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TECHNICAL PAPERS

Surfactant-Enhanced Treatment of Oil-Based Drill Cuttings

[+] Author and Article Information
Jeffrey D. Childs

 School of Civil Engineering and Environmental Science, University of Oklahoma, Norman, Oklahoma 73019

Edgar Acosta

 School of Chemical Engineering and Materials Science, University of Oklahoma, Norman, Oklahoma 73019

John F. Scamehorn

 School of Chemical Engineering and Materials Science, The Institute of Applied Surfactant Research (IASR), University of Oklahoma, Norman, Oklahoma 73019

David A. Sabatini1

 School of Civil Engineering and Environmental Science, The Institute for Applied Surfactant Research (IASR), University of Oklahoma, Norman, Ok Iahoma 73019 Phone: (405) 329-1648, FAX: (405) 325-4217 sabatini@ou.edu

1

Corresponding author.

J. Energy Resour. Technol. 127(2), 153-162 (Jun 15, 2004) (10 pages) doi:10.1115/1.1879044 History: Received April 15, 2003; Revised June 15, 2004

Surfactant-enhanced washing of oil-based drill cuttings was evaluated as a technology of benefit to domestic oil producers. Laboratory studies showed the branched C14-C15 alcohol propoxylate sulfate to be a promising surfactant for liberating oils from these drill cuttings. Low concentrations (0.1% by weight) of this surfactant produced ultra-low oil-water interfacial tensions (IFTs), thereby allowing the rollup/snap-off mechanisms to liberate drilling oil (C16, C18 alpha olefins) from the cuttings. Surfactant-enhanced washing was compared between oil-based drill cuttings, Canadian River Alluvium (CRA), and silica, showing that the hydrophobic nature of the oil-based cuttings limited the amount of oil removed. The Ca++ content of the cuttings promoted surfactant abstraction by the cuttings, thereby increasing the hydrophobicity and oil retention by the cuttings. For this reason, three components were added to produce a robust system: (1) branched C14-C15 alcohol propoxylate sulfate, (2) octyl-sulfobetaine, and (3) builder (Na2SiO3). The Na2SiO3 builder was added to promote Ca++ sequestration, thereby decreasing the Ca++ available for precipitating the surfactant. The octyl-sulfobetaine helps mitigate high hardness and high hydrophobicity by acting as a lime soap dispersing agent (LSDA). Surfactant losses were minimized and oil removal was maximized by using all three components. When washing with this three-component formulation, oil removal was relatively independent of operating conditions such as bath-cuttings contact time and agitation energy; minimizing the contact time and agitation has the added benefit of reducing the fines production during washing operations. When washing with the three-component formulation, the oil was liberated from the cuttings as a free phase layer, sans surfactant and sans solids. The final (post washing) oil content of oil-based cuttings was in the range of 2% to 5%, which is below treatment standards for these cuttings. In addition, greater than 85% of the initial branched C14-C15 alcohol propoxylate sulfate remained in the bath after washing, which minimizes the need for make-up surfactant when the wash water is reused.

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Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 1

Illustration of rollup

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Figure 2

Illustration of snap-off of oil

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Figure 3

Schematic of surfactant-enhanced washing experiment

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Figure 4

Plot of oil-bath IFT as a function of surfactant concentration for surfactants evaluated in this work in the absence of added electrolyte

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Figure 5

Oil-bath IFT for a surfactant concentration of 0.025 wt % for the three surfactants with low IFT in Fig. 4

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Figure 6

Oil removed from recontaminated cuttings as a function of surfactant concentration, oil liberated as free phase upper layer (roll-up and snap-off mechanisms), total oil removed (solubilized and liberated free phase), and oil removed by solubilization in micelles

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Figure 7

Postwash oil content of the α-olefin recontaminated Marathon cuttings following centrifugation at 1790×g as a function of shaking time at a frequency of 400min−1 for the following formulations: (1) water-only wash, (2) surfactant, and (3) surfactant+builder. Initial oil content=20.0wt%.

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Figure 8

Postwash oil content of the SBF Baroid cuttings following centrifugation at 1790×g as a function of shaking time at frequencies of 75, 150, and 300min−1 for different combinations of components showing the best formulation as the one containing lime soap dispersing agent (LSDA, octylsulfobetaine), builder (Na2SiO3), and surfactant (propoxylated sulfate with branched C14-C15 alkyl tail). Initial oil=8.5%.

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Figure 9

Postwash oil content of the DBF Marathon cuttings following centrifugation at 1790×g as a function of shaking time at shaker frequency of 300min−1 for different formulations showing the best formulation as the one containing LSDA (octylsulfobetaine), builder (Na2SiO3), and surfactant. Initial oil content=9.1%.

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Figure 10

Postwash residual oil content for SBF and DBF cuttings, CRA, and silica and range of initial oil contents

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