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Petroleum Exploration Site Assessment | Strategic Carbon
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Leaders of Strategic Carbon, LLC are technical experts in interpretation of deep sediment petroleum deposits and environmental assessments through analysis of the geochemical, geophysical, and biological characteristics of shallow sediments. In shallow sediments above petroleum deposits, vertical fluid and gas diffusion and advection are important indicators of these reserve locations.  Basic biogeochemical parameters in shallow sediment profiles around drilling and exploration areas can also be used for a thorough ecosystem/environmental impact assessment. Through tactical partnerships with research organizations and other key providers, Strategic Carbon, LLC is uniquely positioned to provide services for all phases of exploration and recovery utilizing shallow sediment analysis for deep sediment petroleum assessment.

Typical initial test borehole drilling and well logging can cost in the range of $10-$20 million range for each drill site.  An expedition utilizing these shallow sediment analyses of geochemical, geological, and geophysical data to guide borehole site selection can cost as little as $1-$2 million, depending on the services provided. This certification represents a substantial cost savings to the client, and is an affordable investment to confirm which sites should be explored further.

Strategic Carbon, LLC will work with the client to first understand the project objectives and specific needs. Many different types of analyses are available from Strategic Carbon, LLC, with the final solution tailored specifically to the client’s needs and budget. A typical project may include some, or all, of the following, with a more detailed description below:

  • Site assessment with overflight surveys
  • Review of available data for site selection
  • Field work for sample collection
  • Gas profile and molecular speciation assessment
  • Stable carbon isotope analysis of gas source(s) and cycling
  • Heat flow probing to determine the vertical fluid and gas migration
  • Controlled source electromagnetic surveys for assessment of vertical gas migration and trapping

 

Oil

Overflight site assessment can be useful for the initial site determination (adjacent figure). Manned and autonomous aircraft monitoring for water column surface petroleum sheens can be coupled with knowledge of the physical characteristics of the water column to predict regions in the sediment where there is a vertical migration of petroleum from deep deposits. Surface oil sheen monitoring is achievable with a combination of sensors that includes microwave radiometers for assessment of oil thickness, ultraviolet and infrared sensors that distinguish between thin and thick oil layering, and laser fluorescence to evaluate the oil type. The employment of various types of radars has proven effective in detecting oil sheens. These radars include Synthetic Aperture Radar (SAR), Side Looking Airborne Radar (SLAR), and various types of maritime X-band radars. Currently, SAR is equipped on various autonomous aircraft operating within the United States and other countries. The Coherent Change Detection (CCD) application of the SAR can be used to determine a point of origin, direction of travel, speed of travel, and increases in oil sheening per site based on baseline data.

With an initial site survey complete, Strategic Carbon, LLC will begin the sample collection process, utilizing a state-of-the-art piston coring system for collection of seafloor shallow sediment samples. The piston coring system allows Strategic Carbon, LLC to collect up to a nine (9) meter core sample of the shallow sediment.

Assessment of active vertical gas and petroleum flux to the shallow sediment from deep reservoirs can be accomplished through geochemical analysis of piston core sediment and porewater samples.  Vertical profiles analyzed fluorometrically for petroleum seeps can show a concentration gradient that provides an estimate of deep deposit concentrations.  Further confirmation is achieved with assessment of the shallow sediment gas profiles and speciation.  The vertical flux rate of methane gas can be assessed with analysis of the depth of downward seawater sulfate diffusion into sediment that is controlled by upward vertical methane flux and the anaerobic oxidation of methane (AOM).  The depth of the sulfate-methane interface is dependent on the volume of methane, with a high vertical flux rate indicative of a shallow interface.  Confirmation this assessment addresses the petroleum reserves below and not shallow sediment methane is accomplished with an onboard analysis of the sediment gas composition, looking for higher molecular weight gases up to hexane that are associated with petroleum reserves. Stable carbon isotope analysis of methane and carbon dioxide provides further assessment of the gas source (microbial or petroleum sourced).

Where there is no petroleum in the shallow sediment there is still potential for significant reservoirs, which can be assessed with an analysis of petroleum sourced gases in the shallow sediment.  With the presence of deep sediment petroleum there will be vertical gas advection or diffusion with a distinct composition.  Stable carbon isotope analysis of gases is used to confirm the gas is not sourced from shallow sediment microbial cycles. This basic geochemical data can be coupled with further biogeochemical and microbial data to assess the environmental status of the ecosystem prior to and during field operations.

 

Petroleum-Exploration-ProtocolThe geologic, geochemical, and seismic data can also be coupled with heat flow assessment of vertical fluid migration and controlled source electromagnetic assessment of vertical gas hydrate deposits for a complete assessment of deep sediment petroleum deposits (adjacent figure).  Geological review of the coring sites provides an estimate of the system capacity to focus and force petroleum fluid fluxes. A high heat flow suggests rapid vertical fluid and gas fluxes, which is expected at locations where geochemical profiles show high petroleum seeps. Controlled source electromagnetic data is being developed for assessment of the vertical distribution of methane hydrate loadings that assist in interpretation of deep petroleum deposits.

Pertaining to methane hydrate exploration Strategic Carbon, LLC has demonstrated the benefits of a complete pre-drilling site survey during several expeditions over the last decade, the findings also pertain to petroleum exploration:

  • In expeditions off the mid-Chilean margin, geochemical data indicated low deposits of deep sediment methane while seismic (only) data indicated high methane hydrate deposits;
  • At Atwater Valley, on the Texas-Louisiana Shelf, a raised seismic bottom simulating reflection was correlated with porewater chloride anomalies and methane advection showing deep salt diapirs reduced the hydrate stability;
  • A recent survey of methane hydrate deposits on the Chatham Rise found no vertical methane fluxes in a large region where, conversely, seismic data had indicated high hydrate potential.

 

POINTS OF CONTACT

Richard Coffin, Ph.D., Founder, Strategic Carbon – rcoffin@strategic-carbon.com

Ingo Pecher, Ph.D., University of Auckland – i.pecher@auckland.ac.nz

Mathew Nelson, AAS Corporation – mnelson@aascorporation.com