TITLE:
Research on Pore Structure and Fractal Characteristics of Tight Sandstone Reservoir Based on High-Pressure Mercury Injection Method
AUTHORS:
Zhengyin Li
KEYWORDS:
Tight Sand Reservoir, Reservoir Characteristics, Fractal Dimension
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.11 No.3,
March
23,
2023
ABSTRACT: Pore structure is the key element of tight sandstone reservoir, which
restricts the accumulation and flow of oil and gas in the reservoir. At
present, reservoir pore structure is the focus and difficulty of unconventional
oil and gas exploration and development research. The tight sandstone reservoir
in the Chang 4 + 5 member of the Upper Triassic Yanchang Formation is the main
reservoir for oil and gas exploration in G area. At present, there is little
research on its pore structure and fractal characteristics, which to some
extent affects the progress of exploration and development. This paper selects
the tight core samples of the Chang 4 + 5 member in the southern edge of the
Ordos Basin, and based on the high-pressure mercury intrusion experiment, uses
fractal theory to study the pore structure and fractal characteristics of the reservoir in the study area, thus providing
theoretical basis for the evaluation and exploration and development of the
Chang 4 + 5 tight reservoir in the G area. The research results show that the
lithology of the Chang 4 + 5 tight sandstone reservoir in the southern
edge of the Ordos Basin is mainly feldspathic sandstone, with the highest
feldspar content, followed by quartz, and the clay mineral is mainly chlorite.
The reservoir has poor physical properties and strong heterogeneity. There are
three main fractal characteristics in Chang 4 + 5 reservoir in G area: the
fractal curve of Type I reservoir sample is in two segments, the relatively
large pore has certain fractal characteristics, the pore structure is
relatively regular, and the heterogeneity is weak; Relatively small pores have
no fractal characteristics and pore structure is irregular. The fractal curve
of Type II reservoir samples shows a three-segment pattern, and each pore size
range has certain fractal characteristics, and it gradually gets better with
the increase of pore size. The fractal curve of Type III reservoir samples
presents a similar one-segment pattern, and the fractal dimension exceeds the
upper limit of 3. It is considered that the full pore size of this type of
reservoir does not have fractal characteristics, the pore throat is completely
irregular or the surface is rough, and the heterogeneity is very strong.