Structural exploration: location selection
| Exploring for Oil and Gas Traps | |
| |
| Series | Treatise in Petroleum Geology |
|---|---|
| Part | Predicting the occurrence of oil and gas traps |
| Chapter | Exploring for structural traps |
| Author | R.A. Nelson, T.L. Patton, S. Serra |
| Link | Web page |
| Store | AAPG Store |
Crestal locations
Because the most important goal of exploration is economic success, locations are often chosen to provide maximum information on the economic viability of the prospect. Therefore, locations that assess the structurally highest point (crest) at the primary reservoir appear, at first, to be most attractive. However, other criteria in structural plays need to be recognized when determining prospect-assessment locations. This approach becomes critical as the structural complexity increases or the structural play concept becomes more sophisticated.
Off-crestal locations
Circumstances may occur in which it is more appropriate to select a location based on technical needs or data quality rather than optimizing the economic success of the first well. Generally, these locations provide greater certainty in evaluating data (e.g., clearly defined seismic reflectors to help define a crestal position). Other structural play concepts may require off-crestal positions to be viable.
Examples of circumstances in which it is desirable to drill a location other than the crest include the following:
- Certain fracture plays in the Rocky Mountain thrust belts of the U.S. and Canada may be sensitive to forelimb or backlimb locations to provide the flow rates necessary to establish economic success.
- Tests in the offshore Netherlands have been drilled off crest and away from hinges to obtain an early assessment of matrix porosity in the reservoir.
- The position of the oil–water contact may be critical in defining the volume of hydrocarbons necessary for economic success.
- A nonoptimal acreage position may preclude access to the crestal location.
- Logistics problems (e.g., topography, environmental sensitivities) may preclude access to the crestal location.
Multiple-well locations
Well locations may be selected solely to provide information to support a second location. Such locations may be entirely off structure.
Well data programs and contingencies
There is often a tendency to plan well programs with economic success in mind. Unfortunately, an economic or technical failure is more likely, and we need to design data acquisition programs with options for that eventuality. In choosing a location and designing a well data program, we need to plan for possible failure by asking the following questions:
- Can this play be tested effectively with one well?
- What data do we need to establish a second location?
- What data do we need to determine whether to continue evaluating this play concept on this prospect?
See also
- Structural exploration workflow
- Tectonic setting
- Structural domains
- Structural fairway prospectivity
- Structural lead and prospect delineation
- Structural exploration: thrust belt example
External links
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