Swelling/extraction tests are single-contact phase-behavior experiments to measure the solubility of CO 2 dissolved in crude oil and the amount of hydrocarbon that CO 2 can extract or vaporize from crude oil. The tests are commonly conducted in a visual PVT cell with a large sample size (40-100cc). In this paper, an easy operated apparatus capable of determining phase behavior with a significantly smaller sample size (3 to 14 cc) is described. The apparatus consists of a high-pressure view cell, high-pressure and precision syringe pump filled with CO 2 , a water bath, and accessories to measure the temperature and pressure. The device is capable of determining vapor-liquid, liquid-liquid and vapor-liquid-liquid equilibrium commonly observed in a high pressure CO 2 enhanced oil recovery process. The solubility of CO 2 in oil, the expansion volume of oil due to the dissolution of CO 2 as well as the phase transition during the test were quantified with excellent reproducibility. The molar volume of oil saturated with CO 2 correlated linearly with the mole fraction of dissolved CO 2 suggesting ideal mixing in the liquid phase. The phase behavior between CO 2 and crude oil samples with different composition, temperature and pressure is discussed.

Carbon dioxide (CO 2 ) is a proven enhanced oil recovery technology. However, many reservoirs are located at shallow depths or geologic conditions such that CO 2 can not be injected at pressures above the MMP. CO 2 injection is usually not considered as an enhanced oil recovery process in these reservoirs. When CO 2 is injected below the MMP, displacement efficiency decreases as a result of the loss of miscibility. Near miscible displacement has sometimes been referred to as the process occurring between immiscible and miscible pressures, but has never been clearly defined. This paper describes laboratory study of CO 2 near miscible displacement in an Arbuckle reservoir in Kansas.Phase behavior studies between CO 2 and Arbuckle crude oil were carried out to define near miscible conditions at reservoir conditions. Swelling/extraction tests combined with slim-tube experiments were interpreted to identify the mass transfer mechanisms at near miscible condition. A phase behavior model was developed to match PVT data and MMP in the slim-tube experiment. Good agreement was obtained between simulated and observed data from slim-tube experiments. Core flooding tests were conducted to evaluate oil recovery at near miscible condition at which pressure varies from 1350 psi (MMP) to 1150 psi. Recovery of over 50% of the waterflood residual oil saturation was observed when CO 2 was used to displace Arbuckle oil from Berea, Baker dolomite and Arbuckle dolomite cores.At near miscible conditions, extraction appears to be the primary mechanism for mass transfer between hydrocarbon components and CO 2 . However, the reduction of oil viscosity by a factor of five occurred when CO 2 dissolved in the oil. This suggests that some of the additional oil recovery may be attributed to reduction of the mobility ratio between CO 2 and resident oil.

The thermal behavior of potassium C1–C12 n-alkanoates (K-carboxylates) were studied over the temperature range T/K = (243 to 873). A number of problems in industrial Fischer–Tropsch facilities were attributed to these compounds, but this study also revealed some beneficial effect that may directly be related to the thermal behavior of potassium methanoate. The unusually low melting point of potassium methanoate, T/K = (442.2 ± 0.3), combined with its thermal stability to T/K ≈ (693), may explain the ease of distribution of the potassium promoter of iron-based Fischer–Tropsch catalysts during synthesis even when potassium promoter is added separately. The C2–C12 K-carboxylates were all thermally stable at temperatures T/K ≤ (713), and significant mass loss was not observed at T/K ≤ (748). The thermal stability and high melting point of potassium propanoate, T/K = (636.9 ± 0.3) and potassium butanoate, T/K = (623.1 ± 0.3), in particular caused these compounds to be prone to cause pressure drop problems in refining units. The C4–C12 K-carboxylates melted to a liquid crystal phase first, before clearing at higher temperature. One or more solid–solid transitions were observed in all of the K-carboxylates, with the exception of potassium hexanoate.