西南石油大学学报(自然科学版) ›› 2017, Vol. 39 ›› Issue (2): 35-42.DOI: 10.11885/j.issn.1674-5086.2015.10.22.02

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Pore Structure Characteristics of Taiyuan Formation(C3t) in Eastern Uplift of Liaohe Depression

ZHANG Qin1,2, PANG Zhenglian3, LIU Renhe1,2, MAO Junli4   

  1. 1. Langfang Branch, Research Institute of Petroleum Exploration & Development, PetroChina, Langfang, Hebei 065007, China;
    2. National Energy Shale Gas R & D(Experiment) Centre, Langfang, Hebei 065007, China;
    3. SINOPEC Petroleum Exploration and Production Research Insititute, Haidian, Beijing 100083, China;
    4. Exploration and Development Institute of Liaohe Oilfield, PetroChina, Panjin, Liaoning 124010, China
  • Received:2015-10-22 Online:2017-04-01 Published:2017-04-01
  • Contact: 张琴,E-mail:zhangqin2169@petrochina.com.cn

Abstract: This paper uses the Taiyuan Formation in the Eastern Uplift of the Liaohe Depression as an example to study transitional shale reservoir structures. Cores from well T2905 were observed and described, and samples systematically collected. XRD, high pressure mercury injection, nitrogen adsorption, and field emission scanning electronic microscope(FESEM) methods were adopted for analysis of pore characteristics including pore size, pore shape, and pore structure. Data from high pressure mercury injection showed a bimodal pore size distribution with a higher peak in the 10-100 nm range and a lower peak in the 10 000-100 000 nm range. Nitrogen adsorption can provide information on much smaller pores, so can help to precisely partition pores under 100 nm. Results from nitrogen adsorption indicated that mesopores(10-50 nm) provided the largest pore volume, accounting for 33.48%-43.96%. According to BET analysis, smaller pores provide less specific surface area. Extremely small pores(<2 nm) and micro-pores(2-10 nm) were the major contributors to specific surface area, accounting for 82.92%-91.58%, with an average 87.36%. The results from single factor analysis demonstrate that the specific surface area is not controlled by organic matter content but by clay mineral content, and the coefficient index is 0.901. The hysteresis loop from nitrogen adsorption and desorption can be used to determine pore shape; parallel-plated pores and slit-shaped pores were the main types identified. Such open nano-pores can improve shale gas desorbing efficiency and reservoir permeability, and enhance shale gas production.

Key words: Taiyuan Formation, high pressure mercury injection, low temperature nitrogen adsorption, pore structure

CLC Number: