Page 227 - Fundamentals of Gas Shale Reservoirs

10

PASSIVE SEISMIC METHODS FOR UNCONVENTIONAL
RESOURCE DEVELOPMENT

Alfred Lacazette , Charles Sicking , Rigobert Tibi and Ashley Fish‐Yaner 1
2
1
1
1 Global Geophysical Services, Inc., Denver, CO, USA
2 Global Geophysical Services, Inc., Dallas, TX, USA

10.1 INTRODUCTION an important control on frac effectiveness, location, and well
spacing. Again, the nature and location of such interactions
The purpose of this chapter is to provide a concise introduction cannot be determined by pumping data and simulation alone.
and overview of passive seismic methods and practical appli­ They must be observed. In summary, effective frac design
cations of such methods for unconventional oil and gas work. and field development planning require knowledge of the
We do not intend to provide a careful mathematical treatment actual behavior of hydraulic fractures in oil and gas reservoirs
of the subject or a comprehensive, thoroughly referenced deep in the subsurface. Interactive control of hydraulic
review of the field and its history. Rather, the purpose is to fractures can only be accomplished with real‐time three‐
explain briefly and concisely how these methods work, what dimensional (3D) mapping.
their applications are, how to understand the methods in use by As of this writing, passive seismic monitoring is the best
vendors, and how to interpret the results of passive seismic method for characterizing the size, shape, and location of
monitoring of hydraulic fracture treatments. This chapter also hydraulic fractures in oil and gas reservoirs and for under­
provides the most basic information on geomechanics, earth standing the interactions of hydraulic fractures with preex­
stress, and natural fractures required to understand passive isting natural fracture systems. Frac engineers, development
seismic methods and interpret the results. geologists, and reservoir engineers are the primary users of
The current boom in unconventional resource development passive products.
is almost entirely dependent on hydraulic fracture stimula­ Some basic definitions are required before proceeding
tion of tight petroleum and natural gas reservoirs. Successful further:
fracture treatments require sound designs based on knowledge
of the reservoir geomechanics and preferably with knowledge Active seismic methods—Seismic methods that record
of frac behavior in the field being treated. In some cases, reflected or transmitted seismic waves produced by
fracture treatments must be controlled in real time to ensure artificial explosions or vibrators on the earth’s surface
that the frac does not contact water‐bearing strata or other­ or in wells. The 2D and 3D reflection seismic surveys
wise propagate in undesirable ways. Well spacing in a field familiar to anyone in the upstream oil and gas industry
is a function of the horizontal distance from a well that is are examples of active seismic products.
effectively stimulated by a fracture treatment. This distance Passive seismic methods—Seismic methods that rely
cannot be determined using only pumping data (e.g., on energy emitted by rock movements in the subsur­
amounts of fluid and proppant). Halving or doubling well face. The ultimate source of the energy can be
spacing roughly doubles or halves (respectively) development entirely natural (e.g., tectonic movements or earth
costs of a field. The extent and manner of interaction of a tides), artificial (e.g., hydraulic fracture treatments),
fracture treatment with preexisting natural fractures provides or both.

Fundamentals of Gas Shale Reservoirs, First Edition. Edited by Reza Rezaee.
© 2015 John Wiley & Sons, Inc. Published 2015 by John Wiley & Sons, Inc.