Optimal Reuse of Flowback Wastewater in Shale Gas Fracking Operations Considering Economic and Safety Aspects

Abstract

This work presents a mathematical programing formulation for the optimal management of flowback water in shale gas wells considering economic and safety aspects. The proposed formulation accounts for the time-based generation of the flowback water, as well as the options for treatment, storage, reuse, and disposal. The economic objective function is aimed at determining the minimum cost for the fresh water, treatment, storage, disposals and transportation. The safety objective accounts for the risk associated to a failure in the treatment units and its consequence in human deaths. In this regard, the proposed method is able to consider different treatment units with different operating efficiency factors, costs and risks. To carry out the water integration, a recycle and reuse network is proposed. A given scheduling for the completion phases of the wells is required to implement the proposed method. Finally, an example problem is presented to show the applicability of the proposed method.

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PART A
EUROPEAN SYMPOSIUM ON
COMPUTER AIDED PROCESS
ENGINEERING
2TH
6
Zdravko Kravanja and Miloš Bogataj
Faculty of Chemistry and Chemical Engineering
University of Maribor
Maribor, Slovenia

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xx Contents
Economic Evaluation of Hybrid FO-crystallization-RO Desalination
Process
Kiho Park, Do Yeon Kim and Dae Ryook Yang 919
Modelling and Analysis of a Soybean Biorefinery for the Production
of Refined Oil, Biodiesel and Different Types of Flours
Cristine De Pretto, Paulo Waldir Tardioli, Caliane Bastos Borba Costa 925
Disjunctive Models for Strategic Midstream Delivery Agreements
in Shale Gas Development
Markus G. Drouven and Ignacio E. Grossmann 931
Multiparametric Metamodels for Model Predictive Control of Chemical
Processes
Ahmed Shokry, Canan Dombayci, Antonio Espuña 937
Optimal Reuse of Flowback Wastewater in Shale Gas Fracking
Operations Considering Economic and Safety Aspects
L.F. Lira-Barragán, J. Martinez-Gomez, J.M. Ponce-Ortega,
M. Serna-González, M.M. El-Halwagi 943
Control relevant modelling for haemodialysis
Thomas Eck and Vivek Dua 949
Dynamic Multi-Scenario Approach to Robust and Profitable
Online Optimization & Optimal Control of Batch Processes
Francesco Rossi, Gintaras Reklaitis, Guido Buzzi-Ferraris,
Flavio Manenti 955
Merging information from batch and continuous flow experiments
for the identification of kinetic models of benzyl alcohol oxidation
over Au-Pd catalyst
Federico Galvanin, Noor Al-Rifai, Enhong Cao,
Meenakshisundaram Sankar, Graham Hutchings, Asterios Gavriilidis,
Vivek Dua 961
Multi-period Sequential Synthesis of Heat Exchanger Networks
and Utility Systems including storages
Alberto Mian, Emanuele Martelli and Francois Maréchal 967
Simplification of Equation-Oriented Models through the Digraph Method
Fei Zhao, Xi Chen, Lingyu Zhu 973

Zdravko Kravanja, Milo Bogataj (Editors), Proceedings of the 26th European Symposium on
Computer Aided Process Engineering  ESCAPE 26
June 12th -15th, 2016, Portoro, Slovenia © 2016 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/B978-0-444-63428-3.50162-4
Optimal Reuse of Flowback Wastewater in Shale
Gas Fracking Operations Considering Economic
and Safety Aspects
L.F. Lira-Barragán,a J. Martinez-Gomez,a J.M. Ponce-Ortega,a* M. Serna-
González,a M.M. El-Halwagib,c
aChemical Engineering Department, Universidad Michoacana de San Nicolás de
Hidalgo, Morelia, Michoacán, 58060, México
bChemical Engineering Department, Texas A&M University, College Station, TX,
77843, USA
cAdjunct Faculty at the Chemical and Materials Engineering Department, King
Abdulaziz, Jeddah, Saudi Arabia
jmponce@umich.mx
Abstract
This work presents a mathematical programing formulation for the optimal management
of flowback water in shale gas wells considering economic and safety aspects. The
proposed formulation accounts for the time-based generation of the flowback water, as
well as the options for treatment, storage, reuse, and disposal. The economic objective
function is aimed at determining the minimum cost for the fresh water, treatment,
storage, disposals and transportation. The safety objective accounts for the risk
associated to a failure in the treatment units and its consequence in human deaths. In
this regard, the proposed method is able to consider different treatment units with
different operating efficiency factors, costs and risks. To carry out the water integration,
a recycle and reuse network is proposed. A given scheduling for the completion phases
of the wells is required to implement the proposed method. Finally, an example problem
is presented to show the applicability of the proposed method.
Keywords: Shale gas; Risk in hydraulic fracturing (fracking); Safety; Flowback water
reuse.
1. Introduction
Recently, substantial reserves of shale gas have been discovered around the world.
Hydraulic fracturing technologies have facilitated the production of shale gas trapped in
tight formations. According to the Energy Information Administration (EIA), by the
year 2035 shale gas is expected to provide about half of the total natural gas supply in
U.S.A. (EIA, 2012) The EIA also estimated that U.S.A. has enough natural and shale
gas to meet domestic electricity demands for 575 years at current electricity generation
levels. Certainly, this information highlights the importance and the enormous potential
of shale gas in the future. Even a recent study analyzed the impacts of shale gas in the
chemical industry and in the natural gas market (Siirola 2012). However, a major
challenge for the shale gas industry is associated to the water issues such as the supply
of the water requirements for hydraulic fracturing process (this step demands huge
amounts of water to be successfully implemented), the treatment for the flowback water

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Optimal Reuse of Flowback Wastewater in Shale Gas Fracking Operations
Considering Economic and Safety Aspects 945
Therefore, this work presents a mathematical programming formulation to determine
the optimal flowback water management system that minimizes the total annual cost,
which is composed by the costs of fresh water, treatment, storage, disposals (including
operating and capital costs) and transportation and at the same time minimizes the risks
involved in the potential failures of the treatment units. It is important to mention that
these two goals usually contradict each other and it can be possible to show the results
through Pareto curves. This behaviour is generated owing to a treatment unit with a high
efficiency factor to remove the pollutants has a high cost but at the same time a low risk
and vice versa. The proposed formulation considers fresh water consumption, flowback
water treatment, storage, reuse, and disposal. The proposed method considers a fixed
scheduling for the completion operations to implement the approach. Additionally, the
scheme shown in Figure 2 is proposed to carry out the water integration for the
flowback water in hydraulic fracturing operations. As can be seen, the fresh water is the
primary resource to satisfy the water demands in wells; however the flowback water can
be reused in the hydraulic fracturing operations. Notice that the flowback water
obtained is sent to the interception network, which is composed by a set of treatment
technologies as well as it can be directly disposed. Finally, at the exit of the treatment,
the fluid can be stored or disposed.
2. Model formulation
The optimization formulation accounts for the mathematical relationships required to
model all the balances involved in the proposed superstructure, the relationships needed
to determine the capacity and existence of the units and the objective functions. To meet
the size requirements for this paper, here only are described the objective functions.
2.1. Economic objective function
The total annual cost (TAC) is constituted by the sum of the total operational cost (TOC)
and the total capital cost (TCC):
M
in TAC TOC TCC (1)
Figure 2. Schematic representati on of the proposed superstructure for the water management.

946 L.F. Lira-Barragán et al.
Whereas TOC is composed by the fresh water cost in addition to the operational
treatment unit cost and the transportation cost for all the trajectories considered
(freshwater resource-wells, wells-treatments, treatments-disposals, treatments-storage
and storage-wells):
_ _ _ _ _
_ _ _ _
fresh op treat trans fresh trans fb trans treat dis
trans treat sto trans sto well
TOC Cost Cost Cost Cost Cost
Cost Cost
(2)
Finally, TCC is composed by the capital costs for treatment and storage units and
disposals:
treat wa ste storage
TCC CapCost CapCost CapCost (3)
2.2. Environmental objective function
An important environmental criteria in this project is represented by the total water
requirements (TWR) of fresh water to complete all the desired wells:
time fresh
t
t
TWR H F (4)
2.3. Safety objective function
In this paper, the safety function it is based on the individual risk, and it is related to the
exposure of polluted flowback water at different concentration levels. This risk depends
on the capacity of the treatment units as follows:
_ _
, ,
treat cap well treat
i
i n i t
i n t
i
IR
RiskT F ff (5)
3. Results and discussion
The applicability of the proposed mathematical programming model is shown through
the following example.
Case Study
It is well known that U.S.A. has increased significantly the shale gas production in
recent years. In this regard, Marcellus (located mainly in Pennsylvania) and Barnett
(located in Texas) plays are considered among the largest shale gas reserves. It is
important to mention that most of the information required to implement the proposed
method in this case study has been taken from technical reports with updated data for
the Marcellus and Barnett regions (see Slutz et al. 2012). In this example, the water
management is optimized in time periods of a week with a time horizon of 52 weeks (a
year) and the completion for each well takes 5 weeks; in addition, an average value of
15,000 m3 is used in this work for the water requirements in the completion of each well
and approximately 25 % of the water injected during the hydraulic fracturing is
collected over several days following to the hydraulic fracturing (mainly in the three
weeks after the completion process). Thus, the flowrate required in each well during the
completion time is 428.57 m3/d; while the flowback water obtained after this phase has

Optimal Reuse of Flowback Wastewater in Shale Gas Fracking Operations
Considering Economic and Safety Aspects 947
a value of 342.86 m3/d, 150 m3/d and 42.85 m3/d only for the first three weeks,
respectively. Furthermore, 20 wells must be completed by three hydraulic fracturing
crews according to the scheduling shown in Figure 3. In this figure, the hydraulic
fracturing crew 1 completes the wells 1-8, hydraulic fracturing crew 2 works the wells
9-15 and finally crew 3 operates the wells 16-20. Besides, at the beginning two
hydraulic fracturing crews are working; after a few weeks the three crews can operate.
Nevertheless, approximately in the middle of the year the operation of any crew is not
allowed owing to the water scarcity and gradually when the water availability permits
the hydraulic fracturing crews restart the operations. It is noteworthy that the scheduling
performance is strongly dependent on the historical limitations of the available fresh
water. Also, notice that the transition time required to move the hydraulic fracturing
crew from a well to the next one is a week. On the other hand, the time conversion
factor (Htime) is 7 d/w, kF=0.1, the volumetric efficiency factor ( treat
i) for the treatment
units is 0.9 as well as there is not initial volume in the storage/pits units ( _
s
torage i nitial
s
V).
Also, other relevant information is that the treatment units, storage units and final
disposals considered in this example are typically employed in the existing shale gas
plays.
Thus, the treatment unit accounted ensures a quality for the outlet stream enough to be
reused or disposed under adequate environmentally conditions. In addition, among the
common options to store the flowback water are pits and hydraulic fracturing tanks;
however this last represents an unfeasible option for this specific case owing to the
enormous volumes that represent the flowback water storage of 20 wells compared with
the hydraulic fracturing tank capacities. Whereas the final disposal is carried out
through typical Class II wells. Other important information is required to implement the
proposed method. Once the optimization process is carried out, the Pareto curve shown
in Figure 4 is generated.
Figure 3. Scheduling for the completion phase in each well.
Figure 4. Pareto solutions for the economic and risk objectives.
3.5
3.7
3.9
4.1
4.3
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
TAC, MM
Risk, x10-5
Pareto Curve

948 L.F. Lira-Barragán et al.
As can be seen, the total cost is contradicted to the risk objective, and there is an
increase of approximately 23.8% with respect to the configuration with the highest risk
(4.57x105) and the minimum risk (1.79x10-5). This curve is useful for decision-makers
in order to select balanced designs with adequate costs and risks.
4. Conclusions
This work has proposed a new mathematical programming model for the optimal water
management in shale gas production accounting for economic and safety criteria. The
economic objective function consists in minimizing the total annual cost, which is
composed by the operating and capital costs. The safety goal is aimed at minimizing the
total individual risks (through synthesizing recycle/reuse networks). Also, it is
considered and quantified the total fresh water requirements as well as there were
included satisfy and environmental regulations for the pollutant concentrations for the
wastewater streams discharged to the environment (environmental targets). Notice that
this last aspect represents a relevant environmental improvement owing to usually
existing shale gas plays do not treat their waste streams and consequently environmental
problems have been generated. Moreover, the proposed method determines the number
and type of treatment technologies, storage pits and disposal required in the optimal
configuration as well as their capacities. A Pareto curve is employed to show the trade-
offs among the environmental and safety objectives where the decision makers can
select the final design considering both objectives.
References
J. Martinez-Gomez, O. Burgara-Montero, J.M. Ponce-Ortega, F. Nápoles-Rivera, M. Serna-
González, M.M. El-Halwagi, 2013, On the environmental, economic and safety optimization
of distributed treatment systems for industrial effluents discharged to watersheds, Journal of
Loss Prevention in the Process Industries, 26, 908-923.
J. E. Santibañez-Aguilar, J. Martinez-Gomez, J. M. Ponce-Ortega, F. Napoles-Rivera, Serna-
Gonzalez, 2015, An optimal planning for the reuse of municipal solid waste considering
economic, environmental, and safety objectives, Computer Aided Chemical Engineering, 33,
10271032.
J.J. Siirola, 2014, The impact of shale gas in the chemical industry, AIChE Journal, 60, 810819.
J. Slutz, J. Anderson, R. Broderick, P. Horner, 2012, Key shale gas water management strategies:
an economic assessment tool, SPE/APPEA International Conference on Health, Safety, and
Environment in Oil and Gas Exploration and Production, Perth, Australia.
L. Yang, I.E. Grossmann, J. Manno, 2014, Optimi zation models for shale gas water management.
AIChE Journal, 60, 10, 3490-3501
U.S. Energy Information Administration (EIA), 2012, U.S. 2012 Annual Energy Outlook with
Projects to 2035, Washington, DC, US Department of Energy.
Y.Yaoa, T. Chenc, S.S. Shend, Y. Niub, T.L. DesMarais, R. Linn, E. Saunders, Z. Fan, P. Lioye,
T. Kluz, L.C. Chenb, Z. Wuf, M. Costab,2015, Malignant human cell transformation of
Marcellus Shale gas drilling flow back water, Toxicology and Applied Pharmacology, 228(1),
121130.