The Subsurface Environment
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This document discusses different types of subsurface waters and their origins. It defines four main types: 1) Meteoric waters which occur near the surface and are involved in the hydrological cycle. 2) Formation waters (connate waters) which are trapped in sedimentary basins and have evolved over time through water-rock interactions. 3) Juvenile waters of igneous or metamorphic origin. 4) Mixed waters. It also discusses settings of earth's water, how water moves between settings like oceans, lakes, rivers, atmosphere, and groundwater, and reduction potential as a measure of water quality.
The Subsurface Environment
- 2. Revision: 1. Seal 2. Structural trap 3. Stratigraphic trap
- 3. Introduction We shall discuss about subsurface waters The effects of pressure and temperature on the condensation and evaporation of gas and oil. Fluid dynamics in sedimentary basins
- 5. Genetic Classification Normally, four types of subsurface water can be defined according to their genesis: 1. Meteoric waters: Occur near the earth surface. Involved in hydrogeological cycle. 2. Formation waters (connate waters): water trapped in the pore spaces or rocks in sedimentary basins, and have not recently been involved in the hydrogeological circle. These waters evolve with time as a result of water-rock interactions and gain high salinity. 3. Juvenile waters: These are igneous or metamorphic origin 4. Mixed water Meteoric Mixed Juvenile Connate
- 6. Settings of Earth’s Water Observe all the places where water is present Oceans: 96.5% of near-surface water Rivers Lakes: fresh or salty Swamps and wetlands Atmosphere Glaciers: 69% of freshwater Biological water Water in minerals: may be large amount Groundwater: 30% of freshwater 17.01.a1
- 7. How Does Water Move? Observe how water moves between settings Air currents Evaporation (oceans, lakes, rivers,…) Condensation Precipitation (rain, snow, hail) Runoff Infiltration: water seeps into ground Groundwater flows Groundwater flows onto surface Most precipitation into ocean; some evaporates on way down Transpiration from plants 17.01.b1
- 9. Reduction potential (also known as redox potential, oxidation / reduction potential, ORP, pE or Eh) is a measure of the tendency of a chemical species to acquire electrons and thereby be reduced. Reduction potential is measured in volts (V), or millivolts (mV). Each species has its own intrinsic reduction potential; the more positive the potential, the greater the species' affinity for electrons and tendency to be reduced. ORP is a common measurement for water quality
- 22. Note: Conductivity increases and gradient decreases with depth & declining porosity
- 25. Regional variations in heat flow affect petroleum generation. In areas of high heat flow & high geothermal gradient, the optimal tempt. Will be reached at shallower depth.
- 26. Questions?