According to the drilling and seismic data,the Late Sinian-Early Cambrian intra-cratonic rift was found in Deyang-Anyue area of the Upper Yangtze craton.This rift is controlled by tensional fault and distributed in NNW trending with the NS length of 320 km and EW width of 50-300 km.After three stages of rift evolution,i.e.,the forming stage,developing stage and dying stage,a favorable near-source accumulation assemblage was formed.The research results indicate that:(1) the sedimentary stage of Late Sinian Dengying Formation is the rift forming stage,during which trough-basin facies sedimentation is developed in the rift,while platform marginal facies mounds and shoals are developed on both side,controlling the formation and distribution of high-quality reservoirs in Dengying Formation;(2) the sedimentation stage of Early Cambrian Meishucun-Qiongzhusi Formation is the rift development stage,during which deep-water continental shelf facies argillaceous rocks are filled in the rift with a thickness of 500-1000 m,indicating the sedimentation stage of high-quality source rocks;(3) the sedimentation stage of Canglangpu Formation is the rift dying stage,terminating the evolution history of intra-cratonic rift by gap filling.The intra-cratonic rift is a key factor for the formation of Anyue giant gas field,where the high-quality source rocks provide abundant gases for the giant gas field.A regional lateral sealing occurred during the rapid rising of the western paleo-uplift in Central Sichuan during the Late Yanshan-Himalayan period,favorable to the preservation of the Gaoshiti-Moxi giant gas field on the east wing of the rift.The intra-cratonic rift and its role in giant gas accumulation provides a significant reference for deep oil and gas exploration in paleo-craton basins.

Sinian Dengying Formation was developed extensively as an important natural gas reserving and producing formation in Sichuan Basin.New evidences for micro-petrography and fluid inclusion salinity data in terms of dissolution were obtained through comprehensive research of reservoir petrography and sedimentology,reserving space types,diagenesis and evolutionary sequence,especially thin section identification,SEM identification,and the analysis of element,carbon and oxygen isotope as well as fluid inclusion.It is considered that Dengying Formation has the typical characteristics of facies-controlled dolomite karst reservoirs in terms of reservoir genesis.The main control factors for reservoir development include special sedimentary and diagenetic environment as well as multiphase and multi-type dissolution and failure.Special sedimentary environment is prominently represented as large microbe reef flat and mound flat bodies under the control of dry-hot/arid paleo-climate.These sediments possess frame-building and pore-forming characteristics and early(sea floor) hardening function,thus creating primary matrix porosity reservoir.Special diagenetic environment is featured by poor water-rock interaction,slow mineral stabilization process and excellent preservation of vadose pisolite,aragonite and magnesium-rich calcite under the background of dry-hot/arid paleo-climate,especially beneficial for porosity conservation.Moreover,pore expansion and massive non-texture selective dissolution fissures and caverns are resulted from syngenetic and para-syngenetic dissolution,especially three-phase weathering crust dissolution caused by three-episode Tongwan movement,which fundamentally determines the reservoir formation.Multiphase fissures,especially Late Yanshan-Himalayan tectonic fissures,establish the connection between pores,vugs and dissolution caves to largely enhance reservoir connectivity.

The tempestites are developed in the upper Member of Lower Cambrian Canglangpu Formation and low Member of Longwangmiao Formation and Middle Cambrian Gaotai Formation in Central Sichuan Basin.Storm-generated sedimentary structures mainly include scouring-filling structure,chrysanthemum-like structure,storm tearing structure and hummocky cross stratifications,etc.The storm sedimentary sequences show incomplete development,dominated by A+B+C,A+B,A+C and A+D with a thickness of 5-12 cm.There are five stages of storm-generated sedimentary structures,and tempestites are associated by clastic quartz.The content of clastic quartz is generally higher in storm stage than that in storm ceasing stage.The tempestites present better lateral extension,and storm centers show a migration from Well Block MX202,GS10,MX21 to MX202-NCH1 from bottom to top.Meanwhile,three thickness centers are formed with planar NE-SW distribution,i.e.,Well Block MX202-MX12-MX17,GS10-GS23-GS26 and NCH1.The discovery of Lower-Middle Cambrian tempestites in Central Sichuan Basin indicates that the depositional environment of this study area was storm mixed tidal flat,and storm tidal sand ridges were formed under the effect of NE-trending storm tides,leading to lagoons under sand ridge barrier.Meanwhile,it is also demonstrated that Moxi area was taken as a highland in sedimentary paleo-terrain,presenting a gentle dipping in SW-NE directions,and the north part of Mianyang-Changning intracratonic sag might be closed during the late sedimentary stage of Canglangpu Formation to that of Longwangmiao Formation.

The ultra-deep reservoirs(>4500 m) in the sedimentary basin have different temperature and pressure conditions from shallow and mid-deep reservoirs,and a significant difference also exists in fluid system.The research object is the silicified segment of ultra-deep Middle to Lower Ordovician carbonate reservoirs in Well SN4 along the NE strike-slip faulted belt on northeastern slope of Tazhong uplift,Tarim Basin.Based on deep diagenesis research,systematical analyses were carried out on the fluid inclusion of daigenetic minerals,stable O-C and Si-O isotopes,as well as constant,trace and rare earth elements.The results show that three types of fluid end-members exist in the ultra-deep Middle to Lower Ordovician carbonate reservoirs,i.e.,plutonic upwelling hydrotherm,exogenous syngenetic brine and the mixed fluid of the former two types of fluids and reservoir syngenetic seawater.These three types of fluid end-members evolved from the following two types of fluid-rock interaction system,i.e.,the evolution system of meteoric water-syngenetic seawater gravity flow and that of remote hydrotherm-syngenetic brine mixed upwelling flow driven by igneous activities.The upwelling flow has two fluid sources,i.e.,(1) remote hydrotherm driven by igneous activities,characterized by mid-low temperature,mid-high salinity,rich Si and strong acidity resulting from CO₂ and H₂S hydrolysis reactions,which is the solvent generated in interaction between fractured-vuggy reservoir hydrotherm and rock,and may induce the first phase of natural gas charging;(2) the hot alkaline brine with mid-low temperature,rich in Ca and CH₄,and sourced from the underlying Cambrian source rocks,leading to the formation of late fissure-type bladed calcite and the second phase of natural gas charging for accumulation.Based on diagenetic mineral assemblages and temperature control mineralogy principle,the path model of chemical reaction in reservoirs was created.In combination with the measurements of reservoir physical properties,it was preliminarily estimated that the alternation of such upwelling hydrotherm contributed 8% to reservoir porosity.Therefore,it is indicated that multi-phase igneous activities and fault movements could provide driving force and access for upwelling hydrotherm.Meanwhile,it is an independent factor that plays a very important role in controlling the formation of ultra-deep fractured-vuggy carbonate reservoirs and natural gas accumulation.It is concluded that the central igneous zone in Tarim Basin will become the development zones of hydrothermal fractured-vuggy reservoirs and favorable natural gas accumulation zones.

The traps in the ultra-denudation zones at the northwestern margin of Junggar Basin are characterized by wide distribution,shallow buried depth,long trap-source distance,large differences in trap oil-bearing property and etc.Trap oil-bearing property is mainly controlled by the migrating capability of fault-sand transport system,hydrocarbon migration distance,poor reservoir-cap physical properties and other factors.Among them,the fault-sand transport performance can be expressed by fault open-closure index and sand transport index.The hydrocarbon migration distance can be expressed by trap-source plane distance,and trap reserving performance can be characterized by the difference in reservoir porosity between reservoir and cap rock.Whether the trap contains oil or not depends on whether the fault-sand transport index exceeds critical value.The trap oil-bearing degree has a favorable positive correlation with fault-sand transport index and trap reservoir-cap porosity difference,but shows a negative correlation with trap-source plane distance.Through analyzing the relationship between trap oil-bearing property and single factors,multiple factors are combined to establish the multi-parameter fitting relation of trap oil-bearing property in ultra-denudation zones.The application results show that the predicted value of such fitting relation is highly consistent with the true value,so that this relation can be used for quantitative assessment on the trap oil-bearing property in ultra-denudation zones at the northwestern margin of Junggar Basin.

A study of fluid inclusions found that a special kind of three phase(oil-gas-water) immiscible inclusions developed widely in sandstone reservoirs.This type of inclusions trapped oil and water in an inclusion at the same time.Consequently,these inclusions showed five marked characteristics:(1) gas-oil-water three phase coexistence;(2) abnormal high homogenization temperature;(3) variable liquid-vapor ratios and homogenization temperatures in the same inclusion assemblage;(4) bubble closing to the inner wall of inclusion;(5) extremely low freezing point.There is only a shade of difference in appearance between these inclusions and aqueous inclusions,and their abnormal high homogenization temperatures could easily affect the testing result of homogenization temperatures.So,more attention to the fluorescence features and the phase transition during cooling process of fluid inclusions should be paid.The oil in these inclusions was dominated by asphaltic components and was adsorbed on the inclusion inner wall,which indicated that the formation of these inclusions was closely associated with the selective sorption of polar components in asphaltic by quartz grain surface.

Compared with conventional seismic data processing methods,seismic frequency division technology can more effectively improve the data imaging effect.The analysis on seismic attributes and stratum slices is conducted by taking the data volume after frequency division processing as a carrier,which can not only identify the boundaries of reservoirs more accurately,but also clearly describe the internal reservoir details.The improved Morlet wavelet is taken as mother wavelet function to establish the frequency division processing function.Through frequency division of Ricker wavelet,a dominant frequency window is obtained with comparatively clear waveform characteristics and very strong energy.Through frequency division of actual seismic data,a dominant frequency window can be obtained with optimal imaging effect,and seismic profile has a high resolution after processing,so that the imaging effect has been improved significantly.In addition,the geological body can be identified in the dominant frequency window through frequency division of 2D seismic data,which is unable to be identified using original seismic data.Finally,the seismic data volume after frequency division processing in the dominant frequency window is taken as a carrier to perform new horizon tracing.Further,reservoir prediction is carried out based on the analyses on seismic attributes;compared with the prediction results from the analysis of original seismic attributes,it is found that the predicted sand distribution and boundary of reservoirs through frequency division are more accurate,and the internal details are described more clearly,and have a high consistency with drilling results.This method possesses a broad application prospect in improving the accuracy of reservoir prediction.

To better evaluate the flow ability of shale gas in the matrix rock of reservoirs and accurately predict the yield variation laws of shale-gas horizontal well,based on the Fick's first law and material balance equation,the general gas diffusivity evaluation model was established in consideration of the gas concentration difference induced by pressure difference;the diffusion rate coefficient and diffusion efficiency of shale gas were proposed.On this basis,the corresponding experimental apparatus and flow were designed for shale gas diffusivity evaluation.Meanwhile,the cumulative gas diffusion amount changing over time was obtained through gas diffusion experiments under different conditions.Shale gas diffusion coefficient,diffusion rate coefficient,diffusion efficiency and flow coefficient were obtained using experimental data,so as to analyze the influence factors of shale gas diffusivity.The research results indicate that the gas in shale gas matrix provide important supplies for gas flow in fracturing fissures by means of general diffusion.The magnitude of shale gas diffusivity is determined by shale permeability.The greater the permeability is,the higher the diffusivity will be.The porosity has a small correlation with shale gas diffusivity.

Through analyzing the migration laws of microorganisms in porous media,a 3D three-phase(oil,gas and water) four-component mathematical model was established to reflect the process of MEOR(microbial enhanced oil recovery).The components of the model include microbe,nutrient,dissolved oxygen and metabolite(surfactant).The model is used to analyze the convection,dispersion,growth and decay of microbes,chemotaxis,nutrient consumption,metabolite production,adsorption of all components,microbe desorption and other properties.In the meantime,the MEOR model considers the permeability decline due to adsorption of microorganisms as well as the reductions in oil-viscosity and oil-water interfacial tension due to surfactant.Further,the corresponding simulator was developed according to the mathematical model.The microbial enhanced oil recovery effect was predicted under given parameter conditions,so as to analyze the influences of maximum growth rate,microbial adsorption constant,chemotaxis coefficient and metabolite yield coefficient on MEOR and further reveal the mechanism of MEOR.

Aiming at light source fluctuation noises,zero drift and other problems of H₂S gas concentration sensor in optic-fiber evanescent field,double-light-path absorption detection system was designed to theoretically analyze the relationship between evanescent-field luminous power and gas concentration as well as detection sensitivity.Moreover,the relationship between evanescent-field power and optical-fiber residual diameter in the optic fiber corrosion process was also studied.The sensing probes with different evanescent-field power ratios were used for detection experiments of H₂S gas concentration,so as to explore the influences of small-range temperature variations on gas concentration detection.The experimental results show that when the evanescent-field power ratio of sensing probe is 10%,the sensitivity is up to 4.4 W·L/mol,the detected minimum H₂S gas concentration is 5.1×10^-6,and the temperature of 273~333 K has little influences on H₂S gas concentration detection.Due to low production cost,high sensitivity and high accuracy,the optic-fiber evanescent-field sensor can be applied in measurement of H₂S gas during the hydrocarbon exploration and development process.

Transportation safety of supercritical CO₂ pipeline is a key link for carbon capture and storage technology.When the pressure of supercritical pipeline is excessively high,it is generally released using throttling method,and the throttling-inducing temperature drop can be predicted based on adiabatic assumption.According to adiabatic assumption and the law of energy conservation,the relation between critical throttling ratio and adiabatic index was established by solving the relationship between outlet velocity and sound speed during critical throttling process.The impurities in flue CO₂ made influences on temperature drop in the throttling process.The throttling-inducing temperature drop was calculated based on Bernoulli's equation and isothermal enthalpy difference iterative method.Moreover,the influences of impurities in supercritical carbon dioxide pipeline on the throttling-inducing temperature drop were analyzed according to the binary interaction parameter and mixing rule.Research results show that the presence of SO₂ as an impurity in carbon dioxide is helpful for increasing the post-throttling temperature to reduce the possibility of dry ice blocking,whereas the presence of N₂ as an impurity will further reduce the post-throttling temperature.On the basis of case analysis,the specific operation recommendations are provided for anthropogenic CO₂ throttling.The higher initial temperature can prevent dry ice formation at the outlet of vent pipe in use of multistage throttling.

Stray current will leak due to rail insulation reduction in urban metro system with direct current traction.As a result,adjacent buried pipeline and its sacrificial anode cathodic protection system will be interfered to threat the safety operation of pipeline and cathodic protection system.Numerical simulation technology was used to calculate and solve such interference problems,which was verified using the existing literature data.Meanwhile,actual case calculation was performed to analyze the influence laws of metro stray current on buried pipeline cathodic protection level and sacrificial anode output.Aiming at the obtained influence laws,the corresponding protection methods were proposed,and its effectiveness was also analyzed.The research results can provide references for buried pipeline protection design from metro stray current interference.

Deep coalbed methane(CBM) resources is an important basis for the scale development of the CBM industry in China,but some basic geological problems such as the meaning,definition and the particularities on the "deep" are still not clear.Preliminary investigation shows that the particularity of deep coal reservoir is resulted from higher strata temperature and pressure,which bring about higher compressibility,lower permeability and lower elasticity of deep coals.At the scientific level,the "deep" in CBM fields means not only a depth,more important is a state,which is dependent on threefold formation states the including stress,temperature and(organic) reservoir.At the operational level,the definition of the critical depth between deep and shallow CBM needs to takes into account three geological factors such as the stress state conversion,coal adsorption(gas content) and mechanical properties of coals.Recent research progress provides new insights for solving the basic geological problems.The importance of the free gas to the gas content of deep low-rank coal reservoir is explained,the relationship between the desorption and output stage sensitivity of deep CBM is discussed,the profound impact of variable pore compression coefficient on deep low-rank coal reservoir permeability is analyzed,and the seek-optimizing method of favorable deep-CBM zone based on the accumulation effects is set up.It is suggested that still the geological problems of the four aspects need to solve for deep CBM exploration and development.The first is the deepening evaluation and recognition of deep CBM resource potential,the second is the coupling effect of the basic deep geological characteristics to deep coal reservoir,the third is the geological control of the principles of efficient deep CBM development technology under deep strata stress field,temperature field and chemical field,and the fourth is the geological evaluation of the symbiotic characteristics,co-exploring method and co-mining effectiveness of deep CBM,tight sandstone gas and shale gas in coal measure.

With the enhanced geological knowledge,Yanchang Petroleum Group has clarified that the north Shaanxi slope of Ordos Basin has favorable geological conditions for the formation of unconventional natural gas;tight sandstone gas and shale gas are the most practical exploration and development fields.In terms of geological exploration concept,it has been determined that the provenance of the southern Ordos Basin made a great contribution to the development of Paleozoic sand bodies;frequent transgression and regression is the most favorable factor for promoting the development of high-quality reservoirs.The accumulation mode of "mature hydrocarbon kitchen migration for reservoir control" was created to predict the spatial distribution of tight sandstone gas reservoirs.This study focuses on the gas occurrence capacity of sandy laminae developed in terrestrial shale,aiming to find the occurrence space of free gas.The assemblage of multi-disciplines including geochemistry,reservoir,logging and seismology was used for seismic prediction in the sweet-spot of shale gas reservoirs.Meanwhile,the large-scale exploitation of tight sandstone gas and shale gas is guaranteed by applying horizontal-well drilling and completion technologies for terrestrial shale gas,drilling fluid system with reservoir protection function for tight sandstone gas reservoirs,VES-CO₂ foam fracturing technology,liquid CO₂/slick water mixing fracturing technology and other development technologies.Guided by the integrated exploration and development mode,the geological reserves of Mesozoic shale gas reserves and Paleozoic tight sandstone gas were proven to be 677×10⁸m³ and 3000×10⁸m³ respectively,and current natural gas production capacity has reached 6×10⁸m³/a,basically changing the situation of oil development in the south while natural gas production in the north.

In the 21st century, geodynamics is developing from qualitative analyses to quantitative analyses. Due to its irreversible characteristic, the geological process is difficult to restore, especially for the recovery of geological parameters' evolution in micro scale, now it has become an important scientific problem in geology. Thereby, the concept of "stratigraphic porodynamics" is proposed, which takes microscopic porous media as research subject and mechanic properties of clastic porous media, evolution laws of pore, dynamic causes of pore fluid and its porous flow characteristics in the buried process of sedimentary basins as research contents. It is not only a new discipline which combines diagenetic dynamics and pore fluid dynamics, but also an important component of basin dynamics, which includes progresses of basic theories and applied researches. Furthermore, advancements of basic theories contain six aspects:(1) static balance principle of formation pore,(2) mechanism of sandstone's porosity evolution and quantitative models in the process of burial and diagenesis,(3) characteristics of mudstone compaction and quantitative models of its porosity evolution,(4) theoretical relationship between pore fluid temperature and pressure underground,(5) impacts on pore fluid pressure caused by structural additional stress,and (6) the relationship between the degree of mudstone compaction and thermal evolution of organic matter. Similarly, progresses of applied researches also include six fields:(1) divisions of geotemperature-formation pressure models and explanations of dynamics of oil distribution,(2) improvements on models of formation pressure prediction,(3) determination of critical properties of reservoir and establishment of its dynamic evaluation system,(4) simulation of evolutionary process of fluid pressure,(5) researches on numerical simulation of sandstone oil charging and physical simulation tests,and (6) analyses on dynamic pool-forming process of tight sandstone hydrocarbon reservoirs. All in all, dynamics of stratigraphic porosity integrates the evolution of porosity causes and fluid dynamics as a whole, which is one of the representative disciplines that symbolize geodynamics researches begin to develop in microscale direction in recent 20 years. Most importantly, it is a corollary of quantitative development of researches on mechanism of sedimentary mineral's formation and distribution. In this paper, based on main contents of stratigraphic porodynamics, eight significant research findings are summarized and we expand geological researches from macroscale to microscale, aiming at solving problems of pore parameters' evolution laws in the buried process and updating skills in the application of exploration and exploitation.

Based on the multiple tests and analysis results of more than ten wells in Yacheng, West Qiongdongnan Basin, including drilling and logging data, Laser Raman microprobe, thermodynamic modeling of paleopressures, organic geochemistry, cathodoluminescence, casting thin-section, the carbon-oxygen isotope composition of carbonate cements, etc., this paper analyzes in detail the distribution of the top of overpressure system and characteristic of fluid activity in the nearby discharging zone, and also reveals the diagenetic responses of pressure discharging zone caused by fluid activity. In the present study area, the pressure discharging zone is possibly located in formations around the top of overpressure system. Using the data of formation testing, mud density, well logging and velocity spectrum, it has been confirmed that the top of overpressure system is mainly located within the depth of 3 000-4 000 m beneath the earth and its depth increases from structural high to low position; the influential range of pressure discharging in each well around the top of overpressure zone is different, which can be obtained using vitrinite reflectance (R_o). It is indicated that the current top of overpressure system (in the pressure discharging and fluid draining period) has little difference in depth as compared with the top of paleo-overpressure system. The fluid in the discharging zone is characterized by relatively high temperature and pressure as well as the accumulation of acidic materials and hydrocarbons. The fluid activities cause changes in the temperature, pressure and pore fluid medium of diagenetic field in pressure discharging zone, thus exerting influences on water rock interaction. This phenomenon is specifically described as below:(1) The R_o and clay mineral show a transformation in advance; (2) The organic matter T_max is extremely small and S₁/(S₁+S₂)is extremely large; (3) The development of secondary porosity is resulted from hot fluid acidic dissolution in reservoirs of the discharging zone; (4) The albitization of feldspar particles as well as the abnormal development of authigenic quartz and calcite cement are caused by the discharging of deep overpressure organic fluid. In conclusion, the pressure discharging zone around the top of overpressure system may be favorable for gas accumulation, the formation of high-quality reservoirs and the coupling of cap rocks, which is the target zone for natural gas exploration in Qiongdongnan Basin from now on.

Superimposition of multiple types of eogenetic karsts developing under high-frequency sequence boundary and hypogenic karsts developing along fault belts during burial diagenesis becomes a key factor of deep-ultradeep carbonate reservoir development. Based on an outline of karstification concept, deep-ultradeep Middle-Lower Ordovician strata in Shunnan area in the northern slope of Tazhong uplift, Tarim Basin were studied by means of core observation, thin-section petrological observation, cathodoluminescene imaging, fluid inclusion measurement, stable oxygen and carbon isotope analyses, as well as RMS amplitude computation for 3D seismic data and paleotopography restoration; not only syngenetic karst and interstratal karst types in the upper highstand system tract were microscopically identified, but also a "quasi-layered" development model for such eogenetic karst reservoir was established macroscopically. It is believed that, being seriously filled with subsequent carbonate cement, the eogenetic karst-type reservoir controlled by paleotopography and paleofault had a mean residual porosity of just about 2.0%, whereas the reservoir transformed by hypogenic karst superimposition had a maximum mean porosity up to about 19%. Therefore, reservoirs with eogenetic karsts superimposed by hypogenic karsts will become important targets of exploration in deep-ultradeep Lower Paleozoic ramp zone in the study area.

Large number of fluid inclusions related to hydrocarbon activities are discovered in the oil-bearing dolomites of the Mid-Jurassic Buqu Formation, Southern Qiangtang depression, recording the hydrocarbon migration and accumulation process of oil reservoir belt. In this paper, microscopic fluorescent analysis and homogenization temperature test are conducted based on the petrography of fluid inclusions, to distinguish the crude oil types in oil reservoir belt and explore the hydrocarbon charging process. The obtained results indicate that:1) the oil reservoir belt have characteristics of multi-episode hydrocarbon migration and accumulation, with four types of crude oil inclusions with different maturities and one type of dry-gas inclusion charging. Although the differences exist in the microscopic fluorescent colors of four types of crude oil inclusions in the Long'eni block and Angdaercuo block, the similarities of spectral peak shapes and distinct differences of the main peak wavelengths and red-green entropy parameters between them suggest that these crude oil inclusions may be formed in different maturity stages of the same source rocks. 2) the main accumulation period of the oil reservoir belt is from Late Jurassic to Early Cretaceous and is attributed to hydrocarbon charging in the basin with maximum buried depth. During the Early Cretaceous period, the adjustment of primary oil reservoirs caused by local tectonic activities, resulted in the non-uniform phase of oil inclusions, with, large anomalies in mean homogenization temperature and salinity. During the mid-late Neogene period (the peak period of the second hydrocarbon generation in the basin), part of oil and gas was transferred to dry gas due to the differential subsidence and local thermal anomaly, and finally charged into dolomite particles and calcite cements with migration and capture of fluid.

Mechanical properties of sandstone play an important role in reservoir fracturing design. Based on petrographic observations and rock mechanics tests, a study is conducted on the types of diagenetic facies and mechanical properties of low-permeability reservoir in the upper paleozoic low-permeability sandstone of East Ordos Basin and the petrographic factors which influence rock mechanical properties are also analyzed. In the study area, 6 types of diagenetic facies are detected in the low permeability sandstone reservoir, i.e., matrix filling and strong compaction altered tight facies, quartz-enlarging siliceous cementation-intergranular pore facies, carbonate cementation metasomatism tight facies, calcium dissolution pore facies, matrix dissolution pore facies and clastics dissolution pore facies. For the sandstone with diagenetic facies, a certain difference exists in the compressive strength, mass modulus and poisson ratio. The more the brittle minerals and siliceous cements contained in sandstone and the higher the degree of compaction and recrystalization is, the higher the compressive strength will be, or vice versa. The higher the sandstone porosity is, the lower the elastic modulus will be. The more brittle minerals (e.g., quartz), lower compaction degree and higher porosity will lead to a lower poisson ratio, or vice versa. The sandstone with quartz-enlarging siliceous cementation facies, calcareous cementation-dissolution pore facies and matrix dissolution pore facies has high brittleness coefficient and high fracability, and those with other facies have relatively low fracability.

The axisymmetric drop shape analysis technology was used to study the phase interactions of CO₂-oil system and oil-carbonic water system as well as the interfacial tension (IFT) change laws at high temperature and high pressure. The results indicate that the phase interaction between CO₂ and crude oil at high temperature and high pressure can be divided into two stages. The first stage refers to the CO₂ dissolution resulting in oil swelling, and the second stage refers to the extraction of light components by CO₂ resulting in a shrinkage in oil-phase volume. In case of higher pressure, the phase interaction between CO₂ and crude oil becomes faster. Under the minimum miscible pressure, the shape of oil droplet becomes very unstable, the extraction of light components by CO₂ is enhanced and the interface between CO₂ and crude oil becomes blurred. The temperature and pressure are the main factors that affect the IFT of CO₂ and crude oil. The higher the temperature is, the less stable the gas-liquid interface will be, the higher the dynamic IFT fluctuation will be, and the larger the equilibrium IFT will be. The higher the pressure is, the shorter the equilibrium time of dynamic IFT will be, and the lower the final equilibrium IFT will be. In the oil-carbonic water system, the phase interaction is weak with clear oil-water interface and stable oil droplet shape. When CO₂ is diffused into oil phase from water phase, the volume of oil droplet continues to increase and gradually achieves a stable state, and the extraction of light components by CO₂ resulting in shrinkage in oil droplet volume cannot be observed. When CO₂ is dissolved in water and diffused into oil phase, the IFT is gradually decreased to achieve equilibrium. Under the higher temperature and pressure, the equilibrium time for oil-water IFT will become shorter, and the oil-water IFT is smaller.

To effectively develop natural gas hydrate resources, it is essential to construct a constitutive model for gas hydrate-bearing sediments, reveal the deformation law of sediments, and precisely predict the mechanical properties of the hydrate reservoir. Based on the basic assumption that the micro-unit strength of hydrate-bearing sediments obeys the Drucker-Prager criterion and Weibull distribution law, a new statistic damage constitutive model which can simultaneously describe the strain softening and hardening law was established by combining the statistical damage theory and statistical strength theory. On this basis, the solution of model parameters was explored and the accuracy of the model was also verified. The study demonstrates that the hydrate-bearing sediments being strain softening or strain hardening phenomeon after yielding is controlled by the combined influence of effective confining pressure and hydrate saturation, which is reflect by the conjugacy of F₀ and m in Weibull model. Moreover, model parameters mainly affect the evolution of hydrate-bearing sediments after the damage, and has less impact on the undamaged part.

Solid-liquid two-phase flow is one of the fundamental issues concerning cuttings and sand-carrying oil production in petroleum engineering, and pump rate is one of the main design parameters for solving above engineering problem. Three characteristic flow velocities of solid-liquid flow were proposed, i.e., hydrostatic settling velocity, suspension flow velocity and sand-carrying velocity, and their defining methods were also put forward. Using the experimental apparatuses for comprehensive simulation of solid-liquid flow in wellbore, a sensitivity test was performed on characteristic flow velocities at different conditions of fluid viscosity (1~23 mPa ·s), wellbore inclination angle (45°~90°), quartz sand and ceramsite diameter (0.05~1.5 mm), and pipe inner diameter (40~100 mm). The test results revealed that the quantitative sensitivity relationship between the three characteristic flow velocities and particle size, fluid viscosity, wellbore inclination angle, wellbore diameter and material density in low-viscosity fluid, as well as the relevant changing laws. The empirical relationship among the three characteristic flow velocities had been fitted using experimental data, indicating that suspension velocity tends to be 80.43% of the settling velocity under the same flow conditions, which was inconsistent with the traditional view that hydrostatic settling velocity was taken as the critical sand-carrying velocity. Reasonable flow velocity was 3.75 times of suspension velocity, which can satisfy the requirement of fast sand transportation. Aiming at the problems encountered in the calculation of sand transportation velocity using hydrostatic settling velocity, this study proposed the process and method for reasonable solid-liquid flow design using the three characteristic flow velocities.

Weight loss of cement slurry has a significant impact on the cementing quality, and the variation of structure and properties in cement slurry during liquid-solid transition are closely related to weight loss. Consequently, this paper aimed to investigate the evolution of cement slurry properties during liquid-solid transition by tests using X-ray diffraction (XRD), thermogravimetry (TG) and mechanical analyzer. In combination with Environmental Scanning Electron Microscope (ESEM) and new sampling method, a fixed-point observation was conducted on the micro-morphology of cement slurry in the liquid-solid transition process. The research showed that during liquid-solid transition, the formation rate of Ca(OH)₂ and the hydration rate were remarkably increased; as the hydration of cement slurry progressed, the cement particles were gradually covered by amorphous hydration products, thus forming a support structure among cement particles. For this reason, the cement slurry presents a skeleton-pore structure in the liquid-solid transition process, which can decrease the flowing property of cement particles. As the hydration process continued, the free water content in pore solution was reduced, while hydration products were crystallized and enlarged, which will reduced the porosity of cement slurry and block the effective transmission of water pressure in pores, therefore causing weight loss in the liquid-solid transition process. Meanwhile, the physical bonding between cement particles changed into chemical bonding, thus leading to an increase in compressive strength and a decrease in the Poisson's ratio of cement stone.

In view of the shortcomings of independence assumption for random variables in the reliability analysis of corroded pipeline, an analytical method was put forward for the reliability of corroded pipeline considering the correlation among random variables. The models of corrosion perforation, local burst and rupture as well as their composite failure probability were also established. Based on JC method and orthogonal transformation, the multidimensional normal distribution function was used to propose a computational method for the multi-mode failure probability of corroded pipeline considering correlated random variables. This paper elaborated on the correlation of pipeline reliability analysis. Meanwhile, based on case studies, a study was conducted on how the pipeline failure probability was affected by the correlation between 4 pairs of random variables, including pipe diameter and wall thickness, the depth and length of the defect, the radial rate and axial rate of corrosion, as well as yield strength and tensile strength. The analysis results suggest that the correlation between random variables has no influence on the failure probability of pipeline corrosion perforation. The probability of local burst, rupture and composite failure increases with the increase of correlation coefficient between the defect depth and length as well as that between the radial and axial corrosion rate, and decreases with the increase of correlation coefficient between the pipe diameter and wall thickness. The larger the correlation coefficient between yield strength and tensile strength is, the greater the probability of local burst and rupture will be, while the composite failure probability remains the same. Besides, the impact of variables correlation on the failure probability of corroded pipeline decreases as the corrosion continues. The failure probability of corroded pipeline is most sensitive to the correlation coefficient of radial and axial corrosion rate, and least sensitive to the correlation coefficient between the yield strength and tensile strength.

A convenient calibration method is proposed for installation error of biaxial gravity accelerometer, which is an automatic vertical drilling tool used in directional survey. Based on the transformation principles of space coordinate system, the mathematical model is established for the relation between the biaxial gravity accelerometer and the coordinate system of drilling tool, and the error calibration matrix is constructed as well. Before calibration, the axis of drilling tool is ensured to be invariant, then the floating guide sleeve is rotated, and next the output voltage of accelerometer is measured and used as the multiple linear regression sample after being processed. Afterwards, the calibration matrix is solved using the numerical relations between the elements of the matrix. During calibration, the solved calibration matrix and the component of gravitational acceleration on the sensitive axis of gravity accelerometer are substituted into the mathematical models of two coordinate systems to calculate the component of gravitational acceleration on the three axes of drilling tool coordinate system, thus the deviation angle and tool face angle can be precisely measured. This method does not require any high precision auxiliary measuring instrument or calibration reference platform, and there is also no need to set the drilling tool to a specific state. It is characterized by simple operation and high test accuracy, and is particularly convenient for the last error calibration of the biaxial gravity accelerometer at the drilling site. Experiments indicate that the error of the deviation angle is within 2.5% after calibration.

Tightness of a shale reservoir limits movability and movable amount of oil in it, which is a bottleneck factor restricting exploration and exploitation effects. Movability and movable amount of shale oil are closely related to size, distribution, connectivity and mineral composition of pores, pore throats and crevices in shale, as well as oil-rock interaction. The former is related to probability and mechanism of shale reservoir formation, while the latter is related to occurrence mechanism of oil in shale. Therefore, shale reservoir formation mechanism, occurrence mechanism and movability of oil in shale are three key scientific issues in shale oil research; enrichment of shale oil is related to its organic heterogeneity, while recoverability/fracturability of shale oil is related to its inorganic heterogeneity. These are two key technical issues encountered in screening of "sweet spots" in shale oil. Understanding these three key scientific issues and two key technical issues and establishing a quantitative characterization/evaluation technique provide the key basis for improving shale oil exploration and exploitation efficiency. Based on recent studies as well as foreign and domestic research achievements, current situation and trend of shale oil related studies have been discussed in an attempt to propel theoretical study of shale oil and facilitate substantial advance in exploration and exploitation.

Tight reservoir is characterized by small pore throat size, complex pore structure, strong heterogeneity and large difficulty in characterization. Through systematically summarizing the development situation of current characterization technology of tight reservoir, some notable problems in the characterization of pore structure of tight reservoir were pointed out:(1) the scale study on representativeness of sample should be enhanced while emphasizing on resolution improvement; (2) the study on effective application scope of technology should ben strengthened while pursuing new technologies/methods; (3) The fusion of multi-scale qualitative and quantitative data should be strengthened while emphasizing on the quantitative characterization data combination, thus improving characterization precision. The future development of pore structure characterization technologies of tight reservoir was put forward:(1) to combine static characterization with dynamic evolution through multidisciplinary combination study, and achieve a comprehensive characterization of the pore structure; (2) to strengthen the macro-scale research in close combination with movable fluid evaluation, thus realizing the accurate prediction of scale effective reservoir body; (3) to strengthen the research on field application in close combination with reservoir stimulation measures, thus achieving the evaluation and optimization of engineering sweet spots.

Shale reservoir is generally characterized by large thickness and strong longitudinal heterogeneity of reservoir physical property. The multi-stage fracturing development technology for long horizontal well requires the optimization of landing point and trajectory in horizontal well. This paper put forward the concept of longitudinal integrated shale oil/gas sweet spot considering shale fracability, resources endowment, fluidity and other factors, which is a synthesis of longitudinal geological factors and engineering factors. Then the identification process and method of longitudinal integrated sweet spot was established, thus realizing the recognition process from prospective segment to favorable segment, core segment and sweet spot segment, respectively. Meanwhile, longitudinal integrated sweet spot index was designed, which can quantitatively evaluate the difference and heterogeneity in longitudinal distribution of reservoir physical properties. On this basis, the longitudinal integrated sweet spot coefficients considering effective stress distribution were designed to predict effective hydraulic fracture height, which can accurately quantify the optimal horizontal landing point and effectively guide the target point and trajectory designs of horizontal well. Field application has proved the effectiveness of this method.

Sinian layer is about to become the hydrocarbon exploration potential target in Tarim Basin. Accurate understanding of Sinian distribution and lithofacies paleogeographic characteristics in Tarim Basin is not only a basis of further exploration, but also a key to restore the early tectonic-sedimentary evolution history of Tarim Basin. Based on comprehensive analysis of Sinian field outcrop data in the periphery of Tarim Basin, intra-basin drilling data and seismic data in combination with published research achievements, the Sinian distribution, tectonic setting, depositional system and lithofacies paleogeographic characteristics of Tarim Basin were explored in this study. Research shows that there are three types of Sinian depositional system in Tarim Basin, i.e., clastic depositional system, clastics-carbonate mixed depositional system and carbonate depositional system, vertically presenting the clastic sedimentary-carbonate sedimentary evolution characteristics. These three types of depositional system correspond to three times of Sinian transgressive-regressive cycle. The transgression in the initial period of the Early Sinian (ZSQI) led to the formation of clastic depositional system in the lower member of Lower Sinian. The transgression in the late period of the Early Sinian (ZSQⅡ) resulted in the clastic-carbonate mixed depositional system in the upper member of Lower Sinian. The transgression in the initial period of the Late Sinian (ZSQⅢ) led to the Upper Sinian carbonate depositional system. Due to three transgression processes, three unconformities were formed at the middle and top of Lower Sinian as well as the top of Upper Sinian. With the breakup of the Neoproterozoic supercontinent Rodinia, Tarim Basin entered the continent rifting phase. The Sinian period was the intracratonic depression and passive continental margin evolution stage with the paleo-geographic characteristics of uplift in the south and depression in the north. In the Early Sinian, Bachu-Tazhong-Southeast Tarim Uplift and Tabei residual paleo-land were developed with the littoral-shelf environment in the north and littoral-shelf-bathyal environment in the southwest. In the Late Sinian, the Tabei paleo-land disappeared, where tidal flat environment existed in the north, and passive continental margin neritic environment in the southwest.

There are significant differences among pressure fields of different depressions in a petroliferous basin, and intimate relationship existed between pressure field and hydrocarbon enrichment. Based on the measured pressure data of different depressions in Bohai Bay Basin, distribution of different types of pressure field and the relationships between overpressure and hydrocarbon generation, pressure field and hydrocarbon enrichment were discussed. Research shows that the Paleogene pressure fields of different depressions in the Bohai Bay Basin can be divided into three types:normal pressure type, single overpressure type and double overpressure type. These three types of pressure fields have zoned features in their distributions. Normal pressure filed is mostly distributed in peripheral depressions of the basin, while single overpressure field is widespread in the basin, and double overpressure field is concentrated in the areas around the Bohai Sea. Hydrocarbon generation plays a significant role in overpressure formation, thus overpressure layers generally correspond to the major source rock layers, and the difference of the filling evolution history and the main hydrocarbon generating strata of different depressions may be important factors for the formation of the three types of pressure fields.Overpressure in source rocks is closely related to hydrocarbon enrichment. Horizontally, hydrocarbons are mainly distributed around the overpressure center, and the secondary migration distance of hydrocarbons was affected by the degree of overpressure. Vertically, hydrocarbon distribution was controlled by the type of pressure fields. Hydrocarbon accumulation in the normal pressure type depressions is mainly concentrated in the major hydrocarbon-generating layers and their adjacent layers, and hydrocarbons are enriched in the hydrocarbon-generating layers and upper and lower layers in the single overpressure type depressions, while hydrocarbons mainly accumulate in shallower layers of non-hydrocarbon generation in the double overpressure type depressions. The degree of overpressure in hydrocarbon-generating layers influences hydrocarbon enrichment, and those enormously oil-rich depressions all have stronger overpressure

The residual body of the reformed intact volcanic edifice that was finally formed after emplacement during the depositional stage of Yixian Formation in Mesozoic in the Bohai Sea is defined as a basement reformed volcanic edifice. Based on plenty of drilling, seismic, well logging and thin section data in the study area, this paper discusses the characteristics and oil-gas control effect of the basement reformed volcanic edifice. The results indicate that the basement reformed volcanic edifice is mainly controlled by magmatic property, ancient landform and later reformation, and late fault cut and differential erosion are the main forms of volcanic edifice reformation; volcanic rocks in the study area show strong and weak eruption patterns, belonging to inverted-sequence eruptions, in which explosive facies and intermediate-acidic or acidic effusive facies constitute the excellent reservoir facies belt; weathering, cycles and stage boundaries control the vertical distribution of high-quality lithofacies, and the coupling between each boundary at different levels and residual high-quality lithofacies is the key to oil and gas enrichment. During exploration of these volcanic rocks, a key task is to find the stage boundaries in the volcanic edifice with residual high-quality lithofacies within 150 m from the weathering crust or eruption surface.