Simultaneous Evaluation of Time-Dependent Phase and Wetting Properties of Hydrocarbon Liquids for CO₂-Enhanced Recovery of Oil and Gas from Tight Reservoirs

Abstract

A new method is presented for simultaneous observation of time-dependent interfacial and wetting behavior for a system of hydrocarbon liquids, water, rock sample, and CO2. Application of this method for assessment of using CO2 to enhance oil and gas recovery from water-rich tight reservoirs is discussed with exemplary results. The discussion includes predicting time evolution of capillary pressure in tight rocks and swelling of liquid hydrocarbons trapped by water, and estimating the composition of the liquid phase composed by the trapped hydrocarbons and CO2 transferred through the water barrier.

Driving Mechanisms in CO2-Assisted Oil Recovery from Organic-Rich Shales

“…A thorough investigation on oil extraction from Sultani shale using scCO 2 is available in the literature along with other studies that have proved scCO 2 to be an attractive solvent for hydrocarbons in shales. − Although scCO 2 is not in direct contact with the shale surface in a free form in our experiments, it is however able to diffuse through the aqueous phase until it reaches the shale surface and enters its pores. Part of the CO 2 dissociates in the aqueous phase forming carbonate (CO 3 2– ) and bicarbonate (HCO 3 – ) ions which impedes their migration into the pores of the shale . In any case, molecular CO 2 obviously does enter the pores.…”

“…The volumetric swelling model proposed by Wang et al . is used to calculate the solubility of CO 2 in the oil.…”

“…Part of the CO 2 dissociates in the aqueous phase forming carbonate (CO 3 2− ) and bicarbonate (HCO 3 − ) ions which impedes their migration into the pores of the shale. 52 In any case, molecular CO 2 obviously does enter the pores. This is confirmed through a recurrent experimental observation after the measurements are completed.…”

“…This is possibly due to the complicated partitioning of CO 2 within this complex four-phase system composed of an aqueous phase where carbonic acid is dissociated and molecular CO 2 is solubilized, an oleic phase where molecular CO 2 is also solubilized, and an organic pore system into which CO 2 is dissolved and strongly adsorbed. 29 The volumetric swelling model proposed by Wang et al 52 is used to calculate the solubility of CO 2 in the oil. The model is fitted to our experimental data, and the kinetics are exemplarily presented in Figure 11 for the CaCl 2 brine.…”

Investigation for CO2 Adsorption and Wettability of Reservoir Rocks

“…The value of the contact angles was determined from water sessile drop images taken by the camera, with a drop shape analysis program provided by Krüss, Germany. The program employs the axisymmetric drop shape analysis (ADSA) technique described elsewhere to measure the contact angle on the surface of rocks. ,, …”