American Oil and Gas Reporter - January 2015 - 113

TECH TRENDS
initial prestimulation reservoir properties, which are changing dynamically with each completed frac stage because of the presence of new fractures and changes in the stress field.
The outdated approach of building an overly simple 1-D or
3-D earth model, and then assuming the location of microseismic events can be determined accurately within that simple model construct, is simply wrong! New tools are addressing this oversimplification of a very complex real earth. These tools will enable real-time updates to the 3-D geomechanical model of the
reservoir as frac stages are completed, and will integrate the updated models into the microseismic experiment in real time so
that errors in event locations can be reduced, where appropriate,
based on the sensor geometry of the microseismic experiment.

FIGURE 3
Surface 3-D Image

3-D BSI Image

Joint Acoustic Imaging
One area of technology that offers great potential for improving geophysical data is the joint acoustic imaging (JAI) concept.
In many fields, the presence of existing wells creates the opportunity to collect 3-D borehole seismic imaging (BSI) data during 3-D surface acquisition using downhole geophone arrays. This
approach can allow the full-azimuth anisotropic data, Q factor
measurements, and 3-D imaging volume from the BSI survey to
be integrated into processing the surface 3-D, which can improve
results dramatically (Figure 3).
Where salt bodies are present, acquiring the BSI data in wells
adjacent to or inside the salt also can provide critical information about salt body properties and geometry. This process will
ensure that operators can build accurate and spatially-robust 3D earth models with full accounting of the anisotropic rock properties that are essential to 3-D depth imaging, geomechanical modeling, depth conversion, geopressure prediction, and reservoir simulation and other critical processes.
The power of the BSI imaging concept also can assist operators in achieving very accurate placement of horizontal wells
in thin reservoir targets that can dramatically improve well performance (Figures 4 and 5).
A logical extension of the JAI concept is to add potential fields,
including gravity, magnetics and controlled-source electromagnetics (CSEM), to the integrated-imaging workflow to produce
a joint wave field imaging (JWI) product.
The challenge for this exercise is multifold in that the industry has struggled to demonstrate that the lower resolution of most
potential field methods can add value consistently over the traditional model of using only 3-D seismic data.
One area where electrical methods may have the advantage
over acoustic methods is in monitoring fluid flow in the subsurface, because of the sensitivity of electric and magnetic (E&M)
fields to fluid flow. The E&M geophysical community still has
a lot of room to run with new developments that ultimately may

Integrating 3-D borehole seismic imaging technology in joint
acoustic imaging improves subsurface resolution.

FIGURE 4

C.V. Lime

Wellbore adjusted to
conform to new interpretation

New fault
»100' throw

Base Haynesville

Salt

Interpreting 2-D and 3-D borehole seismic imaging technology
enables wells to be placed more accurately.

FIGURE 5

Adaptive Management Change build angle and
land horizontal in
pay zone

New fault
identified with
»100' throw

As Drilled
Borehole
After WTI

Planned Well
Trajectory
Before WTI

2-D borehole seismic imaging technology in conjunction with
adaptive management while drilling improves final well placement.

JANUARY 2015 113
American Oil and Gas Reporter - January 2015

Table of Contents for the Digital Edition of American Oil and Gas Reporter - January 2015
