Seismic Monitoring Technology Research Articles

Geophysical Monitoring Technologies for the Entire Life Cycle of CO2 Geological Sequestration

Geophysical monitoring of CO2 geological sequestration represents a critical technology for ensuring the long-term safe storage of CO2 while verifying its characteristics and dynamic changes. Currently, the primary geophysical monitoring methods employed in CO2 geological sequestration include seismic, fiber optic, and logging technologies. Among these methods, seismic monitoring techniques encompass high-resolution P-Cable three-dimensional seismic systems, delayed vertical seismic profiling technology, and four-dimensional distributed acoustic sensing (DAS). These methods are utilized to monitor interlayer strain induced by CO2 injection, thereby indirectly determining the injection volume, distribution range, and potential diffusion pathways of the CO2 plume. In contrast, fiber optic monitoring primarily involves distributed fiber optic sensing (DFOS), which can be further classified into distributed acoustic sensing (DAS) and distributed temperature sensing (DTS). This technology serves to complement seismic monitoring in observing interlayer strain resulting from CO2 injection. The logging techniques utilized for monitoring CO2 geological sequestration include neutron logging methods, such as thermal neutron imaging and pulsed neutron gamma-ray spectroscopy, which are primarily employed to assess the sequestration volume and state of CO2 plumes within a reservoir. Seismic monitoring technology provides a broader monitoring scale (ranging from dozens of meters to kilometers), while logging techniques operate at centimeter to meter scales; however, their results can be significantly affected by the heterogeneity of a reservoir.

Time-lapse difference seismic inversion based on scattering theory

Time-lapse seismic monitoring technology is an effective tool for quantitatively estimating subsurface medium variations and plays a crucial role in resource and engineering explorations. Among existing time-lapse inversion methods, the difference inversion technique offers higher accuracy but requires linear inversion operators. During linearization, the background is often approximated as a homogeneous medium, resulting in the loss of effective information. Additionally, merely using reflection wave information is not conducive to improving inversion accuracy. However, the true structure of the subsurface is often complex and inhomogeneous, which can easily generate complex wavefields, such as scattering waves, thereby hindering the resolution of differences between time-lapse models. Therefore, incorporating more comprehensive wavefield information is essential for enhancing the accuracy of time-lapse seismic inversion. To address this issue, a wave-equation-based time-lapse difference inversion method is proposed to retrieve the production-induced property perturbation. In the proposed method, the forward operator is formulated through the scattering wave equation, the operator is linearized through the Born approximation, and the WKBJ method is used to approximate Green's function with high accuracy for the inhomogeneous background. In this study, time-lapse seismic parallel inversion and difference inversion are conducted using the proposed forward operator. Both numerical experiments and application of field seismic data indicate that the proposed time-lapse difference inversion method can realize a more accurate quantitative characterization of time-lapse variations.

Revealing complex subsurface dynamics with continuous seismic monitoring: Observations using distributed acoustic sensing and surface orbital vibrators during hydraulic fracturing

Understanding hydraulic fracturing is crucial to improving the stimulation of unconventional reservoirs and increasing fluid production. This study develops a novel seismic monitoring technology using distributed acoustic sensing (DAS) and surface orbital vibrators (SOV) to capture fracture seismic response and mechanical properties at high temporal intervals. We analyze continuous time-lapse vertical seismic profiling (VSP) data acquired every hour during the first nine days of treatment of an unconventional reservoir in the Austin Chalk/Eagle Field Laboratory. The VSP data contain clear seismic signals scattered from the activated fractures. The spatiotemporal changes of the fracture reflectivity revealed by the SOV/DAS data correlate well with the observations of fracture locations inferred from low-frequency DAS data. These results capture the fracture opening and closure processes, as well as highlight potential prestage activations of the fractures due to hydraulic connectivity with preexisting fracture systems. Therefore, analysis of the presented data set provides a unique opportunity to understand fracture initiation and subsequent evolution, not only in the context of unconventional resources but also in enhanced geothermal systems.

Performance assessment of an iterative ensemble smoother with local analysis to assimilate big 4D seismic datasets applied to a complex pre-salt-like benchmark case

Abstract The use of 4D seismic (4DS) (or time-lapse seismic, TLS) in data assimilation (DA) makes the process more complex due to the higher amount of data to be assimilated, requiring more robust methods and better computational resources (processing capacity and memory). The development and application of permanent seismic monitoring technologies have increased in recent years, improving the overall 4D seismic quality in terms of signal resolution and repeatability. However, a massive amount of data is generated from the multiple monitors, making the incorporation of 4DS data in the DA process more complex. Therefore, robust DA methods capable of dealing with huge amount of data effectively and efficiently are essential. This paper aims to assess the performance of an iterative ensemble smoother method, named subspace ensemble randomized maximum likelihood with a local analysis, to assimilate a big dataset. The method was applied in a challenging pre-salt-like benchmark case with eight seismic surveys, one base, and seven monitors. The 4DS data are the impedance ratios (between two consecutive monitors) in 15 seismic horizons, totaling 105 maps to be assimilated. To our best knowledge, this is state of the art in terms of practical applications in DA. It was possible to assimilate all the data simultaneously: the 105 horizons for the 4DS data and the wells’ production and pressure data. The DA was successful in terms of results quality and method performance. We also ran a case assimilating only well data for comparison purposes.

Blind Curvelet-Based Denoising of Seismic Surveys in Coherent and Incoherent Noise Environments

Distributed acoustic sensing (DAS) is a new seismic monitoring technology. DAS generates a large amount of data, necessitating the development of new technologies to allow for cost-effective processing and handling. The raw seismic data is noisy and must be processed. The curvelet transform is an excellent choice for processing seismic data due to its localized nature, as well as its frequency and dip characteristics. However, its capabilities are limited in case of noise other than white. This paper proposes a denoising method based on a combination of the curvelet transform and a whitening filter, as well as a procedure for estimating noise variance. The whitening filter is included to improve the performance of the curvelet transform in both coherent and incoherent noise cases, as well as to simplify the noise variance estimation method and make it easier to use standard threshold methodology without delving into the curvelet domain. Two data sets are used to validate the suggested technique. Pseudo-synthetic data set created by adding noise to the actual noise-free data collection from the Netherlands offshore F3 block and the on-site data set (with ground roll noise) from east Texas, USA. Experimental results demonstrate that the proposed algorithm achieves the best results under various types of noise.

Advanced time-lapse processing of continuous DAS VSP data for plume evolution monitoring: Stage 3 of the CO2CRC Otway project case study

Active time-lapse seismic monitoring technology is essential for carbon storage projects due to its ability to track the CO2 plume in space and time. A particularly attractive implementation of this technology is permanent seismic reservoir monitoring (PRM) using permanent sources and receivers, which can track subsurface changes in near-real-time over decades. As the number of source points in such a setup is likely to be limited, repeatability and signal to noise ratio need to be improved by processing all the multiple vintages together rather than separately.We explore the advantages of this approach using a PRM dataset acquired to monitor injection of 15 kt of CO2 into a saline aquifer at the Otway International Test Centre (Australia). The monitoring employs continuous acquisition of multi-well offset VSP using nine permanent sources (surface orbital vibrators) and fibre-optic distributed acoustic sensors installed in five monitoring wells producing a vintage every two days for eighteen months before, during and after the injection.Since data reveals seasonal repeatability variations, mainly created by seasonal variations in precipitation levels, for each monitor, an optimal baseline is the one acquired in the same season. The signal-to-noise ratio is further improved by wavefield decomposition of P and S waves. The consistency of the source signature is improved using Wiener filtering. These algorithms improve the data repeatability from about 15–20% to 10–15% normalised root mean square. The results show the CO2 plume signal on the second day of the injection and subsequent time-lapse changes of a stable CO2 plume created at the same reservoir 650 m up-dip five years earlier as a part of the previous field experiment (Stage 2C) at the site.

Soil State Testing Using Heavy Vehicle Vibrations

Changes in the elastic characteristics of the railway subgrade have been determined using nonstop long-term (more than 50 days) train passage seismic observations. We examined the records of the broadband sensitive seismometer TC-120s in the low-frequency band (below 0.1 Hz) to obtain the subgrade response to various train passages and its relaxation after unloading. Analytical models of subgrade deformation by the train are proposed. When comparing models in the experiment, we showed that a lowpass filter (below 0.1 Hz) provides waveforms with parameters determined by the deformation properties of the soil. We carried out statistical processing of 1600 train seismic records and determined parameters characterizing the subgrade reaction to the vibration effects created by trains in the ultra-low-frequency range. Therefore, we can use these parameters to monitor after daily averaging and weekly smoothing. When observing the spring thawing of the soil, we considered the sensitivity of seismic monitoring using heavy vehicle vibrations, particularly changes in the soil state properties under a rise in ambient temperature. The presented observations can be used for seismic monitoring technology at an early stage of hazardous processes in the subgrade.

SUCCEED: A CO2 storage and utilisation project aimed at mitigating against greenhouse gas emissions from geothermal power production

The non-condensable gases in most geothermal resources include CO2 and smaller amounts of other gases. Currently, the worldwide geothermal power is a small sector within the energy industry, and CO2 emissions related to the utilisation of geothermal resources are consequently small. In some countries, however, geothermal energy production contributes significantly to their energy budget and their CO2 emissions are relatively significant. SUCCEED is a targeted innovation and research project which aims to investigate the reinjection of CO2 produced at geothermal power production sites and develop, test and demonstrate at field scale innovative measurement, monitoring and verification (MMV) technologies that can be used in most CO2 geological storage projects. The project is carried out at two operating geothermal energy production sites, the Kizildere geothermal field in Turkey and the CarbFix project site at the Hellisheiði geothermal field. Together with a brief description of the seismic monitoring technologies proposed in the project, this paper presents the details of the two field sites and the progress made in installing and testing of the surface fibre-optic cables at the Hellisheiði geothermal field in Iceland.

Pluto gas field: Successful placement of an infill well based on 4D seismic monitoring

Seismic 4D monitoring technology has not been as widely employed for gas fields as it has for oil. Many gas fields rely on depletion drive, which has a 4D seismic response that can be uncertain and difficult to predict. On the other hand, aquifer-supported gas fields with measurable water ingress have a reasonable chance of success in terms of generating an interpretable 4D amplitude signal. Pluto gas field in the North West Shelf of Australia falls into this category. Following discovery in 2005, Pluto was appraised by five wells, which found a consistent gas gradient and gas-water contact across the entire field and its various reservoirs. Gas production began in 2012. Time-lapse seismic feasibility studies concluded that gas-saturation changes could be observed with a monitor seismic survey acquired three to four years after first gas. The Pluto 4D Monitor 1 survey was acquired at the start of 2016 and revealed both hardening and softening anomalies. Hardening is interpreted as water ingress (expected) and softening as gas expansion (unexpected). The Pluto 4D results provided important insights into reservoir connectivity and discontinuities. Large hardening anomalies at the TR27 (lower) level can be clearly seen in the data, showing avenues for water ingress. More importantly, a large softening anomaly below the original gas-water contact in the TR29 (upper) reservoir is interpreted to be gas expansion into the aquifer created by a U-tubing effect around a possible barrier in the gas leg. This suggests that the entire TR29 reservoir may not be accessed by the producing PLA04 well. Based on this 4D interpretation, the PLA07 well was drilled and completed in 2019 to produce the TR29 gas updip from the gas expansion anomaly and to increase Pluto field recovery.

Research on evaluation technology of gas anomaly zone in Xiadian Mine based on 3D seismic monitoring technology

ABSTRACT Based on the analysis of the theory of seismic exploration, this paper evaluates the quality of three-dimensional (3D) seismic data, analyzes the reflection characteristics of coal seam, and forecasts the thickness of coal seam qualitatively and quantitatively by using seismic attribute and wave group anti inversion method, and obtains the thickness plan of minable coal seam in Xiadian mine. According to the coal seam gas content and gas relative emission, it is predicted that the upper limit of gas relative emission in the mine will change from 1.38 to 20.30 m3/t·d, which is a low biogas mine area with high biogas area in some parts, and the destruction factors of No. 21 coal seam and No. 43 coal seam are abnormal in some parts, which are structural coal. The development of No. 21 coal seam is stable, with the thickness variation range of 0.5 ~ 12.5 m and the average thickness of about 4.3 m. The thickness of No. 43 coal seam is lower than that of No. 21 coal seam. The inversion thickness variation range is 0 ~ 4 m and the average thickness is about 2.5 m. The overall thickness of NO. 43 coal seam has little change. The gas anomaly area of No. 21 coal seam is mainly distributed in the form of dots, the lowest line of monoclinic structure and the monoclinic half slope are mainly distributed in two distribution belts in the form of dots, while the gas anomaly area of No. 43 coal seam is scattered with small area.

Monitoring of coal-mine goaf based on 4D seismic technology

The range of coal-mine underground goaf has continuously expanded over time. Caving, fracture, and deformation zones have also changed, thereby inducing coal-mine water inrush and other environmental disasters. In this study, 4D seismic monitoring technology that is effective in reservoir development was used to monitor abnormal changes in coal-mine underground goaf to explore the feasibility of the method. Taking a coal mine in Hancheng, Shaanxi as an example, we used the aforementioned technology to dynamically monitor the abnormal changes in the goaf. Based on the 4D seismic data obtained in the experiment and the abnormal change characteristics of the coal-mine goaf, the method of 4D seismic data processing in reservoir was improved. A set of 4D data processing flow for the goaf was established, and the anomalies in the surface elevation and overlying strata velocity caused by collapse were corrected. We have made the following improvements to the method of 4D seismic data processing in the reservoir: (1) the static correction problem caused by the changes of surface elevation and destruction of the low-velocity layer has been solved through fusion static correction to comb the low-frequency components of elevation statics with the high-frequency components of refraction statics; (2) the problem of overlying strata velocity changes in the goaf caused by collapse has been solved through the velocity consistency method; (3) the problem of reflection event pull-down in the disturbance area has been solved through space-varying moveout correction based on cross-correlation; and (4) amplitude anomalies in the coal seam caused by the goaf have been addressed using the correction method of space-varying amplitude. Results show that the 4D seismic data processing and interpretation method established in this study is reasonable and effective.

Advanced seismic monitoring technologies for coal and ore mines

Advanced seismic monitoring technologies for coal and ore mines

High-resolution 3D marine seismic acquisition in the overburden at the Tomakomai CO2 storage project, offshore Hokkaido, Japan

Monitoring injected CO2 is an important part of assuring permanence of long term storage to mitigate atmospheric emissions. Three-dimensional (3D) seismic has been shown to be an effective technology for visualizing and quantifying subsurface geology and fluids. In this study, we demonstrate the successful acquisition, processing, and initial interpretation of a first-of-its-kind high-resolution 3D (HR3D) marine seismic survey above an active CO2 injection site offshore Tomakomai, Japan. An initial sensitivity study indicated generally favorable subsurface conditions for imaging subsurface pore fluid changes. A unique processing workflow incorporating multiple data processing software packages has been tailored to the short-offset and low-fold HR3D acquisition. The final 3D volume shows generally flat and laterally-continuous stratigraphy in the overburden above the injection zone without identifiable faults, indicating coherent overburden above the CO2 injection site and low associated risk of vertical CO2 migration. The successful deployment of this novel marine seismic monitoring technology in the overburden at a small-scale (100 kt/yr) demonstration project suggests HR3D will also be a useful characterization and monitoring tool for larger demonstration and commercial-scale (˜10 MT) offshore Carbon Capture and Storage (CCS) sites.

Time Lapsed AVAZ Seismic Modeling Research on CO2 Storage Monitoring

CCUS (Carbon Capture, Utilization and Storage) now is a lead way to reduce greenhouse effect such as carbon dioxide emission in the world. This paper presents an integrated overview of seismic monitoring technology when CO2 injection process. Mainly is time-lapse seismic method .Time-lapse seismic method is a feasible way to monitor CO2 injection process when CO2 interaction with minerals, which is proved an effective method in CCUS experiments. AVAZ (Amplitude versus Azimuth) seismic method is proved a useful tool to indentify CO2 injection process, which can detect fluid-induced seismic anisotropic response and locating where CO2 flow to in reservoirs, therefore, it’s an effective way to monitor CO2 flow in CO2 monitoring process. Since we develop AVAZ modelling experiment base on rock physics theory to modeling the time-lapse AVAZ seismic reservoir response. The research show fluid saturation and pressure behave two main factors influence modeling seismic AVAZ response. Meanwhile the AVAZ response can also be detect by seismic AVAZ data.

Fiber laser sensors for micro seismic monitoring

Micro seismic monitoring technologies based on fiber laser sensors were introduced. Owing to the characteristics of narrow line width, low noise, fiber laser sensing can achieve high sensitivity and low system noise through some methods, such as enhance-sensitivity packaging, interferometric demodulation technology. With the advantages of small in size, resistant to high temperature and pressure, and easy to be wavelength division multiplexing, it is very fit for micro seismic monitoring. The principles of fiber laser hydrophone and fiber laser accelerometer were described. Some factual application examples of using these fiber laser sensors for micro seismic monitoring were presented.

Applying real time seismic monitoring technology for slope stability assessment—An Indian opencast coal mine perspective

This paper outlines the results obtained from real time microseismic monitoring of an opencast coal mine in South India. The objective of the study is to investigate the stress changes within the rockmass along the slope due to underground mine development operation and their impact on the stability of the highwall slope. The installed microseismic systems recorded the seismic triggerings down to −2 moment magnitude. In general, most of the events recorded during the monitoring period are weak in seismic energy. The study adopts a simple and more reliable tool to characterize the seismically active zone for assessing the stability of the highwall in real time. The impact of underground working on the slope is studied on the basis of the seismic event impact contours and seismic clusters. During the monitoring period, it is observed that the intensity of the overall microseismic activity along the slope due to the mine development operations did not cause any adverse impact on the highwall stability.

CO2 Saturation, Distribution and Seismic Response in Two-Dimensional Permeability Model

Carbon dioxide capture and storage (CCS) has been actively researched as a strategy to mitigate CO(2) emissions into the atmosphere. The three components in CCS are monitoring, verification, and accounting (MVA). Seismic monitoring technologies can meet the requirements of MVA, but they require a quantitative relationships between multiphase saturation distributions and wave propagation elastic properties. One of the main obstacles for quantitative MVA activities arises from the nature of the saturation distribution, typically classified anywhere from homogeneous to patchy. The emerging saturation distribution, in turn, regulates the relationship between compressional velocity and saturation. In this work, we carry out multiphase flow simulations in a 2-D aquifer model with a log-normal absolute permeability distribution and a capillary pressure function parametrized by permeability. The heterogeneity level is tuned by assigning the value of the Dykstra-Parson (DP) coefficient, which sets the variance of the log-normal horizontal permeability distribution in the entire domain. Vertical permeability is a 10th of the horizontal value in each gridcell. We show that despite apparent differences in saturation distribution among different realizations, CO(2) trapping and the V(p)-S(w) Rock Physics relationship are mostly functions of the DP coefficient. When the results are compared with the well accepted limits, Gassmann-Wood (homogeneous) (A Text Book of Sound; G. Bell and Suns LTD: London, 1941) and Gassmann-Hill (patchy) models, the V(p)-S(w) relationship never reaches the upper bound, that is, patchy model curve, even at the highest heterogeneity level in the model.

Behaviour Characteristics of Pressure Bump of Deep Mining in Kailuan Coal Mine and Micro Seismic Monitoring Technology

Pressure bump is a serious disaster to threat coal mine production safety. The roof and floor strata in Kailuan coal mine are made of sandstone and mudstone with relatively poor rigidity. Most of mines have been into the deep mining stage over one thousand meters. High-stress becomes the key factor induced pressure bump. In this paper, according to coal mining strata, fault development, mine inflow and other geological factors, based on fracturing parameters of mine rock and wall rock in the pilot mines (Qianjiaying Mine, Tangshan Coal Mine), boundary conditions of the occurrence of pressure bump is tested by numerical simulation using RFPA software. It discusses the mechanism and laws of pressure bump under high stress in the deep mining. Mining face and roadway are taken real-time monitoring, using micro seismic monitoring system (MMS). The location and level of micro seismic events within the coal formation caused by breakdown could achieve precise position. Spatial distribution and characteristics of coal and rock bursting could be identified. The stability of coal and rock could be monitored real-time and analyzed. Pressure bump could be predicted and prevented effectively.

Time-lapse seismic reservoir monitoring technology in China

Digital surveys of the T block in China's Daqing oil field began in 1988, and the first high-resolution seismic survey in the area was conducted from the winter of 1998 to the spring of 1999. These 2D seismic data sets of 1988 and 1999 have been used in a time-lapse seismic reservoir monitoring study. Figure 1 shows the quality of the seismic data is good, and three events can be clearly seen in the seismic profiles.

Recent advances in seismic monitoring technology at Canadian mines

We provide an overview of the current status of seismic monitoring instrumentation employed in Canadian underground mines. Based on several case studies, we outline how passive seismic monitoring techniques are being used to evaluate fractures and stress conditions associated with ore extraction at depth. It is shown that induced microseismicity allows for the remote monitoring of active fractures, delineating modes of failure with advancing excavation fronts, and identifying variations in principal stress orientations during sequential stages of mining. Advances into the characterization of excavation zone of influence through deformation state analysis and the use of seismic hazard analysis to evaluate the potential for ground instability are also discussed.