Superimposed basins with different petroleum resource and accumulation features in different basins widely distribute in China and have obvious and various textures. These basins were formed by composed basins resulted from the superimposed sediments of separated basin in different stage. Those basins belong to one of the reformed basins and have the particular structures and petroleum accumulation conditions. On the basis of the evolution and reformation of the basins and taking the geological characteristics and their superimposed relation of overlying basins and underlying basins as a whole in time and space, the superimposed basins can be divided into four types of transforming superimposed basin, reformed superimposed basin, different superimposed basin and poly-superimposed basin. The petroleum formation condition, accumulation feature and distribution rule of different superimposed basin were discussed. The favorable source rock can be developed and kept in the underlying basin of the superimposed basins, which has significant influence on the whole petroleum occurrence condition, accumulation feature and resource scale of the basin.

The acidity of crude oil is expressed by its total acid number (TAN),which is the number of KOH determined by non-aqueous titration needed to neutralize the acidity in one gram of oil. According to the distribution of TAN of oil in the world, crude oils can be classified into four types including conventional oil, low-acidity oil, high-acidity oil and extremely high-acidity oil. Oil with more than 1 mg/g of TAN is defined as high-acidity oil. On the basis of the origins of oil accumulations, the high-acidity oil can be divided into three types of primary-type, secondary biodegradation-type and mixed-type oils. The TAN of crude oil at any given biodegradation ranking tends to increase in the order of marine oils less than lacustrine oils. In the world, most of high-acidity oils were caused by biodegradation and accumulated mainly in stratigraphic traps of foreland basins, and secondly distributed in anticline, fault-block and stratigraphic traps of rift basins, passive continental marginal basins and cratonic basins.

The stratigraphic-lithological hydrocarbon accumulation zone is inferred to a group of plays formed by changes of lithofacies, lithology and strata. It controls the formation and distribution of stratigraphic-lithological reservoirs with the same geological backgrounds and genesis. The stratigraphic-lithological hydrocarbon reservoir is the main exploration object in the hydrocarbon accumulation zone. The clear target beds and excellent description methods are necessary. The stratigraphic-lithological hydrocarbon accumulation zone was divided into lithological change zone and stratigraphic change zone according to the main controlling factors and then divided into front facies zone, fan near shore, river channel, overlap zone and unconformity zone according to the deposit facies type and stratigraphic contact relation. The formation conditions and characteristics of the different zones were analyzed.

Taking Jiyang Depression as an example, the implication of petroleum exploration resource replacement strategy (PERRS) and the relationship between PERRS and petroleum exploration strategy were discussed. The researching contents and methods for PERRS were put forward. It is necessary to study the contents of three aspects including 12 items while drawing up PERRS. The three aspects contain the evaluation of present exploration situation, analysis of exploration capability and forecast of exploration development tendency. The evaluation of present exploration situation is the premise for studying and drawing up PERRS and contains four evaluation items of exploration degree, exploration potential, exploration level and qulity of exploration targets. The analysis of exploration capability is the guarantee of drawing up and carrying out PERRS and includes the analyses of geological rule, exploration course, suitability of exploration theory and technology, effectiveness of management style and quality of exploration operation. The exploration development regularity is the important reference to draw up PERRS and determines the future scale, rhythm and efficiency of exploration. The major areas of reserves increment, influencing factors for exploration development, and forecast of reserves increment tendency should be taken into account. The above three aspects including 12 items make up the basic researching system of PERRS.

The subsidence history in Junggar Basin was analyzed and modeled with EBM basin modeling system and 2D seismic traverse. The relationship between subsidence rate and tectonic evolution was discussed. The results show that there were some succession and some variety from the early Jurassic epoch to the middle Jurassic epoch. The succession displayed that the subsidence rate was lower in the north than in the south from the early Jurassic epoch to the middle Jurassic epoch in Junggar Basin.The variety displayed that only one subsidence center was developed in the southern margin of Junggar Basin in the early Jurassic epoch. Three subsidence centers were developed in the southern, northeastern and western margins of Junggar Basin respectively in the middle Jurassic epoch. The characteristic of subsidence has a close relationship with tectonic evolution. The stress state was changed from relax stress to extrusion stress from the early Jurassic epoch to the middle Jurassic epoch.

The fluid pressure is obviously lower than the static pressure in gas reservoir of the Upper Paleozoic in Ordos Basin. The fluid pressure gradient of the reservoir is high in the east part and low in the west part. Its change is accordant with the current structural gradient. It is suggested that the low pressure gradient of gas reservoir in the Upper Paleozoic was resulted from the increase in depth of the later sedimentation and the decrease of temperature during erosion. The fluid pressure gradient of Sulig Gas Field was 1.22 MPa per a hundred meters of formation, when the temperature of reservoir formation was 150℃. The pressure gradient decreased about 14.9 percent with temperature decreasing during erosion. The pressure gradient was about 1.06 MPa per a hundred meters of formation at the end of the Cretaceous and decreased about 21.4 percent with the depth increasing in the Cenozoic. Thus, the representative low-pressure gas reservoir could be formed in Sulig Gas Field.

The Ordovician weathering crust of the central gas-field in Ordos Basin could capture the Upper Paleozoic coal-typed gas and the Lower Paleozoic oil-typed gas and was proved as a source-mixed gas reservoir. The volume content and stable carbon isotopic compositions of methane and ethane have the quantitative relationship with the maturities of their source rocks. By using these relationships, a model for calculating the ratio of source-mixed gas was established. According to the model, the percentages of the Upper Paleozoic coal-typed gas and the Lower Paleozoic oil-typed gas are in the range of 22% to 84% and 16% to 78%, respectively. The large ranges of ratio between the two kinds of gases suggest that the gigantic weathering crust reservoir was made up of several isolated small gas pools. It is also shown that the main way for coal-typed gas entering the crust reservoir was eroded channel.

The fault systems and the fault evolutions were analyzed in the Dongpu Sag. The transfer ways of displacement and their corresponding transfer structures among faults within each fault system and among the fault systems were discussed. Four kinds of transfer ways of displacements were determined, including transformation, relaying, growth and decline, and simple decline. The way of transformation resulted in the transfer faults and wedge-shaped fault steps. The way of relaying resulted in the strike slopes and horsts. The way of growth and decline resulted in the central oblique anticlines. The way of simple decline formed decline slopes and fault noses. The transfer structures formed in different time were connected to form transfer structure belts and made the sag in segmentation. The superposition, reconstruction and migration of the transfer structures were closely related to sedimentation and favorable to generation of subtle reservoirs.

The analysis on soluble organic matters from Jurassic coal and its macerals in Tarim Basin showed that there were some biomarker evidences for biodegradation of Jurassic coal, such as n-alkanes, isoprenoids, terpanes and steranes. The mass chromatogram for n-alkanes was characterized by a bimodal distribution in relative proportions of mid-chain and long-chain n-alkanes and ratio of ∑ n-C _21- to ∑ n-C ₂₂₊ above 1.0. In the GC-MS traces of the saturated hydrocarbons, some chemical compounds were identified, such as tricyclic diterpenoids (C ₁₉-C ₂₉) at low intensities, tetracycloclicterpane and C ₃₂—C ₃₄-benzohopane. For the low mature coal samples, the ββ-to-(ββ+αα) ratio was 0.59 and almost reached the equilibrium value. The comprehensive analysis of above features showed that there was a strong biodegradation of saturated hydrocarbon fractions in Jurassic coal rock in Manjiaer Depression of Tarim Basin. In the micro-process of coal rock, the rough biodegradation sequence is inertinite first and vitrinite is followed. The n-alkane on exinite is hard to be biodegraded.

A dynamic equilibrium kinetic model for describing geological evolution history of coalbed methane (CBM) was built,and the relative simulator was programmed in order to study generation,migration,accumulation and emission histories of CBM in Sunan syncline area.The tectonic,burial and thermal history of this area were analyzed.The simulation of CBM evolution history indicated that CBM evolution history in Sunan syncline area could be classified into four stages.In the first and the second stages,CBM was concentrated in low level. In the third stage,gas generation and emission were developed vigorously,and in the forth stage, diffusion emission was the main process.The transverse content of coalbed methane is high in the axis of the syncline and low in the edge at present.

Three-dimension (3D) models were created by integration of geological data,well logs and seismic data for a better heterogeneity characterization.Well logs, cross-well seismic data and 3D seismic data in Ken 71 area of Shengli Oilfield were incorporated into a 3D model with sequential Gaussian-Bayesian simulation.The model generated with this technique has several advantages of higher vertical resolution compared with the 3D inverted acoustic impedance (AI),consistency of lateral variation as 3D inverted AI and more reliability due to integration cross-well seismic data.It is observed that the precision of the model depends on the 3D inversion.

On the basis of core observation and logging data, the sedimentary facies and their characteristics of stream channel reservoir in the second member of Shahejie Formation in Xianhe Oilfield of Dongying Depression were studied. The trend surface analysis and shale color district figure combining with sedimentary palaeogeographic pattern and inherit of provenance direction were applied to analyze provenance direction. The analysis result showed that the provenance from first to fourth group in the second member of Shahejie Formation in the third area of Wangjiagang Oilfield was mainly derived from the south part of the study area. The drilling ratio analysis method and the average thickness curves of sand body can illustrate the features of reservoir. The suitable drilling profile was applied to stochastically modeling of reservoir, and the artificial neural network method was used to predict reservoir thickness and porosity from the first to fourth group in the second member of Shahejie Formation. The result is in good agreement with those known well data. The seismic coherence cube technology was used to remove noise and interpret seismic data for finding out types, features and geologic attributes of correlation abnormal volume, researching on the time-space appearances and distribution of every sand layer and predicting the typical single sand-body. The results provided evidence for petroleum exploration and development.

The waveform inversion method for computing shear wave anisotropy of formation in the cross-dipole acoustic-array logging was introduced. This method is based on the very fast simulated reannealing (VFSR) to evaluate shear wave anisotropy. The global optimization search speed of this method is faster than that of other reannealing algorithms. The data from several wells were intensively processed using the software made upon the VFSR. The results indicate that this algorithm can meet the need of computing accuracy and computing speed in the waveform inversion. This method can be used in practical data processing of cross-dipole acoustic-array logging.

The large scale gas reservoirs have been found in deep volcanic formation in the north of Songliao Basin of China. The volcanic gas reservoirs are characterized by various type rock, complex lithologies, sharp lateral variations of lithologies and lithofacies, development of microcrack, poor physical property, serious anisotropy and difficulty of development. The lithology, lithofacies, development degree of fracture, types of storage space, configuration of pore and fracture, and validities of matrix and fracture in deep volcanic formation were evaluated with multidisciplinary methods. The development mode, layer series of development, rational spacing between wells, deploy of well pattern, velocity of gas production, years of stable production and recovery factor were discussed and optimized on the basis of geological study. The reasonable development scheme for volcanic gas reservoir was compiled. The various technologies, including overall planning, implementation in turn, pilot test of infilling well pattern, following-up investigation, and regulation on time, were used in the development of volcanic gas reservoirs. The good results have been achieved.

A model holder for high-temperature and high-pressure resistance was designed and taken as a connection between outer pipelines and model. On the basis of the common microcosmic experiment system, a microcosmic experiment system for high-temperature and high-pressure resistance was developed and used to observe the dynamic behavior of bubble point, oil-gas distribution and oil-gas flow performance, and effect of free gas on oil and water flow during pressure declines. The oil-gas flow law during water flooding and crude oil containing gas at different pressure were analyzed. A macroscopic experiment system of high-temperature and high-pressure resistance was developed to analyze oil and gas productivity. The development effectiveness of water-flooding under different pressure was researched. The results showed that there were less gas points, and the gas point bulk was small, while reservoir pressure declined to about point pressure. Free gas is helpful to oil and water flow. Swept area of water-flooding was wider. If water injection is running before reservoir pressure declines to point pressure and reservoir pressure is keeping more than 87% of point pressure, the oilfield development will need less injection of water and get low total water cut and more recovery. The effectiveness of the research results have been proved in practice.

According to the geologic characteristics and waterflood development performance of the exploited Fuyang Formation in the periphery of Daqing Oilfield, the effective driving energy system in low-permeability formation, the fluid flow properties of fracture-matrix system, displacement characteristics of waterflood development of fracture formation, and oil production mechanism of imbibitions process were investigated. The starting pressure gradient was achieved using field data. The effective drive model for oil displacement was developed. The line water injection and well pattern infilling technologies for improving the exploitation effectiveness in the periphery of Daqing oil field were discussed.

The flow behavior of viscoelastic and power-law oil-displacement agent in individual pore throat model and 2D stochastic channel bundle model was studied using numerical method.The individual pore throat of reservoir was modeled as a constricted channel and expanded one,which makes up the unit of the 2D stochastic channel bundle as porous media model.The channel bundles whose size conforms to same or different probability distribution were used to model homogeneous and heterogeneous porous media.On the basis of the flow in pore throat model,the relative expressions between pressure drop and flow rate of viscoelastic fluid and power-law fluid in 2D stochastic channel bundle were presented.The percolation models of the two kinds of fluid were developed on the basis of Darcy equation.Equivalent permeability was put forward to measure the seepage ability of non-Newtonian oil-displacement agent.The results show that for the viscoelastic oil-displacement agent,the seepage ability decreases with the increase of viscoelasticity,diurnal injection,and heterogeneity and mean pore size of porous media.For the power-law fluid,percolation is the function of power-law exponent and pore structure regardless of diurnal injection.The seepage ability increases with the decrease of power-law exponent,mean pore size and heterogeneity.

There are many types of crude oil in Ordovician fracture-cave reservoirs of Tahe Oilfield,including condensate oil,volatile oil,normal oil and heavy black oil distributed in different regions.On the basis of geological control factors,the difference of fluid property was analyzed.The fracture-cave reservoirs have the heterogeneity and multi-period oil sources.The heterogeneity of hydrocarbon fluid property is related to the destructive reformation in the forming process of reservoirs.According to the geological response characteristics of hydrocarbon fluid distribution,the Ordovician reservoirs in Tahe Oilfield can be divided into six flow units,in consideration of the same flow unit,similar fluid characteristic,similar well performance,similar physical property of reservoir and similar natural energy.Some stimulation measures and suggestions for different flow units are presented,in order to reasonably and scientifically develop this type of oilfield.

On the view of different construction interface and different type of remaining oil distribution in thick formations of extra-high water cut period in Lamadian Oilfield,three kinds of fine inner potential excavation technology for thick oil formation were presented.The first one is the fine division water injection and plugging in a long rubber packer with a seal length of 1~3 meters.This packer can be used to jam the thin barrier and neighbour borehole.The thickness of construction interface jammed by this packer is 0.2 meter.The second one is the inner hydraulic slotting perforation technology.This technology is characterized by high accuracy for positional control and no quaking for slotting.The operation of this technology has no damage to the thin interbed and cement sheath.The barrier thickness is minimized to 0.2 meter.The third one is the inner positional balance fracturing technology.Six kinds of string can be used to protect the construction interface.The construction interface of 0.4 meter in thickness was tested.The three kinds of fine potential excavation technology were all used in large scale and became the new mode for inner potential excavation of the thick formation in the extra-high water cut period.

A percolation network model for expressing pore structure and fluid characteristics of reservoir was developed.The effects of size and shape of pores,connectivity and the amount of micropores in reservoirs on the relative curve of the resistivity index I with the water saturation S _w were simulated by numerical modeling.The effects of formation water salinity on the rock resistivity were discussed.The relative magnitude of the different influencing factor was analyzed.The quantitative simulation of the different factors affecting the I— S _w curve shows that the connectivity of the void space and the amount of micropores have the greater effect on the I— S _w curve than other factors.The salinity of formation water has a great effect on the absolute resistivity value.The non-archie phenomenon is prevalent and remarkable in reservoir rocks with low permeability.

Aiming at the complexity and multiple flow forms at the bottom of flow field in horizontal well,the basic flow forms of fluid field near and far horizontal wells in low-permeability reservoir were analyzed.The calculating formulas for producing capacity of horizontal well in low-permeability reservoir with deformation medium and start-up pressure gradient were developed.The productivity characteristics of horizontal well and various flow features in different horizontal section of well were discussed by analyzing and calculating examples.The results showed that the productivity of horizontal well in low-permeability reservoir decreased with the increment of start-up pressure gradient and deformation coefficient of medium.As the horizontal section of well got longer,the fluid far away from horizontal well changed from the radial flow to the planar flow.The main pattern of fluid near horizontal well was radial flow.

The Archie formulae for some ideal rock models were derived according to the Ohm Law using the Calculus technique.The affecting factors on the cementing exponent and the saturation exponent were numerically analyzed.It is proved that the saturation exponent kept relatively constant in oil-wet reservoirs while it changes a lot with water saturation in water-wet reservoirs.The relationship between the saturation exponent in water-wet reservoir and saturation exponent in oil-wet reservoir was derived.It can be concluded that watered-out extent will affect the Archie formulae dramatically. It should be given great attention in the well logs analysis of waterflooded zones.

The exploration and development of abroad deepwater oilfields were introduced.The most appropriate development mode applicable to deepwater oilfield of the South China Sea was investigated by comparing the current typical engineering modes for deepwater oilfield development in the world according to the actual environmental conditions of the South China Sea, as well as the current and near future technical capability and equipment state of the China National Offshore Oil Corporation.The structures of typical deepwater platforms were analyzed.The selection scheme of deepwater platforms in the South China Sea was suggested.The key technologies for development of deepwater platform in the South China Sea were discussed.

The technology of top screen pipe cementing of casing and liner in the horizontal well and sidetracking horizontal well was presented.This technology is different from the general method without cementing at the top of screen pipe in casing and liner.It can isolate the liner from the external casing and formation,and provide the possibility of perforating oil layer in the transition segment.Two sets of crafts in casing were made.One is the combination of the screen pipe,external casing packer,drillable plug,stage cementing collar for horizontal well,and the other is the combination of the external casing packer,drillable plug,stage cementing collar,drilling liner hanger for sidetracking horizontal well.The successive field test of twenty wells has been achieved.

Aiming at the problem of equivocal correction coefficient formulas of casing strength quoted in the American Petroleum Institute(API),the regularities and distribution of parameters for casing properties of API were discussed.The regularities of casing strength distribution were obtained by means of Latin Hypercube stochastic simulation method based on Monte-Carlo method.The influences of the randomness of geometric dimensions and mechanical properties of casing on the randomness of casing strength were achieved.The reliability model of casing strength was established by the use of reliability theory.The casing strength values under different reliability and the reliability of casing strength value in API formula were calculated.The research results indicate that the greater the random of casing properties is,the lower the reliability of casing strength value in API formula will be.The correction coefficient of elastic collapse strength of casing in the API formula is reasonable in terms of reliability.However,the API internal yield pressure formula of casing appled the correction coefficient is much safer.

The concept of big system was applied to the synthetic diagnosis of the electric submersible pump(ESP) unit.The ESP unit was divided into three sub-systems.The diagnosis models of the three sub-systems were synthesized.The synthetic diagnosis method for the ESP unit was proposed.On the basis of the concept and theory of system engineering,the working condition,the characteristics and technology parameters of the underground units such as ESP and motor,as well as the stratum data,production data,liquid data of oil wells were analyzed.By using the recording charts and hydraulic experiment data,a synthetic diagnosis model for ESP unit was built.The correlative parameters of the ESP and motor working underground were computed and compared with the special parameters.Using contrast and test method and recording charts for synthetic diagnosis of ESP unit,and technology for data collection and remote transmission of downhole well,The synthetic diagnosis for ESP unit was realized.

The leakage of pipelines may result in the economic loss and serious environmental pollution.On the basis of the negative pressure mean wave velocity method,a new iterative algorithm for leakage orientation of oil pipelines was proposed by analyzing the transmitting characteristics of pressure wave and the defect of traditional formula for leakage orientation of pipelines.The proposed new algorithm is helpful to improve the orientation precision.The wavelet transformation was used to cancel the noises in the negative pressure signals and capture the strange point.The fairly precise time difference was obtained.The simulation results showed that the orientation precision of the proposed algorithm was better than the traditional method.

The governing equations of the power-law fluid flow in annulus with the inner cylinder executing a planetary motion under the moving bipolar coordinate system were established.The governing equations were numerically solved by the finite difference method,and the distribution of the stream-function of the flow was obtained.The results show that the secondary flow appears in the flow of the power-law fluid in annulus with the inner cylinder executing a planetary motion.The distribution of the secondary flow is related with the direction and magnitude of the revolution velocity and the rotation velocity of the inner cylinder and the eccentric distance of annulus.

There are some lacks in the former models for calculating fracture initiation pressure and fracture starting point in deviated wellbore with perforations.On the basis of the stress field in the intersection between drilling hole and perforations,the calculating models for transverse stress,fracture initiation pressure and fracture starting point at the intersection of two perforated holes existing Micro-Annulus plane were analyzed.In order to estimate the turning degree of fractures,the models for calculating angle between fracture initiation plane and the perfect hydraulic fracture plane are presented.A calculation example is given.

The compound plugging material is broadly distributed in the leakage formation after compound plugging agent is injected into the leakage formation.The proportion of various plugging material in some area is balanceable relatively.So,there is a balance area.The concept of balance area is useful for lost circulation control.A novel lost circulation simulator for simulating leakage formation and lost circulation control procedure perfectly was developed.The distribution and occlusion status of plugging material and the position of balance area were experimented on core in laboratory and could be observed from the experimented core cutting.The lost circulation control formula can be modulated till the experiment successes.The experimental result showed that the balance area would move towards the entry side of core,if the effect of lost circulation control was good.Otherwise,it will move towards the outlet of core,even no balance area appeared in the core.The experiment of new lost circulation simulator has a good repeatability.The formula acquired by experiment was applied directly to the lost circulation control in field.The result showed that this technology has been successfully applied in the procedure for lost circulation prevention and control.

The optimization history of gas allocation in gas-lift block was decribed.The characteristics of all kinds of gas-lift performance curves were analyzed.The optimum model of gas allocation for development of oilfield was given.A new method named as sequential unconstrained minimization technique combined by the interior-point method and exterior-point method to solve the non-linear optimum mathematic model of gas allocation was proposed.Newton-Raphson method was adopted to solve the nonlinear equations,and the maximum gas allocation method for predicting the initial gas injection rates was modified.Taking Zhongyuan Oilfield forth block as an example,four gas allocation schemes were obtained on the basis of the gas-lift performance curves.The new method was used to calculate the gas allocation of the four schemes.An optimum scheme was presented.

A comprehensive study on dolomite reservoir in Tarim Basin showed that the dolomite reservoir in the Lower Paleozoic of Tarim Basin was resulted from the combination of multiphase and multi-type geological processes. The main elements to form dolomite reservoir include the favorable sedimentary facies, multiphase dolomitization, various corrosion, fracturing and associate cracks. The corrosions contain the deep-buried dolomite dissolution, corrosion of multi-supplying organic acid in hydrocarbons, magmatic hydrothermal corrosion, the corrosion of acid fluid generated by thermochemical sulfate reduction, squential-interface corrosion and unconformity karstification. The comprehensive evaluation of dolomite reservoir and the systematic analysis of reservoir-forming conditions showed that the Cambrian-Lower Ordovician dolomite reservoirs in Tarim Basin were wide-ranging and also had the preferable reservoir-forming conditions. The key factors for hydrocarbon accumulation are mainly the efficient cap-rock and the steady tectonic settings. Three new domains of exploration, including dolomite buried-hill-type reservoirs in the regions of Yingmaili-Yakela, Tazhong and Mazhatage, the dolomite inside-type reservoirs in the Akekule and Tazhong regions, and the reservoirs under the middle Cambrian halo-anhydrites in Tazhong and Bachu regions, were illustrated.

Puguang Gas Field as the largest gas field of Sichuan Basin is also the biggest marine carbonate formational gas reservoir. In addition, Puguang Gas Field has highlights in several aspects such as the deepest burial condition, the highest reserves abundance, excellent reservoir quality, the thickest reservoir bed, the highest quantity of H ₂S and the biggest dry coefficient of natural gas. Puguang Gas Field has the special condition of reservoir-forming, which is in virtue of some factors, including the repeated infusion of the multiple hydrocarbon and high quality of hydrocarbon, the dynamic matches of channel system and the processes of generation and expulsion of hydrocarbon, the development of reservoir bed at the edge of evaporated plateau and the high-energy oolite facies, the highly formation of the secondary porosity due to the late dolomization and intense acid corrosion, the paleo-tectonic bulges and long-term received hydrocarbon, the occurrence of thermochemical sulfate reduction and the highly development of secondary porosity in reservoir bed, the optimism of the performance of reservoir bed, as well as the effectiveness barrier of thick gypsum rock in Jialingjiang and Leikoupo formations overlying Feixianguan Formation.

The deepwater area with over 300 meters in water depth in the northern continental margin of South China Sea experienced pre-rift phase, rift phase,post-rift phase and Neotectonic phase. In this area, a bump-sag pattern was formed. The Paleogene system with 3~6 kilometers in thickness was deposited in the sags during the rift phase. The thickness of Lower-Middle Miocene deposited during post-rift phase was less than 2000 meters. The late Miocene-Quaternary system with a tremendous thickness was formed and also reformed in east part during Neotectonic phase. The potential hydrocarbon sags in deepwater area are the faulted depressions formed in the rift phase. The proven source rocks are the early Oligocene mid-deep lacustrine mudstone, transitional mudstone,marine mudstone and coal system. The probable source rock is the Eocene mid-deep lacustrine mudstone, and the possible one is the upper Oligocene and Miocene marine mudstone. There are at least three reservoir cases in deepwater, including Oligocene transitional sandstones, Neogene-Quaternary marine deepwater sandstone and reef, and Eocene terrestrial sandstone. The seal rocks are developed widely, and the Neocene marine mudstone is the regional seal. There are a lot of traps with the main styles of draping anticline, fault trap and deepwater fan. The oil-gas migration style varies with time and space and is controlled by the Neotectonic fault activities. The parallel migration dominates in the deepwater of Qiongdongnan Basin and in the early phase of Baiyun Depression, and the vertical migration dominates in the late phase of Baiyun Depression. The deepwater play and traps contain bulge, secondary bulge in sag, fault zone and deepwater fan. Exploration activity should first aim at the structural traps in the sag and in the forward direction of structure around the sag and then gradually develop toward the non-structural trap.

Fault is a chief factor for affecting oilgas reservoir formation. The lithologic bodies such as alluvial fan, fan-delta, reef and bio-bank are the main oil-gas reservoir bodies. When the fault is connected with the lithologic body, the fault-lithologic body oil-gas reservoir will be generated. The study on Junggar Basin showed that the fault and lithologic body became the trap elements and resulted in the dominant type of oil-gas pools in Junggar Basin. The fault activities controlled the basic features of pool formation in the basin. The fault combination style moderately influenced the migration, accumulation, distribution and abundance of oil and gas. The faulting phases strongly influenced the oil-gas migration and accumulation period and the style of pool formation. The Chepaizi-Mosuowan paleo-uplift in the interior of the basin provided the elementary environment for the development of the stratigraphic traps and the fault-lithologic traps to a large extent. The two flank slopes of the paleo-uplift are the favorable area for generating the lithologic and stratigraphic oil reservoirs. The southeast flank slope is the best area.

The opposite opinions about the problem that coal-bed gas was derived from coal and its measure strata are presented. The carbon isotope composition of coal-bed gas（CH ₄ and CO ₂), the isotope compositions and products obtained from the thermal simulation experiment of coal and its measure strata as well as the abnormal high-mercury contents in the coal-bed gas were observed. The geotectonic environment of coal-bed gas reservoir formation and the gas eruption in the coal mine and forest fire were analyzed. The abnormity of satellite thermal ultra-red was found before gas eruption and forest fire. According to the practice and experiences of coal-bed gas exploration in the United States, the coal-bed gas might be derived from the deep crust or upper mantle, the form of the methane is depended on gas divorced from upper mantle and the Fischer-Tropsch synthetic, rather than coal and coal measures strata. On the basis of the above origins, a new plan for preventing coal-bed methane explosion may be discovered. The exploration targets of coal-bed gas will be reconsidered.

There are various and abundant lithologic-stratigraphic hydrocarbon reservoirs in Dagang prospecting area of Qikou Sag in Huanghua Depression of Bohai Bay Basin. The primary reservoirs in reserves are the updip pinch out reservoir and structural-lithologic composite reservoir. Those non-structural traps rely on matching between palaeostructure background and sedimentary system. According to palaeostructure cosmetics of Qikou Sag in Dagang prospecting area and distribution characteristics of sedimentary system, there are five important domains for petroleum exploration, including ① enclosed slope of palaeohigh, pitching end, and reversal clastic source area of slope break; ② frequent facies change area; ③ break in gentle slope of palaeohigh; ④ semi-close lacustrine bay area; ⑤ break in abrupt slope and low-lying offloading areas in depression. According to the exploration principle of "macroscopic lithologic-stratigraphic hydrocarbon reservoirs", a special exploration strategy was adopted in Dagang Oilfield. The sedimentary system superposition research method was combined with palaeostructure background. The structural zone was emphasized as the lithologic change zone, and the exploration of lithologic-stratigraphic hydrocarbon reservoirs was combined with subtle techniques and procedures. Comparing with the structural reservoir, the lithologic-stratigraphic reservoirs in Dagang prospecting area have more abundant types, more wide distribution areas and more reserves, as well as all system tracts and whole pressure fields. So, these reservoirs are the most important exploration targets.

The microfossil analysis of the samples from the Middle and Upper Triassic in eastern Gansu Province was made. The extremely abundant acritarchs assemblage mainly consisting of Leiosphaeridia was discovered in Chang 7 Member of Yanchang Formation in southwestern Ordos Basin. Leiosphaeridia discovered from the Yanchang Formation might root in the lacustrine macroscopic algae, which may be the sporophyte of large-scale red algae and/or chlorophytes. Whereas the Proterozoic and Paleozoic Leiosphaeridia is commonly thought as the marine unicellular phytoplankton. The strata of high abundance acritarchs accorded with the distribution of the main source rock in Chang 7-3 and Chang 7-2 members of Yanchang Formation in eastern Gansu Province. The acritarchs is the important component of alginite and amorphous mass. The pyrolytic indexes show that hydrocarbon potential gradually boosts up with the increase of acritarchs abundance. The lacustrine acritarch is the important biologic source of high-quality source rock of the Yanchang Formation in Ordos Basin.

The giant Ordovician buried hill in Lunnan area was characterized by wholly oil-bearing and locally enriched oil. It is difficult to be explored because of the high heterogeneity of carbonate reservoirs and the complexity of fluid in the weathering crust. The key factors for hydrocarbon accumulation including source rocks, reservoirs and oil-gas migration systems were systematically researched by the new theories and methods in petroleum geology, geophysics and organic geochemistry. Furthermore, according to the tectonic evolution of the buried hill and multi-period accumulation of oil and gas, a hydrocarbon accumulation model for the giant buried hill in Lunnan area was proposed. This model has played a guiding role in finding and proving the giant oil field in the Lunnan buried hill. The proved reserve in this field is more than 600 million tons.

The drilling data, geophysical data in the north part of Baiyun Depression and ODP files were used to well-seismic analysis, strata correlation and seismic stratigraphic interpretation. The results showed that Baiyun Depression was in the continental shelf in the late Oligocene from 32.0 Ma to 23.8 Ma before present. The large-scale shallow-water continental delta sandstone and mudstone inter-bedding deposits of Zhuhai Formation were developed around Baiyun Depression, which is different from half-deep or deep water fine deposit since 23.8 Ma. At the same time, the upper surface (at 23.8Ma) and lower surface (at 32.0Ma) of Zhuhai Formation are two large unconformities created by two times of large-scale structural movement in the South China Sea and the transferring interfaces of sedimentary-tectonic-climate conditions. During deposition period of Zhuhai Formation, the continental-shelf slope break migrated from north to south till to the southern uplift belt in the Pearl River Mouth Basin, and the large progradational delta depositional systems was clesely correlative with the extensive regression of relative sea level changes in the late Oligocene. Zhuhai Formation in Baiyun Depression has good shallow marine delta reservoir-seal combination conditions, which is significant for petroleum exploration in deepwater area of Baiyun Depression.