Oil prices and production sharing and similar contract factors did not significantly impact this quarter's production volumes compared to the previous quarter or the second quarter of 2011. Our second quarter sales volumes were 759,000 barrels per day, slightly lower than our production volumes due to the timing of liftings in the Middle East/North Africa. Second quarter 2012 realized prices were lower for our products compared to the first quarter of the year. Our worldwide crude oil realized price was $99.34 per barrel, a decrease of about 8%. Worldwide NGLs were $42.06 per barrel, a decrease of about 20%. And domestic natural gas prices were $2.09 per MCF, a decline of 26%.
Second quarter 2012 realized prices were also lower than the second quarter 2011 prices for all our products. On a year-over-year basis, price decreases were 4% for the worldwide crude oil, 27% for worldwide NGLs and 51% for domestic natural gas. Realized oil prices for the quarter represented 106% of the average WTI and 91% of the average Brent price. Realized NGL prices were 45% of WTI, and realized domestic gas prices were 92% of the average NYMEX price.
Price changes at current global prices affect our quarterly earnings before income taxes by $38 million for $1 per barrel change in oil prices and $8 million for $1 per barrel change in NGL prices. A swing of $0.50 per million BTUs in domestic gas prices affects quarterly pretax earnings by about $35 million. These price change sensitivities include the impact of production sharing contract volume changes on income.