About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

New Orleans Geological Society


New Discoveries Point to a Bright Future: South Louisiana Onshore Petroleum Exploration Symposium, May 22, 2003
Pages 14-16

3-D Seismic Data Acquisition in Southern Louisiana: Considerations for Technical and Commercial Success [Abstract]

Steve Knapp*, Kevin Callaghan, Randy Sides


Over the last two decades 3-D seismic data has changed the way exploration and production companies discover and exploit subsurface hydrocarbons. Technical and commercial drivers that have made this high-resolution image available to a wide audience have accelerated its impact. Several key technical milestones have aided the advancement of the technique over the course of time: portable recording systems which can withstand the elements; recording systems that can acquire a large number of channels; radio telemetry; GPS positioning; and processing capabilities (prestack migration, AVO). On the commercial side, non-exclusive surveys rather than proprietary ownership has allowed for many explorers to benefit from one dataset with shared cost and limited liability, thereby lowering the cost for accessing the seismic data. In the end it is the team effort combining the data owner, the acquisition company, and the oil company that results in success from both a technical and commercial viewpoint.

The planning and execution of current 3-D surveys bear little resemblance to their predecessors, especially when operations encroach upon urban areas. Project management has taken on added dimensions that require coordination of a multifaceted operation with stringent quality control procedures. Land work to secure permits, both surface and mineral, in the area of seismic operations is clearly one of the major logistical hurdles. In urban areas, nearly half of the project costs are allocated to permitting. shows a map-view display of a recent 3-D survey and is representative of the complex permitting areas, especially with small tracts, some having complicated title histories.

Survey grid of shots and receivers displays with a background of the permit issues that require resolution prior to acquiring beginning the seismic acquisition program. Typically on surveys such as this example in urban areas, the number of permits can exceed 300 per square mile.

* Speaker

End_Page 14-------------------------

In addition, the regulatory approval process involves interaction with many different municipal entities, ranging from local (town council), parish (Utilities Commission or Parish Police), state (Wildlife and Fisheries Commission), and federal (U.S. Army Corp of Engineers).

Project management also includes survey design, a cumbersome task in areas of restricted access due to environmental and cultural considerations or other factors that may restrict shot and/or receiver placement. Planning that considers these limitations facilitates efficient operations once the crew is actually in the field. In order to ensure optimal shot and receiver placement, aerial photographs or satellite images are typically used to determine exclusion zones and to assist in making adjustments in shot/receiver positioning and charge sizes for dynamite shots ().

A) Aerial photograph with shot and receiver grid overlay which assists in planning actual placement of equipment versus the pre-plot position. B) Exclusion zones indicated with circles of increasing radius representing acceptable increase in charge size. These radii are determined using particle motion studies coupled with industry standard guidelines.

The resultant shot and receiver distribution is monitored and modeled frequently to ensure the geophysical objectives are maintained. Further modifications allow for the utilization of different source and receiver types. Energy sources can be comprised of dynamite shots of variable charge size and hole depth, airgun shots when there are adequate navigable waterways, and Vibroseis in areas where explosive charges are impractical (). Force testing using three-component sensors is conducted in the planning phase to determine charge size limitations, and, in conjunction with the recording, to ensure particle motion does not deviate from generally accepted tolerances. The receiver spread typically contains eight lines of 168 channels for a total of 1344 detector locations. The receivers can be a combination of conventional geophones, either surface or buried, and buried hydrophones. The technique of utilizing marine detectors onshore requires filling the holes with water to ensure response from the hydrophones.

End_Page 15-------------------------

Various types of energy sources and detectors are utilized in modern seismic acquisition surveys to adapt to surface conditions. A) Dynamite shot hole drilled with a portable rig attached to an airboat.

B) Vibroseis operation in neighborhoods and other urban settings. C) Portable drilling rig for placement of hydrophone in water filled hole. D) Airgun barge operation in the Mississippi River.

Surveys of this type require extensive planning. This management, along with other Considerations, controls costs while maintaining data integrity. Typically data acquisition comprises half of the project cost, distributed as follows: surveying (10%), drilling (15%) and recording (25%). Permitting and other land work constitutes an additional 45%, with miscellaneous extras filling out the remaining 5%. These extras include quality control in the field, data processing, and other items such as maps, aerial or satellite imagery and deliverables. Non-exclusive surveys allow for these costs to be shared while at the same time limiting liability.

In summary, one finds that careful attention to the technical requirements for a given area, combined with close control of the decisions that affect cost, yield a 3-D seismic program which can be considered successful on both technical and commercial aspects. Cooperation and teamwork between the data owners, the acquisition contractors, and the oil companies ensures that the geophysical objectives are satisfied in a manner that benefits everyone. In the future this paints an exciting picture for seismic data acquisition in south Louisiana and in other challenging operational areas.

End_of_Record - Last_Page 16--------


Seitel Data, 10811 South Westview Circle Drive, Suite 100, Building C, Houston, TX 77043

Copyright © 2003 by NOGS (The New Orleans Geological Society)