Oil & Gas Geology ›› 2005, Vol. 26 ›› Issue (2): 202-207.doi: 10.11743/ogg20050211

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Differences between formation conditions of Ordovician karstic reservoirs in Tazhong and Tahe areas

Yan Xiangbin1,2, Li Tiejun1, Zhang Tao1, Li Guorong3, Jin Xiaohui1, Ma Xiaojuan1,4   

  1. 1. Exploration & Production Research Institute, SINOPEC, Beijing;
    2. Northwest University, Xi'an, Shaanxi;
    3. Chengdu University of Technology, Chengdu, Sichuan;
    4. Central South University, Changsha, Hunan
  • Received:2004-12-08 Online:2005-04-25 Published:2012-01-16

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Abstract:

Comparative study shows that Ordovician karstic reservoirs in Tazhong and Tahe are quite different. In Tazhong, Ordovician dolomite reservoirs are characterized by small karst vugs, and limestone reservoirs are characterized by limited karst caves. While the karst cavernous reservoirs in Tahe are characterized by superimposition of multiple series of strata and continuous distribution in a large area. The main factors that have caused the differences of Ordovician karstic reservoirs in Tazhong and Tahe are tectonic evolution, lithofacies palaeogeography and dissoluble rock types. In Middle Caledonian, thrusting and folding were strong and well developed, dissoluble dolomites or limestones were dispersedly outcropped in narrow strips, and karst slopes were developed limitedly in Tazhong area; while tectonic movement in Tahe area was weak at that time. In Early Hercynian, Tahe area was wholly and largely uplifted, resulting in formations being strongly denuded and leveled, dissoluble limestone strata being flatly outcropped in large area, and karst slopes being well developed. Meteoric water flowed along the existing fracture systems and dissolved and reconstructed them in tubular flow, resulting in large cave systems. Several sets of cavernous reservoirs are distributed in large areas, due to multiple series of strata being superimposed and interconnected. However, tectonic movement in Tazhong was relatively moderate in Early Hercynian. Therefore, Tazhong area was dominated by Caledonian karst, while Tahe area was dominated by Hercynian karst.

Key words: Tarim Basin, Ordovician, karstification, karstic reservoir

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