Evangeline Section Meeting on Drilling and Production Practices on the Gulf Coast, 24 April, Lafayette, Louisiana
The deposition of scaling compounds from brines produced with oil has been a serious problem for many years. The use of inhibited muriatic acid to remove acid soluble scale has become commonplace, but the acid insoluble scales required mechanical removal.
Now calcium sulfate or "Gyp" scale, which is one of the most common of the acid insoluble scales, can be removed chemically.
The deposition of scales can be controlled over long periods of time by placement of complex dimetallic polyphosphates in the producing formation.
The deposition of scaling compounds from brines produced with oil has been a serious problem for many years. Compounds such as calcium carbonate, calciumsulfate, barium sulfate, and others have been found in many wells. The effect that these scales have on the production of a well will depend largely on the location of the scale in the system. Since the scaling or precipitation takes place when the equilibrium of the brine is changed by pressure drop, temperature change, or mixing with other brines, it could cause trouble at any point in the production system. Scale deposits have been found in the production string, down hole equipment perforations, and in the formation itself. The formation of scales is an economic problem that affects the producing operator. The scale can plug fractures or formation channels, stop upper forations, plug tubing and pumps and stick rods. All of these will have adverse effect, if not in production decline, at least in economical operations.
Scales found in wells have been roughly divided into two groups through field operations. Based on their reaction with hydrochloric acid, they are either [1] acid soluble or [2] acid insoluble. This, of course, is a simplified division as some of the scales found in the wells are mixtures of scaling compounds, but it is adequate for most field applications.
