Petroleum Reservoir Evaluation and Development ›› 2022, Vol. 12 ›› Issue (3): 468-476.doi: 10.13809/j.cnki.cn32-1825/te.2022.03.009

• Shale Gas Exploration • Previous Articles     Next Articles

Pore structure characterization of Shahezi Formation shale in Songliao Basin: Based on low-field nuclear magnetic resonance technology

LI Chuxiong1,2(),SHEN Baojian1,2,LU Longfei1,2,JIANG Qigui1,2,PAN Anyang1,2,TAO Jinyu1,2,DING Jianghui1,2   

  1. 1. Wuxi Research Institute of Petroleum Geology, Sinopec Exploration and Production Research Institute, Wuxi, Jiangsu 214126, China
    2. State Key Laboratory of Mechanism and Effective Development of Oil and Gas Enrichment in Shale, Wuxi, Jiangsu 214126, China
  • Received:2020-11-03 Online:2022-06-26 Published:2022-06-24

Abstract:

In order to characterize the micro pore structure of Shahezi Formation shale in Songliao Basin, nine shale samples from the lower part of the Shahezi Formation in the Songliao Basin were selected to carry out NMR T2 tests in saturated and dry conditions, and simultaneous petrophysical testing with field emission scanning electron microscope observation. The T2 relaxation characteristics, pore types and distribution characteristics were systematically analyzed. And the difference of porosity measured by the NMR method and the gas method was compared. The results show that the NMR T2 spectrum of the shale samples from the Shahezi Formation is dominated by a single peak type with shorter relaxation time, and the pore diameter is mainly distributed in the range of 10~1 000 nm. The pore types are mainly nano-scale inorganic pores, and the organic pores and microfracture generally underdeveloped. The NMR porosity calculated after deducting the base signal is 0.68 %~3.66 %, which has a good matching relationship with Helium porosity. The samples with smaller porosity are more likely to be affected by the background signal of rock matrix, resulting in the relative error of test results. In generally, the nuclear magnetic resonance technology can accurately analyze the porosity and pore size distribution of low porosity and low permeability shale samples, but attention should be paid to the NMR signal interference caused by organic matter and clay mineral bound water.

Key words: shale, nuclear magnetic resonance, porosity, pore size distribution, pore type

CLC Number: 

  • TE121