Advanced Technologies for Produced-Water Treatment and Reuse
Authors: Carpenter Chris 
Published: January 2015

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 17394, ’Advanced Technologies for Produced-Water Treatment and Reuse,’ by A. Hussain, J. Minier-Matar, A. Janson, S. Gharfeh, and S. Adham, ConocoPhillips, prepared for the 2014 International Petroleum Technology Conference, Doha, Qatar, 20-22 January. The paper has not been peer reviewed.

Historically, the treatment of produced water (PW) has been limited to free-oil and suspended-solids removal, using physical separation technologies and injection in disposal wells. However, because of new regulations, combined with geological restrictions and local water scarcity, the drive to have a greater fraction of the PW treated more extensively and ultimately to be reused is increasing. This paper presents the results of a laboratory investigation in which treatment processes were evaluated as treatment methods for PW from different oil and gas fields.

Introduction

A combination of factors is putting great pressure on operators to find new ways of treating and managing PW that promote water conservation and sustainability. However, treating PW to produce a good-quality effluent is a challenging task. PW characteristics can vary considerably. In order to treat PW to a water-quality standard that enables it to be reused, advanced water-treatment technologies (AWTTs) have to be applied, alone or in combination.

To investigate the suitability of several AWTTs to treat and reuse PW from Qatari gas fields, the authors, in conjunction with an operator’s research center, carried out a laboratory investigation in which various treatment processes were evaluated. Four treatment methods were selected to target main contaminants identified in PW from a Qatari gas field: Membrane processes were used to target field chemicals, membrane-distillation (MD) methods were used to target salinity, membrane-bioreactors (MBRs) were used to target organics, and ozonation was used to target field chemicals.

Overview of AWTTs

Membrane Processes. The potential for membrane processes to treat PW has been demonstrated successfully in various field studies; moreover, a number of upstream petroleum full-scale facilities have already installed membrane processes to treat and reuse PW. The treatment trains either are a combination of different membrane processes or involve other conventional water-treatment technologies such as media filtration or clarification. For two case studies involving the use of membrane processes, please see the complete paper.

Thermal Evaporators. These entered the PW-treatment market by finding niche opportunities. Moreover, because almost all waste streams are recycled back to the evaporator, the volumes of fresh water required for makeup are dramatically reduced.

With the proliferation of shale-gas wells in the past decade in the US, the demand for treating flowback water with total-dissolved-solids (TDS) concentrations greater than 100 000 mg/L has expanded the opportunities for thermal systems. Another niche market in which the application of evaporators has been very successful is the steam-assisted- gravity-drainage enhanced-recovery process.

MBRs. MBRs are now considered by the downstream petroleum industry as an excellent solution to treat various wastewater streams. Although MBRs have not yet been applied to treat PW at upstream oil and gas facilities, a number of bench-scale and pilot studies report that PW is biodegradable, achieving chemical-oxygen-demand (COD) and oil-and-grease (O&G) removals greater than 95%. Moreover, full-scale MBRs are also operating successfully in other industries, treating highly contaminated organic streams (COD greater than 15 000 mg/L) and achieving COD removals greater than 95%.