The present invention relates to a process for the production of propylene polymers in the presence of a Ziegler-Natta catalyst comprising a titanium compound having at least one titanium-halogen bond, and a blend of a diether compound and a succinate compound as internal electron donor, all supported on a magnesium halide in active form, an organoaluminium compound and an optional external donor. To overcome variation that occurs with temperature which can result in signal degradation of the adjacent channel spectrum, a temperature compensated current is utilized to create an offset signal. The BOP stack has a throughbore and is installable on a well such that the throughbore is in fluid communication with the well bore.