Analysis of Environmental Aspects of Exploiting Unconventional Reservoirs
This paper presents an analysis of the environmental aspects of the exploitation of unconventional reservoirs in order to evaluate the risk of the activity.
This paper presents an analysis of the environmental aspects of the exploitation of unconventional reservoirs in order to evaluate the risk of the activity. To this end, the existing normative framework, the natural and socioeconomic conditions of the area, and the applicable technologies are considered. The novelty of this work is the analysis of the factors that determine the environmental risk including technologies, environmental conditions at the site, and the legal context in the region.
A review and comparative analysis was performed of the general and environmental regulatory framework in Argentina where unconventional exploration or exploitation activities are carried out. This analysis was completed with a review of the effluent-management strategy, comparing it with criteria used by other countries, especially the United States.
In order to perform a preliminary evaluation of the environmental risk, a structured, conceptual, and qualitative analysis was conducted in specific sectors corresponding to each of the areas of exploration and exploitation.
Depending on the information available at the regional level, and based on the analysis of satellite images, each site was characterized according to 20 parameters. Parameters 1–9 represented the natural physical environment, 10–13 represented biotic or ecological factors, and 14–20 represented human environment:
- Temperature—Low temperatures result in a longer time for recovery; biochemical processes are slower. Extreme temperatures result in operational technological challenges.
- Precipitation—High levels of precipitation make the land less stable, raising the risk of water erosion, landslides, torrential phenomena, floods, and other extreme events.
- Contour—Abrupt land contour changes increase the risk of erosion, landslide, or mass removal.
- Wind—Frequent and intense winds increase the dispersion of atmospheric pollutants, especially particulate matter, and can lead to potential contamination of populated or productive areas.
- Water Depth—Deeper groundwater increases the risk of contamination by intentional or accidental spills, as well as contact with hazardous substances.
- Wetlands—The proximity to wetlands (e.g., streams, rivers, lakes, and ponds) increases the risk of contamination by intentional or accidental spill.
- Water Resources—The availability of water resources affects hydraulic-fracturing operations.
- Land Quality—High-quality land results in greater risk to the environment from an accidental spill or degradation from occupation, erosion, or contamination.
- Hydrologic Regime—Increased intermittence of the watercourse increases the risk of torrential activity, erosion, and flooding, raising the risk of accidents during the operation phase.
- Ecoregion—The type of ecoregion affects sensitivity and vulnerability.
- Physiognomic Diversity—A higher diversity of species or life forms increases the risk to more species because the ecosystem is more vulnerable and has a greater biotic wealth.
- Highland Ecosystems—High-altitude ecosystems are more vulnerable to human activity.
- Protected Ecosystems—Proximity to protected ecosystems or species with legal protection presents a greater risk of degradation and environmental damage.
- Infrastructure—The lack of roads or paved roads increases the risk of accidents and leads to necessary adaptation, increasing the environmental effects of the entire activity.
- Services—A deficiency in public services (e.g., energy, gas, water, and sewage) increases the risks and environmental effects associated with a greater human presence and an increase in the demand for natural resources.
- Waste Management—The availability of integrated solid-waste-management systems or special- or hazardous-waste-management systems increases the environmental risk of the activity by increasing the generation of waste.
- Populated Centers—Proximity to populated centers increases the risk of interference with local activities, the degradation of essential natural resources (e.g., water), the restriction of movement of people and goods, the competition for natural resources, the alteration of the local economy, and spontaneous immigration.
- Productive Areas—Proximity to areas of intense agricultural activity increases the risk of interference with local activities, alteration of the pattern of land use, degradation of resources, and competition for inputs and local labor.
- Territorial System—The intervention in unstructured territorial systems increases the risk of their degradation and the alteration of patterns of occupation and mobility.
- Historical Areas—Intervention in areas protected by their historical or archaeological value increases the risk of degradation or damage to local heritage.
For each of the 30 sites considered, each parameter or indicator was analyzed and a value was assigned on a scale of 1 to 5, corresponding to a lower (1) or greater (5) environmental risk.
Finally, an analysis of exploitation activity was conducted, identifying for each stage the main activities, risks, and environmental effects and possible mitigation measures. In addition, possible technologies for the treatment of flowback water and its reuse were analyzed with respect to their physical/chemical characteristics and the volume of water to be treated.
Results and Discussions
Environmental aspects are critical to the development of unconventional-hydrocarbon exploitation. In this context, environmental risk includes the set of factors related to environmental issues that can affect the activity.
The following three components make up the environmental risk of exploration and exploitation—the environmental regulatory framework, the conditions of the surrounding environment, and the technology used.
Evaluation of the Legal Framework. Different types of environmental regulations exist for the exploitation of hydrocarbons: general and specific rules for the activity and the sector. The Argentine National Constitution, Article 41, explicitly incorporates the right to a healthy, balanced environment suitable for human development so that productive activities satisfy present needs without compromising those of future generations. Other regulatory measures include national and provincial environmental laws that contain principles of environmental management.
Preliminary Environmental Site Assessment. The 20 indicators defined earlier were analyzed for each of the 30 selected sites. Remote sensing provided sufficient information on terrain and geoforms, land cover, type of vegetation, proximity to bodies of water, land uses (e.g., agriculture, livestock, and forest plantations), infrastructure (e.g., roads and electric lines), populated centers, areas of special management (e.g., natural protected areas and aboriginal territories), and territorial structure. It also allowed mapping of study areas. Complementing the analysis with a field visit to the area under study also can be useful.
The environmental assessment of the site, together with the evaluation of the regulations, allows for defining or adjusting the technological complexity and the environmental-management system to be used.
Analysis of Applicable Technologies. Technological innovation plays an important role in the development of unconventional hydrocarbons, to maximize volumes with minimal production costs and to consider and internalize the challenges of fulfilling the environmental norms and conditions, including natural and social aspects. In order to evaluate the influence of the technology used on environmental risk, the main stages of the activities were analyzed with identification of the environmental effects and mitigation measures for potential risks.
Although all stages of the activity may be relevant to environmental risk, the location of aquifers and the depth of reservoirs are critical during drilling, completion, and hydraulic fracturing. The completion of wells is the most critical stage because a barrier failure would cause contact between the hydrocarbon and the external environment.
The availability of water is another important factor. Drilling and fracturing requires a large volume of water, approximately 20,000 m3/d. The volume of water used in fracturing is rarely 1–2% of the total water used in the area; however, if the region is suffering from water shortages, any water extraction might cause concern to the public. In areas of severe water scarcity, recycling of produced water and mixing with high-salinity brines that are too saline for agricultural use is possible, and surprisingly effective and economical, in large-scale fracturing operations. Technology should play an important role in increasing the water efficiency of the activity.
Technology plays a fundamental role in all the stages involved in the exploitation of unconventional resources. Identifying those stages with greater risk potential is important in order to be able to enhance technical and other mitigation measures.
Environmental risk assessment is a useful tool at regional and subregional levels. It can be conducted with background information and can be complemented with information from remote sensing and, possibly, a visit to the area.
The result of the analysis of areas with unconventional reservoirs highlights the most-relevant environmental factors at risk. Together with the evaluation of regulations, the assessment allows for the identification of technological complexity or management systems and the areas with the highest and lowest levels of environmental risk. This allows for the identification, implementation, and development of potential mitigation measures with the objective of achieving sustainability.
This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 185546, “Importance of the Study of Environmental Aspects in the Exploitation of Unconventional Reservoirs for Risk Assessment of the Activity in Argentina,” by M.A. De La Zerda and E. Erdmann, SPE, Instituto Tecnológico de Buenos Aires, and R. Sarandón, Universidad Nacional de La Plata, prepared for the 2017 SPE Latin America and Caribbean Petroleum Engineering Conference, Buenos Aires, 17–19 May. The paper has not been peer reviewed.