** Oil shares plunge on reports OPEC maintainsproduction at 30 mln/bpd
** Sector index off 2.8 pct, wiping out just half its gainfrom last month's 3-year low.
** All 20 of the worst performers on the STOXX 600 are oil & gas producers or services, led by Petroleum GeoServices & Seadrill. Chart: http://link.reuters.com/kyp53w
** Brent crude falls $3 to 4-yr low under $75/bl as Saudioil minister confirms OPEC will not cut
** Oil firms top 5 losers on the FTSE too withPetrofac leading losses. Royal Dutch Shell down2.6 pct. (RM: alasdair.pal.thomsonreuters.com@reuters.net)