Unconventional Field Research Articles

Normal faulting activated by hydraulic fracturing: A case study from the Barnett Shale, Fort Worth Basin

Surface microseismic arrays enable long-term field-scale monitoring over multiple stimulations during the life of an unconventional field. In this study, we show highly economic methods of monitoring with sparse surface arrays in the Barnett Shale and develop an alternatative method of processing to enable good vertical and horizontal resolution of located events. We show that sparse surface monitoring arrays enable not only the detection and location of high numbers of microseismic events but also source mechanism characterization. This case study illustrates how hydraulic fracturing activated normal faulting at a distance of approximately 1 mile from stimulated wells. We show that the source mechanism enables us to resolve between newly created hydraulic fractures and activated faults. The differences in source mechanisms and b-values of newly created fractures and activated faults are consistent with independently processed temporary star-like arrays, which are also deployed over the same stimulation.

A methodology for integrating unconventional geologic and engineering data into a geocellular model

Unconventional field development and well performance analysis encompass multiple disciplines and large data sets. Even when seismic and other data sets are not available, geologists can build geocellular models to determine factors that improve operational efficiency by incorporating well log, geosteering, stratigraphic, structural, completion, and production data. I have developed a methodology to integrate these data sets from vertical and horizontal wells to build a sequence stratigraphic and structurally framed geocellular model for an unconventional Marcellus Formation field in the Appalachian Basin, USA. The model would benefit from additional data sets to perform a rigorous investigation of performance drivers. However, the presented methodology emphasizes the value of constructing geocellular models for fields with sparse data by building a geologically detailed model in a field area without seismic and core data. I used third-order stratigraphic sequences interpreted from vertical wells and geosteering data to define model layers and then incorporate completion treating pressures and proppant delivered per stage into the model. These data were upscaled and geostatistically distributed throughout the model to visualize completion trends. Based on these results, I conclude that geologic structure and treating pressures coincide, as treating pressures increase with stage proximity to a left-lateral strike-slip fault, and completion trends vary among third-order systems tracts. Mapped completion issues are further emphasized by areas with higher model proppant values, and all treating pressure and proppant realizations for each systems tract have the greatest variance away from data points. Similar models can be built to further understand any global unconventional play, even when data are sparse, and, by doing so, geologists and engineers can (1) predict completion trends based on geology, (2) optimize efficiency in the planning and operational phases of field development, and (3) foster supportive relationships within integrated subsurface teams.

E&P Notes (November 2019)

E&P Notes Majors Step Up Low-Carbon Initiatives The Oil and Gas Carbon Initiative (OGCI), the CEO-led enterprise formed to drive the industry response to climate change, has launched a new effort to unlock large-scale investment in carbon capture, use, and storage (CCUS) as a crucial tool to help achieve net zero emissions. The CCUS initiative is designed to help decarbonize multiple industrial hubs around the world. The goal of the initiative, according to OGCI, is to double the amount of CO2 that is currently being stored globally before 2030 while building a pipeline of potential future hubs to bring the fledgling CCUS industry to scale. To achieve this goal, OGCI says it will start by building on the work of many others to jointly put five emerging hubs into operation in the US, the UK, Norway, The Netherlands, and China. In parallel, OGCI announced it has launched a joint CCUS Acceleration Framework with the 11 countries supporting the Clean Energy Ministerial CCUS Initiative, a high-level global forum working to create a global, commercial CCUS industry at the scale needed to meet the Paris Climate Agreement goals. BP Appraisal Well Proves “World-scale Gas Resource” Offshore Senegal The BP-operated Yakaar-2 appraisal well off Senegal encountered 30 m of net gas pay in a similar high-quality Cenomanian reservoir as the Yakaar-1 discovery well drilled in 2017, partner Kosmos Energy said 23 September. Yakaar-2 was drilled 9 km from Yakaar-1 and proved up the southern extension of the field. Kosmos said the results underpin its view that the Yakaar-Teranga resource base is “world-scale” and could support an LNG project to supply domestic and export gas markets. The previous Yakaar and Teranga discoveries on the Cayar Offshore Profond block confirmed that a prolific inboard gas fairway extends 200 km from Mauritania through the Greater Tortue area on the maritime boundary of Senegal and Mauritania, according to Kosmos’ website. The Teranga-1 discovery well was drilled in 2016. Development of Yakaar-Teranga is expected in a phased approach with Phase 1 providing domestic gas and data to optimize the development of future phases. Chevron, Schlumberger, Microsoft Team To Improve Digital, Petrotechnical Work Flows Chevron, Schlumberger, and Microsoft will combine their capabilities to create better digital, cloud-enabled work flows. The companies will build for Chevron applications in Schlumberger’s DELFI cognitive exploration and production (E&P) environment that will be native to Microsoft’s Azure cloud computing platform. DELFI is a scalable and open cloud-based environment providing E&P software technology across the exploration, development, production, and midstream segments. The combination of digital technologies will enable Chevron—and, eventually, other companies—to process, visualize, interpret, and glean insights from multiple data sources, the companies said. Summer of Funding: These Oil and Gas Startups Raised More Than $70 Million The oil and gas industry’s appetite for emerging innovations grew by at least $70 million over the past few months as investment arms of several large producers and upstream venture firms completed funding rounds for startups. The influx of cash into young firms is considered a major component of the upstream industry’s drive toward digital transformation. The companies attracting investor attention tilt toward the North American shale sector, which has been turning to new technologies to unravel the complexities of tight reservoir development. Others apply more broadly to unconventional and conventional field development. Study of DUCs Concludes Better Later than Never Delaying a completion by as many as 4 years has “little effect” on the initial production level, according to a new study by US Energy Information Administration (EIA). The study tested the assumption that long-delayed completions mean a well is not worth the cost. “Some people say you cannot fracture a well drilled more than a year ago,” but the data says otherwise, said Jozef Lieskovsky, a senior analyst for the EIA who coauthored the report. The study looked at Bakken wells dating back to 2014, when the oil price crash caused a surge in drilled but uncompleted wells (DUCs) as companies slashed spending. What the EIA found was that the average initial production for the oldest wells (3–4 years old) peaked at a slightly higher level that the youngest ones (1–2 years old).

Optimization Work Flow Maximizes Value of Unconventional Fields

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE-191779-18ERM-MS, “A Fast-Paced Work Flow for Well Spacing and Completions Design Optimization in Unconventional Reservoirs,” by Hoss Belyadi, SPE, and Malcolm Smith, EQT Corporation, prepared for the 2018 SPE Eastern Regional Meeting, Pittsburgh, Pennsylvania, USA, 7–11 October. The paper has not been peer reviewed. Well spacing optimization is one of the more important considerations in unconventional field development. The essence of field development and optimization is to use completions design and well spacing to optimize the net present value (NPV) of the field on the basis of current commodity pricing, capital expenditure (CAPEX), operating cost, cycle time, and net revenue interest. A substantial variation in any of these essential factors must be studied to make sure the appropriate changes are accounted for in field development and optimization. A fast-paced and dynamic work flow has been developed that can be applied in different shale reservoirs to maximize the NPV of these assets. This paper describes the work flow, starting with a fracture model, then coupled with a production model using numerical simulation to obtain a calibrated model, and, finally, a detailed economic and sensitivity analysis to obtain the well spacing and completions design that will yield the highest NPV of the field. Introduction When well spacing systems (interlateral spacing) for various unconventional basins were developed, commodity pricing was much higher and completions job sizes were smaller than they are today. The majority of wells were completed with less than 1,300 lbm/ft of proppant. As operators increased job sizes and seized the benefit of higher production performance, discussions regarding increasing well spacing also took place. After 2014, operators sought ways to stay economical at lower commodity pricing and began to consider feasible ways to reduce operational costs, improve well productivity, raise NPV/acre, automate processes and work flows, use machine learning (ML) to improve predictability, and optimize workforce efficiency. Optimal well spacing for any unconventional well depends on many factors, including gas price, capital and operating expense, acreage position and inventory, completions design, production performance, and lateral length. There is no one-size-fits-all well spacing for various completions designs. Performing a full analysis, therefore, is crucial to finding the optimal well spacing for each area, either analytically or numerically. Factors such as geology, engineering, and economic analysis must be considered. For instance, optimal well spacing and completions design for a geologically noisy and complex reservoir will be invalid in a discreet and quiet area. Similarly, if well spacing and completions design were developed for a high-commodity-pricing environment, performing the same work flow and evaluation at lower commodity pricing would yield an increase in well spacing. The work flow described in the complete paper addresses all these factors and uses modeling, numerical simulation, ML, and linear programming to optimize NPV.

Development and Application of a Coupling Method for Well Pattern and Production Optimization in Unconventional Reservoirs

Numerous optimization variables cause the optimization of large-scale field development challenging, which can be overcome by constraining wells to be within patterns and optimizing the parameters relevant to the pattern type and geometry. In this study, a new method incorporating well pattern optimization and production optimization for unconventional reservoirs is presented. By defining a quantitative well pattern description approach, we develop the geometric transformation parameters to quantify well pattern operations (e.g., rotation, shear, especially translation) to change the geometric shape of well patterns including five-spot, inverse seven-spot and inverse nine-spot well pattern. In contrast, a variety of optimization algorithms can be applied to accomplish the optimization of well pattern problems but the computational cost is large for many algorithms. Therefore, we also propose a general upscaling stochastic approximation algorithm (GUSA), which is an improved approximate perturbation gradient algorithm, to realize the combination of well pattern optimization and production optimization simultaneously. It is proved that both the gradient formulation of SPSA algorithm and EnOpt algorithm are the special form of the general approximate perturbation gradient. Afterwards, the synthetic cases (homogeneous and heterogeneous models) and actual unconventional field cases are discussed based on the three mentioned well pattern types. The detailed optimization results show that the presented coupling method can achieve the optimization by transforming well pattern geometry, reducing the total number of wells and adjusting the field injection rate, which is proved to be effective. In sum, this coupling method provides an efficient optimization procedure combing the well pattern optimization and production optimization for practical field development.

Evaluating the Efficiency of Gravimeter Vibration Protection during Aerogravimetric Surveys

Aerogravimetric survey is a rapidly developing and promising method for studying the gravity field in remote regions of the Earth. However, its practical use involves difficulties. Thus, during flights, inertial interference occurs due to engine-induced vibration of the fuselage. Earlier, various options for antivibration designs were tested. During its annual aerogravimetric works, the Schmidt Institute of Physics of the Earth, Russian Academy of Sciences (IPE RAS), employs a quite efficient option, which, however, cannot be regarded as complete. For the first time, a high-frequency seismometer was used to evaluate the efficiency of a gravimeter antivibration system used in aerogravimetric operations. Vibration suppression was assessed in a wide frequency range. During experimental flights, a decrease in vibration noise was detected at a frequency of 2 Hz, which is relevant for gravimetric equipment. The experimental results confirm the adequacy of the applied antivibration equipment. The antivibration platform developed at IPE RAS significantly reduces vibrations affecting the GT-2M aerogravimetric system. The possibility of using the Baikal-ACN high-frequency seismometer in an unconventional field of application is demonstrated.

Unconventional Magnetization below 25\u2009K in Nitrogen-doped Diamond provides hints for the existence of Superconductivity and Superparamagnetism

The magnetization of nitrogen-doped single crystalline diamond bulk samples shows unconventional field and temperature hysteresis loops at T {boldsymbol{lesssim }} 25 K. The results suggest the existence of superparamagnetic and superconducting regions in samples with nitrogen concentration <200 ppm. Both phases vanish at temperatures above 25 K where the samples show diamagnetic behavior similar to undoped diamond. The observation of superparamagnetism and superconductivity is attributed to the nitrogen doping and to the existence of defective regions. From particle-induced X-ray emission with ppm resolution we rule out that the main observations below 25 K are due to magnetic impurities. We investigated also the magnetic properties of ferromagnetic/high-temperature superconducting oxide bilayers. The magnetization results obtained from those bilayers show remarkable similarities to the ones in nitrogen-doped diamond.

Estimation of uncertainty in reservoir simulations results and its application to an unconventional natural gas field

Estimation of uncertainty in reservoir simulations results and its application to an unconventional natural gas field

An optimised Hydraulic Fracturing Treatment on Challenging Rizq Field

Hydrocarbon production from unconventional reservoirs is often associated with hydraulic fracturing operations. In many cases however, the high in-situ stresses and complex natural fracture network hinder an effective stimulation process. Therefore, different strategies are adopted to increase the success chance of stimulation. These strategies are in many cases field dependent and thus cannot be extended to other fields. In this study, we demonstrate a new work flow to ensure a successful stimulation process in an unconventional gas field in Pakistan. Well Rizq-01 was drilled as an exploration into challenging PAB formation which is tight sandstone with 0.3mD permeability but highly fractured. Exploration wells in offset fields were drilled and stimulated in the same formation and resulted in screening-out and inability to place enough proppant due to fracture complexity and high in-situ-stresses. To overcome these challenges, extensive petrophysical and geomechanical analysis were performed to introduce a new workflow for stimulation of the formations with similar characteristics. The workflow includes a) Extract extensivewell log information for better understanding of stress barriers, stress magnitude and orientation, Young’s Modulus, formation fluid information, other essential petrophysical properties, b) Sensitivity analysis on the hydraulic fracturing treatment including the proppant size, type and volume, and fluid systeme.g. the design was based upon geomechanical and petrophysical interpretations of the openhole log data, and c) Redesign of fracturing treatment process utilizing a first-of-its-kind onsite pre-frac test results, showing its helpfulness in the absence of bottom-hole gauge. The study therefore summarizes the challenges, the work flow implemented, and the lesson learnt for successful stimulation job in Rizq Field.

Unconventional field induced phases in a quantum magnet formed by free radical tetramers

We report experimental and theoretical studies on the magnetic and thermodynamic properties of NIT-2Py, a free radical-based organic magnet. From magnetization and specific heat measurements we establish the temperature versus magnetic field phase diagram which includes two Bose-Einstein condensates (BEC) and an infrequent half magnetization plateau. Calculations based on density functional theory demonstrates that magnetically this system can be mapped to a quasi-two-dimensional structure of weakly coupled tetramers. Density matrix renormalization group calculations show the unusual characteristics of the BECs where the spins forming the low-field condensate are different than those participating in the high-field one.

Selection of decline curve analysis method using the cumulative production incline rate for transient production data obtained from a multi-stage hydraulic fractured horizontal well in unconventional gas fields

This research presents the selection of an appropriate decline curve analysis (DCA) methodology according to the transient production performance of a multi-fractured horizontal well in an unconventional gas field by using the cumulative production incline rate (IQp) The IQp introduced in this research is the change of cumulative production per unit time divided by the cumulative production. The IQp was confirmed for use as an indicator that could generalise and quantify a production decline through the analysis of well production data. The IQp values of eight and four DCA methods were applied to the production data generated by a reservoir simulation. The Duong method forecasted the production trends most accurately when the IQp exceeded 0.25%, while the YM-SEPD method was the most preferable for the rates below 0.05%. In addition, the analysis of production data for shale gas wells in Canada and the USA matched the simulation results, confirming that it would be reasonable to use the IQp in order to select a DCA method to forecast the production of unconventional gas wells. [Received: February 23, 2017; Revised: December 7, 2017; Accepted: December 9, 2017]

Fatigue assessment of Ti-6Al-4V titanium alloy laser welded joints in absence of filler material by means of full-field techniques

The aim of this research activity was to study the fatigue behavior of laser welded joints of titanium alloy, in which the welding was performed using a laser source and in the absence of filler material, by means of unconventional full field techniques: Digital Image Correlation (DIC), and Infrared Thermography (IRT). The DIC technique allowed evaluating the strain gradients around the welded zone. The IRT technique allowed analyzing the thermal evolution of the welded surface during all the fatigue tests. The fatigue limit estimated using the Thermographic Method corresponds with good approximation to the value obtained from the experimental fatigue tests. The obtained results provided useful information for the development of methods and models to predict the fatigue behavior of welded T-joints in titanium alloy.

An integrated approach to discretized 3D modeling of geomechanical properties for unconventional mature field appraisal in the western Canadian sedimentary basin

In mature field appraisal and development, discretized geomechanical property models play a vital role in providing information on in situ stress regime as a guide for placement of directional wells. Laboratory methods of measuring these properties, in most cases, take only small samples from consolidated rocks. These isolated samples may not be representative of the entire elastic regime existing in the reservoir owing to sample size. In general, geomechanical studies are performed on a well-by-well basis and then these measurements are used as calibration points to convert 3D seismic data (if available) to geomechanical models. However, elastic properties measured this way are restricted to the well location and interpolation across the reservoir may not be always appropriate. To overcome these challenges, this paper describes an integrated approach for deriving 3D geomechanical models of the reservoir by combining results of 3D geocellular models and basin models. The basin model reconstructs the geologic history (i.e., burial history) of the reservoir by back-stripping it to the original depositional thickness. Through this reconstruction, the mechanical compaction, pore pressures, effective stress, and porosity versus depth relationships are established. Next, these mechanical properties are discretized into 3D geocellular grid using empirical formulas via lithofacies model even if no 3D seismic data are available for the reservoir. The discretization of elastic properties into 3D grids results in a better understanding of the prevailing stress regimes and helping in design of hydraulic fracturing operations with minimal risks and costs. This approach provides an innovative way of determining effective horizontal stress for the entire reservoir through 3D distribution of elastic properties.

Hydraulic Fracturing and Production Optimization in Eagle Ford Shale Using Coupled Geomechanics and Fluid Flow Model

With increasing production from shale gas and tight oil reservoirs, horizontal drilling and multistage hydraulic fracturing processes have become a routine procedure in unconventional field development efforts. Natural fractures play a critical role in hydraulic fracture growth, subsequently affecting stimulated reservoir volume and the production efficiency. Moreover, the existing fractures can also contribute to the pressure-dependent fluid leak-off during the operations. Hence, a reliable identification of the discrete fracture network covering the zone of interest prior to the hydraulic fracturing design needs to be incorporated into the hydraulic fracturing and reservoir simulations for realistic representation of the in situ reservoir conditions. In this research study, an integrated 3-D fracture and fluid flow model have been developed using a new approach to simulate the fluid flow and deliver reliable production forecasting in naturally fractured and hydraulically stimulated tight reservoirs. The model was created with three key modules. A complex 3-D discrete fracture network model introduces realistic natural fracture geometry with the associated fractured reservoir characteristics. A hydraulic fracturing model is created utilizing the discrete fracture network for simulation of the hydraulic fracture and flow in the complex discrete fracture network. Finally, a reservoir model with the production grid system is used allowing the user to efficiently perform the fluid flow simulation in tight formations with complex fracture networks. The complex discrete natural fracture model, the integrated discrete fracture model for the hydraulic fracturing, the fluid flow model, and the input dataset have been validated against microseismic fracture mapping and commingled production data obtained from a well pad with three horizontal production wells located in the Eagle Ford oil window in south Texas. Two other fracturing geometries were also evaluated to optimize the cumulative production and for the three wells individually. Significant reduction in the production rate in early production times is anticipated in tight reservoirs regardless of the fracturing techniques implemented. The simulations conducted using the alternating fracturing technique led to more oil production than when zipper fracturing was used for a 20-year production period. Yet, due to the decline experienced, the differences in cumulative production get smaller, and the alternating fracturing is not practically implementable while field application of zipper fracturing technique is more practical and widely used.

O(N) and O(N) and O(N)

Three related analyses of ϕ4 theory with O(N) symmetry are presented. In the first, we review the O(N) model over the p-adic numbers and the discrete renormalization group transformations which can be understood as spin blocking in an ultrametric context. We demonstrate the existence of a Wilson-Fisher fixed point using an ϵ expansion, and we show how to obtain leading order results for the anomalous dimensions of low dimension operators near the fixed point. Along the way, we note an important aspect of ultrametric field theories, which is a non-renormalization theorem for kinetic terms. In the second analysis, we employ large N methods to establish formulas for anomalous dimensions which are valid equally for field theories over the p-adic numbers and field theories on ℝn. Results for anomalous dimensions agree between the first and second analyses when they can be meaningfully compared. In the third analysis, we consider higher derivative versions of the O(N) model on ℝn, the simplest of which has been studied in connection with spatially modulated phases. Our general formula for anomalous dimensions can still be applied. Analogies with two-derivative theories hint at the existence of some interesting unconventional field theories in four real Euclidean dimensions.

Ant colony heuristic for user-contributed comments summarization

User-contributed comments (UCC) are one of the signs of the social media. Due to the high popularity of social media, it becomes already exceedingly difficult to find the most relevant, interactive information for the users. The motivation behind this work is the fact that users may interest to get an efficacious brief understanding of comments without reading the entire comments. This paper opens up an unconventional field of comment's summarization predicated on Ant colony optimization mixed with Jensen–Shannon divergence (ACO-JSD). ACO-JSD is a proposed novel technique concerning the extraction the most interactive comments from the huge amount of concise comment's perspectives. This problem is unfastened utilizing ACO to generate the optimal solution. Moreover, the JSD model is employed to ensure a summary could capture the essence of the original comments. First, an acyclic semi-graph has been constructed under two constraints: (1) the longest comments will be isolated from the graph, (2) The more similarity between two comments, the greater the chance that mutual connectivity is eliminated. Next, a feasible solution is constructed to select the high-quality summarization. Finally, the proposed algorithm has been evaluated over a collection of Facebook posts with their associated comments and an excellent performance in comparison with traditional document summarization algorithms was obtained. Accordingly, the computational results show the efficiency of the proposed algorithm, as well as its ability to find a good summary that is guaranteed to be near-optimal.

Quantitative estimation of permeability enhancement, production and depletion from microseismic data

It is a known fact that cost efficiency is the number one priority across the industry, perhaps even more so in today’s price environment. Operators are seeking technologies to improve profitability for unconventional field development. Getting a reliable estimate of production within days of completing an unconventional well is every operator’s dream. Armed with this knowledge operators would be able to evaluate the effectiveness of treatment and well spacing strategies without having to wait for months of actual production, allowing for them to arrive at an optimum development plan in a more timely fashion. In this article we demonstrate that microseismic monitoring, taken as an insitu, real time field observation of the completion of a well that integrates all the effects of rock properties, tectonic stresses and treatment parameters enables an estimate of well productivity within reasonable limits. In this method, microseismic data is used to describe a deterministic discrete fracture network model, differentiating between propped and un-propped fractures and further defining a fracture intensity in a given rock volume. This fracture intensity is translated into a measure of permeability enhancement, both magnitude and distribution, achieved through the process of hydraulic fracturing. Through reservoir simulation using this more complete model it is possible to estimate each well’s current and future productivity and the reservoir pressure depletion as a function of time. Current practices rely on unrealistic planar fracture models leading to to inaccurate predictions of unconventional wells’ production and drainage patterns. The approach presented here explicitly honours the microseismic measurements and provides a realistic representation of the induced fracture geometry and thus improved production and drainage estimates. These early production predictions are available within a few days after a well’s treatment, eliminating the typical 6-to-12-month waiting time for production results. The ability to create a model that is consistent with actual production, as shown in the case histories presented here, suggests that uncertainty is sufficiently constrained through the workflow outlined in this article.

Scoring completion effectiveness in unconventional horizontal wells using 3D seismic attributes

Using a multihorizontal well-completion pilot in an unconventional oil field in the Lower 48 (contiguous United States) Midcontinent, a workflow is proposed to evaluate the effectiveness of horizontal-well completions through 3D surface-seismic attributes and microseismic data. Three-dimensional surface seismic is often continuous over unconventional fields and provides a measurement in areas where no other data are available. In addition, microseismic is the only geophysical data that allows us to “see” the apparent hydraulic-fracture zone around a wellbore. Using these two geophysical tools integrated with engineering and geologic data such as image logs, total proppant, number of stages, estimates of fracture length and height, permeability, chemical tracers, and production rates, a “geophysical completion scorecard” is developed to evaluate a multiwell horizontal pilot and apply it to additional wells drilled outside the pilot in an effort to predict their completion effectiveness. A postdrill review of production rates in those wells shows good correlation to the scorecard's predictions of completion effectiveness.

ChemInform Abstract: Carbon‐Centered Radical Addition to C=X Bonds for C—X Bond Formation

AbstractReview: [56 refs.

Ambient Seismic Imaging Throughout the Unconventional Field’s Life Cycle

Technology Update Newly developed ambient seismic imaging methods provide valuable information throughout the life cycle of an unconventional field. Methods developed by Global Geophysical Services enable new insights for exploration, development planning, fracture and refracture design, reservoir management, production forecasting, and reserves estimation. Ambient seismic imaging has also been used to monitor conventional reservoirs, waterfloods, CO2 sequestration, mine stability, and water influx into mines. Additional applications include geothermal systems and induced seismicity monitoring. Many assume that the term “ambient seismic” (imaging artificial or natural seismic emissions) is synonymous with “microseismic” (imaging earthquakes with a magnitude less than 0, i.e., microearthquakes or MEQs). However, advances in the understanding of natural and induced seismic emissions and new imaging and analytical methods have differentiated these terms. Microseismic methods typically locate MEQs by use of classical seismological methods: polarization angles and arrival times of P and S waves. Thus, the term “microseismic” implies methods relying only on MEQs, the “dots-in-a-box” long familiar to fracturing engineers and development geologists. In recent years, research has shown that the majority of the seismic energy radiated during a fracture treatment is in seismic phenomena other than MEQs. Other emission sources include longperiod, long-duration (LPLD) activity (Das and Zoback 2013a and 2013b), long-duration signals (LDS) (Sicking et al. 2014), and fluid resonance in the fracture system (Tary and van der Baan 2012). These types of emissions cannot be analyzed with classical methods because they do not have distinct, noticeable first arrivals or recognizable P/S wave separation. Such emissions can persist or fade in and out for minutes to hours, rather than milliseconds, and therefore cannot be classified as distinct events such as MEQs. Furthermore, there may be other seismic phenomena that have yet to be identified and categorized. Seismic emission tomography (SET) is an alternative to locating earthquakes with P and S wave arrivals and polarization angles. It is in wide use for surface monitoring and most recently for downhole monitoring. SET focuses total trace energy by means of ray tracing through the velocity model in short time steps (on the order of 100 ms), thus imaging energy from many types of seismic emissions, including MEQs, LPLD, LDS, fluid resonance, and possibly unknown phenomena. Each computed SET time step produces a voxel-by-voxel depth image of seismic emissions in the same way that a 3D surface reflection seismic survey produces a 3D time image. MEQs located in individual time steps are termed “proxy hypocenters” because they represent brief, high-energy events. However, they are not identified uniquely as MEQs by classical methods.