Full Length Research Paper

Stabilization/solidification of synthetic Nigerian drill cuttings

S. E. Ogechi Opete¹, Ibifuro A. Mangibo² and Elijah T. Iyagba¹*

¹Department of Chemical Engineering, University of Port Harcourt, P. M. B. 5323, Port Harcourt, Rivers State, Nigeria.

²Department of Petroleum Engineering, University of Port Harcourt, P. M. B. 5323, Port Harcourt, Rivers State, Nigeria.

^*Corresponding author: E-mail: et.iyagba@uniport.edu.ng. Tel: +234 803 405 2225.

Accepted 20 January, 2010

Abstract

In the Nigerian oil and gas industry, large quantities of oily and synthetic drill cuttings are produced annually. These drill cuttings are heterogeneous wastes which comprises of hydrocarbons, heavy metals and chlorides. Currently, the treatment option for these drill cuttings is thermal treatment, which does not remove these toxic contaminants. In this study, the use of stabilization/solidification as a means of treating synthetic drill cuttings for potential reuse in construction products is investigated.  Portland cement was used as a binder. The ratio of water-to-dry binder was 0.4:1. Three different mix ratios of the drill cuttings and binder (2:1, 3:1, 4:1) were investigated. A set of physical tests (Unconfined compressive strength test and Durability test) as well as Toxicity Characteristic Leaching Procedure tests were conducted on the different mixes. For the drill cuttings, the moisture content, sodium adsorption ratio and exchangeable sodium percentage values of 4.04, 6.37 and 7.44% were below the DPR limits of 50, 12 and 15%, respectively. Heavy metals such as arsenic, mercury and silver were below 0.01, 0.001 and 0.001 mg/l compared to the DPR limits of 5, 12 and 5 mg/l, respectively. However, cadmium, chromium and zinc contents of 1.63, 54.80 and 121.17 mg/l were higher than the DPR limits. The unconfined compressive strength test results for the drill cuttings-binder ratios of 2:1, 3:1 and 4:1 were 1040, 606 and 490 psi, respectively much higher than the DPR limit of 20 psi. The Toxicity Characteristic Leaching tests and the Wet/Dry Durability tests produced satisfactory results as well. 

Key words: Drill cuttings, stabilization, solidification, portland cement.