Mitigating risks from hydraulic fracturing-induced seismicity in unconventional reservoirs: case study.
Ontology highlight
ABSTRACT:
SUBMITTER: Hui G
PROVIDER: S-EPMC9307861 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Models for hydraulic fracturing-induced earthquakes in shales typically ascribe fault activation to elevated pore pressure or increased shear stress; however, these mechanisms are incompatible with experiments and rate-state frictional models, which predict stable sliding (aseismic slip) on faults that penetrate rocks with high clay or total organic carbon. Recent studies further indicate that the earthquakes tend to nucleate over relatively short injection time scales and sufficiently far from the injection zone that triggering by either poroelastic stress changes or pore pressure diffusion is unlikely. Here, we invoke an alternative model based on recent laboratory and in situ experiments, wherein distal, unstable regions of a fault are progressively loaded by aseismic slip on proximal, stable regions stimulated by hydraulic fracturing. This model predicts that dynamic rupture initiates when the creep front impinges on a fault region where rock composition favors dynamic and slip rate weakening behavior.
| S-EPMC6713494 | biostudies-literature
Project description:Shale oil and gas exploitation by hydraulic fracturing experienced a strong development worldwide over the last years, accompanied by a substantial increase of related induced seismicity, either consequence of fracturing or wastewater injection. In Europe, unconventional hydrocarbon resources remain underdeveloped and their exploitation controversial. In UK, fracturing operations were stopped after the Mw 2.3 Blackpool induced earthquake; in Poland, operations were halted in 2017 due to adverse oil market conditions. One of the last operated well at Wysin, Poland, was monitored independently in the framework of the EU project SHEER, through a multidisciplinary system including seismic, water and air quality monitoring. The hybrid seismic network combines surface mini-arrays, broadband and shallow borehole sensors. This paper summarizes the outcomes of the seismological analysis of these data. Shallow artificial seismic noise sources were detected and located at the wellhead active during the fracturing stages. Local microseismicity was also detected, located and characterised, culminating in two events of Mw 1.0 and 0.5, occurring days after the stimulation in the vicinity of the operational well, but at very shallow depths. A sharp methane peak was detected ~19 hours after the Mw 0.5 event. No correlation was observed between injected volumes, seismicity and groundwater parameters.
| S-EPMC5988740 | biostudies-literature
Project description:During December 2011, a swarm of moderate-magnitude earthquakes was induced by hydraulic fracturing (HF) near Cardston, Alberta. Despite seismological associations linking these two processes, the hydrological and tectonic mechanisms involved remain unclear. In this study, we interpret a 3D reflection-seismic survey to delve into the geological factors related to these earthquakes. First, we document a basement-rooted fault on which the earthquake rupture occurred that extends above the targeted reservoir. Second, at the reservoir's stratigraphic level, anomalous subcircular features are recognized along the fault and are interpreted as resulting from fault-associated karst processes. These observations have implications for HF-induced seismicity, as they suggest hydraulic communication over a large (vertical) distance, reconciling the discrepancy between the culprit well trajectory and earthquake hypocenters. We speculate on how these newly identified geological factors could drive the sporadic appearance of induced seismicity and thus be utilized to avoid earthquake hazards.
| S-EPMC6205443 | biostudies-other
Project description:Hydraulic fracturing can improve the permeability of coalbed methane (CBM) reservoirs effectively, which is of great significance to the commercial production of CBM. However, the efficiency of hydraulic fracturing is affected by multiple factors. The mechanism of fracture initiation, morphology and propagation in CBM reservoirs is not clear and need to be further explored. Hydraulic fracturing experiment is an accurate tool to explore these mechanisms. The quantity of experimental coal rock is large and processing method is complex, so specimen made of similar materials was applied to replace coal rock. The true triaxial hydraulic fracturing experimental apparatus, 3D scanning device for coal rock section were applied to carry out hydraulic fracturing experiment. The results show that the initiation pressure is inversely proportional to the horizontal stress difference (??) and positively related to fracturing fluid injection rate. When vertical stress (?v) is constant, the initiation pressure and fracture width decrease with the increasing of ??. Natural fractures can be connected by main fracture when propagates perpendicular to the direction of minimum horizontal stress (?h), then secondary fractures and fracture network form in CBM reservoirs. When two stresses of crustal stress are close and far different from the third one, the fracture morphology and propagation become complex. Influenced by perforations and filtration of fracturing fluid in specimen, fracturing fluid flows to downward easily after comparing horizontal well fracturing with vertical well fracturing. Fracture width increases with the decreasing of elastic modulus, the intensity of fracture is positively related with the elastic modulus of coal rock. The research results can provide theoretical basis and technical support for the efficient development of CBM.
| S-EPMC5886525 | biostudies-literature
Project description:Hydraulic fracturing (HF) is a reservoir stimulation technique that has been widely deployed in recent years to increase the productivity of light oil and/or natural gas from organic-rich, low-permeability formations. Although the process of fracturing a rock typically results in microseismic events of magnitude < 0, many cases of felt seismic events (typically magnitude 3.0 or larger) have also been reported. In the Western Canada Sedimentary Basin (WCSB), where more than 40,000 wells have been drilled and hydraulically fractured in the past two decades, the occurrence of HF-induced events has surged in some areas. Yet, many other areas of the WCSB have not experienced a significant increase in induced seismicity, despite a sharp increase in both the number of HF wells and the volumes of injected fluid. The relationship between injected volume and induced magnitudes can be quantified using the seismic efficiency ratio (SEFF), which describes the ratio between the net seismic moment release and the injected fluid volume. Runaway rupture, in which the fault rupture is dominated by the release of accumulated tectonic stresses, is inferred to be marked by an abrupt increase in SEFF to a value > 0.5. Most previous studies of induced earthquakes have been limited to a single operation and/or seismicity sequence. To better understand the observed variability of the seismic response to HF stimulations at a basin scale, we compiled HF data for all unconventional wells hydraulic fractured in the WCSB between 2000 and 2020, together with the seismicity reported during the same period. We grouped these observations into bins measuring 0.2° in longitude and 0.1° in latitude, or approximately 13 by 11 km. We identified 14 areas where large magnitude events resulted in high SEFF values, implying runaway rupture had taken place. However, we find that in these areas, sustained fluid injection did not lead to persistent high SEFF values. Instead, as injection continued, SEFF values returned to values less than 0.5. This suggests that there is a limited budget of tectonic strain energy available to generate runaway rupture events: once this is released, event magnitudes decrease even if high volume injection persists.
| S-EPMC9402563 | biostudies-literature
Project description:Development of unconventional shale gas reservoirs (SGRs) has been boosted by the advancements in two key technologies: horizontal drilling and multi-stage hydraulic fracturing. A large number of multi-stage fractured horizontal wells (MsFHW) have been drilled to enhance reservoir production performance. Gas flow in SGRs is a multi-mechanism process, including: desorption, diffusion, and non-Darcy flow. The productivity of the SGRs with MsFHW is influenced by both reservoir conditions and hydraulic fracture properties. However, rare simulation work has been conducted for multi-stage hydraulic fractured SGRs. Most of them use well testing methods, which have too many unrealistic simplifications and assumptions. Also, no systematical work has been conducted considering all reasonable transport mechanisms. And there are very few works on sensitivity studies of uncertain parameters using real parameter ranges. Hence, a detailed and systematic study of reservoir simulation with MsFHW is still necessary. In this paper, a dual porosity model was constructed to estimate the effect of parameters on shale gas production with MsFHW. The simulation model was verified with the available field data from the Barnett Shale. The following mechanisms have been considered in this model: viscous flow, slip flow, Knudsen diffusion, and gas desorption. Langmuir isotherm was used to simulate the gas desorption process. Sensitivity analysis on SGRs' production performance with MsFHW has been conducted. Parameters influencing shale gas production were classified into two categories: reservoir parameters including matrix permeability, matrix porosity; and hydraulic fracture parameters including hydraulic fracture spacing, and fracture half-length. Typical ranges of matrix parameters have been reviewed. Sensitivity analysis have been conducted to analyze the effect of the above factors on the production performance of SGRs. Through comparison, it can be found that hydraulic fracture parameters are more sensitive compared with reservoir parameters. And reservoirs parameters mainly affect the later production period. However, the hydraulic fracture parameters have a significant effect on gas production from the early period. The results of this study can be used to improve the efficiency of history matching process. Also, it can contribute to the design and optimization of hydraulic fracture treatment design in unconventional SGRs.
| S-EPMC5761844 | biostudies-literature
Project description:The pulmonary inflammatory response to inhalation exposure to fracking sand dust (FSD) was investigated in a rat model. Adult male Sprague-Dawley rats were exposed by whole-body inhalation to air or an aerosol of FSD at concentrations of 10 or 30 mg/m3, 6 hours/day for 4 days. The control and FSD-exposed rats were euthanized at post-exposure time intervals of 1, 7 or 27days and pulmonary inflammatory, cytotoxic and oxidant responses were determined. Deposition of FSD particles was detected in the lungs of all the FSD-exposed rats. Analysis of bronchoalveolar lavage parameters of toxicity, oxidant generation, and inflammation did not reveal any significant persistent pulmonary toxicity in the FSD- exposed rats. Similarly, the lung histology of the FSD-exposed rats showed only minimal changes in influx of macrophages following the exposure. Determination of global gene expression profiles detected significant differential expressions of only six and five genes in the 10 mg/m3, 1 day post-exposure, and the 30 mg/m3, 7-day post-exposure FSD groups, respectively. Taken together, data obtained from the present study demonstrated that FSD inhalation exposure resulted in minimal/no toxicity or gene expression changes in the lungs of the rats.
2020-10-01 | GSE148255 | GEO
Project description:The use of hydraulic fracturing (HF) to extract oil and natural gas has increased, along with intensive discussions on the associated risks to human health. Three technical processes should be differentiated when evaluating human health risks, namely (1) drilling of the borehole, (2) hydraulic stimulation, and (3) gas or oil production. During the drilling phase, emissions such as NOx, NMVOCs (non-methane volatile organic compounds) as precursors for tropospheric ozone formation, and SOx have been shown to be higher compared to the subsequent phases. In relation to hydraulic stimulation, the toxicity of frac fluids is of relevance. More than 1100 compounds have been identified as components. A trend is to use fewer, less hazardous and more biodegradable substances; however, the use of hydrocarbons, such as kerosene and diesel, is still allowed in the USA. Methane in drinking water is of low toxicological relevance but may indicate inadequate integrity of the gas well. There is a great concern regarding the contamination of ground- and surface water during the production phase. Water that flows to the surface from oil and gas wells, so-called 'produced water', represents a mixture of flow-back, the injected frac fluid returning to the surface, and the reservoir water present in natural oil and gas deposits. Among numerous hazardous compounds, produced water may contain bromide, arsenic, strontium, mercury, barium, radioactive isotopes and organic compounds, particularly benzene, toluene, ethylbenzene and xylenes (BTEX). The sewage outflow, even from specialized treatment plants, may still contain critical concentrations of barium, strontium and arsenic. Evidence suggests that the quality of groundwater and surface water may be compromised by disposal of produced water. Particularly critical is the use of produced water for watering of agricultural areas, where persistent compounds may accumulate. Air contamination can occur as a result of several HF-associated activities. In addition to BTEX, 20 HF-associated air contaminants are group 1A or 1B carcinogens according to the IARC. In the U.S., oil and gas production (including conventional production) represents the second largest source of anthropogenic methane emissions. High-quality epidemiological studies are required, especially in light of recent observations of an association between childhood leukemia and multiple myeloma in the neighborhood of oil and gas production sites. In conclusion, (1) strong evidence supports the conclusion that frac fluids can lead to local environmental contamination; (2) while changes in the chemical composition of soil, water and air are likely to occur, the increased levels are still often below threshold values for safety; (3) point source pollution due to poor maintenance of wells and pipelines can be monitored and remedied; (4) risk assessment should be based on both hazard and exposure evaluation; (5) while the concentrations of frac fluid chemicals are low, some are known carcinogens; therefore, thorough, well-designed studies are needed to assess the risk to human health with high certainty; (6) HF can represent a health risk via long-lasting contamination of soil and water, when strict safety measures are not rigorously applied.
| S-EPMC7225182 | biostudies-literature
Project description:Hydraulic fracturing operations are generating considerable discussion about their potential to contaminate aquifers tapped by domestic groundwater wells. Groundwater wells located closer to hydraulically fractured wells are more likely to be exposed to contaminants derived from on-site spills and well-bore failures, should they occur. Nevertheless, the proximity of hydraulic fracturing operations to domestic groundwater wells is unknown. Here, we analyze the distance between domestic groundwater wells (public and self-supply) constructed between 2000 and 2014 and hydraulically fractured wells stimulated in 2014 in 14 states. We show that 37% of all recorded hydraulically fractured wells stimulated during 2014 exist within 2 km of at least one recently constructed (2000-2014) domestic groundwater well. Furthermore, we identify 11 counties where most ([Formula: see text]50%) recorded domestic groundwater wells exist within 2 km of one or more hydraulically fractured wells stimulated during 2014. Our findings suggest that understanding how frequently hydraulic fracturing operations impact groundwater quality is of widespread importance to drinking water safety in many areas where hydraulic fracturing is common. We also identify 236 counties where most recorded domestic groundwater wells exist within 2 km of one or more recorded oil and gas wells producing during 2014. Our analysis identifies hotspots where both conventional and unconventional oil and gas wells frequently exist near recorded domestic groundwater wells that may be targeted for further water-quality monitoring.
| S-EPMC5740626 | biostudies-literature
Project description:Hydraulic fracturing plays an important role in the commercial development of unconventional oil and gas, which is directly related to the production of oil and gas wells. An accurate evaluation is critical for hydraulic fracturing, but it is urgent to propose a quantitative assessment of hydraulic fracturing fracture propagation for realizing hydraulic fracturing fracture propagation and multiposition permeability measurement under an in situ stress environment. Herein, a true triaxial stress loading and permeability testing device was designed and fabricated, and a permeability evaluation model was established under various states, which can realize the accurate measurement of multiple faces and the total permeability of tight specimens before and after hydraulic fracturing. It can directly measure permeability under the conditions of the true triaxial fracture propagation experiment. The comparative experimental result shows that the new technique can quantitatively evaluate the fracture propagation experiment of true triaxial hydraulic fracturing. The overall permeability and the directional permeability of the five faces were obtained, and the fracture propagation was evaluated by comparing the change in permeability. The test permeability error rate is within ±10%. Furthermore, a more refined evaluation of hydraulic fracturing fracture propagation can be carried out based on the fracture observation and AE event results. The research results provide a new strategy for a more quantitative and refined evaluation of fracture propagation and help to optimize the parameters of hydraulic fracturing.
| S-EPMC9366778 | biostudies-literature