The Hexiwu buried-hill zone is a major hydrocarbon accumulation in the Langgu sag in northern Jizhong depression, where no new breakthrough has been made since three small Ordovician buried-hill reservoirs (Bieguzhuang, Liuqiying, Liuqiying West) were discovered in the south during the early exploration stage. Pertinent and deep study was conducted on the structure and reservoir characteristics that constrains the hydrocarbon accumulation in the Ordovician heterogeneous carbonate buried-hill reservoir, as well as reservoir stimulation and other major techniques. Through the merged 3D seismic prestack depth migration (PSDM) processing and precise structure interpretation, the zonal structure framework was ascertained, and accordingly the Yangshuiwu buried-hill structure comprising three local highs was discovered. Analysis was made on the Ordovician sedimentary facies and reservoir characteristics, indicating that the dolomite flat and dolomitic lime flat are favorable sedimentary facies belts within the study area, and the reservoir development is jointly controlled by rock type, fracture distribution and karstifcation. The dolomite serves as major reservoir. Through the study of hydrocarbon supply conditions, tectonic evolution and its control on hydrocarbon accumulation, and reservoir-cap rock assemblage, a new model of massive-laminar complex buried-hill accumulation was established for the Ordovician carbonate heterogeneous reservoir within the Hexiwu buried-hill zone. Guided by the new study results, a risk exploration well, Antan 1X, was deployed at the structure high in the west of Yangshuiwu buried-hill. This well revealed a high yield of 40.89×10⁴m³ gas and 71.16 m³ oil per day in the Ordovician reservoir, marking a signifcant breakthrough in ultra-deep and ultra-high temperature Ordovician buried-hill exploration in the north of Jizhong depression. Moreover, the practice exhibits the promising exploration prospect in this domain.

Slope is a major structural unit of fault lake basin in eastern China, and also an important zone in the Bohai Bay Basin for increasing oil and gas reserves. Through years of comprehensive studies and exploration practices in slopes, it is newly proposed that the slopes (or large gentle slopes) show a high-moderate-low differentiation. To be specifc, the geologic differentiation of high, moderate and low slopes in subsidence rate, sedimentary sequence, reservoir physical property, hydrocarbon generation and evolution, formation pressure, fluid property and reservoir type results in the theory of hydrocarbon enrichment in dominant facies belts in slope of fault lake basin. Essentially, in high slope, channel/trough controls sand, and oil and gas enrich in dominant migration and preservation facies. In moderate slope, slope break controls sand, and oil and gas enrich in dominant structural-lithologic facies. In low slope, distal fan controls sand, and oil and gas enrich in dominant source-reservoir coupling facies. According to this theory, fne exploration and drilling operations have been carried out in the slopes. As a result, remarkable achievements were made in stratigraphic-lithologic reservoirs in the slope zone. During the past fve years, additional 3P oil reserves exceeded 3×10⁸t, and four 10 million-ton class proftable productivity construction blocks and three 100 million-ton class blocks with the potential of signifcant reserves increased. Thus, it is demonstrated that the theory of hydrocarbon enrichment in dominant facies belts in slope plays an important role in directing the large-scale proftable reserves increase and high effcient productivity construction.

The Enping Formation is the main source rock that has been proven in deep water area of the Baiyun sag, the Pearl River Mouth Basin. Understanding its sedimentary evolution and key controlling factors is essential for oil and gas exploration in the Baiyun sag. Through comprehensive analysis of wells, cores, seismic data and palaeo-biology, it is believed that the "source to sink" system apparently varied during different sedimentary stages of the Enping Formation. During the early-middle sedimentation stage, the main provenances were the Mesozoic igneous rocks in the uplift areas around the Baiyun sag. during the late sedimentary stage, the source materials were carried by the ancient Pearl River into the Baiyun sag from the South China fold belt as the principal migration pathways in the north of the sag were gradually opened. Correspondingly, proximal small braided delta, fan delta and beach bar dominated by paleo-troughs were deposited in the Baiyun sag during the early-middle sedimentation stage of the Enping Formation, and large continuously-transgressive coal delta was deposited during the late sedimentation stage. The variation of "source to sink" system dominated the plane distribution of the Enping Formation near-shore coal measure, far-shore terrestrial marine and closed bay marine source rocks, and controlled the dispersed distribution of coal-measure source rocks during the early-middle stage and the vertical diversity of extensive development during the late stage. Moreover, the variation of "source to sink" system allowed for the development of lithologic-stratigraphic targets that were mainly derived from proximal fan delta, braided channel complex and beach bar during the early-middle sedimentation stage, and the lithologic-stratigraphic targets dominated by delta-front transgressive complex sand bodies during the late stage.

Previous understandings on types, evolution rules and formation mechanisms of the Yanchang Formation microfacies in delta estuary of the Ordos Basin are different. In this paper, a systematic study was conducted on microfacies of Chang 4+5 pay zone in Fanxue area of the Ordos Basin and its formation mechanisms based on core and well logging data. The study provides the following conclusions. First, the study area is dominated by distributary channel, mouth bar and interdistributary bay in terms of microfacies. Second, the sedimentary model for the Fuxue area with co-existence of rivers and bars is established according to the microfacies distribution in key layers, and thin blanket mouth bars and narrow zonal distributary channels were mainly developed during the early sedimentation stage of Chang 4+5 pay zone, while thick bulk mouth bars and wide zonal distributary channels during the late sedimentation stage. Third, a semi-quantitatively statistical analysis was carried out on the spatial forms of mouth bars using the data of dense well pattern. Fourth, it is concluded after analysis on main controlling factors for evolution of sedimentary microfacies that, due to the sustained falling of the sedimentary base level, the autogenetic cycle processes of distributary channels, such as bifurcation, convergence and lateral migration, were intensive to constrict the lateral growth of mouth bars, thereby resulting in a reciprocal relationship between mouth bars and distributary channels. Fifth, more attentions should be made to the mouth bar sand bodes which are predominant reservoir beds in the delta front.

In recent years, PetroChina Southwest Oil & Gas Field Company has successfully applied the horizontal well volume fracturing technology in tight sandstone reservoir in the 1^st member of Shaximiao Formation ("Sha 1 Member") of Middle Jurassic to promote the exploration and development of tight sandstone oil and gas. Taking the Sha 1 Member reservoir in Gongshanmiao area (which has the best exploration and development benefts) as an example, according to the research approach of tight oil and gas and the source-reservoir confguration, the Sha 1 Member reservoir is divided into two types of exploration and development domains: (1) tight oil and gas in sheet sandstones at the bottom; and (2) conventional distal oil and gas in channel sandstones in the middle-lower parts. According to comprehensive analysis, the sheet sandstones at the bottom of the Sha 1 Member have better hydrocarbon accumulation conditions than the channel sandstones. Controlled by sedimentary microfacies, such sheet sandstones are thin, but they are widely distributed with better physical properties, superior source-reservoir confguration, high oil and gas flling degree and large hydrocarbon-bearing area. Thus, these sheet sandstones are worthy of large-scale benefcial development by the horizontal well volume fracturing technology.

It is disputable about whether the eastern provenance exists for the Pinghu Formation in the Xihu sag. Its clear answer will be signifcant for hydrocarbon exploration. Based on drilling, seismic, and test data, the Pinghu Formation sediments were analyzed in respect of ZTR index of heavy minerals, sandstone types, debris composition, sandstone content, seismic facies and syndepositional structural features. It is found that the ZTR index of terrigenous heavy minerals and the maturity of sandstone components in the Pinghu Formation are "low at both sides of the sag and high in the middle", while the contents (or percentages) of siderite (an authigenic heavy mineral) and sandstone are "high at both sides of the sag and low in the middle". According to seismic reflection features, the Pinghu Formation has apparent chaotic reflections at basin margin and prograding reflection confguration that indicates the existence of the eastern provenance. Moreover, the existence of growth anticlines during middle-late stage of the Pinghu Formation further proves, from the prospective of tectonic stress, that there was an eastern folded and uplifted belt during the sedimentation of the Pinghu Formation. It is concluded that the eastern folded and uplifted belt had already uplifted and become the eastern provenance during the sedimentation of the Pinghu Formation. The deep Pinghu Formation in central and eastern parts of the Xihu sag has good hydrocarbon exploration prospect.

Many scholars have made detailed studies and discussions on the types of sedimentary facies in the Shawan Formation, the major oil-generating formation in the Chunguang block, but their achievements and recognitions are inconsistent. On the basis of outcrop section and drilling core observation, together with the rock color, sedimentary structure and other facies markers, it is derived that the Shawan Formation is of the braided river delta-lake sedimentary system. According to shapes of wireline logging curves and seismic attribute analysis, the sedimentary microfacies are identifed as braided channel, and underwater distributary channel at the braided river delta front. Statistical analysis on the features of lithologic traps at the oil-producing point indicate that the underwater distributary channel sands at the braided river delta front serve as the major reservoir, and the depositional pattern is summarized as the underwater distributary channel sands at the braided river delta front as reservoir with lateral phase-transition seal. According to this pattern, the prospective targets are selected within the study area, and the underwater distributary channel sands at the braided river delta front in S2 sand group of Shawan Formation within the study area is considered as Type I target zone for the following exploration.

The natural gas in the deepwater L Gasfeld in the South Gabon Sub-basin is characterized by abnormally heavy carbon isotopic compositions, with δ¹³C₁ and δ¹³C₂ ranging from -32.8‰ to -28.4‰ and from -25.8‰ to -23.4‰, respectively. According to the ethane carbon isotope criterion of natural gas, the natural gas in the L gasfeld is classifed as coal-type gas. The investigation on regional source rocks and hydrocarbon resources shows that this area is geologically unqualifed for the formation of large coal-type gas felds, since sapropel type oil source rocks are mainly developed while humic gas source rocks are poorly developed. Carbon isotope analysis reveals that abnormally heavy carbon isotopic composition occurs during the Cretaceous Barremian Stage in the Gabon Basin and its neighboring areas, especially in the Melania Formation lacustrine good source rocks. This is similar with abnormally heavy ethane carbon isotope of natural gas in the L gasfeld. Gas source analysis indicates that the natural gas in the L gasfeld is mainly derived from high-over maturity oil cracked gas which is generated by the Cretaceous sub-salt lacustrine source rocks. In particular, the lacustrine source rocks of Barremian Melania Formation are dominant.

The principal petroliferous basins in Japan are typical fore-arc basins and back-arc basins. They have complex geological structures that were formed under the joint effects of the tectonic movements of Pacifc Plate, North America Plate, Philippine Sea Plate and Eurasian Plate for a long time. In this paper, these principal petroliferous basins were investigated from the aspects of tectonic setting, sedimentary characteristics and development data. It is shown that the structural evolution of these basins can be divided into four stages, i.e., subduction, basin development, subsidence and compression deformation. The subsidence stage in the Miocene of Neogene is the key period for hydrocarbon generation. The oil and gas discovered are mainly preserved in structural traps, lithologic traps and complex traps of Neogene, as well as the basal fractured reservoirs of pre-Neogene. The oil and gas are horizontally scattered and vertically inhomogeneously distributed. The hydrocarbons in the study area were mainly accumulated in three patterns, i.e., vertical migration-fracture pathway, lateral migration-slope pathway, and self generation-self preservation, with the predominance of vertical migration hydrocarbon accumulation. Plays were taken as evaluation units. Eight plays in the petroliferous basins of the study area were analyzed from the aspect of resource potential. It is indicated that the Niigata Basin, the Kanto Basin, the Gyeongs Basin and the Kitakami Basin are the major oil and gas exploration areas within Japan in the future.

Many studies have been conducted on conventional oil and gas in the Sanshui Basin, but insuffcient efforts have been made on unconventional oil and gas, especially shale gas. In this paper, based on the structural and regional sedimentary settings, and using multiple techniques such as outcrops observation, samples testing, and scanning electron microscope (SEM), the distribution, organic geochemical features and reservoir properties of the Palaeogene Buxin Formation dark shale were investigated to identify the accumulation conditions in this area. It is shown that the Buxin Formation shale was developed under the control of lacustrine sedimentary environment during the formation of the lake basin, with consistent depocenter and subsidence center, shale thickness of about 50-70 m (58 m on average), and burial depth of about 500-3000 m, which are favorable for preservation of organic matters. Dominated by Type Ⅱ-Ⅲ kerogens, the Buxin Formation shale is in the maturity stage, with TOC of 0.56%-3.29% (1.25% on average) and Ro of 0.71%-1.94% (1.31% on average), indicating that it is basically qualifed for gas accumulation. Microscopically, micropores in authigene clay minerals are dominant, with the pore-throat radius of 1-8 μm, and total pore space is developed, providing effective reservoir space for shale gas. The Buxin Formation can be divided into three members from the bottom to the top. The 2^nd Member composed of deep lacustrine sediments was deposited during the period when dark shale in the basin was formed and has the most favorable organic geochemistry parameters, relatively good reservoir properties, and greatest hydrocarbon generation potentials. In contrast, the 3^rd Member and 1^st Member have inferior properties in a descending order.

The Fula sag in the Muglad Basin is a hydrocarbon-rich sag in a passive continental rift basin. Currently, its exploration focuses on lithologic traps. According to the "sag-wide oil-bearing theory" and the "tectonic-sequence zone accumulation theory", the matching relationship among structures, sedimentations, effective source rocks and migration conditions in third-order sequences of Fula sag was analyzed comprehensively by means of "four-map overlying" play evaluation method for lithologic reservoirs. Then, combined with existing oil and gas discoveries, the favorable plays of lithologic reservoirs in the Fula sag were predicted. It is indicated that AG2 Member of Abu Gabra Formation is the most favorable interval for the development of lithologic reservoirs, and the fan delta front within the Jake area is currently the most favorable lithologic reservoir exploration zone, followed by the meandering delta front within the Baleela area and then the meandering delta front within the Moga area. The lithologic reservoirs at the upper wall of fracturing slope break belt in the Fula area are limited in exploration potentials.

In the Tarim River area within the Taklimakan desert, the Tarim Basin, the ideal time for feld seismic survey is the frost period dating from December to next January or February. When the wide azimuth 3D seismic survey was conducted within the Well YML2 South 3D area in 2014, the break-up period during February arrived in advance. The width, boundary and phreatic surface elevation of the Tarim River varied dramatically. During the break-up period, as the climate changed greatly, the Tarim River transgressed and regressed frequently, while breaking-up and freezing usually alternated, leading to the varying coverage and number of shot point and receiver point flooded. As a result, the seismic survey across the Tarim River could not be carried out as it was previously designed. With consideration to the fact that the changing hydrogeologic conditions during the break-up period have adverse impacts on the seismic survey, the operation scheme was updated or adjusted. The high precision remote sensing information technology was applied to trace and understand the variation of hydrogeologic conditions in real-time manner. According to the thought and method of initial dynamic design and rolling optimal design for observation system, the shot points and receiver points in the Tarim River hazard were timely migrated, resumed or increased, and fne seismic operation was organized orderly, in order to ensure the normal parameters during the frost period. The application results show that high-resolution wide azimuth 3D data with high S/N ratio were acquired.

As the exploration and development spread to deep subtle reservoirs, the palaeo buried-hill reservoir becomes one of the major targets. The Hejian buried-hill inside is characterized by large depth, complicated structures and low S/N ratio, which brings about great challenges to the precise imaging and structure confrmation of the buried-hill inside. This paper presented the basic principle of reversetime migration based on the two-way wave equation, including higher-order fnite difference wave feld extrapolation algorithm and perfectly matched layer absorbing boundary conditions. After the characteristics of the Hejian buried-hill inside were analyzed, the reverse-time migration and traditional pre-stack depth migration were used to process the model data and actual data. The results show that the reverse-time migration can realize precise imaging of the Hejian buried-hill inside, with better performance than the traditional method.

In order to achieve unrestricted fracturing stages and consistent and intelligently controllable sliding sleeves in all stages, a sliding sleeve control system is designed on the basis of radio frequency identifcation (RFID) technology. When the RFID tag ball passes through the fracturing string, the stored data is sent to the downhole through the coupling between in-built antenna and reader antenna. The reader sends a command signal to the electronic control unit according to different settings after receiving the carrier signal. The electronic control unit drives the hollow-shaft motor to rotate, and the hollow-shaft motor realizes accurate commutation through the Hall signal, so that the openness and opening/closing of sliding sleeve is intelligently adjusted. An experiment was conducted on the bench to verify the reliability of the system.