With the great development of China's oil and gas exploration in recent years, some new petroleum geological phenomena couldn't be explained with the known knowledge of petroleum geology theories. It is important to input new theoretical concepts from several aspects. The rich-hydrocarbon depressions have the characteristic of "Sag-Wide Oil-Bearing", which means that there are very high probability of oil reservoir formation owing to alternations of source rocks and sheet sandbody in the rich-hydrocarbon depression. The exploration scope can be spread from "secondary structural zone" to the whole sag and depression. There are new geological features for the middle and deep parts in the superimposed basins. The retarding process of hydrocarbon generation under overpressure can widen and deepen the liquid hydrocarbon window, which provides more chance for finding liquid hydrocarbon in deep horizons. The distribution of deep horizon reservoirs experiencing multiple-stage tectonic movements is inconsistency with the theory of "source kitchen control theory". Under the control of early reservoir formation, later burial, resistant compaction due to overpressure, structural uplifting as well as halite "suspension" and secondary diagenesis, there are favorable reservoir rocks in deep horizons. The oil-bearing and gas-bearing abundance of secondary structural zones in the multistage superimposition process varies largely. There developed over-late reservoir in the deep formation under annealing geological background. The high-efficiency formation of natural gas reservoirs is controlled by time-space matching of hydrocarbon generation, reservoir formation process and combination of formation elements. Therefore, hydrocarbon generation thermodynamics was introduced to the evaluation of gas source kitchens. The concept of high-efficiency gas source kitchen was proposed, and the new evaluation index was established in this paper. The preserve mechanism and distribution rule of efficient process of reservoir formation and excellent elements of petroleum system in petroliferous basins of China were analyzed.

The Permian-Jurassic alluvial-fan, subaqua-fan and delta-fan were widely distributed in the west-north margin of Junggar Basin. Their genesis and distribution are relative with the contemporaneous action of faults. Tectonic movement in this area gradually weakened from the Permian to the Jurassic period, and the dimensions of fan was reduced step by step. The movement of tectonic activity resulted in transfer and superimposition of various fan. Since the tectonic movement in Baikouquan-Xiazijie area was strong and extended for a long time, there developed some fans with large dimension, good superimposition and obvious migration. Contrarily, the tectonic movement in Chepaizi-Zhongguai area was weak and resulted in some small fans with poor superimposition and less migration. Fault and fan controlled the oil-gas gathering in this area. The active regularity of the faults is obviously different, which results in the fans developed in different stratum and causes the different oil-gas distribution.

Qingtang Basin is a large Mesozoic marine sedimentary basin located on northern Qingzang plateau and has the widespread and thick source rocks. The source rocks of Xiaochaka Formation in the upper Triassic and Buqu Formation and Xiali Formation in the middle Jurassic were researched by organic geochemistry means. It is found that the organic matter type of source rocks is good, and abundance of organic matter is large. The maturity of organic matter varies from mature to over-mature, and the burial conditions of source rocks are relatively good. The simulation of hydrocarbon-generation process revealed that source rocks had two periods of hydrocarbon generation and hydrocarbon expulsion. The production of hydrocarbon is extremely large. The fossil-reservoir belt located in dolomite of Buqu Formation in the Bilongcuo-Angdaercuo region has a length of 100 kilometers and a width of 20 kilometers. It is a long and narrow humid swarm with light oil. The organic geochemistry characters of oil-source rocks show that oil and gas of the fossil-reservior come mainly from the hydrocarbon rock in the lower Jurassic. The discovery of the fossil-reservoir belt implied that Qiangtang Basin had large-scale migration and accumulation of oil and gas. It will have a good prospect for exploration of oil and gas.

The Ordos Basin is the secondary biggest sedimentary basin of China. Four giant gas fields had been proven in the basin, including Sulige, Yulin, Wushenqi and Jingbian gas fields with proven reserves over 100 billion cubic meters for each gas field to the end of 2002. The hydrocarbon source rocks of the Sulige, Yulin and Wushenqi gas fields are coal measures of the Upper Paleozoic. The Jingbian gas field was found in the carbonates of Majiagou Formation in the Ordovician of the Lower Paleozoic. There are still existing arguments about the gas sources of Jingbian gas field. The alkane carbon isotopes analyses of 125 gas samples collected from the above-mentioned four gas fields show that the carbon isotopes of giant gas fields in the Upper Paleozoic are heavy, and the range of values is narrow. The gases are characterized by coal-formed gas. The δ ¹³C _iC4 value is bigger than the δ ¹³C _nC4 value. Reversal of carbon isotope values in single type appears in the Upper Paleozoic gas fields. In the Lower Paleozoic Jingbian gas field, the δ ¹³C ₁ dominant peak values, the δ ¹³C _B values and the δ ¹³C _T values are similar to those in the Upper Paleozoic. However, there are still some different characteristics in Jingbian gas field from other three gas fields. The reversals of carbon isotope values are of multiple types. The values of δ ¹³C ₁,δ ¹³C ₂ and δ ¹³C ₃ are ranged widely, and the δ ¹³C ₂ value is smaller. These characteristics show that the gases are mixed from mainly humic and some sapropelic sources. It is suggested that the humic and sapropelic sources are all from C-P coal measures and the Taiyuan Formation carbonates with a high abundance of organic matter in the Upper Paleozoic rather than the conventional idea suggested that sapropelic gases are mainly from the Majiagou Formation carbonates with the total organic content of 0.20 %.

Based on the new 3D seismic data, the complex structural characteristics and the difference of oil and gas accumulation in Tazhong No.1 Structural Zone were studied with the isochronous sequence framework and structure analysis. It is indicated that Tazhong No.1 Structural Zone is a complicated faulted slope break resulted from a large thrust belt eroded for a long time from the end of the early Ordovician to the early of the late Ordovician. A composite of carbonate reefs and banks of platform margin in Lianglitage Formation of the Upper Ordovician was developed along the carbonate slope break. Tazhong No.1 Faulted Slope Break can be divided into five parts with different geometry and development characteristics by the accommodation of transfer zones,which caused the difference of oil and gas accumulation. The thick composite of carbonate reefs and banks in rimed shelf is located in the Tazhong-44 Block. This area is the favorable exploration district and has high and stable production of carbonate along the slope break. There are intensive structural effect and Karst process in Tazhong-45 Block. This area has an advantageous prospect for a large scale fracture-hole reservoir. The two zones are main exploration targets for large oil and gas fields.

The lower-paleozoic marine carbonate rocks in North China Basin were generally characterized by low abundance of organic matter and high maturity. The low abundance of organic matter was caused by the sedimentary environment. Lithology, rock texture and sedimentary structure proved that the North China Basin in the Lower Paleozoic was mainly in the shallow inland sea and lagoon, where water was unquiet and salty. The evaporation rate was high, and the sedimentary environment was unfavorable for low-grade living beings to grow and be preserved. The high maturity was caused by the deep-seated metamorphism produced in the Mesozoic-Cenozoic period. Especially, when the Mesozoic was covered by the low-middle Triassic Formations with the thickness ranged from 2000 meters to 2500 meters, the buried depth of the Lower Palaeozoic source rocks was over 3000 meters, which resulted in the early-hydrocarbon-generation fully. According to the data of 1500 samples, the organic matter abundance of few samples exceeds 0.5 percent, and their average value is less than 0.2 percent. The content of chloroform bitumen "A" is lower than 0.012 percent. The average concentration of S ₁+S ₂ is lower than 0.2mg/g. All these indications are inaccessible to the standard of effective oil source rock. The TTI- R _o conversion and strata correlation were used to recover the sedimentary environment of the low-middle Triassic carton basin. The calculated thermal metamorphic grade of the Lower Paleozoic at the end of Triassic is higher than 1.2 percent, which accords well with the present distribution of thermal metamorphic grade in North China Basin.

Exploration researches on lithologic and stratigraphic reservoirs in Erlian Basin and Jizhong Depression in recent years reveal that the different trap-forming mechanism and variance of reservoir-forming control factors resulted in unique distribution of lithologic and stratigraphic reservoirs compared to the structural reservoirs. Lithologic and stratigraphic reservoirs were mainly distributed along the "flood surface, unconformity surface and fault surface". Those reservoirs could be distributed in the low or high potential areas and developed in the low system tract (LST) or the high system tract (HST). The distribution of lithologic reservoirs was mainly controlled by depositional system, and the distribution of stratigraphic reservoirs was mainly controlled by truncation zones and overlap zones. The enrichment degrees of them were mainly controlled by sedimentary facies and reservoir facies belts. The exploration of lithologic and stratigraphic reservoirs should be taken into attention. Exploration units must be reclassified by taking sedimentary system, stratigraphic overlap and denudation as the main control factors. More attention should be paid to the study on reservoirs controlled by the "flood surface, unconformity surface and fault surface" as well as by the sedimentary facies and reservoir facies. The exploration domains should be extended from ring sag to troughs, from positive structural areas to negative structural areas, from structural highs to structural flanks, and from structural zones to lithofacies zones, overlap zones and denudation zones.

The Ordovician reservoir in Tahe Oilfield experienced many tectonic reconstructions and was characterized by multiple hydrocarbon charging. Based on 105 Ordovician core samples from 10 wells of Tahe Oilfield, systematic analysis of fluid inclusions was employed to study the complex hydrocarbon charging histories. The results of fluorescence observation on petroleum inclusions and microthermometry of both petroleum and aqueous inclusions indicated that the Ordovician reservoir of Tahe Oilfield experienced five thermal fluid activities corresponding to four times of petroleum charging and one time of gas charging. Comprehensive analysis of fluid inclusion and the burial history curve shows that the four times of hydrocarbon charging happened in the late Hercynian, the Indo-Sinian and Yanshan, the early Himalayan and the middle Himalayan respectively. The gas charging happened in the late Himalayan. The integrated information suggests that the critical moment for petroleum charging is in the late Hercynian.

The conventional inversion for time domain is unfavorable to cross-hole seismic data in depth domain. An appropriate velocity model for depth-time conversion was constructed. The data can be converted from depth domain to time domain. The inversion result obtained in the time domain can be converted back to depth domain for reservoir interpretation. The constraint model for wave impedance of cross-hole seismic data was developed. The depth-time conversion of wave impedance profile in the time domain was made, and the wave impedance profile of cross-hole seismic data in the depth domain was obtained. The converted wave impedance profile and the seismic data in depth domain can be directly used to analyze reservoir property.

The method for prognoses of thin reservoirs by combing seismic high-resolution inversion technology and geological simulation was presented. The relative stability of reservoir and the response of geophysical field of the thin reservoir in Shahejie Formation of Minfeng Sag in Shengli Oilfield were analyzed. The inversion technologies of seismic wavelet including multi-scale decomposition and high-resolution were used to analyze the interval transit time. The primary geological model was developed. The reservoir parameters, log data and seismic data were applied to simulate the geological model and to predict the thin reservoirs of Minfeng Sag. The simulation shows that for the stratum more than 3000 meters in depth, the thin reservoirs from five meters to eight meters in thickness can be prognosticated.

Turbidity sand widely developed in the deposit center of Dongying faulted basin is closely related to source rocks and favorable to form lithologic reservoir. But it is difficult to quantitatively predict oil-gas-bearing property in turbidity sand. The characters of plentiful reservoir proved to be turbidity sand reservoir by drilling were analyzed. In combination with tested and simulated data, the key factors controlling reservoir-forming in turbidity sand were discussed. A threshold value of relative indexes for evaluating oil-gas-bearing property was given. The results show that expulsion intensity of hydrocarbon in surrounding rock is the most important factor of reservoir-forming. If hydrocarbon resource rock is abundant in turbidity sand, the main factors affecting the oil-gas-bearing property include reservoir property, drive force and resistance force of reservoir-forming. The surrounding rock with an hydrocarbon-expulsion intensity greater than 200 thousands of tons per square kilometer and the dynamic reservoir-forming index greater than 0.15 is favorable to form the reservoir with high-fullness hydrocarbon, while the turbidity sand with thickness less than two meters and porosity less than 12 % is unfavorable for reservoir formation.

The quantitative calculation of shale smear and some unresolved problem were researched based on the phenomenon of shale smear, fault sealing mechanisms and its controlled factors. The shale smear was controlled by fault throw, lithologic association and shale plasticity. According to structural history and compaction history, the first active period of fault,buried depth of formation and faulted formation plasticity can be determined. Furthermore, the shale smear may be counted if shale smear occurred. The study of shale smear shows that hydrocarbon remigration happened along a few layers in south fault of Ying 32,because the sealing property of a few important layers was poor, which made hydrocarbon migrate across the fault,while all oil-bearing layers were sealed in the north fault of Ying 32. All those indicated the difference of sealing properties and dynamic state for the same fault.

The uncertainties of a gas reservoir located in the north part of Shaanxi Province were studied with stochastic modeling. The responding gas reserves of the reservoir were calculated with three groups of data obtained from two hundreds and fifty four wells, one hundred and forty six wells, thirty wells by using fifty, one hundred and two hundreds of random seeds, respectively. Probabilistic distributions of these reserves were analyzed. Three probabilistic reserves (P90, P50, P10) for the three groups of data were obtained respectively by using one hundred of random seeds. The probabilities of three probabilistic reserves larger than the real reserves are 90 percent, 50 percent and 10 percent respectively. The calculated results illustrate that as the number of wells increase, the mean values of gas reserves continuously increase, and their mean variances decrease, which results in the reduction of the uncertainties of reservoir. The top strata surface and net thickness were obtained by Kriging method. The spatial distributions of porosity, permeability and gas saturation were obtained by simulation of Gaussian field.

Flow unit is the smallest macro-geological unit in oil and gas reservoir. By the use of laboratory displacement test of core samples with different porous volume factor, logging parameter evaluation data of completed wells in different development period and a number of production performance data, the evolution laws of reservoir's macro-physical property parameters for flow units with different genesis in the course of waterflooding development were studied and analyzed. The mathematical evolution models for each kind of parameters were established. The variation factors for corresponding physical property parameters were found out. The 3-D geological model of working station for establishing software "Earthvision" was used to load variation factor of physical property parameters on the basis of the original 3-D geological parameter models. The data processing and result extraction were made. The four-dimensional dynamic evolution realistic serial models for different flow units in the course of development were developed. So, oil and water flow characteristics and residual oil distribution inside the flow units in different development phases can be predicted with the models.

According to the results of the research in the laboratory and field tests, the experiences of polymer flooding in Daqing Oilfield in seven years were analyzed. The actual recovery in the field and the major factors influencing recovery efficiency were investigated. The methods for enhancing recovery efficiency, the measures to obtain a uniform polymer flooding front and the ways to lower the costs for producing crude oil by polymer flooding were discussed. The effectiveness of polymer flooding technology applied in Daqing Oilfield can provide some references for further application of polymer flooding in China.

Taking Gangdong development area of Dagang Oilfield with mid-later developing phase as an example, some geology and drilling-exploitation engineering factors controlling residual oil formation and distribution including the seepage discrepancy of inner layers, plane and inter layers, positive micro-structure of oil formation, updip pinching of sand bodies, default shielding, non-perforated oil layers and well condition deterioration were investigated. The results show that the key geology factor affecting residual oil formation and distribution includes the reservoir seepage discrepancy. The vertical inner seepage discrepancy led the residual oil to be mainly distributed in the mid-upper sections of positive rhythm sands. The important residual oil abundance zones are in the sand amalgamation belts on plane, and the relative low-permeability areas are in the major sand boundaries. The non-coupling property of geology factors such as size and shape of sand and inter seepage discrepancy to the engineering factors such as well deployment led to the combination of multi-operating mechanism such as injection-production well pattern imperfect, non-controlled well pattern, injection-production relation inefficiency. The different kinds of residual oil distribution, such as plane residual oil stagnant area, non-producing oil sand body, suppressing high pressure residual oil layers, are easy to be formed.

The cyclic carbon dioxide injection technology to improve heavy oil production after steam soak was studied by physical simulation. The mechanisms of cyclic carbon dioxide injection were investigated. The results show that injection of carbon dioxide into heavy oil reservoir in the late steam soak period can increase expansion energy and decrease oil viscosity and also demulsify the emulsion formed in the steam soak process. In general, carbon dioxide dissolved in the heavy oil can reduce oil-water surface tension and result in breakdown of emulsion. Also, the injected carbon dioxide can change oil-water relative permeability and lower the remaining oil saturation. The field pilot test shows that cyclic carbon dioxide injection after steam soak is successful in technology and has the economic benefits. Both physical simulation and pilot test show that cyclic carbon dioxide injection technology is economically feasible to improve the development results after multi-cycle steam soak for heavy oil reservoir.

The numerous existing methods for prediction of oil and gas production were reviewed, and a multi-model combined forecast method based on fresh degree function was developed. This method was derived from the single-model prediction technique. The fresh degree function is brought into the multi-model combined forecast method, which can effectively describe the varying trend of the data list and improve the self-adaptive recurrent algorithm and fuzzy variable weight combined forecast method to some degree. So, the improved model can not only adopt useful data of different methods but also make the weight coefficient of combined forecast being time-varying. This method has the features of high precision and high accuracy of prediction, good adaptability and simplicity of calculation.

The recovery ratio, exploitation degree, drainage range and the production forecast of single coal-bed methane (CBM) well were discussed by using the production data of Zaoyuan well pattern. By the end of November 2003, the total accumulative production of CBM in Zaoyuan well pattern was 9.7979 million cubic meters. The recovered percentage was 2.2 percent. It is estimated that about 236 million cubic meters of recoverable CBM reserves has not been extracted from the coal beds of this well pattern. At present, Zaoyuan well pattern stands in initial stage of production. The range of single well drainage is less than 10 acres, and these wells have not been connected with pressure produced itself. It is predicted that the average gas rate of single well would be from 2500 cubic meters to 3000 cubic meters per day, after a larger range of pressure drop funnel was formed. So, the well space was suggested to be 20 acres to 25 acres.

The mechanisms of formation blockage were analyzed. The principles of newly developed high pressure water jet technology combined with acidization for treating perforations and formations near wellbore are introduced. The applied results of thirty oil wells and water-injection wells in Shengli Oilfield and Huabei Oilfield indicated that this technology is characterized by simple procedure, high success ratio, wide feasibility and remarkable effectiveness. It has a good prospect in the application of production increment and augmented injection as well as enhanced oil recovery.

It is important to consider adding drag reducer for the transportation technology when making an optimization design project of crude oil pipeline. Two mathematic models for describing the relationship of hydraulic pressure gradient and drag reducer concentration with the flow rate and viscosity of crude oil and the diameter of pipeline were established. The regression parameters of the two models were obtained from the two models by genetic arithmetic (GA) optimizing technology. The two models were inspected with the actual examples. The biggest error is 2.9750 percent. On the basis of those two models, the mathematic models for optimizing designs of crude oil pipeline with and without drag reducer were proposed and solved by combining the genetic arithmetic algorithm with discrete variables, multiple forms of mixed discrete variables and database technology. This method can guarantee the reliability and veracity of the optimized solutions and also speed up the search for the optimized solutions. The solution process of the mathematic models for optimization design of crude oil pipeline is given. The example of calculation shows that the effect of the prices of drag reducer, electricity and fuel on the annual converted costs and the operating management costs must be considered when making optimization design adopting transporting plans with drag reducer. The optimum project of the calculated example is that the optimizing design considering the transportation technology without drag reducer at the average flow rate of oil is made firstly. When the flow of crude oil rate exceeds the average value, the optimizing operation using the transportation technology with drag reducer should be considered.

A model for expressing the change of backscattering flux of foam drilling fluid with time was established, according to the optics property of foam drilling fluid. Furthermore the concept of specific surface area of foam was presented to describe the stability of foam. The mathematical model was established to correlate the specific surface area of foam with time utilizing light backscattering theory and backscattering model. The stabilities of three samples of foam drilling fluid with different density were evaluated by employing infrared scanning turbiscan. The stability of foam drilling fluid was analyzed. The parameters of the backscattering flux ratio model were acquired by data regression. The comparison result of decay rate and half-life verified the correctness and feasibility of the optics evaluating method.

A 3D finite element model for calculating the casing stress in the directional wells was developed based on the theory of coordinate conversion. The rock laboratory tests and conventional casing sizes in the field were used to calculate the maximum effective stress varying with deviation angle and azimuth angle under different combinations of in-situ stresses and formation property. Three different situations were considered for the in-situ stress. (1) The overburden stress is the maximum principal one, and the horizontal stresses are uniform. (2) Similar to situation (1), but the horizontal stresses are non-uniform. (3) The overburden stress is the middle principal one. It is found that the casing stress in the directional well is significantly affected by the complex in-situ stress field, well track and the formation property. An optimal well track exists for any combination of these factors. All these factors should be carefully considered in the casing design process.

The system efficiency is a primary index for evaluating pumping system. The quality of measured parameters has a great influence on the efficiency of pumping system. According to the analysis compendium of uncertainty, the uncertainty analysis models were established. The assessment method of uncertainty components in class A and class B was introduced. A combined calculation method of normal uncertainty and extended uncertainty was presented. An artificial lifted well system was taken as an example to illustrate the proposed method. The calculated results reveal that the impact factors for the uncertainty of the measured values include numerical reading of electric energy meter, tubing pressure, casing pressure, liquid production, liquid density and producing fluid level of artificial lifted well system. It is important to lower the uncertainty of these factors in order to decrease the uncertainty of measured result.

The basic constitutive characteristics of a sort of beam-pumping unit with a new balance system were described. The balance principles were discussed, and a virtual prototyping model was established. The assumption terms in the model and the basic methods for examining the virtual prototyping model were discussed. The constraint infliction principles in the establishment of the virtual prototyping model were analyzed. The dynamic property of the new pumping unit was investigated with software for virtual prototyping technology. The curves of force acted on the articulated points of main parts and the torque curve of crank were obtained. The analysis result indicated that the force status on the articulated points of the main parts was obviously improved, and the opposite force existing in the common beam-pumping units was canceled. The torque curve of crank was unchangeable, and the opposite side torque was reduced obviously. The balance function of the new type beam-pumping unit was improved. A good energy-saving result has been obtained.

In order to design the rod string and analyze failure mechanism, the dynamics analysis on rod string of surface driving screw pump must be conducted. A nonlinear dynamics model for describing the impact contact state between rotating rod and tube was presented. In consideration of the impact contact between rotating rod and tube that happens in any direction of well depth and well bore circumference, the dynamic gap element to describe the random impact contact state between rotating rod and tube was constructed. A rotating rod dynamics analysis method was proposed by combining the dynamic gap element with space beam element. This method has been applied to the B2-6-41 Well in Daqing Oilfield. It is shown that the relative error between calculated average value and actual test value of the rod torque at well head is 1.5 percent. The dynamic strength of rod string and the mount position of centralizer were calculated, according to the acquired deformation of rod string and its impact contact force with tube in the time domain. The designed rod string with this method can safely run in the well for longer time, which makes pump-inspection period over 550 days. This method can also be widely used in other Oilfields.

Compound hydrocyclone is a new hydrocyclone based on the advantages of dynamic cyclone and static cyclone. The internal flow field of compound hydrocyclone was simulated using amended RNGK-ε model. The simulation result is in accordance with the experimental data,which proves the correctness of mathematical model and computation. The numerical simulation values of axial velocity and tangential velocity are very approach to the experimental result. The simulated distribution law of radial velocity benefits the cyclone structure and performance analyses. The mathematical model and computing method can be used to forecast the internal flow field of compound hydrocyclone and can also provide an effective way for the study of compound hydrocyclone such as separation mechanism, flow field characteristics and structural optimization design.

Four opinions about sustainable development of petroleum resource in China are presented.Firstly,the peak annual output of crude oil in China will keep to about 0.18 billion tons.To keep the peak annual output longer is favorable for petroleum supply security.Secondly,the discovery of big oil-gas fields will go along with the discovery of "low-quality reserves" in a long time.When exploring big oil-gas fields,it is necessary to explore "low-quality reserves".Thirdly,the recovery of crude oil in China should approach in the economic policy of "more wells and low output".Finally,the new exploration areas unknown to us now will greatly affect the prospect of petroleum resources in China in future,such as Nansha areas in South China Sea,Tibet Plateau and deep water aktian deposit areas in north of South China Sea.

There is great gas exploration prospect in Junggar Basin,because of the high resource assessment and low exploration degree.Gas migration is controlled by regional tectonic movements.Migration direction and accumulation area are controlled by fluid potential.The faults and unconformity are the main migration pathway.Abnormal pressure is the main power of gas migration.All the geologic and accumulation characteristics accord with the features of deep basin gas.Thus,updip direction of slope and paleohigh are the migration direction and favorable accumulation area,and foreland thrust nappe structure is oil and gasbearing belt with great potential.There are multiple abnormal pressure compartments in deep horizons of frontal zone of the basin.These areas have the geologic characteristics to form deep basin gas trap and will be the important gas exploration targets.

Huge natural gas resources have been proved in the Kelasu Thrust Belt of Kuche Depression.In spite of many structural traps developed,this belt had encountered high risk of hydrocarbon exploration for tens of years.The investigation of geology,drilling and geochemistry shows that a huge gas reservoir was formed in the main expelling pathway for overpressure fluid system under the seal of Eogene gypcrete/salt due to compression stress.The overpressure fluid expulsion occurred preferentially along those thrust faults which cut across the sealed gypcrete/salt bed of the least thickness in the vicinity of belt.The overpressure fluid expelling leads to pressure reduced and then causes gas up-migration along the faults down through underlying Triassic-Jurassic source rocks.In general,the main expelling pathway of overpressure fluid controls gas accumulation in this area.

The existence of mixed crude in western arc structural belt of Taibei Depression in Turpan-Hami Basin is explained,according to some characteristics of crude oil such as biomarkers and carbon isotope ratio.On the basis of the principle of material balance,a mathematical model for hybrid scale of mixed crude was established by the use of αααRC ₂₇ percentage of two kinds of crude oils including crude oil derived from coal measures and crude oil originated from limnic shale.The hybrid scale of mixed crude was calculated by using the mathematical model and the parameters of biomarkers of two kinds of crude oil.The spectrums of sterane and terpane were simulated and compared with some parameters and spectrums of actual mixed crude.A satisfactory result has been obtained.The distribution characteristics of different kinds of crude oil in this structural belt were determined.

Deep basin gas trap is considered as the prospective target of gas exploration and research in recent decades.The exploration methods for deep basin gas trap are based on integrative study of geological theory,exploration strategy and engineering techniques.In detail,the integrative study consists of the following three indispensable aspects:① Emphasis on study and application of geological theory for deep basin gas trap during the exploration process;② Multi-subject integrative study on the exploration method based on the specific geological features of deep basin gas trap;③ Improvement of drilling and production techniques.The application of the integrative exploration method for deep basin gas trap in Tongnanba Structural Belt of Sichuan Basin proved the feasibility of this method for identifying the deep basin gas trap.The geological and seismic data indicated that Chixi Syncline has formed "pressure compartment" with favorable source-reservoir-cap rock assemblage and become the prospective area for exploration of deep basin gas trap.The systematic factors/elements of deep basin gas trap were analyzed,and a geological model suitable for deep basin gas traps of Tongnanba Structural Belt was proposed.It is suggested that under the condition of regional geo-pressure transforming zone in the syncline of the structure,and the terrestrial formation from the bottom of Upper Shaximiao Formation to the top of Lower Shaximiao Formation,the local overpressure areas are the important spots for exploration of deep basin gas traps.It is recommended to make further study and to design a wildcat well in this area.

According to evolution stages of expanded basin,characteristics of tectonic action,property of fault,distribution of depositional system and sand-body,the slope break was classified into two styles of fracture slope break and flexure slope break.The genesis,difference and exploration fields of the fracture slope break and flexure slope break were analyzed.By using multiple information,genesis and distribution scope of the flexure slope break,reservoir styles and seal condition in the south of Songliao Basin were discussed.The favorable exploration fields and prospective blocks were presented.

The sandstones in second and fourth members of Xiangxi Formation of the Upper Triassic are the main natural gas reservoirs in Sichuan Basin.There has got good exploration and exploitation results recently.The sandstone of second and fourth members of Xiangxi Formation with stable thickness and high mineral maturity are distributed in the area of about 100 thousands of square kilometers in Sichuan Basin.The thicker bed always shows reverses graded bedding and develops tempestite,washing stratification and wedge-shaped cross-bedding or planar stratification with 180°angles with each other.GR curves usually show box girder.The whole bed has alternating layers with five percent to ten percent of carbonaceous mudstone and thin coal layer.In the depositional period of second and fourth members of Xiangxi Formation,the mountains all around Sichuan Basin were in the tectonic movement.The sediments brought into the lake by alluvial fans and rivers were washed and removed by wave and lake current and then formed bank-bar sandy body along or near the lake shore.With the migration of lake-coast line,the bank-bar sandy body was migrated perpendicularly to or along the lake-coast line and finally formed sandstone distributed in all over the inner basin.A sedimentary model in the second and forth members of Xiangxi Formation of the Upper Triassic of Sichuan Basin is presented.

There developed tight formations and low-porosity and low-permeability reservoirs in Anpeng deep zones of Biyang Depression.The natural fractures were well developed in the reservoir.Lots of fractures are in the form of high degree or vertical type and belong to the extension and shear fractures.The fracture identification technologies such as the oriented core technique and acousto-electric imaging log were used to get the occurrence and distribution of fractures.The analysis on reservoir depositional system indicates the genesis mechanism of Anpeng structural nose and its connection with the generation of reservoir fractures.

The leading passages of mantle-genetic carbon dioxide reservoir and inorganic alkane hydrocarbon reservoir found in Xujiaweizi Rift of North Songliao Basin were discussed.The tectonic characters of deep layer and high abnormal thermal-flow of Songliao Basin show that the crust low-velocity and high-conduction zone in the deep layer of Songliao Basin may be the magma chamber accumulated in the mid or lower crust and produced from the partly melting inside mantle under the interaction of crust and mantle.The low-velocity and high-conductivity zone may also be the melted lava inside crust under the conditions of high thermal flow and shortage of water.The analysis on geophysical data and geochemical data of deep layer in North Songliao Basin suggests that the low-velocity and high-conduction zone in crust of deep layer in Songliao Basin is a mid-station for transferring mantle-derived carbon dioxide into the shallow reservoir by magmatism and volcanism.

The sedimentary history of Wuerxun Depression includes a few stages corresponding with structural evolution.The result of sequence stratigraphy research shows that the Cretaceous strata in this area involve two first-order sequences,five second-order sequences and twelve sequences.These sequences take on many obvious surface characteristics and abundant sedimentary systems.The sedimentary history includes two major growth cycles.The first cycle started from T ₄,and the second cycle is a non-integrated cycle started from T ₀₄.The general tectonic framework controls the form of the depression and the distribution of the depositional systems in the accommodation,which is the fundamental reservoir formation condition.Furthermore,the strata and the depositional systems are the essential physical reservoir formation condition.The major potential hydrocarbon resources are the dark mudstones of the condensed sections in sequence 4 and sequence 5 of second-order sequence Ⅱ and Ⅲ.The favorable reservoirs are mainly involved with lowstand fan,lowstand wedge,highstand delta front,highstand fan delta front and the turbidity fan in these two second-order sequences.