SPE-174118-MS Water Management: What We Have Learned and What We Need to Consider for Developing a Shale Play in Argentina Juan Carlos Bonapace, Halliburton; Facundo Alric, Adrian Angeloni and Luciano Zangari, Total Austral Copyright 2015, Society of Petroleum Engineers This paper was prepared for presentation at the SPE Latin American and Caribbean Health, Safety, Environment and Sustainability Conference held in Bogotá, Colombia, 7–8 July 2015. This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright. Abstract Hydraulic fracturing has been active in Argentina since the 1960s. The first jobs were performed using oil-based fluids. Throughout the years, new water-based fluids were introduced to replace alcohol-based fluids and foams based on reservoir requirements, economics, and safety and environmental issues. Currently, more than 95% of hydraulic fractures performed in the country are made using aqueous-based fluids. Recently, exploration and development of resource shale plays, such as the Vaca Muerta, have begun. To achieve commercial production, this type of reservoir must be stimulated by hydraulic fracturing using large volumes of water. From 2009 to present, various exploration techniques have been performed in different shales, such as Los Molles, Vaca Muerta, Agrio (Neuquén Basin), Cacheuta (Cuyo Basin), and the D-129 (Golfo San Jorge Basin). This paper discusses aspects of water logistics necessary during the well completion phase, fracture treatment designs applied in Vaca Muerta, and laboratory studies performed on flowback and produced waters to help evaluate the potential for water reuse. The focus is on three different phases of water cycles for these projects. • Water sources and stimulation: information for vertical and horizontal wells based on physical-chemical characteristics of various freshwater for stimulation, volume of water used, type of fracture treatment, and fracture fluid and additives used. • Logistics: evolution of different water storage and transport options used for shale projects on single or multiple well pads. • Reuse of flowback and produced water: laboratory tests on different flowback and produced water and/or blends (freshwater-flowback-water), treated and untreated including: ‒ Physico-chemical characteristic of water (flowback and produced) from different wells. ‒ Formation sensitivity tests with different water sources and usage possibilities. ‒ Fracture fluids, conventional borate fluids, and a new low-residue CMHPG-metal formulated fluid using no traditional water treated and untreated with high total dissolved solids (TDS). Introduction Well stimulation using hydraulic fracturing has been widely used for producing oil and gas reservoirs in Argentina since the 1960s. This stimulation technique has been applied in the five hydrocarbon producing basins shown in Fig. 1, as well as in a variety of formations and types of reservoirs, such as conventional, tight, and more recently in shale (hydrocarbon source rock). The hydraulic fractures created in Argentina present a variety of conditions and challenges related to depth (from 300 to 4,500 m), bottomhole temperature (BHT) (100 to 300°F), reservoir pressure (from subnormal to overpressure), formation permeability (high, medium, low, and ultralow perm), multilayer reservoirs, and multitarget wells. Throughout the years, there have been noticeable changes to the types of treatment and wells in which fracturing fluids are used, from oil-based systems, alcohol-water mixtures, and foams, to water-based fluids currently used. The steady increase in drilling activity and, therefore, well completion and stimulation has led to increased water consumption; thus, alternatives have been sought to help minimize this impact in certain basins. Bonapace et al. (2012) documents the use of
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
SPE-174118-MS
Water Management: What We Have Learned and What We Need to Consider for Developing a Shale Play in Argentina Juan Carlos Bonapace, Halliburton; Facundo Alric, Adrian Angeloni and Luciano Zangari, Total Austral
Copyright 2015, Society of Petroleum Engineers This paper was prepared for presentation at the SPE Latin American and Caribbean Health, Safety, Environment and Sustainability Conference held in Bogotá, Colombia, 7–8 July 2015. This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright.
Abstract Hydraulic fracturing has been active in Argentina since the 1960s. The first jobs were performed using oil-based fluids.
Throughout the years, new water-based fluids were introduced to replace alcohol-based fluids and foams based on reservoir
requirements, economics, and safety and environmental issues. Currently, more than 95% of hydraulic fractures performed in
the country are made using aqueous-based fluids.
Recently, exploration and development of resource shale plays, such as the Vaca Muerta, have begun. To achieve
commercial production, this type of reservoir must be stimulated by hydraulic fracturing using large volumes of water. From
2009 to present, various exploration techniques have been performed in different shales, such as Los Molles, Vaca Muerta,
Agrio (Neuquén Basin), Cacheuta (Cuyo Basin), and the D-129 (Golfo San Jorge Basin).
This paper discusses aspects of water logistics necessary during the well completion phase, fracture treatment designs
applied in Vaca Muerta, and laboratory studies performed on flowback and produced waters to help evaluate the potential for
water reuse.
The focus is on three different phases of water cycles for these projects.
• Water sources and stimulation: information for vertical and horizontal wells based on physical-chemical
characteristics of various freshwater for stimulation, volume of water used, type of fracture treatment, and
fracture fluid and additives used.
• Logistics: evolution of different water storage and transport options used for shale projects on single or multiple
well pads.
• Reuse of flowback and produced water: laboratory tests on different flowback and produced water and/or blends
(freshwater-flowback-water), treated and untreated including:
‒ Physico-chemical characteristic of water (flowback and produced) from different wells.
‒ Formation sensitivity tests with different water sources and usage possibilities.
‒ Fracture fluids, conventional borate fluids, and a new low-residue CMHPG-metal formulated fluid using no
traditional water treated and untreated with high total dissolved solids (TDS).
Introduction Well stimulation using hydraulic fracturing has been widely used for producing oil and gas reservoirs in Argentina since the
1960s. This stimulation technique has been applied in the five hydrocarbon producing basins shown in Fig. 1, as well as in a
variety of formations and types of reservoirs, such as conventional, tight, and more recently in shale (hydrocarbon source
rock). The hydraulic fractures created in Argentina present a variety of conditions and challenges related to depth (from 300
to 4,500 m), bottomhole temperature (BHT) (100 to 300°F), reservoir pressure (from subnormal to overpressure), formation
permeability (high, medium, low, and ultralow perm), multilayer reservoirs, and multitarget wells.
Throughout the years, there have been noticeable changes to the types of treatment and wells in which fracturing fluids
are used, from oil-based systems, alcohol-water mixtures, and foams, to water-based fluids currently used. The steady
increase in drilling activity and, therefore, well completion and stimulation has led to increased water consumption; thus,
alternatives have been sought to help minimize this impact in certain basins. Bonapace et al. (2012) documents the use of
2 SPE-174118-MS
produced water for use in a fracturing fluid in the Golfo San Jorge Basin, managing to replace 55% of freshwater
consumption.
Early work (hydraulic fractures) to develop Argentina’s shale basins was conducted during 2010. The majority of
exploration and development has been in the Vaca Muerta formation, but work has also been assessed in other formations,
such as Los Molles, Cacheuta, D-129 and Agrio more recently. Experience gained related to water management in these shale
plays during the completion of more than 40 wells (>200 hydraulic fractures) by different operators is presented.
Furthermore, laboratory studies were conducted on treated and untreated flowback waters and their assessment for use as
fracturing fluid water is presented.
Fig. 1—Map of five hydrocarbon producing basins discussed.
Water Sources and Stimulation Currently, Argentina’s largest shale reservoir development is the Neuquén Basin in the Vaca Muerta formation; however,
development has been performed in other plays, such as training in the Los Molles, Agrio, some stimulation in the Cuyo
Basin (Cacheuta formation), and in the Golfo San Jorge Basin (D-129 formation). These basins have a history of
conventional reservoir development and corresponding stimulation techniques (primarily hydraulic fracturing). Thus, water
sources normally used for these developments (conventional reservoirs) are the same as those used during the early stages of
exploration and subsequent development of shale reservoirs. Some particularities in terms of water type have been observed
in such exploration wells for other plays. In the Los Molles formation, a mixture of fresh water (85%) and produced water
(15%) was used because of the large volume of water necessary for hydraulic fracturing of a 10 stage horizontal well. For the
completion in the D-129 formation, the operator decided to use 100% produced water (low salinity < 10,000 TDS) to run all
the stimulation treatments (five fracture stages).
Given the economic potential of the Vaca Muerta play, the focus lies on this reservoir. Considering its vast extension in
the Neuquén Basin, the Vaca Muerta comprises many fields exploited at levels located below or above the Vaca Muerta by
several operators. This helps because some fields and operators have existing surface facilities; this is favorable during the
exploration and development phases of this shale in relation to the logistics of water.
The primary sources of water in the Neuquén Basin used to develop these hydrocarbon resources are rivers (Neuquén,
Limay, Colorado), lakes, or reservoirs (Cerro Colorado, Pellegrini), or groundwater sources, such as wells with low salinity
(< 5,000 TDS). These types of wells for water supply need a permit from regulatory authority and produced water is not
suitable for human consumption or farmlanding.
SPE-174118-MS 3
Physical-Chemical Analysis. Table 1 presents a summary of different water sources that have been used during stimulation
in the Vaca Muerta. It presents the primary feature chemical of these sources, which have been identified according to
operator, field, and nature (surface or underground). Additionally, the first column presents the requirements for fresh water
to be used as the base element of a fracturing fluid (according to service company standards).
Fresh Water
Field Water Requirements
Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 A B#a B#b B#c C
Water Source Type River River River River River Well Well Well Well River
Table 1—Summary of various sources of water used during stimulation in the Vaca Muerta.
As Table 1 depicts, the underground water sources (wells) are higher than surface sources (rivers) in terms of pH, TDS,
total suspended solids (TSS), chlorides, sulphates, bicarbonates, and sodium. However, all referenced water sources meet the
requirements established to be used in fracturing fluids. Five samples of water from the Neuquén River (different points of
location) are included as references and comparison.
Types of Treatment. The most common hydraulic fracturing treatments performed in different plays in Argentina were
hybrid fracturing designs. Fig. 2A presents average water volumes per stage (m3) for various shales in Argentina and types of
reservoir fluids. Additionally, Fig. 2B presents corresponding percentages according to the fluid system used, distribution of
slickwater (SW), linear gel (LG), and crosslinked gel (XL). In general, it can be observed that the greatest volumes of water
(m3) by stage correspond to reservoirs of gas and wet-gas (Fig. 2A red and yellow bars), being hybrid treatment designs for
both SW-LG (Los Molles) and SW-LG-XL (Vaca Muerta).
4 SPE-174118-MS
Fig. 2—(A) average water volume per stage (m3); (B) percentage according to fracturing fluid type.
A statistical analysis regarding the type of hydraulic fracture in Vaca Muerta was performed for six fields, A, B, C, D, E,
and F. Fig. 3 shows more detail for the treatments performed in these wells based on reservoir fluid composition. A total of
13 wells and more than 65 hydraulic fractures were analyzed. In general, average water volume per stage (Fig. 3A) varied
according the fluid reservoir; for oil wells, average water volume was 1300 m3; it was 1850 m
3 for wet gas; and 2180 m
3 for
gas wells. Fig. 3B presents the fracturing fluid distribution for each. The fracturing treatments were primarily hybrid SW-XL,
where in some cases used SW-LG-XL; the percentages of most systems ranged from 30 (oil) to 84% (gas) for slickwater and
70 (oil) to 10% (gas) for crosslinked systems. LG was commonly used as a contingency in the transition from SW to XL.
Small percentages were used (less 10%) based on the pressure response during the treatment and reservoir conditions.
Normally, the completion of a Vaca Muerta well has involved a total water volume of ~ 6500 m3 for vertical wells and
~14500 m3 for horizontal wells.
Fig. 3—(A) average water volume per stage (m3); (B) percentage based on fracturing fluid type.
SPE-174118-MS 5
Types of Systems. These systems used fresh water and contained chemical additives to provide various functions:
• SW: contained friction reducer and friction reducer breaker.
• LG: contained gelling agent, buffer, and breaker.
• XL: consisted of buffer, gelling agent, crosslinker, and breaker (usually used a 20-lbm/1000 gal XL guar-borate
fluid.
• Additionally, each of the fluid systems also typically contained a biocide, clay inhibition, and surfactant additives.
Specific surfactants were selected according to reservoir fluid type (oil, wet gas, and gas).
Yang et al. (2013) and Patel et al. (2014) presented a detailed analysis of the evolution of fracturing fluid designs,
fracturing fluids, water consumption, chemical additives, and proppant used for different basins in the US. This information
is valuable for identifying tendencies or changes in these points in other US shale plays.
Logistics During the past five years, there has been substantial progress related to water management and logistics for sustainable
development of Argentina’s shale plays. A variety of water storage systems and methods for transferring water (trucks, pipe
systems) have been used in the Neuquén Basin associated with operations, primarily in the de Vaca Muerta. Various models
of water management were used by numerous operators and depended on the stage or phase of activity (exploration or pilot
phase), type of completion (vertical, horizontal, or recompletion wells), surface facilities existing in the fields, geographical
location, and proximity to available water sources. Water storage systems have been primarily mobile fracture tanks (80 m3)
(Fig. 4B), circular tanks (1,000 to 5,500 m3) (Fig. 4A), and lined pits (15,000 to 35,000 m
3) (Figs. 4C and D). The
movement of water has been performed primarily by trucks, and some operators have built transfer systems using piping
(tubing or aluminum pipe) and centrifugal pumps.
Currently, the most common storage systems used are mobile fracture tanks and circular tanks. Pits utilization are
restricted for environmental restrictions. A greater number of suppliers of fracture tanks have been incorporated in the last
years, and also, the incorporation of new technologies in circular tanks (easy assembly, portables, and greater capabilities).
Fig. 4—(A) circular tank (6000 m3); (B) fracture tanks (6000 m
3); (C) small pit (15000 m
3); (D) large pit (35000 m
3).
Following is a discussion of varying cases of water management plans and logistics developed for vertical wells during
the initial stage of exploration, as well as cases for horizontal wells under development.
First Vertical Well The first well in Vaca Muerta was drilled in A Field, which has a very good infrastructure attributed to development wells in
tight formations. The completion of the well consisted of four hydraulic fractures stages, requiring of 7600 m3 of total water.
6 SPE-174118-MS
Alternatives were evaluated for the logistic and water management; finally, it was decided to install a transfer system through
pipes and a water storage location close to the well to be stimulated (Fig. 5).
A water well (groundwater with low salinity) was used for source water located in the same field with production flow of
1200 m3/D. A circular tank for water storage of up to 1000 m
3 was located within the vicinity. This well was 7.5 km away
from the well to be stimulated. The operator performed the laying of a 4 in. pipe from the water well to the water storage
location, in which there were installed two circular tanks of 2000 m3 capacity (Fig. 6A). Water was pumped from the well to
the location using centrifugal pumps. The service company provided a water transfer system (Figs. 6B and 6C) between the
storage location and the stimulation wellsite, 350 m of distance, consisting of two lines of 8-in. aluminum pipe and two
centrifugal pumps with a pumping capacity of 40 to 67 bbl/min. At the location of the vertical well, mobile fracture tanks
were placed (Figs. 6D and 6E) with a total storage capacity of 2000 m3. Before starting the stimulation, a water volume of
6000 m3 was available (frac tank and water location tanks were completely filled; Fig. 5); additionally, as a backup, recharge
water was onsite by means of trucks.
Fig. 5—Water management plan for first vertical well completion.
Fig. 6—Water management plan for first vertical well completion.
Vertical and Horizontal Well The second vertical well in Vaca Muerta was drilled in Field B; as the first well, this field has a very good infrastructure. The
completion consisted of four hydraulic fracture stages, requiring of 8000 m3 of water. For the stimulation of this well, it was
decided to drill a new water well (groundwater and non-potable water) close to the wellsite and apply the same water
management strategy. The water well (Fig. 7A) finally was drilled at 300 m from the wellsite and had a flow capacity of
2,000 m3/D (natural production). To complete the vertical well, a mobile fracture tank was installed in the water well location
to store water and a centrifugal pump. The water storage was transferred from the frac tank to the wellsite using one line of
aluminum pipe (8 in.) and a centrifugal pump. In the wellsite, the water was stored in three circular tanks (each had a capacity
of 1000 m3) and 15 mobile frac tanks (Figs. 7B and C), a total storage capacity of 4500 m
3 was available at the location.
SPE-174118-MS 7
Fig. 7— Water management plan for second vertical well completion.
The first horizontal well completion in Field B consisted of six fracture stages, consuming a total volume of water of
13000 m3. It was decided to use part of the infrastructure built for the vertical for the horizontal well drilled 1.5 km from the
water well (Fig. 8). The water plan involved taking water from the water well and transferring and storing it in the location of
vertical well (water location). Based on the amount of water needed, it was necessary to install a new circular tank with more
capacity (total storage capacity 3200 m3). Then, the water was transferred to the wellsite using a centrifugal pump and
aluminum pipe. The horizontal well had total water capacity storage of 5000 m3 (circular tank and mobile fracture tanks). For
this job, the service company was in charge of water logistics and it was necessary to transfer a portion of the water in real
time.
Fig. 8—Water management plan for horizontal well completion.
Use and Reuse of Flowback, Produced, and Treated Water This section analyzes the possibility of using water nontraditionally (flowback and produced), either treated or untreated.
Various alternatives uses include (a) flowback and produced water untreated; (b) mixing dilution water (flowback-produced)
untreated with fresh water; (c) and treated water.
Laboratory studies were conducted to evaluate different alternatives for the use of these nontraditional waters as suitable
for fracturing fluids, primarily for use in a XL gel system. The tests performed included:
• Detailed water (physical-chemical) analysis.
• Clay swelling and inhibition testing.
• Evaluation and development of XL fluids, proppant transport capacity.
• Damage by gel residue and TSS.
8 SPE-174118-MS
Physical-Chemical Analysis. Table 2 presents a summary of different flowback and produced waters labeled by different
fields in the Vaca Muerta formation. The same primary physico-chemical variables can be observed for these waters.