Kasper Korsholm Ostergaard

Improving the Accuracy of Gas Hydrate Dissociation Point Measurements

Abstract: Following our previous communications on the impact of the amount of water phase on the time required at each temperature‐step 1 and the limitations of visual techniques in determining hydrate dissociation points, 2 a series of tests were conducted in this laboratory to investigate the impact of measuring techniques, mixing efficiency, heating method and heating rate on the accuracy of hydrate dissociation point measurements. The results showed that nonvisual techniques combined with stepwise heating and satisfactory mixing could save a significant amount of time while providing accurate hydrate dissociation data.

Equilibrium data and thermodynamic modelling of cyclopentane and neopentane hydrates

Abstract Cyclopentane and neopentane have only recently been recognised as a potential hydrate former, forming structure-II gas hydrates. However, no information on their hydrate phase boundary or modelling has yet been reported. In this paper, experimental hydrate dissociation data for cyclopentane and neopentane in their binaries and ternaries with methane or/and nitrogen (i.e., methane/cyclopentane, nitrogen/cyclopentane, methane/nitrogen/cyclopentane, methane/neopentane, nitrogen/neopentane, and methane/nitrogen/neopentane) over a wide range of temperature (282–301 K and 276–293 K, respectively) have been reported. The results of comparison with other newly discovered hydrate forming compounds showed that cyclopentane is the strongest hydrate promoter with neopentane in the second place. The predicted hydrate free zone is in good agreement with the experimental data, demonstrating the success of modelling.

Gas Hydrates and Offshore Drilling: Predicting the Hydrate Free Zone

Abstract: A well‐recognized hazard in offshore drilling is the formation of gas hydrates in the event of a hydrocarbon flow into the well bore from the reservoir (e.g., a kick). This could potentially block the BOP stack, kill lines and chokes, obstruct the movement of the drill string, and cause serious operational and safety concerns. Currently, salts are added to the drilling fluids to inhibit hydrate formation in offshore and arctic drilling. For deep water drilling, even saturated saline solutions may not provide the required protection, unless combined with chemical inhibitors. The reported experimental data on gas hydrate formation in drilling fluids are very limited and in some cases inconsistent. The available predictive methods are generally empirical correlations based on limited data and with limited application. In this presentation, a thermodynamic model capable of predicting the hydrate free zone in the presence of salts (NaCl, KCl, CaCl2, NaBr, Na‐formate, etc.) and chemical inhibitors (methanol, ethanol, ethylene glycol, glycerol, etc.) is presented. The model developed has been employed to predict the hydrate free zone in drilling fluids designed for offshore and deep water applications. The predictions are compared with experimental data and an empirical correlation, demonstrating the reliability of the thermodynamic model.

Equilibrium data and thermodynamic modelling of isopentane and 2,2-dimethylpentane hydrates

Experimental hydrate equilibrium data and thermodynamic modelling of isopentane and 2,2-dimethylpentane (2,2-DMP) are presented. Both compounds are reported to form structure-H gas hydrates in the presence of a help gas. Hydrate dissociation data for isopentane and 2,2-DMP in their binaries and ternaries with methane and/or nitrogen are measured and successfully modelled using an equation of state-based thermodynamic model. Indication of a change in the stable hydrate structure (structure-H to structure-I) for isopentane and 2,2-DMP in their binaries with methane at higher temperatures is also discussed.

A novel approach for oil and gas separation by using gas hydrate technology

Abstract: It is known that gas hydrates remove the light ends from reservoir fluids. Therefore, controlled hydrate formation in reservoir fluids could be an attractive option for separating oil and gas; that is, to replace conventional production facilities. In this communication we present the results of an integrated experimental and modelling study on the feasibility of the process, and the impact of the various parameters on the rate of hydrate formation. The study investigated the impact of parameters, such as mixing, water history, temperature, pressure, volume of reactor, heat removal requirements, and the quality of separated liquid. The work identified the major parameters and some of the technological requirements. Based on the experimental data, a simplified mass transfer model was constructed to simulate the kinetics of the separation process and to calculate the reactor volume and heat requirements at a specified degree of conversion. The results showed that it is possible to remove most of the lights from the liquid hydrocarbon phase by hydrate formation. The resulting liquid phase could be suitable for pipeline export or tanker loading after some treatment. Associated gas could be recovered locally from the hydrate phase. Alternatively, in cases where there is no infrastructure for transporting this gas, it might be exported as a hydrate slurry, as proposed by Gudmundsson and coworkers.

Gas hydrate equilibria of 2, 3-dimethylbutane and benzene with methane and nitrogen

Four phase (liquid water, liquid hydrocarbon, vapour, hydrate structure-H) equilibrium data are presented for 2,3-dimethylbutane in the presence of the help gases methane and/or nitrogen. Also, further to a previous communication, four phase (liquid water, liquid hydrocarbon, vapour, hydrate structure-II) equilibrium data are presented for benzene in the presence of nitrogen, and a mixture of methane and nitrogen. The hydrate equilibrium data are reported over the seabed temperature range (274–288K). Thermodynamic description and Kihara potential energy parameters for 2,3-dimethylbutane and benzene are reported for hydrate prediction purposes.