Regarding the dramatic increase of water additional resource administration in numerous drilling industries’ operational performances and oil/gas extractions, water supply plays a significant role in their performances as efficient as optimum operations, in respect of the way, this utilization is often invisible to the public eye. The necessity of water in a wide variety of drilling operation due to its vast applicant in several functions is widely reported in the literature that has been required to remain these procedures plateau. Department of Petroleum Engineering, Islamic Azad University, Science and Research Branch, Tehran, Iran
Received: 12 September 2017 / Accepted: 17 April 2018
© The Author(s) 2018
Regarding the dramatic increase of water additional resource administration in numerous drilling industries’ operational performances and oil/gas extractions, water supply plays a significant role in their performances as efficient as optimum operations, in respect of the way, this utilization is often invisible to the public eye. The necessity of water in a wide variety of drilling operation due to its vast applicant in several functions is widely reported in the literature that has been required to remain these procedures plateau.
Department of Petroleum Engineering, Islamic Azad University, Science and Research Branch, Tehran, Iran
The objective of this comprehensive study is to conduct an investigation into the studied field and analyze the assessment of necessary water and produced water which is provided in the surface for reinjection procedures in the hydraulic fracturing and water injectivity; in respect of the way, petroleum and drilling industries will push themselves into limits to find suitable water sources from a local source to encapsulate their economic prosperities and virtually eliminate extra expenditures.
In comparison to other industries and consumers, oil and gas development is not a significant water consumer, and its water demands can exert profound impacts on local water resources, and this is why it imposes particular challenges among water users in a vast majority of fields and areas in times of drought. Moreover, water has become an increasingly scarce and costly commodity over the past decades, and operators are being beneficially noted that awareness of recycling and reusing phenomenon that has treated effluent is both costs competent and socially responsible. Consequently, energy, environmental situation, and economic prosperity considerations should be analytically and preferably investigated to cover every eventuality and each possibility of disposal and water reuse options.
The volume of total freshwater consumption by individuals in the earth is only 2.5%, because most of it (97.5%) which is too salty for human use, that is to say, that just less than 1% of this fresh water is available for direct human consumption. Due to continual population growth, agricultural and industrial developments, and climate change effects, water resource scarcity has become a critical issue in many parts of the world (Arnell and Lloyd-Hughes 2014; Fischer et al. 2017; Freyman 2014; Gallegos et al. 2015; Pedro-Monzonís et al. 2015). The cost of rig water could be relatively inexpensive in those regions where there is abundant local access to rivers or lakes, and local regulations permit withdrawal, in respect of the way, petroleum operators are trying to achieve to cheap water which is dwindling and companies have to search further to access rig water (Kondash and Vengosh 2015; Nicot and Scanlon 2012; Nicot et al. 2014; Scanlon et al. 2014a, b).
Water reuse offers an enormous chance for operators to access to independent sources of water which it is dependable on some occasions. Furthermore, it would be locally controlled and play a significant role in the environmentally friendly use. The proportionality of water resource distribution in each category is demonstrated in Figs. 1, 2, and 3. As can be seen in Fig. 1, the volume of fresh water is 1/32 of saline water in the earth, and this amount would be drastically decreased shortly due to the vast consumption of fresh water by individuals and numerous industries (Davarpanah et al. 2018).
Fig. 1 Percentage of earth’s water sources
Fig. 2 Percentage of freshwater sources.
Fig. 3 Percentage of surface freshwater sources
The distribution of freshwater and surface fresh water is depicted in Figs. 2 and 3, respectively.
Each year, the total volume of produced wastewater by petroleum industries are exceeded more than 800 billion gallons. These wastewater productions contain the large volumes generated wastewater over the life of the well and massive volumes of water which is urgently needed in hydraulic fracturing performances (Davarpanah and Nassabeh 2017a, b; Scanlon et al. 2013a, b; 2014a, b; 2015). Hydraulic fracturing is a controlled operation that pumps fluid and a propping agent through the wellbore to the target geological formation at high pressure in multiple intervals or stages, to create fractures in the formation and facilitate production of hydrocarbons.
Hydraulic fracturing is a safe and proven way to develop natural gas and oil; it has been used throughout the oil and gas industry for about 60 years. Therefore, water usages and the water reuse in petroleum industries have become one of the significant concerns in petroleum exploration and production industries as an energy issue. Water exercise plays a dominant influence in the life cycle of petroleum industries as below:
– considered as the cooling equipment in mud circulation which helps to cool the drill bit and carries rock cutting out of the borehole;
– hydraulic fracturing;
– enhanced oil recovery techniques;
– water flooding;
– steam-assisted gravity drainage (SAGD) (Clark and Veil 2009; Holt et al. 2009).
Two of the main challenges of petroleum industries are providing the sufficient amount and appropriate quality of water and find novel solutions to properly manage the wastewater generation. Wastewater composition in most of the cases is being categorized as follows:
– high dissolved organic matter, including volatile compounds and hydrocarbons;
– high salt content (often > 35 g/L);
– metals (e.g., iron, manganese, calcium, magnesium, barium, etc.);
– dissolved gases (e.g., H2S);
naturally occurring radioactive material (NORM);
– high concentrations of suspended solids, oil, and grease(Chen and Carter 2016; Davarpanah and Nassabeh 2017a, b; Dubiel et al. 2012; Engle et al. 2014; Esser et al. 2015).
There are four methodologies and techniques of waste management which are addressed to improve the quality of produced or injected water during drilling operations that have entailed reduce, recycle, reuse, and recover. Reduce is the generation of less waste through more efficient practices such as process modification, use of non-toxic additives, inventory control, and management. Recycle/reuse is to convert waste back into a product such as burning waste oil for energy, oily wastes for road construction and stabilization, recycling drilling muds, and recycling scrap metals. Recover is extracting materials or energy from waste such as recovery of oil from tank bottoms and sludges (Glassman et al. 2011). These four parameters are followed by waste treatment and disposal.
The treatment utilizes techniques to minimize the amount and toxicity of waste to minimize the amount that has to be disposed of. For waste disposal, environmentally sound and approved methods should be used. Regarding local geology, there are million tons of in situ water which are produced by production operations on the surficial wellbore equipment and significant amount of these waters are separated by powerful equipment; however, these obtained water sources may contain chemical pollutants, heavy metals, oily particles, etc., which have potentially devastating effects on the environmental processes and they will not be capable for human treatments due to their toxic and detrimental effects.
One of the primary reasons of this issue is that operators may add many chemicals to this fluid to make the process more productive. Another underlying assumption which is to be elaborated about this phenomenon would be natural salty water that is trapped in the rock matrixes. Thereby, a large volume of this water is transferred to the surface. The possibility of assessing the dire consequences of fossil and hydrocarbon fuel development on the water life cycle are being investigated and widely reviewed by numerous scientists and engineers to optimize the maximum water reuse in operations; these extensive studies include water management practices; recycling, treatment, disposal of wastewater, and the impacts on the watershed and surrounding environment. Reuse and recycling processes are practiced by petroleum companies; in such areas, there are restriction rules for disposal wells and freshwater is more expensive and harder to find (Kharaka et al. 1988).
Lots of water sources in petroleum industries include produced water, refinery wastewater, marketing terminal water, ground water, storm water, parking lot runoff, plenty of off-the-shelf treatments, and unlimited supply of applications. These steps are being illustrated graphically in the PFD diagram in Fig. 4.
Fig. 4 Typical water treatment PFD (Kharaka et al. 1988)
Oil and gas wastewater treatment is considered as one of the leading pollution possibilities owing to including a broad variety mixture of salt and suspended solids in high concentrations, metals such as arsenic and barium, organics like hydrocarbon compounds, and potentially naturally occurring radioactive material. It is of paramount importance to clarify the hazardous risks of this toxicity appropriately and control their mobilization, and study their occurrence dispersion, their settlement time in the environment and their corrosive effects on the food chain.
Some “light-treatment” techniques are widely administered in petroleum industries which most of these treatment methodologies have determined when wastewater treating is entirely variable, and its appropriate application is prohibitively expensive to construct, operate, and maintain. Thereby, a few acceptance standards due to how to identify what is in each waste stream and which adequate methods to clean this are being presented. One of the main steps in the rapid acceleration of water reuse is the advent of advanced membrane treatment methodologies, and their cost reductions are classified into four categories;
– membrane technologies include microfiltration (MF).
– ultrafiltration (UF).
– nanofiltration (NF).
– reverse osmosis (RO) (Orem et al. 2014).
Using MF or UF in municipal wastewater reuse, especially for RO pretreatment, started to multiply in the late 1990s. Nowadays, the integrated utilization of MF and UF with RO has widely available and has reached a standard in municipal advanced recycled water projects, especially for indirect potable water reuse cases where the recycled water is re-injected to the groundwater aquifer to augment the existing water sources. Historically, petrochemical plants and refineries have used RO as pretreatment for ion exchange demineralizers to produce pure water for boiler feed and process uses. Since 1999, more than ten UF systems have been installed as pretreatment for RO in petrol facilities for boiler feed-water demineralization. RO, in the form of VSEP (vibratory shear enhancing processing), has also been used in the full scale for removing selenium from stripped sour water to help a large refinery meet stringent discharge requirements. In addition, there are other types of preparing techniques for separating solids and other particles from water which are necessary to reuse it again in drilling and operational performances.
These techniques are dilution, filtration, and centrifugation, liquid–liquid extraction (LLE), support-assisted liquid–liquid extraction (Al Dabaj et al. 2018), solid-phase extraction (Oetjen et al. 2017, 2018), and solid-phase micro-extraction (SPME). Dilution serves the purpose of two significant principles: lessen the sample viscosity which plays a vital role on the analysis of water injections and flow backs; in respect of the way, viscosity reduction causes the enhancement of re-productivity. Furthermore, dilution procedures altered the matrixes of the sample and prompted to have more compatibility with further analyzing. Filtration and centrifugation are other kinds of separation for virtually eliminating the particulate components to deal more compatibility with the analytical methodologies. Moreover, filtration processes would not have the ability of dissolved fractional component alteration (Ferrer and Thurman 2015; Mitra 2004; Oetjen et al. 2017, 2018; Rodriguez-Aller et al. 2016; Thurman et al. 2017).
Production from unconventional shale oil and gas plays
Accumulations of hydrocarbons such as oil and gas in natural conventional and unconventional reservoirs throughout the world which most of them were migrated from clean fine-grained, dark-gray, or black organic-rich sedimentary source rocks were referred to organic-rich shales. Over the past decades, organic-rich shale formations have been considered as the source rocks in petroleum reservoirs, that is to say, that, hydrocarbons originated and migrated into sandstone and limestone of various reservoir qualities, because unconventional reservoirs have low permeability than other reservoirs and have less economic volumes of oil and gas produced in oilfields. To produce commercial quantities from the unconventional reservoirs, a combination of increased oil and gas prices and improved technology of horizontal drilling and multi-stage fracturing are required (Rabbani et al. 2018; Rowan et al. 2015; Thacker et al. 2015).
Produced water reuse and recycling in some of the oilfields
Produced water in two of the Barnett shale reservoirs which are located in the northern portion of Pennsylvania is being studied, and their comparison between them is clarified as below to continue to minimize the amount of freshwater utilization in drilling and production operations; in respect of the way, it lessened the extra expenditures of freshwater supplements (Mantell 2011):
– Shale field-1 water reuse
In this field, produced water has generally had higher levels of TDS, low amounts of TSS, and moderate scaling tendency; that is to say, that, in this field, the volume of water reused and treated by membrane treatment techniques is relatively 8% of the total amount of water which is used for drilling and hydraulic fracturing operations. However, water reuse treatments play a significant role in production and drilling operations; logistical and economical performances impose specific restrictions in the administration of large volume of water reuse in this field (Jin et al. 2017; Mantell 2011).
– Shale field-2 water reuse
In this field, produced water has generally had lower levels of TDS, moderate amounts of TSS, and low scaling tendency; that is to say, that, in this field, the volume of water reused and treated by membrane treatment techniques is relatively 8% of the total amount of water which is used for drilling and hydraulic fracturing operations with water reuse production with a target goal of 23% reuse in the play. Regarding low levels of TSS, it does not urgently need of specific filtration before reuse operation. In comparison to the previous category, logistical and economical performances impose particular restrictions in the administration of large volume of water reuse in this field (Horner et al. 2016; Mantell 2011).
Total dissolved solids (TDS) are being used for the following purposes:
– It is used as a measurement of inorganic salts, organic matter, and other dissolved materials in water.
– It is used as a secondary drinking water contaminant.
– It can cause some operational problems for drinking water systems.
– It can cause toxicity to aquatic life through increases in salinity, changes in the ionic composition of the water, and the toxicity of individual ions.
– Significant sources of TDS are being found in:
– steel industry;
– pharmaceutical manufacturing;
– mining operations;
– oil and gas extraction;
– some power plants;
– food processing facilities (Wilson and VanBriesen 2012).
Although there are numerous studies and research activities which are widely reported in the literature to emphasize the importance of flow-back waters, in this comprehensive study, the author is tried to investigate the water treatment of shale reservoirs and how to provide sufficient water utilization for each well by the optimization of each procedure. Furthermore, by serving the purpose of water reuse in drilling and exploration industries, the administration of fresh water is virtually reduced and subsequently will help to the water scarcity in the world.
Methodology and application of produced water reuse
The vertical wells to be drilled were exploration wells in the southwest Iran’s oilfield which is called South-Aban oilfield that could provide information on potential reservoirs and lithological data of the field. This oilfield unit distributed into the Asmari, Pabdeh, Gorpey, Ilam, and Sarvak formations which are located in the Cheshmeh-Khosh operational field. No offset data were available on the well, and the nearest well information was 80 km away. Geologist forecast from this well required drilling through reactive shales in the member. It produces a smaller volume of produced water initially (compared to the other significant plays) and has inferior quality produced water.
It has had higher levels of TDS and high amounts of TSS, and produced water has high scaling tendency. In this field, low produced water volumes, poor produced water quality, and the resulting economics have prevented successful reuse of produced water. However, due to the large volumes of higher quality drilling wastewater generated during the drilling process, it is actively exploring options to reuse this wastewater in subsequent drilling and fracturing operations.
The studied field entails seven production wells which three of them are located in the gas shale layer (well-05–07), and other wells are drilled horizontally on the oil shale layers. The reason for drilling the wells in the horizontal form is that high potentiality of wells for hydraulic fracturing regarding the high connectivity of the fractures and cracks has successfully operated. The production performance for each well is schematically demonstrated in Figs. 5, 6, and 7 to espouse the importance of productivity rate for each well.
Fig. 5 Oil production rate for each well
Fig. 6 Water production rate for each well
Fig. 7 Gas production rate for each well