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Decision Support System for Produced Water Management in the
Offshore Petroleum Industry
Niaz Mohammed, Tahir Husain, Neil Bose, Brian Veitch, and Kelly Hawboldt
ABSTRACT
DISSPROWM is an integrated modeling system for prediction of fate of produced
water pollutants in offshore environments, for determining the best treatment
technology and for assessment of risk and hazards to human and marine species
from non-carcinogenic and carcinogenic pollutants present in the produced water
including radionuclides. It consists of a Windows based Graphical User Interface
(GUI) developed with Microsoft Visual Basic that integrates a SQL Server database,
an initial dilution model, a dispersion model and risk assessment modules for human
beings and marine species. Mukhtasor’s model (Mukhtasor, 2001) is used as the
initial dilution model and is good of uniform flow only. USEPA Cormix has been used
for uniform as well as non-uniform or stratified flow. The database contains hundreds
of pollutants and their properties that are required in dispersion and risk assessment
modeling. The database also contains current produced water regulations and
information on some of the selected existing treatment technologies with typical cost
data required for decision-making purposes.
DISSPROWM database has been designed to include all important entities related to
produced water management. The database model is shown in Figure 2. The
database model has been normalized to third order form (3NF) to eliminate
redundancy and to improve data consistency and future enhancements. Apart from the
pollutants and pollutant properties, information on existing treatment technologies,
their applicability and cost in the offshore environment, information on the regulatory
requirements of produced water discharge, and monitoring requirements have also
been introduced.
The database has been implemented on a Microsoft SQL Server 2000 database
server.
DISSPROWM can assess carcinogenic and non-carcinogenic risk to human
health and marine species. It compues individual hazard quotient and the total fish
hazard. DISSPROWM can also assess human risk from contaminated fish
consumption as shown in the Figure 8. DISSPROWM can not compute hazard of
related to non-carcinogenic pollutant if the reference dose (RfD) is not available.
In case of carcinogenic risk, Slope Factor (SF) is needed. To determine the level
of risk NOEC and LC50 is needed. Therefore risk and hazard computation will be
incomplete if DISSPROWM does not have these pollutants stored in it’s database.
INTRODUCTION
Figure 4: Main Screen of DISSPROWM showing Pollutant Toxicology Data
According to the International Association of Oil and Gas Producers (OGP 2004) report,
about 17 million cubic meters of produced water is produced daily worldwide in
combined onshore and offshore operations. Management of this huge volume of
produced water in offshore developments in conjunction with the crude oil and natural
gas is a challenge for the industries. Common disposal options include produced water
treatment (PWT), reinjection (PWRI) and disposal (PWD). It is very difficult for the oil
and gas industries to make a decision about which disposal options to use because
this necessitates a detailed study of treatment methods, costing information and
regulatory requirements.
Decisions that industries need to make are:
 How clean should the produced water be before being discharged?
 Should the produced water be treated? If so what is the best available technology
(BAT) for treatment?
 What are the alternative treatment technologies considering cost and removal?
 Should produced water be re-injected into the wells?
 What is the risk involved to the marine organisms and humans if the produced water
is discharged into the ocean: in the short term; in the long term?
 What are the regulatory requirements before discharge and are they realistic and
sufficient?
DISSPROWM is developed with the objective to address issues that are critical for the
offshore petroleum industry and also to make the tool applicable to industry in their
decision-making to manage produced water in a cost effective and environmentally
safe manner. A schematic of DISSPROWM is shown in Figure 1. As shown in the
Figure, it contains a comprehensive database with information on chemical properties,
toxicity and technology, dilution models, as well as information on best available
treatment technology applicable to offshore platforms.
Figure 2: Database model of DISSPROWM
DESCRIPTION OF DISSPROWM
DISSPROWM has the following characteristics and functionalities:
• DISSPROWM is an integrated modeling system consisting of a SQL Server based
database, an initial dilution model, a dispersion model (Cormix) and some risk
assessment modules. The database contains produced water contaminants,
treatment technologies, case studies, costing, and regulatory guidelines
• The Graphical User Interface (GUI) of DISSPROWM is equipped with structured
menus and modern toolbar for frequently used functionalities and context sensitive
Help System.
• It has interactive data entry for produced water contaminants and dispersion model
parameters.
• It has a number of 2D and 3D graphical and tabular display options for displaying
prediction of fate and transport of pollutants
• It can assess risk and hazard for fish and other marine species as well as human
being from consumption of contaminated fish.
• From a known concentration of produced water contaminates the system can decide
the best available technology (BAT), and its approximate cost. Based on the extent
of treatment, it is possible to estimate risk to fish and marine species and human
beings and hence a tradeoff between cost and risk can be developed.
It takes series of user input in sequence and decides the best available technology
and risk to marine habitats and human health as shown in Figure 3.
Fate and Transport of Pollutants
Fate and effect of produced water depends on the fate of the individual components
and how their concentrations change with time. Dilution is mainly thought of as
occurring in two phases. There is the initial dilution or near-field phase which occurs in
the first few minutes, and the far dilution phase that happens several hours later.
Fate of pollutants in DISSPROWM is predicted by Mukhtasor’s initial dilution model
and Cormix. Mukhtasor’s initial dilution model is used to predict the concentration at
the end of the Control volume. The model is very simple and reportedly function with
reasonable accuracy for stable discharge from an open- ended outfall into unstratified
running water. Cormix is used for uniform and non-stratified flow and the concentration
of pollutants is predicted at both near fields and far-field.
Mukhtasor’s model is used to predict predicted environmental (PEC) concentration
and hence the exposure concentration. PEC is computed with the centerline dilution
model proposed by Mukhtasor (2001). Exposure concentration is computed using the
PEC, exposure probability and bioavailable fraction.
DISSPROWM has a number of tabular and graphical option for display of PEC
predicted by Mukhtasor’s model and Cormix in the near field and far field. A 2D plot for
near field concentration of one of the pollutants (Benzene) is shown in Figure 5.
Figure 8 Computation of human carcinogenic risk
Produced Water Treatment Technologies
Numerous studies have been done on treatment technologies, their applicability,
advantages, disadvantages, cost, commercial applications and other factors.
Information on produced water treatment technologies are scattered and is being
continuously compiled in the DISSPROWD database
Several other commercial treatment methods are available in the market. Most of these
treatment technologies are stored in the DISSPROWM database. A DISSPROWM
screen showing the best available technology and alternate technology is shown in
Figure 6.
Figure 8: Treatment Technology suggested by DISSPROWM
CONCLUSIONS AND RECOMMENDATIONS
DISSPROM can also plots contaminant plume and Contour plot of using Surfer for
Windows that must be installed in User’s PC. DISSPROM has a user interface for
various options of the contouring, such as selection of pollutant, setting a title for the
contour plot, smoothening of contour, shading of contour and using a boundary file
overlaid on the contour plot. A contour plot is shown in Figure 6.
Figure 3 The Schematic of DISSPROWM
Figure 1: Structure of DISSPROWM
DISSPROWM DATABASE
Numerous studies have been conducted in the past on produced water contaminants,
their fate and transport in the marine environment, risk induced to the ecology and
human beings. These studies has been compiled in many books and reports.
Chowdhury (2004) developed a Microsoft Access based database that contains
common produced water pollutants and their properties.
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DISSPROWM force users to enter different categories of input data in a sequential
manner. The Sequence data should be entered is shown on the Tabs below the toolbar.
After the project information is entered, other categories of data are entered or
computed in the following sequence: Pollutant name  Pollutant Concentration 
Flow and Ambient data  Control Volume Data  and Fish Data  risk computation
data. The structure of the system that showing pollutants toxicology data is shown in
Figure 4. This data is retrieved from database. Users are required to estimate and enter
the missing data so that Risk and hazard can be computed by DISSPROWM. Upon
completion of data entry, DISSPROWM allows user to save the data in a project file and
perform different task. Some of functionalities of DISSPROWM, such as querying
database entries and generating reports can be done any time without competing data
entry.
References
Chowdhury, S. H. (2004). Decision Support System for Produced Water Discharges in Offshore Operations, MS
Thesis, Faculty of Engineering and Applied Science, Memorial University of Newfoundland.
Mukhtasor (2001). Hydrodynamic modeling and Ecological Risk Based design of produced water discharge from
an offshore platform; A thesis for PhD at Memorial University of Newfoundland.
OGP, (2004). Fate and effects of naturally occurring substances in produced water on the marine environment a new review, Draft sent to OSPAR’s meeting of the offshore industry committee (15-19 March 2004, Agenda
item 3, OIC 04/3/Info.1-E) by The International Association of Oil and Gas Producers (OGP).