Natural Gas Exploration Research Articles

Diagenetic Facies and Their Controls on the Quality of Tight Sandstone Reservoirs: A Case Study from the Upper Paleozoic Gas Reservoir in the Eastern Ordos Basin, North China

Diagenetic facies play a significant role in the evaluation and prediction of reservoirs as they comprehensively reflect the spatial distribution characteristics of deposition, diagenesis, and petrophysical properties. Based on the petrographic observation and considering pores, lithology, and diagenesis types, the diagenetic facies types were identified, and the pore evolution process and its influence on the quality of low permeability tight gas reservoirs were analyzed. The results show that six types of diagenetic facies were identified, including siliceous cementation intergranular pore facies (A), carbonate dissolution pore facies (B), matrix dissolution pore facies (C), clastic dissolution pore facies (D), matrix filling and strong compaction tight facies (E), and carbonate cementation and metasomatism tight facies (F). The evolution process of porosity shows that the restored original porosity is indicated to be between 34.2% and 36.0%. The average porosity loss caused by compaction was 17.1%, while the average porosity loss caused by cementation is 14.1%. The average porosity increased by 2.5% on diagenetic facies B, C, and D due to dissolution. Consequently, diagenetic facies A with weak compaction and diagenetic facies B, C, and D with strong dissolution are effective reservoirs with porosity greater than 6.6% and permeability greater than 0.25 − 0.6 × 10 − 3 μm2. The distribution areas of A, B, C, and D are favorable areas for tight gas exploration and are important indicators for the prediction of tight gas in the Upper Paleozoic Shanxi Formation in the eastern Ordos Basin. This study provides a new petrographic method for reservoir prediction and exploration of natural gas, which has practical value and economic significance.

Microbial communities and their roles in the Cenozoic sulfurous oil reservoirs in the Southwestern Qaidam Basin, Western China

The latest discovery of sulfurous natural gas marked a breakthrough in the Cenozoic natural gas exploration in the southwestern margin of Qaidam Basin. The 16S rRNA analyses were performed on the crude oil samples from H2S-rich reservoirs in the Yuejin, Shizigou and Huatugou profiles, to understand the sulfurous gas origin, which was also integrated with carbon and hydrogen isotopes of alkane and sulfur isotopes of H2S collected from the Yingxiongling Area. Results show that the microorganisms in samples can survive in the hypersaline reservoirs, and can be classified into multiple phyla, including Proteobacteria, Planctomycetes, Firmicutes, Bacteroidetes, and Haloanaerobiaeota. Methanogens are abundant in all of the three profiles, while sulfate-reducing bacteria are abundant in Yuejin and Huatugou profiles, contributing to the methane and H2S components in the natural gas. The carbon, hydrogen and sulfur isotopes of sulfurous natural gas in the Yingxiongling Area show that the natural gas is a mixture of coal-type gas and oil-type gas, which was primarily derived from thermal degradation, and natural gas from the Yuejin and Huatugou profiles also originated from biodegradation. The isotopic analysis agrees well with the 16S rRNA results, i.e., H2S-rich natural gas from the Cenozoic reservoirs in the southwest margin of the Qaidam Basin was primarily of thermal genesis, with microbial genesis of secondary importance.

A Flexible, Low-Cost, Miniature Methane Sensor Based on PEDOT:PSS

The development of methane sensors with high sensitivity is vital for the safe application of methane. In this work, we developed a new flexible, low cost, miniature methane sensor based on PEDOT:PSS coated screen-printed electrochemical electrodes as a resistive sensor. PEDOT:PSS is used as a sensing electrode, and the presence of methane causes a change in the resistance of the PEDOT:PSS layer. The sensor demonstrates a fast detection time of 10 s, excellent sensitivity of 0.5 pA/ppm, and a wide linear detection range of 600 to 0.8x10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> ppm. The sensor shows excellent stability and reliability. The detection error is within 2.8% for a single sample, 7.1% for different samples from the same batch, 16% for different batches and different samples, 3.4% for storage for 4 days, and 14% for temperature increase to 70°C. The sensor is simple to prepare, low cost and highly flexible. We anticipate that this work could open up exciting opportunities for the development and application of methane sensors, such as natural gas exploration and identification of methane leaks in mining and kitchens.

Salt Diapir‐Driven Recycling of Gas Hydrate

AbstractBy harnessing both hypothetical, synthetic basin and gas hydrate (GH) system models and real‐world models of well‐studied salt diapir‐associated GH sites at Green Canyon (Gulf of Mexico) and Blake Ridge (U.S. Atlantic coast), we propose and demonstrate salt movement (and in particular, diapirism) to be a new mechanism for the recycling of marine GH. At Green Canyon, for example, we show that by considering this newly proposed diapir‐driven recycling mechanism in conjunction with previously proposed lithological control on sandy‐reservoir‐hosted hydrate at the base of the GH stability zone (BGHSZ; ∼bottom‐simulating reflector, BSR), modeled GH saturations match drilling data. Overall, salt diapir movement‐induced GH recycling provides a temperature‐driven mechanism by which GH saturations at the BGHSZ may reach &gt;90 vol. % and by which GH volumes near and free gas volumes beneath the BGHSZ may be increased significantly through time. Interestingly, comparison of salt diapir‐driven recycling and sediment burial‐driven recycling scenarios suggests notably higher rates of recycling via diapir‐driven versus burial‐driven processes. Our results suggest that GH and associated free gas accumulations above salt diapir crests represent particularly attractive targets for unconventional and conventional hydrocarbon resource exploration and for scientific and academic drilling expeditions aimed at exploiting GH systems. Salt basins containing GH systems—including passive margin basins of the Gulf of Mexico, southeastern Brazil, and southwestern Africa—are therefore compelling localities for studying salt‐driven GH recycling and for salt diapir‐associated natural gas exploration.

Pore structure characteristics of different lithofacies of the Longmaxi shale, Western Hunan‐Hubei Region, China: Implications for reservoir quality prediction

Lithofacies and micropore characteristics of shale reservoir directly affect the exploration and development of natural gas. To determine the development potential of shales of the Longmaxi Formation in the Western Hunan‐Hubei Region, the lithofacies types and micropore structure characteristics of the Longmaxi Formation shales have been systematically studied in this paper, based on ordinary thin sections, argon ion polishing–scanning electron microscopy, physical property testing, x‐ray diffraction whole‐rock and clay mineral analysis, isothermal nitrogen, and carbon dioxide adsorptions. According to the principle of ‘laminar structure + total organic carbon (TOC) + mineral composition of felsic, clay, and carbonate minerals’, eight types of shale lithofacies were identified. The effective porosity of the Longmaxi shale ranges from 1.8% to 14.4%, with a peak range from 3% to 6%, while the permeability ranges from 0.001 to 1.27 mD, with an average of 0.106 mD. Combined with the isothermal adsorption experiments, the proportion of mesopores is the largest in the Longmaxi shale, followed by macropores and micropores. Moreover, the pore diameters of mesopores are concentrated between 3 and 10 nm, while those of micropores are concentrated between 0.4 and 0.9 nm. The pore volume of shale is most developed when the content of brittle felsic minerals is 50% ~ 75% and the content of clay minerals is 25% ~ 50%, and the TOC content is positively correlated with the pore volume and specific surface area. There are significant differences in the pore development characteristics of different lithofacies. The shale reservoir space analysis indicates that micropores are controlled by TOC content and clay minerals, while the macropores are controlled by depositional intergranular pores, TOC content, and felsic content, as well as diagenetic pyrite mould pores, microfractures pores, and intercrystalline pores. On the other hand, mesopores are related to a mix of depositional and diagenetic factors with dominant contribution of intergranular pores, intercrystalline pores, organic pores, and intergranular shrinkage fractures pores. It is found that the pore development of massive organic‐rich siliceous shale lithofacies has the best reservoir quality, including well‐connected intergranular pores, intercrystalline pores, organic pores, and shrinkage fractures. Therefore, the massive organic‐rich siliceous shale lithofacies is the dominant fine‐grained reservoir lithofacies in the studied area. Based on understating the pore characteristics of different lithofacies, this study can provide a scientific basis for the prediction of favourable sweet spots of shale gas reservoir in the Longmaxi Formation, western Hunan‐Hubei Region.

Multistage dolomitization of deeply buried dolomite in the Lower Cambrian Canglangpu Formation, central and northern Sichuan Basin

The dolostone units in the Cambrian Changlangpu Formation of the Sichuan Basin have demonstrated substantial potential for natural gas exploration. A systematic understanding of the various dolomite (and non-carbonate) phases that build these rocks and the diagenetic pathways of the Canglangpu Formation carbonates still needs to be developed. This study combines the petrographic properties of dolomite (and non-carbonate) phases with their geochemical evidence (carbon, oxygen and 87Sr/86Sr isotope data). Moreover, fluid inclusion evidence and in situ rare-earth element (REE) data are presented. The samples studied were taken from hand specimens collected in the field and plugs from cores to explore the properties and evolutions of dolomite in the Cambrian Canglangpu Formation in the central-northern Sichuan Basin. Six dolomite phases are identified: silty crystalline dolomite (D1), fabric-retentive dolomite (D2), fabric-destructive dolomite (D3), fine crystalline dolomite (D4), medium to coarse crystalline dolomite cement (C1a and C1b) and saddle dolomite cement (C2). Silty crystalline dolomite represents the earliest dolomitization and shows δ18O values comparable to those of Cambrian seawater. Fabric-retentive dolomite, fabric-destructive dolomite and fine crystalline dolomite represent reflux dolomitization during shallow burial. Specifically, Fine crystalline dolomite with a turbid-core and clean-rim may have recrystallized from secondary dolomitization of marine-derived porewater. Fabric-destructive dolomite shows the depleted δ13C values, resulting from the secondary dolomitization involving organics degradation in medium to deep burial environment. The fluid inclusion data demonstrates that the medium to coarse crystalline dolomite cement (C1a) formed in relatively elevated temperature and salinity brines. Intrusion of sulfur- and metal-rich (Zn and Fe) medium-temperature hydrothermal fluids gave rise to the formation of medium to coarse crystalline dolomite cement (C1b) and sphalerite mineralization. Cementation of saddle dolomite was promoted by sulfate-rich reducing hydrothermal fluids. δ13C depletion, extremely low REE content and positive δEu in the saddle dolomite cement suggest the presence of thermal sulfate reduction.

SECURITY OF NATURAL GAS SUPPLY TO CONSUMERS IN UKRAINE AND POLAND IN THE FACE OF OPEN RUSSIAN MILITARY AGGRESSION IN 2022 (COMPARATIVE STUDY)

Security of natural gas supply to consumers in Ukraine and Poland in the face of open Russian military aggression in 2022 (comparative study).&#x0D; Military operations, including Russian attacks on natural gas production sites controlled by Ukraine and network restrictions, have led to a 7 % year- on-year decline in natural gas production and the temporary loss of natural gas access for hundreds of thousands of Ukrainian consumers. In 2022, 18,5 bcm of natural gas is likely to have been produced. The autumn suc- cesses on the frontline allowed Ukraine to start clearing damage on reco- vered territories and increase the number of new drillings.&#x0D; The extensive damage to companies using natural gas in production that was caused by Russian attacks and the scale of emigration reduced natural gas consumption in Ukraine by a quarter. Nevertheless, imports were ne- cessary. It was most profitable for the government in Kyiv to bypass transit costs and buy part of the natural gas supplied from Russia via Ukraine to the EU.&#x0D; Due to the cost of transit, a smaller part of the gas acquired by Ukraine was from other countries (e.g. Norway). The amount of natural gas (owned and owned by foreign companies) in storage in Ukraine at the end of October was 14,2 bcm. In the end, from its western partners Ukraine probably im- ported a total of only 1,5 bcm. Likely, some of the natural gas owned by foreign counterparties stored in Ukrainian storage facilities was purchased. As of 2021, the demand for Polish customers was lower than for Ukrainian needs. According to preliminary data, some 16,15 bcm of natural gas was sent to Polish consumers in 2022. Probably mainly due to the authorities’ protective moves towards households, natural gas transmission to domestic consumers in Poland fell by only less than 17,5 % compared to 2021. Indus- trial use of natural gas has decreased more.&#x0D; The Polish authorities have completed many investments (or made progress in this area) in natural gas infrastructure long postulated by experts. The degree of depletion of deposits and the high capital intensity of natural gas exploration and production requires a significant increase in investment in natural gas exploration and production to stop the further decline in natural gas production in both countries.

Natural gas potential of Neogene source rocks in the Yiliping area, Qaidam Basin: Using an improved hydrocarbon generation and expulsion model based on least‐squares Monte Carlo

The Neogene petroleum system in the Yiliping area of the Qaidam Basin presents great prospects for natural gas exploration. However, its natural gas potential, including the source rock characteristics, is insufficient. Due to a lack of geological constraints, the hydrocarbon generation and expulsion (HGE) model, which is widely used in resource potential evaluation, may be unable to obtain optimal parameters. Here, we propose an improved HGE model based on least‐squares Monte Carlo to assess the HGE characteristics and natural gas resource potential of the Neogene source rocks in the Yiliping area by combining geological and geochemical investigations. The findings show that the Neogene source rock is effective and has significant potential for natural gas generation. Algae and bacteria, which were deposited in a saline and anoxic environment, are the primary sources of organic matter in Neogene source rock (primarily Type II and Type III). Modelling work suggests that Type II and III kerogen of Neogene source rock reach hydrocarbon generation threshold (HGT) at Ro = 0.38% and Ro = 0.49% and reach hydrocarbon expulsion threshold (HET) at Ro = 0.45% and Ro = 0.55%. The maximum HGE intensities are 3400 × 104 and 3378 × 104 t/km2. The extra‐source natural gas and shale gas resource potentials are predicted to be 2.05 × 1012 m3 to 4.11 × 1012 m3 and 7.03 × 1012 m3. The findings will guide future Neogene natural gas exploration in the Yiliping area of the Qaidam Basin.

Pelagic and estuarine birds as sentinels of metal(loid)s in the South Atlantic Ocean: Ecological niches as main factors acting on bioaccumulation

Activities related to the offshore exploration and production of oil and natural gas provide economic development and an essential energy source. However, besides the risk of petroleum hydrocarbon contamination, these activities can also be sources of metals and metalloids for marine organism contamination. In this research, we evaluated the potential use of two pelagic (black-browed albatross Thalassarche melanophris and yellow-nosed albatross T. chlororhynchos) and one estuarine bird species (neotropical cormorant Nannopterum brasilianus) as sentinels of contamination of As, Cd, Cr, Cu, Pb, Mn, Mo, Zn, Ni, Ba, V, and Hg in an area under influence of oil and gas activities. The analyses were carried out in samples collected from 2015 to 2022 from 97 individuals. A factor alert; an adaptation from the contamination factor is proposed to identify individuals with high concentrations that possibly suffered contamination by anthropogenic origin. Grouping all species, the metal(loid)s with the highest concentrations were in decreasing order: Zn > Cu > Mn > Hg > As > Cd > Mo > V > Cr > Ba > Ni > Pb. Similar concentrations were observed for V, Mn, Cr and Pb among the three species. Pelagic birds showed higher levels of concentrations for Hg, As and Cd. Based on the correlations and multivariate analysis performed, the results indicate that the ecological niche factor has greater relevance in the bioaccumulation of these elements compared to the habitat. Although some individuals showed high concentrations in part of the trace elements, suggesting exposure to anthropic sources, the direct influence of oil production and exploration activities was not observed, suggesting that activities on the continent are the primary contamination source. The results of this work highlight the role of seabirds as sentinels for metal(loid)s, contributing to the knowledge of the occurrence of contaminants in the South Atlantic Ocean.

Decipher hydrocarbon generation and accumulation based on fluid inclusion and chronology: A case study from the Upper Paleozoic buried-hills in Huanghua Depression, Bohai Bay Basin

Deciphering hydrocarbon generation and accumulation stage is of significance to understand oil and gas evolution and seek exploration targets. Taking the Upper Paleozoic buried-hills in the Huanghua Depression, Bohai Bay Basin, as a case study, hydrocarbon generation environment and detailed accumulation process are revealed by fluid inclusions observations, Laser Raman spectroscopy, Fourier Infrared spectroscopy, and K–Ar isotope measurements. The results show that both oil and gas inclusion were captured in the quartz overgrowth, dissolved feldspar and calcite microfractures, showing blue to dark brown fluoresce. The grains containing oil inclusions index (GOI) of oil, oil & gas and gas being 25%, 65%, and 10% and the inclusions with abundant methyl groups and short chains, both indicate high thermal maturity. One series of fluids inclusion is generally observed, evidenced by the concentrated homogenization temperature of 135–145 °C and salinity of 3%–15 w.t.% NaCl equiv, indicating one primary charging stage. The gas and gas & liquid inclusions mainly contain CH4, with also peaks indicating CO2 and N2. The Carboniferous and Permian biomarkers show reducing environment with brackish water, with organic matter sources both from marine and continental. The relative content of ααα20RC27, ααα20RC28, and ααα20RC29 exhibit source contributions both from algae and higher plants, and mainly of II2 to III kerogen. Both coal derived gas and oil associated hydrocarbons are identified from most of the buried-hills. Combining the fluid homogenization temperature and salinity, as well as the thermal evolution history, the hydrocarbon generated from the Upper Paleozoic was concentrated at the end of the Eocene (40 Ma±), while the beginning of charging is 60 Ma±. The Wumaying Buried-hill is of only coal derived gas and has potential for inner coal measure natural gas exploration. The results provide a detailed understanding of hydrocarbon accumulations in the study area, which can also be reference for improving petroleum exploration efficiency in similar basins.

Geochemical characteristics of source rocks and gas exploration direction in Shawan Sag, Junggar Basin, China

In recent years, significant advancements have been achieved in the exploration of natural gas around Shawan Sag in the Junggar Basin. However, the geochemical characteristics and distribution of source rocks in the center of the sag have yet to be thoroughly researched, and there is a lack of understanding regarding the evolution history of hydrocarbon generation and the characteristics of each set of source rocks. This has posed limitations on future exploration and development initiatives in the area. The study focused on source rock samples from the uplift zone and conducted a comprehensive evaluation through seismic and hydrocarbon generation thermal simulation experiments. This allowed for clarification of the product characteristics of source rocks in different strata and pointing out the direction for future natural gas exploration. The results showed the presence of four sets of well-developed source rocks in Shawan Sag, characterized by their extensive thickness, wide distribution, and deep burial, laying a material foundation for oil and gas accumulation in peripheral structures. The Carboniferous and Jiamuhe Formation source rocks have high organic matter abundance, but the quality is poor and the potential for generating hydrocarbons is low, leading mainly to the generation of dry gas. On the other hand, the Fengcheng Formation and Lower Wuerhe Formation source rocks have high organic matter abundance and good quality, and are highly mature, resulting in high potential for generating hydrocarbons. The δ13C1-RO regression equation of natural gas in Shawan Sag was established, and the carbon isotope distribution patterns of ethane generated from source rocks in different layers were identified, providing a foundation for determining the maturity of natural gas and correlating the sources of gas in surrounding structures. The west slope of Shawan Sag has favorable preservation conditions and is located on a hydrocarbon migration pathway, similar to the slope of Mahu Sag. This area also has favorable geological conditions for the formation of large lithologic reservoirs, making it a key field for gas exploration in the study area moving forward.

Study of Socio-Economic-Cultural Impacts and Community Health Due to Oil and Natural Gas Exploration Activities in the Tuban Oil and Gas Field

This research is a social study by capturing several problems in the oil and gas sector combined with literature studies that have relevant themes. This study aims to determine the social, economic, cultural and health impacts of the oil and gas company's exploration activities in the Tuban Oil and Gas Field. Data collection was in the form of primary data and secondary data in semester II of 2018. The methods used in this study were qualitative and quantitative methods. Qualitative methods taken from primary data, namely observation and interviews. Primary data were obtained through direct observation and interviews with respondents selected by purposive sampling. The quantitative method uses secondary data obtained from research documents and reports relating to government agencies and companies. Primary data and secondary data were combined and then conducted interviews to obtain deeper information using the forum group discussion (FGD) method. The final data obtained were analyzed using descriptive statistical methods. The results of the study show that there are jobs for local workers, but the information is still not transparent and most of the jobs are temporary projects. Most people know and feel the benefits of the presence of oil and gas companies in their area. The community expects the company's attention to reduce people's concerns about oil and gas activities. Conflicts often occur due to delays in the disbursement of compensation funds and the implementation of CSR, as well as several oil and gas company activities that have a direct impact on the community. The company's efforts to boost the local economy by increasing employment opportunities and increasing wage rates. Meanwhile, in terms of public health, it cannot be determined with certainty whether there is a correlation between disease and the activities of oil and gas companies. In general, oil and gas companies have a positive impact on the community around the working areas of oil and gas companies.

Origin of a giant fuzzy reflection zone and its implication for natural gas exploration in the southwestern Qiongdongnan Basin of the South China Sea

Origin of a giant fuzzy reflection zone and its implication for natural gas exploration in the southwestern Qiongdongnan Basin of the South China Sea

Natural gas characteristics and gas-source comparisons of the Lower Triassic Feixianguan Formation, Eastern Sichuan Basin, China

There is great controversy regarding the origin and source of natural gas in the Lower Triassic Feixianguan Formation in the Eastern Sichuan Basin. This seriously restricts the study of natural gas dynamics in the Feixianguan Formation and thus hampers natural gas exploration in the region, so further study is urgently required. Using experimental tests of natural gas composition, stable isotopes, and noble gas isotopes with gas chromatography (GC) and mass spectrometry (MS) studies of source rock and reservoir asphalt saturated hydrocarbons, the natural gas geochemical characteristics, the genetic identification and a gas-source comparison of the Feixianguan Formation were studied. Then, constrained by the thermal history, the histories of gas generation and expulsion were restored by basin simulation technology. Finally, a gas accumulation model was established for the Feixianguan Formation. The results showed that (1) the H2S-rich and H2S-poor gas reservoirs of the Feixianguan Formation are distributed on the east and west sides of the Kaijiang-Liangping trough in the Eastern Sichuan Basin, respectively. The carbon and hydrogen isotope compositions of the natural gas in the gas reservoirs are generally heavy and have typical characteristics of high-maturity dry gas reservoirs. (2) The natural gas of the Feixianguan Formation is organic thermogenic gas, which is mainly oil-type gas generated by the secondary cracking of crude oil. The gas-generating parent material is mainly type II kerogen. (3) The natural gas of the Feixianguan Formation in the Eastern Sichuan Basin was mainly generated by argillaceous source rocks of the Upper Permian Longtan Formation. (4) Natural gas accumulation occurred as follows: the paleo-structure heights were filled with crude oil in the Early Jurassic, and paleo-oil reservoirs were formed in the Feixianguan Formation; during the Middle-Late Jurassic, the paleo-oil reservoirs were cracked when the reservoir temperatures rose above 160 °C, and paleo-gas reservoirs were formed. Since the end of the Late Jurassic, the paleo-gas reservoirs have been adjusted and reformed to form the present-day natural gas reservoirs. These results provide a basis for studying natural gas accumulation dynamics of the Feixianguan Formation in the Eastern Sichuan Basin.

Appraisal of tectonically-influenced lowstand prograding clinoform sedimentary fairways of Early-Cretaceous Sember deltaic sequences, Pakistan using dynamical reservoir simulations: Implications for natural gas exploration

The Early Cretaceous reservoir system of the Indus basin has a suite of stratigraphic-based trapped petroleum plays such as the fluvial-dominated channelized systems, shallow marine incised valley systems, and lowstand prograding clinoforms. However, the seismically-imaged Lowstand prograding clinoform plays (LCP) are hot topics in the stratigraphic-based hydrocarbon traps-bearing traps fairways. These LCPs remain established throughout an extensively falling sea level with succeeding growth, which fills these LCPs with gas-saturated reservoirs. The LCP remains mud-dominated, which has created ambiguous expressions in full-spectrum seismic. Hence, they in turn complicate the prediction of the stacking patterns of the depositional parasequences, the source of sedimentary influx, the angle of stratigraphic traps, and their controls on the vertical/lateral migration of hydrocarbon-bearing fluids. The bandlimited seismic amplitude lacks the tuning frequency, which is one of the key parameters in the seismic sedimentological analysis given the above-mentioned constraints. This study connects the broadband spectral analysis with the bandlimited seismic amplitude-based attributes to quantify the LCP using wavelet transform-based impedance-decomposed porosity-gas-saturation of velocity and density simulations (PGVDS). The seismic amplitude and 23-Hz CWT attribute have allowed the detection of vertical thickness, lateral distribution, and angle of coarse-grained and fractured sigmoidal LCP facies of 22 m, 6 km, 7°, and 26 m, 12 km, 5°. The PGVDS have predicted the thickness, density, and velocity for porous gas-saturated LCP as 31–34 m, 2.1–2.15 g/c. c, 80–85%, 29–32%, 2139–2304 m/s, and non-porous water-saturated LCP as 18–28 m, 2.2–2.39 g/c. c., 60–75%, 17–25%, 2863–3108 m/s. The PGVDS have also imaged the highly fractured and laterally continuous fluvial-dominated onlapping channel-filled reserves that served as a source of generating a high impact of sedimentary influx within aggradational stacking patterns for gas-saturated (80–85%) sedimentary facies of LCP at an angle of zero degrees and porosity range of >30%. The lateral changes in the densely fractured network validate the facies-controlled migration of hydrocarbon-bearing reserves within the LCP, which implicates the development of regionally developed stratigraphic-based trapping plays throughout the basins of Pakistan. This study has categorically broadened the impact of connecting the spectral attributes of inverted reservoir simulations in inferring the geometry, extent, thickness, and distribution of hydrocarbons in prograding clinothems inside the Indus Basin. Hence, this research can serve as an analogue for the exploration of worldwide LCP with similar geological conditions.

A New Methodology Combining Geophysical Calculations and Geological Analysis to Identify and Characterize Carrier Systems for Vertical Hydrocarbon Migration in the Central Diapir Zone of the Yinggehai Basin, China

To understand hydrocarbon migration in terms of the mechanisms, accumulations and exploration targets, it is essential to correctly identify and characterize the carrier systems that control fluid-migration history and oil/gas reservoir formation. The Yinggehai Basin in China is an important area for natural gas exploration and production. However, due to the argillaceous sand sedimentary environment and the absence of faults from the Neogene thermal subsidence period, traditional migration pathways are absent in the Yinggehai Basin, posing significant challenges to target evaluation in this area. Exploration shows that most of the existing gas reservoirs are associated with vertical migration. In this work, coherence cube and curvature seismic techniques are used in the central diapir zone of the Yinggehai Basin to identify diapir-associated fractures and regional stress. Together with geological analysis, two categories of carrier system are discussed in detail to explain the complex migration and accumulation patterns that have puzzled the area. Diapirs have five evolutionary phases, i.e., pressurization, piercing, equilibrium, release and collapse, which have different fracture development patterns, leading to different mechanisms of hydrocarbon migration and accumulation. The carbon isotopes of gaseous hydrocarbons in DF shallow layers and mid-deep layers have an inverted order distribution, indicating mixed accumulation with different maturity, whereas in the mid-deep layers of the diapir-affected areas, there is a single accumulation with low maturity. Early diapiric activity allowed the natural gas produced from deep source rocks to migrate upward along the diapiric carrier system and accumulate in suitable traps to form gas reservoirs. For regional-stress related fractures, the gradual loss of overpressure and fluids from deep to shallow in high-pressure fractures results in the gas accumulation time of deep traps in the regional stress-related carrier system being relatively late and the gas accumulation time of shallow traps being relatively early.

Quantifying spatial characteristics of the Bowhead Whale Aerial Survey Project (BWASP) survey design

The Bowhead Whale Aerial Survey Project (BWASP) has been conducted annually since 1979 in the Alaskan Beaufort Sea to monitor the distribution and relative abundance of the Bering-Chukchi-Beaufort (BCB) stock of bowhead whales (Balaena mysticetus) during their autumn migration. BWASP was created to specifically address broad-scale research and management questions related to bowhead whale ecology, with particular interest in the potential effects of oil and natural gas exploration, development and production activities on the BCB bowhead whales. With elevated concerns about climate change, increasing oil and gas activities and the forecasted increase in vessel traffic, it is expected that interest in the BWASP dataset will also increase in order to evaluate effects of these anthropogenic activities on BCB bowhead whales and indigenous whaling. The following analysis quantified the spatial characteristics of the BWASP survey design and provided guidelines for the types of investigations that the BWASP data can potentially address. Sampling lags (transect spacing) in the BWASP survey design of approximately 20km along the east/west axis of the study area limit the spatial scale of phenomena that can be detected using data from a single BWASP survey. Therefore, BWASP data are relatively uninformative for studying variability in distribution or relative abundance along the east/west axis over short time scales (one survey) and within small areas measuring less than approximately 20km. In addition, computer simulations showed spatial heterogeneity in the long-term survey coverage probability (the probability that a given location will be included in a survey having an assumed effective search width under the BWASP survey design). Pooled transects created from simulated surveys resulted in a repeating diamond pattern in which coverage probability was low. Analyses incorporating data from many BWASP surveys should account for this spatial heterogeneity, via either the survey coverage probabilities or quantification of survey effort; otherwise estimates of variables such as relative density, density, or habitat use may be biased. The BWASP surveys have increased understanding of the broad-scale patterns of bowhead distribution, relative abundance and behaviour. The utility of this dataset in informing other questions will depend upon the scale of the ecological phenomena under investigation and the analytical scales used to address the questions.

Paleoenvironment reconstruction of the Middle Ordovician thick carbonate from western Ordos Basin, China

Reconstructing paleoenvironments has long been considered a vital component for understanding the development and evolution of carbonate reservoirs. The Middle Ordovician Period is considered the archetypical greenhouse interval, and also a critical period in biological evolution. The Middle Darriwilian isotope carbon excursion has been observed in many areas of the world and may be related to the biological explosions caused by decreases in the temperature. The thick carbonate rocks in the fifth member of the Middle Ordovician Majiagou Formation in the Dingbei area of the Ordos Basin were chosen as an example, based on the concentration of major, trace and rare earth elements as well as C, O and Sr isotopic analyses, the paleoenvironment was reconstructed. And its impact on natural gas exploration was analyzed. The results show that the seawater paleotemperature was 29 °C, suboxic-anoxic paleoredox conditions were observed, and the seawater paleosalinity was high. A large number of plankton in the biological explosion caused a rapid increase in the total organic carbon in carbonate rocks, which provided natural gas as supplemental source rocks. Affected by early meteoric water, the dissolution of gypsum laid the foundation for high-quality reservoirs, and the residual gypsum also further preserved natural gas. This study provides new data for the paleoenvironment and a theoretical basis for further natural gas exploration.

Building Options for the Brazilian Pre-salt: A technical-economic and infrastructure analysis of offshore integration between energy generation and natural gas exploration

The objective of this work is to evaluate the technical-economic and infrastructure aspects for the Brazilian Pre-salt natural gas use. Factors like technology maturity level, fuel and facilities costs, and electricity market are analyzed; the levelized cost of energy (LCOE) of two possibilities are calculated: (i) offshore Gas-to-Wire (GtW) and (ii) molecular natural gas outflow through the pipeline with onshore thermoelectric generation. This work also discusses the possibility of natural gas (NG) transport via liquefaction, considering the Floating Liquefied NG (FLNG) technology for national and international market. The LCOE of GtW technology is higher (67–87 US$/MWh) than onshore plants (43–69 US$/MWh) for Pre-salt area, higher than the historical energy price of Brazilian NG thermoelectric generation (44 US$/MWh), but, in general, lower than Brazilian NG energy auction price cap (84.5 US$/MWh) and lower than some values found in the literature for onshore plants (42–124 US$/MWh) abroad Brazil. FLNG technology is still new, there is no scale, few players use it, and it does not seem to be a feasible option for Pre-salt NG now. It is concluded that elements such as political uncertainties of the international natural gas market, the high CO2 rate in the Pre-salt's natural gas mixture, and the difficulties in implement deep-sea infrastructure are challenging elements for the three possibilities analyzed. The Brazilian market discussion is relevant since it is a greenfield natural gas area in need of development. Thus, it is of upmost importance to implement a comprehensive energy policy to address offshore-onshore energy integration regulation and technological developments for the offshore transmission systems, and CO2 content separation process.

Formation conditions of natural gas fields in the lacustrine basin in eastern China: Insights into the first discovery within the Bohai Bay Basin

The hydrocarbon source of Bohai Bay Basin is dominated by oil-prone kerogens of type II2-II1 within semi-deep and deep lacustrine facies. In the Neogene period, faults were well-developed via significant structural activity. The Bohai Sea is generally considered to have no geological basis for the formation of large natural gas fields. Through analogous analysis of domestic and international gas fields, the key geological factors that restrict formation in continental rift lacustrine basins were studied, including gas source, preservation conditions, and reservoirs. A natural gas enrichment and accumulation model within a petroliferous basin is presented. The model indicates that rapid subsidence and high-intensity gas generation within petroliferous sags during the late stages were main contributors to natural gas field formation. Archean metamorphic buried hill reservoirs and thick, overpressure mudstone with strong vertical sealing ability provided favorable storage space and preservation, respectively. Using the model, an integrated Archaean metamorphic buried hill condensate gas reservoir, Bozhong 19–6, was discovered in the Bohai Bay Basin. The natural gas reserves are about 450×109 m3, equivalent to oil production of 800 ×106 m3, and signify a breakthrough in natural gas exploration of continental rift lacustrine basins in China.