Gas Discoveries Research Articles

Development prospect of natural gas industry in the Sichuan Basin in the next decade

The Sichuan Basin is the earliest natural gas discovery and utilization area in the world, where China's modern natural gas industry started. Through nearly 7 decades of development, a natural gas industrial system with complete upstream, midstream and downstream industry chain has been established, and its natural gas production has been among the top in China for half a century. And it has played an important role in the process of improving the primary energy consumption structure and constructing a “beautiful China”. The evaluation result of national oil and gas resources in the 13th Five-Year Plan shows that the natural gas resource extent in the Sichuan Basin is 39.94 × 1012 m3, ranking the first in petroliferous basins of China. In addition, the proven rate of natural gas resource is only 15% and it is still in the early and middles stages of exploration. Therefore, the Sichuan Basin has great potential in natural gas exploration and development. The natural gas production in the Sichuan Basin in 2020 is 565 × 108 m3 (including all production enterprises of PetroChina and Sinopec in the Sichuan Basin), taking the first place in China major gas producing areas. Over the next decade, the China puts forward new development concepts from the perspective of development circumstances. The construction of Chengdu–Chongqing economic circle will be promoted and a national natural gas strategic production base with yearly gas production of 1000 × 108 m3 will be built up in the Sichuan Basin, which marks a new golden development age of natural gas industry in the Sichuan Basin. From the perspective of development potential, deep and ultra-deep marine carbonate gas reservoirs, deep shale gas and continental tight sandstone gas will be the key exploration and development fields to search for giant gas fields in the Sichuan Basin. It is recommended to strengthen core technology researches according to the thoughts of “coordinated development of marine and continental, conventional and unconventional, structural and lithologic” and relying on theoretical and technological progress. In the future, it will enter a booming development period when the quality of natural gas resources will be continuously improved and the production rate will be increased continuously. In the meantime, take advantage of the opportunities of prosperity development to break through the development bottleneck of increasingly complex work objects, incomplete pipeline network system and insufficient high end and high additional value industries. Under the situation of normalized low oil price, construct a new-type industrial system with the coordinative development of natural gas production, transportation, storage and marketing and the innovation and efficiency improvement in the whole industrial chain. It is predictable that the natural gas industry in the Sichuan Basin will start in a new peak growth period and a high-quality development period in the next decade, and its yearly natural gas production will exceed 1000 × 108 m3, and the yearly natural gas production of PetroChina Southwest Oil & Gasfield Company will reach 800 × 108 m3 in 2030. Obviously, the Sichuan Basin will be a world-class natural gas production and supply base.

Interlinkages between Energy Consumption and Economic Growth: A Review, an ARDL Bounds Testing Approach

In this study, we re-examine the discussions on the relationship between energy consumption and economic growth by replicating the autoregressive distributed lag (ARDL) bounds testing framework for Tanzania in Odhiambo [1,2], Journal of Energy Policy, and extending it to Kenya country from 1971 to 2014. We use two proxies of energy consumption (total energy consumption and electricity consumption for each country) and GDP growth rate as a proxy of economic growth for each country. The bound F-test reveal that our results are consistent with Odhiambo [1,2] findings that there is still a stable long-run relationship between each proxy of the energy consumption and economic growth for both Tanzania and Kenya. However, when extending the study to more recent data up to 2014, the results of the causality test are inconsistent with Odhiambo [1,2] findings for Tanzania only while being consistent with Kenya results for both two energy proxies and economic growth. The findings reveal the bi-directional causal relationship between each proxy of the energy consumption and economic growth in both short-run and long-run in Tanzania. Overall, the paper finds that the recent discoveries of the substantial natural gas and significant energy project spur economic growth in Kenya and Tanzania.

INDONESIA’S NATURAL GAS: PRODUCTION, RESERVES, AND CHALLENGES

Recent years has witnessed decline in national oil production at an alarming rates of higher than 10% annually. On the other hand, national gas reserves and production situation is much better even though problems such as unanticipated production shortfall of existing fields and commerciality of new reserves have still to be faced. Analysis on history of production and reserves and comparison between oil and gas discoveries in recent years may lead into a conclusion natural gas may serve as an alternative source for energy and national income in years ahead. However, challenges such as technology, infra-structures, law enforcement, social unrests, tight regulations, and incentives are still day-to-day reality. These challenges need to be addressed appropriately if sustainable gas, and also oil, productions are to be achieved.

The New Approach For Zonal Subdivision Of Pliocene - Pleistocene Nannoplankton Biostratigraphy In Waipoga-Waropen Basin, Papua

Waipoga-Waropen Basin is placed in northern part of Papua on the island of New Guinea. The gas discoveries had been made since 1958 in this basin, however, no economic value of reserves lead to the not producing basin state until this time. The main problem in Waipoga-Waropen Basin is great thickness of Pleistocene sedimentary layers (until 7500m) as product of turbidite system (Wold Barret, 2000). This makes difficulty in well section correlation based on the conventional biostratigraphy since individual layers within that section is being small part of biozone. Many reworked nannoplankton as implication of turbidite deposit are also being complicated aspect in biostratigraphic analysis. The Pleistocene ranges from 1.806 m.a. to 11.550 k.a. It was the most recent episode of global cooling or ice age took place. In nannoplankton biostratigraphy, this age is characterized by the extinction of Discoaster brouweri (Discoaster group) at the bottom and the first occurrence of Emiliania huxleyi at the top. The quatitative nannoplankton investigation of “T” well has been done, and there is evident that its sedimentary section gives the excellent nannoplankton assemblages to subdivide Pleistocene age sediments of Waipoga-Waropen Basin (Zone NN19) into 9 subzones. Biomarkers from the bottom to the top consist of: LO of Discoaster brouweri, FO of Gephyrocapsa caribbeanica, FO of Gephyrocapsa oceanica, LO of Cacidiscus macintyre , LO of Helicosphaera sellii, FO of Reticulofenestra asanoi, FO of Gephyrocapsa parallela, LO of Reticulofenestra asanoi, FO of Helicosphaera inversa and LO of Pseudoemiliania lacunosa. The sediments belong to zone NN 20 that placed in the uppermost part of Pleistocene were not analysed.

A novel method to realize multicomponent infrared spectroscopy gas logging based on PSO-split peak fitting-SVM

The recent introduction of infrared spectroscopy gas logging technology is of great significance for the timely discovery of oil and gas, the prediction of well kicks, the prevention of blowout and gas invasion, and the comprehensive evaluation of reservoirs. However, the accuracy and stability of the current quantitative analysis methods for gas logging measurement data are limited by the severe overlap of infrared absorption spectra and the difficulty of sample preparation. In this paper, a novel hybrid method based on particle swarm optimization split peak fitting and a support vector machine (PSS) is presented to address this issue. The method uses a single peak that satisfies a specific absorption line to fit the mixed spectrum and classifies and identifies the parameters of a fitted single peak to complete the “mathematical separation” of the overlapping spectrum. The IR spectral data of 761 samples for methane, ethane, propane, n-butane, iso-butene, n-pentane, iso-pentane and carbon dioxide were collected for quantitative analysis experiments. Repeated comparison experiments of different feature extraction methods under the same partial least squares (PLS) regression method show that the PSS model established with fewer samples still has better analytical accuracy and stronger robustness. At the same time, PSS can significantly improve the model accuracy under different regression methods to a similar level, reducing the dependence on regression methods. PSS combined with PLS can simultaneously measure the contents of eight components in a multicomponent mixture, and the predicted average root mean square error is 0.7242% for 60 mixed experimental gas samples and 0.2534% for 3 industrial standard gas samples. The proposed method has a high practical application value for popularizing IR spectroscopy gas logging technology and provides a new concept for the quantitative detection of substances with high molecular similarity.

E&P Notes (March 2022)

E&P Notes (March 2022)

Hydrogen-rich gas discovery in continental scientific drilling project of Songliao Basin, Northeast China: new insights into deep Earth exploration

Hydrogen-rich gas discovery in continental scientific drilling project of Songliao Basin, Northeast China: new insights into deep Earth exploration

Discovery of a Damped Lyα Absorber Originating in a Spectacular Interacting Dwarf Galaxy Pair at z = 0.026

Abstract We present the discovery of neutral gas detected in both damped Lyα absorption (DLA) and H i 21 cm emission outside of the stellar body of a galaxy, the first such detection in the literature. A joint analysis between the Cosmic Ultraviolet Baryon Survey and the MeerKAT Absorption Line Survey reveals an H i bridge connecting two interacting dwarf galaxies (log (M star/M ⊙) = 8.5 ± 0.2) that host a z = 0.026 DLA with log[N(H i)/cm−2] = 20.60 ± 0.05 toward the QSO J2339−5523 (z QSO = 1.35). At impact parameters of d = 6 and 33 kpc, the dwarf galaxies have no companions more luminous than ≈0.05L * within at least Δv = ±300 km s−1 and d ≈ 350 kpc. The H i 21 cm emission is spatially coincident with the DLA at the 2σ–3σ level per spectral channel over several adjacent beams. However, H i 21 cm absorption is not detected against the radio-bright QSO; if the background UV and radio sources are spatially aligned, the gas is either warm or clumpy (with a spin temperature to covering factor ratio T s /f c > 1880 K). Observations with VLT-MUSE demonstrate that the α-element abundance of the ionized interstellar medium (ISM) is consistent with the DLA (≈10% solar), suggesting that the neutral gas envelope is perturbed ISM gas. This study showcases the impact of dwarf–dwarf interactions on the physical and chemical state of neutral gas outside of star-forming regions. In the SKA era, joint UV and H i 21 cm analyses will be critical for connecting the cosmic neutral gas content to galaxy environments.

Delineation of Subsurface Structures Using Gravity Data of the Shallow Offshore, Lamu Basin, Kenya

Lamu Basin is located in South Eastern Kenya and covers about 170 000 km2 both onshore and offshore. Kenya’s Lamu Basin is hitherto underexplored even though there have been notable oil and gas discoveries along the margin of East Africa. This study focuses on the shallow section of the Lamu offshore bounded by 39°E to 43°E by 2°S to 6°S, whereby, unfortunately, some of the wildcat wells turned out to be dry although expensive. Gravity interpretation techniques such as spectral analysis and first horizontal derivative were applied to the reduced gravity data to delineate and model structures to minimize the high investment risks. The gravity data used in this study were sourced from the International Gravity Bureau (BGI) and National Oil Corporation of Kenya (NOCK) digital data courtesy of companies like Woodside Energy, Anadarko Kenya Limited, and Total Exploration and Production companies. The obtained reduced gravity data were gridded to produce the gravity anomaly grids (Free air, Bouguer, and Isostacy), which were consequently drawn into maps. From spectral analysis, depths to shallow sources and deep sources were estimated. These depths were used to set regional and residual separation filters using the Gaussian filter. The first horizontal derivative (FHD) applied to the regional Isostatic gravity anomaly map yielded features that were inferred as intrasediment fractures/faults trending in NW-SE and NE-SW directions. The features like the ridges, troughs, and faults mainly trending in the NW-SE direction are discernable from the regional anomaly map. The developed models show the basement highs and lows with a possibility of anticlinal and synclinal structures and thick sedimentary successions likely to represent good hydrocarbon source kitchens.

Community perspectives on natural gas management in Tanzania

Several studies have discussed community participation in socio-economic projects. The studies have shown that many projects that have been initiated by either the government or private sectors have encountered resistance and reluctance from the local communities and other officials due to lack of prior and continuous involvements, poor dissemination of information on the significance of the projects, and differences in priority and interests. One of the key factors for the success and sustainability of any project is a clear understanding of the community's voluntary involvement, perspectives, and expectations of the given project. This study, therefore, aims to analyze the communities’ perspectives, expectations, and concerns related to the recent discovery and management of natural gas in Tanzania. The study adopted a questionnaire survey. Data was collected from the 115 respondents from local communities of Lindi and Mtwara regions in Tanzania. The study revealed that the communities are aware of the natural gas discoveries and policies and laws related to them. It shows that a small number of employment opportunities have been created and/or are expected to increase in the future. There should be transparency and accountability in the natural gas development, contracts, and agreements. The parliament should be the most trustworthy custodian of natural gas revenues. The study revealed that the natural gas sector would enhance the living conditions of Tanzanian households and support the attainment of the country's socio-economic development.

KTaO3 -The New Kid on the Spintronics Block.

Long after the heady days of high-temperature superconductivity, the oxides came back into the limelight in 2004 with the discovery of the 2D electron gas (2DEG) in SrTiO3 (STO) and several heterostructures based on it. Not only do these materials exhibit interesting physics, but they have also opened up new vistas in oxide electronics and spintronics. However, much of the attention has recently shifted to KTaO3 (KTO), a material with all the "good" properties of STO (simple cubic structure, high mobility, etc.) but with the additional advantage of a much larger spin-orbit coupling. In this state-of-the-art review of the fascinating world of KTO, it is attempted to cover the remarkable progress made, particularly in the last five years. Certain unsolved issues are also indicated, while suggesting future research directions as well as potential applications. The range of physical phenomena associated with the 2DEG trapped at the interfaces of KTO-based heterostructures include spin polarization, superconductivity, quantum oscillations in the magnetoresistance, spin-polarized electron transport, persistent photocurrent, Rashba effect, topological Hall effect, and inverse Edelstein Effect. It is aimed to discuss, on a single platform, the various fabrication techniques, the exciting physical properties and future application possibilities of this family of materials.

Piping Away Development: The Material Evolution of Resource Nationalism in Mtwara, Tanzania

The article explores the evolution of resource nationalism at a local level through the construction of infrastructure. It argues that, in Mtwara, resource nationalism was combined with local perceptions and demands that were shaped through the construction of different forms of infrastructure. The discovery of gas was accompanied by infrastructure in the forms of increased electricity generation and access, improved roads, and construction of new buildings. There were also plans and promises for industrial development utilising gas both as a raw resource in production and as fuel for electricity generation. These provided the confirmation that natural gas was to act as a modernising force for the region and boost economic and social development. Perceptions changed with the confirmation that a pipeline would be constructed to transport gas from Mtwara to Dar es Salaam for electricity generation, causing protests and riots. The completion of the pipeline, combined with the government’s response to the protests, resulted in a change in the perception of what gas can provide for the region. With gas now going to Dar es Salaam, it has also symbolically removed the bedrock of a local gas-based developmental imaginary. Instead, gas has added to the historical grievances that many in the region perceive.

Nanomaterial-based gas sensors: A review on experimental and theoretical studies

Gas sensors play an essential role in various fields such as public safety, environmental monitoring, medical engineering, food monitoring, pharmaceutical industries and clinical diagnostic, to name a few. The need for miniaturized sensors possessing high sensitivity, time response, selectivity, reproducibility, durability, and low cost has driven the discovery of nanomaterials-based gas sensing devices due to their inherent properties such as chemical/physical gas adsorption capabilities and high surface-to-volume ratio. Studies in the literature highlight the development of gas sensors using novel nanomaterials to detect toxic gases. The gas molecules are sensed by the nanomaterial due to adsorption of the gas on the sensor surface, which leads to conductivity change in the nanomaterial. However, the sensing mechanism is quite complicated. Computational studies help the researchers elucidate the physical understanding behind such a complicated mechanism and aid in developing tailored nanomaterials for gas sensing applications. This review outlines different sensor types and the advantages and disadvantages of each sensor for various applications. Different nanostructure-based gas sensors and recent studies are discussed elaborately. The contributions made by theoretical and experimental studies in studying the gas sensing applications of nanomaterials are also discussed.

Multiproxy geochemical characterization of Kommugudem Formation, Krishna Godavari Basin, India: Implication on hydrocarbon potential and shale brittleness

The unconventional reserves are vital future energy resources and globally augmented interest endeavours the discovery of gas and oil‐rich shales. The Kommugudem Formation, Krishna Godavari Basin was evaluated based on sample laboratory and well log studies from six wells deciphering mineralogical and organic geochemical parameters to provide an understanding of hydrocarbon potential and brittleness. Kommugudem Formation constitutes Type III kerogen dominantly with high total organic carbon (TOC) and Tmax indicating the presence of high organic matter. The mean vitrinite reflectance indicates mature to post‐mature shale majorly in the gas generation window. Fourier transform infrared spectroscopy functional group investigation revealed the presence of aromatics and aliphatics with a higher degree of abundance owing to higher TOC content. The basic well logs recorded in the studied region are used to estimate the continuous TOC and porosity of the formation and corroborate with laboratory core data. Petrographic, X‐ray diffraction, and field emission scanning electron microscopy studies revealed the presence of dominantly siliceous mineral matter with relatively lower clay and carbonates. Organic mudstone classification indicates formation is dominantly silica‐dominated lithotype and clay‐rich siliceous mudstone. Microfractures and micropores are observed in mineral and organic matter that may act as storage sites for hydrocarbons. Kommugudem Formation on the basis of mineralogy indicates compositional analogy with brittle zones of Barnett Shale Formation. The high mineralogical brittleness index of the Kommugudem Formation indicates good conditions for hydraulic fracturing. The present investigation demonstrates excellent hydrocarbon generation potential and good brittleness in wells A and B while C, D, E, and F have relatively lower potential and may have low gas and oil sources.

North Africa Builds Back With the Rise of Egypt and East Med Gas

With Europe facing winter gas shortages, North Africa’s role as an energy supplier is in the spotlight, particularly as Algeria’s 1 November closure of the Maghreb–Europe Gas Pipeline to Spain via Morocco further tightens volumes of gas that Europe can import. The International Energy Agency (IEA) projects a 40% drop in Europe’s domestic gas production by 2025 outside of Norway, with the Netherlands and the UK accounting for more than 80% of that decrease. The Netherlands is closing its Groningen field, source of almost half the country’s production in 2019 but also a cause of earthquakes. Its output will be cut by more than 50% to 3.9 Bcm in the year through October 2022, which will be the last year of regular production, according to the Dutch government. The UK cannot seem to offset declining North Sea production despite Total’s 2018 Glendronach discovery in the West of the Shetland Island area and its 2019 Glengorm discovery in the central North Sea with China’s CNOOC. Norwegian production remains flat, averaging 120 Bcm per year over the next 5 years, the IEA reports. And despite the energy policy voiced from Brussels that focuses mostly on renewables, few in the know dispute that gas is and will remain a critical component of the energy transition moving forward for transport, power generation, and as a feedstock to produce hydrogen. North Africa can provide gas—specifically from the Eastern Mediterranean where Egypt, Israel, Cyprus, and Greece are developing a world-class resource base while Cairo positions itself, buoyed by support from the EU and the US, as a regional hub for pipeline gas to Europe as well as LNG and electricity distribution between North Africa, the Middle East, and Europe. North Africa’s Future Shifts From Sand to Deep Water Eni is Egypt’s largest gas producer. The Italian major is active across the North African upstream, investing in new exploration in Libya, Morocco, Tunisia, and Algeria, but its crown jewel is Egypt’s Zohr gas field in which it has a 50% operator interest and partners with Russia’s Rosneft (30%), BP (10%), and Abu Dhabi’s Mubadala Petroleum (10%). The Zohr gas field is located in the Shorouk concession which Eni holds under a production-sharing agreement with Egypt. Situated 190 km north of Port Said, Zohr is Egypt’s largest-ever gas discovery and the largest-ever discovery in the Mediterranean Sea. Eni brought Zohr’s gas on stream in record time, 2 years after the field’s initial discovery in 2015, according to the company’s website. Production reached a targeted 2.7 Bcf/D in August 2019, nearly 5 months ahead of plan, due to the swift completion of eight land-based treatment units including those for sulfur removal, as well as the commissioning of three wells and a second 30-in., 216-km-long gas pipeline to join underwater production facilities to the land-based treatment plant, Eni reported. Eni’s 2020 plan included drilling of two more production wells to boost gross capacity to 3,200 MMscf/D and the upgrading of subsea facilities and onshore treatment.

Israel's Trade Alliances Strategy: Enjoying the Best of All Worlds

This article revisits Israel's trade and political alliance with the European Union – its major trade partner. The article examines the position calling to water down Israel-EU trade relations, considering EU's insistence on linking economic benefits with political advancement in the region, insights gained by the COVID-19 pandemic and substantial recent regional developments: Israel's trade diversification policy, the conclusion of Abraham Accords and the discovery of gas in the Eastern Mediterranean basin. Concluding that such a strategy may not serve the parties' interests best, the article explores ways to leverage these developments to further enhance EU-Israel partnership.

Five Decades Of Petroleum Exploration And Discovery In The Malay Basin (1968-2018) And Remaining Potential

Since the first oil discovery in the Malay Basin in 1969, more than 700 exploratory wells have been drilled. To date, there are more than 181 oil and gas discoveries, about half of which are currently in production and about a dozen are already in their secondary or tertiary recovery stages. In 2014 it was estimated that a total of over 14.8 billion barrels of oil equivalent (bboe) of recoverable hydrocarbon resource have been discovered in the basin, contributing to approximately 40% of the total hydrocarbon resources of Malaysia. By the end of the first decade of exploration in 1979, all the major basin-centre anticlinal structures had been tested. This play type contributed 60% of the total discovered resource in the basin. By 1981 this most prolific play type had been practically exhausted, as all the giant fields (those with recoverable resource > 0.5 bboe) had been found. As “creaming” of the basin-centre anticlinal play continued into the early 1980s, exploration efforts gradually shifted to the newly discovered western margin play types, particularly in the Western Hinge Fault Zone, Tenggol Arch and the adjacent Penyu Basin. There was a “lull” period from 1985 to about 1990, due to the global oil crisis, after which exploration was rejuvenated through significant discoveries in several play types on the northeastern ramp margin. This followed a successful drilling campaign that lasted until around 1997 and contributed an additional ~1 bboe of recoverable resources over a seven-year period. Since then, most of the incremental resource addition came from the highly gas-charged play in northern region that comes under the Malaysia-Thai Joint Development Area (JDA) and on the northeastern ramp margin, which includes the Commercial Arrangement Area (CAA) between Malaysia and Vietnam. Individually, however, the hydrocarbon volumes in these later discoveries were relatively small compared to the earlier discovered play types. Subsequently, new play types were pursued, including stratigraphic channels, deeper reservoirs beneath existing fields, high pressure/high temperature (HPHT) reservoirs, overpressured and tight reservoirs, and fractured basement reservoirs. All had some measure of success but none were able to volumetrically match the discoveries made decades earlier. As of end of 2018, over 2100 exploration and development wells had been drilled in the entire basin. Based on the creaming curve, since around 1990 and into the fifth decade of exploration, the incremental resource addition has been increasing steadily at an average rate of ca. 120 MMboe per year. The data indicate that the expected average discovery size would be less than 25 MMboe, and that at least 5 wells need to be drilled per year to sustain the same rate of resource addition. If no new plays are explored and no significant discoveries made, resource addition is expected to plateau beyond 2020. The basin needs a new stimulus, and more importantly, new exploration play concepts to sustain exploration business.

Research on quantitative analysis method of PLS hydrocarbon gas infrared spectroscopy based on net signal analysis and density peak clustering

As an important part of integrated logging, gas logging can directly measure the content and composition of hydrocarbon gas in the formation, and plays an irreplaceable role in the discovery and evaluation of oil and gas while drilling and real-time drilling parameter monitoring. Traditional gas logging uses chromatographs to analyze downhole gas. However, due to its long measurement period, many additional instruments, long lines, strict environmental requirements, complex operations, and easy distortion, it has been difficult to meet the requirements of current exploration work in complex oil and gas reservoirs. With the advantages of fast analysis speed, rich detection parameters, short delay time, good stability, and strong anti-pollution ability, the quantitative infrared spectroscopy technique can replace chromatography for hydrocarbon gas measurement. However, when it is used for the quantitative analysis of downhole hydrocarbon gases, a large span of absorption spectra and overlapping characteristic peaks can occur due to the complexity of gas components, making quantitative identification more difficult. To address the above problems, this paper proposes a method of net signal analysis (NAS) combined with density peak clustering (DPCA) for local PLS modeling. The method first obtains the net signals of the unknown and correction samples by the net signal analysis and then clusters the net signals by DPCA to select the corresponding local correction for PLS modeling prediction. The experimental results show that the NAS-DPCA-PLS method proposed in this paper is significantly better than the traditional method in the quantitative analysis of hydrocarbon mixed gas components, and the average accuracy of mixed component prediction reaches more than 98%, which effectively improves the detection accuracy of quantitative analysis of mixed component infrared spectroscopy and provides important theoretical support for the use of infrared spectroscopy in gas logging.

Hydrocarbon accumulation in an active accretionary prism, a case study in the deepwater Rakhine Basin, Myanmar offshore

The Rakhine Basin, Myanmar offshore has remained unproductive for a long time. The discovery of biogenic gas in 2004 and the followed dry wells in 2007 have made the exploration in this area more complicated. 2D/3D seismic data newly acquired after 2007 has been interpreted, distributions of anticline structures and turbidite channels have been mapped. Combined with the newly drilled well data and the regional geological setting analysis, a model for hydrocarbon accumulation has been established. We show that under deep-water environment and due to the thick sedimentary volume, neither the turbidite channels, nor the anticline structures can accumulate hydrocarbon alone. Only if turbidite channels pass across the anticline structures, hydrocarbons from the deep sour rocks will migrate upward through conduits to the anticline traps and fill into the turbidite sands overhead to form hydrocarbon reservoirs. The intersections of the turbidite channels and the anticline structures should be the main targets for future gas exploration in the deep-water Rahkine Basin, offshore Myanmar.

Seismic interpretation, reservoir characterization, gas origin and entrapment of the Miocene-Pliocene Mangaa C sandstone, Karewa Gas Field, North Taranaki Basin, New Zealand

The Karewa gas discovery highlighted the potential for commercial gas accumulations in the shallow Miocene-Pliocene stratigraphic horizons, thus changing the exploration strategy in Taranaki Basin, New Zealand. The gas origin, its entrapment mechanism, and the petrophysical characteristics of the Miocene-Pliocene Mangaa C sandstone reservoir have been evaluated. Organic geochemical analyses of Mangaa and Giant Foresets shales bounding the sandstone reservoir point to their immaturity (Tmax< 426 °C) and poor capability for thermogenic hydrocarbon generation. Karewa gas displays an isotopic pattern of δ13C1 ≫ δ13C3 > δ13C2 reflecting its biogenic origin with no signs of thermogenic input. Additionally, the depleted δ13C1 (of range −61.32% to −61.02%) and δDC1 values (of range −183.5% to −182.3%) support its microbial origin likely by bacterial carbonate reduction and degradation of the organically-bound CO2 to form methane. Shales of the Giant Foresets and Mangaa formations contain, and therefore contain abundant organically-bound CO2.Karewa prospect as a roll-over structure bounded by listric faults forming a four-way dip closure. These faults are the gas migration paths from Mangaa and Giant Forests shales to the Mangaa C sandstone reservoir. Excellent petrophysical reservoir characteristics of Mangaa C sandstone (visual porosity av. 20.7%, helium porosity from core av. 30.2%, shale volume av. 6.4%, and water saturation av. 34.5%) prompted its gas potential with high hydrocarbon saturation (av. 65.5%). Mild mechanical compaction and low content of authigenic mineral phases aided in the preservation of the primary intergranular porosity. Seal capacity analysis of the Mangaa C system confirmed the efficiency of the overlying mudstones to seal a thick gas column (up to 150 m) with a minimal risk of leakage.