Scale Inhibitor Selection for Deepwater High Temperature Applications

Deepwater scale control in high temperature reservoirs has been a challenge since many scale inhibitors lose effectiveness at high temperatures due to molecular instability. It is well known that polymeric scale inhibitors have the highest thermal threshold up to 500 degree F among the three basic types of scale inhibitors. However, there were reports showing certain degradation of some polymeric scale inhibitors below 500 degree F. Therefore, a group of five polymeric scale inhibitors with various chemistries and molecular weights were selected for thermal stability investigation at 350 degree F. Evaluation of the scale inhibition performance was conducted for each chemical before and after thermal aging treatment using dynamic scale loop equipment so that the degree of degradation of each chemical could be determined. A reference scale inhibitor was used for comparison on the scale inhibition performance. Fourier Transform Infrared spectra were taken for scale inhibitors before and after aging to qualitatively characterize the influence of thermal aging. The calcium tolerance abilities were also studied for the five scale inhibitors. The work concludes by giving an in-depth evaluation of several novel polymeric scale inhibitors and determines their suitability for application in high temperature subsea environments.