Refracted seismic waves recorded on Ocean Bottom Nodes (OBN) from all azimuths benefit from high Signal-to-Noise Ratio (SNR) and may provide important information about deepwater reservoirs, especially those below massive salt bodies. For target-oriented imaging, refracted wave paths can help understand accurately how the geometry of acquisition illuminates the target region, thereby supporting cost-effective survey designs. To this end, we study two techniques: (i) wave paths calculated by a Reverse Time Migration (RTM) algorithm for refracted wave events selected in synthetic seismograms; (ii) ray tracing using the eikonal equation. We discuss illumination examples for two models: a 3D velocity model typical of the Brazilian pre-salt fields and a simplified multilayered 2D approximation. We show that wave paths can map a given source-receiver pair into illuminated regions for selected refracted first arrivals. For the pre-salt refractions we can establish an offset range for successful reservoir imaging. Presentation Date: Wednesday, October 14, 2020 Session Start Time: 9:20 AM Presentation Time: 11:00 AM Location: Poster Station 8 Presentation Type: Poster

Deepwater Gulf of Mexico Auger and Cardamom fields are mature brownfields with more than 25 years of production. Economic infill opportunities are increasingly smaller in dimension. Identifying and adequately derisking these opportunities are critical to the continuous success of the asset. However, this had become more and more difficult on the basis of available vintage streamer and OBN seismic data, thus leading to the plan of acquiring new OBN data in Q1 2019 and in parallel reprocessing available legacy OBN and streamer (WAZ/NAZ) data to ensure optimum data quality through a new state of the art velocity model. Time-Lag Full Waveform Inversion (TLFWI) along with better illumination provided by the OBN data was instrumental in obtaining an improved velocity model, which resulted in better seismic positioning, resolution and amplitude fidelity. TLFWI helped in reducing azimuthal move-out discrepancies of the reservoir sands by enhancing the resolution of the overburden velocity field. Furthermore, a new salt interpretation for the root of the Auger salt dome resulting from the project provided new insights to the geological understanding of the Auger sediment basin and salt depositional model. Incorporating the newly acquired OBN data midway during the velocity modeling improved stability of the velocity inversion in the part of the Auger basin that lacked legacy OBN coverage, which led to overall improved amplitude fidelity. The uplift in seismic imaging enabled identification of additional new and verification of known economic infill opportunities as well as the deselection of non-viable targets. Presentation Date: Tuesday, October 13, 2020 Session Start Time: 1:50 PM Presentation Time: 4:45 PM Location: 362A Presentation Type: Oral

The formation evaluation of the unconventional tight sand reservoirs is challenging at different points of view, where several factors affect the recording and make their evaluation and the potential in place assessment hard to define. That’s why, the new technologies and customized workflows that are being applied in such reservoirs are greatly helping in decreasing the uncertainties encountered at different levels of the unconventional tight sand reservoirs lifecycle. One of the milestone steps is the formation fluids identification and sampling. In the past, the selection method of the intervals for formation fluids sampling using the MDT tool was based on conventional well logging analysis and more precisely on selecting intervals with high porosity compared to other intervals. However, this method has shown its limitations in tight reservoirs due to the low porosity and low permeability. For that reason, Schlumberger has established a new customized workflow known as ‘Fracture Ready Package’ in order to optimize formation fluids sampling program, which consists on an orientation to the characterization of natural fracturing which represents a major element in tight reservoirs cases. This methodology consists of the combination of acoustics (Sonic Scanner) and borehole image services to conduct a complete and detailed natural fractures characterization, namely: type of fracture (open fracture, semi open, closed cemented fracture) orientation and the exact location of the fracture and most important, analyze the continuity of the fracture far from well wall by analyzing anisotropy using sonic scanner tool. Presentation Date: Monday, October 12, 2020 Session Start Time: 1:50 PM Presentation Time: 3:05 PM Location: 360D Presentation Type: Oral

The complex structuring of the Andaman Sea, situated at the northern edge of the Southeast Asia Archipelago, is bordered at its western side by a subduction zone, accretionary prism and a volcanic arc. The basin proper embraces diverse tectonic features in its fore-arc, volcanic arc and back-arc provinces. A central spreading center splits volcanic ridges and the large back-arc region of its eastern side. This paper describes the seismic expression de-risking of the shallow and deeper structure and stratigraphy of these quite diverse geologic provinces of Andaman Sea, a vast Tertiary basin that is still largely unknown and under-explored. Presentation Date: Wednesday, October 14, 2020 Session Start Time: 9:20 AM Presentation Time: 11:25 AM Location: Poster Station 10 Presentation Type: Poster

The Benue Trough has been generally described as an elongate rift filled with Cretaceous sediments that are up to 6000 meters thick and has been divided into the Lower, Middle and Upper arms. The Benue Trough is itself a product of the West and Central African Rift System. Several models have been put forward for the evolution of the Trough but all of them still remain controversial due to insufficient data on its tectonic framework, thermal history, and relationship between tectonics and sedimentation. The purpose of this study is to interpret available new aeromagnetic data to study the tectonic framework of part of the trough (Upper-Benue trough) with a view to understanding the evolution of the trough. NigeriaSat-X and SPOT 5 imageries covering the basin were processed and interpreted and lineaments mapped out from them with the aid of the digital elevation model (DEM) of the basin. Several enhancement transforms such as first vertical derivative (FVD), Tilt derivative (TDR) and Total horizontal derivative (THDR) were applied to the total magnetic intensity (TMI) grid of the basin after which the basement faults were mapped out. The depths to the source hence sedimentary thickness were also derived from the magnetic field using methods like Spectral Analysis and Source Parameter Imaging (SPI) or Local wavenumber. The lineaments from the SPOT 5 data show a predominant NNE-SSW, NE-SW followed by the NNW-SSE with a few N-S and E-W trends and the basement configuration show a predominantly NE-SW trend which is the predominant trend in the Benue Trough while a few strike in the N-S,NW-SE, and WNW-ESE direction. This suggests that the basin was subjected to several stress regimes. Differential uplift of the basement fault blocks may also have given rise to drape folds observed in the overlying sediments. The Benue Trough maybe an old rift that has gone through several processes such as block faulting, volcanism, emplacement of basic igneous material within the basin and that all volcanic activity ceased before the Tertiary. The sediments of the Gongola and Yola arm of the basin have potential for hydrocarbon generation. Presentation Date: Tuesday, October 13, 2020 Session Start Time: 1:50 PM Presentation Time: 2:15 PM Location: Poster Station 6 Presentation Type: Poster

There is a great need for access to clean, safe water in many locations across the globe. DC resistivity has been demonstrated to be a viable approach to locating a good location for drilling water wells. However, lack of experience, lack of training or improper training, and no or little access to software results in the drilling of dry holes. This was the situation in Rwanda. Presentation Date: Monday, October 12, 2020 Session Start Time: 1:50 PM Presentation Time: 3:30 PM Location: 360C Presentation Type: Oral

Since the mid 1980’s, amplitude versus offset (AVO) data have been used by earth scientists to help in the prediction of lithology using seismic data. Although previous work has greatly aided in our ability to interpret AVO data, the AVO response cannot be easily visualized with respect to changes in rock properties, lithology, porosity, fluid type, and fluid saturation utilizing available techniques. The “AVO Template” we introduce allows for this visualization. The AVO Template is a graphical display that predicts the AVO responses at a lithologic interface using rock properties and Shuey’s parabolic approximation to Zoeppritz equations. The AVO Template allows an interpreter to visualize the changes in AVO response caused by changes in rock properties. In conjunction with a Rock Physics Template, the AVO Template can also be used to help estimate fluid type, porosity, and fluid saturation. Given the proper choice of parameters, the AVO Template can be used to help predict the probability of hydrocarbons in a prospective reservoir. Possible applications of the AVO Template include conventional and unconventional exploration and production, 4D seismic interpretation, and other applications where seismic data are used to predict lithology. Presentation Date: Wednesday, October 14, 2020 Session Start Time: 1:50 PM Presentation Time: 3:30 PM Location: 362A Presentation Type: Oral

The ChengBei eastern slope locates in the southwestern of the Bozhong Sag. It has superior hydrocarbon supply conditions. Drilling has confirmed that reservoirs are not developed in Paleogene, but there are oil reservoirs when sand is found. Aiming at problems such as fewer exploration wells in the target area, low resolution of Paleogene seismic data, rapidly lateral change of reservoir, and difficulty in identifying seismic lithofacies, this paper proposes a frequency-divided iterative inversion method under the constraint of sedimentary facies through the innovations in petrophysical modeling and seismic inversion methods. Finally, through the characterization of reservoir distribution, it provideds a strong support for the next well deployment. Note: This paper was accepted into the Technical Program but was not presented at the 2020 SEG Annual Meeting.

We present the methodology and processing schemes that use 3D field data to obtain the reservoir characteristics and metallogenic regularity of sandstone type uranium deposit. Firstly, the tectonic characteristic of uranium reservoir is extracted by superimposing uranium anomaly onto the results of structural interpretation. Secondly, we obtain the sedimentary characteristics of uranium reservoir by the extraction and optimization of seismic attribute. Then, the lithological characteristic of uranium reservoir is acquired by adding the uranium anomaly into the 3D lithological inversion data. Finally, we establish a 3D comprehensive geological model integrated uranium anomaly, structure, sedimentation, lithology to study the metallogenic regularity of sandstone type uranium deposit. Numerical results show that the scheme based on 3D seismic interpretation can get 3D, high-resolution, intuitive and multi-perspectives characteristics of uranium reservoir and the 3D comprehensive geological model integrated these characteristics is conducive to the 3D visualization analysis to the metallogenic regularity of sandstone type uranium deposit. Presentation Date: Tuesday, October 13, 2020 Session Start Time: 1:50 PM Presentation Time: 3:55 PM Location: Poster Station 4 Presentation Type: Poster

At present, Bohai oilfield has entered the second time interpretation stage. It is an effective means to find new structural traps by changing the original extension fault interpretation mode into the new strike-slip fault mode especially in Bohai Bay section of Tanlu fault zone. How to prove that the new strike-slip fault mode is correct? In this paper, we try to consider it from the aspect of tectonic stress field: through the development and application of tectonic stress field numerical simulation technology based on fault mode, fracture orientation information (dip angle and dip azimuth) in well and formation stress in wellbore. We respectively simulate the tectonic stress field formed by the two interpretation models and predict the corresponding fracture distribution. Then analyze the two predicted fracture orientation information and the actual fracture orientation information in well to see that which match better, so this interpretation mode is reasonable and correct. This study takes the fault system second interpretation of MiaoXi area in Bohai Bay Basin as an example (Figure 1). The main faults under original extension fault interpretation mode and new strike-slip fault mode are modeled in depth domain respectively. Combined with actual fracture information in well and the stress parameters from drilling and logging data, the numerical simulation of tectonic stress field is carried out respectively. It is confirmed that the coincidence rate of predicted fracture orientation information under strike-slip fault mode is 85%, and that under extension fault mode is 65%. Therefore, the strike-slip fault interpretation mode is more reasonable in MiaoXi area. New discovered structural traps’ area is more than 20km2, Provide high quality structural traps for oil and gas exploration. Note: This paper was accepted into the Technical Program but was not presented at the 2020 SEG Annual Meeting.

The Norwegian Petroleum Directorate (NPD) has confirmed that “During the last ten years, ~35% of the targets in the Norwegian part of the North Sea have been related to stratigraphic traps while ~65% to structural traps. This supports the hypothesis that the Norwegian sector of the North Sea may match that of the UK sector of the North Sea where the largest proportion (33%) of the undiscovered resources are believed to be hosted within stratigraphically-trapped post-rift reservoirs, predominantly in Paleogene deep-water strata. The study area is called NPC-4 which is classified as an unconfirmed play in the northern Norwegian North Sea. The focus of this study is on the Sele and Lista formations within the Rogaland Group of the Paleocene age with deep marine depositional environments. The goal of the research is mapping potential reservoir-quality deep-water sandstones. The available data includes: 2D seismic lines in both strike and dip directions, 3D seismic that cover the study area, well logs data for all wells in the study area, stratigraphic and final well reports for all the available wells, images of core samples for some of the wells, and 3D pre – stack seismic data that cover the study area. The methodology includes: 1) interpreting the available seismic data and identifying sequence boundaries and existing faults; 2) Doing Seismic facies analyses for the selected seismic lines; 3) Correlation of key wells; 4) Creating a lithofacies framework 5) Mapping the deep – water sandstones in the study area; and 6) Identifying the type hydrocarbon accumulation in those deposits. Sequence and seismic facies analyses have been performed for selected seismic lines depending on the bounding relationships, reflection configuration, reflection amplitude, and reflection continuity. Six seismic facies have been determined. In well logs correlations, Maximum Flooding Surface (MFS) at the base of the package has been used as a datum to correlate logs from key wells for selected sections. This helped with identifying the architecture of the sandstone deposits in the study area. Good resolution images for the core samples from four wells in the study area were used to identify the lithofacies in Sele and Lista formations. Eleven lithofacies were identified in those core sample images. The 3D pre – stack seismic data have been used to do the Amplitude Versus Offset (AVO) analysis to identify the types of the hydrocarbons in the identified sandstone deposits. Seismic sequence and facies analyses helped isolate packages with a higher probability of deep-water sand deposits. Log correlations show compensationally stacking lobes forming a sand-rich lobe complex. No evidence for channelization has been documented in the logs, cores, or seismic data. Sedimentary structures in the available core images such as normal grading, the massive sandstone, the ripples laminated sandstone and the planar lamination are interpreted at Bouma Ta and Tb divisions. The fine-grained and thinly-bedded lithofacies suggest that existing cored wells most likely intersected the Sele and Lista along a lobe fringe. Presentation Date: Wednesday, October 14, 2020 Session Start Time: 9:20 AM Presentation Time: 9:20 AM Location: Poster Station 10 Presentation Type: Poster

We present the results of electromagnetic (EM) studies over deep copper-sulphide orebody in the South Urals. This study is aimed mainly at testing the EM method’s capability of detecting orebodies of such shape, depth, and composition. The 3D modeling showed the potential of detecting the deep relatively small orebody with AMT/CSEM. The most appropriate technique for such deposits allocation was suggested according to the study results. Presentation Date: Wednesday, October 14, 2020 Session Start Time: 1:50 PM Presentation Time: 3:05 PM Location: Poster Station 2 Presentation Type: Poster

Carbonate cavity reservoirs have been a challenge in the industry for hydrocarbon exploration and production. Seismic imaging is able to find the cavities using the ‘beam string’ reflections. However, it lacks the detail of the cavities and the faults, sub-faults and fractures around them. During the production phase, it turns out that the cavity structures and their related sub-faults and fractures could be critical. This means that the understanding of connectivity between cavities could help improve production. Also, due to its cavity nature, the geo-model is difficult to be used for reservoir simulation. However, the model serves a good tool for analytical analysis such as material balance. The goal of this work is to build a geo-model by using a Bayesian approach. By extracting the relative reflection strength such as RMS, the cavities can be identified more easily. Using steerable pyramid processing, the faults and sub-faults are recognized. By merging the cavities and sub-faults, we devised a ‘cotton tree’ display scheme. This structure and the corresponding inversion of its seismic form the constraints of geological modeling. The reservoir model is built using a strong seismic-constrained approach. Furthermore, the model is used to analyze the dynamic performance and for better reserves estimation. The connectivity between cavities is analyzed using the model and ‘cotton tree’ structure. The procedure demonstrates a valid tool for cavity connectivity analysis. Presentation Date: Wednesday, October 14, 2020 Session Start Time: 8:30 AM Presentation Time: 10:35 AM Location: 362A Presentation Type: Oral

With the deepening of exploration and development, more and more attention has been paid to the study of unconventional reservoirs, especially deep tight sandstone reservoirs. Due to the special physical properties of low porosity and low permeability and complex pore structure, the traditional rock physics model is no longer applicable. In this paper, a modeling method is proposed based on the complex mineral component model and the equivalent medium theory. This method subtly considers the four characteristics such as the diversity of tight sandstone matrix minerals, the irregularities of pore structure, the connectivity between pores and the anisotropy caused by fractures, and obtains multiple parameters that can reflect the characteristics of the reservoir pore structure. The pore structure parameters calculated by this model fully take into account the general laws of rock physics and regional differences, and have high accuracy. The application in a work area shows that this method can effectively mine the micro information hidden in the logging data, and can provide a reliable reference for the division of high-quality reservoir intervals. Presentation Date: Monday, October 12, 2020 Session Start Time: 1:50 PM Presentation Time: 2:40 PM Location: Poster Station 4 Presentation Type: Poster

Modern mineral exploration focuses in underexplored regions where the terrain and geological environments make the discovery of mineral ore deposits increasingly difficult. The availability of multi-physics data is potentially useful because the complementary information contained in each data set can be integrated into a common Earth model consistent with all available geoscientific information. The goal of this study is to develop a workflow for quantitative integration of geophysical and geological data for mineral exploration. We focus on two important components of the workflow: joint inversion and geology differentiation. Joint inversion allows physical property models to constrain each other at the inversion stage, resulting in structurally similar models and enhanced correlations between inverted physical property values. Geology differentiation makes use of the jointly inverted physical property values and builds a 3D quasi-geology model that shows the spatial distribution of various geological units. The proposed workflow is first tested on a synthetic data set before being applied to a set of airborne gravity and magnetic data in central British Columbia. We have successfully identified multiple geological units that are consistent with the airborne geophysical data and prior geological information. This work provides guidance for follow-up detailed geophysical surveys in the study area and highlights the benefits of integrative interpretation of multi-physics geoscientific data. Presentation Date: Wednesday, October 14, 2020 Session Start Time: 8:30 AM Presentation Time: 9:45 AM Location: 351D Presentation Type: Oral

Based on Monti Carlo simulation using laboratory measured rock physics data, we studied the effect of seismic anisotropy on the AVO gradient B and compared it with the gas saturation effect on AVO gradient. Our study shows that the former is usually much greater than the latter, and the seismic anisotropy affects the gradient B similarly when the reservoir formation is fully brine- saturated and when it is gas-saturated. Seismic anisotropy generally reduces the magnitude of the AVO gradient. Compared to its effect on gradient B, gas saturation usually has a much stronger effect on the AVO intercept A. Therefore, ignoring seismic anisotropy may make little difference in AVO interpretation for hydrocarbon identification. Presentation Date: Wednesday, October 14, 2020 Session Start Time: 1:50 PM Presentation Time: 4:45 PM Location: 362A Presentation Type: Oral

The Brazilian oil exploration frontier has changed from simple post-salt targets to deeper and more complex pre-salt targets. This new exploration scenario mostly focuses on Santos Basin, southeast Brazil, where prospects generally lie beneath complex salt bodies with canopy overhangs and salt stratification. In such regions, conventional narrow-azimuth towed-streamer (NATS) data often fails to produce an image that can adequately de-risk prospects in the exploration phase. Ocean bottom node (OBN) data, on the other hand, is known to improve seismic velocity model building and imaging over production fields. Velocity models and corresponding imaging after full-waveform inversion (FWI) are much improved when used with OBN data, which features highquality low frequency content, longer offsets, and full azimuthal coverage. Those are crucial ingredients for deep and complex targets. Unfortunately, OBN data are not commonly available at the beginning of the exploration cycle, when uncertainty and risk are high. To reduce exploration risk in Santos Basin, we studied deploying sparse nodes on an exploratory scale. Using a decimated field OBN data set from Santos Basin, we show that the sparse node acquisition provides enough information for a reliable inversion with FWI. This velocity model can then be paired with conventional NATS data to yield an image with more accurate positioning of subsurface structures. Moreover, the sparse node data itself can also be used for imaging; we demonstrated that it contains valuable information about the pre-salt formations. Finally, we combined conventional NATS data and sparse nodes acquisition data in a least-squares framework, producing a structural image that can potentially further reduce risks at the exploration phase. We also derived a metric that aims to quantify the quality of the resulting seismic images. Note: This paper was accepted into the Technical Program but was not presented at the 2020 SEG Annual Meeting.

Due to the presence of clay-rich sediments and saltwater, electrical conductivities in coastal estuary environments are highly variable and include extreme values. Terrain electromagnetic induction (EMI) methods are often deployed in coastal environments, as elsewhere, to map conductivity structures because portable instrumentation allows for rapid data acquisition. However, an important consideration is that portable EMI instruments assume there is a linear relationship between ground conductivity and ratio between the transmitted magnetic field and measured secondary magnetic field. Such an assumption is not valid for highly conductive material like saltwater. There is a need to model the 3D response of conductivity structures expected in a coastal setting to understand what a portable instrument is capable of resolving. We present example results from a 3D solver that illustrate the difference in response over a lateral conductivity boundary as a function of instrument orientation and conductivity contrast. The response gradient over a lateral boundary is steeper in a transverse profile than an inline profile. A vertical coplanar (VCP) coil orientation is better able to capture the changing eddy current pattern at a lateral boundary due to current accumulation at the edge of a discontinuous layer. Presentation Date: Wednesday, October 14, 2020 Session Start Time: 1:50 PM Presentation Time: 1:50 PM Location: 361A Presentation Type: Oral

Carbonate reservoirs in the S area of the Tarim Basin (China), with low porosity, complex fracture systems and dissolved pores, are ultra-deep hydrocarbon resources. Especially, cracks play an important role in reservoir connectivity and storage space. To study the effect of cracks on reservoir, we have performed measurements on limestone samples under different confining pressures, and used the self-consistent approximation model and Biot-Rayleigh theory to simulate. Based on the dependence of seismic Q on the cracks, a multiscale attenuation template (RPT) is built, based on P-wave attenuation, impedance and phase velocity ratio. Then, calibration of the RPT is performed at ultrasonic and seismic frequencies to estimate the total and crack porosities of reservoirs. The results indicate that the distribution of the microcracks and pores were obvious different in the reservoirs. The total porosity is low (mostly < 5%), which is consistent with the geological structure and well-log data. The crack porosity is mainly between 0.06% and 0.12%, its behavior shows a good agreement with the actual oil production reports. Presentation Date: Tuesday, October 13, 2020 Session Start Time: 8:30 AM Presentation Time: 8:30 AM Location: 362D Presentation Type: Oral

In oil & gas exploration, magnetic anomaly caused by reverse remanent magnetism is often ignored. With the exploration step moving to the fine stage, this problem needs to be paid great attention by the processing and interpretation researcher. In large area data processing, it is difficult to identify and separate the reverse remanent magnetic anomalies, some of the reverse magnetic anomalies need to be identified with the cooperation of processing means. Further more, we can carry out inversion and interpretation to achieve correct interpretation and comprehensive geological research. Presentation Date: Tuesday, October 13, 2020 Session Start Time: 1:50 PM Presentation Time: 2:40 PM Location: Poster Station 6 Presentation Type: Poster