Drilling Targets Research Articles

Using Mineral Chemistry to Aid Exploration: A Case Study from the Resolution Porphyry Cu-Mo Deposit, Arizona

AbstractThe giant, high-grade Resolution porphyry Cu-Mo deposit in the Superior district of Arizona is hosted in Proterozoic and Paleozoic basement and in an overlying Cretaceous volcaniclastic breccia and sandstone package. Resolution has a central domain of potassic alteration that extends more than 1 km outboard of the ore zone, overlapping with a propylitic halo characterized by epidote, chlorite, and pyrite that is particularly well developed in the Laramide volcaniclastic rocks and Proterozoic dolerite sills. The potassic and propylitic assemblages were overprinted in the upper parts of the deposit by intense phyllic and advanced argillic alteration. The district was disrupted by Tertiary Basin and Range extension, and the fault block containing Resolution and its Cretaceous host succession was buried under thick mid-Miocene dacitic volcanic cover, obscuring the geologic, geophysical, and geochemical footprint of the deposit.To test the potential of propylitic mineral chemistry analyses to aid in the detection of concealed porphyry deposits, a blind test was conducted using a suite of epidote-chlorite ± pyrite-altered Laramide volcaniclastic rocks and Proterozoic dolerites collected from the propylitic halo, with samples taken from two domains located to the north and south and above the Resolution ore zone. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) data of epidote provided indications of deposit fertility and proximity. Competition for chalcophile elements (As, Sb, Pb) between coexisting pyrite and epidote grains led to a subdued As-Sb fertility response in epidote, consistent with epidote collected between 0.7 and 1.5 km from the center of a large porphyry deposit. Temperature-sensitive trace elements in chlorite provided coherent spatial zonation patterns, implying a heat source centered at depth between the two sample clusters, and application of chlorite proximitor calculations based on LA-ICP-MS analyses provided a precisely defined drill target in this location in three dimensions. Drilling of this target would have resulted in the discovery of Resolution, confirming that epidote and chlorite mineral chemistry can potentially add value to porphyry exploration under cover.

ICDP workshop on the Lake Tanganyika Scientific Drilling Project: a late Miocene–present record of climate, rifting, and ecosystem evolution from the world's oldest tropical lake

Abstract. The Neogene and Quaternary are characterized by enormous changes in global climate and environments, including global cooling and the establishment of northern high-latitude glaciers. These changes reshaped global ecosystems, including the emergence of tropical dry forests and savannahs that are found in Africa today, which in turn may have influenced the evolution of humans and their ancestors. However, despite decades of research we lack long, continuous, well-resolved records of tropical climate, ecosystem changes, and surface processes necessary to understand their interactions and influences on evolutionary processes. Lake Tanganyika, Africa, contains the most continuous, long continental climate record from the mid-Miocene (∼10 Ma) to the present anywhere in the tropics and has long been recognized as a top-priority site for scientific drilling. The lake is surrounded by the Miombo woodlands, part of the largest dry tropical biome on Earth. Lake Tanganyika also harbors incredibly diverse endemic biota and an entirely unexplored deep microbial biosphere, and it provides textbook examples of rift segmentation, fault behavior, and associated surface processes. To evaluate the interdisciplinary scientific opportunities that an ICDP drilling program at Lake Tanganyika could offer, more than 70 scientists representing 12 countries and a variety of scientific disciplines met in Dar es Salaam, Tanzania, in June 2019. The team developed key research objectives in basin evolution, source-to-sink sedimentology, organismal evolution, geomicrobiology, paleoclimatology, paleolimnology, terrestrial paleoecology, paleoanthropology, and geochronology to be addressed through scientific drilling on Lake Tanganyika. They also identified drilling targets and strategies, logistical challenges, and education and capacity building programs to be carried out through the project. Participants concluded that a drilling program at Lake Tanganyika would produce the first continuous Miocene–present record from the tropics, transforming our understanding of global environmental change, the environmental context of human origins in Africa, and providing a detailed window into the dynamics, tempo and mode of biological diversification and adaptive radiations.

The influence of Totten Glacier on the Late Cenozoic sedimentary record

AbstractAnalysis of multichannel seismic profiles collected on the continental rise off the Sabrina Coast, East Antarctica, has allowed the determination of the acoustic features that are indicative of major evolution steps of the East Antarctic Ice Sheet (EAIS) and highlights the role of meltwater that originated from Totten Glacier in shaping the margin architecture. The arrival of marine-terminating glaciers into the coastal region was recorded by an enhanced sediment input on the continental rise and the nucleation of channel-levees. Downslope sedimentary processes were dominant throughout the Late Cenozoic, testifying to the progressive growth of a highly dynamic, temperate ice sheet on the continent. The last evolutionary step marks the transition to when a full polar glacial regime occurred. The development of a prograding wedge with steeply dipping foresets on the continental shelf and slope exemplifies sedimentation at this time. Other sub-sea-floor observations indicate that downslope fluxes, triggered by glacial meltwater, were still able to deeply erode and deliver sediments to the rise area. This study's findings have led to the identification of expanded and well-preserved sedimentary successions, which we suggest should be considered as priority targets for future International Ocean Discovery Program deep drilling due to the sensitivity of the ice sheet in this area.

Play Fairway analysis of geothermal resources across the State of Hawai‘i: 4. Updates with new groundwater chemistry, subsurface stress analysis, and focused geophysical surveys

This paper is the fourth in a series on a play fairway analysis of geothermal resources across the State of Hawai‘i. Here we describe recent exploration activities that include groundwater sampling in ten locations statewide, as well as geophysical surveys on Lāna‘i, across the SW rift of Haleakalā Volcano (Maui), and surrounding Mauna Kea Volcano (Hawai‘i Island). We derive a first-order method for computing topographic stress using Green’s functions, finding that topography can induce appreciable crustal stress. We develop a new method for incorporating depth information about resistivity, density, and topographic stresses into our previously published equations to calculate resource probability and confidence. We incorporate newly collected and modeled data into our calculations to update statewide maps of probability and confidence. Lāna‘i Island and southeast Mauna Kea are identified as the top targets for exploratory drilling. The east rift of Haleakalā Volcano, the southern-most region of Mauna Loa’s SW rift (Hawai‘i Island), and central Kauai are identified as targets for geophysical surveying.

Seismic fine imaging and its significance for natural gas hydrate exploration in the Shenhu Test Area, South China Sea

ABSTRACT Shenhu area in South China Sea includes extensive collapse and diapir structures, forming high-angle faults and vertical fracture system, which functions as a fluid migration channel for gas hydrate formation. In order to improve the imaging precision of natural gas hydrate in this area, especially for fault and fracture structures, the present work propose a velocity stitching technique that accelerates effectively the convergence of the shallow seafloor, indicating seafloor horizon interpretation and the initial interval velocity for model building. In the depth domain, pre-stack depth migration and residual curvature are built into the model based on high-precision grid-tomography velocity inversion, after several rounds of tomographic iterations, as the residual velocity field converges gradually. Test results of the Shenhu area show that the imaging precision of the fault zone is obviously improved, the fracture structures appear more clearly, the wave group characteristics significantly change for the better and the signal-to-noise ratio and resolution are improved. These improvements provide the necessary basis for the new reservoir model and field drilling risk tips, help optimize the favorable drilling target, and are crucial for the natural gas resource potential evaluation.

Advances in ICP-MS technology and the application of multi-element geochemistry to exploration

There have been several advances in inductively coupled plasma-mass spectrometer (ICP-MS) analytical technologies in the last decade. Collision/reaction cell ICP-MS and triple quadrupole ICP-MS techniques can produce lower detection limits for select elements that experience interferences with a standard quadrupole (e.g. Se and As). Triple quadrupole ICP-MS, in particular, can eliminate virtually all polyatomic or isobaric interferences for highly accurate measurements of some element isotopes systematics that are of great interest in mineral exploration, namely Pb/Pb. Laser ablation ICP-MS has become more popular as an effective analytical tool to measure mineral grain trace elements, which could assist in vectoring to mineralization or exploration drill targets. The ablation of a spot on a Li-borate fused glass disk paired with XRF analysis has also gained popularity as an alternative to total whole rock characterization packages that employ several separate digestions and analytical methods. While there have been several advancements in ICP-MS technologies in exploration geochemistry, they have not been widely accepted or implemented. This slow adaptation could be due to the extended recession in the mining industry between 2012 and 2017. It is also possible that standard ICP-MS data (i.e. no collision/reaction cell) is still fit for purpose. This stands in stark contrast to implementation of ICP-MS in the previous decade (1997–2007), which was transformational for the industry. Consideration of all elements from large multi-element ICP-MS analytical suites for mineral exploration can be an extremely powerful tool in the exploration toolkit. The discovery of the White Gold District, Yukon, is a prime example of how the utilization of soil geochemical data, when plotted spatially, can vector to gold mineralization. The presence of Au + As + Sb soil anomalies were key to delineating mineralization, especially when accompanied by publicly available geological, geographical and geophysical data. Additionally, elements and element ratios not typically considered in Au exploration, including Ni and U, were utilized to determine the lithological and structural controls on mineralization. The availability of multi-element ICP-MS data was also useful in the discovery of the Cascadero Copper Taron Caesium deposit. Ore-grade Cs was discovered only because Cs was included in the multi-element ICP-MS exploration geochemistry suite. Before the availability of ICP-MS, it is unlikely that this deposit would have been discovered. Thematic collection: This article is part of the Exploration 17 collection available at: https://www.lyellcollection.org/cc/exploration-17

Which anomaly should I drill? Using spatial statistics to inform exploration in covered IOCG terranes

SummaryThis contribution presents a method for efficiently classifying geophysical anomalies and identifying regions and features that share characteristics of many known iron-oxide-copper-gold (IOCG) deposits of the Gawler Craton, and can therefore be used in drill target prioritization. Residual Bouguer gravity and reduced-to-pole total magnetic intensity grids over the Gawler Craton were transformed, generating polygon datasets representing populations of locally anomalous gravity and magnetic intensity. Taken as simple anomaly polygons, there are a very large number of features across the Gawler Craton (>39,000 TMI and >10,000 gravity). Superimposing mineral deposits over these features shows a clear spatial correlation between IOCG deposits and occurrences, and anomalies (>90% of deposits within 1,000 m of an anomaly), but leaves thousands of anomalies of varying magnitudes that cannot all be related to IOCG mineralization. Eliminating TMI and gravity anomalies with a separation of more than 1,000 m reduced the search space to ~20,000 TMI features and ~8,500 gravity features. Limiting the search to a statistically derived gravity threshold ≥0.4 mGal gravity anomalies, the exploration space is reduced to 798 gravity features with coincident TMI features within the Olympic Copper-Gold Province. The Anselin Local Morans I method was used to delineate geographic regions based upon spatial clustering of high magnitude anomalies. The spatial distribution and clustering characteristics of the gravity anomalies provide additional information and can be related to differing basement geology and deposit style. Terranes where lithologies and Cu-Au occurrences are commonly magnetite-rich show clustered high-magnitude gravity anomalies, and correlated spatially with the Mount Woods and Moonta domains within the eastern Gawler Craton. Importantly, it was found that the central, and currently most endowed, the Olympic Domain, was distinct in that it was dominated by spatial outliers (discrete high-magnitude density features).These results could be used as a starting point in developing IOCG exploration strategies, due to the high number of additional untested, spatially coincident gravity and magnetic anomalies that warrant further investigation.

Passive seismic HVSR surveying for groundwater exploration at the Chilalo Graphite Project, Tanzania

Passive seismic HVSR surveying is increasingly being used for investigating the thickness of soft sedimentary cover deposits sitting over hard and fresh bedrock, and for direct drill targeting of p...

The value of VSP data through early phases of field appraisal and development: A modeling and acquisition case study in the Gulf of Mexico

The Gulf of Mexico is a rich hydrocarbon province that contains a diversity of petroleum systems play types. Often, identifying drilling targets can be challenging when solely using surface seismic data, particularly in areas with complex salt structures in the overburden. In this paper, we present a vertical seismic profile (VSP) modeling and acquisition case study for an oil field located in a subsalt, deepwater, ultrahigh-pressure high-temperature environment. Our objective was to model the subsurface to guide the acquisition of VSP data during the early phases of exploration and appraisal drilling. In the first exploration well, a salt-proximity VSP designed in a walkaway configuration was carried out to help better define the geometry of a salt overhang and verify anisotropy parameters, helping to reduce a critical uncertainty for imaging the subsalt structure across a large segment within our field area. In the first appraisal well, a zero-offset VSP was collected to establish a direct well tie and further calibrate our velocity model. In the second appraisal well, we utilized walkaway VSP data to form a high-frequency stratigraphic image between the two appraisal wellbores. These data were used to generate an enhanced image of the reservoir section that revealed subtle stratigraphic boundaries, another key subsurface uncertainty. Finally, we modeled both ambitious and conservative 3D VSP acquisition designs to understand the imaging area achieved through a 3D acquisition and undertook an assessment to understand the impact of PP and PS imaging for reservoir characterization. We conclude that VSP data are valuable tools in the early phases of field appraisal and development, and we demonstrate the business value of VSPs to optimize development drilling locations in our study area.

Las Pailas geothermal field - Central America case study: Deciphering a volcanic geothermal play type through the combination of optimized geophysical exploration methods and classic geological conceptual models of volcano-tectonic systems

Sustainable exploitation strategies of high-enthalpy geothermal reservoirs in a volcanic geothermal play type require an accurate understanding of key geological structures such as faults, cap rock and caldera boundaries. Of same importance is the recognition of possible magmatic body intrusions and their morphology, whether they are tabular like dikes, layered like sills or domes. The relative value of those magmatic bodies, their age, shape and location rely on the role they play as possible local heat sources, hydraulic barriers between reservoir compartments, and their far-reaching effect on the geochemistry and dynamics of fluids. Obtaining detailed knowledge and a more complete understanding at the early stages of exploration through integrated geological, geophysical and geochemical methods is essential to determine promising geothermal drilling targets for optimized production/re-injection schemes and for the development of adequate exploitation programs. Valuable, extensive geophysical data gathered at Las Pailas high-enthalpy geothermal field at northwestern Costa Rica combined with detailed understanding of the geological structures in the underground may represent a sound basis for an in-depth geoscientific discussion on this topic. Currently, the German cooperation for the identification of geothermal resources in Central America, implemented by the Federal Institute for Geosciences and Natural Resources (BGR), supports an international and interdisciplinary effort, driven by the Instituto Costarricense de Electricidad (ICE) with different international and national research institutions, including the Leibniz Institute for Applied Geophysics (LIAG). The discussions and joint studies refer to the optimized utilization of geophysical and geological methods for geothermal exploration in the Central American region, using the example of Las Pailas Geothermal Field. The results should contribute to a better understanding of the most appropriate geothermal exploration concepts for complex volcanic field settings in Central America.

Great Mining Camps of Canada 7. The Bathurst Mining Camp, New Brunswick, Part 1: Geology and Exploration History

The Bathurst Mining Camp of northern New Brunswick is approximately 3800 km2 in area, encompassed by a circle of radius 35 km. It is known worldwide for its volcanogenic massive sulphide deposits, especially for the Brunswick No. 12 Mine, which was in production from 1964 to 2013. The camp was born in October of 1952, with the discovery of the Brunswick No. 6 deposit, and this sparked a staking rush with more hectares claimed in the province than at any time since. In 1952, little was known about the geology of the Bathurst Mining Camp or the depositional settings of its mineral deposits, because access was poor and the area was largely forest covered. We have learned a lot since that time. The camp was glaciated during the last ice age and various ice-flow directions are reflected on the physiographic map of the area. Despite abundant glacial deposits, we now know that the camp comprises several groups of Ordovician predominantly volcanic rocks, belonging to the Dunnage Zone, which overlie older sedimentary rocks belonging to the Gander Zone. The volcanic rocks formed during rifting of a submarine volcanic arc on the continental margin of Ganderia, ultimately leading to the formation of a Sea of Japan-style basin that is referred to as the Tetagouche-Exploits back-arc basin. The massive sulphide deposits are mostly associated with early-stage, felsic volcanic rocks and formed during the Middle Ordovician upon or near the sea floor by precipitation from metalliferous fluids escaping from submarine hot springs. The history of mineral exploration in the Bathurst Mining Camp can be divided into six periods: a) pre-1952, b) 1952-1958, c) 1959-1973, d) 1974-1988, and e) 1989-2000, over which time 45 massive sulphide deposits were discovered. Prior to 1952, only one deposit was known, but the efforts of three men, Patrick (Paddy) W. Meahan, Dr. William J. Wright, and Dr. Graham S. MacKenzie, focused attention on the mineral potential of northern New Brunswick, which led to the discovery of the Brunswick No. 6 deposit in October 1952. In the 1950s, 29 deposits were discovered, largely resulting from the application of airborne surveys, followed by ground geophysical methods. From 1959 to 1973, six deposits were discovered, mostly satellite bodies to known deposits. From 1974 to 1988, five deposits were found, largely because of the application of new low-cost analytical and geophysical techniques. From 1989 to 2000, four more deposits were discovered; three were deep drilling targets but one was at surface.

Assessing shale mineral composition: From lab to seismic scale

Shales have always been a difficult target for drilling of deviated and horizontal wells. In the presence of azimuthal stress fields, inclined boreholes in smectite-rich shales exhibit geomechanical instabilities and can result in borehole failure. The complex geology of the major gas fields in the Northern Carnarvon Basin on the North West Shelf of Australia makes it necessary to drill deviated wells through the smectite-rich shale seal extending more than 1 km in thickness. Predicting the mineralogical composition of shales in the area is therefore crucial for the success of drilling operations related to hydrocarbon exploration and production. Here we introduce a novel workflow that combines seismic data, well logs, and laboratory measurements to rapidly infer smectite content in shale. The workflow is applied to the Duyfken 3D seismic survey in the central part of the Northern Carnarvon Basin. The results of our quantitative interpretation are verified against the laboratory X-ray diffraction measurements from the test well that was not used for interpretation, and they match the test data well within the determined uncertainty bounds.

Value-add and safe drilling from 4D AVO evaluation in the Enfield oil field, North-West Shelf, Australia

The Enfield oil field, on the Australia?s Greater North- West Shelf, started production in July 2006, and has already seen significant benefit from 4D seismic monitoring. The technique is particularly applicable in Enfield due to faulting and baffles within the reservoir, the need for multiple water injection wells, and the presence of a gas cap. Full-field monitor surveys in February 2007 and December 2008 have made major contributions to reservoir management and identification of infill drilling opportunities. This paper highlights the 2009 development drilling in the field?s Sliver Block, where 4D not only supported the business case for a new production and water injection well, but also provided important information to enhance safe and efficient drilling. 4D AVO analysis involved extraction of changes over various source-receiver offset ranges, driven by a rock property model in which nears and mids tend to show pressure changes, while fars and ultra-fars show saturation changes. A clear 4D AVO signal on the early monitor showed the drilling target area to be pressured up by a distant injector, contrary to pre-4D expectations. The later monitor confirmed this, and also showed the oil target intact ? with no significant water sweep. Using 4D, significant overpressure in the target was predicted. Accordingly, casing schemes for the wells were redesigned to enable safe reservoir entry; the distant water injector was shut in prior to drilling; and appropriate heavy brine was ordered for completion operations. Actual pressures fell within the predicted range, and a safe and successful drilling campaign was achieved.

Petroleum prospect analysis and new gas horizon detection at Fenchuganj Gas Field in the Surma Basin, Bangladesh: An application of sequence stratigraphic concept

Abstract The biggest question in the present gas crisis is where to find gas in the onshore of Bangladesh. The exploration strategies so far taken over the Surma Basin give importance only to the structural traps (fault-bounded anticlines). Already most of the anticlinal structures have been drilled and now they are at nearly matured stage. Therefore, most sustainable solutions are revising all the gas fields with sequence stratigraphic concept and find out the hidden possibilities of stratigraphic traps that are being still neglected. In this paper, interpretation of available logs and seismic has revealed the sequence stratigraphic concept of the reservoirs as well as new exploration prospect in the portion of Fenchuganj Gas field. The study reveals seven prospective reservoir zones, PR-1 to PR-7 from older to younger in studied area. Prospective reservoir PR-1 and PR-4 are belong to highstand system tract whereas PR-2, PR-3 and PR-5 are in the lowstand system tract. Upper two reservoirs PR-6 and PR-7 are located within the sand facies of transgressive system tract. Analysis of seismic attribute and log response has yield a prospective future drilling target in the erosional remnant of a highstand system tract truncated against lowstand-incised valley and capped by transgressive shale. Based on the seismic amplitude (bright spot), two exploration prospects were also identified in the stratigraphic traps located on the flank of the Fenchuganj structure. One is highstand sand truncated against shale-filled valley and the other one is lowstand channel sand sealed by transgressive shale, which demand further investigation. Thus, this approach provides new insights for local and international oil companies that there are huge possibilities of finding stratigraphic traps in the tidal deposits of regressive shelves that are yet to be well documented.

Structure and fracture-cavity identification of epimetamorphic volcanic-sedimentary rock basement reservoir: a case study from central Hailar Basin, China

Taking the epimetamorphic volcanic-sedimentary complex basement in Beier Depression, Hailar Basin, China, as an example, the lithology, diagenesis, reservoir characteristics, and vertical zoning structure division are studied by using core, thin sections, cathodoluminescence, SEM, LSCM, well logging, FMI, diplog, and 3D seismic data. The reservoirs including fractures and cavities are identified and predicted separately under the control of vertical zoning structure, by well logging response, seismic reflection features, and multiseismic attributes. The results show that the assemblage of fine siltstone, tuffaceous sandstone, and tuff is the best lithology assemblage for reservoir development. The basement reservoir structure is divided into four zones, and zone II developing both fractures and pores has the best reservoir quality, followed by zone III having fractures dominated. Fracture and pore-cavity reservoirs have decreasing resistivity, density, and other features in conventional well log, and pore-cavity reservoirs have relatively high amplitude and bead or lenticular-shaped seismic reflection. The seismic attributes of curvature, coherence, and amplitude extracted under the control of specific zonation are effective reservoir prediction methods. Reservoir distribution including fracture and pore-cavity is controlled by the palaeogeomorphology of basement buried hill and fault activity and property. For the buried hills with high palaeogeomorphology and long-term structural activity controlled by main faults, developing high-quality reservoirs of fractures as well as pores, are the optimal targets for basement drilling, in the condition of effective hydrocarbon migration path.

Logging-based identification and evaluation of karst fractures in the eastern Right Bank of the Amu Darya River, Turkmenistan

Carbonate gas reservoir in the eastern area on the Right Bank of the Amu Darya River, Turkmenistan, are of low-porosity and with developed fractures. In this area, fractures control reservoir properties and natural gas production, and karst fractures are the most important kind of fractures, so their identification and evaluation are quite necessary. In this paper, fracture types were identified and their occurrence was extracted by using conventional logging and image logging data after core calibration. Then, the distribution characteristics of karst fractures and their controlling effect on reservoirs were studied according to the identification results. And the following research results were obtained. First, karst fractures are mainly of high angle with the characteristic of mono system and the interactive relation of genesis. Second, they are mainly distributed in the upper XVhp layer of Callovian–Oxford Stage and the lower XVa2–XVI layer. Third, they are the main effective fractures in this area. The dissolved pores are connected effectively through the expanded karst fractures by dissolution, and consequently reservoirs of high porosity and permeability are formed and they are the important reservoir type and high-yield gas reservoir in this area. Fourth, karst fractures are related to high-yield wells and high-yield layers in this area, and they also control the distribution of high-yield reservoirs in the lower part of Callovian–Oxford Stage. It is concluded that by virtue of imaging logging and conventional logging data, karst fractures, unfilled fractures, semi-filled fractures and fully filled fractures can be identified and evaluated better. Furthermore, the identification and evaluation of karst fractures deepen the understanding on fractured reservoirs in this area, improve the reservoir evaluation effect, and provide the basis for the target horizon and azimuth optimization of horizontal wells and highly deviated wells. And it is also indicated that the reservoirs with developed karst fractures are the subsequent important drilling targets.

Laboratory Confirmation of Non-Linear Electrical Effects in Mineralised Rocks

Induced Polarisation (IP) and Transient Electromagnetism (TEM) are among the most widely used ground electrical geophysics methods in Australia, being specialised in detecting conductive and chargeable targets such as sulphide deposits. A key challenge of IP T often a chargeable body is not a sulphide deposit but a graphite-rich formation of black shale or clays. As these shale deposits are undesirable targets, distinguishing by physical methods such as drilling is exhaustive on exploration resources. Graphite-rich shales, which plague induced polarisation surveys, cannot be distinguished from sulphide mineralisatio by existing electrical methods. The effect of disseminated sulphide grains acting as a diode in the presence of two electrical signals of nonharmonically related frequencies was originally studied in the 1970s. There is some evidence that shales produce a strictly linear response. This contrasts to the non-linear response of sulphide-rich rocks which generates additional signals in the frequency domain. A laboratory-based reinvestigation into non-linear properties of sulphides has been undertaken with a view towards field application. Variable frequencies and signal strengths were used to validate the method, based initially on the processes described in White (1974). The intermodulation mixing terms produced as a response by sulphide mineralised deposits in this laboratory-based investigation may allow for electrical distinction of sulphides from non-mineralised shales and clays. The application of a direct current (DC) bias to either signal increased the detectability of non-linear responses, allowing for a lower current density threshold for measurement. The magnitude of the non-linear signal detected provides a basis for field testing of this previously unutilised electrical property, with the eventual aim to providing a method for greatly reducing the number of drill targets barren of mineralisation.

Identification of shallow geohazard channels based on discontinuity seismic attributes in the South Caspian Sea

Identification of geomorphological features in seismic data is a key element of seismic interpretation. Channels in the shallow subsurface are potential geohazards. At deeper levels, they can be the actual targets for (horizontal) drilling. Either way, it is important to optimally delineate these features prior to well location positioning and drilling. We have studied a poststack 3D seismic data from the South Caspian Sea featuring shallow channels that are considered potential geohazards for drilling operations. In the first step, we attenuate the acquisition footprints along the inline direction using a geostatistics approach based on factorial kriging. To better visualize channels in the presence of stratigraphic dips, we create a dense set of horizons using an inversion-based flattening algorithm. In the next step, we compare various discontinuity attributes such as semblance, similarity, curvature, and the relatively new attribute based on the multiscale and multidirectional shearlet transformation to determine which one best images our features of interest. Curvature attributes clearly image channel levies (positive curvature) and channel centers (negative curvature). Lateral changes in the curvature magnitude infer sedimentation from the north. Similarity, semblance, and shearlet transform attributes also successfully delineate channel edges, but these attributes do not contain additional geologic information. In the final step, we qualitatively analyze channel thickness variations by the red-green-blue blending of three spectral components based on short window Fourier transforms.

The Resource Estimation and Geologic Risk Assessment for the Southern Structure Belt in Block 69, Yemen

Block 69 in Yemen is characterized by several poor oil forming conditions, such as being low in trap confirmation and poor reservoir quality etc.. Though three wells have been drilled, no commercial hydrocarbon discovery has been made, showing the great difficulties for oil and gas exploration in the block. The author, on the basis of analyzing the oil and gas accumulation conditions, has performed trap conformation in the block and carried out trap resources estimation and geologic risk assessment, thus suggested that the Prospect-1 trap is the most favorable drilling target in the future.

A look back: The drilling campaign of the Curiosity rover during the Mars Science Laboratory's Prime Mission

The Mars Science Laboratory (MSL) rover, Curiosity, completed its first Martian year, 669 sols (687 Earth days), of operation on June 24, 2014. During that time the rover successfully drilled three full depth drill holes into the Martian surface and analyzed the recovered material using onboard instruments, giving us new insights into the potential habitability of ancient Mars. These drill targets are known as 'John Klein' (Sol 182) and 'Cumberland' (Sol 279), which lie in the mudstones of the Yellowknife Bay formation, and 'Windjana' (Sol 621), which lies in the sandstones of the Kimberley formation. In this paper we will discuss what was necessary to procure these samples, including: 1) an overview of the sampling hardware; 2) the steps taken to ensure sampling hardware is safe when drilling into a target (i.e., evaluation of rock type, rover stability, prior testbed experience, etc.); and 3) the drilling parameters used to acquire these samples. We will also describe each target individually and discuss why each sample was desired, the triage steps taken to ensure it could be safely acquired, and the telemetry obtained for each. Finally, we will present scientific highlights obtained from each site utilizing MSL's onboard instrumentation (SAM & CheMin), results enabled by the drills ability to excavate sample at depth and transfer it to these instruments.