Main Accumulation Controlling Factors and Forecast of Sand Lens Reservoir, Dongying Depression, China

Jiyang sub-basin is the most important area of subtle traps in China. Exploration in recent years has shown that the petroliferous property of the sand lens reservoir is quite different and the accumulation mechanism of lithologic reservoir is not clearly comprehended, restricting further exploration. A statistical analysis of the petroliferous properties of 145 lens reservoirs in Dongying depression was carried out, as well as the analysis of typical lenticular pools and NMR modeling experiments.Resultsshow that structural and sedimentary factors, and hydrocarbon generation and expulsion conditions of the surrounding source rock, as well as reservoir properties, are the main controlling factors for lens reservoir formation. Lens reservoir formation depends primarily upon the balance of accumulation power and resistance. When the hydrocarbon supply thresholds have been exceeded the accumulation power is bigger than the resistance at the sand and mud interface, so oil/gas would possibly accumulate to the lens. Accumulation power is made up of different capillary pressures between source and reserve, and hydrocarbon diffusion, as well as hydrocarbon volume expansion. Resistance is the osmotic resistance of flowing liquid. The better the three accumulation controlling factors are matched, the higher the petroliferous property. By applying the research results, the lens reservoir distribution of the third member of the Neogene Shahejie Formation in Dongying depression is forecast.