Vertical Seismic Profile Tool
Used to correlate seismic data for accurate depth measurement of geological fractures
- Openhole or cased-hole data acquisition
Features and Benefits
The VSP survey provides a true depth calibration of the surface seismic data and is the best way to ensure time-estimated formation depths are correct. Studying the seismic wavelet, captured by the downhole tools, can give insight into the reflection and transmission properties of the formations. Correct correlation of the rock types, as measured by VSP in the well, to those mapped on a seismic volume, is one of the most useful interpretation tools. More complex analysis can yield much more data, which improves the structural, stratigraphic, and lithological understanding of the reservoir and even provides measured parameters to improve surface seismic data processing. VSP is the only logging method able to image formations many hundreds of feet below the bottom of the borehole.
The VSP survey provides the following capabilities:
- Recorded data can be processed to reveal formations ahead of the bit to identify deeper targets or over-pressure zones, for example.
- Distinguishes upgoing and downgoing wavefields that help to identify primary and multiple events.
- Reveals the location of fault planes, reefs, and pinchouts.
- Can determine reflector dip.
- Calculates amplitude versus offset and anisotropy values.
- Has higher frequency content than surface seismic for targeted imaging in 2D and 3D.
Weatherford offers three VSP tools, each with its own strengths. The simplest is the Avalon ASR-1, a high-temperature analog tool that can be run singly or in a two-level array. A gamma ray tool can be combined with either configuration for accurate depth correlation.
The Avalon Geochain™ tool is the digital version of the ASR-1 and can be assembled into an array of up to 48 tools. Primarily a VSP tool, it can be fitted with fixed geophone sensor cartridges to become a robust, microseismic monitoring tool suited for high-temperature wells. The Geochain tool can be tractored or pumped into horizontal wells. Used with rigid interconnect cables (RITC), it can be pushed into horizontal wells on modified coiled tubing.
The Sercel SlimWave™ tool array was developed under Weatherford guidance for microseismic monitoring. This slim, multilevel digital array is an advanced seismic tool capable of running up to 24 levels on any Weatherford wireline at sample rates ranging from 0.25 to 4 ms. It is also well suited for complex VSP, 3D, or walkway-type surveys where a multilevel array is required. Depth correlation is assured using gamma ray and casing collar locator (CCL) tool options. Intertool spacing of any Sercel SlimWave array can be customized to meet specific client requests. Tool spacing can be from a few feet (~1 m) to 330 ft (100 m) between sensors.
Intertool spacing of any of the three tools can be customized.