Scale control in ultra-deepwater under high temperature, high pressure and high total dissolved solids (TDS) is critical for efficient and safe oil and gas production. With the continued development of offshore production in ultra-deepwater, more and more wells are exposed to extremely high temperature (>150 °C) and pressure (>15,000 psig) under anoxic condition. However scale testing, prediction and control under these extreme conditions is often challenging due to the limitation of testing equipment to accurately simulate these environments.

The dynamic tube blocking test is a widely applied test approach for evaluating scale risk and scale inhibition efficiency in the laboratory. However, little information has been reported for studying control and inhibition of siderite (FeCO3), a major product from corrosion. Furthermore, very few studies assess the scaling risk of iron oxides under extremely high temperatures.

In this research, the kinetics of siderite nucleation and precipitation has been studied in the absence and presence of scale inhibitors including sulphonated polycarboxylic acid (SPCA), polyvinyl sulphonate (PVS), carboxymethyl inulin (CMI) and sodium citrate. Scale inhibitors have been evaluated at high temperature (up to 250 °C) to determine if they are applicable for siderite (or iron oxide) inhibition. Inhibition of iron oxide precipitation under 250 °C and 600 psig was observed.

All solutions used in this research are strictly anoxic with ≪ 1 parts per billion (ppb) of dissolved oxygen and in the absence of added reducing reagents, that might alter the reaction. This strictly anoxic condition is critical for evaluating inhibition efficiency and degradation of scale inhibitors due to the interferences and reactions between dissolved oxygen and scale inhibitors.

You can access this article if you purchase or spend a download.