Photo: Christian Ove Carlsson

CERE seminar by Yiqun Liu

"PVT Study of Gas-Stock Tank Oil System at HPHT Conditions"



Global oil consumption will soon reach 100 million barrels per day and is going to increase in the foreeable future. To meet the high global oil demand, the industry has to develop unconventional petroleum reservoirs or reservoirs at harsh conditions, the latter being quite often HPHT (high pressure-high temperature).

Accurate description of the reservoir fluid phase behavior is crucial to development of a petroleum reservoir, and essential to the risk reduction for HPHT ones. However, there is a general lack of accurate thermophysical data in the literature at HPHT conditions despite their importance for reservoir simulation and production forecast.

For example, density, viscosity, and phase equilibirum data of a resercoir fluid are difficult to obtain over a wide temperature and pressure range, and the asymmetric nature of reservoir fluid systems usually poses many challenges for precise modeling of these properties.

In this study, we intend to prepare fluid mixtures with different gas-oil ratios to mimick different reservoir fluid compositions. The asymmetric mixtures are prepared by recombining stock tank oils with gases of known composition. In the beginning stage, we focus on the phase equilibrium study of pure gas (C1, N2, CO2) and stock tank oil systems.

The saturation pressure is measured in a PVT 240/1500 variable volume cell with full visibility screen manufactured by Sanchez Technology. It can operate in the pressures up to 1500 bar and temperatures up to 200 . The saturation pressures are measured through swelling tests which was to define the maximum allowable gas (C1, N2, CO2) concentration for a given pressure.

Once the saturation pressure of the system is determined, density and excess volume of methane + STO and nitrogen + STO were measured under the single-phase region. The measurement provides valuable data for evaluation and development of relevant models such as classical cubic EoS’s (SRK and PR) and an advanced non-cubic EoS (PC-SAFT).


Thu 21 Feb 19
9:00 - 10:00