Page 208 - Geochemistry of Oil Field Waters

SEDIMENTARY ROCKS 195

TABLE 7.1
Average composition of sea water

Element Amount Element Amount Element Amount
(PPm) (PPm 1 (PPm)
Chlorine 18,980 Zinc 0.01 Tungsten 1 lo4
Sodium 10,560 Molybdenium 0.01 Germanium 1 lo4
Magnesium 1,270 Selenium 0.004 Xenon 1 lo4
Sulfur 880 Copper 0.003 Chromium 5 x 10-
Calcium 400 Arsenic 0.003 Beryllium 5 10-~
Potassium 380 Tin 0.003 Scandium 4 x
Bromine 65 Lead 0.003 Mercury 3 x 10-
Carbon 28 Uranium 0.003 Niobium 1
Oxygen 8 Vanadium 0.002 Thallium 1 10-~
Strontium 8 Manganese 0.002 Helium 5 x 10"
Titanium 0.001 Gold 4 x lod
Boron 4.8 Thorium 0.0007 Praseodymium 2x
Silicon 3.0 Cobalt 0.0005 Gadolinium 2
Fluorine 1.3 Nickel 0.0005 Dysprosium 2
Nitrogen 0.8 Gallium 0.0005 Erbium 2
Argon 0.6 Cesium 0.0005 Ytterbium 2
Lithium 0.2 Antimony 0.0005 Samarium 2
Cerium 0.0004 Holmium 8 x
Rubidium 0.12 Yttrium 0.0003 E uro pi um 4 x
Phosphorus 0.07 Neon 0.0003 Thulium 4 x
Iodine 0.05 Krypton 0.0003 Lutetium 4 x
Barium 0.03 Lanthanum 0.0003 Radium 3 x lo-"
Indium 0.02 Silver 0.0003 Protactinium 2 x lo-'*
Aluminum 0.01 Bismuth 0.0002 Radon 9
Iron 0.01 Cadmium 0.0001

tion. Some of the reactions that occur in or to diagenetic waters include
bacterial, ion exchange, replacement (dolomitization), infiltration by
permeation, and membrane filtration.

Formation water. Formation water as here defined is water that naturally
occurs in the rocks and is present in them immediately before drilling (Case,
1955).

Juvenile water. Water that is in primary magma or derived from primary
magma is juvenile water (White, 1957).

Sedimentary rocks

At least a portion of the water found in petroleum reservoirs consisting of
sedimentary rocks was deposited with the sediments before they were trans-
formed into rock. As the sediment compacted to form rock, the composition