American Oil and Gas Reporter - February 2018 - 68

SpecialReport: Advancing Shale Science

Managing Water Crucial In Shale Plays
By Faruk Civan
LA HABRA, CA.-Successfully implementing effective water handling systems is a complicated task that relies on
balancing a number of engineering, economic and environmental concerns. Optimizing the management of the water
cycle requires scientifically guided approaches to achieve a comprehensive understanding of overall field water resources
and issues of relevance in proper water
characterization and processing.
Specific elements of successful strategies include centralizing water management facilities, using alternative sources
to freshwater, employing green completion
designs, and streamlining logistics and
transportation.
One of the challenges is quantitatively
accounting of water volumes to accommodate flexibility in balancing water supply and demand under dynamic reservoir
and field conditions. This requires:
* Combining permanent, temporary
and portable treatment technologies;
* Monitoring and diagnosing the
water cycle under dynamic operating conditions;
* Effective data assimilation;
* Wastewater abatement aided by dynamic systems simulations; and
* Integrating engineering- and economics-based analyses in field water handling.
Optimizing the economic value of the

water cycle in shale reservoirs is particularly
challenging given the large volumes of
water required during well completion and
the amount of fluid flowed back from the
reservoir during the early production phase.
Defining The Issues
Water issues in oil and gas operations
can be classified into two general categories: Managing natural water sourced
from rivers, lakes, coastal waters and
groundwater aquifers, and handling
wastewater generated during drilling,
completion and production processes.
For natural water, the important issues
include availability, accessibility, compatibility and injectivity of available
supplies. The main issues for wastewater
are generation, quality, quantity, continuity and composition.
One of the major trends defining upstream water management is the move to
recycle and reuse produced and flowback
waters for various purposes, including
well completion, pressure maintenance
and enhanced oil recovery, as well as potential nonindustry beneficial applications
such as agriculture, and even drinking
water after purifying. In this sense, the
industry no longer considers pro duced/flowback waters as "waste" that
must be disposed of, but as a source of
supply that must be recovered and
processed in the most cost-effective and
environmentally responsible manner.
There are three main aspects involved

FIGURE 1A

in water processing: Water characterization
(present and required quality), treatment
methods (in situ versus surface processes,
parameters, quality, capacity, separated
materials, sludge, etc.), and equipment
(gas/liquid/particulate separation, storage,
transportation and measurement).
The primary damaging compounds
that may be present in wastewater streams
are sand, solid particulates (precipitates,
asphaltenes and paraffins), corrosion
products, and oil droplets. The larger
the quantity of the produced water
stream, the bigger the scale of precipitation, sand production and corrosion
problems, increasing the operational
costs required to handle and process
the water to treat/remove contaminants.
That includes all the necessary lifting,
separating, processing, storage and transportation equipment.
In addition, there are water handling
challenges specific to low-permeability,
porous media such as shales. Typically,
the water present in shale pore space is in
the forms of clay-bound water, capillarybound water, and mobile water (Figure
1A). During the hydraulic fracturing
process, water-based frac fluid is introduced
under pressure into the near-wellbore
reservoir formation, and becomes mostly
trapped in the formation. When production
commences, a portion of that trapped
water gradually is flowed back with the
produced hydrocarbons (Figure 1B).
Fracturing fluid entrapment can cause

FIGURE 1B

Water and Gas Contained in Shale

Adsorbed and
Dissolved Gas

Free Gas
Kerogen

Natural and
Induced
Fractures
Inorganic
Matter

Clay-Bound, CapillaryBound, and Mobile Waters
68 THE AMERICAN OIL & GAS REPORTER

Hydraulic Fracturing
Water Flowback
American Oil and Gas Reporter - February 2018

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