PHYSICAL SIMULATION EXPERIMENT ON ACCUMULATION OF TIGHT OIL AND GAS

With the development of engineering technology, especially the advancement in fracturing technology, unconventional oil and gas becomes a significant part of global oil and gas production. At present, profound understanding is scare in accumulation and controlling factors of tight oil and gas, which has been an obstacle to the prediction of tight oil and gas potential area and the elevation of exploration benefit. As big scientific issues in the field of tight oil and gas geology, researches need to be carried out in charging mechanism of tight reservoir, which aims to shine more light on the controlling factors of various saturations of oil and gas in tight reservoir and on the effective prediction method for the “sweet spot”.

A series of physical simulation experiment devices were developed to study the accumulation mechanism of tight oil and gas, with a focus on details of the experiment process and experiment procedure. And a series of physical simulation experiments were conducted on charging process of oil and gas in tight reservoir. Results turned out that there was a positive correlation between the saturation of oil and gas in tight reservoir and the injection pressure, and also the ratio of permeability and porosity.

Pore scale of tight reservoir was much smaller than that of conventional reservoir, and in the charging process oil and gas entered into smaller pores with increasing of the injection pressure to break the obstruction of capillary force, where oil and gas saturation elevated with the increase of injection pressure. With the same injected amount of oil and gas, lager porosity induces a lower oil and gas saturation, which can be manifested by positive correlation between oil and gas saturation and the ratio of permeability and porosity. A series of physical simulation experiments were conducted using gas as the fluid medium in tight reservoir from the Upper Triassic Xu Jiahe Formation in the Hechuan area of Sichuan Basin, and the gas saturation plates were established under the joint control of pressure difference and reservoir porosity/permeability parameters.