Hydrocarbon Indicators Research Articles

The Mundeck Salt Unit: A Review of Aptian Depositional Context and Hydrocarbon Potential in the Kribi-Campo Sub-Basin (South Cameroon Atlantic Basin)

The Kribi-Campo sub-basin, located in the Gulf of Guinea, constitutes the southeastern segment of the Cameroon Atlantic Margin. Drilling in the Aptian salt unit revealed a sparse hydrocarbon presence, contrasting with modest finds in its counterparts like the Ezanga Salt in Gabon and the Rio Muni Salt in Equatorial Guinea. This discrepancy prompted a reassessment of the depositional context and hydrocarbon potential of the Mundeck salt unit. By integrating 2D seismic reflection and borehole data analysis, this study established the structural and stratigraphic framework of the area, emphasizing the salt unit’s significance. Borehole data indicate a localized salt unit offshore Kribi, with seismic reflection data revealing distinct forms of diapir and pillow. This salt unit displays a substantial lateral extent with thicknesses ranging from 4000 m to 6000 m. The depositional context is linked to the following two major geological events: a significant sea-level drop due to margin uplift during the Aptian and thermodynamic processes driven by transfer faults related to mid-oceanic ridge formation. These events were crucial in forming and evolving the Mundeck Salt. Regarding hydrocarbon prospects, this study identifies the unit as being associated with potential petroleum plays, supported by direct hydrocarbon indicators and fault-related structures. The findings suggest that untapped hydrocarbon resources may still exist, underscoring the need for further exploration and analysis.

Integrated approach to determining the identity of the pollution of adjacent territories with oil products

The methodology of arranging laboratory studies of oil-contaminated soils, soils and bottom sediments to determine the source and composition of hydrocarbon contamination is described. The complex approach to laboratory analysis of samples of oil-contaminated soils, soils and bottom sediments is proposed, which allows a highly reliable identification of the potential source of contamination and/or making conclusions about the identity of the contamination of adjacent territories. The proposed complex of analytical methods includes infrared spectrometry, gas chromatography with mass-selective detection, thin-layer chromatography with flame ionization detection and elemental analysis (C, H, N, S, O). Application of the proposed integrated approach allows highly reliable determination of the nature of oil contamination of soils, estimation of the total gross content of oil products and their hydrocarbon composition, and identification of the potential source of pollution. Possible errors in the interpretation of the results of determining the identity of contamination of territories and the importance of using an integrated approach in drawing conclusions about the source (culprit) of pollution are shown using real soil samples taken from oil-contaminated objects and adjacent territories. The importance of taking into account the losses of volatile oil products at the stage of sample preparation for soil contamination with light oil fractions is demonstrated. The use of standard methods of sample preparation (drying of the samples under study) leads to errors in assessing the level of contamination of territories with volatile hydrocarbons and in the choice of methods of remediation of contaminated territories. To minimize losses of volatile hydrocarbons (petrol and naphtha fractions) at the stage of soil sampling and transportation the use of sorbent is proposed. Addition of a sorbent to the soil contaminated with oil products can reduce losses of volatile hydrocarbons by 15 – 20% in the analyzed samples. Application of the developed complex approach makes it possible to determine the features of the individual hydrocarbon composition, group and elemental composition of petroleum products and identify hydrocarbon indicators (markers) inherent only to a certain type of petroleum product.

Characterization of Carbonate Reservoir Potential in Salawati Basin, West Papua: Analysis of Seismic Direct Hydrocarbon Indicator (DHI), Seismic Attributes, and Seismic Spectrum Decomposition

Carbonate reservoir of Kais Formation in Salawati Basin, West Papua, is the most famous oil and gas reservoir in the eastern part of Indonesian Archipelago since 1970’s. Nowadays, new prospects in this area are more challenging and most relevant near the infrastructure of previous oil and gas fields. In this study, a relatively new seismic dataset was investigated to figure out new prospects in carbonate reservoir rocks in the area of interest. In this preliminary study, where seismic data are not supported by well data, direct hydrocarbon indicator (DHI), seismic attribute, and spectral decomposition (CWT: continuous wavelet transform) allow the authors to characterize the reservoir geometry and to predict pore fluids within the reservoir rocks. The reservoir geometry of carbonate reef of Kais Formation (C1) was identified by seismic reflectors with high amplitude contrast at the top C1. The hydrocarbon indicator was predicted by DHI where dim spots, flat spots, and polarity reversals are indicative of hydrocarbon prospects. From the attribute analysis, the attribute instantaneous amplitude detected the top carbonate C1, whereas pore fluids were predicted from high sweetness attribute. In addition, spectral decomposition CWT method confirms the top C1, identified as saturated rock by the frequency of 10 Hz, 20 Hz, and 30 Hz. Based on a seismic study in the researched area, the target zone is expected to be a very promising hydrocarbon reservoir, specifically a carbonate reservoir. As a result, the preferred well-test location is in a region with access to the Kais Formation limestone reef layer. This study can assist in reservoir characterization, especially in areas with limited well control.

The evolution of clay mineral and its indication of hydrocarbons under overpressure: An example from the shale of the Qingshankou Formation in the Gulong Sag

The enrichment and development of shale oil are significantly influenced by the evolution of clay minerals. In this paper, the mineralogy and clay mineral crystallinity of shale samples from Wells X1, X2 and X3 in the Gulong Sag are characterized by X-ray diffraction analysis (XRD) and field emission scanning electron microscopy (FE-SEM). Geochemical parameters, including total organic carbon (TOC) and rock-eval pyrolysis, were also evaluated. The results reveal that illite in the shale primarily exists in the matrix, originating mainly from the transformation of smectite and I/S mixed layer. Chlorite in pores is predominantly formed through fluid precipitation and crystallization. The study area exhibits abnormal evolution of illite and I/S mixed layers, as well as the phenomenon of rapid chlorite growth under overpressure condition. The abnormal evolution of illite and I/S mixed layer may attribute to the inhibition of the conversion reaction from I/S mixed layer to illite. Chlorite's rapid growth occurs through the nucleation mechanism. Furthermore, through the analysis of clay and organic matter correlation, coupled with overpressure and hydrocarbon-rich section considerations, it is observed that chlorite may play a significant role in the storage and generation of S1. This study contributes to a better understanding of the relationship between clay mineral evolution and shale reservoir overpressure, offering valuable insights for the accurate assessment of shale oil.

The observation of atmospheric HONO by wet-rotating-denuder ion chromatograph in a coastal city: Performance and influencing factors

Due to the significance of atmospheric HONO as a reservoir for radicals and the presence of substantial unknown sources of HONO, there is a pressing need for accurate and consistent measurement of its concentration. In this study, we compared the measurements obtained from the monitor for aerosols and gases in ambient air (MARGA) based on wet chemical method with those from the incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) based on optical method to assess the suitability of the MARGA instrument for accurate HONO detection. The diurnal patterns obtained by the two instruments are similar, with peaks at 8 a.m. and lows at 5 p.m. Over the course of the observation period, it was often observed that HONO concentrations recorded by the MARGA instrument consistently exceeded those obtained through the IBBCEAS technique, accounting for approximately 91.33% of the total observation time. Throughout the entire observation period, the R2 value between the two instruments was 0.49, indicating relatively good correlation. However, with a slope of only 0.27, it suggests poor agreement between the two instruments. Furthermore, the R2 and slopes between the two instruments vary with the seasons and day-night. The larger the quartile values of NO2, NH3, and BC, the greater the slopes of both MARGA and IBBCEAS instruments, and the higher the concentrations of NO2, NH3, and BC (indicator of semivolatile oxidizable hydrocarbons), the greater the differences between the two instruments, all indicating that NH3 may promote the reaction of NO2 with semivolatile oxidizable hydrocarbons to produce HONO. The O3 with its strong oxidizing properties may cause underestimation in the MARGA instrument by oxidizing NO2− to NO3− in the absorbing solution. It is challenging to derive a universal correction formula due to the interference of various chemical substances. Hence, MARGA should not be used for HONO research in the future.

A comparative study on hydrocarbon detection using cepstrum–based methods

Amplitude anomaly caused by a high–frequency component is attenuated more rapidly than a low–frequency component for a seismic trace in sediments susceptible to gas influence and is always used as a direct indicator of hydrocarbons. Recently, cepstrum–based hydrocarbon detection methods have become an important exploration pathway for detecting amplitude anomalies in the gas–bearing formation more sensitively and accurately. In this study, we compared three cepstrum–based hydrocarbon detection methods. We compared their fluid identification abilities in gas reservoirs and the noise robustness. They were further compared with the traditional absorption coefficient estimation method. We also indicate how the choice of the selection of the sliding–window length influences the performance of the three cepstrum–based hydrocarbon detection methods. Model test results and real data applications show that for thick gas reservoirs, the hydrocarbon detection methods using the Berthil–based cepstrum and the wavelet–based cepstrum can better discriminate the upper and lower interfaces than the hydrocarbon detection method using the Fourier–based cepstrum. For thin gas reservoirs, the hydrocarbon detection method using the wavelet–based cepstrum can identify the lower interface of the gas–bearing reservoir more obviously than the upper interface. The hydrocarbon detection method using the Berthil cepstrum cannot identify the upper and lower interfaces of the gas–bearing reservoir, but it shows higher temporal and spatial resolution compared to the hydrocarbon detection method using the Fourier–based cepstrum. For noise robustness, the hydrocarbon detection method using the wavelet–based cepstrum has the strongest noise robustness property, and the hydrocarbon detection method using the Fourier–based cepstrum is the most sensitive method to the noise. For time–consumption, the hydrocarbon detection method using the wavelet–based cepstrum is the most time–consuming, and the hydrocarbon detection method using the Fourier–based cepstrum is the fastest.

Structural and Stratigraphic Interpretations for Mishrif Formation in Kumait Oil Field, Using Seismic Reflection Data, Southern-Eastern Iraq

The Kumait oil field is located in the Maysan Governorate southeastern Iraq, which was studied and interpreted by using 2D and 3D seismic data provided by the Oil Exploration Company using Petrel software. The study concerned the Mishrif Formation belongs to the Cretaceous Age. The reflector was detected based on synthetic seismograms and well logs for Kt-1 well. Structural maps (two-way time, velocity, and depth) were derived from seismic reflection interpretations to show several structural features, such as four isolated irregular enclosures representing the Kumait structure plunging NW-SE and demonstrating that the Kumait oil field is influenced by the Najd fault system trending NW-SE. The stratigraphic interpretation used the variance attribute to delineate the edge of the fault, which extended from the Mishrif Formation with a depth of 3090m and used the Direct Hydrocarbon Indicators (DHI) to identify the stratigraphic features in the research region and the extraction of seismic attributes. The applied seismic attributes, such as the instantaneous phase, show dim spots, flat spots, and mounds and is followed by down-lap; the instantaneous frequency, which offers low-frequency areas indicating a high probability of hydrocarbon accumulation; and the RMS amplitude, which shows high amplitude in the seismic data that conforms to the structure and confirms the presence of hydrocarbon.

Integrated analysis of wireline logs analysis, seismic interpretation, and machine learning for reservoir characterisation: Insights from the late Eocene McKee Formation, onshore Taranaki Basin, New Zealand

This study aims to integrate seismic and well data for re-assessment and delineating the geological and petrophysical characteristics of the Late Eocene McKee Formation. Despite the McKee Formation being a hydrocarbon-producing field, there have been no previous integrated studies conducted to characterize its deposits in the Taranaki Basin. To execute these tasks, the process involves the interpretation of seismic data, wireline analysis, and 3D porosity volume prediction using multi-layered feed-forward neural network models. The seismic data was interpreted and found to contain low displacement faults due to intricate geometric complexities, the contour map that was generated shows lateral extension and thickness variation, and the region of direct hydrocarbon indicators was detected using the root-mean-square. Additionally, the seismic inversion provides a comprehensive understanding of the acoustic impedance variations from low to high value, which signifies the presence of mudstone clasts content. Furthermore, in the wireline log analysis, the reservoir was found to be a Silici-clastic and carbonate field owing to the presence of dolomite, calcite, and quartz. After applying cutoffs, petrophysical parameters were evaluated. The estimated values for effective porosity, reservoir thickness, shale volume, and water and hydrocarbon saturation were 15.04 % to 17.29 %, 85.44 m to 122.41 m, 8.99 to 14.87 % and 12.97–27.10 %, and 72.9 % to 87.03 %, respectively. The outcome of this extensive research aids in accurately characterizing this region for the future prospectively of the field. This integrated study can be applied and adapted to other basins in New Zealand and the southwestern Pacific. The proposed workflow is also suitable for analogous scenarios in various basins worldwide.

Food shortage driven crop residue burning and health risk

Ending global hunger is one of the greatest challenges humanity faces. The second Sustainable Development Goal (SDG 2), Zero Hunger, seeks to simultaneously address global environmental sustainability and food security challenges. However, ending hunger and food shortage would lead to the increase of agricultural activities and crop yields, which in turn might rise crop residue biomass burning, leading to adverse environmental and health consequences. This study estimated the health risk using modeled airborne benzo[a]pyrene (BaP), a common indicator of carcinogenic polycyclic aromatic hydrocarbons (PAH) released from crop residue biomass burning, and demonstrated the dependence of incremental lifetime lung cancer risk (ILCR) on the prevalence of undernourishment (PoU). Results showed that 10.4% of the global population are exposed to BaP concentration levels exceeding the EU target value (1 ng/m3) due to crop residue burning. The dependence of ILCR on PoU was attributed to increasing post-harvest crop residue biomass burning consequent to growing crop yield motivated by food shortage. Although global mean ILCR from crop residue burning BaP emission was positively correlated with the mean PoU at a correlation coefficient of r = 0.87 (p < 0.0001), positive and negative associations between PoU and ILCR were found among different less-developed countries. Eighty-nine less-developed countries were clustered into five groups, and the response of each group's ILCR to their respective PoU was assessed, which was interpreted by a human development index (HDI) that measured key dimensions of human development. Results also revealed that sustainable agriculture and implementation of air emission control measures play key roles in the association between hunger and ILCR.

On the use of low-frequency passive seismic as a direct hydrocarbon indicator: A case study at Banyubang oil field, Indonesia

Abstract Low-frequency passive seismic (LFPS), discussed in recent years, has emphasized a strong correlation between the spectral properties and the presence of hydrocarbon reservoirs. While the theoretical background supporting this phenomenon is still debated, its application has been popular in Indonesia and exposes broad possibilities for exploration. In this study, we conducted a survey at an oil field in Central Java, Indonesia, investigating the case of using this technique as a direct hydrocarbon indicator (DHI). In spatial and temporal measurements, we examined the hydrocarbon-related energy above the reservoir boundary based on several attributes of passive seismic recordings: polarization, power spectral density (PSD), and vertical-to-horizontal spectral ratio (VHSR). We address some issues: (1) the anomalies are not always vertically polarized, so the use of VHSR is unlikely to be reliable; and (2) the anomalies are getting amplified during days, so in anomalies mapping, normalizing the amplification requires calibration. Regardless, LFPS is still applicable in quantifying hydrocarbon-related energy. We recommend using PSD as a primary spectral attribute for DHI. In addition, it is also critical to synchronize the measurements at different sites to obtain an unbiased quantification of hydrocarbon-related energy.

Complex spherical-wave seismic inversion in anelastic media for the P-wave minimum quality factor

Attenuation always exists when seismic waves propagate in underground anelastic media, especially in hydrocarbon-bearing reservoirs. Quality factor Q or attenuation factor 1/ Q can be used to quantify the seismic wave attenuation and has become an important hydrocarbon indicator. The relationship between the plane-wave reflection coefficient ([Formula: see text]) in anelastic media and P- and S-wave quality factors has been widely used in the plane-wave seismic inversion to estimate the quality factors. The [Formula: see text] provides an adequate approximation for the deeper subsurface. However, for the shallow subsurface and anelastic wavefields excited by point sources, the [Formula: see text] is inaccurate and its meaning involves some fundamental difficulties. In view of this, a Q-dependent P-P spherical-wave reflection coefficient ([Formula: see text]) in anelastic media is used here. Considering that having too many parameters to be inverted will lead to unstable and inaccurate inversion results, we further derive an approximate anelastic [Formula: see text] and anelastic spherical-wave impedance ([Formula: see text]), which are frequency dependent and are the functions of P- and S-wave velocities, density, and P-wave minimum quality factor ([Formula: see text]). Finally, a complex spherical-wave seismic inversion approach in anelastic media for the P-wave minimum quality factor is developed. Using the Bayesian inversion approach and complex convolution model, we first estimate the multilayer [Formula: see text] from the complex seismic traces with different frequencies and incidence angles. Based on the inverted angle- and frequency-dependent [Formula: see text], the P- and S-wave velocities, density, and P-wave minimum quality factor are further estimated using a nonlinear inversion tool. Synthetic examples verify the feasibility and robustness of the complex spherical-wave seismic inversion approach in anelastic media. In the shallow subsurface, the spherical-wave inversion is superior to plane-wave inversion. A field example further demonstrates the accuracy and great potential of our approach in hydrocarbon-bearing reservoir prediction.

Dynamic multimedia approach for source apportionment of polycyclic aromatic hydrocarbons

This study was performed to evaluate the variable indicators of polycyclic aromatic hydrocarbons (PAHs) source apportionment by using an unsteady-state multimedia model. The identical indicators have been used in different environmental bulks for more than 20 years, which resulted in huge errors in source apportionment. Generated through four emission arrays, the diagnostic ratios for indicators revealed dimensionless OR, in air/soil and seawater/sediment reached ∼3.63 and ∼0.24 for Fla/Pyr, and for Ant/Phe the ratio was ∼0.31 and ∼0.18, and coastal OR for air/seawater was higher than the offshore, suggesting both compartmental and spatial divergences. The PCA indicated similar loading distribution and primary factors, shared by emission, atmosphere, and seawater arrays, whereas the slow transport between air/water and soil/sediment, weak degradation, and original concentration level might result in factors in soil and sediment separated or merged in dynamic conditions. The physicochemical divergence of indicators could be intensified after long-term environmental transport, misleading the source apportionment. Therefore, the result elucidated the essential evaluation of additional inorganic indicators and necessary verification by simultaneous sampling measurement on vertical compartments.

Fractal modeling of oil and gas geochemical data in the Taiwan Strait Basin

This study investigated the fractal characteristics of oil and gas indicators in the Taiwan Strait Basin using multifractal methods. The results revealed that these indicators can be categorized into five groups through cluster analysis, principal component analysis, and multifractal analysis. Acidolysis hydrocarbon indicators exhibited strong multifractal characteristics, while other indicators showed weak multifractal characteristics. The high values of Polycyclic aromatic hydrocarbons (F) indicators were mainly found in the southwest direction of the study area, whereas the high values of total aromatic hydrocarbons and their derivatives (UV) indicators were distributed in the eastern part. Erosion carbonate (ΔC) indicators were predominantly located in the western part, while the distribution of acid extractable hydrocarbons (A) and pyrolytic hydrocarbons (P) indicators was sporadic. The distribution of Erosion carbonate (ΔC) indicators in the Jinjiang Depression resembled that in the Jiulongjiang Depression, but the distribution of other indicators varied. The S-A method was employed to identify oil and gas anomaly target areas and predict and evaluate favorable prospect zones in the basin. This study provides a theoretical foundation for future oil and gas exploration and evaluation in the Taiwan Strait.

3D reservoir characterization of the Mangahewa Formation, Mangahewa Field, Taranaki Basin, New Zealand

The Mangahewa Formation is the primary reservoir target in the Mangahewa Field in the Taranaki Basin, New Zealand. This formation is distinguished by its marginal marine substantial tight-sand reservoir, having thickness exceeding 800 m. The aim of this study is to assess the reservoir properties of the Mangahewa Formation through 3D reservoir modeling, employing 3D seismic data, core data, and well data from the Mangahewa Field. Utilizing variance attributes, the faults and horizons have been identified successfully within the field. The majority of the interpreted faults exhibit dip angles exceeding 60°, with a maximum displacement of 118 m. To detect direct hydrocarbon indicators, root-mean-square amplitude seismic attribute, envelope, and generalized spectral decomposition techniques have been employed. Subsequently, four lithofacies, comprising 78.3% sandstone, 9.2% siltstone, 9.5% claystone, and 3.0% coal have been established by utilizing the Sequential Indicator Simulation (SIS) algorithm to create a lithofacies model. A property model has been generated using the Sequential Gaussian Simulation (SGS) algorithm. Petrophysical evaluation indicates that the Mangahewa Formation exhibits reservoir qualities ranging from fair to good, with porosity levels between 8% and 11%, permeability averaging up to 10 mD, variable shale volumes, and hydrocarbon saturation in the range of 40%–50%. This study's methodologies and findings can serve as a valuable foundation for similar investigations in other tight-sand gas fields located in different regions.

Dealing with unique minerals in petrophysical logs

Most petrophysical equations and methods are designed to deal with hydrocarbons found within mineralogies, such as quartz and feldspars or calcite and dolomite. Petrophysical tools and techniques have also largely been designed to investigate rocks containing these minerals. Hence, when log analysts encounter a field containing unique mineralogies, determining an appropriate petrophysical evaluation process for such unconventional reservoirs can be a challenge. In this paper, we aim to discuss our learnings using two unique case studies. The first is a well which had intersected opalines and logged with conventional modern “western style” tools. The second is a well which has intersected tuffs and volcanics and which was logged with older “Russian style” tools.For opalines, we discuss the potential mineral signatures observed on the well log data and the reservoir potential of the rocks. We find that the unique microporous structure created by opal-CT microspheres/lepispheres, combined with either fracture or matrix-porosity dominant properties, potentially allows for storage of hydrocarbons within the rock. Hence, we hypothesize that opaline reservoirs could be classed as “Low Resistivity Low Contrast” (LRLC) pay and should not be glossed over just because typical hydrocarbon indicators are not seen.For tuffs and volcanics, we first share some of the challenges faced and methods used in conducting modern petrophysical interpretation with data from older Russian-style logs. Again, we discuss the potential mineral signatures observed on the logs and look at properties such as pore throat radii, size, and mineral composition and how that affected reservoir potential. Our findings indicate that the distribution of pore sizes allowed for greater connectivity within the rock, where the pore geometry effects aided in low residual oil saturations.

Prestack inversion and amplitude variation with offset attributes as hydrocarbon indicators in carbonate rocks: A case study from the Illinois Basin

Prestack inversion and amplitude variation with offset attributes as hydrocarbon indicators in carbonate rocks: A case study from the Illinois Basin

Direct hydrocarbon indicator analysis to predict reservoir in Deepwater Krishna-Godavari basin: a case study

The amplitude Variations with Offset (AVO) technique is extensively used in hydrocarbon exploration and production for de-risking of the prospect before drilling. The interpretation of AVO results brings more confidence in the presence or absence of hydrocarbon. The AVO and Direct Hydrocarbon Indicator (DHI) analysis have their own inherent limitations. Therefore, to ensure the presence of true AVO in seismic, other attribute supports are crucial. The present prospect in this study was deposited as a channel-levee complex in the shelf-slope of the Krishna-Godavari basin. There is evidence of false AVO within this complex and thus additional attributes were used in this study to support the AVO analysis. The conventional AVO analysis shows the presence of Class-III AVO for a probable reservoir in seismic. However, it is unable to ensure the presence of hydrocarbon in the stacked reservoir unit. The spectral AVO technique was used to check AVO response at low frequencies for laminated and stacked reservoir units. Additionally, seismic attenuation and dispersion attribute studies were incorporated into the de-risking analysis. The drill result showed two distinct reservoir intervals in this prospect, which validated the predrill interpretation. This integrated approach added significant value in de-risking the prospect using AVO and other seismic attributes in complex geologic setups.

Static Reservoir Simulations and Seismic Attributes Application to Image the Miocene Deep-Water Reservoirs in Southeast Asia

Globally, deep-water reservoir systems are comprised of a variety of traps. Lateral and downdip trapping features include sand pinch-outs, truncation against salt or shale diapirs, and monoclinal dip or faulting with any combination of trapping designs; the potential for massive hydrocarbon accumulations exists, representing significant exploration prospects across the planet. However, deep-water turbidites and submarine fans are two different types of traps, which are developed along the upslope and the basin floor fans. Among these two traps, the basin floor fans are the most prolific traps as they are not influenced by sea-level rise, which distorts the seismic signals, and hence provides ambiguous seismic signatures to predict them as hydrocarbon-bearing zones for future explorations. Therefore, the deep-water channel-levee sand systems and basin floor fans sandstone define economically viable stratigraphic plays. The subsurface variability is significant, and hence, characterizing the thick (porous) channelized-basin floor fans reservoir is a challenge for the exploitation of hydrocarbons. This study aims to develop seismic-based attributes and wedge modeling tools to accurately resolve and characterize the porous and gas-bearing reservoirs using high-resolution seismic-based profiles, in SW Pakistan. The reflection strength slices better delineate the geomorphology of sand-filled channelized-basin floor fans as compared to the instant frequency magnitudes. This stratigraphic prospect has an area of 1180 km2. The sweetness magnitudes predict the thickness of channelized-basin floor fans as 33 m, faults, and porous lithofacies that complete a vital petroleum system. The wedge modeling also acts as a direct hydrocarbon indicator (DHI) and, hence, should be incorporated into conventional stratigraphic exploration schemes for de-risking stratigraphic prospects. The wedge model resolves a 26-m thick hydrocarbon-bearing channelized-basin floor fans lens with a lateral distribution of ~64 km. Therefore, this wedge model provides ~75% correlation of the thickness of the LSL as measured by sweetness magnitudes. The thickness of shale that serves as the top seal is 930 m, the lateral mud-filled canyons are 1190 m, and the thick bottom seal is ~10 m, which provides evidence for the presence of a vibrant petroleum play. Hence, their reveals bright opportunities to exploit the economically vibrant stratigraphic scheme inside the OIB and other similar global depositional systems.

Utilizing Direct Hydrocarbon Indicators on 3D-Seismic Data to Prove the Existence of Hydrocarbon Accumulation in the Subtle Stratigraphic Trap in the Mishrif Reservoir at the Dujaila Oil Field, SE of Iraq

The current study aims to utilize the Direct Hydrocarbon Indicators technique to identify the presence of hydrocarbons in the Carbonaceous Mishrif Formation (Late Cretaceous) from the 3D seismic data (post-stack) integrated with available information of two wells (Du-1 and Du-2). The 3D-seismic survey was carried out in 2010, covering 602.62 km2, at the Dujaila oil field in Maysan, SE of Iraq. Distinct seismic features for hydrocarbon presence indicators were diagnosed and identified on both sections of seismic amplitude and instantaneous phase, such as dim spots, flat spots, and phase polarity reversals. They helped in direct detecting the presence of hydrocarbon accumulation in the stratigraphic trap, in the region around well Du-1 at the upper part of Mishrif Formation, which is located at a time (TWT) extending from -1730 ms in the top Mishrif to underneath at TWT -1775 ms that corresponded with depth 2825 m to 2887.5 m, respectively. Furthermore, based on the well-defined position of a flat spot, which represents oil-water contact; it helped to determine the length of the oil column was 56.8 m in the vicinity of productive well Du-1. It is close to the actual length of the oil column measured in the well was 49 m. As a result, the circular area with a radius of about 3 km around well Du-1 is more suitable for low-risk drilling in the future.

The Application of Seismic Attributes in Fault Detection and Direct Hydrocarbon Indicator in Tomboy Field, Western-Offshore Niger Delta Basin

Seismic attribute analysis is important in subsurface data interpretation, such as seismic interpretation, which could involve seismic stratigraphic and structural interpretation. This interpretation is often hampered by seismic resolution and, sometimes, human inability to identify a subtle feature on the seismic. These factors have frequently led to the poor seismic interpretation of geologic features. Thus, an integral approach to studying structural patterns and hydrocarbon bearing zones using seismic attributes was carried out on the Tomboy field using 3D seismic data covering approximately 56 km2 of the western belt of the Niger Delta. The seismic volume underwent post-stack processing, which enhanced seismic discontinuities. A deep steering volume was first created, and several dip filters were applied to enhance faults in the study area. After that, curvature and similarity attributes were calculated on the dip-steered and fault-enhanced volume. These calculations show detailed geometry of the faults and zones of subtle lineaments. Six faults (F1, F2, F3, F4, F5 and F6) were identified and mapped. These faults range from antithetic to crest growth faults. Two major growth faults (F5 and F6) were revealed to dip in the northeast to southwest directions. A near-extensive crest fault (F4) appeared beneath the major faults. Although several minor fractures were displayed in the southern and central portions of the crest fault of the dipping seismic data, the southwest (F4) and growth fault, F6, are responsible for holding the hydrocarbon found within the identified closures. Using attributes on the seismic data increased confidence in mapping and interpreting structural features. Furthermore, energy attributes were used as Direct Hydrocarbon Indicators (DHI) to visualize viable areas within the study, which allows a more robust interpretation. Time slices were taken in regions of flat and bright spots. The spectral decomposition attribute was run on these slices to display areas of high amplitude reflection typical of hydrocarbon-bearing regions trapped mainly by regional to sub-regional growth faults. The surface attribute calculated on the generated surface shows that the field is predominantly controlled by faults serving as traps for hydrocarbon.