Oil & Gas Geology ›› 2004, Vol. 25 ›› Issue (3): 258-262.doi: 10.11743/ogg20040304

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Deposition and genetic analysis of Carboniferous Kalashayi Formation in Tahe oilfield

He Faqi1, Zhai Xiaoxian1, Yu Renlian1, Pu Renhai2   

  1. 1. Northwest Petroleum Bureau, SINOPEC, Urumqi, Xinjiang;
    2. Department of Geology, Northwest University, Xi'an, Shaanxi
  • Received:2004-01-15 Online:2004-06-25 Published:2012-01-16

Abstract:

Sedimentary characteristics and genesis of the Carboniferous Kalashayi Formation sand-shale sequence in Tahe oilfield are analyzed through integrating palaeontological,log,core,seismic and geochemical data.Overall,the sandstones in Kalashayi Formation are of progradational sedimentary sequence that get coarser and thicker upwards.The upper Ⅰ-Ⅲ oil reservoir groups are mainly of fluvial facies,while the lower Ⅳ-Ⅴ oil reservoir groups are of tide-effected fan delta front facies and plain facies.The evidences of tidal influences include:(1)rich in charophyta fossils with individual brackish Ostracoda and Acritarch microfossils;(2)local wavy,lenticular,bioturbate and scour-and-fill beddings;(3)a strontium/barium ratio ranging between 0.021 and 0.716,suggesting an environment from brackish to fresh water;(4)the Ⅳ-Ⅴ oil reservoir groups,as a whole,are the transition facies from tidal flat "double peak limestone" in the Bachu Formation to fluvial deposition of Ⅰ-Ⅲ reservoir groups.

Key words: Tahe oilfield, Kalashayi Formation, sedimentary characteristics, fluvial facies, tidal flat facies, eustatic sea-level change

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