Comprehensive Study on Microscopic Pore Structure and Displacement Mechanism of Tight Sandstone Reservoirs: A Case Study of the Chang 3 Member in the Weibei Oilfield, Ordos Basin, China

Abstract

With the continuous growth in global energy demand, research and development of unconventional oil and gas reservoirs have become crucial in the field of energy. This study focuses on the Chang 3 reservoir of the Yanchang Formation in the Ordos Basin, Weibei Oilfield, China. This reservoir is a typical tight sandstone reservoir, and its microscopic pore structure and displacement mechanism are essential for the efficient development of tight oil. However, the reservoir faces challenges such as complex microscopic pore structures and unclear displacement mechanisms, which hinder the efficient development of tight oil. In light of these challenges, through various studies including core observation, high-pressure mercury injection tests, water flooding experiments, oil-water two-phase relative permeability measurements, and stress sensitivity experiments, it was found that the Chang 3 reservoir exhibits strong microscopic heterogeneity. The pore-throat distribution characteristics mainly present two types: single peak and double peak, with the double peak type being predominant. The reservoir was classified and evaluated based on these characteristics. The improved injection ratio and properties enhance oil displacement efficiency, but an increase in irreducible water saturation has a negative impact on efficiency. The stress sensitivity of the reservoir fluctuates between weak and strong, with permeability being sensitive to net confining pressure. It is recommended to pay particular attention to the stress-sensitivity characteristics during reservoir development. The research results provide a scientific basis for the optimized development of tight oil reservoirs in this region, promote the sustainable development of unconventional oil and gas resources, and have significant theoretical and practical implications.

Comprehensive Numerical Evaluation of CO2 Huff-n-Puff in an Offshore Tight Oil Reservoir: A Case Study in Bohai Bay Area, China

“…In recent years, China’s onshore tight oil reservoirs characterized by ultralow porosity (<10%) and low permeability (<0.1mD) have been effectively developed . With this basis, for offshore unconventional reservoirs, the economic development has been received increasing attention. , …”

“…In recent years, China's onshore tight oil reservoirs characterized by ultralow porosity (<10%) and low permeability (<0.1mD) have been effectively developed. 1 With this basis, for offshore unconventional reservoirs, the economic development has been received increasing attention. 2,3 Since the oil recovery factor in tight oil reservoir is typically below 10% in the primary production, 4 CO 2 injection has been considered as an enhanced oil recovery method to improve the performance in tight oil reservoirs.…”