Print this pageThe Use of DNA Analyses Moving into Petroleum Exploration
Scientists have known for decades that the majority of bacteria cannot be cultured. The phrase ”the great plate count anomaly” was coined to describe the disparity between the number of microbial cells that could be seen under a microscope and the number of cells that could actually be grown in laboratory.
The introduction of DNA-based detection methods has led to a revolution in the field of microbiology. The fundamental basis for applying this technology to oil and gas exploration is that most hydrocarbon-bearing structure leaks. This leakage usually includes the lower molecular weight components such as methane, ethane, propane and butane, and occasionally oil itself. The vertical migration of these hydrocarbons can be in form of macroseeps that follow faults or fractures, or microseeps that follow a buoyance-driven mechanism that results in a diffuse plume at the surface.
Potential benefits of DNA-based hydrocarbon seep detection and characterization include:
DNA based detection methods are potentially more sensitive than conventional analytical detection instruments;
It confers averaging function to offset variable rates of hydrocarbons seepage;
It detects specific bacteria that mediate hydrocarbon metabolism and remodeling.
To this technique, a large collection of molecular bioindicators for propane was identified. Propane was chosen as hydrocarbon target because it is generally considered a reliable indicator of thermogenic hydrocarbons. During the first phase of the project a large collection of molecular bioindicators for propane was identified, and for the second phase these probes were tested for their utility as a tool for mapping the location of propane plumes overlying potential hydrocarbons-bearing structures. The results presented elevated levels within the production limits of the fields.
Like any surface geochemical method, DNA-based molecular methods should be thought of as a complement to geophysics rather than as a replacement. There are a number of ways in which the technology could be incorporated at various stages in an exploration program. Prior to seismic acquisition, molecular surveys could be performed over a large area on a regional scale. Surface Molecular methods are less expensive than seismic, and this strategy would allow an operator to focus its geophysical budget on only over areas with the greater potential for hydrocarbons.
AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil