New characterization on the petrophysical characteristics of tight sandstone reservoirs in Yanchang Formation Ordos Basin China

Abstract

New characterization on petrophysical characteristics of tight sandstone reservoirs is of an important value to exploration and exploitation of oil and gas. In this paper, low-field nuclear magnetic resonance, combined with casting thin sections, laser scanning confocal microscopy, scanning electron microscopy and pressure-controlled porosimetry were applied to investigate the pore structure characteristics of nine tight sandstone samples of Yanchang Formation in the Upper Triassic Ordos Basin China. And then, based on the nuclear magnetic resonance T 2 spectrum distribution and previous theoretical models, a new model is proposed to predict permeability of tight sandstone reservoirs. Petrophysical characteristics are qualitativelyquantificationally analyzed by a combination of various experiments, which is considered to be a new method that will be widely used in future research. Results indicate that nuclear magnetic resonance T 2 spectrum distribution has a close relationship with characteristics of pore types and pore radius distribution. Three T 2 spectrum peaks are identified by the relaxation time at 0.1-10 ms, 10-100 ms and >100 ms correspond to micropores (<0.2 mm), mesopores (0.2-4.9 mm) and macropores and fractures (>4.9 mm), respectively, which is well consistent with results from casting thin sections, laser scanning confocal microscopy, scanning electron microscopy and pressure-controlled porosimetry. Compared with the existing several classical models, the new permeability model can better estimate the permeability of tight sandstone samples. The new characterization method and new model can accurately evaluate petrophysical characteristics of typical tight sandstone samples, which have a great value for nuclear magnetic well logging in the exploration and exploitation of tight sandstone reservoirs in the Ordos basin.

Effects of organic matter and mineral compositions on pore structures of shales: A comparative study of lacustrine shale in Ordos Basin and Marine Shale in Sichuan Basin, China

“…Furthermore, only small quantity of dissolved pores develops in the Yanchang Formation lacustrine shale because the maturity of this shale is low. However, the tight sandstone of the Yanchang Formation has a large number of intragranular dissolution pores (Li et al., 2016).…”

Multifractal characteristics of shale and tight sandstone pore structures with nitrogen adsorption and nuclear magnetic resonance

“…As the one of the main tight oil/gas reservoirs in China, the pore structures of tight sandstones in the Ordos Basin have been widely reported (Du and Shi 2019;Li et al 2016;Wang et al 2020). The results show that the fractal dimension can effectively characterize the complexity of the pore structure, and the pore structure complexity and heterogeneity increase with the increase in fractal dimension (Wang et al 2018;Lyu et al 2017).…”

Special Issue: Advances of petroleum exploration and geology research in West China's petroliferous basins

“…Dolomite and tight gas sandstone reservoirs may be targeted during future gas exploration (Li et al, 2016), and therefore recent research has focused on such reservoirs.…”