Print this pageEmerging Paleozoic Plays in North China's Onshore Basins
ALLEN, MARK B., STEPHEN J. VINCENT, GUO LI, CHRISTINE BROUET-MENZIES, DAVID I. M. MacDONALD, and ZHAO XUN
Many Chinese basins have Mesozoic-Cenozoic non-marine reservoirs that have poor production rates. Several Paleozoic plays potentially offer better production rates in the Tarim, Ordos and Bohai basins of north China. These basins have in common Precambrian basement, that once formed part of the Gondwanaland Supercontinent, and thick Lower Paleozoic carbonate successions. These, along wiith marine siliciclastic units, represent important reservoir units within these basins. Other north Chinese basins, such as Junggar, Turfan, Erlian and Songliao, have juvenile basement created during Late Paleozoic orogenies at Asia's margins. This group lacks good quality Paleozoic reservoirs.
Lower Paleozoic carbonates in the footwall blocks of early Tertiary half-grabens have been producing in the Bohai Basin for over 20 years, but their distribution is still poorly understood, and the prospects for this play are uncertain. Similar carbonates are preserved beneath the Mesozoic cover of the Ordos Basin. Strata at the top of the Middle Ordovician succession underwent major karst and breccia formation, prior to the deposition of mid Carboniferous clastics above a regional unconformity. Several recent major gas discoveries have been made in this karstic horizon and this is rapidly becoming the basin's principal pay zone. Several Paleozoic horizons in the central and northem Tarim Basin have produced oil and gas since 1984. These include Cambro-Ordovician carbonates which are similar to those of the Ordos and Bohai basins, except that production comes from compressional traps which developed during successive Late Paleozoic-Cenozoic orogenies in Central Asia. Lower Carboniferous marine sandstones of the Dongnetang Formation are also productive.