Simultaneous oil recovery and residual gas storage: A pore-level analysis using in situ X-ray micro-tomography

Abstract

We imaged sandstone cores at residual gas saturation (S gr) with synchrotron radiation at a nominal resolution of (9 µm) 3. We studied two three-phase flooding sequences: 1. gas injection into a core containing oil and initial water followed by a waterflood (gw process); 2. gas injection into a waterflooded core followed by another waterflood (wgw process). In the gw flood we measured a significantly higher S gr (= 20.6%; S gr in the wgw flood was 5.3%) and a significantly lower residual oil saturation (S or ; S or in the gw flood was 21.6% and S or in the wgw flood was 29.3%). We also studied the size distribution of individual trapped clusters in the pore space. We found an approximately power-law distribution ∝ with an exponent τ 2.02-2.03 for the residual oil clusters and τ = 2.04 for the gas clusters in the gw flood. τ (= 2.32) estimated for the gas clusters in the wgw process was significantly different. Furthermore, we calculated the surface area A-volume V relationships for the clusters. Again an approximate power-law relationship was observed, ∝ with p  0.75. Moreover, in the gw flood sequence we identified oil layers sandwiched between the gas and water phases; we did not identify such oil layers in the wgw flood. These results have several important implications for oil recovery, carbon geo-sequestration and contaminant transport: a) significantly more oil can be produced and much more gas can be stored using a gw flood; b) cluster size distributions for residual oil or gas clusters in three-phase flow are similar to those observed in analogue two-phase flow; c) there is a large cluster surface area available for dissolution of the residual phase into an aqueous phase; however, this surface area is significantly smaller than predicted by percolation theory (p  1), which implies that CO 2 dissolution trapping and contamination of aquifers by hazardous organic solvents is slower than expected because of reduced interfacial contact areas.

Pore Scale Observations of Trapped CO2 in Mixed-Wet Carbonate Rock: Applications to Storage in Oil Fields

“…In a in the safety and permanence of the storage and contributes the majority of estimated storage 46 capacity in regional assessments [6][7][8][9] . A large body of recent work has reported observations of 47 trapping in the laboratory [10][11][12] and modeling to analyze the implications for CO 2 migration 13 …”

Multi-Objective Optimization of Microemulsion Flooding for Chemical Enhanced Oil Recovery

“…This considerable potential is of great interest for Enhanced Oil Recovery (EOR) methods which fall into three main categories: thermal, gas and chemical methods. Generally, they involve the injection of fluids into the reservoir to generate favorable fluid properties or interfacial conditions, overcoming forces trapping the oil and boosting oil production substantially [3][4][5].…”

Pore-scale remaining oil distribution under different pore volume water injection based on CT technology

“…In the earliest studies, clusters of all size were observed, with approximately power-law distributions (Iglauer et al, 2012). It had been found that cluster size can range from a single pore to multiple-pore configurations (Karpyn et al, 2010;Kumar et al, 2010;Iglauer et al, 2013). The blob size was directly related to the viscous force, and the blob surface area and volume had an impact on the mass transfer characteristics of the system (Al-Raoush and Willson, 2005).…”