Ahmed Al-Futaisi

Three-Phase Hydraulic Conductances in Angular Capillaries

In this paper, we extend to three fluid phases a prior finite-element study of hydraulic conductance of two-phase creeping flow in angular capillaries. Previously, we obtained analytic expressions for the hydraulic conductance of water in corner filaments. Here we present the results of a large numerical study with a high-resolution finite element method that solves the three-phase creeping flow approximation of the Navier-Stokes equation. Using the projection-pursuit regression approach, we provide simple analytic expressions for the hydraulic conductance of an intermediate layer of oil sandwiched between water in the corners of the capillary and gas in the center. Our correlations are derived for the oil layers bounded by the concave or convex interfaces that are rigid or allow perfect slip. Therefore, our correlations are applicable to drainage, spontaneous imbibition, and forced imbibition with maximum feasible hysteresis of each contact angle, oil/water and gas/oil. These correlations should be useful in porenetwork calculations of three-phase relative permeabilities of spreading oils. Finally, we compare our results with the existing correlations by Zhou et al., and Hui & Blunt, who assumed thin-film flow with an effective film thickness proportional to the ratio of the flow area to the length of the no-flow boundary. On average, our correlations are twofour times closer to the numerical results than the corresponding correlations by Zhou et al. ,a nd Hui &B lunt.

Use of Tank Bottom Sludge to Construct and Upgrade Unpaved Roads

Tank bottoms are the liquids and residue, such as heavy hydrocarbons, solids, sands, and emulsions, that collect at the bottom of the treating vessel or that remain at the bottom of storage tanks after a period of service. Sludge composition is 50% to 65% crude oil, 20% to 35% water, and 5% to 20% solids. Disposal of tank sludge is a significant item of tank maintenance costs. Results are presented on the use of tank bottoms as a binder to construct and upgrade unpaved roads. Various sludge samples were initially characterized for chemical and physical composition, then three mixtures were prepared by using blends of aggregates and tank bottoms. No bitumen was used in the mixes. The mixtures include hot mix (aggregate and sludge were both heated), heated sludge and cold aggregate mix, and cold mix (no heat was applied). The Marshall mix design (ASTM D1559) was followed in the preparation and testing of the specimens. Results indicate that tank bottoms act as a binder to the aggregate and can provide significant strength. Heating both the sludge and the aggregate resulted in the highest stability value of 11.9 kN. An optimum sludge content of 6.5% by total weight of the mixture satisfied the requirements for low (3.3 kN) or medium (5.3 kN) trafficked surfaces or base layers according to Asphalt Institute specifications. Other mix properties, such as flow, air voids, voids in mineral aggregate, and voids filled with asphalt, were acceptable.

Impact of Microscopic NAPL-Water Interface Configurations on Subsequent Gas Injection into Water-Wet Permeable Rocks

Predictive field-scale models of the concurrent flow of three fluids require accurate predictions of five macroscopic flow descriptors: three relative permeabilities and two capillary-pressures as functions of the fluid saturations and saturation history. Since direct measurement of these descriptors is very difficult, and empirical correlations are often unreliable, the use of physically- based pore-scale models has become an appealing alternative. In this paper, we describe the features of our quasi-static pore network model for three immiscible fluids. The model integrates a realistic representation of pore connectivity and morphology reconstructed from 3D micro-focused X-ray CT images, a realistic description of fluid displacement mechanisms, and a sound representation of the wetting properties of the rock. All pore-level displacement mechanisms: piston- type, snap-off, cooperative pore-body filling, and double-displacements are considered with arbitrary contact angles and spreading coefficients. The proposed model is used to simulate gas injection into water-wet permeable rocks that initially contain water and NAPL after two-phase drainage followed by two-phase imbibition. The gas injection is performed using a cluster-based invasion percolation algorithm with trapping. The strong influence of the two-phase saturation history on the three-phase transport properties of a permeable rock is illustrated by performing a series of gas injections into Bentheimer and Berea sandstones with different initial NAPL and water saturations, and different microscopic fluid interface configurations.

Potential Use of Petroleum-Contaminated Soil in Hot Mix Asphalt Concrete

Petroleum-Contaminated Soil (PCS) results from leaking underground storage tanks, oil spills on clean soils, or soils surrounding petroleum refineries and crude oil wells. In Oman, Petroleum Development Oman (PDO) generates more than 50,000 tons/year of petroleum-contaminated soil (PCS) and faces a real challenge to safely dispose of these quantities. PDO is currently practicing the bioremediation process with high cost and limited results. This paper presents the results of using PCS as an fine aggregate substitute in Hot Mix Asphalt concrete (HMA) with percentages up to 40 percent by total aggregate weight. Environmental assessment was performed by analyzing the raw contaminated soil for heavy metals, and hydrocarbons. The Marshall mix design method was used to prepare and test the mixes. The results indicated a reduction in optimum asphalt content from 4.1 percent in the control mix to 3.5 percent in the PCS mixes. The increase in PCS content up to 40 percent resulted in a reduction in stability from 24.3 to 4.7 kN and increase in air voids from 3.5 to 9.4 percent. The flow was within the limits of specifications. Leaching of heavy metals using the Toxicity Characteristic Leaching Procedure (TCLP) was also performed on selected mixes. The results indicated concentrations well below the TCLP regulatory limits except for Zn for the 40 percent PCS mixes. The results indicated potential use of up to 15 percernt PCS in surface mixes, while higher percentages (up to 40 percent can however be used for medium or light traffic surface or base course layers.