Non-OPEC supplies have declined by around 1 million barrels per day, according to Sen, largely due to unplanned outages in Nigeria and Canada.
"I think the secular trend is higher," she told CNBC in London.
"The damage we are doing to the non-OPEC supplies is tremendous at this point in time … It is mainly because of all these unplanned outages — Nigeria, in particular, where we are losing nearly 700,000 barrels per day. But even if these unplanned outages do get resolved — unlikely at this stage — the underlying damage to the supply side is tremendous," Sen later added.
She said crude prices had recovered faster than forecast.
This month, Goldman Sachs said WTI spot prices would rise faster in the second-half of 2016 and 2017 than it had previously expected, but the recovery would be shallower.
It raised its 2016 average forecast for WTI prices to $44.60 per barrel, from the $38.40 predicted in March. However, the bank cut its forecast for 2017 to $52.50 a barrel from $57.50.