The Study on Lower Limit of Porosity for Oil Accumulation in Chang-8 Member, Zhenjing Area, Ordos Basin
摘要
Lower cutoff values of the porosity and permeability of oil-bearing reservoir are as low as 4% and 0.03×10-3 μm2 within Chang-8 Member which is typically high-tight reservoir in Zhenjing area. The study of oil accumulation stages, diagenesis, burial history and simulation experiment reveals that the genesis of the high-tight oil reservoir is largely due to strata getting tighter after hydrocarbon accumulation. This paper presents a new approach to assess the lower limit value of porosity for oil accumulation, by taking porosity evolution of sandstone into consideration, and adding the loss of porosity after oil accumulation to current lower cutoff value of oil-bearing properties. The study shows that the lower limit value of porosity for oil accumulation in Chang-8 Member in Zhenjing area is 10.5%.