In the Chang-7 member of YanChang Formation in Ordos Basin, the tight sandstone reservoir is inter-bedded with or adjacent to source rock. Its surface air permeability is less than 0.3mD and the oil reserve in the tight sand reservoir is typically tight oil. As of 2014, China^’s first large-scale tight oil field with the reserve reaching 100 million tons – Xin^’anbian Oilfield – has been proven, with three demonstration zones of tight oil horizontal well technology and three pilot zones for large-scale development established. The study indicates a series of favorable conditions for accumulations, such as a wide distribution of high-quality source rock, large-area extension of fine-grained sand body, development of small-size pore with a diameter of 2-8μm, and filling ability for accumulation. Effective combination of those favorable conditions holds the key to large-scale enrichment of tight oil in Ordos Basin. The Chang 7 tight sandstone reservoir is good for engineering quality and crude oil quality and high in dissolved gas content, with a neutral-weak hydrophilic wettability of oil reservoir, thus being in favor of crude oil production. The basin has a great potential for tight oil exploration. Based on a preliminary assessment, tight oil reserve is as high as 20×10⁸t, providing the important resources for the oil field to keep its production stable.

Based on analysis of sedimentation and lithofacies paleogeography of Ordovician Majiagou Formation in the central and eastern part of Ordos Basin, this paper, for the first time, defines the 3rd and 4th sequential stratigraphic configuration of Majiagou Formation and divides Majiagou Formation into three 3rd sequences and 11 4th sequences. The study is focused on lithofacies paleogeographic evolution of the 4th sequences of Ma5, a gas-producing horizon, fully analyzing the controlling role of sedimentary sequences on distribution of dolomite reservoirs. (1) Fluctuations of sea level and ejection of central paleo-uplift caused the differences in dolomitisation – penecontemporaneous dolomite in the regressive period and mixing dolomite in the transgressive period. (2) The differences in dolomitisation led to a vertically cycled distribution of reservoirs with development of gypsum-dissolved dolomite reservoirs in the regressive period and intercrystal pore dolomite reservoirs in the transgressive period. (3) Distribution of reservoirs is controlled by sedimentary facies in the sedimentary sequences. Intertidal gypsum-bearing dolomite flat is the favorable sedimentary microfacies in the regressive sedimentary cycle and intertidal algae-clastic beach is the favorable sedimentary microfacies in the transgressive sedimentary cycle.

Lithologic character is one of the main controlling factors for development of tight oil sweet spot. The Ek₂ layer of Cangdong sag, Huanghua depression, is rich in tight oil resource. To clarify the lithologic development characteristics of fine-grained Ek₂ sedimentation, highresolution sequential stratigraphy and tight oil and gas abundance geological theory are used to make high-resolution sequence stratigraphic division of the Ek₂ layer and analyze its sedimentary characteristics on the basis of coring, testing, logging and well-log data. The study indicates that theEk₂ layer in Cangdong sag is a set of intact three-order sequences, which can be further divided into four-order sequences (SQEk₂ ¹—SQEk₂ ⁴). Fine-grained sedimentation in SQEk₂ ¹ high stand system tract is complicatedly composited without favorable minerals development. It is characterized in extensive distribution of brittle minerals, such as muddy felsites debris and analcite. Four main types of rock developed in the area – shale, dolomite, sandstone and mixed sedimentary rock, of which mixed sedimentary rock developed best. Tight sandstone and dolomite are the main reservoirs. The research results refresh the previous views that shale developed as source rock in finegrained sedimentation of Ek₂ layer in Cangdong sag but no reservoirs developed there, effectively expand the oil and gas exploration field in Cangdong sag.

The ^“2W1H^”(wide-band, wide azimuth and high-density) technique, a high-precision integration seismic exploration technology, presents requirements for matching theoretical concepts and technical processes from field data acquisition to data processing and interpretation. This paper provides basic definitions and technical specifications for the ^“2W1H^”technique, and points out its superior advantages in resolution, fidelity and inversion accuracy based on theoretical records and synthetic records. The technique can be used for description of reservoirs in areas with well-developed thin interbeds, prediction of fractures in areas with high anisotropy, and exploration of deeper targets or formations with special lithologic features. In addition, the technique may be used to enhance quality of structural mapping for formations with complicated structures. Application of the technique in 3 areas proved its importance in exploration, appraisal and development of complex oil/gas reservoirs. By enhancing quality of seismic data, the technique can effectively reflect configurations of complex reservoirs and distribution of fluids therein, so as to promote fidelity of the data.

Offshore oil and gas exploration is a high-risk activity with high investment. Hydrocarbon detection of underlying exploration targets, along with conventional geophysical exploration technology, can remarkably improves offshore oil and gas exploration success rate, deepwater area in particular, and reduces hydrocarbon exploration risk and cost. Based on the hydrocarbon microseepage principle, microbial geochemical exploration (MGCE) detects existence of hydrocarbon reservoirs directly by means of inspecting hydrocarbon oxidation bacterium and light hydrocarbon gas. MGCE is a direct hydrocarbon-detecting technology, which has a wide application in offshore area. In recent years, MGCE has been used for oil and gas estimation of deepwater traps in Qiongdongnan Basin and Pearl River Mouth Basin of South China Sea, achieving good results. The drilling result confirms that MGCE is suitable for oil and gas exploration in the region. MGCE is a flexible, fast and effective hydrocarbon detecting technology worth to be recommended for the central and southern parts of South China Sea, where the exploration degree is low and the risk is high. Large-scale application of MGCE is hopeful to accelerate deepwater exploration process of South China Sea.

Based on the oil and gas field data and basin geological and geophysical data from international commercial databanks, this paper analyzes the hydrocarbon accumulation conditions and exploration areas of deepwater post-salt clastic rock in offshore eastern Brazil. The basins in Brazil’s eastern offshore area experienced three development stages, namely the Early Cretaceous Valanginian – Early Aptian intracontinental rifting stage, the Middle Aptian – Early Albian inter-continental rifting stage, and the passive continental marginal stage after the Middle Albian. Horizontally, the area can be divided into extensional belt, diaper belt and compressional belt. Hydrocarbon of deepwater post-salt clastic rock comes from lacustrine shale from Barremian and marine shale from Cenomanian-Santonian. The source rock is large in thickness and good in quality and physical property, with good reservoir-cap conditions. The sedimentary model of post-salt clastic rock indicates such a dynamic process as the sediments, stayed in the broad continental shelf, is re-transported under triggering conditions and slumped at a number of points. Then turbidite is shaped and laterally and lenticularly distributed in a potato-shaped alignment on the periphery of the continental shelf. The deepwater sedimentary structures are mainly the rootless turbidite channels and lobes while sedimentation of reservoirs is confined and transformed by deformation of salt rock. Hydrocarbon accumulations of deepwater post-salt clastic rock are jointly controlled by source kitchen position, distribution of reservoir sedimentary facies, and deformation of salt rock. The next-stage exploration should be focused on intra-slope ponded-basins on the periphery of continental shelf. The strata of exploration should be expanded horizontally into Eocene and Oligocene – Miocene in Espirito Santo Basin and Oligocene-Miocene in Santos Basin.

The statistical figures about China^’s coal-bed methane (CBM), particularly CBM drained from coal mine and its utilization rate, are very confused. It is not feasible to calculate the nation^’s total CBM output simply by adding CBM drained from coal mines, with low methane content and a large variation range, to the CBM production from wells drilled on the surface. CBM production and utilization should be verified by standard measurement of commodity amount. CBM output and utilization have not reached the target as predicted in recent years. It is necessary to hold a cautious attitude towards the CBM target put forth in the 13th Five-year Plan. Sluggish CBM development resulted mainly from royalty management issues. Some national oil companies^’monopoly of the royalty is overlapped with the royalty of specialized companies and coal enterprises. Inadequate investment from enterprises also seriously impairs CBM development owing to a high CBM cost. To promote a healthy CBM development it is necessary to strengthen structuring reform, deregulate royalty admission, make reasonable the relations between specialized CBM companies and coal mines, and keep comprehensive development of different types of oil and gas on the basis of the law and regulations. In the efforts to reduce development cost, the country should make a multi-disciplinary research on CBM in the light of the Chinese characteristics.

Junggar Basin is rich in coal-bed methane (CBM) resources. The abundance zones and main favorable exploration targets are located in the eastern Urumqi –Baiyanghe area on the southern periphery of the basin. Based on the study of engineering technological adaptability, it is necessary to use the fracturing and renovation process suitable for extraction of CBM in Junggar Basin. Under the present gas price, the drilling depth should be less than 1000 meters according to the study of the single-well CBM production ceiling. The investment in single-well asset should be less than 8 million yuan. Based on the study of the environment, risks and strategy of CBM industrial development, it is concluded that the policy framework of China^’s CBM development and application is preliminarily shaped at the present time with a series of supportive policies released, such as elimination of business exclusive franchise, preferential taxation and financial subsidies. The industry has been on the track of large-scale development. Xinjiang has released a series of favorable policies for CBM industrial development and successfully established ^“the pilot CBM development zone^” in the Baiyanghe area. PetroChina has also emphasized non-conventional oil and gas as an important area in the upstream sector opening to the outside world and formulated the concrete guidance documents on CBM business in Xinjiang, creating favorable policy environment for CBM industrial development in Junggar Basin. To take into account the risks for CBM development performance, a co-funded cooperative CBM exploration pattern is proposed to be the most realistic option for CBM industrial development.