Changes

[[file:oilfield-water-analysis_fig2.png|thumb|{{figure number|2}}Stiff<ref name=pt05r149 /> diagrams used to show water compositions on maps.]]

[[file:oilfield-water-analysis_fig2.png|thumb|{{figure number|2}}Stiff<ref name=pt05r149 /> diagrams used to show water compositions on maps.]]

In the past, only the six principal elements were reported. Only five of these were determined by analysis: calcium, magnesium, chloride, alkalinity (usually reported as bicarbonate), and sulfate. Sodium was estimated by difference. Results were reported as parts per million (ppm), but because the methods are volumetric, it is more correct to report those results as milligrams per liter (mg/L). Recently, physical methods such as atomic absorption and spectrometry have made it possible to analyze for the less abundant elements<ref name=pt05r10>American Society for Testing Materials, 1990, Water and environmental technology: ASTM, v. 11., 01, 612 p., and v. 11., 02, 878 p.</ref>. Some elements, such as barium, are important because they precipitate and plug pores. Others such as iodine and bromine may be economically profitable to recover. (For more on properties of reservoir water, see the chapter on “[[Petroleum reservoir fluid properties]]” in Part 10.)

In the past, only the six principal elements were reported. Only five of these were determined by analysis: calcium, magnesium, chloride, alkalinity (usually reported as bicarbonate), and sulfate. Sodium was estimated by difference. Results were reported as parts per million (ppm), but because the methods are volumetric, it is more correct to report those results as milligrams per liter (mg/L). Recently, physical methods such as atomic absorption and spectrometry have made it possible to analyze for the less abundant elements.<ref name=pt05r10>American Society for Testing Materials, 1990, Water and environmental technology: ASTM, v. 11., 01, 612 p., and v. 11., 02, 878 p.</ref> Some elements, such as barium, are important because they precipitate and plug pores. Others such as iodine and bromine may be economically profitable to recover. (For more on properties of reservoir water, see [[Petroleum reservoir fluid properties]].)

==Interpretation==

==Interpretation==