Hedge funds and other large investors reduced their net long positions on the New York Mercantile Exchange by more than 8,500 contracts to end Tuesday at 146,304.
Speculators on the ICE Exchange's look-a-like US contract increased their net long positions, however, by 3,453 contracts to 19,807 that week.
US crude oil futures dropped from $84.45 a barrel on Sept. 27 to $75.67 a barrel on Oct. 4.
The largest part of the fall in net longs on NYMEX came from speculators opening new short positions to bet on further price falls. Short positions rose by 6,329 over the period to 68,747, versus a reduction in longs of 2,220 to 215,051.
Some of those will have been caught out by the bounce in prices since they bottomed on Tuesday, rallying by over $7 to close at $82.98 a barrel on Friday — a gain of almost 10
percent in just three sessions.
Speculators' views were mixed on oil products last week, increasing net longs in RBOB gasoline but cutting them for heating oil.
RBOB net longs were up by 2,615 to 36,505 in the week to Oct. 4 as prices rose fell from $2.6955 a gallon to $2.4884 a gallon.
The rise in net longs in RBOB largely came from traders closing short positions, which were down by 2,228 to 13,533.
Heating oil net longs were cut by 3,990 to 9,584 as prices fell from $2.8766 a gallon to $2.7234 a gallon. Long positions were cut by 3,286 while shorts were raised by 704 futures and options contracts.
Meanwhile, J.P. Morgan said on Friday it sees upside price risks conducive to oil prices moving to $130 per barrel for 2013 from ongoing geopolitical issues, low spare capacity, the potential for stock building, and currency-related issues.
The bank sees Brent prices for 2013 average at $121.25 per barrel and forecasts 2013 average WTI price
at $114.25 per barrel.
"Our analysis suggests that supply constraints will again be reached by the end of 2013, driving a quarterly rise in our ICE Brent price forecast to $130/bbl," it said.
J.P. Morgan maintained its price projection of $115 a barrel for Brent crude oil, and $97.50 a barrel for WTI through 2012.
