Inversion of seismic velocities using drill-bit seismic waves

Project description

The drill bit emits seismic waves that can be used for geosteering in real time. By analysing these data, we can reposition the drill bit, as well as detecting risks (e.g faults and karst) and geological targets ahead of the bit. The data can be acquired on permanent reservoir monitoring (PRM) systems or on smaller ocean-bottom cables which are deployed during drilling. The drill bit emits a continuous signal that can be deconvolved in a similar manner as in vibroseis processing onshore, and the dataset coming out of the process is comparable to VSP data. One of the purposes of this dataset will be to update the velocity model during drilling. Map migration of interpreted geological surfaces using the new velocity information can improve the geological interpretation ahead of the drill bit. This is information that will be of great value for the operator during drilling.

The goal of the work will be to develop a work flow for estimating seismic velocity information and associated uncertainties during drilling. The workflow will be based on ray-based methods. In this project the absolute time between the drill bit and the seabed receivers is known.

The work is planned to consist of the following key elements:
1) Generate model data
2) Develop the workflow and test on modelled data
3) Try the workflow on real data
4) Use of machine learning in selected steps of the workflot

Proposed course plan during the master's degree (60 ECTS):

GEOV219 – Computational Methods in Solid Earth Physics (vår)
GEOV272 – Seismisk tolkning (høst)
GEOV277 – Signalanalyse og inversjon i geovitenskap (høst)
GEOV375 – Avansert anvendt seismisk analyse (vår)
AG-335 – Arctic Seismic Exploration (vår)

Prerequisites

BSc. in geophysics, mathematical specialization

External data

OCTIO will seek to make a real dataset available for the project.

Analytical work

The student will get access to software for seismic modelling, processing and interpretation.