About 80% of discovered oil reserves in the world is sourced from marine source rocks (about 20% from lacustrine facies), and the main control factors of oil reservoir are diversified in different oil-bearing basins. As viewed from global basins, the most important and most common accumulation control factor is oil source, i.e., "source control" is the most important. The major global marine basins are studied through exploring the formation conditions of marine source rocks, and it is discovered that the Persian Gulf Basin, the West Siberia Basin, the Mexico Gulf Basin, the North Sea Basin, the Atlantic Ocean Basin, the East Africa coast Basin, Sichuan Basin, Tarim Basin and Paleo-Tethys Ocean and other basins were all gulfs during the formation period of chief source rocks, i.e., the lands existed in three sides, and a majority of gulfs had only one water channel (a minority had 2-3 water channels) connected to the ocean. The gulf is the most favorable estuary for river. After passing the weathering denuded zone, the river dissolves a large number of minerals to bring the elements including phosphorus, iron and potassium to the gulf as the main nutrients for aquatic organisms such as algae (the nutrients brought by oceanic upwelling is unable to reach the gulf). Because of the seawater replacement between gulf and ocean with blocked communication, the high concentration of nutrient is maintained, and thus can guarantee the long-term reproduction of aquatic organisms such as algae. The small winds and waves in gulfs are favorable to the organic matter preservation, so as to form high-quality source rocks. The relationship between the organisms and rivers in modern oceans and lakes, such as the Bohai Sea, East Sea, South China Sea, Taihu Lake and Dianchi Lake, are studied to further confirm that the main nutrients for aquatic organisms growing are derived from the rivers on land.

According to field survey, it is found that a set of stable detachment layer is developed in Wufeng Formation of Sichuan Basin and its periphery, characterized by stable thickness (0.3-1.5 m)and special occurrence horizons, and may be a set of high-permeability carrier bed at the bottom of chief shale gas horizons in WuFeng-Longmaxi Formation. Based on the differences in the control of detachment layer on the enrichment of shale gas, shale gas can be divided in exogenous-supply type and in-situ enrichment type. Therefore, the operability of this classification scheme is preliminarily validated by a great discovery of shale gas in Well HD1 and Well XD2. Meanwhile, it is also confirmed through exploratory drilling that the investment return cycle of Well HD1 is similar to that of the current shale-gas exploratory well, and the hydrocarbon transport ability of "connecting planes" caused by detachment layer is greater than that of "connecting lines" generated by the artificial fracturing of shale-gas horizontal well. The enrichment laws of exogenous-supply shale gas not only well explain various problems in the present shale gas exploration and development processes, but also provide assistance in studying the enrichment laws of shale gas in China and the dynamic hydrocarbon accumulation mechanisms in complicated structural zones. The matched pinnate horizontal well technology is able to break through the industrial technical bottleneck of high cost and severe environmental pollution caused by shale-gas horizontal well fracturing, so as to realize the commercial fracturing-free development of shale gas.

The marine crude oil in Tarim Basin is considered to be mainly originated from two sets of source rocks, i.e., Cambrian-Lower Ordovician and Middle-Upper Ordovician, but which is a dominant contributor has been in dispute for a long term. Based on previous research works, through a comprehensive study based on the comparison of biomarkers, fraction carbon isotopes, n-alkane carbon isotopes and the mass balance simulation of carbon isotope, the marine crude oil in Tabei area is confirmed to be mainly contributed by the Middle-Upper Ordovician source rocks (up to 88%), and different regions make different contributions. However, confirmed by current drillings, the high-abundance Middle-Upper Ordovician source rocks show limited distribution, based on which it is difficult to explain the scale of hydrocarbon resource from the giant marine oil field widely distributed in Tabei area. Based on the geological and geochemical evidences including the kerogen elements changing with burial depth, the variation of hydrocarbon generation potential and the paleo-TOC recovery, it is validated that a large scale of hydrocarbon generation and expulsion have occurred in the deep present-day low-TOC source rocks of the platform area, Tarim Basin. In addition, the effective present-day low-TOC source rocks are comprehensively identified according to the hydrocarbon expulsion threshold, source rock geochemistry and logging features. On this basis, the hydrocarbon-generation potential method is adopted to evaluate the hydrocarbon expulsion quantity in the Middle-Upper Ordovician high-abundance and effective low-abundance source rocks of various accumulation systems in the platform area, Tarim Basin. The hydrocarbon expulsion quantity of Middle-Upper Ordovician low-abundance source rocks in the platform area is 494.4×10 ⁸t, and that from the high-abundance source rocks is 1 353×10 ⁸t. The relative contribution ratios of high-abundance and low-abundance source rocks are 73.2% and 26.8% respectively. Among them, the hydrocarbon expulsion quantity of Middle-Upper Ordovician source rocks in Lunnan-Yingmaili accumulation system, Tabei uplift is 327.7×10 ⁸t, and the relative contribution ratios of high-abundance and low-abundance source rocks are 59.8% and 40.2% respectively, indicating that the low-TOC source rocks make an important contribution to the formation of giant marine oilfield discovered in Tarim Basin.

Using silver nitrate-impregnated silica chromatographic column, the sulfur-bearing non-hydrocarbon fraction can be separated from Ordovician crude oil in Well Shunnan 1, Tarim Basin. Using GC-MS method, a complete series of lower thiadiamondoids compounds are found in the sulfur-bearing non-hydrocarbon fraction, including 38 compounds such as thiaadamantane, thiadiamantane and thiatriamantane. Meanwhile, higher thiatetramantanes and tetramantanethiols can be detected as well. Taking D ₁₆-adamantane as the quantitative internal standard, the contents of lower thiadiamondoids, thiaadamantane, thiadiamantane and thiatriamantane in the crude oil of Well Shunnan 1 are 79.88 μg/g(oil), 21.27 μg/g(oil), 31.49 μg/g(oil)and 27.12 μg/g(oil)respectively. The detection of high-content thiatriamantane as well as higher thiatetramantanes and tetramantanethiols shows that the crude oil has experienced moderate thermochemical sulfate reduction (TSR)effect. The higher tetramantanes and pentamantanes can also be detected from the crude oil in Well Shunnan 1, and the 3-+4-methyldiamantane from crude oil is up to 707 μg/g(oil), which indicates the crude oil has experienced serious cracking. Crude oil cracking and TSR effect is the reason for crude oil possessing the heaviest marine whole-oil carbon isotope (-26.7 ‰). The regional high temperature-high pressure background combined with strike-slip fault development supports the geological conditions for the generation of thermal cracking and TSR effect.

The hydrocarbon charging characteristics and migration direction is of great significance for determining the Ordovician favorable abundance zone in Tazhong Area. Through analyzing the data such as existing hydrocarbon exploration achievements and fault system characteristics, multiple methods of conventional logging, seism and geochemistry are used to carry out the in-depth research on the hydrocarbon charging characteristics and migration direction of the target stratum in the study area. The results show that multistage-charging crude oil and natural gas in Tazhong area were all injected into Ordovician reservoirs through 11 hydrocarbon charging points, and then locally migrated along the NW-SE trend. All the 11 hydrocarbon charging points are located in the fault intersection zone formed by the rip cutting between NW-trending thrust fault and NE-trending strike-slip fault. The distribution of the relative parameters of crude oil and natural gas is controlled by hydrocarbon charging points and NW-SE local migration. Adjacent to the hydrocarbon charging points, the hydrocarbon properties present abnormal distribution with NW-SE anomaly gradually weakening. It is shown that with the increasing of the distance away from hydrocarbon charging point, hydrocarbon charging intensity becomes smaller, crude oil density gradually increases, while Ts/(Ts+Tm)index, adamantine index (MDI), TMNr index and TeMNr index of crude oil gradually decline, as well as natural gas aridity coefficient, gas-oil ratio and hydrocarbon productivity; meanwhile, the methane carbon isotope of natural gas becomes gradually lighter. Finally, the study on Ordovician hydrocarbon charging characteristics and migration direction in Tazhong area shows that the further hydrocarbon exploration of target stratum in the study area should focus more on the west of northern slope belt, especially the updip tectonic position of fault intersection zone.

In recent years, favorable trends of hydrocarbon exploration are shown in Hari sag, Yingen-Ejinaqi Basin. However, the distribution of oil and gas is not clear, which seriously restricts the exploration process in this area. Based on the systematic test and analyses of source rocks, crude oil and oil sand samples, a study is performed on the geochemical characteristics of source rocks and oil-source correlation, so as to ascertain the oil-source characteristics of crude oil and provide a basis for hydrocarbon exploration. The research results show that for source rocks in Lower Cretaceous Yingen Formation (K ₁y for short), TOC, R _o, Pr/Ph and gammacerane index are averaged at 4.69%, 0.62%, 0.34 and 0.36 respectively. The source rocks are characterized by extremely high organic matter abundance, Type I and low maturity, presenting the hydrocarbon origin features dominated by the input of aquatic organisms as well as the sedimentary paleo-environment featured with strong reduction, brackish water and water mass stratification. For source rocks in Lower Cretaceous Suhongtu Formation (K ₁s for short), TOC, R _o, Pr/Ph and gammacerane index are averaged at 1.04%, 0.75%, 0.99 and 0.28 respectively. The source rocks are characterized by favorable organic matter abundance, Type Ⅱ ₁-Ⅱ ₂ and low maturity-maturity, presenting the hydrocarbon origin features dominated by the mixed source of aquatic organisms and higher plants as well as the sedimentary paleo-environment featured with reduction and brackish water. For source rocks in Lower Cretaceous Bayingebi Formation (K ₁b for short), TOC, R _o, Pr/Ph and gammacerane index are averaged at 0.91%, 1.31%, 1.18 and 0.24 respectively. The source rocks are characterized by medium-good organic matter abundance, Type Ⅱ ₂-Ⅲ and maturity-high maturity, presenting the hydrocarbon origin features dominated by the mixed source of aquatic organisms and higher plants as well as the sedimentary paleo-environment of weak reduction-weak oxidation and brackish water. In terms of the carbon isotope of individual n-alkanes or the biomarker compound characteristics, the crude oil in K ₁b is similar to the source rocks in K ₁b while different from the source rocks in K ₁y and K ₁s, proving that the source rocks of K ₁b reservoir are mainly the hydrocarbon source rocks in K ₁b. The crude oil of Well Yanha 2 and Yanha 3 is sourced from the hydrocarbon source rocks of K ₁b at different tectonic positions, and the differences in thermal evolution degree of source rocks result in a big deviation in maturity between two oil samples. The reservoirs in K ₁b show the characteristics of "near-source accumulation and extremely limited lateral migration" in the study area.

Due to the interference of stochastic noise, the effective signal of seismic exploration is usually covered and thus is difficult to be identified; meanwhile, it is difficult to distinguish the stochastic noise and effective signal in the time domain. As a new type of multi-scale and multi-directional time-frequency analysis method, Shearlet transform possesses the optimal sparse representation capacity, localization characteristics and directional sensibility. When the stochastic noise is removed by Shearlet transform, effective signals can be retained to the maximum degree, and the signal-to-noise ratio of seismic data can be effectively improved. Aiming at the deficiency in traditional Shearlet transform threshold de-noising method unable to change with the scale and direction, the adaptive threshold changing with the scale and direction is proposed, able to adapt to the difference in noise levels of different scales and directions. The adaptive threshold algorithm based on Shearlet transform and de-noising method based on wavelet transform can be used to de-noise the theoretical and actual seismic data respectively. It can be known by contrast that the adaptive threshold algorithm based on Shearlet transform has the stronger de-noising capacity, able to reserve the effective signal to the utmost extent.

There are abundant oil-gas resources in Ordovician buried-hill carbonate reservoirs of the northern Jizhong depression. Due to complex lithology (mixed with dolomite and limestone), ultra-high temperature (180℃)and high stress gradient (0.023 MPa/m), various technologies have been used previously, but no breakthrough was achieved. Aiming at the above reservoir geological problem, reservoir evaluation, process optimization, technique design and other research were carried out on basis of reservoir geological characteristics, so as to form the special volume fracturing technology of geo-engineering integration for ultra-high temperature and ultra-deep heterogeneous carbonate reservoir. Firstly, the geological and engineering volume fracturing factor scheme of complex fissure network was validated by the physical test of 1 m ³ huge rocks and numerical simulation means in combination with geological characteristics, and the results show that even if the reservoir is mainly characterized by micro fissures, poor connection and high dual-direction stress deviation (7.0-9.8 MPa), complex fissure network hydraulic fractures can also be achieved by high displacement-high-low viscosity liquid combination, temporary plugging diversion and other techniques. Secondly, the integrated volume fracturing technology was applied for ultra-high temperature and ultra-deep reservoir, i.e., through the safety and mechanical check on tubular column, volume fracturing pressure prediction and impact analysis on measuring-pilot production, the previous multi-processes were changed into the integrated tubular column of exploration production and development production so as to reduce the safety ricks. Thirdly, the technology of multistage injection, temporary plugging diversion and sand-adding acid-fracturing was created for 180℃ ultra-temperature and 5 000 m ultra-deep carbonate reservoirs to achieve the volume fracturing objective of inter-layer temporary plugging and inner-layer diversion. Fourthly, the carboxymethyl fracturing fluid and acidizing fluid systems applicable at 180℃ ultra-high temperature were preferentially used, and the viscosity of fracturing fluid through 120 min shearing at 180℃ and 170 s ^-1 still remains 80 mPa·s. Through 60 min shearing at 180℃ and 170 s ^-1, the viscosity of acidizing fluid reaches 30 mPa·s. The above technology was widely applied in Well Antan 1x with the pumping rate of 11 m ³/min to ensure the 6 h safety and high-efficiency implementation as well as subsequent safety and stable production for a half year and above under all kinds of adverse conditions including large scale (3 000 m ³), high pressure (80-90 MPa), multiple combination with liquids (fracturing fluid and acidizing fluid)and ultra-high temperature (180℃). Proven by micro-seismic monitoring and simulation, the stimulated reservoir volume was increased by 3.5 times than the past technology to realize the length-width-height 3D simulation. After fracturing, daily gas production was 40.9×10 ⁴m ³, daily oil production was 71 m ³, the pressure of pilot production well head kept over 25 MPa, and stable daily gas production reached 10×10 ⁴m ³, which achieved the integrated design objective of exploration, development, geology and engineering.

Residual-oil in-situ gasification is a forward-looking technology aiming at abandoned reservoir. Slow gas-producing rate is the main problem at the present stage, unable to satisfy the demand for developing large-scale oilfields. In this study, microbial electrolytic cell was introduced to supply energy for microbial growth and metabolism, realized the "microorganism-electrochemistry" combination effect and accelerated the material and energy supply in the process of microbial gasification, so as to speed up the microbial methane synthesis rate. Firstly, the "syntrophic metabolism-methane production" microflora with high gas-producing rate was obtained by acclimating from oil reservoir, and the microflora community structure was analyzed by high-throughput sequencing. The results show that Syntrophomonas, Syntrophus, Syntrophothermus and other microbes with syntrophic metabolism characteristics become the dominant bacterial genera. Methanoculleus, Methanobacillus and Methanobacterium can use H ₂+CO ₂ and formate as the substrate to synthesize methane, and then become the dominant archaea genera. Moreover, the gas-producing analysis shows that this microflora methane synthesis rate reaches 5.3×10 ^-3mL/(cm ³·d), then under the same conditions, the microbial electrolytic cell additionally increased by 0.15 V is used to enhance the methane synthesis of such a microflora; the methane synthesis rate is improved to 14.7×10 ^-3mL/(cm ³·d) by 177.4%, and the Faradic efficiency is increased from 64.7% to 123.2%. Finally, the influence factor for the microbial electrolytic cell enhancing methane synthesis rate was studied, and the methane synthesis rate can be impacted by carbon source, mineralization, electrode material and electric potential, of which electric potential can significantly affect the methane synthesis rate. Under the condition of adding 1.5 V electric potential, the methane synthesis rate of such a microflara can reach 33.16×10 ^-3mL/(cm ³·d), increased by 526.4%.

Rate transient analysis (RTA)is a type of theoretical analysis method to quickly evaluate the parameters of shale oil-gas reservoirs including the permeability, hydraulic fracture half-length, SRV volume, recoverable reserves and EUR based on production data. When analyzing the actual data of a certain overseas shale oil-gas field, due to the irregular dynamic data and imperfect theory, a great uncertainty exists in RTA results. This will cause errors in the judgment of well production state, thus misleading the formulation of development strategies. Aiming at the problems of multiple solutions and false solutions easily appearing in the process of RTA, a research was conducted in terms of optimizing interpretation method and perfecting analysis theory in this study, and two methods were proposed, i.e., the constrained solution method including linear flow analysis and analytical model fitting and compound linear flow interpretation method, which can improve the reliability of interpretation results. Moreover, the two methods showed good application effect in analyzing the typical wells of a certain shale oil-gas block, of which the interpretation permeability was basically consistent with test permeability. On this basis, it was found that the hydraulic fracture half-length of some producing wells was less than the designed well spacing, so that well pattern infilling could be locally adjusted according to analysis results.

Aiming at the abnormal increase of produced gas-oil ratio in water flooding oil blocks at the middle and late development stages, the oil-gas-water samples obtained from oilfield were adopted to implement a series of physical simulation tests including high-pressure physical property test on simulated formation liquid and water flooding oil, so as to make clear the effect law of water cut in produced liquid on produced gas-oil ratio. The results show that under the condition of fully mixing, the saturation pressure and solution gas-oil ratio of simulated reservoir oil will decrease along with water injection, and moreover, the decreasing magnitude will enlarge with the increasing mass fraction of water. When the mass fraction of water reaches 60%, the saturation pressure of the simulated reservoir oil will decrease by 5.92%, the solution gas-oil ratio will decrease by 9.78%, and the solution gas-water ratio is 2.065 cm ³/g. Under the stirring-free condition, the solution gas-water ratio is gradually increased over the water-oil contact time. When the injected water and simulated oil keep standing and contacting for about 24 hours, the gas volume dissolved in water will reach stability, showing that the injected water can obtain gas from oil phase and turn into gas-bearing water when the injected water contacts with crude oil during its migration in the formation from injection to production. Under the formation condition, the corrected solution gas-oil ratio of simulated produced liquid rises gradually with the increasing of water cut. During the core flooding test in the condition of outlet pressure higher than saturation pressure, the produced gas-oil ratio rises sharply with the increasing water cut as the water cut is over 95%, proving that the change of water cut has a significant influence on the produced gas-oil ratio when the water cut of produced liquid is already at a relatively high value.

This study focused on the current oil-well completion damage made by oil-based drilling fluids. Based on the high-stability characteristic of Pickering emulsion, and through changing the concentration of surfactant CTAB, the bentonite solid particles with different surface wettability were prepared using the in-situ activation technology, so as to study the phase transition mechanism of CTAB inducing bentonite emulsion. The hydrophilicity, hydrophobicity and surface wettability changes of bentonite particles were characterized by Zeta potential and contact angel changes, and the emulsion phase-transition behavior was featured by changes in the conductivity and micro-morphology of bentonite emulsion system. The experiment results show that the surface wettability changes of bentonite particles can be achieved by changing CTAB concentration, and then twice phase transition behaviors can be induced in bentonite emulsion. Moreover, the research on application performance indicates that this reversible emulsion oil-based drilling fluid system has favorable thermal stability with small filtration, so as to avoid the damage to the oil-well completion caused by traditional oil-based drilling fluids.

The lack of fine fault interpretation, unclear controlling reservoir mechanism and resource potential of Yaha buried-hill belt in Tarim Basin were the bottlenecks restricting exploration breakthrough and capacity construction. Using the new data of three-dimensional inverse time migration processing, reservoir inversion, core observation, thin section analysis and well testing, strata and lithofacies distribution were determined, structural morphology and fault system were characterized, the genetic mechanism and hydrocarbon accumulation of quality reservoirs were studied in Yaha buried-hill belt. The study showed that the early strong thrusting of Yaha fault was an important geological event that had affected the denudation of the fault block, the reservoir development and hydrocarbon enrichment. Different types of dolomite developed in Paleozoic laid the material foundation for the formation of insider reservoirs. Tectonic cracks had a positive influence on the development of karst reservoirs, and high-quality reservoirs spread along fractures. The comparison of hydrocarbon sources showed that hydrocarbon on the north side of the Yaha fault is mainly from the Triassic-Jurassic terrestrial hydrocarbon source rock in Kuche depression, and it moves southwards along the unconformity surface. On the south side, hydrocarbon originated from the source rock in the Lower Paleozoic, migrated vertically along the fault and adjusted laterally on the buried-hill surface. A large complex hydrocarbon reservoir model of fault-block buried-hill was created to reevaluated and broke through the view that reservoirs were controlled by the Upper Cambrian anticline buried-hill, to expand the exploration fields of Sinian and Cambrian fault-block buried-hill, and to clarify the potential of 20 million tons hydrocarbon exploration in Yaha buried-hill structural belt. It played an important guiding role in the hydrocarbon exploration and development of buried-hill.

The upwelling facies is an important sedimentary model of marine organic-rich shale. Based on the outcrop and drilling data of Lower Silurian Longmaxi Formation, Wuxi area, Northeast Sichuan, a fine characterization is made on the Aeronian organic-rich shale. It is preliminarily concluded that the Aeronian shows the sedimentary formation characteristics controlled by upwelling, and four understandings are achieved as follows:(1)The lithological assemblages are diversified, presenting multiple deep lithofacies assemblages of the thick-layer carbonaceous shale with interbedded siliceous shale, carbonaceous shale with a high gamma sandstone layer (GR 185-203 cps), carbonaceous and clayey shales with barite lumps, rhythmic layers composed of clayey shale and high gamma sandstone layer, and thick-massive clayey shale from bottom to top, more complex than Wufeng-Rhuddian Formations. (2)Low S/C ratio and high Mo content indicate that the Wuxi sea area in the Aeronian sedimentary period has continental margin characteristics with low salinity and low enclosure. (3)The rich nutrients such as P, Fe and Ba show that the paleoproductivity of Wuxi sea area was generally high through the Ordovician and Silurian transition and peaked at the Aeronian, significantly higher than contemporaneous basin area. (4)The deposition rate was relatively fast, roughly characterized by being slow in early stage and quick in middle-late stage, reaching 25.24-149.42 m/Ma after the middle Aeronian sedimentary period and controlling the formation of organic-rich shale with the thickness of 18-50 m and TOC of 2%-4%. Therefore, it can be judged that the organic-rich shale in Longmaxi Formation of Yangtze sea basin is dominated by slow deposition of stagnant water shelf facies, and the Aeronian on the northern margin of basin area and above is the upwelling facies sediment.

Industrial gas flows have recently been discovered for the first time in the dolomite reservoirs from Mid-Devonian Guanwushan Formation, Northwest Sichuan Basin, and its natural gas sources have attracted much attention. Based on geochemical analysis, a comprehensive study is conducted on the geochemical characteristics of Devonian natural gas, bitumen, oil sand and source rocks. The results show that the Devonian natural gas is secondary cracking dry gas dominated by hydrocarbon gases, including more than 94% of methane content, trace ethane, propane, and a small amount of non-hydrocarbon gas such as nitrogen and carbon dioxide. The δ¹³C₁ value of nature gas is ranged from -32.3‰ to -31.9‰, δ¹³C₂ values is from -28.6‰ to -28.4‰, and δ²H₁ values is from -141‰ to -138‰, indicating the hybrid gas dominated by sapropelic type. The n-alkanes and alkyl cyclohexane of Devonian downhole bitumen are characterized by two main peaks, and the biomarkers are distributed normally. The bitumen and oil sands in the outcrop section are subjected to strong biodegradation. The comparison in the biomarkers characteristics of saturated hydrocarbon and aromatic hydrocarbons between bitumen, oil sands and source rocks show that the Devonian oil and gas is sourced from the Lower Cambrian Qiongzhusi Formation and Lower Permian source rocks, dominated by Qiongzhusi Formation. The research results have important guiding significance for developing exploration and deployment solutions for natural gas in Northwest Sichuan Basin.

Through the observation and analysis of Well Ming D2, it is proposed that the slumping deepwater gravity flow sediments are widely developed with various sedimentary structures and obvious characteristics in Cretaceous Nantun Formation and Damoguaihe Formation in Dongming sag, Hailaer Basin. Based on sedimentary process, the simplified classification scheme represented by Shanmugam is used to divide the slumping deepwater gravity flow into four processes, i.e., sliding, slumping, debris flow and turbidity current. Meanwhile, this paper describes the sedimentary characteristics in each stage of the process, summarizes the main identification marks, analyzes and discusses the formation mechanism. It is considered that the three stages of sliding, slumping and debris flow of the slumping deepwater gravity flow are dominated by the mass flow transport mechanism, and the sedimentation in the stage of turbidity current is mainly controlled by Newtonian fluid or turbulent flow mechanism. In the sliding stage, the partial reservation of primary sedimentary structure characteristics, such as sand-mud interbed and sedimentary cycle, is mainly identified by the development of small normal fault or reverse fault in internal layers, and large stratigraphic dip. The sediment in the slumping stage is mainly characterized and identified by plastic deformation with the top and bottom abruptly contacted with dark mudstone, as well as the large-scale internally-developed syndepositional soft-sediment deformation structures, such as convolute structure. The debris flow can be classified into sandy and muddy debris flows. The debris flow sediment is mainly marked by the Bingham fluid and overall frozen sediment with the top and bottom of sandstone abruptly contacted with dark mudstone, massive sandstone as well as the favorable conditions for developing floating gravel and mudstone tearing clastics. In addition, the reverse graded bedding can be developed in the sandy debris flow. The turbidity sediment transported by Newtonian fluid is mainly indicated by normal grading bedding, the bottom abruptly contacted with dark mudstone, and the development of complete or incomplete Bouma sequence.

There is certain relationship between volcanic hydrocarbon reservoirs and fractures, while fracture distribution laws are macroscopically characterized by seismic attributes. A quantitative characterization method of volcanic fractures is established on a basis of electrical imaging logging to study the "point", "linear" and "planar" distribution laws of Carboniferous volcanic fractures in Dixi area. This method is applied to perform the fine interpretation of lithology and fractures using electrical imaging logging data, define the calculation method of fracture parameters, and obtain the fracture development level and distribution characteristics. The study shows that the tectonic fractures with median-high angle are dominant in Carboniferous. Meanwhile, basic lava and acidic intrusive rocks have higher fracture development rate and density than volcanic breccia and tuff, and are the main place for the development of fractures. In case of the single-layer thickness less than 15 m, fractures are prone to develop, characterized with "single-section" development mode, large density of fracture layer and high fracture development rate. In case of the single-layer thickness greater than 15 m, fractures are difficult to develop, mainly concentrated at the top and bottom of lithological body, characterized with the "tri-section" or "bi-section" development pattern, overall small density of fracture layer, low fracture development rate and high local rate. In the meantime, the weathering crust can promote the development of fractures in the adjacent lithological body and change the development pattern. Fractures are mainly distributed vertically at the depth of 250 meters under the top of Carboniferous weathering crust; the deep fracture development degree is gradually declined. However, on the horizontal level, the vicinity of faults is the high-value zone of fracture layer density and development rate, distributed in the trend towards fault.

The reserving space type, diagenesis type, and diagenetic mineral assemblages in Member Ma 5₅-Ma 5₁₀ of Majiagou Formation, Ordos Basin are studied based on core observation, conventional logging and image logging data. The results show that the main lithology of Member Ma 5₅-Ma 5₁₀ in Majiagou Formation is dominated by silty and fine crystalline dolomite. The main reserving spaces are dominated by intercrystalline pores, intercrystalline dissolved pores and dissolved pores, occasionally with diagenetic fractures. According to diagenesis, diagenetic minerals and reservoir physical properties, the diagenetic facies are classified into six types, i.e., intercrystalline pore facies, corrosion facies, diagenetic micro-fracture facies, compaction and pressure solution facies, calcite cementation facies and gypsum filling facies. In combination with the response characteristics of diagenetic facies on the conventional logging curves, the imaging logging porosity spectrum analysis is introduced to realize the logging recognition of single-well diagenetic facies, and the analysis results are well consistent with gas production test data. The combination of qualitative analysis on imaging logging porosity spectrum and conventional logging can reveal the development and distribution of pores, and also determine diagenetic facies during logging and provide theoretical guidance and method support for reservoir evaluation and prediction.

Aiming at the complex planar distribution of residual oil at ultra-high water cut stage and different development strategies in various regions, a zoning regulation and control method of reservoir is proposed based on the calculated results of reservoir numerical simulation. Firstly, the water saturation corresponding to ultimate water cut is taken as the criterion to distinguish the flooded area and potential area. Secondly, the residual recoverable reserve abundance limit and flowing velocity limit are established considering economic factors. By using this two limits, the potential area is divided into four types, i.e., low-speed new-well regulation zone, low-speed injection-production regulation zone, high-speed new-well regulation zone and high-speed injection-production regulation zone. Through comprehensively considering the distribution characteristics of each zone, the connected-area labeling algorithm is used to calculate the number of grids in the connected areas of each zone. Then the area of connected areas and the residual recoverable reserve are calculated and the development policy of different connected areas is recommend. The reservoir application results shows that the area of low-speed new-well regulation zone and low-speed injection-production regulation zone is decreased greatly, and the recovery degree is improved by 3.1% after five years of reservoir regulation.

The coalbed methane geological parameters of 20 blocks/mines in China are systematically collected and sorted to analyze the change laws of sorption time and permeability varying with coal-rank. In combination with the gas production curves of CBM wells in different rank blocks, this study reveals the reasons for gas production dynamic diversity in different rank blocks prior and posterior to peak production, in order to provide the basis for controlling primary drainage rate in different rank blocks. The studies show that (1) sorption time has a U-shaped variation with the increasing coal-rank. In the low and medium rank blocks/mines, the sorption time is generally less than 15 d; in high rank blocks/mines, the sorption time greatly varies from 0.1 to 85.54 d. (2) Coal reservoir permeability has not varied systemically with the increasing coal-rank between the blocks/mines, but shows 2-3 orders of difference within a block/mine. (3)Peak production time is correspondingly related to primary drainage rate and sorption time, but not evidently related to permeability. (4) In different rank blocks, the primary drainage rate of a well should be controlled according to the allocation relation between sorption time and permeability of coal seams in the well:in low and medium rank blocks, the sorption time is generally short, for the well/seam with low permeability, the primary drainage rate has to be strictly controlled. In high rank blocks, the sorption time varies from short to long, for the well/seam with long sorption time and high permeability, the primary drainage rate can be speeded up appropriately.

Fractures are crucial for unconventional hydrocarbon exploitation, but it is difficult to accurately observe the 3D spatial distribution characteristics of fractures. Microtomography (micro-CT)technology makes it possible to observe the 3D structures of fractures at micro-scale. In this study, micro-CT scanning is conducted on multiple mud-shale samples of source rocks in the Permian Lucaogou Formation, Junggar Basin. The Avizo software is applied to process and segment the micro-CT images, so as to obtain the 3D fracture structure model inside rock core. Therefore, the independently-developed CTSTA program is adopted to quantitatively describe the micro-fractures inside rock core, including fracture dimension, extension direction and extension scale. Meanwhile, this study summarizes the classification characteristics of fractures and their anisotropy. On this basis, the fractal dimensions of fractures can also be extracted. Previous studies have shown that the geometric features of fractures have self-similarity at a large or small scales, which can be described by exponential laws; and the fractal dimension is a typical exponent. Through the quantitative description or characterization of 3D fractures at micro-scale, the distribution characteristics of fractures on a large scale could be known.

During the drilling process of fractured carbonate formations, the coexistence of well kick and loss caused by the displacement of gas and liquid gravity often leads to downhole complexity, difficulty in well control and reservoir damage. In this study, an indoor experimental device for gas and liquid gravity displacement is created to simulate the coexisting well kick and mud loss, characterized by the adjustable key parameters such as fracture size and drilling fluid performance, automatic data acquisition and analysis, displacement process visualization and so on. The phenomenon of gas-liquid gravity displacement is simulated using this new device, by which an obvious gas-liquid interface can be observed in fractures. By changing the fracture width, fracture opening degree, drilling fluid viscosity, bottom hole pressure and other parameters, this paper analyzes the characteristics of gas-liquid gravity displacement in fractured formation. The results show that the loss rate increases with the fracture width and opening degree rising, more sensitive to fracture width. In the meantime, the increase of drilling fluid viscosity has an obvious suppression effect on gas-liquid gravity displacement. Based on the results of laboratory experiments, the preventive measures for gas-liquid gravity displacement are proposed, which can provide references for safe drilling in carbonate fractured formations.

Constant tool face angle curve is a typical component of well-path in planning, characterized by complex calculation and difficult design solution. The existing models are lack of generality and only have single solving mode, so two typical planning models of well-path with constant tool face angle are proposed to find the flexible and effective solving methods. Aiming at the common design problems of directional wells and horizontal wells, two typical planning models of single and dual constant tool face angle curve(s)combined with line are created to discuss multiple solving methods of design variables. Through rationally setting the initial value of design variable, the quasi-Newton numerical solving method is used to solve the above two types of planning models accurately, rapidly and flexibly. According to calculation examples, these two typical planning models of well-path and their solving methods are correct, reasonable and effective, able to be used for the well-path planning of directional or horizontal well, satisfying various kinds of application requirements.

Bozhong sag is not only the most oil-abundant but also the most gas-abundant sag in Bohai Bay Basin, which lies in the middle of Bohai region with an area of nearly 9 000 km² and a thickness of Cenozoic strata more than 10 km. It is the largest and thickest sag in Bohai Bay Basin. Bozhong sag experienced two stages, i.e., Paleogene fault depression and Neogene regional depression. During the stage of Paleogene fault depression, a bi-extension occurred to form a pattern of "four subsag with one uplift". The fault depression experienced an evolutionary process from several separated subsags into a whole. Continuous sedimentation led to the formation of Paleogene and Neogene-Quaternary "double-thickness" structure during the depression stage. There are three sets of source rock layers in Bozhong sag, i.e., Members 1 and 3 of Shahejie Formation and Member 3 of Dongying Formation (Sha 1, Sha 3 and Dong 3). High-quality source rocks are mainly developed in the middle and upper part of Sha 3, and the lower part of Sha 1 and Dong 3. Since the overlying layers are ultra-thick, there occurred the high evolution of source rocks. Based on statistical research, this study has established the hydrocarbon generation and expulsion models for different layers of source rock in Bozhong sag. As viewed from the predicted results, the source rock in Bozhong sag has large oil and gas discharge of 512.5×10⁸m³ and 311.64×10¹¹m³, respectively. Reservoirs of Kongdian Formation and buried hill in Bozhong sag present good hydrocarbon source conditions and locate in the near-source zone. The regional caprock of deep reservoir is the thick mudstone in Dongying Formation with a high degree of diagenesis and a strong blocking ability. The buried hill formations are characterized by old age, hard lithology, multiple tectonic movements, fissure development, strong corrosion, favorable property and high yield. The glutenite in Kongdian Formation has a strong anti-compaction property. Large groups of deep traps are developed, showing great prospects for exploration. Thus, deep reservoirs in Bozhong sag have the conditions to form large gas field, which are favorable areas for the discovery of large gas fields.

Accumulation physical analog experiment, cast and fluorescent thin sections, field emission scanning electron microscope (FESEM)and environment scanning electron microscope (ESEM)were utilized to study the secondary migration mechanism and accumulation controlling factors of Jurassic tight oil in central Sichuan Basin. It was revealed that under the huge migration driving force, tight oil in the study area migrated with low speed non-Darcy flow through a low efficient migration path, and underwent three migration and seepage phases, including viscous flow, nonlinear flow, and quasi-linear flow. The mode was characterized by microscopic pore-facture complex conduction and macroscopic large-scale short-distance migration. Based on the migration mechanisms, the favorable tight oil play was controlled by the distribution of profitable source rocks. The hydrocarbon generating intensity of 4.0×10⁵t/km² indicated the distribution boundary of favorable tight oil play in the study area. High permeability and porosity reservoir formed tight oil sweet spots, and high-capacity wells were closely related to the development of fracures in a majority.

The Jiuxi depression in the Jiuquan Basin is a typical well-explored petroliferous depression, in which the Qingnan sag is the main petroleum generation sag. With the increase of the number of exploration wells and the depth of exploration in recent 10 years, more and more source rocks in the lower part of the Xiagou Formation and the Chijinpu Formation have been exposed, which provides valuable information for re-understanding the main source rock and its hydrocarbon generation potential in this sag. A detailed geochemical study on a large number of source rocks from more than 30 wells in the Qingnan sag has been carried out and the results indicate that the abundance of organic matter in the Lower Cretaceous source rocks increases from top to bottom, in which the source rocks in the Zhonggou Formation and the Upper Member of the Xiagou Formation are only fair source rock, while the source rocks in the Middle and Lower members of the Xiagou Formation and the Chijinpu Formation are good or very good source rocks with high content of organic matter dominated by Type Ⅱ kerogen. The organic matter abundance of the source rocks is generally the highest in the central region and slightly lower in the south and north, and the high potential source rocks are mainly distributed in the central-northeastern parts where the Middle and Lower members of the Xiagou Formation and the Chijinpu Formation are all main source rocks, while only the Lower Member of the Xiagou Formation and the Chijinpu Formation are good and main source rocks in the southern part. The Middle and the Lower members of the Xiagou Formation are at the stages of thermally mature and peak oil respectively, and the Chijinpu Formation is at the stage of late oil window to highly mature condensate. These source rocks are the main source rocks in the Qingnan sag, and have generated and expelled a large amount of crude oil. There is still good oil exploration potential in the central and northern parts of the Qingnan sag. These understandings have an important guiding role for the fine exploration of oil and gas in the Jiuxi depression. The example of the Jiuxi depression has an important enlightenment to the fine exploration and research of other well-explorated basins in China.

Ordovician carbonate buried hill is an important hydrocarbon exploration target in Qikou sag where the strong heterogeneity of reservoir leads to the exploration in slow progress. Based on the systematic analysis of macro-structural background, drilling and logging, conventional logging, imaging logging, oil testing, seismic and other geological data, the characteristics and main controlling factors of Ordovician buried-hill reservoirs in Beidagang structural belt are identified to propose a multi-stage karst development model. The lithology of buried-hill reservoir in Beidagang structural belt is dominated by dolomite and gypsum-karst breccia. The reserving spaces mainly include karst caves, intergranular dissolution pores, intergranular pores and fractures. The reservoir development is primarily controlled by lithologic assemblage and the comprehensive reformation of Late Caledonian-Early Hercynian, Indosinian-Yanshanian and Himalayan stages. On the basis of the restored karst paleogeomorphology, oil test performance, filling materials of karst caves and tectonic settings, the models for three stages of paleo-karst transformation are established, i.e., the Late Caledonian-Early Hercynian peneplain karst residual hill-slope-sag transformation model, and the Indosinian-Yanshanian secondary residual hill-sag model under the whole background of karst slope, and the Himalaya fault karst transformation model. Among them, the Late Caledonian-Early Hercynian period is the most important stage of reservoir reformation in Beidagang structural belt. The Indosinian-Yanshanian paleo-karst reservoir transformation only had obvious effects in the Qianmiqiao buried-hill zone, while the Himalayan paleo-karst transformation only occurred in the boundary fault zone of the Paleogene sag, leading to the transformation of the Late Caledonian-Early Hercynian paleo-karst reservoirs.

An analysis on nanoporous structure of organic-rich shale is the basis for evaluating the reserving properties of shale reservoirs and the exploration and development potential of shale gas resources. In this study, the nano-CT and 3D reconstruction technique is used to evaluate the shale pore characteristics and connectivity of the Lower Silurian Longmaxi Formation in the Jiaoshiba area of Sichuan Basin. The experimental results show that:(1)nano-CT can display the three-dimensional spatial structure of shale pores, and will be more conducive to characterize the shale pore characteristics in combination with other experimental methods; (2)based on nano-CT, four components including matrix minerals, organic matter, pores, and high-density minerals (such as pyrite)can be distinguished in shale samples with the volume ratio of 89.20%, 6.22%, 2.71% and 1.87% respectively; (3)the pore sizes evaluated by nano-CT range from 79 nm to 4.7 μm, dominated by 100~500 nm, mainly including organic pores and inorganic pores; (4)strong heterogeneity exists in shale pore, generally with better connectivity, dominated by grade Ⅲ connectivity domains.

Through apatite fission track dating and thermal history simulation of five samples in the northern section of Liaoxi uplift, Liaodong Bay depression, the Cenozoic evolution process of the northern section in Liaoxi uplift was analyzed based on regional geological settings and drilling data. The northern section of Liaoxi uplift presented massive uplift and denudation in Cenozoic, characterized by blocky and phased uplift and denudation. The western block experienced two denudation phases, i.e., 65.0~45.8 Ma and 25.3~18.6 Ma, with the annual denudation thickness of 1737 m and 1020 m; the eastern block experienced two denudation phases of 65.0~36.7 Ma and 25.1~19.6 Ma, with the annual denudation thickness of 1 765 m and 711 m. The Cenozoic tectonic evolution in the northern section of Liaoxi uplift was divided into six stages, and significant differential uplift and decline occurred in the eastern and western blocks. The differences in spatiotemporal evolution of the Cenozoic tectonics were mainly controlled by the vertical activity age and intensity of No.2 and No.3 faults in Liaoxi. Jinzhou 25-1 oilfield in the western block of the northern section in Liaoxi uplift experienced two phases of hydrocarbon accumulation, and the early and late reservoir accumulation phase was 25.4~24.2 Ma and 10.7~4.5 Ma, respectively.

The biological gas recovery technology has been applied successfully in the Powder River Basin of U.S., so that the depleted low-rank-coal gas field can re-achieve high yield, thus proving that biological gas recovery is one of effective approaches for the high efficiency development of coalbed methane (CBM). In order to effectively develop the low-rank CBM in China, a simulation experiment was conducted to test the flora types and make clear the gas production means and biological gas recovery potential in the coal seams of Jiergalangtu depression, Erlian Basin. The results indicate that a massive amount of methanogen exists in the coal samples and coalbed water of Jiergalangtu Depression, and acetic acid dissociation and CO₂ reduction both lead to the production of CBM. All coal samples have methane production potential capacity under the in-situ condition, and the Ⅳ coal seam group produced 11±1.4 μmol/g of methane (equivalent to 0.25-0 28 m³/t) of coal sample in five months. In the experiment with exogenous bacteria, the Ⅲ coal seam group produced 18.40 μmol/g of methane (equivalent to 0.41 m³/t) of coal sample. The studies reveal that the Jiergalangtu depression of Erlian Basin can provide the conditions for biological gas recovery, especially for the Ⅲ coal seam group with low gas content. For the Ⅳ coal seam, after gas is depleted using conventional methods, biological gas recovery technology is used as an effective means to improve the single-well production and recovery. At present, six favorable depressions with the geological conditions of coalbed methane similar to Erlian Basin are selected in this study, and the total amount of resources is 4 180×10¹²m³.

Yan'an tight sandstone gas field is characterized by multiple vertical primary development layers, large inter-layer span, wide-scale distribution of effective sand body, high reservoir heterogeneity and significant regional difference. Thus, it is necessary to adopt the efficient mobilization technology using combined stereoscopic well pattern for exploration, which is applicable to different layers and regions. In this paper, the design idea of stereoscopic well pattern with hierarchical constraint is proposed based on four-level constrains, i.e., surface environmental constraint, macroscopic constraint, local constraint and attributive constraint. As a result, the optimization design system of stereoscopic well pattern is established from macro to local, space to property and surface to subsurface through multi-dimension, multi-scale and multi-factor coupling. Then, under the guidance of this design idea in combination with the geological properties of Yan'an gasfield, four development regions are divided, i.e., the multi-layer river-channel enrichment region, the dual-layer non-river-channel low enrichment region, the tri-layer non-river-channel low enrichment region and multi-layer river-channel low enrichment region. Meanwhile, four sets of hybrid well patterns are given, including vertical/directional well with large well spacing, and vertical/directional well+horizontal well with large well spacing. In addition, the optimization standard of well spacing density is proposed for tight sandstone gas field in the enrichment reservoir with recovery efficiency as the main constraint function and the low enrichment reservoir with single well gas yield as the main constraint function. Accordingly, the optimized well spacing density in Yan'an gasfield is 1 000 m×800 m for enrichment reservoir, and 1 200 m×1 000 m for low enrichment reservoir.

High-frequency magnetic coupling wired drill pipe can increase the transmission rate of MWD (measurement-while-drilling)data, able to use coaxial cable for reducing high-frequency loss and realize wireless signal transmission between drill rods based on magnetic coupling effect. To determine the signal-carrier frequency, achieve the matching impedance between different wired drilling tools and reduce channel attenuation, two different models are utilized to complete the channel modeling and simulation analysis. Firstly, the cascade model of standard two-port network elements is used for simulation. Although the "black box" network element based on measurement data is unable to give physical explanation, and also cannot provide optimized design parameters, the simulation results are beneficial to the verification experiment of wired drill pipe process. Secondly, the hybrid model combining lumped-parameter circuit and transmission line is applied for simulation; the lumped-parameter circuit has measurable design parameters, able to provide physical explanation and optimize the system, and the transmission line simulates the coaxial cable with the length unable to be ignored under high-frequency conditions. In the hybrid model, the scattering parameter is calculated by the link parameters of cascade network, so as to set three tuning parameters (coupling coefficient, winding inductance and hysteresis loss). The simulation results are exactly consistent with those measured data.