What are the chances of surviving septicemia in the intensive care unit?

Good. The overall adult survival is around 70%. Young adults do better than elderly. Keys to improving the odds include early recognition that you are "septic", early broad spectrum antibiotics based on the presumed source ( lung, soft tissue, blood vessel catheter, abdomen ), early drainage of any pus, aggressive support of the lungs, kidneys, heart to maintain good perfusion to all these.
Very good. Most medical centers have protocols for dealing with sepsis that have a high degree of success. What is important is whether shock occurs or not and other underlying illnesses. In the past mortality for septic shock was 35-40%, but now it can be as low as 8-10% in the best icu's.
Depends. The specifics vary based on source of sepsis and to what extent there are underlying medical problems that predisposed to sepsis. ( for example a 90 year old man with chronic kidney failure and lung cancer septic from a perforated bowel will probably do worse than a 30 year old man septic from pneumonia. That said the overall mortality rate from sepsis is in the 25% range, meaning 3/4 will survive.