Geophysics
Understanding Time-Depth Conversion
Time-depth conversion is a vital step in transforming seismic reflections from abstract time data into actionable geological insights.
The humble well-tie has cascading impacts on all aspects of field development.
Who needs a good well tie? We say, everybody! Everybody working with seismic, that is.
Seismic is an excellent tool for connecting the dots (ie. wells). It can map changes in the rock’s physical properties and structures that perturb the rocks, like folding and faulting. Seismic is a remote & non-invasive way to look for changes in a potential reservoir. When it comes to ground truth, wells are the only way to directly sample the rock. Through logging, observation at the wellsite, core, and careful picking of formation & zone tops, geologists are firmly grounded in the earth’s rocky reality.
Wells are also the best way to relate information from the well, measured in depth, to seismic, which is measured in two-way time (the time for the energy to travel down, bounce off rock interfaces, and travel back up again). Well ties involve matching geologic tops to geophysical time horizons. This is the best way to merge geology and geophysics to make a realistic interpretation of the subsurface. For more information on this process, check out this article.
A small step with a big impact
Getting a good well tie might sound satisfying, but it can also have huge financial impacts. That’s because seismic is used to plan wells and guide drilling, which are costly activities. To plan and drill a horizontal well (or multiple wells in a pad configuration), geophysicists must convert seismic from time to depth. Imagine telling a driller to drill to 500 milliseconds…that would raise some eyebrows! This means that seismic must be reconciled with the wells to guide the drill bit (a process called geosteering).
Failure to keep a well on its trajectory means fewer resources are recovered from the ground. It can also mean changes in the reservoir that can impact well integrity and safety. A great well can quickly become uneconomic if serious problems are encountered. A good well tie to seismic is the first step to mitigate this.
A solid foundation for deep insights
The story doesn’t end there. An accurate earth model continues to benefit geoscientists even after drilling the well. When all information is in depth, drilling and completion (everything that is done to a well to get it flowing) information can be combined with geological observations and seismic properties to better understand the rock. The more information we can gather and the more relationships between human activities, the reservoir, and well performance we can interpret, the better future wells will be. Both in terms of efficiency and dollars.
The humble well-tie has cascading impacts on all aspects of field development. From geoscience modeling to well planning to drilling & completions to data analysis, it all starts with the well tie.
For more information on SeisWare’s well tie process, check out our quick video or contact us for a demo.
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