Seismic solutions utilizing existing in-mine infrastructure for mineral exploration: A case study from Maseve platinum mine, South Africa

We demonstrate the application of seismic methods using in-mine infrastructure such as exploration tunnels to image platinum deposits and geologic structures using different acquisition configurations. In 2020, seismic experiments were conducted underground at the Maseve platinum mine in the Bushveld Complex of South Africa. These seismic experiments were part of the Advanced Orebody Knowledge project titled “Developing technologies that will be used to obtain information ahead of the mine face.” In these experiments, we recorded active and passive seismic data using surface nodal arrays and an in-mine seismic land streamer. We focus on analyzing only the in-mine active seismic portion of the survey. The tunnel seismic survey consisted of seven 2D profiles in exploration tunnels, located approximately 550 m below ground surface and a few meters above known platinum deposits. A careful data-processing approach was adopted to enhance high-quality reflections and suppress infrastructure-generated noise. Despite challenges presented by the in-mine noisy environment, we successfully imaged the platinum deposits with the aid of borehole data and geologic models. The results open opportunities to adapt surface-based geophysical instruments to address challenging in-mine environments for mineral exploration.

Unlocking ultra-high-density seismic for CCUS applications by combining nimble nodes and agile source technologies

In the quest for denser, nimbler, and lower-cost seismic surveys, the industry is seeing a revolution in the miniaturization of seismic equipment, with autonomous nodes approaching the size of a geophone and sources becoming portable by crews on foot. This has created a paradigm shift in the way seismic is acquired in difficult terrains, making zero-environmental-footprint surveys a reality while reducing cost and health, safety, and environmental risk. The simplification of survey operation and the new entry price of seismic surveys unlocked by these technologies are already benefiting industries beyond oil and gas exploration. High trace density seismic has become accessible to industries playing a key role in the net-zero era, such as geothermal and carbon capture, utilization, and storage (CCUS), to which a good understanding of the subsurface geology is crucial to their success. We describe these benefits as observed during an ultra-high-density seismic survey acquired in June 2020 through a partnership between STRYDE, Explor, and Carbon Management Canada over the Containment and Monitoring Institute site. The smallest and lightest source and receiver equipment in the industry were used to achieve a trace density of 257 million traces/km2 over this test site dedicated to CCUS studies. We discuss the operational efficiency of the seismic acquisition, innovative techniques for data transfer and surveying, and preliminary results of the seismic data processing with a focus on the near-surface model and fast-track time migration.

Stratigraphic Study for the Cretaceous-Tertiary period in Qasab-Jawan area in north weastern Iraq by using 2D seismic survey

A seismic study was conducted to re-interpret the Qasab and Jawan Oil fields in northwestern Iraq, south of the city of Mosul, by reprocessing many seismic sections of a number of field surveys by using the Petrel software. Two reflectors, represented by the Hartha formation, deposited during the Cretan age, and the Euphrates formation, formed during the Tertiary age, were delineated to stabilize the structural picture of these fields. The stratigraphic study showed that the Qasab and Jawan fields represent areas of hydrocarbon accumulation. Seismic attribute analysis showed low values of instantaneous frequency in the areas of hydrocarbon accumulation. Instantaneous phase was used to determine the limits of the sequence, the nature of sedimentation, and the type of vanishing, i.e. onlap vs. toplap. Low instantaneous amplitude values were recorded, indicating hydrocarbon reservoirs in the studied area. Various other seismic stratigraphic features were studied , including the distribution mound, flat spot, and channels in the two formations, but they were discontinuous because of the tectonic effects. These activities explain reasonably the distribution of hydrocarbons in the studied area.

Integrated approach to the typification and localization of deposits of the anomalous section of the Bazhenov formation of the Frolov oil and gas region

Introduction. The subject of the study of this work is the deposits of the anomalous section of the Bazhenov formation (ASB) of Western Siberia, the disturbed occurrence of which was recorded by 2D, 3D seismic exploration and borehole data at many fields of the Frolov oil and gas region. The research area unites the company’s assets in the KhMAO and the Tyumen region, which are part of the large hydrocarbon cluster “ZIMA”. Aim. In order to typify various complexes of rocks of the Bazhenov formation and further localization of deposits, a comprehensive core analysis, GIS and seismic studies were performed. Materials and methods. According to the results of lithological study of the core and petrophysical interpretation of logging diagrams, have been identified various types of rocks in the interval of the Bazhenov formation. According to the results of the interpretation of the seismic survey materials, contoured zones that differ in the wave pattern by different coherence of the axes of common phase. The revealed differences in seismic sections compared with borehole data and geological bodies mapped based on the obtained patterns. Results. Based on a comprehensive interpretation of the core, GIS and seismic studies, established the zonality of the distribution of various types of deposits of the Bazhenov formation, the relationship of the development of ASB zones with the introduction of Early Cretaceous sedimentary bodies and showed the introduction of detrital material from the overlying rocks. Conclusions. The authors of the article conclude that the development of anomalous sections of the Bazhenov formation involves several stages of the introduction of landslide bodies of overlying rocks, according to the gradation of Neocomian clinocyclites in the north-west direction. Within the study area, mapped three large landslide bodies in the Bazhenov formation interval, each of which was formed an internal zonality and because of the introduction of rocks from the overlying interval.

Facies models of hydrocarbon-bearing formations of Podneytinskiy reservoir at Bovanenkovskoye and Kharasaveyskoye fields

Background. Significant part of hydrocarbons at Bovanenkovskoye and Kharasaveyskoye fields are contained in Podneytinskiy reservoir, and study of geological features of its productive strata is important for development planning for the fields in a whole. Aim. The paper reflects the results of integrating well and seismic data to characterize the formations of Podneytinskiy reservoir at Bovanenkovskoye and Kharasaveyskoye fields. Materials and methods. As part of the study, sedimentological description of core was analyzed, the core, well logging and seismic survey information were assessed, and the facies schemes were prepared. Results. As a result of the work, the reservoir architecture features and the distribution of reservoir properties of the target interval were revealed. It has been established that the considered formations of Podneytinskiy reservoir can be divided into two parts, the lower one is represented by deposits of predominantly deltaic origin, and the upper one is of continental and subcontinental genesis. The sedimentary conditions of rocks influenced the complexity of their architecture, so, in the formations referred to the lower part of the studied interval, the reservoirs, as a rule, are laterally continuous, in contrast to the deposits of the upper part of the section, which are typically characterized by extremely high lateral heterogeneity. Depositional conditions also influenced the reservoir properties of productive sediments. As a result of the work, it was revealed that the reservoirs of better quality are formed in fluvial and tidal channels, distributary channels and proximal parts of deltas, they have higher reservoir properties, are characterized by thicker sandstone interlayers and lower portion of carbonated interlayers in comparison with reservoirs formed in other conditions. Conclusions. The article provides quantitative characteristics of reservoir properties depending on sedimentary conditions. The results obtained form the basis for creation of geological models of Bovanenkovskoye and Kharasaveyskoye fields.

The Seismic Interpretation for (X) Oil Field Depending on 3D Seismic Data of Nearby Oil Field, Southern Iraq

This research focused on using seismic data to review the structure of the (X) Oil Field, located 40 km SW of Basrah, Southern Iraq. The study utilises a 3D seismic survey conducted during 2011-2012, covering the (Y) Oil Field 2 km to the west, and with partial coverage across (X), to map the Top Zubair reflector. Seismic rock properties analysis was conducted on key (X) Oil Field wells and used to tie the Top Zubair reflector on (X) Oil Field. The reflector was mapped within the time domain using DecisionSpace Software, and then converted to depth using a velocity model. The depth structure map was then compared to the original oil water contact (OOWC) across the fields to understand the potential structural closure of the Top Zubair reservoir in both fields.

Overcoming CO2 Injector Well Design and Completion Challenges in a Carbonate Reservoir for World's First Offshore Carbon Capture Storage CCS SE Asia Project

Oil & Gas Operators are focusing on zero carbon emission to comply with government's changing rules and regulations, which play an important role in the encouragement of carbon capture initiatives. This paper aims to give insights on the world's first offshore CCS project in carbonate reservoir, where wells will be drilled to inject CO2, and store produced CO2 from contaminated fields. To safeguard the storage containment, the integrity of all wells needs to be scrutinized. Development wells in the identified depleted gas field are more than 40 years old and were not designed with consideration of high CO2 concentration in the reservoir. In consequence, the possibility of well leakage due to accelerated corrosion channeling and cracks, along the wellbore cannot be ignored and require careful evaluation. Rigorous process has been adopted in assessing the feasibility for converting existing gas producers into CO2 injectors. The required defined basis of designs for gas producer and CO2 injection wells differs in a great extent and this governs the re-usability of wells for CO2 injection or necessity to be abandoned. Three (3) new CO2 injectors with fat to slim design approach, corrosion resistant alloy (CRA) material and CO2 resistant cement are designed in view to achieve lifecycle integrity. Optimum angle of 53 deg and maintaining the injection pressure of 50 bar at 90 MSCFD rate is required for the injection of supercritical CO2 for 20 years. During well execution, challenges such as anti-collision risk, total loss scenarios while drilling in Carbonate reservoir need to be addressed before execution. The completion design is also focusing on having minimal number of completion jewelries to reduce pressure differential and potential leak paths from tubing hangar down to the end of lower completion. The selection of downhole safety valve (TRSV) type is of high importance to accommodate CO2 phase attributes at different pressure/temperature. Fiber Optic is included for monitoring the migration of CO2 plume by acquiring seismic survey and for well integrity by analyzing DAS/DTS data.

The Role of Legacy Seismic in Enhancing the Image in the Current Seismic Data – Abu Dhabi: Case Study

Acquiring surface seismic data can be challenging in areas of intense human activities, due to presence of infrastructures (roads, houses, rigs), often leaving large gaps in the fold of coverage that can span over several kilometers. Modern interpolation algorithms can interpolate up to a certain extent, but quality of reconstructed seismic data diminishes as the acquisition gap increases. This is where vintage seismic acquisition can aid processing and imaging, especially if previous acquisition did not face the same surface obstacles. In this paper we will present how the legacy seismic survey has helped to fill in the data gaps of the new acquisition and produced improved seismic image. The new acquisition survey is part of the Mega 3D onshore effort undertaken by ADNOC, characterized by dense shot and receiver spacing with focus on full azimuth and broadband. Due to surface infrastructures, data could not be completely acquired leaving sizable gap in the target area. However, a legacy seismic acquisition undertaken in 2014 had access to such gap zones, as infrastructures were not present at the time. Legacy seismic data has been previously processed and imaged, however simple post-imaging merge would not be adequate as two datasets were processed using different workflows and imaging was done using different velocity models. In order to synchronize the two datasets, we have processed them in parallel. Data matching and merging were done before regularization. It has been regularized to radial geometry using 5D Matching Pursuit with Fourier Interpolation (MPFI). This has provided 12 well sampled azimuth sectors that went through surface consistent processing, multiple attenuation, and residual noise attenuation. Near surface model was built using data-driven image-based static (DIBS) while reflection tomography was used to build the anisotropic velocity model. Imaging was done using Pre-Stack Kirchhoff Depth Migration. Processing legacy survey from the beginning has helped to improve signal to noise ratio which assisted with data merging to not degrade the quality of the end image. Building one near surface model allowed both datasets to match well in time domain. Bringing datasets to the same level was an important condition before matching and merging. Amplitude and phase analysis have shown that both surveys are aligned quite well with minimal difference. Only the portion of the legacy survey that covers the gap was used in the regularization, allowing MPFI to reconstruct missing data. Regularized data went through surface multiple attenuation and further noise attenuation as preconditioning for migration. Final image that is created using both datasets has allowed target to be imaged better.

Lessons Learnt Reprocessing a Noisy Onshore 3D Seismic Survey

An 1,100 km2 400-fold seismic survey was acquired over some of the largest sand dunes in UAE in 2007. Large sand dunes generate many challenges for seismic processing due to the irregular data acquisition, large statics caused by the significant difference between the sand and sabkha velocities, and a massive amount of reverberation noise that hides the signal in the data. Occidental and ADNOC Sour Gas reprocessed this survey from January 2019 to August 2020 to overcome the challenges of the strong sand dune noise. For the first time, it was processed through prestack depth migration (PSDM). The primary objectives of the reprocessing project were to get an accurate PSDM volume that tied all of the available well control data; and to derive as accurate seismic amplitudes as possible over the target reservoir interval from near to far offsets to enable elastic inversion for reservoir porosity and net-thickness prediction. Whilst the reprocessing project achieved the project objectives and generated good subsurface images, it did not run as smoothly as hoped, despite being processed by one of the premier multinational processing companies. The extremely large sand dunes, which are present across most of the survey area, created major imaging problems. Key technical lessons learnt during reprocessing included: (1) CRS errors occurred sporadically during acquisition, requiring correction; (2) the sand curve (Liner, 2008) worked well for sand dune static corrections for this data set; (3) near surface statics changed whilst the survey was acquired by up to 6 ms - each shot station needed to be corrected for these statics changes because the shot stations were acquired twice with a symmetric split recording spread; and (4) the contractor's standard post-migration processing sequence (gather flattening, radon, noise attenuation, stack) did not work well for this very noisy data set. Next time we work with similar data and require a high quality result, we know to double the estimated project timeline as every step in the processing sequence takes much longer than expected when the signal-to-noise ratio of the data is very low. The novelty of this work was that we obtained large improvements in the seismic stack by applying offline gather conditioning before calculating trim statics to optimally flatten the very noisy migrated offset vector tile (OVT) gathers, prior to running the final noise attenuation and stacking workflows. Without this offline gather conditioning, the trim statics workflow mostly aligned the noise and damaged the stack.