Maintaining an alkaline pH is of crucial importance for all well construction fluids in order to avoid corrosion problems. The only way of avoiding a significant drop in pH when these fluids are exposed to acidic gases is to add a pH buffer. Formate brines are the only high-density oilfield brines compatible with alkaline pH buffers. Consequently, carbonate / bicarbonate pH buffers are routinely added to formate field brines. This section of the manual describes the natural pH buffering capabilities of formate brines themselves and the effect of an acid gas influx (carbon dioxide (CO₂) and hydrogen sulphide (H₂S)) on the brine pH. The benefits of the carbonate / bicarbonate buffer addition are demonstrated by showing the pH response of such buffered formate brines to an acid gas influx. Guidelines are given for how to measure pH in formate brines and how to measure buffer concentration and buffer capacity.

 

To be advised of updates to this chapter please mail us.