Characteristics of the tight sand reservoirs in the delta front in the Xu-2 Member of the Upper Triassic Xujiahe Formation (Hechuan area of the central Sichuan Basin, SW China)

  • Xiong Ding
  • Bingwen Wang
  • Jingshan Chen
  • Qingsong Tang
  • Han Wu
Original Paper


The Xu-2 Member of the Upper Triassic Xujiahe Formation (Hechuan area, southwestern China) is an important potential sedimentary sequence for gas exploration in the central Sichuan Basin. Thus, we performed a comprehensive study of drilling parameters, sedimentary cores, well logging, and core test data and combined our results with previous research and the geological background of the basin. We found that the Hechuan area was a delta front that included underwater distributary channels, interchannels, and mouth and distal bars during deposition of the Xu-2 Member. The sand body genetic types were divided into three categories based on where they developed: an underwater distributary channel, a mouth bar, or a distal bar. The lithology of the Xu-2 reservoirs is mainly feldspathic litharenite, lithic arkose, subarkose, litharenite, and sublitharenite. Residual intergranular pores and intergranular dissolution pores are the major pore types in the reservoirs. Reservoirs with porosities of 0.18–15.84% and permeabilities of 0.001–8.72 × 10−3 μm2 showed a correlation coefficient of 0.7592. The reservoir throats are mainly tubular and constricted. Overall, the sedimentary environment and diagenesis are the major controlling factors for reservoir formation in the study area. The reservoir zones with relatively high porosity and permeability mainly developed in a delta front with underwater distributary channels and mouth bars. Chlorite growth preserved the primary pores during early diagenesis stage B, and intergranular dissolution pores resulted from contact with organic acids derived from source rocks during middle diagenesis stage A1. Compaction and cementation significantly decreased porosity during middle diagenesis stage A2. These important factors influenced reservoir quality.


Reservoir characteristics Controlling factor Tight sand Xujiahe Formation Central Sichuan Basin 



We thank Kara Bogus, PhD, from Liwen Bianji, Edanz Editing China (, for editing the English text of a draft of this manuscript.

Funding information

This work was initially carried out with the support by the China Scholarship Council Foundation (201708515155), Open Fund (PLN201613) of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Southwest Petroleum University), and PetroChina Innovation Foundation (2015D-5006-0107).


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Copyright information

© Saudi Society for Geosciences 2018

Authors and Affiliations

  • Xiong Ding
    • 1
  • Bingwen Wang
    • 1
  • Jingshan Chen
    • 1
  • Qingsong Tang
    • 2
  • Han Wu
    • 1
  1. 1.School of Geosciences and TechnologySouthwest Petroleum UniversityChengduChina
  2. 2.Chuanzhong Oil and Gas Field of PetroChina Southwest Petroleum CompanySuiningChina

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