formation of gas or precipitate definition

For example, seawater is often injected into offshore reservoirs for pressure maintenance. īarite scales are generally the result of mixing incompatible waters. Halite self-scaling is found with both high-temperature and low-temperature wells. This increase in water vapor can leave behind insufficient liquid water to maintain halite solubility in the coproduced brine phase. (Falling pressure has a much smaller effect on decreasing halite solubility.) Evaporative loss of liquid water is generally the result of gas breakout from undersaturated condensate and oil wells, as well as the expansion of gas in gas wells. Halite solubility in water decreases with decreasing temperature, favoring halite dropout during the production of high total dissolved solids ( TDS) brines to the surface.

The drivers are falling temperature and evaporation. Halite scaling is also a self-scaling process. Calcite solubility also decreases with decreasing temperature (at constant CO 2 partial pressure). This removes carbonic acid from the water phase, which had kept the basic calcite dissolved. The main driver for its formation is the loss of CO 2 from the water to the hydrocarbon phase(s) as pressure falls. “Exotic” scales such as calcium fluorite, zinc sulfide, and lead sulfide are sometimes found with high temperature/high pressure (HT/HP) wells.Ĭalcite deposition is generally a self-scaling process. The chemical formulae and mineral names for most oilfield scales are shown in Table 1.

For example, strontium sulfate is frequently found precipitated together with barium sulfate. Many of these scaling processes can and do occur simultaneously. Additional salts may precipitate in the formation or in the wellbore (scale from “incompatible waters”). This is called “self-scaling.” If a brine is injected into the formation to maintain pressure and sweep the oil to the producing wells, there will eventually be a commingling with the formation water. 4.4.1 Cautions with inhibitor treatmentsĪs brine, oil, and/or gas proceed from the formation to the surface, pressure and temperature change and certain dissolved salts can precipitate.

Formation of gas or precipitate definition