The formation conditions are favorable and hydrocarbon resources are abundant in Shuguang-Leijia area of the western sag of Liaohe Oilfield. Subtle reservoir types are mainly the buried hill reservoirs and the Palaeogene special lithologic reservoirs. Main factors controlling hydrocarbon of subtle reservoirs and their distribution rules in the area are studied systematically with the analysis of the geologic setting. The result shows that the subtle reservoirs in the area are mainly determined by such factors as the structural-depositional environment, valid source rocks, fault surface, unconformity surface and sandbody transporting layers, etc. Formation of the buried hills and special lithologic rocks are primarily controlled by structural-depositional environment. The distribution of subtle reservoirs is horizontally around generating sags. Subtle reservoirs are vertically distributed along by fault surface and unconformity surface. The distribution set of subtle reservoirs is controlled by some main source-reservoir-cap assemblages. Formation models of hydrocarbon accumulations of subtle reservoirs tend to vary in three different tectonic settings including sags and slopes as well as uplifts.

Songliao peripheral basins are characterized by low level unbalanced exploration and complicated geological conditions, but with better resource bases. Because of the different characteristics of strata development and structural evolution of different basins, basins in the area are classified into two categories---successor basins and remnant basins. Moreover it is pointed out that the basins are distributed with regularity. Based on this, the hydrocarbon generation, accumulation, and reservoir-forming conditions of the main basins in the study area are analyzed. Successor basins are proved to have favorable prospects for exploration. At last suggestions of "laying emphasis on succession, strengthening preparatory work for oil and gas exploration, and deepening comprehensive study on Songliao peripheral basins" are proposed. Attention should be paid on deep exploration of successor basins featuring in low level exploration.

Under the guidance of tectonic slope-break theory, the types of tectonic slope-break in Nanmazhuang area of Raoyang Depression of Bohai Bay Basin and relationship between distribution of sand bodies and types are researched by using seismic and well log data. The genetic mechanism of lithologic oil and gas reservoir at tectonic slope-break in this area is also discussed. The results indicate that the types of tectonic slope-break in Nanmazhuang can be divided into three types according to faults basic characteristics and combined style, they are "comb-like tectonic slope-break", "broom-like tectonic slope-break" and "ladder-like tectonic slope-break". Different types have different control on distribution of sand bodies, but as a whole, main faults of tectonic slope-break and direction of sediment influx system determine forming location of sand bodies, and strike of main faults controls stretch direction of sand bodies. The tectonic slope-break zone is favorable and important for the formation of subtle oil and gas reservoir, such as lithologic reservoir.

The Lower Member sandstones in Devonian Donghetang Formation at Qun 6 well are made up of micro fine and fine lithoclastic quartz sandstones. It is a suit of high maturity, low porosity and low permeability reservoirs. The reservoirs have huge thickness and significant heterogeneity. According to the statistics of cores and thin-sections under microscope, the density of dense and semi-dense laminae in the sandstones sometimes attain one hundred or more per meter. The influential factors of heterogeneity in the reservoirs include syndepositional structures, dolomite cementation, filled with heavy bitumen except compaction and dissolution. These factors lead to low permeability and low oil-fluidity in the sandstones. The contents of bitumen and heterogeneity increase obviously from top to bottom the sandstones in Lower Member of Donghetang Formation. The more uniform block sandtones at lower and middle parts are favorable reservoirs

The Cretaceous Shushanhe Formation in Shenmu-1 well in Wushi sag is mainly fine litharenite, pebbly sandstone & sandstone-conglomerate in plain and front channel bed of fan delta. The average porosity of well logging and core analysis is about 9% and the reservoir is characterized by low porosity and low permeability. Observed by microscopic chips, the Cretaceous segment of 5118.8m~5143.05m in Shenmu-1 well has high amount of Carbonate grain, and high content of carbonate debris particles at 5108.05~5117.83m. The Shushanhe Formation with undeveloped pores is mainly dissolution pore, structural fractures and crush fractures develop in thick rocks, which contribute a lot to the productivity of Shenmu-1 well.

Considering the geomorphic feature of the loess area in eastern Ordos Basin where the reservoir is relatively thin, seismic exploration was conducted to suit local conditions in recent years. The straight line method and the crooked line method in valleys were applied, and some exploration results were achieved. To further characterize the distribution of sand bodies, forecast the effective reservoir, and to carry out effective lithological stratigraphic traps, full digital seismic research was launched in loess area of eastern Ordos Basin in 2007 and 2008. First is the seismic acquisition technology characterized by small group, long arrangement, high density, high coverage, and digital geophone single-point reception. Second is the seismic data processing technology characterized by high fidelity and high signal-to-noise ratio to maintain dynamic characteristics. Third is prestack and poststack seismic attribute analysis and reservoir predicting technology which is guided by high-precision stratigraphic sequence. The combination of the three technologies improves the accuracy of reservoir prediction and provides technological support for natural gas exploration and development in the east of the basin.

Electrical characteristics of rock are the basis to carry out electrical prospecting and data processing interpretation. Physical parameters leading to electric anomaly are mainly related to the size of rock resistivity distribution. While analyzing the CEMP data in southern margin of Ordos Basin, it is found that there is great difficulty in tracking the Triassic and Permian by using the same electric combination properties. To solve the problem, statistical analysis is made on the electric logging data of multiple wells in the surveyed area and its surrounding areas, moreover the electric combination and distribution characteristics of different areas of the Triassic and Permian are analyzed and studied. Results show that the same set of strata in eastern and western areas shows different electric properties, i.e. in the eastern area the resistivity of the Triassic is higher than that of the Permian, while in the west the resistivity of the Triassic is lower than that of the Permian. The CEMP profile reinterpreted according to the above law is more objective and reasonable, and the interpretation result conforms to the prediction of geologists. Seismic exploration is deployed on the basis of the CEMP results.

In order to study the propagating rules of pure compress wave and pure shear wave of the hybrid elastic wave field more accurately, the general method is achieved by the operator separation to construct equivalent first-order hyperbolic type elastic wave equation to achieve the elastic wave field separation numerical modeling, which increases not only the computed memory and computed time, but also the computing complexity. In order to solve the above problems, the paper puts forward a quick elastic wave field separation numerical modeling scheme base on staggered-grid and second-order elastic wave equation, according to which the pure compress wave (divergence field) and pure shear wave (curl field) are calculated with layered model and a complex model with solid-fluid. The numerical result shows that this method can correctly separate pure compress wave and pure shear wave from hybrid wave field with high precision and high efficiency, and the paper also indicates the method's inapplicability of the wave on the surface of solid-fluid and so on.

To speed up the exploration of Carboniferous volcanics in the Santanghu Basin and to promote the use of reserves, technological research is conducted to solve the difficulties in volcanic reservoir identification and evaluation of oil/gas/water zones, and the problems of strong reservoir heterogeinity and low natural production. By applying the gas surveying technology, the fluorescence quantitative technology, the gas chromatography logging technology and the elemental capture spectroscopy (ECS) logging technology, the Formation Micro Image (FMI) well logging technology, the difficulties in volcanic reservoir evaluation are solved effectively. Seismic reflection characteristics of high-quality volcanic rock reservoirs are studied and the distribution range of high-quality reservoirs are delineated with high accuracy. Based on the optimization of stimulation technologies of volcanic reservoirs, the emulsion fracturing systems is worked out, and it shows good compatibility with the volcanic reservoir in weathered zone that has strong water sensitivity. The system demonstrates satisfying fracture-stimulation effect. The application of new technologies effectively promote Carboniferous exploration, production of the third-level reservoir of the Carboniferous Kalagang Formation exceeds 100 million tons within two years, and a block with high quality reserves is therefore formed.

According to the data of geology, geochemistry and geophysics, the migration and accumulation units of a sag in northern Bohai Bay Basin are divided and assessed. There are two reservoir formation dynamic systems in the Bohai Bay Basin. The analytical hierarchy process is used to assess the migration and accumulation units of the two dynamic systems from the four aspects of hydrocarbon generation and expulsion, accumulation, migration and preservation. The result shows that No.5 unit in the shallow dynamic system has the best hydrocarbon accumulation; No.5 unit in the deep dynamic system has the best hydrocarbon accumulation, while No.2 and No.3 units take the second place

Coal seam reservoir conditions and development technologies are the major factors that influence China's CBM recovery. CBM recovery can be increased by improving drilling and completion technologies and stimulation technologies. Some shortcomings of commonly-used drilling and completion technologies, fracturing technologies, and gas injection technologies are analyzed, it is believed that the short radius radial horizontal well technology has the function of completion and stimulation and it can increase the single-well productivity substantially. The high-energy gas fracture technology can improve the reservoir conductivity and protect coal reservoir, decrease contamination to coal reservoir caused by water sensitivity, and reduce costs. The gas concentration and flow rate before and after gas injection change with time, indicating that gas mixture enhanced CBM recovery (G-ECBM) has obvious effect.

The economic evaluation of oil & gas play is an important work tache of resource evaluation, exploration plan and decision making for stock companies, and have important significance to frame exploration deployment and to program the middle-long term exploration planning. The new method of evaluation of oil & gas play in the sea, named the dynamic simulation of exploration and development full cycle, is put forward. The new model and evaluation system have been established, according to the characteristic of the oil & gas exploration and development in the sea, contra posing to the main risk factors and the resource distribution characteristic of the oil & gas play, integrating with development and engineering model. The evaluation thoughts, main process and technology traits of the method are introduced in the article. The example indicates favorable applying result.

Comprehensive study of global oil and gas geology and related evaluation have not yet been systematically launched in China. Overseas petroleum exploration and development has nothing to refer to, as compared to domestic petroleum exploration and development which can learn from historical experience and lessons. In order to carry out overseas petroleum exploration and development, it is required to have an all-round understanding of resource countries, to conduct a rigorous feasibility study combining different disciplines, geological and non-geological work. In addition to the rigorous appraisal of petroleum resource potential, earnest appraisal of petroleum business risk, socio-economic risk, political risk and competitive risk need to be taken into account. On the basis of risk identification and classification, a whole process of risk management and control as well as global petroleum exploration and development risk evaluation and project optimization is established. It is put forward that appraisal has risk of its own, and it is necessary to overcome the effect of seven subjective factors including seduction, overconfidence, and overly conservation, etc. Through thorough analysis of investment environment appraisal indexes, the concept and method of comprehensive investment appraisal based on considering all risk factors are proposed, which can not only help master the opportunity of risk investment, but can also aid obtaining commercial discovery and economic results

Geological risk assessment of the oversea hydrocarbon exploration project plays a significant role in investment and decision-making of oversea exploration projects. In order to indicate differences of geological conditions and risk from different projects as objectively as possible, with respect to features of oversea hydrocarbon exploration projects, this paper discusses principles of geological risk assessment on oversea hydrocarbon exploration projects and puts forward a new quantitative risk assessment method combining geological characteristics with degree of prospecting. Furthermore, the parameters system and the assignment standards system for geological risk assessment are established in this paper. It provides a new and applicable method for management and decision-making of oversea hydrocarbon exploration projects

The Arctic Regions have large area, harsh natural climatic conditions, complicated geological and tectonic evolution conditions and low-level gross exploration. The assessment made by the United States Geological Survey (USGS) shows that the Arctic Regions have abundant oil and gas resources. Vendian Baikalian, Late Devonian Ellesmerian, and Middle Cretaceous Brookian orogeneses are the three major tectonic events in the Paleozoic stratigraphy and deformation history of the Eastern Arctic Region. In general, the period from Triassic to Jurassic in Branchian Sea and most areas of Northern Siberia is characterized by tectonic subsidence, during the period major hydrocarbon sources rocks and reservoirs deposited in the Arctic Regions. Intercontinental deformation of Paleogene-Neogene is related to the Pacific plate subduction, the Indian plate collides with the Eurasian plate, and the North Atlantic rifting plays an important role in the trap formation of the Arctic Regions. Northern waters of the Siberian Basin are essentially forward areas, the Pokur group between the Upper Aptian Stage and the Cenomanian State of Cretaceous has the greatest potential, many huge anticlinal gas reservoir have not been drilled, and at the same time there is great potential in discovering large-scale lithologic oil and gas reservoirs. Middle and Lower Jurassic large gas fields are one of the important potential exploration targets. Due to the harsh natural conditions, the exploration potential of the eastern Branchian Sea mainly concentrates in the Jurassic inversion anticlines which have not been drilled and partly explored, so it is almost improbable to find gas pools and condensate pools with huge reserves, simple structure, and of commercial exploitation value. Many reservoirs and hydrocarbon source rocks developed in the East Greenland Rift Basin, and there are huge potential to find fault block traps. The Arctic Regions are peaceful politically, which provides opportunities for oil and gas exploitation in the region. However, the oil price volatility, the geological uncertainty and ecological vulnerability are great challenges to the Arctic oil and gas development.