Hadi Nasrabadi

Confinement Effects on Phase Behavior of Hydrocarbon in Nanochannels

Several researchers have recently studied the phase behavior of petroleum fluids in shale systems. There is a general agreement that the confined PVT properties in shale are substantially different from the corresponding bulk properties. These differences have significant impact on the prediction of well performance and ultimate recovery in shale reservoirs. Experimental measurements of fluid properties in shale rocks are currently not available. This has led to significant amount of uncertainty in phase behavior calculations for shale reservoirs.In this study, experimental validation of numerical predictions for phase behavior of various hydrocarbons confined in nanochannels was performed using a nanofluidics platform. The nanofluidics platform was designed, fabricated and tested at different temperatures. Design of the nanochannel is described in this paper.In this study, a nanochannel device (similar to Duan and Majumdar 2010) was designed, fabricated, packaged and tested. The reservoirs in the nanofluidic chip were filled with various hydrocarbon liquids (e.g. n-decane). The temperature was varied at a constant pressure, during which epifluorescence imaging was performed to measure the bubble nucleation temperature, i.e., the temperature corresponding to the formation of the first bubble of gas (i.e., to determine bubble-point pressure and temperature relationship).Copyright

Mesoscopic Simulation of Slip Motion for Gas Flow in Nanochannels

In this paper the Lattice Boltzmann method (LBM) was used to investigate gas flow in nano-channels, the critical region beyond which indefinite slip motion occurs in this channel and its effect on the deduced permeability. We defined a parallel-bounded planar two-dimensional domain for our simulation and calculated the system velocity profile.Numerical conformity was achieved when compared with the Hagen-Poiseuille’s equation. Good agreement was also established between the simulation and existing models reported in literature. A closer look at the region of full slip motion was also done and we observed that above a critical slip coefficient, a sudden significant increase in slip motion sets-in indefinitely with respect to the system time scale.The results indicate that when the LBM is used in gas flow simulation in nano-channels, if the slip effect is increased there is an effective increase in the fluid velocity and this affects the deduced permeability.Copyright

A Novel Model for Fracture Acidizing with Important Thermal Effects

Fracture acidizing is a well stimulation technique used to improve the productivity of low-permeability reservoirs, and to bypass deep formation damage. The reaction of injected acid with the rock matrix forms etched channels (that depend on injection rate, mass transport properties, formation mineralogy, reaction chemistry of the acid, and temperature) through which oil and gas can then flow upon production. The use of a model that can effectively describe fracture acidizing is an essential step in designing an efficient and economical treatment. Several studies have been conducted on modeling fracture acidizing, however, most of these studies have not accounted for the effect of variation in acid temperature (by heat exchange with the formation and the heat generated by acid reaction with the rock) on reaction rate and mass transfer of acid inside the fracture. In this study, a new fracture acidizing model is presented that uses the lattice Boltzmann method for fluid transport and takes into account these temperature effects. The lattice Boltzmann method incorporates both accurate hydrodynamics and reaction kinetics at the solid-liquid interface. This method is also well known for its capability to handle reactive transport in complex geometries. This enables the method to model realistic fracture shapes, on a pore-scale level, and predict the shape of the fracture after acidizing. Results of carbonate fracture dissolution with and without the thermal effects are presented. It is found that including thermal effects alters the predicted shape of the fracture after acidizing.