Evaluating Geological Formations and Managing Ground-Water Resources: Can We Afford the Effort?

Evaluating Geological Formations and Managing Ground-Water Resources: Can We Afford the Effort? Stanley T. Paxton & Todd Halihan Oklahoma State University GSA Annual Meeting Salt Lake City, Utah 16-19 October, 2005

Acknowledgements US EPA, Ada, Oklahoma United States Geological Survey Oklahoma Water Resource Board ExxonMobil Corporation American Association of Petroleum Geologists Oklahoma State University

Ground Water - from Development to Management 2001 September 2002 Access to clean water is a continuing global challenge August 2002 February 2004 August 2002

Global Challenge Stress on world s major river basins, comparing the amount of water available to the amount of water humans use. Concerns about regional stability Source: World Commission on Water in the 21 st Century - MSNBC

What is Needed? Shift in economic thinking ground water vs surface water Consider ground water as a regional resource Teams of scientists and concerned citizens (geology, sociology, business, government) working water issues for the common good Water from Table Mountain Group, South Africa

Today s Main Points Given that access to clean water is a continuing global challenge. Assessing, predicting, and managing groundwater supply / quality on a regional basis is one way to address the issue Regional formation characterization studies necessary to the above can/should be conducted by our community (more frequently) > the technology is available > the cost is not prohibitive relative to a) surface storage and b) preservation of long-term public health

Why Few Studies? Insufficient need? > unnecessary? we just don t do things that way (old habits) Tools and techniques unavailable? Too expensive?

Key Lessons from Regional Studies: Properties vary with the geologic framework at all scales Factors that control properties can be mapped > stratigraphy, depositional setting > provenance > burial history (pressure, temperature) Development of predictive models / maps requires systematic integration of skills, tools/techniques, and quality-controlled data

Steps in Performing Regional Studies

Regional Studies and Keys to Success 1. Design study within context of regional geology 2. Emphasize rock-properties and water-quality data 3. Build an integrated database using standardized classification schemes 4. Devote time to data analysis 5. Develop and test predictive models 6. Recast predictive models as maps and tables to satisfy needs (governmental, business, technical) 7. Refine models as new wells drilled / update data base

Hierarchy of Factors Influencing Formation Properties Scale Dependency Design study within context of regional geology temperature Burial Factors pressure burial fluids depositional fluids provenance Inherited Factors stratigraphy facies

Depositional Environment Frequency 200 150 100 50 0 <2400m n=1461 1 DARCY 0.01 1 100 10000 An example of differences expected in aquifer properties should stratigraphic section be uplifted and eroded to nearsurface environs! North Sea Brent Group North Viking Graben Frequency 400 300 200 100 2400-2800m n=4072 1 DARCY 0 0.01 1 100 10000 up to 18% φ, three orders of magnitude difference in permeability across depositional settings Frequency 300 250 200 150 100 50 2800-3200m n=3423 Setting Offshore Marine Lower Shoreface Coastal Plain Upper Shoreface Active Channel 1 DARCY 0 0.01 1 100 10000 Permeability md

Temperature Frequency 300 n=3423 250 1 DARCY North Sea Brent Group North Viking Graben Facies Setting An example of differences expected in aquifer properties should stratigraphic section be uplifted and eroded to near surface environs! E D C B A Offshore Marine Lower Shoreface Coastal Plain Upper Shoreface Active Channel up to 18% φ, three orders of magnitude difference in permeability across temperature threshold 200 150 100 50 250 200 150 100 0 0.01 1 100 10000 50 n=3081 0 0.01 1 100 10000 Permeability md 800m

Locating Favorable Quality Temperature Pressure Fluids One approach to recognizing where the best formation quality will be located a Sweet Spot will correspond to the mapped coincidence of favorable conditions for each of the formation quality controls... Provenance Optimum Facies Maps Base Map Sweet Spot

Why Few Studies? Insufficient need? > unnecessary? we just don t do things that way (old habits) Tools and techniques unavailable? Too expensive?

What Price Water? Tucurui Hydropower Complex in Brazil (US $10 Billion) Positives > water storage, generation of electricity Negatives > malaria outbreaks, increase in mercury concentrations (World Commission on Dams) > evaporation > displacement of inhabitants

Cost of Surface vs Ground Water Surface Water Reservoirs* - $1 billion / km 3 - Typical project cost $10-100 million Ground Water Development - $20 K - $100 K / km 3 - Typical study cost of $100,000 - $1 million *Based on survey of dams used for water supply only and constructed in last 10 years.

Buckets Ground-water storage is 98% of the available freshwater storage (largest and cheapest container or bucket ) Halihan 2002 Box sizes proportional to the volume of fresh water

Why Few Studies? Insufficient need? Clear Need > unnecessary? But we do we just don t do things that way (old habits) Tools and techniques unavailable? Too expensive? Available Can we afford not to?