Thermal effects in a depleted gas field by cold CO2 injection in the presence of methane
Year: 2014
Type: conference-paper
Abstract: Depleted gas fields are seen as promising options for geological storage of CO 2 . The advantage of hydrocarbon fields are that the characteristics, such as the storage capacity and the proven sealing capacity are known. This means that only limited uncertainty remains after a technical feasibility study. One important issue with depleted gas reservoirs is the low pressure, at the onset of injection. This may lead to adiabatic cooling (Joule-Thomson cooling or JTC). The temperature reduction associated with this JTC can lead to hydrate formation and freezing of the residual pore water, especially the injected fluid also has a low temperature. In a related paper, we report on the development of a simulator, which is capable of predicting the fate of transport of a CO 2 in either the liquid gaseous and supercritical phase. The model only contains CO 2 besides the aqueous phase. One of the remaining challenges is to predict the impact of the methane, which is still present in a depleted gas reservoir, on the phase behavior of CO 2 and the thermal aspects. In this study simulations were performed on the P18-4 depleted gas field. The CO 2 was injected at a minimum temperature of 12 °C into the reservoir formation with a temperature of 120 °C. The average injection rate during the demonstration phase was modelled with 1.1 Mton/yr over a period of 5 year. The injection of cold CO 2 into P18-4 was modelled in TOUGH2 and a new module, which can handle not only the behaviour of CO 2 but also of CH4. The original ECO 2 M module was initially designed for CO 2 behaviour in gas reservoir and aquifers for brine-CO 2 mixtures, including all possible phase transitions, in the absence of any other gas. The new TOUGH2 module, which we gave the name ECO 2 MG module, was extended in such a way that compositional flow simulations of two different gases can be modelled, namely CO 2 and CH 4 . The ECOMG module can not only model the behaviour brine CO 2 mixtures but also the behaviour of brine-CO 2 -CH 4 mixtures including phase changes from gas to liquid and from super- and sub-critical conditions. Density, viscosity and enthalpy of the CO 2 -CH 4 mixture is based on NIST data. The new TOUGH2 module was used to model the thermal aspects of CO 2 injection including the presence of brine and CH4 initially in the reservoir. The reservoir model was initialized with a brine-methane mixture at 20 bar, which is the expected abandonment pressure of the reservoir. The prediction of thermal effects of this new tool were compared with those of the earlier version (CO 2 only) for several times during the projected 5 year injection period. The thermal effects investigated in this study were the JTC and also the effect of evaporation of the aqueous phase. The heat of evaporation of the brine is very significant and cools down the near well area significantly depending on the initial water saturation and the injection temperature of the CO 2 itself. In the new module we saw that after the CO 2 injection was started at first instance an uniform front of CO 2 /CH4 was formed. After a few years gravity underride of the still gaseous CO 2 becomes visible, which became stronger after the phase transition to liquid CO 2 . A free CH4 phase moved during the simulation in front of the CO 2 plume.
Source: Energy Procedia
Authors: D. Loeve, C. Hofstee, J.G. Maas
Language: English
Subfield: Environmental Engineering
Field: Environmental Science
Domain: Physical Sciences
Open Access status: diamond
OpenAlex ID: W2014939593