(613d) Changes in Bubble Point of Hydrocarbons in Shales: Effect of Confinement and Presence of Kerogen

The exploration and production from shale plays have revolutionized oil and gas production in US. The fluid properties in low permeability, low porosity shales are, however different from the conventional reservoirs. The kerogen is a organic matter found in shale rocks. It is considered as precursor to oil and gas found in shales and is a key component of the shale rock. The pore sizes in organic and inorganic matrix in shales are found to be in the range of nanometers. Thermodynamics of the oil and gas in intergranular porosity and in kerogen-related porosity are topics of significant research. The saturation pressures of hydrocarbons changes due to confinement and presence of kerogen in shales. Molecular Dynamics Simulations of kerogen-oil system and experiments related to swelling of kerogen with oils show the interaction of kerogen with oil.

In current work, kerogen is isolated from a shale sample by a series of acid treatments. The shale rock sample was collected from one of the prolific US shale play. The isolated kerogen was then swelled with octane-decane (60-40%) mixture. Swelling of kerogen is measured using Differential Scanning Calorimetry (DSC) and the results were compared with swelling ratios reported in published data. DSC is then used to measure the changes in bubble point of same octane-decane mixture in kerogen, at room as well as reservoir temperatures. The work, thus accounts for the effect of confinement of oil and kerogen-oil interactions on pressure-volume-temperature (PVT) properties of oil. The research shows that the bubble point pressures for oil at given temperatures are suppressed in the nano pores and in the vicinity of kerogen. The changes in saturation pressure of oils in shales effect properties like production gas-oil ratio and volumes and rates of recovery of petroleum reserves.