Automatic gather picking using a 3D horizon
For years, gathers have been too large (and slow!) to use in every-day interpretation. These days, we shouldn't think twice about turning to gathers to understand AVO and anisotropy. In this workflow, we show how to use a 3D (IL/CL) horizon to automatically pick an event through some gathers.
We’ll start by creating a new gather horizon.
In the horizon tab, create a new horizon and select Offset as the gather domain. If you don't select a gather domain, the horizon will not propagate across the gathers!
We will use this BaseRes_TWT horizon as a starting point for the gather horizon propagation.
We must check that the horizon and gather volumes have a common sequence, i.e. points on the horizon must land on gathers. When calculation errors are small, e.g. from 2D lines into 3D, Insight will automatically regrid to solve this problem. For gathers, Insight does not make the same assumption and the propagator will raise an error.
A quick review of our extents shows the IL/CL increments are different. We must translate this horizon to the same increment as the gathers.
We’ll use Regrid horizon operation to translate the horizon to the same grid as the gather volume. We don't need to set any interpolation or constraints. Save it as a new horizon.
With our horizon ready, let’s review the event in the gathers at the horizon intersection.
You can see there's an outer mute on the gathers. We created a 42 degree mute in the Mute tab, then ran the gathers through a Mute Gather process. Insight created this on-the-fly muted gather volume which is perfect for display and for propagation. The blue dot is where our IL/CL horizon intersects each gather -- sitting on a nice, bright peak.
Back in the Control Panel, in the Horizon Tab, we'll select the gather horizon, open the picking panel and set the Mode to Propagator.
In the propagator settings, we'll choose the muted gathers as the volume to propagate, and our regridded BaseRes_TWT as the seed horizon.
We click propagate and can watch the propagation in real-time. Since DUG-Insight is multi-threaded, as it propagates, we can review the pick on the map at different offsets, or change colours. Once the propagation is done, we can save it to the existing horizon.
By turning on the gather view Amplitude graph, we can view the amplitude of the event across the gather. Without the horizon, we would see the amplitude of a single time slice across all the gathers. With the horizon in place, we also see the amplitude across the picked event. The amplitude of the gather at the horizon is a better display -- it isn't affected by dipping events or residual move-out.
In this image, the amplitude at the horizon is in pink and the amplitude of the time-slice is in red.
In Map View, we can scroll through offsets to QC the horizon propagation. We can extend this pick using the manual tools, or use the propagator again with some new settings or additional seed points.