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Shallow hazard detection in the near surface, a coherence cube processing application

Samedan Oil Corporation, Houston, Texas, U.S.

Evelyn Medvin

Core Laboratories, Houston, Texas, U.S.

Corresponding author: BRader@nobleenergyinc.com

Editor's note: Coherence Cube processing is protected under U.S. patents and is a mark of Core Laboratories.

The first 20% of the full text of this article appears below.

Interpreting the depositional style of deepwater sediments requires high-resolution seismic data. Enhancement of the seimic volume through specialized processing and interpretation methods can greatly improve the usability of exploration and production 3D volumes for shallow drilling hazard detection. Coherence cube processing provides a highly innovative and accurate method for clearly imaging subsurface faults and stratigraphy recorded in 3D surveys. The application of this technology to traditional 3D seismic surveys is key to detecting shallow hazards in deepwater areas where traditional methods are costly or inadequate.

Shallow drilling hazards exist as shallow gas pockets, gas chimney features, pockmarks on the seafloor caused by fluid withdrawal, near-surface faults, and shallow-water flow sands (SWF). SWF are the most difficult to detect and most dangerous in the deepwater environment. Studies have shown that nearly 80% of deepwater wells in the Gulf of Mexico have encountered SWF. Brian Barley of BP commented: "Our failure to predict shallow flowing sands reliably is an expensive gap in the tool kit" (TLE, 1999).

Drilling hazards also affect the positioning of platform anchors, field development, processing facilities and the placement of pipelines. Focused geohazard surveys required by the U.S. Minerals Management Service (MMS) may be inadequate for assessing hazards that can negatively affect a deepwater discovery. Kerry Campbell analyzed this problem in a 1999 TLE article and concluded, "Clearly, the most reliable technical approach to minimize geohazards risk would be to use 3D exploration seismic data for a preliminary geohazard assessment...."

Applying specialized processing techniques to enhance conventional 3D seismic data is a logical approach to minimizing geohazard risks. We have found that coherence cube processing applied to conventional seismic data is particularly useful in identifying near-surface depositional patterns that can impact well placement without requiring acquisition of additional data.

Coherence cube processing is the measurement of . . . [Full Text of this Article]