The Carboniferous period was the transitional period in which the Junggar and the Tulupan-Hami micro-continental blocks separated from each other, converged together and ran into a stage of an interior cratonic basin. It underwent two cycles from extension to convergence during the Early and the Late Carboniferous periods, respectively. The Early Carboniferous was characterized chiefly by marine deposition, while the Late Carboniferous developed the marine-terrestrial transitional facies and volcanic rocks. The volcanic rocks of Batamayineishan Formation of the Upper Carboniferous (C₂b) were dominantly of center-eruptive and fracture-eruptive origins, medium-to-basic and medium-to-acid rocks, and volcanic rocks consisted of such reservoirs as the weathering crust and the interior interval owing to the long-periods of weathering and leaching, the dissolution of organic acid or deep thermal fluids. The reservoir thickness and scale of the weathering crust were largely influenced by the hiatus, lithology, litho-facies and faults. The reservoir space was composed mainly of secondary pores and fractures. The effective reservoir intervals occurred within 350m downward from the unconformity at top Carboniferous, while the local positive relief was more favorable. On the other hand, the volcanic interior reservoir intervals were chiefly controlled by the volcanic edifices, litho-facies and the short-period of hiatus, while the explosive and the overflowing facies were more prone to be reservoirs. The reservoir of the Lower Carboniferous was mainly of the sandy-conglomerates. Based upon the reservoir features, there were four kinds of hydrocarbon plays in the Carboniferous including the weathering crust of the Upper Carboniferous volcanic rocks, the interior interval of the Upper Carboniferous volcanic rocks, the sandy-conglomerates of the Upper Carboniferous, and the sandy-conglomerates of the Lower Carboniferous. The first one is the established play, while the other three types are the conceptual plays. The Carboniferous of Junggar Basin has the properties of large thickness of hydrocarbon source rocks, much-developed volcanic reservoirs and favorable conditions for oil and gas pool-formation and thus has a promising and large exploration potential.

The area percentage of lake and ocean basins is from 71% to 83% of the earth in the geological history, but the total area of oil and gas fields is little. Some basin has petroleum, and some has no petroleum. Some basin is rich in petroleum, and some basin is poor. The amount of organism in the sedimentary rock determined the quantity of oil and gas. Nourishment was the key factor for organism growth and river was the main source of nourishment in the basin after Carboniferous. There were many rivers around the lakes in the Mesozoic and Cenozoic periods in China. The nourishment was abundant in those basins. The growth and preservation of the organism were controlled by the rates of deposit and subside of basins. The source rock was rich in the basin deposited with low rate, and the source rock was poor in the basin deposited with high rate. The marine sediments distributed in the southeastern coast of China. The correlation between marine source rock and river in the Cenozoic was obvious. The middle-big gas fields located in the front of river (delta). It is the best way for “determining source” to search the river and the corresponding delta of marine. The most oil-bearing basins were correlative with the lake-delta-river system or the ocean-delta-river system in the Upper Paleozoic. The most oil-bearing basins were also correlative with the lake-delta-river system or the gulf-delta-river system in the Cenozoic of the world.

The Carboniferous reservoir has become the main gas producing formation in Sichuan Basin through more than 30 years of exploration and development. Recently, the new round study on stratigraphy, sedimentary facies, reservoir, source rock, structure, accumulation and trap in the eastern Sichuan Basin indicated that there are two kinds of exploration targets. One is lithologic trap, which is under the control of grain-clastic bank and heterogeneous burial dolomization in inner Carboniferous, and it shows the characteristics of heterogeneous reservoir. The other is large stratigraphic trap, which can be formed in Carboniferous wedge out area. So the Carboniferous reservoir in the Sichuan Basin has the formation condition of lithologic and stratigraphic gas pools,and 4 favorable regions and 12 prospective targets have been found, which reveals the great exploration potential.

Most source rocks of the large marine oil-gas fields in domestic and overseas are graptolite shale, oil shale and marl with great amounts of clay mineral, which formed in the deepwater slope environment transferred from tableland to trough.But the carbonate rock is formed in the shallow water environment under good exchanging condition with atmosphere, which causes the low abundance of organic matter and poor-type kerogen. Hydrocarbon-expulsion efficiency of carbonate rock is lower than that of shale, and the TOC content in carbonate rock can not be reduced when the maturity increases. So, carbonate rock can not become the effective hydrocarbon source rock. The carbonate rock-argillaceous rock, limestone-siliceous shale and sea-bottom clastic rock developed from east to west in Pingliang Formation of the western Ordos Basin,which shows the lithological sequence of marine sediment resulted from increasing water depth. The graptolite shale and marl with high-abundance hydrocarbon are formed in the palaeogeographic environment of deepwater slope.

Through analyzing the main types, micro-fluorescence and thermodynamic characteristics of fluid inclusions in the Neogene reservoir of Huatugou Oilfield,the process of fluid filling into reservoirs could be divided into two stages including low-temperature and low-salinity fluid, high-temperature and high-salinity fluid. The study on the burial history and thermal history showed that hydrocarbon filling in the first stage was mainly a trace amount of immature hydrocarbon and happened at the middle Pliocene Epoch. The hydrocarbon filling in the second stage was a large scale filling of oil and gas and happened in the late Pliocene Epoch. The second episodic petroleum accumulation process lasted a short time and could be a fast and efficient petroleum-charging model.

As main conduits of hydrocarbon migration as well as seals,faults play an important role in hydrocarbon accumulation,especially in heavily faulted areas. The mechanism of hydrocarbon migration in fault zones remains to be a major issue in petroleum geology. This paper deals with the origin of fault asphalt zone and its significance in hydrocarbon migration in the Dongxin oil-gas field in Bohai Bay Basin. The results show that the larger growth-fault can form bigger cavities along fault zone during periods of active faulting. The characteristics of fault cavities are dependent mainly upon stress state,lithology,the shape of fault plane and hydrocarbon injection,with areas of high fault-plane irregularity being more favorable for occurrence of fault cavities,which in turn are better conduits for hydrocarbon migration. Therefore,the position and size of fault cavities determine the different migration paths of hydrocarbons along a fault. Once hydrocarbon migrates into the cavities,light components of hydrocarbon are escaped firstly,leaving the remains of heavy residue,i,e.,asphalts.

The thermal simulation test of light hydrocarbon and the individual light hydrocarbon carbon isotope analysis method were used to investigate the generation model and carbon isotopic composition of light hydrocarbon obtained from coal. The results showed that a large amount of light hydrocarbon was generated from coal when the maturity R_o ranged from 1.1% to 1.7%, and the aromatic amount was the most while the maturity R_o was over 1.7%. The carbon isotope values of benzene and toluene in coal pyrolysed gas are comparatively greater. The δ¹³C value of benzene was from －25.2‰ to －17.6‰, and the average value was －22.2‰. The δ¹³C value of toluene varied from －25.3‰ to －17.2‰, and the average value was －22.1‰. All of these values are quite similar to the carbon isotopes of kerogens in the source rocks, which shows a good inherit effect of carbon isotopic between kerogen and aromatics. The light hydrocarbon composition characteristics of coal-derived gas and carbon isotope analysis showed that the relative content of methylcyclohexane was more than 50% in the C₇ light hydrocarbons of methylcyclohexane, dimethylcyclopentane and normal heptane in about 92% of 173 gas samples. The carbon isotope values of benzene, toluene, cyclohexane and methylcyclohexane in natural gas were greater. The δ¹³C value of benzene ranged from －24.4‰ to －16.2‰, and the average value was －20.9‰. The δ¹³C value of toluene varied from －24.1‰ to －16.9‰, and the average value was －20.4‰. The δ¹³C value of cyclohexane ranged from －25.8‰ to －16.2‰, and the average value was －21.9‰. The δ¹³C value of methylcyclohexane varied from －25.9‰ to －18.7‰, and the average value was －22.0‰. The natural gas migration direction analyzed by means of light hydrocarbon composition change showed that the hydrocarbons migrated mainly from the south to north in the forming stage of gas reservoir in Sulige Giant Gasfield.

Based on the geological features of bound water film with fixed thickness, the change law and controlling factors of fluids in reservoirs during forming period of the tight sandstone gas reservoirs were analyzed. Three geologic thresholds in the forming process of tight sandstone gas reservoir, including gas injection threshold, gas saturation threshold and gas termination threshold, were established. The corresponding concept model and calculation model were set up and used to predict the tight sandstone gas reservoirs in the Upper Palaeozoic of Ordos Basin. The results indicated that the correspondence depths of three geologic thresholds were 2350m, 2850m and 4800m respectively. The liquid distribution characteristics predicted by using above geologic model are in good agreement with those of actual reservoirs, which indicates that this model can be used to accurately predict the liquid distribution in the tight sandstone gas reservoir.

The western Tabei Uplift with the complex geological structure and a series of oil and gas layers,is a typical “composite hydrocarbon accumulation play ”. On basis of the physical properties, geochemical behavior and carbon isotope date,crude oils in this region were classified into marine oil and terrestrial oil,and the terrestrial oil includes lacustrine oil and coal measure oil.Compared to terrestrial oil, the marine oil has high-density and high-content dibenzothiophene, low-content rearranged terpane and sterane series and low-value of carbon isotope. The marine oil was mainly derived from the Middle-Upper Ordovician source rocks and distributed in the Ordovician deep karst reservoir and similar to crude oil of the western Lungu and Tahe areas. The lacustrine oil mainly distributed in the weathering crust underlying K1kp Formation, and coal measure oil was mainly located in the sandstones of N-K1bs.Fine oil-source correlation is significant for hydrocarbon accumulation,and it can provide evidence for identifying oil and gas sources, hydrocarbon charging times and migration direction. This method can also effectively identify the hydrocarbon transmission systems and provide a direct evidence for oil-gas distribution and controlling factor analysis.

The relationship between the genesis of CO₂ and dawsonite in the northeastern China was studied on the base of the research of CO₂ gas reservoirs and dawsonite in the south of Songliao Basin and Hailaer Basin,with the help of the analysis of carbon and helium isotopes of CO₂ gas reservoirs and carbon-oxygen isotopes of dawsonite in each basin respectively,and combining with the relationship between CO₂ gas reservoirs and fault,volcanic rocks.It was found that most of CO₂ in the northeastern China had a mantle-derived magmatic genesis and was homology with the CO₂ forming the dawsonite.As the trace mineral for CO₂,dawsonite can register the accumulation of CO₂ during geological history.High concentration of Na⁺，K⁺，HCO₃^-and CO₃^2-were displayed owing to the modification of CO₂ in formation water and crude oil.The geology record of mantle-derived magmatogenetic CO₂ was built according to the relationship between dawsonite and CO₂,the changing on the concentration of the ion in formation water and the abundant CO₂ dissolving in crude oil.

On the bases of strain energy, surface energy in rock and fracturing mechanics theory, the relationship between crustal stress and parameters of tectonic fracture was confirmed using the represent element volume and flat seepage model. The Coulumb-Mohr principle was applied to the examination of shear fracture, while Griffith principle was taken as the examination of tension fracture. The calculation model of the relationship between crustal stress and tectonic fracture parameter was developed and used to calculate aperture, density, porosity and permeability of fractures on the basis of paleo-fracture parameters. The calculated vector parameters such as permeability were anisotropy using this model. In combination with stress field numerical simulation, the calculation model is available to quantitave characterization of reservoir fractures and prediction of fracture parameters in the brittle-elasticity strata, such as sandstone, carbonate and igneous rocks.

The Markov chain models have played a more important role in the reservoir stochastic modeling, but the models are difficult to be integrated with the multi-scale data such as logging, core data and seismic data, which limits the application of the models. A new method and some formula were proposed for integrating the multi-scale data with the Markov chain models. The large-scale data were added into the models and taken as the conditional data, and the small-scale data were used to get exact data of well points by formula. The application of the method to simulate lithology of a section across wells in Y region of SL Basin shows that the fine lithology distribution obtained from the new method is more accurate and distinctive than that of the previous method.

One of the pathways to more efficiently and economically exploit the proved reserves is to produce oil in a dynamic real-time optimal state under the existing production conditions, which is one of the cores for the intelligent oilfield. The reservoir is recognized as a complex dynamic system, and the optimal object is to maximize the net present value of production in the reservoir optimization. By solving the mathematical model for describing the reservoir production status to determine the real-time control settings, the optimal production schedule can be obtained. Because dynamic production optimization of reservoir is a large-scale complicated optimization problem, an efficient gradient-based algorithm is used to treat the problem. The control gradients are obtained by the maximum principle firstly, and then the line searching method can determine the optimal control settings of each control step. The analysis on the application of above theory in oil reservoir shows that the optimal production scheme is coincident with the actual demand of oilfield.

The distribution of remaining oil in high water cut period has the very scattered characteristics in space. The calculation of the coarse grid can not meet the requirement of analogy precision at this stage, while the calculation of the fine grid will consume much memory storage of computer and calculation time, or even worse calculation can not be processed because of dispersion. In order to define the oil-displacing front of water and further quantify the remaining oil distribution at high water cut period, the dynamic local grid refinement (DLGR) technology was developed,which take water cut and saturation as the calculation standard. The DLGR technology enables the local refinement gird change with time, which can track the oil-displacing front of water. The calculation case using the coarse grid, fine grid and DLGR technology showed that the DLGR technology could achieve the similar result with the fine gird and reduce the calculation time by 80%. This technology could realize the same analogy precision of the fine gird and greatly increase the simulation speed while shorten the simulation cycle and save the calculation cost.

The composite hot foam system is an important replacement technique for enhancing oil recovery after polymer flooding and has some properties of the foam flooding and thermal flooding techniques and also has a certain effect of carbon dioxide and nitrogen flooding. In the laboratory experiment, the HY-3 surfactant was taken as the foaming agent, and the hot flue gas was chosen as the foaming gas, and sodium carboxymethylcellulose was chosen as the foam stabilizer. The experimental results showed that the effect of foaming agent and flue gas injection at the same time was better than that of them injected alternatively. With the increase of the composite hot foam slug, the oil-displacement pressure difference and oil recovery of foam flooding increased. The optimized foam slug was 0.6 PV. Adding stabilizer into the foam system could increase the strength of the composite hot foam system and the extent of enhanced oil recovery. After polymer flooding, extent of composite hot foam flooding recovery increased with temperature increasing. Under the condition of high temperature, the extent of enhanced oil recovery reached 16.29% for the composite hot foam flooding.

The nitrogen foam displacement fluid was developed to meet the demand for controlling water breakthrough in the reservoirs with high water cut in Daqing Sabei Oilfield. The oil-displacement test using three heterogeneous cores showed that the nitrogen foam injection technique could decrease the produced liquid ratio and water cut of high-permeability reservoirs more significantly than the polymer displacement method. The field test indicated that nitrogen foam displacement could control the breakthrough of injected water along the high-permeability zone effectively. As a result,the oil displacement efficiency could increase considerably. In fact, the content of water in the output fluid of the tested wells decreased from 93.9% to 90.2%. The output of oil increased by 16.4 tons, whereas the output of the produced fluid decreased by 41 tons per day. The accumulated output of oil is 3.486 tons in half a year. The oil production increase and the overall efficiency are significant, which suggests that nitrogen foam displacement fluid can enhance oil recovery of Daqing Sabei Oilfield effectively and has good prospect in oilfield application.

A new concept of response remaining oil saturation in polymer flooding was defined on the basis of reservoir numerical simulation. The macroscopic response mechanism of remaining oil was discussed. The places and shapes of response remaining oil in reservoirs with polymer flooding were investigated. The influences of reservoir rhythm, oil viscosity and the amount of polymer injection on the distribution of response remaining oil were analyzed. The research results showed that the response remaining oil vertically distributed in the upper parts of the cross-flow zones and took on the shape of spindle. The response zones were horizontally located between the injected wells and producing wells and took on the circular shape. The response mechanism and distribution of remaining oil were various in the different rhythm formations. The body of response remaining oil moved to the lower parts of formation, and the peak values of response remaining oil saturation declined with the increase of oil viscosity. As the injection amount of polymer increased, the boundary of response remaining oil extended bilaterally along the axis of spindle.

The pressure, temperature and oil saturation distributions and general thermodynamic characteristics of in-situ combustion zones with vertical well pattern in heavy oil reservoir were experimentally investigated by using 1D and 3D physical modeling systems. The experimental results indicated that five zones were characterized with distinctive thermodynamics from air injecting well to producing well, including burned zone, combustion zone, coking zone, oil bank and residual oil zone. The coking zone supplies the solid fuel for burning, while the high oil saturation bank with the largest pressure gradient in the formation is the main consumption zone of gas-injecting pressure. Maintaining a stable oil bank is necessary to ensure the forward movement of fire front, and fufill stable production and enhanced oil recovery.

The novel granular nutrients based on starch-cellulose for indigenous microbial flooding were developed. The activating process of the novel nutrient to the indigenous microorganism communities was investigated. The plugging and displacing effects of nutrients were evaluated by core-flooding experiments. The plugging and displacing mechanism of the nutrients were discussed. The research results showed that the indigenous bacterial populations could be effectively activated by the novel nutrients and significantly grown under the conditions of oxygen and no oxygen. The hydrocarbon-oxidizing bacteria and ferment bacteria were the dominant population. The novel nutrients could be metabolized to produce the useful bio-surfactant (rhamnolipid with fatty acids of saturated or unsaturated alkyl chain between C₈ and C₁₂) and bio-gas (CH₄ and CO₂) to emulsify oil. The core oil-displacement experiments of the heterogeneous model showed that the novel nutrient system could improve the oil-displacement efficiency and greatly increase the volumetric sweep efficiency. The recovery efficiency was improved by 12%~20% of OOIP under the experiment conditions. Field test suggested that the novel nutrients based on starch-cellulose could effectively plug off higher-permeability zones and divert the injected fluid into the low-permeability zones. The oil production rate increased remarkably with the declined water cut and the input-output ratio was more than 1 to 9.

About 50% oil was remained after polymer displacement and mainly distributed in the smaller pores of bypassed area by polymer displacement．The multi-slugs parallel gathering energy technology was developed, and its mechanism was described and identified in the paper. The plugging agents with different viscosity and quality were injected into three parallel cores to generate oil-displacement slugs in the different permeability zones, which could increase the partial displacement pressure gradient and oils remained in the middle and low permeability zones. The laboratory experiment showed that the oil recovery by water displacement after injecting two turns function slugs reached to 89.15%, which increased by 32.78% compared to the polymer displacement. The water-cut point of produced fluid was the lowest compared with the foam flooding, tri-combination flooding and polymer body expansion agent profiling. The produced fluid fractions of three parallel cores inclined to close and keep stable in a considerable extension, and the cross flow could be inhibited effectively. The heterogeneous experiment showed that oil saturations in the middle and low permeable zones decreased by 35% and 56% separately and changed little in the high permeable zone.Oil remained in the middle and low permeable zones could be employed greatly.The pressure difference changed with the movement of the injected slugs.The local pressure peak was located at the position of the slugs.The injected slugs approximately moved in parallel in the heterogeneous reservoir.

Based on the definition of reserves-production ratio (R/P), the production characteristics in the rising, stable and decline stages of oil production during oilfield development were analyzed. The new calculation methods of R/P in the three stages were present, and some relationship equations were built up among the reserves-production ratio, the production rising rate, reserves displacement rate, reserves-production balance factor and developed reserves factor. The study result shows that R/P changes irregularly in the whole process of oilfield development, but there is a stable value of oil production in every stage of the three development stages. The oil production rate and R/P value should be unchangeable in order to realize the stable oil production. An relationship equation among oil recovery factor, reserves replacement ratio and developed reserves factor was developed on the basis of definitions of R/P and oil recovery factor. The new methods can be used to match the index of oilfield development and analyze the reasonability of three ratios in oilfield development.

The 3D fracture prediction software is very necessary in the development of low-permeability reservoirs. A 3D mechanical model for predicting fractures in the low-permeability reservoir was established on the basis of the mechanical analysis and considering the efficiency of the fluid-solid coupling, non-linearity of rock material and dynamic effect of fracture propagation. The 3D mathematical mode for description of fracture dynamic propagation was achieved using the finite element method. The simulation of the model in Well Zhao 38-271 shows that the mean error rate of the calculated fracture shape is 107 percent compared with that of on-site testing, which can meet the requirements of engineering precision. The new simulation method can provide reliable and accurate prediction ways for hydraulic fracturing design and improve the successive rate of hydraulic fracturing technology.

The prediction of rock drillability is important for drilling and exploring engineer.In order to improve the accuracy of formation drillability,a new method for simulating the distribution of drillability field was discussed according to fractal theory,and the new method has been applied in the volcanic rock formation in Xujiaweizi.In general,the formation drillability is calculated based on well acoustic logging after the well completion.Using the well acoustic logging date and indoor experiments of drillability,a mathematic model for describing the relationship between the well acoustic logging and the formation drillability was established by regression analysis.Because the well acoustic logging had a fractal character with long range correlations by R/S analysis,a method of fractal interpolation was proposed to construct the distribution field of well acoustic logging.Random mid-point fractal interpolation method is one of the most popular methods.This method assumes that wells stand at the edge-corner point of the square.However,this situation always does not exist,so a weighted function with random mid-point fractal interpolation method has been put forward.Combining techniques of continental strata correlation and depth-normalization,the improved fractal interpolation method gets an accurate distribution field of well acoustic logging and drillability.The practice shows that fractal theory can successful reflect the macroscopic trend and microscopic heterogeneity of rock formation.Compared with the results of traditional methods,it can offer more reasonable explanation to the change of rock formation and higher prediction accuracy and excellent generalization.

The deep reservoir in the Block 3 of the center part of Junger Basin is commonly characterized by high initial water saturation, high capillary pressure, complicated structure, serous heterogeneity, high oil-gas flow resistance and natural fractures. Laboratory core tests confirmed that one of factors for severe damage of reservoir was water blocking effect caused by aqueous invasion fluids during drilling and production operations. The damage extent of permeability ranges from 49.3% to 89.2%. By adopting the liquid trap prevention method, ideal packing theory and d₉₀ rule,a high-performance drilling fluid was developed,which was composed of polyalcohol SYP-1, efficient water blocking preventing surfactant HAR and temporary bridging agents. The protection characteristics of fluid to reservoir were verified by compatibility test, surface and interfacial tension test, dynamic damage test and phase trap test. The test results and field data showed that the fluid system could satisfy the safe and fast requirement of ultra-deep drilling operation. The synergy of HAR and SYP-1 could efficiently minimize water blocking, reduce the surface-interfacial tension and improve the displacement rate of drilling fluid.

Foam drilling fluid has some special physical properties. The mathematical model for foam flow and heat transfer in wellbore was established, and the solution method of the model was proposed. In order to analyze the effect of heat transfer on the hydraulic parameters of foam drilling, the numerical calculation was conducted by employing the established mathematical model and the corresponding solution method. The results indicated that the temperature of foam in drilling pipe was always lower than that of foam in annulus and formation. The foam temperature at the bottom of annulus was lower than formation temperature,but the foam temperature at the top of annulus was higher than formation temperature. The deviation between foam temperature at bottom of annulus and formation temperature increased with the increases of well depth, liquid injection rate and gas injection rate. The wellbore heat transfer could result in quantity increasing of foam at top of annulus, quality decreasing of foam at bottom of annulus, pressure increasing at bottom of annulus, the minimum sand carrying velocity decreasing and the minimum gas injection rate increasing. The wellbore heat transfer could decreased the foam stability and the sand carrying capacity of foam,and it also could affect the foam density and Fanning friction coefficient. Although, the wellbore heat transfer had a certain extent effect on hydraulic parameters of foam drilling, the effect was limited and could be counteracted by increasing gas injection rate and back pressure.

The earthquake occurred in Wenchuan County of Sichuan Province resulted in seriously secondary geological disasters such as landsides and quake-formed lake. The Lan-Cheng-Yu pipeline passing through the earthquake area had also been seriously affected. For protecting the pipeline safety and supplying oil for disaster area, the PetroChina Pipeline Company applied the integrity technology to identify the threats affecting the pipeline safety and assess the risk grade. The protection and mitigation plans were developed. An integrity management program based on GIS was also used to graphically display the assessment results and provide information for operators to effectively allocate resources for appropriate prevention, detection and mitigation activities of safety improvement.

The down hole sucker-rod pumping system diagnosis technology widely used in oil fields is based on the relationship of polished rod displacement with time and the relationship of polished rod load with time to determine the running conditions of the whole system. In the survey of rod displacement, the abnormity rotation of dynamometer will cause some errors between the measured value and the true value of the polished rod,which further result in some deformation of polished rod dynamometer diagram and serve deformation of computed pump dynamometer diagram. A new sucker-rod pumping diagnosis technology was proposed on the basis of filtering treatment of measured displacement of polished rod. This diagnosis technology can filtrate displacement data and optimize the polished dynamometer diagram to reduce some errors and accurately compute pump dynamometer diagram. The new technology was verified to be credible and practical with the on-site data.

It is very difficult to resolve the problem about the dynamic fatigue reliability control simultaneously considering randomness and fuzziness of offshore drilling platform. According to the fuzziness of inspection results and failure criterion, a new simple fuzzy model for the dynamic fatigue reliability control of offshore drilling platform was proposed on the basis of the minimum cost per unit operation time model. Fuzzy model reckons the time effects of the capital and the loss of the failure of offshore drilling platform with time. The conclusion can also be generalized to the platform system. An example illustrated the validation of the proposed method. The effect of fuzzy uncertainty is very important for getting the reasonable dynamic fatigue reliability control.

There is no slip of viscosity liquids in casing and tubing under the condition of gas flowing out of casing head in gas-venting wells. The multi-phase flow models associated with Reynolds Number and roughness used in the petroleum industry usually lose their applicability. Based on the characteristics of casing annulus gas-venting wells, the particularity of multi-phase flow in the condition that the casing-head gas flows through a nearly stagnant liquid was investigated. Based on the theory of Taylor bubble, a model to calculate void fraction and pressure gradient in various viscosity liquids was developed. This model is applicable to bubbly flow and slug flow. The produced gas-liquid ratio of 10% at corresponding pump inlet was taken as a criterion to calculate and optimize the submergence depth of electric pump in the casing annulus of gas-venting wells. The application of this model to 40 various wells proved its reliability.

In the rotary steerable drilling system, there is a downward communication channel to send the guidance control command from the ground monitor to the down-hole steering tool. The negative pulse of drilling fluid transmits a downward command mode encoded by the three-descending and three-ascending words. A command-sending device on the ground transmits the command mode into flow rate of drilling fluid, which is changing with a certain pulse width of drilling fluid. A control word composed of five instruction codes represents the grade of guiding force and angle of tool face. There is a downward receiving device in the down-hole steering tool. The data acquisition unit of the device can detect the output voltage or frequency of the down-hole fluid motor that reflects the pulse flow change of drilling fluid. The data processing and interpretation software based on signal threshold judgment and pulse width identification can process the received information. Then a right guiding control command calculated using the pulse width and the sequence of the 5 codes could be obtained. Several different measures were used in the receiving device for improving the reliability and anti-interference performance of downward signal transmission. Experimental results showed the feasibility of this downward transmission scheme.

The geometric parameters, mechanical properties and external loading of casing have the stochastic property. The deficiency of the traditional method for design of casing safety factors was analyzed. An evaluation approach of casing reliability resistant to casing collapse and burst strength was established according to the structural reliability theory. The distribution regularities of casing strength were simulated by the Monte-Carlo random sampling method. The probabilities of casing failure and the correspondence with safety factors under different loading conditions were discussed. The study showed that the assessment method of casing failure risk could be used to quantitatively evaluate casing reliability. For the different types of casings and loadings, casing failure probabilities may not be equivalent under the same safety factors. The failure probability target level calculated by the established reliability method could provide foundations for selection of safety factors as well as design and evaluation of casing under uncertainty loading conditions.

According to the situation of oil and gas exploration,nine developing trends in the research of reservoirs are presented, including: ①developing petroleum reservoir-forming dynamics of basins and enforcing the research on the relations of geothermal field, geopressure field and geostress field with the rules of hydrocarbon accumulation and distribution; ②strengthening and deepening the research on the “non-structural reservoirs”, such as lithologic-stratigraphic reservoirs and hydrodynamic entrapment reservoirs; ③studying on the carbonate sequence stratigraphy; ④strengthening the research on the reservoir-forming rules of natural gas; ⑤researching on the reservoir-forming mechanism of superimposed petroliferous basins in China; ⑥paying attention to the research on the neotectonism and late hydrocarbon accumulation; ⑦researching on the unconventional gas resources; ⑧searching the inorganic-origin hydrocarbon reservoirs; ⑨further researching on the basin modeling. The above aspects are the hot and hard points of present and future research works. The strengthen research will definitely improve the development of petroleum industry of China.

The aborted oceanic basin is a special basin generated during basin evolution from epicontinental rift to ocean basin. This kind of basin is characterized by formation of the oceanic basement, which stopped expanding later and switched to depression. The tectonic evolution period of this type basin includes 3 stages of epicontinental fault subsidence, oceanic basement expanding and depression. The formation generated during the period of epicontinental fault subsidence belongs to the continental facies distributed near the margin of the basin. The formation formed during the period of oceanic basement expanding belongs to the hemipelagic or pelagic deposit, which passively overlapped upon the prior layer from the brim to expending center of the basin. The formation formed during the period of depression belongs to deep-sea plain deposit and deep-sea mudstone. The aborted oceanic basin has higher geothermal heat flow and gradient, which are favorable to the organic material thermal evolution and result in the smaller hydrocarbon-generating threshold value. The aborted oceanic basin might become significant province of deep-water hydrocarbon exploration activity, because of good matching of source rock, reservoir bed and capping formation.

Hydrocarbon accumulation period is the important content for researching the reservoir-forming pattern and hydrocarbon enrichment laws. The hydrocarbon source rock of the Upper Cretaceous Taizhou Formation in Subei Basin was only discovered in the eastern China at present. The history of burial, thermal evolution and hydrocarbon generation in the Upper Cretaceous Taizhou Formation were simulated. The fluid inclusions of 48 samples from the reservoirs in Taizhou Formation were investigated on the observation of lithofacie features and homogeneous temperature. The results showed that hydrocarbon source rock in Taizhou Formation experienced the continual subside-briefly lifting-secondary subside period. The divergences of hydrocarbon generation history and hydrocarbon accumulation period between Hai’an Sag and Gaoyou Sag were caused by the difference of subsides and lifting amplitudes. In Hai’an Sag, hydrocarbon of Taizhou Formation was generated from the Late Eocene Sanduo Period to the Quaternary and continuously charged and massively accumulated in the Pliocene Yancheng and Quaternary periods. Hydrocarbon of Taizhou Formation in Gaoyou Sag was generated from the Late Palaeocene Funing Period to the Eocene Sanduo Period and continuously charged and massively accumulated from the Eocene Sanduo Period to the Quaternary. The main charging timing of reservoirs matches with hydrocarbon generation and exclusion periods, which is favorable for petroleum accumulation in these areas.

On the basis of the interpretation and analysis of the seismic and drilling data of the northern Songliao Basin, the characteristics of the bottom boundary of Yaojia Formation (T11 boundary) were described and studied. Four groups of large-scale broad low-relief NNE fold belts below the T11 boundary were distinguished. The uplift amplitude caused by the four groups of fold-thrust belts decreased from east to west. The thickness of red palaeosoil beds developed in the T11 boundary also slowly gets thiner from east to west. The palaeontologic data suggested that there were several age-specific biomarkers on the upper and low surfaces of this boundary. The data of geophysics, sedimentology and palaeontology indicated that the T11 boundary was a regional angular unconformity formed in a compression regime during the post-rift thermal subsidence phase of Songliao Basin. The data from stratigraphy, palaeontology and isotopic dating ages revealed that the T11 boundary was formed during the period of the late Cretaceous (about 88.5Ma before present). This age is consistent with the time of a great reorganization between Pacific plate and Eurasian plate in the Mesozoic time. Therefore, the T11 boundary in the northern Songliao Basin was the responding surface to interaction between the Pacific plate and Eurasian plate in the Late Mesozoic. Since then, Songliao Basin had gotten into tectonic inversion evolution phase.

The Paleozoic carbonate stratum at the bottom of superimposed basins is very important for petroleum exploration in China. The evolution of pores, cracks and holes is responded to the formation and preservation of carbonate reservoirs. The strata unconformity and fault system are the important factors influencing the formation of carbonate reservoirs. Based on the different properties of fault system and control mechanism of the fault system to fracture evolution and induced karst of carbonate reservoir, the effects of four fault systems on carbonate reservoirs were researched, including the effect of fault overturning in the process of hydrocarbon accumulation and the formation of carbonate reservoirs, the effects of fault-related folds on the formation of different types of carbonate reservoirs, the lapping effects of multi-stages faults on the evolution of carbonate reservoirs and their characteristics of petroleum geology, the carbonate reservoir properties and hydrocarbon accumulation resulted from hydrothermal alteration induced by faults. The study result shows that the inversion faults are beneficial to the late accumulation of hydrocarbon under the ideal conditions of early extension and late burial as well as the fault-related folds beneficial to form the insider type of anticline reservoir. The fault-enrichment zone, multi-lapping faults and karst slope are favorable to the formation of effective strata and related hydrocarbon accumulation in the carbonate reservoirs.

The petroleum geological conditions of the first member of Yaojia Formation in the west of Daqing Oilfield were analyzed. The evolution history of the basin and the hydrocarbon generation-expulsion history of source rocks were simulated, and the dynamic conditions for hydrocarbon migration were successfully reconstructed using the basin modeling techniques. The characteristics of sandstone, unconformity and faults carriers were investigated, and a hydrocarbon carrier framework model was constructed. The coupling analysis on migration dynamics and pathways was made using the hydrocarbon migration and accumulation modeling methods as well as the percolation theory. The distribution of hydrocarbon pathways, migration directions and migration quantity of the first member of Yaojia Formation in Daqing Oilfield were obtained. Those study results combined with other petroleum geological conditions were used to prospect the target zones. Some favorable exploration zones such as Aonan nose structure,Da’an nose structure,Yingtai nose structure, Tahala area and the structure in the north of Bayanchagan were identified.

Anda Sag is adjacent to Sanzhao Sag in the northern Songliao Basin and has good petroleum geological conditions for generating petroleum. The shallow-middle layers in Anda Sag have displayed good oil and gas exploration potential in the recent years. But it is still a puzzle about the unclear oil source, which restricts the exploration in this area. The structural evolution relations of Anda Sag with the surrounding structural belts, such as Sanzhao Sag in the south of Anda Sag, Heiyupao Sag in the north, Daqing placanticline in the west and Mingshui terrace in the east, were studied using the balanced section. The assay data and geochemistry indicator show that Anda syncline is an isolated sag and possesses the conditions for forming the isolated hydrocarbon-generation kitchen. According to the oil-source correlation, the structural belts in the west and north parts of Anda Sag have great exploration potential and the further exploration object should be focused on the fault-lithologic reservoirs.

An efficient approach was provided to quantitatively evaluate mudstone source rock based on the studies of sequence stratigraphy，seismic facies,sedimentary facies,microphotography and geochemistry experimental data.Firstly,the distribution of potential source rock was forecasted using phase-controlling inversion restricted by reconstruct acoustic curve(AC),which reflected the abundance of total organic carbon(TOC),in different sedimentary facies of the sequence stratigraphic framework respectively.Combining with digital volume of the thermal evolution index generated from the geochemical experiment data and basin modeling simulation through Kriging interpolation, the distribution of high quality source rock was estimated. Accordingly,this innovative protocol was applied in Qingshui Sub-sag of Western Sag,Liaohe Depression,which can greatly increase the predication precise and has been forming the basis to the further exploration of this area.

There develops shale with rich organic matters in Longmaxi Formation of the Lower Silurian in Sichuan Basin. This shale with a great thickness is the source of shale gas and widely distributed in the basin. As the source,the shale is characterized as high organic content，good organic type and high organic thermal evolution degree.As the reservoir,there exits great quantity of cracks,porous and wrinkles,which offers sufficient accumulated space for shale gas. The isothermal adsorption test shows that the shale has strong ability of gas adsorption. The structural condition in this basin is available for forming shale gas reservoir. The gas shows of many wells drilled in the shale strata of the Lower Silurian in this area indicated the great potential of shale gas. The shale indexes of thickness distribution, organic carbon content, thermal evolution degree and gas generation level in Sichuan Basin show that Yibin-Zigong-Luzhou and Dazhou-Wanxian areas are the favorable zones for shale gas exploration.