Downhole Seismic Source Inversion for Borehole Resolution

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Solution Overview

Problem

Conventional borehole seismic survey systems face limitations such as signal attenuation and loss of resolution due to the distance between sources and receivers, and are unable to provide comprehensive information about subsurface structural features, particularly rock properties and hydrocarbon content.

Innovation Solution

The use of a downhole seismic source, either controlled or microseismic, in various geometries like Reverse VSP to acquire seismic data that would otherwise be inaccessible with traditional surface-based methods, allowing for improved data quality and frequency range, and enabling the investigation of formations over long distances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If sources are located at the surface and receivers are placed in the well (conventional VSP), then the survey configuration is simple and easy to implement, but signal attenuation increases and resolution is lost due to the distance between source and receivers

Engineering Contradiction:

Improveseismic data resolutionVSAvoidsource-receiver configuration complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent inverts the conventional VSP configuration by placing the seismic source downhole and receivers at the surface or in different wells. This inversion reduces the source-receiver distance, minimizing signal attenuation and improving resolution while maintaining operational feasibility through modified acquisition geometries

Inventive Principle:

Principle #13The other way round (Inversion)

2Area of stationary object

If the distance between source and receivers is increased to cover larger formation areas, then the survey coverage area increases, but signal attenuation and loss of resolution worsen

Engineering Contradiction:

Improveformation coverage areaVSAvoidseismic data quality

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The patent segments the survey into multiple downhole source locations and receiver positions, allowing coverage of large formation areas through coordinated multi-point acquisitions. Each segment maintains short source-receiver distances for high quality data, while the collection of segments provides comprehensive area coverage

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from traditional 1D vertical source-receiver alignment to 3D distributed downhole source and surface/downhole receiver arrays. This dimensional expansion enables coverage of lateral extent while maintaining vertical resolution through spatially distributed measurements

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Loss of information

If conventional VSP techniques are used with source at surface and receivers downhole, then the acquisition method is straightforward, but portions of the formation surrounding the well remain invisible

Engineering Contradiction:

Improvesubsurface structural feature visibilityVSAvoidacquisition simplicity

Core Design Contradiction:

Loss of informationVSEase of operation

Solution Approach 1:

The patent introduces downhole sources as intermediaries that generate seismic energy close to the formation regions of interest. These downhole sources act as mediators that enable imaging of previously inaccessible zones by placing the energy source within or near the target formation rather than at the surface

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the spatial parameter of source location from surface to downhole positions. This parameter change fundamentally alters the illumination geometry, enabling detection of subsurface features that are invisible to conventional surface-source configurations while maintaining operational feasibility

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enhances the resolution and quality of seismic data, providing previously unobtainable velocity information and detailed insights into subsurface structural features, including rock properties and hydrocarbon content, beyond the limitations of traditional VSP techniques.

Implementation Method 1

employing a downhole source, such as a microseismic event or a controlled source, to generate seismic waves

Methodology Applied

Scientific EffectSeismic wave generation: Vibration

Implementation Method 2

recording data relating to seismic waves generated by the microseismic event at at least one receiver

Methodology Applied

Scientific EffectSeismic wave detection: Sound

Data Source

PatentUS10120093B2Methods for in-situ borehole seismic surveys using downhole sources

Publication Date: 2018.11.06 SCHLUMBERGER TECH CORP

AI summary

Methods for in-situ reservoir investigation by borehole seismic methods are provided using receiver(s) and a downhole source. The downhole source may be a microseismic event, and may be located relative to the receiver(s) in any configuration. The downhole source may also be a controlled source that is positioned in a reverse vertical seismic profile (RVSP) geometry with respect to the receiver(s). The methods may involve locating the receiver(s) in a first well (which may have any orientation, including vertical or horizontal), and locating the source in a monitoring well (which may have any orientation, including vertical or horizontal), such that the source in the monitoring well is positioned at a greater depth in the formation than the receivers in the first well.