The WTI for February delivery lost 29 cents Friday to settle at $45.59 a barrel. The benchmark peaked at $46.77 and bottomed out at $45.13. Compared to the Dec. 14 settlement, WTI is down 11 percent for the week.

Brent crude oil futures also ended the day lower. The February Brent contract price settled at $53.82 a barrel, reflecting a 53-cent day-on-day decline. Brent is down 10.7 percent for the week.

Factors that have contributed to the downturn in oil prices include concerns about a softening global economy, recent interest rates hikes by the U.S. Federal Reserve, ongoing political tensions in the United States and elsewhere and skepticism that plans by “OPEC+” countries to curb oil rig flanges gulf coast production will be adequate to stabilize the oil market. As Robert Rapier, chief energy analyst with Investing Daily, told Rigzone on Thursday, lead OPEC member Saudi Arabia has unveiled .

January reformulated gasoline (RBOB) also ended the pre-Christmas week on a negative note. RBOB futures edged downward by less than a penny to settle at $1.32 a gallon. Since last Friday, RBOB has lost 7 percent.

Bucking Friday’s downward trend was January Henry Hub natural gas, which rose by 23 cents to end the day at $3.82. Week-on-week, natural gas is down less than 1 percent.