Browsing by Author "Eaton, David W. S."
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Item Open Access 3D Geological Modeling from Concept Sketches and Annotations(2017) Mendonça Amorim, Ronan; Costa Sousa, Mário; Famil Samavati, Faramarz; Eaton, David W. S.; Sharlin, Ehud; Katz, Larry; Mould, DavidDuring the early stages of any design project, specialists explore and refine ideas collaboratively by constructing conceptual models through hand-drawn sketches and renderings. The resulting models are then used to make decisions before moving to the detailed design phase of development. Sketch-Based Interfaces and Modeling (SBIM) is an area of research devoted to the development of computational tools to aid in this prototyping process. The main goal of SBIM is to construct models directly from hand-drawn sketches, leveraging the sketching skills of experts in different domains such as art, science, and engineering. In this thesis, I investigate the theory and practice of concept sketching applied to the problem of constructing conceptual models of geological structures describing subsurface environments. Geological models describe the disposition, geometry, and types of rocks in the subsurface, and are critical to a wide range of applications, such as oil/gas exploration. Current subsurface modeling workflows lack more interpretive and interactive modeling tools, which could enable experts to rapidly construct a variety of digital conceptual geological models directly from their interpretation sketches. In this thesis, I am addressing fundamental research in SBIM motivated by the challenges of constructing conceptual geological models from 2D hand-drawn sketches. This thesis explores the use of SBIM to complement existing geological modeling tools with more interpretive and interactive methods, with the goal of expediting the construction of concept geological structures described at the early stages of subsurface modeling. To this end, two new SBIM methods are proposed: (1) Geo-Editor aims to enable experts to more easily and rapidly edit/augment existing geological surfaces, using sketches directly in 3D with/without geological data. (2) Geo-Sketcher complements the previous approach by allowing the rapid construction of conceptual geological models from a blank-screen environment using rule-based SBIM. It leverages the standard language provided by geological and topographic maps to provide experts with a familiar notation for sketching. The results and feedback from domain experts demonstrate that the proposed methods can significantly reduce the time necessary to create or edit 3D geological models.Item Open Access An Integrated geophysical study of Valhalla gneiss complex, southeastern British Columbia(1988) Eaton, David W. S.; Cook, Frederick A.LITHOPROBE seismic reflection data in combination with petrophysical, aeromagnetic and gravity data have been used to study crustal structure beneath Valhalla gneiss complex, a Cordilleran metamorphic core complex in southeastern British Columbia. The region is characterized by a thin crust relative to most parts of North America, high surface heat flux and elevated lower crustal and/or upper mantle electrical conductivity, and is tectonically interposed between a convergent plate margin along Canada' s west coast and the stable North American craton to the east. Laboratory measurements of rock properties coupled with observed seismic reflections from mylonite zones suggest that mylonite reflectivity is influenced by interdependent strain related changes in density, velocity and p-wave anisotropy and elucidates some aspects of the more general problem of the nature of reflections in crystalline terranes. Ma.gnetic susceptibility measurements have been used to correlate aeromagnetic anomalies with exposed rock units. Bandpass filtering has been applied to the aeromagnetic data in order to further classify anomalies on the basis of wavenumber spectrum, and upward continuation of the data has been used to investigate the depth extent of Eocene Coryell intrusions. Regional/residual separation of Bouguer gravity data based on a best fit quadratic surface indicates that the Valhalla gneiss complex is coincident with a 15 mGal gravity high. Two dimensional numerical modelling of this gravity feature suggests that the area is underlain by rocks with a bulk density of 2710 kg/m3 . This inferred density value along with the absence of a pronounced regional aeromagnetic signature implies that "typical" oceanic basement is not present in the upper crust beneath Valhalla gneiss complex. Reprocessing of LITHOPROBE seismic line SCC-5 traversing the Valhalla gneiss complex has been undertaken to clarify a number of features important for the interpretation. A very high amplitude west dipping reflection beneath the Valhalla gneiss complex is imaged on line SCC-5. The Valhalla reflection may originate from the buried Gwillim Creek shear zone, a significant thrust-related mylonite zone that is exposed 30 km north of the seismic profile. A minimum of 20 km of overlap between two pairs of reflection zones separated by the Valhalla reflection supports the interpretation that the Valhalla reflection images a significant thrust fault. A convex upward narrow bandwidth reflection at 12 s two way time on the west side of line SCC-5 is interpreted to originate from the Moho, suggesting that the base of the crust undulates in depth, perhaps partially accounting for the virtual absence of Moho reflections elsewhere on this survey. The lower crust is both non-reflective and electrically conductive beneath the Valhalla gneiss complex, in contrast to other regions of high lower crustal conductivity where a reflective lower crust is often predominant. The combination of geophysical techniques used in this investigation illustrates the usefulness of adopting an interdisciplinary approach for studies of the earth' s crust.Item Open Access Comparison of convolutional neural networks with matched-filtering for detection of induced seismicity(2019-08-19) Vragov, Volodymyr; Eaton, David W. S.; Trad, Daniel O.; Krebes, Edward StephenThe problem of extracting weak earthquake signals from continuous waveforms data recorded by networks of seismic sensors, referred to as earthquake detection, is a challenging and critical task in seismology. Waveform cross-correlation (matched-filtering) is a widely used method to detect weak earthquake signals with waveforms similar to those of known events. Even using this method, earthquake catalogs are often limited and incomplete, so there is a need for a more general detector. Because earthquakes occur infrequently, detection algorithms must be capable of quick processing of months to years of continuous data dominated by noise. To address these challenges, we propose to use convolutional neural networks, a new detection method that utilizes large seismic datasets to perform computationally efficient search to identify events in the continuous data. We set up an algorithm as a supervised machine learning problem and test its performance against matched-filtering based detector on synthetic and Kaybob-Duvernay region data. In this work, I introduce a DuverNet, which is an optimized convolutional neural network for the detection of induced seismicity in the Kaybob-Duvernay production region. First, I test two different convolutional neural network architectures: ConvNetQuake and VGG-Junior. Second, I test two different loss functions: cross-entropy loss and focal loss. My thesis is the first time focal loss is used to tackle class imbalance problem in earthquake detection. Focal loss helps tackling the problem of class imbalance and allows to achieve higher accuracy for convolutional neural network detectors. Third, I compare performance of matched-filtering and DuverNet. After allowing time for appropriate training, DuverNet performs best in computational runtime and memory use. Moreover it delivers superior detection performance compared to the matched-filtering detector. Synthetic data testing illustrates that DuverNet better generalizes to previously unseen events and is found to be better at detecting more events at lower signal-to-noise ratio compared to the matched-filtering method. Finally, my thesis introduces a novel dataset collected by the 6 UC/DSA array stations installed by Nanometrics for the University of Calgary.Item Open Access Double-Difference Seismic Event Relocation: A Study of the Applications and Limitations of the Relocation Problem(2024-08-12) Biegel, Katherine M.; Dettmer, Jan; Eaton, David W. S.; Gilbert, Hersh Joseph; Innanen, Kristopher A. H.; Kao, HonnEarthquake relocation provides refined earthquake catalogs based on additional considerations or data beyond the initial earthquake location estimates. Double-difference relocation, in particular, utilizes the assumption that ray paths in close proximity to one another will pass through a similar earth velocity structure. The method minimizes the residual difference for pairs of these travel time observations to refine event locations. This thesis focuses on the application of three double-difference methods based on differing geometries of data pairing: event-pair relocation, station-pair relocation, and double-pair relocation. In this thesis, I introduce a previously unavailable software, relocDD-py, that implements all three of these relocation methods along with a complete workflow, including data preparation, automated variable selection, and post-relocation uncertainty analysis. This software is developed in Python using many widely implemented Python packages to allow for integration into existing seismic workflows. In addition, I present studies that apply this software and methodology at various scales, including (1) a large-scale tectonic study of complex plate subduction and the resulting seismicity in Alaska and Yukon where we find direct evidence of the Totschunda-Fairweather Connector fault; (2) a regionally observed induced seismicity event with analysis of the entire earthquake sequence from Peace River, Alberta where we find activation of multiple sub-parallel faults; and finally (3) a densely monitored induced seismicity experiment which ruptured a complex network of pre-existing faults near Fox Creek, Alberta where we find limits on the depth of seismicity to the hydraulic fracturing depth. Double-difference relocation can improve existing catalogs even in sparsely monitored areas and can reduce relative location uncertainty to such a degree that detailed three-dimensional interpretation of fault structures is possible. In many cases, event-pair relocation, the most widely applied double-difference method, is sufficient to improve relative uncertainties and maintain absolute location uncertainties. However, in cases with complex velocity models and dense monitoring, the double-pair method can improve relative uncertainties beyond event-pair relocation, which may identify additional seismicity features. The double-pair method is more computationally expensive and, therefore, is not necessary in all cases. All three double-difference relocation methods have an important role to play in earthquake and other seismic event relocation and catalog refinement. My work provides a software tool and a standardized workflow for the implementation of double-difference relocation in seismic studies.Item Open Access Effects of Nanopores on Carbon Dioxide Enhanced Oil Recovery in Tight Oil Reservoirs(2017) Zhang, Kai; Chen, Zhangxing (John); Azaiez, Jalel; Chen, Shengnan; Eaton, David W. S.; Patil, Shirish L.Horizontal well drilling with multi-stage hydraulic fracturing is mainly applied in tight oil exploitation. In some tight carbonate reservoirs like Pekisko, acidizing is applied. The primary recovery factor, however, remains below 10% even with advanced technologies. Water flooding has also been proposed for tight oil development, but water can form a membrane up to 43 nm, which tremendously hinders water injectivity. A CO2 miscible process seems a promising technique to enhance tight oil recovery. The mechanism of CO2-oil miscibility is the separation of oil molecules by the CO2 introduced; van der Waals forces that hold the oil molecules together need to be overcome. The process is similar to the vaporization of a liquid. The energy added into the liquid is used to overcome the van der Waals forces that hold the molecules of the liquid together, separate the liquid molecules and split them into the gas phase. In a nanoscale pore medium, variations in molecular orientation and molecules arrangement result in an alteration in the van der Waals forces, thereby creating unique thermal dynamic properties. These contribute to changes in CO2-oil miscibility compared to that in conventional reservoirs. At present, no systematical study addresses CO2-oil miscibility in nanopores. To unlock the mysteries of CO2 in enhanced oil recovery (EOR) in nanopores, the interactions between nanopores and molecules are studied using armchair, a zig-zag carbon nanotube, cubic shape smooth and rough nano-channels, and nano-channels with a functional group OH. The molecules trajectory and potential energy can be recorded by molecular dynamics simulations. The CO2-oil miscibility in nanopores is further presented including phase equilibrium, vaporizing and condensing drive, immiscible and miscible processes, and solubility parameters. The nanopore effect can be applied in screening candidate reservoirs for CO2 flooding and in selecting CO2 parameters by reservoir simulations. The thesis can be very revealing to researchers in the area of CO2-oil miscibility in nanopores.Item Open Access Examination of Shallow Structure in Geothermal Sites of Western Canada Using Microtremor Measurements: Mount Meager and Burwash Landing Case Studies(2024-02-15) Berumen Borrego, Fernando; Gilbert, Hersh Joseph; Dettmer, Jan; Eaton, David W. S.Canada has enormous geothermal potential, a sustainable alternative energy in the form of heat. Despite its significant role in moving Canada closer to net-zero CO2 goals, geothermal resource production faces numerous exploration challenges, notably the risks associated with drilling. However, with the emergence of new technologies, e.g., closed-loop systems and declining costs, geothermal energy is increasingly competing with conventional resources like coal. This thesis investigates the use of the Horizontal-to-Vertical Spectral Ratio (HVSR) method, also known as Nakamura’s method or microtremor HVSR (mHVSR), in two geothermal exploration projects. Commonly referred to as HVSR in the geophysical community, this method analyzes microtremors and is effective in determining seismic structures up to 200 meters deep at Mount Meager and 500 meters at Burwash Landing. HVSR complements other geophysical methods that focus on deeper structures and overcomes the limitations of surface geology. At Mount Meager, British Columbia, HVSR has been instrumental in identifying resonance frequencies and understanding the subsurface structure. It has revealed the variability in the shallow subsurface, aiding in the estimation of volcanic unit thicknesses and expanding upon existing geological and seismic data. This has enhanced the understanding of subsurface geology and associated risks. In Burwash Landing, Yukon Territory, where geothermal energy is crucial for local energy needs, the application of a trans-dimensional Bayesian inversion algorithm on HVSR curves has provided detailed insights into seismic structures. This method has offered accurate estimations of bedrock depth and sediment compaction, refining previous interpretations. Notably, it helped correct overestimated sediment layer thicknesses encountered during a drilling operation in November 2022. The trans-dimensional approach avoids the use of predefined models, quantifies uncertainty, and adds objectivity to interpretations. Overall, these studies highlight the importance of HVSR in geothermal exploration, especially in areas with complex topography and geology. HVSR is crucial for understanding shallow structures, assessing associated hazards, and informing studies on deeper geothermal resources. The findings significantly contribute to the understanding of seismic structures in these regions, with broader implications for global sustainability, energy self-sufficiency, and environmental objectives.Item Open Access Innovative seismic workflows for characterizing unconventional shale resource plays(2019-08-16) Sharma, Ritesh Kumar; Lines, Larry R.; Sacchi, Mauricio D.; Maini, B. B.; Trad, Daniel O.; Lawton, Don C.; Eaton, David W. S.Over the last five to seven years the characterization and exploitation of shale formations have led to a more dominating role for the engineers, ahead of geoscientists. A common perception is that in shale formations of interest, horizontal wells can be drilled anywhere in any direction, and completed at regular intervals along their lengths, a process referred to as ‘factory drilling’. The economics of such shale plays may have been the driving factor for such practices, but studies have shown that factory drilling should be replaced with smart drilling, which entails optimum placement and stimulation of the laterals, resulting in more uniform production. Reservoir quality (RQ) defined by organic richness, effective porosity, fluid saturation, pore pressure and gas-in-place, and completion quality (CQ) represented by in-situ stress field, mineralogy (clay content and type), and the presence of natural fractures as well as their orientation, must be considered in planning strategic hydraulic stimulation for increasing the total production of a horizontal well. As many of these properties can be estimated from seismic data, they can be integrated by introducing the concept of shale capacity, which is defined as the ability of a shale play to produce hydrocarbons, once it gets fractured. In this thesis, the usual challenges faced by geoscientists in computing individual components of shale capacity and their solutions have been highlighted by considering different datasets from different basins in North America. For instance, an important property of the formation of interest is its brittleness, and the usual criterion for its determination is to look for pockets that exhibit low Poisson’s ratio and high Young’s modulus. Though not difficult to compute, this combination is not found to be favourable in every shale play. Consequently, after highlighting the fallacy in following such a criterion a new attribute is proposed that makes use of strain energy density and fracture toughness. While the former controls fracture initiation, the iii propagation of fractures is governed by the latter. As hydraulic fracturing comprises both these properties, it is firmly believed that the new proposed attributes could be used to highlight the favorable intervals for fracturing. This work is followed by an alternative way of integrating key parameters of shale capacity, helping understand the variability in the well performance. It is firmly believed that geoscientists can not only stay relevant but can play a crucial role in improving the overall completion effectiveness and economics of shale plays.Item Open Access Moment-Tensor Analysis of Seismicity Related to Hydraulic Fracturing in North America(2019-01-30) Zhang, Hongliang; Eaton, David W. S.; Innanen, Kristopher A.; Gilbert, Hersh J.; Lines, Laurence R.; Zhang, HaijiangVarious types of seismic arrays are being used to monitor seismicity associated with oil and gas operations. These different types of recording systems exhibit significantly different characteristics in azimuthal coverage, magnitude detection threshold, signal-to-noise ratio and waveform frequency content. Taking these factors into account, this thesis focuses on implementing source-mechanism inversions for three typical monitoring geometries including the regional seismic network, sparse surface array and dense shallow borehole array. With the aim of investigating potential indicators for the discrimination between fluid-injection induced seismicity and natural earthquakes in the Western Canada Sedimentary Basin, the waveform-fitting-based moment-tensor inversion is performed for eight induced earthquakes with M > 3 and a nearby M 5.3 inferred natural earthquake, all of which were recorded by regional seismic networks. Based on the inverted parameters, the focal depth is found to be the most robust for parameter to distinguish the induced seismicity from natural earthquakes since the induced events considered here are significantly shallower than one observed nature event and most intraplate earthquakes in the Canadian Shield. Moreover, in addition to a dominant double-couple (DC) mechanism this is common to nearly all events, non-negligible non-DC components (typically > 25%) are observed within the moment-tensor solutions for most of the induced events. To overcome limitations of typically low signal-to-noise ratio and poor azimuthal coverage for the sparse surface array, a novel regularized approach is developed to estimate a composite focal mechanism from a set of microearthquakes recorded by this type of array. It operates by minimizing the weighted misfits of both SH/P amplitude ratios (in absolute sense and logarithmic scale) and P-wave polarities, using a regularization parameter determined from the trade-off curve for these values. The regularized approach reduces the multiplicity of solutions and avoids the use of signed amplitude ratios, which may be ambiguous for data with low signal-to-noise ratio. For the hydraulic-fracturing induced event sequences recorded by a dense shallow borehole array near Fox Creek area, a least-squares inversion based on 3C P-wave amplitudes has been implemented, which avoids fitting the relatively high-frequency waveforms and the picking of S-wave amplitudes that are contaminated by P-wave coda. The recovered source mechanisms are dominantly strike-slip with sub-vertical nodal planes, although a distinct cluster of events is characterized by more complex mechanisms with slip on a shallow-dipping plane accompanied by significant (> 30%) non-DC components. The non-DC components may be due to tensile crack opening and/or co-slipping on several fault strands that have been mapped using 3D seismic data. In addition, in the absence of direct stress measurements, moment-tensor solutions of the hydraulic-fracturing induced event sequences are used to estimate the local stress field near the Fox Creek area. The estimated orientation of SHmax differs from the median regional SHmax direction by ~ 15º, but it agrees with the nearest available borehole measurement from the World Stress Map. Mohr circle analysis indicates that N-S trending faults, which hosted the largest events (MW > 1.5), are mis-oriented for slip and required a relatively large increase in pore pressure (12 ± 4 MPa) in order to be brought to a state of incipient failure.Item Open Access Rock mass characterisation and the hydro-mechanical behaviour within interbedded low permeability reservoirs during hydraulic fracturing(2018-11-22) MacKay, Mason Keays; Eaton, David W. S.; Clarkson, Christopher R.; Pedersen, Per Kent; Lawton, Don C.Classification of the subsurface using a rock mass framework provides insight into reservoir behaviour because the combined characteristics of intact rock and the natural fracture system can be quantified. Rock mass classification is useful for reservoir characterisation because the primary factors affecting deformation and flow in a reservoir are included in the classification scheme, which can be applied across a range of rock formations. In this dissertation, heterogeneous low-permeability (‘tight’) reservoirs are classified according to their geological strength index value. This is achieved through outcrop mapping, microseismic analysis, core logging, wireline log analysis and geomechanical testing. These methods are applied to the prolific tight gas/oil Duvernay Shale reservoir in Western Canada. The rock mass classification framework is then used to assist in understanding how fluid propagates in the reservoir during hydraulic fracturing. Rather than a static diffusive process, the movement is hypothesised to occur episodically and dynamically in much the same way as the natural earthquake cycle moves fluid through the rock mass. Evidence of this behaviour is provided from microseismic observations during hydraulic fracturing treatments and through a novel technique to analyse pressure fluctuations during the stimulation treatment in the time-frequency domain. This method provides insight into fluid flow mechanisms occurring in fractured shale and tight rock reservoirs, and can be used to constrain before-closure flow-regime interpretations. A pressure-dependent rock mass Biot’s coefficient is derived from previously published empirical methods and verified through distinct element modelling techniques. Results from this study indicate that a critical fluid pressure can be achieved where the fracture system is fully connected and rock mass mobilization occurs. Under lower fluid pressures, pressure diffusion is more likely to occur rather than localized flow. The stiffness of the intact rock is observed to play an important role on how fluid becomes segmented within the reservoir. This research advances the concept of rock mass characterisation in low-permeability petroleum reservoirs and demonstrates how it can be used to understand the dynamic geomechanical system.Item Open Access Seismic Lithofacies Investigation of the Jurassic Plover Formation, North West Shelf, Australia using a Multi-Variate Process(2024-01-03) Green, Ryan Derochie; Pedersen, Per Kent; Hubbard, Stephen; Eaton, David W. S.To unravel the geologic sequence of events leading to the current configuration of Jurassic sediments of the Poseidon and Crown gas fields, Browse Basin, North West Shelf (NWS), Australia, a multi-variate, fully integrated workflow was developed. Basins undergoing extensional tectonics are often associated with igneous intrusions, volcanic tuffs, or basalt flows, these high amplitude features can resemble gas-filled sandstones or carbonate reefs in reflection seismic data. Basaltic intrusions are present throughout the Mid-Late Jurassic interval that contains reservoir-quality sandstones in the study area. This work will complement reservoir characterization studies required to support multi- trillion cubic feet (tcf.) of liquified natural gas (LNG) exports and associated carbon capture projects on the NWS. The study outlines the steps in workflow creation and evaluation of effectiveness. A seismic-stratigraphic framework was built to understand the tectonic influence on Jurassic strata. Within the framework, a multi-attribute, hierarchical seismic facies classification process, correlated to the seismic signature of wellbore lithologies, defines Seismic Cluster Facies (SCF). These were used in interpreting paleogeography and major geologic event timing.Item Open Access Seismic migration/inversion for transversely isotropic elastic media(1991) Eaton, David W. S.; Stewart, Robert R.Item Open Access Source Parameters and Tectonic Setting of the 2017 St. Elias Earthquake Sequence near the Southern Terminus of the Eastern Denali Fault, Northwestern Canada(2019-09-18) Choi, Minhee; Eaton, David W. S.; Enkelmann, Eva; Dettmer, Jan; Gilbert, Hersh J.On May 1, 2017 two earthquakes of magnitude 6.2 and 6.3, respectively, occurred in proximity to the eastern Denali fault (EDF). These double mainshock events were followed by more than 2,700 aftershocks. Moment-tensor inversion of the mainshock signals shows that the initial event produced reverse slip on a steeply dipping fault with a NW-SE strike direction, while the second produced left-lateral strike-slip on a near-vertical fault with an E-W strike direction. A double-difference relocation method, coupled with clustering analysis, was applied to the aftershock distribution, confirming that seismicity was localized along two previously unmapped fault structures. Stress inversion indicates that the maximum principal stress axis is oriented almost perpendicular to the EDF, suggesting that the fault system is not well oriented for strike-slip in the contemporary stress field. Coulomb stress analysis indicates that the second event was likely triggered by the first one (static stress triggering), with a delay of about two hours. A generalized model is developed to explain the observations, wherein gravitational potential from the >4,000 m high Mount Fairweather, as well as strain partitioning along the plate boundary, produce a stress regime that extends inboard towards the EDF.Item Open Access Towards improved hydraulic fracturing effectiveness through modelling and data integration: A case study from the Horn River Basin, BC(2018-03-28) Kent, Alana Hope; Eaton, David W. S.; Pedersen, Per Kent; Maxwell, Shawn C.Understanding how hydraulic fracture (HF) treatments affect a formation is crucial to ensure economical production in unconventional reservoirs. This thesis investigates an industry dataset from the Horn River Basin (HRB) that consists of microseismic (MS), reflection seismic, drilling, and completion data. Analysis of the MS reveals high variability in event clouds. While single monitor well bias is prominent in the magnitude statistics trends, kinked probability distributions and high outlier events suggest multiple mechanisms for MS generation. Spatial distributions are not classical bi-wing patterns but show lateral confinement, azimuthal variations, and out-of-zone growth. Stress heterogeneity is evident from variability in the instantaneous shut-in pressure (ISIP) and breakdown pressure values. The reflection seismic attributes of amplitude, most positive curvature (kpos), P-Wave impedance (Zp), and brittleness (BRI) show reservoir compartmentalization and are interpreted to account for irregular microseismic event growth. Deep MS growth is attributed to cross-cutting linear kpos trends and high values also appear to create a barrier; MS events arrest or curl to avoid positive anomalies. Rapid Zp transitions are also interpreted as a barrier and perforations in high zones correlate to rounded cloud growth and completion issues. In some situations, the high kpos and Zp values are co-located, suggesting that the impedance contrast is due to fractures. Both wells are in brittle areas but BRI does not appear to dictate growth direction. A completion method, named here as Short Interval Re-injection (SIR), is investigated with respect to the cohesionless state of the created fracture network, comprised of natural fractures (DFN) and the HF plane. The computer modelling code 3DEC was used to create a geomechanical model with observed MS events used as the calibration metric. The increase in MS event count seen in literature was replicated in the observed and modelled MS but it was discerned that the technique did not increase fracture complexity, as few new fractures were created during the re-injection. It is instead suggested that the SIR technique reinforces previously created fractures to improve stage production.