Numerical Simulation Study on Hydrocarbon Migration of Paleo-reservoirs in Tazhong Oil Field, Tarim Basin, Northwestern China

Tazhong Oil Field located in the center of Tarim Basin is one of the greatest discoveries during the petroleum exploration in Tarim Basin. The course of many years for hydrocarbon exploration and development has proved that there existed a much larger ancient reservoir than present-day reservoir and residual oil section below present WOC is of obvious characteristics of water displacement. Study shows that after it early formed, the paleo-reservoirs had been reformed to a great extent by hydrodynamic pressure caused by compacted water flow, which had played a dominant role in the redistribution of oil and gas in the evolution process of paleo-reservoir to present one. The previous method to study secondary migration caused by hydrodynamic pressure is as follows: to draw oil and water potential energy diagrams by utilizing pressure data of exploratory wells; to judge hydrocarbon migration direction and possible accumulation position by combining them with geological conditions; thereafter, to forecast potential oil reservoirs from the macroscopic view. Application of reservoir numerical simulation technology to hydrocarbon migration by hydrodynamic pressure has its advantage whether in its mechanism or in the accurate description of oil and water distribution. This paper has first presented the existence of the paleo-reservoir, and then constructs its geological model on the basis of recognizing its configuration at different geological stages.