3D VSP Research Articles

Automated condylar seating assessment using a deep learning-based three-step approach

ObjectivesIn orthognatic surgery, one of the primary determinants for reliable three-dimensional virtual surgery planning (3D VSP) and an accurate transfer of 3D VSP to the patient in the operation room is the condylar seating. Incorrectly seated condyles would primarily affect the accuracy of maxillary-first bimaxillary osteotomies as the maxillary repositioning is dependent on the positioning of the mandible in the cone-beam computed tomography (CBCT) scan. This study aimed to develop and validate a novel tool by utilizing a deep learning algorithm that automatically evaluates the condylar seating based on CBCT images as a proof of concept.Materials and methodsAs a reference, 60 CBCT scans (120 condyles) were labeled. The automatic assessment of condylar seating included three main parts: segmentation module, ray-casting, and feed-forward neural network (FFNN). The AI-based algorithm was trained and tested using fivefold cross validation. The method’s performance was evaluated by comparing the labeled ground truth with the model predictions on the validation dataset.ResultsThe model achieved an accuracy of 0.80, positive predictive value of 0.61, negative predictive value of 0.9 and F1-score of 0.71. The sensitivity and specificity of the model was 0.86 and 0.78, respectively. The mean AUC over all folds was 0.87.ConclusionThe innovative integration of multi-step segmentation, ray-casting and a FFNN demonstrated to be a viable approach for automating condylar seating assessment and have obtained encouraging results.Clinical relevanceAutomated condylar seating assessment using deep learning may improve orthognathic surgery, preventing errors and enhancing patient outcomes in maxillary-first bimaxillary osteotomies.

Bilateral alloplastic temporomandibular joint reconstruction with orthognathic surgery: a case report of idiopathic condylar resorption

Idiopathic condylar resorption (ICR) also known as cheerleader’s syndrome, progressive condylar resorption, idiopathic condylysis, and condylar atrophy can be defined as chronic ongoing changes of condylar shape and decrease in mass. It is characterized by an excessive physical stress to the articular structures of the temporomandibular joint (TMJ) that exceeds the normal adaptive capacity. Consequently, leading to decrease condylar head volume, decrease ramus height, progressive mandibular retrusion in adults, or decreased growth rate in adolescents. A case report of a 30-year-old female based on the history, clinical, and radiographic examination has class II skeletal relationship secondary to bilateral ICR, receded chin, vertical maxillary excess (VME) and canting. Surgical treatment plan was established using 3D Systems, Inc., (“3DS”) VSP® and case was managed by bilateral total alloplastic temporomandibular joint reconstruction (BATMJR) with orthognathic surgery to do LeFort I, bilateral condylectomy, genioplasty, and inferior border osteotomy. The case report includes one-year follow-up which shows stable outcome, emphasizing long-term success of comprehensive treatment strategy in addressing skeletal class II malocclusion associated with ICR.

Multi-Scale Seismic Measurements for Site Characterization and CO2 Monitoring in an Enhanced Oil Recovery/Carbon Capture, Utilization, and Sequestration Project, Farnsworth Field, Texas

To address the challenges of climate change, significantly more geologic carbon sequestration projects are beginning. The characterization of the subsurface and the migration of the plume of supercritical carbon dioxide are two elements of carbon sequestration that can be addressed through the use of the available seismic methods in the oil and gas industry. In an enhanced oil recovery site in Farnsworth, TX, we employed three separate seismic techniques. The three-dimensional (3D) surface seismic survey required significant planning, design, and processing, but produces both a better understanding of the subsurface structure and a three-dimensional velocity model, which is essential for the second technique, a timelapse vertical seismic profile, and the third technique, cross-well seismic tomography. The timelapse 3D Vertical Seismic Profile (3D VSP) revealed both significant changes in the reservoir between the second and third surveys and geo-bodies that may represent the extent of the underground carbon dioxide. The asymmetry of the primary geo-body may indicate the preferential migration of the carbon dioxide. The third technique, cross-well seismic tomography, suggested a strong correlation between the well logs and the tomographic velocities, but did not observe changes in the injection interval.

Morphological Variation of the Mandible in the Orthognathic Population-A Morphological Study Using Statistical Shape Modelling.

The aim of this study was to investigate the value of 3D Statistical Shape Modelling for orthognathic surgery planning. The goal was to objectify shape variations in the orthognathic population and differences between male and female patients by means of a statistical shape modelling method. Pre-operative CBCT scans of patients for whom 3D Virtual Surgical Plans (3D VSP) were developed at the University Medical Center Groningen between 2019 and 2020 were included. Automatic segmentation algorithms were used to create 3D models of the mandibles, and the statistical shape model was built through principal component analysis. Unpaired t-tests were performed to compare the principal components of the male and female models. A total of 194 patients (130 females and 64 males) were included. The mandibular shape could be visually described by the first five principal components: (1) The height of the mandibular ramus and condyles, (2) the variation in the gonial angle of the mandible, (3) the width of the ramus and the anterior/posterior projection of the chin, (4) the lateral projection of the mandible's angle, and (5) the lateral slope of the ramus and the inter-condylar distance. The statistical test showed significant differences between male and female mandibular shapes in 10 principal components. This study demonstrates the feasibility of using statistical shape modelling to inform physicians about mandible shape variations and relevant differences between male and female mandibles. The information obtained from this study could be used to quantify masculine and feminine mandibular shape aspects and to improve surgical planning for mandibular shape manipulations.

Offshore subsurface characterization enabled by fiber-optic distributed acoustic sensing (DAS): An East China Sea 3D VSP survey example

Recent advances in distributed acoustic sensing (DAS) technology have allowed more intense measurements of subsurface and environment events, providing improved geohazard monitoring and subsurface characterization. This study discussed the subsurface evaluation enabled by the DAS-vertical seismic profiling (DAS-VSP) system in the East China Sea, China. Taking advantage of a continuous recording of the vibrational wavefields through the strain deformation of the fiber deployed along the borehole, DAS-VSP is considered an emerging and promising alternative borehole acquisition method. It provides a wider-spectrum range of recordings in a cheaper, denser, and more continuous tense compared to conventional geophones. We explored the 3D DAS-VSP signal processing and imaging strategy. Based on a set of 3D DAS-VSP data of exceptional quality, this study reviewed the common processing challenges and practical solutions for de-noise, de-ghosting, de-multiple, and wavefield separation arising from the DAS acquisition mechanism in the offshore VSP scenario. High-quality down-going multiples were separated and imaged using the pre-stack Gaussian beam depth migration in addition to the primary reflection wavefield, providing significant additional illumination to support the subsurface evaluation. The current results validated the efficiency of the DAS-VSP survey and encouraged better geological interpretation.

Joint Obn and 3D Das-Vsp Data Acquisition and Processing in the East China Sea

Borehole and surface joint seismic exploration is a 3D seismic exploration method formed by the combination of surface seismic and VSP survey simultaneously. Using the 3D DAS-VSP data, accurate time-depth relationship, formation velocity, deconvolution operator, spherical diffusion compensation factor, absorption attenuation factor, anisotropy parameters and high-resolution structural imaging around the wellbore can be obtained. These parameters can be used to significantly enhance the surface 3D seismic data processing. This paper describes the 3D DAS-VSP data acquired by a downhole armoured optical cable simultaneously with an OBN data acquisition project in East China Sea, and the results of 3D DAS-VSP data imaging processing. The usual 3D VSP data imaging processing steps include: observation system definition, preprocessing, first arrival picking, static correction, amplitude compensation, deconvolution, wavefield separation, velocity analysis and imaging. Based on the characteristics of offshore 3D VSP downgoing multiples, the offshore 3D VSP downgoing multiple imaging technique has been innovatively developed. This greatly expands the 3D DAS-VSP imaging range and improves the overall 3D DAS-VSP imaging quality. The 3D DAS-VSP downgoing multiple reflection wave imaging shows significant imaging quality improvement in comparison with the vintage 3D OBC data imaging. The detailed structure, tracing of the reservoir and formation tops becomes easier and less ambiguous using both new OBN data imaging and 3D DAS-VSP data imaging when compared with the vintage 3D OBC data imaging.

Frequent 4D monitoring with DAS 3D VSP in deep water to reveal injected water-sweep dynamics

Time-lapse monitoring using 3D distributed acoustic sensing vertical seismic profiles (DAS VSPs) is rapidly maturing as a nonintrusive low-cost solution for target-oriented monitoring in deep water. In a Gulf of Mexico field, DAS fibers deployed in active wells enable detailed tracking of the water flood in two deep reservoirs. Multiple tests in adverse well conditions let us understand the impact of source size and other factors on the spatially dependent quality of time-lapse DAS data and prove that excellent image repeatability is achievable under typical field conditions. Frequent repeat surveys allowed us to predict the timing of water arrival in a producer and to observe new water injection patterns that are important for understanding water-flood performance. Going forward, DAS 4D monitoring is envisioned as a tool that can assist with proactive wells and reservoir management, new well planning, and reservoir model updates.

Anisotropy analysis from 3D VSP surveys acquired at Otway site

Anisotropy analysis from 3D VSP surveys acquired at Otway site

Extraction and characterization of faults and fractures from 3D VSP data in a carbonate reservoir: A workflow

We present a workflow for the extraction and characterization of fractures and faults using a Reverse Time Migrated (RTM) volume from 3D Vertical Seismic Profile data (3D VSP) acquired in an oilfield offshore Abu Dhabi in the United Arab Emirates. The workflow consists of: preconditioning of the input RTM volume, which involves removal of acquisition footprints; extraction of faults and fractures using a semblance based discontinuity attribute; binary filtering and clustering for characterization and interpretation using prior geological information, as well as removals of unwanted features such as those related to stratigraphy; and finally interpretation. Complex networks of lineaments were extracted after application of the workflow. The location of lineaments with length greater than 200 m and orientated WNW-ESE to NW-SE correlates with a known flower structure which has a trend similar to that of the Proterozoic Najd Fault System that cut the Arabian Peninsula. Lineaments with strike directions ENE-WSW and NE-SW are interpreted to be related to reactivation of basement faults and correspond to the Hormuz Salt basin's major trend in the Arabian Gulf. Dominant strike directions of lineaments at three reservoir levels correlate with dominant strike directions of interpreted fractures from Fullbore Formation Microimager (FMI) and core data; thus implying that they are likely related to fractures or fracture corridors. Lineaments with orientation NNE-SSW correlate with closed fractures while lineaments with orientation NNW-SSE correlate with open fractures. Zones with relatively high fracture intensity are generally located north and north-west of the VSP well in the reservoir zones. The good correlation of the results with interpreted fractures from core and FMI data shows the robustness of the workflow and gives confidence to the results.

3D Vertical Seismic Profiling Acquired Using Fibre-Optic Sensing Das – Results From The CO2CRC Otway Project

Distributed Acoustic Sensing (DAS) is an optical interferometric method for acquisition of acoustic and seismic signals. It uses laser pulses that travel along the length of a fibre-optic cable and backscatter as they encounter small inconsistencies in the fibre. Impinging seismic waves cause strain on the cable, resulting in differences in phase of the backscattered light. Interest in DAS has increased significantly in the past decade as it is particularly suited for VSP acquisitions, including for permanent reservoir monitoring. Fibre-optic cables can be installed permanently in the well, cemented behind the casing or attached to tubing; they offer a relatively cheaper and efficient solution when compared to conventional borehole sensors. This study is part of the CO2CRC Otway Project. The Otway Project site is located approximately 240 km south-west of Melbourne, Australia. The Stage 2C of the project aims to monitor a small injection (15 kt) of CO2/CH4 gas mixture at a depth of approximately 1500 m. Here, we show the results of a 3D VSP survey acquired using DAS cable deployed on production tubing in the injector well. The DAS up-going wavefield shows a high level of noise. However, DAS is able to record the main reflections, including at the injection depth. After 3D migration of the data, noise levels reduce significantly. Events on DAS inline match with events on a corridor stack produced from a geophone check-shot data. Due to the directionality pattern, DAS was only able to image up to approximately 300 m radius from the well.

CO2 Storage Site Characterisation at Harvey, Western Australia Using Non-Conventional Seismic Survey Geometries

This stage of the South West Hub Carbon Capture and Storage (CCS) project aims to produce an in-depth integrated study of the fault and fracture network surrounding the Harvey 3 well to obtain an understanding of their propensity to act as conduits for the injected CO2. An additional interest to the seismic component of the study was to find an optimum CO2 sequestration monitoring methodology. This was of key importance since acceptance by the farming community across the area of the potential reservoir extent is crucial for successful completion of the project. These two factors were taken into account for the survey design that was comprised of more conventional components consisting of simultaneous recorded 3D surface and 3D VSP data sets and an alternative component that recorded multi-offset VSP (MOVSP) survey along the public roads. A comparative analysis of seismic imaging achieved with different geometries is discussed. One of the important results was that MOVSP surveys produced good results and hence this technique may be preferred for monitoring CO2 sequestration in this area. This was since it caused no disturbance to the farming ground and it was much more likely to gain acceptance with the landowners.

Seismic characterization and monitoring of a deep CO2 storage reservoir with 3D VSP using direct shear waves

We show a low-cost option for shear wave imaging of CO2 storage reservoirs that utilizes seismic waves that have been ignored by reflection seismologists for decades. These overlooked waves are direct-S waves generated by vertical-displacement vibrators and explosive sources. Shear waves are known to be helpful for detecting fractures and subtle faults which is critical for evaluating of CO2 storage capacity and sealing properties of the caprock. Utilizing direct-S waves produced by P-wave sources provides these benefits with no need to deploy special shear-wave sources. In addition, the SV-P mode, which is the upgoing P-wave produced by SV-to-P conversion, makes it possible to utilize S-wave attributes with data recorded by vertical geophones only.We developed a processing workflow to extract SV-SV and SV-P seismic modes from 3D VSP data acquired over a CO2 storage reservoir at Decatur, Illinois and tested these modes for seismic imaging and monitoring of the reservoir. In addition, we inspected an SH-SH mode that appeared interpretable in our data. We observed that direct-S images were consistent with traditional VSP direct-P images and calibration synthetic seismograms. A joint analysis of all available seismic modes allowed a constrained interpretation of faults within the reservoir. Direct-S waves appeared to not be advantageous for CO2 plume growth monitoring in the Decatur project. The SV-P mode demonstrated low sensitivity to CO2 concentration. The time-lapse difference for the SV-SV mode was uninterpretable due to the low signal-to-noise ratio of that mode.

Integration of completion data, microseismic data, downhole logs, and multicomponent seismic data in the Mississippi Lime, north-central Oklahoma

Previously published work on a Mississippi Limestone (Mississippi Lime) prospect in north-central Oklahoma described a prospect that is data rich. Aquisition was on a dense grid using nodal 3C phones, and PP and PS data were both processed and jointly inverted. Several pilot holes and laterals were drilled and fully logged, including Sonic Scanner and formation-microimager (FMI) fracture logs. Microseismic data were acquired on one well pad, as was a 3D VSP. New resesarch discusses two specific fracture-characterization methodologies. The first is the integration of vertical and lateral log suites, including fracture imaging, with seismic rock properties and completion results, including microseismic data. The results of this effort not only characterize fracture width and height but go farther by explaining why and how those fractures are created. The second is the use of converted-shear (PS) data to measure anisotropy and correlate those measurements with fracture logs. Specifically, two methods of calculating anisotropy are analyzed: slow shear-wave (S2) traveltime correction and transverse/radial energy ratio. Both methods are theoretically valid but might break down in practice because of various nongeologic artifacts that can be present in the data.

3D VSP and surface full-azimuth seismic integrated study in northeastern China

Great progress has been made on VSP techniques in recent years, especially the improvement of downhole geophone manufacture and VSP data-processing methods. In XJWZ area of Daqing oil field, the reservoir is formed mainly by volcanics, and its distribution is complex because of many periods of volcanic overlap in the area. Early seismic surveys in the area had been mainly 2D and narrow-azimuth 3D, which are not suitable for anisotropy analysis and fracture identification. Therefore, a joint survey of 3D VSP and full-azimuth surface seismic was implemented. The project was an attempt to combine the advantages of VSP and surface seismic by 3D VSP and full-azimuth surface-seismic simultaneous survey. Q factor and anisotropy parameters estimated from VSP are applied to 3D seismic processing. Reservoir characterization and gas-saturation prediction with final images showed encouraging results. Suggested wells have been drilled and wet gas has been found, so the validity of this method has been proved.

3D VSP: A mine of information for mining exploration

The 3DVSP technique becomes more popular with the emergence of multilevel 3 component borehole tools. The value of the information derived from VSP is not always well understood. In this paper we will present a case history of a joint surface and borehole seismic acquisition, with the goal to de-risk a shaft sinking location on a platinum mine. TD was about 650m and the VSP tool was 110m long. On surface a dense grid of receivers and vibrator source points were laid out in 1.2 km radius circle centered on the well head. A12 level 3C VSP digital tool was lowered in the borehole, in three successive depth positions. The surface 3D cube was processed and interpreted independently from a the 3D VSP data. On a near target reflector, the surface data structural interpretation showed mainly a clear E/W fault, and additional subseismic lineaments of differing azimuths, difficult to identify in terms of fault. The 3D VSP image limited to a short radius around the borehole confirmed the fault/dyke nature of these lineaments, separating monocline compartments. As a consequence, the surface data was carefully re-interpreted and on the second structural images derived from two surface seismic reflectors and the near surface fault footprint from 3DVSP residual statics, a series of subtle faults were clearly assessed. last, the few faults intersecting the borehole can be clearly recognized on the logs and the borehole radar logs. This case study demonstrates the added value of a joint interpretation of surface and borehole data in a decision making process for shaft sinking.

Distributed acoustic sensing for reservoir monitoring with VSP

3D VSP has long been viewed as conceptually attractive for illuminating targets under complex overburden, both for exploration purposes and for time-lapse monitoring of reservoirs. However, the widespread use of 3D VSP has been hindered by the cost and risk of deploying geophones in a borehole, and by the limited availability of accessible wells. These hurdles are largely removed when acquiring downhole seismic with a new measurement called distributed acoustic sensing (DAS).

Steam-injection monitoring in South Oman—from single-pattern to field-scale surveillance

Downhole seismic monitoring has become an alternative to more conventional surface seismic in cases where the latter has low signal-to-noise ratio or poor repeatability, or when frequent monitoring of a local target is required. Downhole 3D VSP monitoring has been applied to both onshore (O'Brien et al., 2004; Kiyashchenko et al., 2011) and offshore environments (Wu et al., 2011). In onshore environments, surface seismic repeatability often suffers from surface noise and near-surface variations caused by water-table changes or surface facilities construction. For VSP surveys, the wavefield separation into downgoing and upgoing fields presents an opportunity to discriminate between near-surface and reservoir changes, thus making time-lapse applications more effective.

Prediction of the seismic time-lapse signal of CO2/CH4injection into a depleted gas reservoir - Otway Project

Stage I of the Otway project conducted by the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) in 2007-2010 included injection of 66000 tons of CO2-rich gas into a depleted gas reservoir at Naylor field, Otway Basin, Victoria. In this paper we present a seismic modelling study that estimates the time lapse response of CO2/CH4 injection into the Waarre C reservoir. Based on the static geological model, acoustic impedance inversion of the seismic baseline data as well as log data, two models with different levels of detail in the reservoir properties are built. The distribution of the injected CO2/CH4 mixture in the reservoir and the gas properties are obtained from flow simulations. In order to predict the change in acoustic impedance after injection, we employed the Gassmann fluid substitution workflow. The modelled total differences in acoustic impedance for different amounts of CO2/CH4 injected are of the same order of magnitude for both models and reflect the CO2 mass fractions predicted by flow simulations. Finally zero incidence synthetic data are computed for these cases using a statistical wavelet of the baseline data. The computed synthetics are compared to surface seismic and VSP monitoring data. The repeatability of the surface seismic data is too low to detect the predicted signal. For the 3D VSP data, the time-lapse signal/noise has a similar order of magnitude as the predicted signal. It may have the level required to detect the signal.

Time-lapse 3D VSP using permanent receivers in a flowing well in the deepwater Gulf of Mexico

The vision of smart wells permanently instrumented with geophones has existed for some time. Such installations would enable opportunities for frequent reservoir monitoring, high-resolution 3D VSP imaging, and illumination of difficult areas. For many subsalt fields, 3D VSPs acquired in such wells may be the best option to illuminate and monitor reservoirs without the need to stop production or enter a well. However, this technology is not yet widely applied, nor perhaps proven.

Slowness surface construction and inversion from 3D VSP data

The emerging technology of three-dimensional vertical seismic profiles (3D VSPs) allows the extensive sampling of reflecting surfaces over a wide range of incident angles and azimuths. Such data can be used to provide additional insights into the effective rock properties associated with features that are below seismic resolution, such as layering or aligned systems of fractures which lead to elastic anisotropy. Here we analyse two 3D VSPs acquired in the Arabian Gulf and show how the data may be processed to extract slowness surfaces, how these surfaces can be used to estimate anisotropy parameters, and how the anisotropy relates to the geological characteristics of the formation and its stress history.