Solvent Injection Strategy for Low-Temperature Production from Fractured Viscous Oil Reservoirs

Abstract

Viscous oil resources have great potential to help meet the future demand for petroleum products as conventional resources are depleted. Currently high temperature steam injection is the recovery process of choice, with high energy intensity and associated greenhouse gas emissions. The work presented here explores a low-temperature solvent-only injection strategy targeting fractured systems. The warm solvent is in the vapor phase when injected into the reservoir but will condense when it contacts the cold oil and reservoir rock (liquid extraction). After the system has reached the target operating temperature, the injected solvent remains in the vapor phase when it contacts the oil (solvent-enhanced gravity drainage). The experiments discussed in this work explore the key parameters (permeability, temperature/pressure, in situ injection rate, and solvent type) that influence each production mechanism. The primary impact of decreasing permeability is a proportional decrease in film gravity drainage rate. A decrease in temperature slows the mass transfer during the liquid extraction phase and decreases the drainage rate during the film gravity drainage phase. Increasing the in situ injection rate leads to improved liquid extraction because of higher concentration gradient in the solvent-rich liquid phase at the oil/solvent interface. Solvent type affects both mechanisms and changes the nature and amount of asphaltene precipitation. Pentane yields relatively less asphaltene precipitate than butane (18 wt % vs 11 wt % asphaltene content in residual oil). Residual oil saturation was observed to increase as permeability and/or temperature were decreased.

Viscous Oil Recovery and In Situ Deasphalting in Fractured Reservoirs: Part 1. The Effect of Solvent Injection Rate

“…Rankin et al 20 conducted preliminary proof-of-concept experiments on viscous oil recovery in a sand pack simulating a single-fracture matrix system. The novel warm solvent injection strategy that combines two mechanisms, liquid extraction and vapor solvent-oil gravity drainage, showed high oil production rate and low residual oil saturation.…”

“…In this work, we seek to extend the study from Rankin et al 20 through investigating the effect of solvent rate on the mechanism of liquid solvent extraction and the dynamics of deasphalting in a single fracture-matrix system. Instead of sand packs, 20 cores drilled from a well consolidated sandstone outcrop are used for a more realistic matrix permeability and pore network morphology. The core flood experiments are conducted at a constant temperature and production pressure such that the injected solvent (n-butane) remains in liquid phase.…”

Modeling solvent enhanced gravity drainage from a single matrix block in fractured oil reservoirs

“…Oil recovery with solvent injection mainly depends on the diffusion of solvent and its mixing due to natural convention in the matrix blocks (Kahrobaei et al 2012). Diffusion of solvent is a very slow process and is not practical as an enhanced oil recovery method, however, gravity driven convection with counter-current flow is a promising solution for many fractured reservoirs from heavy to light oils (Darvish et al 2006;Hatiboglu and Babadagli 2008;Rankin et al 2014; Leyva-Gomez and Babadagli 2016).…”

Estimation of Low-Temperature Mass-Transfer Properties of Methane and Carbon Dioxide in n-Decane, Hexadecane, and Bitumen Using the Pressure-Decay Technique

“…For instance, these hydrocarbon resources can be found in reservoirs at temperatures ranging from 10 to 20 °C and pressures of 0.5 to 4 MPa. 2 Therefore, understanding the behavior of the reservoirs' fluids at these conditions is essential for the implementation of any recovery technique. Certainly, heavy oil recovery processes require the estimation of properties inherent to its operating mechanism.…”