Falling temperatures usually boost the spirits of oil producers. As energy users in the Northern Hemisphere stoke their furnaces and fill up their oil tanks, demand for fuel begins climbing toward its annual peak. For members of the Organization of Petroleum Exporting Countries, who supply 40% of the world's crude, the season should be one of relative harmony. But not this year. The group is in the throes of an oil-pumping free-for-all that has sent prices tumbling to levels not seen in more than two years.
In the past six weeks, three leading gulf producers -- Saudi Arabia, Kuwait and the...