop a light system, as proposed by SpotLight Company: depending on the expected 4D effect, the initial seismic image is analysed to determine where to position the most pertinent source and receiver pairs. This solution allows a monthly monitoring.
Applications to real data, including blind tests, demonstrated the attractiveness of the method. However, it is essential to quantify the impact of the different processing steps on the final result. Currently, the analysis is based on rays, a simplified physical approach.
The main objectives of the PhD thesis are:
• Quantify the impact of different parameters on the final result. For example, the image used to determine the best source/receiver pairs could be a structural image (standard approach) or a quantitative image (least-squares iterative result). The associated spatial resolutions are different and should be evaluated; along the same line, create a quality factor associated with the seismic images
• Demonstrate how to extend the current approach to a full-wave approach that takes into account finite frequency effects;
• Apply the techniques to synthetic and real data sets, with a strong industrial impact;
Organisation of the PhD thesis:
• Bibliography study of seismic monitoring techniques (passive and active sources), study of the compromise between dense acquisitions but infrequent versus sparse but frequent acquisitions [3 months]
• Impact of the migration (i.e. standard migration versus quantitative migration) on the selection of the best source/receiver pairs. Recently, Mines ParisTech has developed a new quantitative migration scheme for the same cost as the standard approach. This tool will be evaluated for the first time in the monitoring context [12 months]
• Applications to real data sets [6 months]
• Impact of a full-wave approach versus geometrical (ray-based) approach to take into account finite frequency effects [7 months]
• Application of the full-wave approach for real data sets [4 months]
• Final thesis writing [4 months]
ProfileThe candidate should have a strong background in maths and physics. He/she should have a clear interest for geophysical applications, in particular in the context of seismic imaging. He/she should have a strong experience in scientific programming. It is essential to be fluent in English (speaking and writing). He/she will spend time at Mines ParisTech and within SpotLight Company.

How to apply
Candidates must contact the director(s) of the thesis proposal or the contact person specified. The latter will then hold auditions and select the most suitable candidate for their project.
Content of the application :
-a CV
-a letter of motivation
-transcript of marks of Master 2 (or equivalent)
-summary of the Master 2 report (or equivalent)
-Letter of recommendation from the Master 2 internship supervisor (or equivalent)
FundingConvention CIFRE