Phase equilibria of (methane-long chain ester cuts) systems in drilling conditions

Interactions Between Drilling Fluid and Reservoir Fluid

“…Effectively, we know that the higher the molar mass, the higher the critical point of a methane -hydrocarbons mixture [1]. This behaviour is also observed for the methane -methyl laurate, methane -methyl laurate -toluene (1) and the methane -methyl laurate -toluene (2) mixtures: the bubble curve of the methane -methyl laurate mixture is below the bubble curve of the methane -methyl laurate -toluene (1) which is below the bubble curve of the methane -methyl laurate -toluene (2). Again using the Peng-Robinson/Abdoul-Péneloux model, we compared the methane -ester -toluene mixtures and the methane -alkane -toluene mixtures behaviour (see figure 5) and the conclusions were similar.…”

“…The four different model systems investigated are the following: -Methane -methyl laurate -Methane -methyl stearate -Methane -methyl laurate -toluene (1) -Methane -methyl laurate -toluene (2) The methane -methyl laurate -toluene systems (1) and (2) are different by the relative quantities of methyl laurate and toluene in the liquid phase: the liquid phase of the methanemethyl laurate -toluene mixture (1) contains 17.1 mol % of toluene and the second one, 70.7 mol %.…”

“…• If the amount of gas incorporated in the mud is important, Berthezene et al [1] and Bureau et al [2] investigated the phase equilibria of different long chain natural esters with methane at two different temperatures (363.15 and 423.15K) and up to 100 MPa. Their conclusions indicated that no region of full miscibility is observed and that there is no critical point below 100 MPa at 363.15 K. Therefore, the mixture may still contain two phases and form gas bubbles within the mud column leading to the risk of explosion at the surface when mud circulation is stopped.…”

“…Their conclusions indicated that no region of full miscibility is observed and that there is no critical point below 100 MPa at 363.15 K. Therefore, the mixture may still contain two phases and form gas bubbles within the mud column leading to the risk of explosion at the surface when mud circulation is stopped. Bureau et al [2] attempted to model the phase behaviour using several equations of state and concluded that the ESD equation of state [3] provides a better fit of the bubble point curve.…”

“…In a second step, we use the model presented in Bureau et al [2] (ESD equation of state) to describe the phase behaviour and the volumetric properties of the mixtures investigated. In order to improve the gas -oil equilibrium prediction, we propose correlations for binary interaction coefficients between methane and ester, and between methane and aromatic molecules.…”