TABLE OF CONTENTS Produced water contains a number of substances, in addition to hydrocarbons, that affect the manner in which the water is handled. The composition and concentration of substances may vary between fields and even between different production zones within a single field. The terminology used for concentration is milligrams per liter (mg/l), which is mass per volume ratio and is approximately equal to parts per million (ppm). Some of the important produced water constituents are discussed in this section.
Produced waters contain dissoved solids, but the amount varies from less than 100 mg/l to over 300,000 mg/l, depending on the geographical location as well as the age and type of reservoir. In general, water produced with gas is condensed water vapor with few dissolved solids and will be fresh with a verl low salinity. Aquifer water produced with gas or oil will be much higher in dissolved solids. Produced water from hot reservoirs tends to have higher TDS concentrations while cooler reservoirs tend to have lower levels of TDS.
Dissolved solids are inorganic constituents that are predominantly sodium (Na +) cations and chloride (Cl -) anions. Other common cations are calcium (Ca 2+), magnesium (Mg 2+), and iron (Fe 2+), while barium (Ba 2+), potassium (K +), strontium (Sr +), aluminum (Al 3+), and lithium (Li +) are encountered less frequently. Other anions present are bicarbonate ( 
), carbonate ( 
), and sulfate ( 
).
