The Independent Petroleum Association of America (IPAA) said Thursday production of natural gas plant liquids (NGPL) -- which includes ethane, propane, butane and lease condensate -- has increased substantially over the last three years.

According to IPAA calculations of data from the Energy Information Administration (EIA), domestic liquids production -- which couples NGPLs with Lower 48 crude oil -- totaled 654,000 b/d in 1Q2011, a 9.4% increase over 1Q2008. That means domestic liquids production was higher than what was imported from five of the top 10 sources for crude oil imports, namely Russia (556,000 b/d), Algeria (489,000 b/d), Iraq (375,000 b/d), Angola (320,000 b/d) and Colombia (318,000 b/d).

The figures reinforce the results of another IPAA study from July 6, which found that NGPL production had increased more than 12% from 2008 to 2010. In the July 6 report the IPAA said the increase in NGPLs "[was] coming in part from increased activity in the Bakken, Permian [and] Eagle Ford [shales]."

On Thursday the IPAA said NGPLs had achieved "a healthy rise" between 1Q2008 and 1Q2011, climbing 200,000 b/d to an all-time high of more than 2 million b/d, an increase of more than 11%.

"At that level, NGPLs are not easy to ignore since their output consistently exceeds that of total U.S. offshore crude oil production," the IPAA said, adding that the increase in NGPL production was the result of "strong growth in domestic natural gas production since 2005."

The IPAA said independent producers account for about 85% of marketed natural gas production in the United States, which is currently near a 40-year high at around 23 Tcf/year.

The liquids production study is available on IPAA's website,