In view of mud logging enterprises' production and operation still using the traditional management modes such as paper documents and Excel tables,there are problems such as file preservation difficulties,limited functions,and inconvenience in cross-specialty statistics,the research on the establishment and application of an integrated management system for production and operation is carried out.In the process of building an integrated management system for production and operation,after in-depth analysis of the management and operation requirements of various departments of the companies,the hierarchical & micro-service architecture and frontier techniques were used to realize efficient data integration,processes optimization and intelligent decision-making. The application of this system can significantly improve management efficiency,reduce costs,and effectively promote digital management innovation in mud logging enterprises.

With the organizational restructuring of China Petroleum and vigorous widespread of teams of private petroleum enterprises,mud logging operations are currently undertaken by personnel without a geology（logging） background or young engineers,who lack of work experience and complete professional knowledge,and this leads to an increase in misoperations,false alarms and omissions,which results in growing risks to drilling well-control and brings a threat to production safety that cannot be ignored. An intelligent mud logging platform is proposed focused on MapReduce technology,which includes a series of core functional modules such as automatic generation of mud logging assignment, real-time warning of geological anomalies and comprehensive geological assessment. The construction of these functional modules has greatly improved the intelligent level of logging operations. After being applied in 98 mud logging teams and over 700 wells in the Chuanyu and Changqing regions,the digital mud logging operation model has effectively reduced misjudgments and oversights and provided strong technological support and safety assurance for improving drilling speed, efficiency and quality.

Carbon isotope logging technology is widely used in oil exploration realm,especially in unconventional oil and gas exploration. To meet the large-scale exploration and development needs of shale oil and gas,DQL-T carbon isotope logging while drilling apparatus has been developed. It is based on chromatography coupled with mid-infrared quantum cascade laser and uses laser absorption spectrum technology,which is a gas detection technology with high detection performance,strong antijamming ability,and low usage cost. The isotopic values of carbon compounds can be detected quickly by the absorption characteristic peaks of the molecular bond of ¹²C-O or ¹³C-O on laser spectrum. The C₁-C₃ components of drilling fluid gas or cuttings headspace gas are separated and enter the oxidation pond,and the CO₂ generated by oxidation enters the mid-infrared laser spectrum measurement module for carbon isotope measurement. Through the research of "compact-linear" laser measurement module,superminiature volume gas absorption cavity and other techniques,the purpose of overall equipment miniaturization is achieved. The multistage temperature control technique is used to make the spectral core temperature fluctuation in the drilling environment less than 0.02 ℃,and the change characteristics of carbon isotope of drilling fluid gas and cuttings headspace gas can be measured in real time at the well site. The carbon isotope logging analysis of well X in an oil field shows that DQL-T carbon isotope logging while drilling apparatus can quickly measure carbon isotope and is suitable for the harsh environment in the field. Analysis suggests that the reservoirs with high δ¹³C_1-7 fractionation and moderate outgassing amount of the headspace gas have the high enrichment degree of the hydrocarbon accumulation,large occurrence pressure and relatively good physical properties,which can be used as the key reconstruction intervals.

In the oil & gas exploration and development field,the detection of helium in the strata mainly relies on gas logging technology. However,during the process of drilling fluid returning to the ground through the annulus,gases such as helium that are not easily soluble in drilling fluid,will rise to the ground along with the drilling fluid and escape directly into the atmosphere through the liquid surface as the temperature,pressure and other environmental conditions change. At the same time,the existing electric degassing device is installed far away from the drilling fluid outlet,which cannot collect the helium escaping from the drilling fluid outlet pipe,thus affecting the reliability of helium detection. To this end,an anti-escape helium collecting device is designed and developed,which consists of a gas collecting chamber,floating buoys,a fixing device,an anti-escape gas replenishment pipe,a gas collecting pipe,a handle,etc. It is fixed at the outlet position of the drilling fluid line in the drilling fluid ditch. Its anti-escape gas replenishment pipe is directly connected with the drilling fluid outlet pipe,which can replenish the helium escaping from the drilling fluid to the gas collecting chamber,thereby being convenient to collect the gas in the drilling fluid in time,reduce the helium escaping,and effectively improve the reliability of helium detection.The device has the advantages of simple structure,low processing cost and convenient use. It is suitable for collecting helium in the outlet drilling fluid at the petroleum exploration sites,convenient for timely acquisition of helium content in drilling fluid,and improves the reliability and effectiveness of helium gas reservoir exploration.

Accurate prediction of the productivity of shale gas wells is of crucial importance for the efficient development of shale gas. However,complex geological and engineering factors make production prediction a difficult problem in gas field development. This paper aims to establish harmonic decline and hyperbolic decline models to predict shale gas well early production by deeply studying the adsorption characteristics and seepage mechanism of shale gas,systematically monitoring the methane carbon isotope characteristics of natural gas samples from shale gas production wells,and combining the production historical data and production decline characteristics. Monitoring data shows that the methane carbon isotope of the production gas in shale gas wells continuously becomes lighter in the early stage,and becomes heavier after the implementation of stimulation measures. Moreover, after the daily production and the methane carbon isotope value reach their maximum simultaneously, the methane carbon isotope value begins to become lighter again, which may be the result of intensified separation due to diffusion effects after the production of adsorbed gas. Research shows that there is a good corresponding relationship between the change of methane carbon isotope in production gas and the change of gas production rate. Combined with production reality,the productivity prediction models of hyperbolic decline in the early stage and exponential decline in the later stage are adopted to make the predicted results more accurate. Through accurate dynamic monitoring of productivity and reserve estimate, shale gas development can be effectively guided.

In view of the strong heterogeneity of the low-permeability reservoirs in the sha 2 Member of Bohai X Oilfield,the large productivity differences among different wells,and the large deviations between the actual productivity and the pre-drilling prediction of some wells during exploration and development,this paper uses grey correlation analysis to determine sensitive factors affecting productivity and creates a productivity evaluation model based on logging data from 18 wells in X Oilfield. On this basis,combined with Pearson correlation coefficient theory,the C_DP,evaluation chart and evaluation criteria are determined,and finally a method for quickly and accurately evaluating the initial productivity of a single well while drilling in the low permeability reservoirs of the sha 2 Member of X Oilfield is formed. Gas total volume,deep resistivity,porosity,permeability,oil saturation,shale content,and effective thickness are chosen as sensitive factors for the productivity of the low-permeability reservoirs in the sha 2 Member. Based on these seven sensitive factors,the C_DP, evaluation chart and criteria are established. When the C_DP is greater than 0.28,the initial productivity of a single well is greater than 40 m³/d; when the C_DP is less than 0.28,the initial productivity of a single well is less than 40 m³/d. The C_DP,charts and criteria have been applied to 7 wells in X Oilfield with good results. They can accurately evaluate the initial productivity of a single well,thereby providing new reference for decision making on completion program,and also providing new means for rapid productivity evaluation of complex low-porosity and low-permeability reservoirs.

In order to improve the accuracy and efficiency of using well-log information to identify the lithology of tight sandstone reservoirs,based on literature researches,a Lasso-SSA-Adaboost combined model is proposed to identify the lithology of tight sandstone reservoirs. First,the Least Absolute Shrinkage and Selection Operator（Lasso） model is used to order the importance of the original data set's eigenvalues and reduce feature dimensionality. Then,the eigenvalues with higher accuracy for lithology identification and classification are fed into the Adaptive Boosting（Adaboost） model for training and learning. Due to the frequent use of hyperparameters in the modeling process of Adaboost,the Sparrow Search Algorithm（SSA） is adopted to perform hyperparameter optimization to obtain the optimal combination of parameters. Based on the log and core data of the Yan 8 tight sandstone reservoirs in the J study area,a Lasso-SSA-Adaboost combined model was trained and constructed, and compared the effects of identifying lithology with K-nearest neighbor（KNN） algorithm and random forest model. After feature extraction using the Lasso model,the iteration error rate of the Adaboost model is significantly reduced compared to not using the Lasso algorithm,and the accuracy of lithology identification is significantly improved. The global optimization search of SSA algorithm obtains the optimal hyperparameters of Adaboost through fewer iterations,which improves the training accuracy and efficiency of the model. The prediction accuracy of Lasso-SSA-Adaboost combined model is over 90% on the test set,showing its good effects in the study area.

Under the complex sedimentary dynamic conditions of the Paleogene,the Huizhou 26-6 structure formed a complex large-scale glutenite deposit body,which was continuously accompanied by strong volcanism and associated materials,resulting in very complex lithology of the buried hill interface. At present,there are few systematic studies on the complex lithology of buried hill reservoirs,and the stuck and early warning of buried hill interfaces are also thorny issues. In order to accurately distinguish the complex lithology of buried hill reservoirs, as well as stuck buried hill interfaces to reduce engineering accidents,element logging data are used to study the complex lithology of buried hills, mainly igneous rocks,including diorite,granite,limestone and the mountain entry mode. Research shows that the main elements in Huizhou 26-6 structure include seven elements： Si,Al,Fe,Mg,K,Na,and Ca. For the main lithology of igneous in the buried hills,the four maps Si-Fe,Si-Mg,Si-Ca,Si-K have good distinguishing effects. There are two types of mountain entry modes in Huizhou 26-6 structure: one is to enter the diorite fracture development zone first and then enter the granite basement; the other is to enter the granite basement directly. The first type is when entering the diorite fracture development zone,its element characteristics are that the content of Si,K and Na elements decreases,and the content of Fe,Mg and Ca elements increases. There are subtypes in this mountain entry mode. There is a small granite intrusion developed in the weathering crust at the top of the diorite fracture development zone,which is consistent with the characteristic elements of the basement granite,but the Si and Al elements in the weathering crust are slightly higher. When entering the granite basement,the contents of Si,K,and Na elements increase,and the contents of Fe,Mg,and Ca elements decrease. The elemental characteristics of the second type are as follows： the content of Si,K,and Na elements increases,and the content of Fe,Mg,and Ca elements decreases.

Bao 8 wellblock is located in Baode block of the northern segment of the Jinxi flexure fold belt on the eastern margin of Ordos Basin, which is a shallow coalbed methane exploration and development area. Due to the shallow burial depth, large stratigraphic dip, and complex structural changes of the target beds, as well as limited well site space and dense well locations, the drilling construction in the wellblock faces the difficulties such as drilling anticollision, high horizontal displacement to vertical depth ratio, large drag and torque and wellbore cleaning. Therefore, the Landmark drilling engineering design system is used for in-depth analysis. By calculating the relationship between the build-up rate under the conditions of specific target-entering well inclination angle, burial depth of target point and pre-target displacement and deviation angle of angle holding section, the optimized design of wellbore trajectory is carried out based on the concept of "advance deflecting, stable inclination angle finding layer and interwell anticollision". The six-stage 3D wellbore trajectory design is used to improve the trajectory stability, and the friction drag and dog-leg severity are reduced by adjusting the position of deflecting point. Adopt the floating casing running technology to solve the problem of casing running and avoid the casing helical buckling. The pipe string assembly of "ϕ80.9 mm heavy weight drill pipe+ϕ73 mm tubing+ϕ60.33 mm tubing" is designed to ensure the smoothly running in fracturing pipe string, reduce sucker rod wear, prolong its service life and improve drainage depression efficiency. The method was successfully applied to Bao 8 wellblock, and the drilling of 35 directional wells and 20 horizontal wells was completed. For the horizontal wells, the average horizontal displacement to vertical depth ratio is 3.15, the maximum horizontal displacement to vertical depth ratio is 5.32, there are no trajectory collision accidents, the drilling rate of the reservoirs is 98.2%, and the quality of the wellbore and cementing is up to 100% excellent standard. The optimized wellbore trajectory shows good adaptability in drilling and completion, fracturing pipe string running in, and drainage and production sucker rod eccentric wear, providing solid technical support for the construction of China's first 100 million cubic meters coalbed methane large platform. This successful experience has significant demonstration effects and reference value for other shallow coalbed methane exploration and development in China.

Accurately determine the types and characterestics of reservoir rocks and provide an important basis for natural gas exploration and development,this paper,this study investigate a lithological identification method for natural gas reservoirs based on the RBF neural network model using logging data. In order to deal with such factors as equipment performance differences and human operation errors,this paper studies the lithology identification method of natural gas reservoirs based on logging data. After real-time correction and preprocessing of logging data from the three aspects of data parameter conversion,pressure balance,and drilling fluid flow rate,empirical mode decomposition method is used to decompose the corrected logging data,and obtain low-frequency and high-frequency logging data components,and calculate the state characteristic spectral entropy of different components of logging data. Then,the state characteristic spectral entropy is input into the RBF neural network model. After model transmission,mapping,and classification,the lithology identification results of natural gas reservoirs is output. The experimental results show that this method can effectively correct and preprocess logging data,and meanwhile decompose its high-frequency components from logging data,and accurately identify the lithology of natural gas reservoirs. The application effect is significant.

Rapid and accurate prediction of crude oil density can directly support reserve calculation,operation plan formulation guidance,and exploration decision-making during the drilling process. Differences in reservoir bury depth,thermal evolution of hydrocarbon sources,and migration preservation conditions in the Zhu I Depression in the Pearl River Mouth Basin lead to large differences in crude oil density. Therefore,quantitative prediction of crude oil density cannot be achieved on the operation site,which brings a series of challenges to exploration operation and production plan decision-making. Based on the 3D quantitative fluorescence spectrum and laboratory crude oil density,combined with the regional oil qualitative classification standards,this paper uses the spectrum segmentation method to determine the proportion of different oil components. Then,correlation analysis is carried out with the crude oil density in the laboratory,and a quantitative calculation model of crude oil density based on 3D quantitative fluorescence logging data is constructed,which finally realizes real-time and quantitative prediction of crude oil density during the drilling process. Quantitative prediction of crude oil density is carried out in 9 wells in different target areas of the Zhu I Depression and finds that the relative error rate of crude oil density between the prediction and the measured results dose not exceed 2%,confirming that this method has good application prospects.

Most of reservoir prediction results have been based on lithology and logging data,but the rich information included in logging gas data has not been applied to reservoir prediction work. Geophysical profession considers that reservoirs enriched with oil and gas will form biphasic media with characteristics of low-frequency energy enhancement and high-frequency energy attenuation,commonly known as "low-frequency resonance and high-frequency attenuation". The logging data can intuitively reflect the oil and gas properties of the reservoir. Therefore, a reservoir prediction method based on seismic-gas logging parameters fusion has been explored by organically combining the advantages of seismic data and full hydrocarbon curves.The practice has proved this method can be applied to well site deployment,and can also be used in tracking while drilling, which provides a basis for timely trajectory adjustment guiding,thereby improving drilling efficiency.

The reservoirs of Sulige Gas Field are low-permeability and tight,with complex pore structure and significant differences in physical and gas-bearing properties,and it is difficult to accurately classify reservoir types,which is not conducive to the effective implementation of subsequent reservoir stimulation. To study the impact of reservoir types on reservoir stimulation,nine geological parameters that affect gas-well deliverability were selected： effective thickness,porosity,permeability,reservoir quality factor,permeability coefficient of variation,gas-bearing saturation,maximum total hydrocarbon of gas logging,natural gamma,and hydrodynamic index. Using the K-means clustering analysis algorithm,the effective reservoirs were classified into three types. A normalization method was used to define the reservoir classification coefficients,forming a quantitative evaluation method of reservoir types suitable for this gas field. Taking a single set of sand bodies as the study object,the quantitative analysis was conducted from four aspects： the ratio of effective thickness to sand body total thickness,type,effective thickness,and planar distribution scale of gas zones. Fifteen reservoir combination categories were classified and corresponding fracturing reconstruction scales were proposed to form differential fracturing reconstruction schemes,providing quantitative basis for reservoir stimulation. By calculating to determine the reservoir types of gas zones from 149 drilled wells in three blocks in the middle part of the gas field in 2023,the average coincidence rate is 93.0% compared with the fracturing gas testing results. The reservoir classification coefficient of the gas zone has a good exponential relationship with the open flow potential,which can be used to predict the gas zone productivity.

NMR plays a vital role in identifying the properties of formation fluids. However,the existing one-dimensional NMR has certain limitations. Different fluids and their occurrence modes are all presented in the same T₂ spectrum,and the judgment of their occurrence modes is greatly affected by human factors,which affects the accuracy of fluid property identification by mud logging technology. In contrast,two-dimensional NMR technology can provide parameters such as T₁ and T₂,which can effectively solve the problem of identification difficulty caused by overlapping information of different fluids in one-dimensional NMR analysis method. A method of identifying fluid properties with remaining oil index was created by conducting experiments on the modes of occurrence and distribution intervals of fluids under the conditions of original samples,water saturated samples and manganese saturated samples using two-dimensional NMR technology. In the Junggar Basin,the method was applied to identify the fluid properties of 9 oil testing formations in 9 wells,and the fluid properties of 8 formations were accurately identified,with an accuracy rate of 88.9%,which improved the effectiveness of two-dimensional NMR technology in fluid property identification.

Mud logging data contains rich geologic information of hydrocarbon reservoirs,including reservoir characteristics,oil-bearing abundance,fluid properties,productivity status,etc. However,the accuracy and reliability of traditional mud logging interpretation and evaluation methods are greatly affected by human factors,making them difficult to meet the needs of quantitative and accurate evaluation. Based on the statistical multiple linear regression model and entropy method,a comprehensive analytic research was conducted on gas logging,element logging,rock-mineral logging and geochemical logging data. The reservoir physical property index（M_i） and oil-bearing abundance comprehensive evaluation score（F_i）were established,and a quantitative evaluation chart and criteria were constructed to achieve quantitative interpretation and evaluation of mud logging data. In the interpretation and evaluation of five wells in Zhage structure of Hetao Basin,the coincidence rate of interpretation while drilling is increased from 80.00% to 92.50%,which effectively reduces the human errors in the process of mud logging interpretation and evaluation,and provides a strong technical support for regional reservoir exploration and development.

With the continuous expansion of natural gas exploration into deeper strata in Ordos Basin,many Ordovician wells in the western margin of the basin have obtained industrial gas flow through oil testing in Wulalike Formation,and the exploration potential has been further confirmed. However,with the advancement of exploration,the challenges of identifying sweet spot reservoirs and assessing fluid properties have become increasingly prominent. Therefore,on the basis of previous studies,the key mud logging parameters of 61 wells in Wulalike Formation reservoirs in the western margin of Ordos Basin were comprehensively analyzed,the response characteristics of these parameters in shale gas reservoirs were summarized,and the corresponding sweet spot reservoir evaluation methods and interpretation criteria were established. Through the practical application in 25 layers from 9 wells in Wulalike Formation,the interpretation coincidence rate has reached 85.0%,6% higher than before,effectively improving the exploration and development efficiency and success rate of shale gas resources in the region,and providing technical support for the subsequent exploration and development of shale gas reservoirs in Wulalike Formation in the western margin of Ordos Basin.

As the lack of in-depth understanding of the characteristics and main control factors of carbonate fault-controlled reservoirs of the middle-lower Ordovician extra-deep carbonate rocks in the eastern part of the Aman transition zone in the Tarim Basin,the well location deployment and development plan preparation in this area are limited to a certain extent. Therefore,the characteristics and main control factors of the middle-lower Ordovician reservoirs in the eastern part of the Aman transition zone are studied by using the data of cores,casting thin sections,imaging logging images,log and production performance. The results show that the fault-controlled reservoirs of the middle-lower Ordovician carbonate rocks in the eastern part of the Aman transition zone are dominated by sparry arenaceous limestone,and there are 9 reservoir space types,including fractured cavities,breccia pores,dissolved vugs, intercrystal pores, intercrystalline dissolved pores,macroscopic structural fractures,structural fractures,stylolites and dissolued fractures,and the main reservoir types are cave,fractured-vuggy and fracture. The development of reservoirs is mainly controlled by sedimentation,faulting and karstification,that is, grainstone under the background of high-energy shoals provides the material basis for reservoir development,strike-slip faults are the tectonic prerequisites for reservoir formation,and karstification has an improving effect on the reservoir space in the study area and promotes the development of reservoirs.

As one of the unconventional energy sources,shale oil is important in increasing reserves and production. However,due to the difficulty in mining shale oil and the high construction cost,it is necessary to clarify the shale oil enrichment factors in order to achieve accurate positioning and effective development. Based on the shale layers of the Es₃ of Qibei subsag in Qikou Sag of the Bohai Bay Basin,comparative analysis of organic matter and occluded hydrocarbons of different lithofacies types is carried out,and the lithofacies types containing oil and gas with industrial value are clarified. By establishing the intersection relationship between mineral composition and free hydrocarbons,and analyzing the correlation between the number of fractures and laminae,the main controlling factors in the shale oil occurrence space are clarified. Research shows that the laminated shale and bedded mud shale are the main enriched lithofacies of shale oil in Shahejie Formation of the area,with good pore structure,high organic carbon content,high density of bedding fractures,and high occluded and free hydrocarbon content,which has production and development advantages. The study shows that lithofacies type,organic matter type and abundance,thermal evolution degree,rock minerals composition,and the number of laminae are the main factors affecting the enrichment and high yield of shale oil.

The high-quality source rock of Lianggaoshan Formation in northeastern Sichuan Basin is an important horizon for continental shale oil & gas exploration and development. To guide the future exploration and development of continental shale oil & gas in this area,the macro and micro characteristics of the reservoirs were analyzed by mud logging techniques such as rock pyrolysis,scanning electron microscope and X-ray diffraction,and the main control factors of shale oil & gas in Lianggaoshan Formation were deeply discussed. The following findings are obtained： There are three types of typical lithological combination sequences in Lianggaoshan Formation,which reflect a relatively complete lacustrine transgression-lacustrine regression cycle vertically; The hydrocarbon generation potential of different source rocks varies greatly,among which black shale has the strongest hydrocarbon generation potential with high total organic carbon（TOC）,high free hydrocarbon（S₁） and high pyrolytic hydrocarbon（S₂）,while argillaceous siltstone has the weakest hydrocarbon generation potential;The high-quality shale reservoir space is mainly composed of inorganic pores,organic pores and microfractures,and its main mineral types are quartz and clay minerals,with good reservoir performance and fracability. The following understandings have been obtained from the further analyses： The dominated high-quality lacustrine shale of Lianggaoshan Formation are mainly controlled by sedimentary environment and formed in reducing environment with deeper water bodies,which is conducive to the organic matter burial and preservation. The larger thickness of the strata makes it difficult for shale oil & gas to overcome the migration resistance and is mastly retained in the middle of the source rocks, and a small amount of oil & gas in the upper and lower shales may partially have expulsion and migration under pressure. It is concluded that the lacustrine shale of Lianggaoshan Formation in northeastern Sichuan Basin has the moderate degree of organic matter evolution,good microfracture development and fracability,and good potential for shale oil & gas enrichment and development.

The Chang 7 Member of Yanchang Formation in Yan'an area,southeastern margin of Ordos Basin is a typical continental shale gas exploration and development horizon. In order to understand the influence of pores with different genesis and their structures on the adsorption of continental shale gas,the mineral composition of the shale in Chang 7 Member of Yanchang Formation was studied by using organic geochemical methods. The pore size distribution characteristics of shale were studied by nitrogen low temperature adsorption method,and the adsorption characteristics of nitrogen in shale were analyzed by fractal theory,thereby revealing the heterogeneity of shale pore structure. For the shale in Chang 7 Member,the organic carbon content is 0.50%-6.43%,with an average of 2.93%; the content of brittle minerals is 0-46.00%,with an average of 7.75%; the clay mineral content is 21.00%-59.00%,with an average of 40.95%. According to the fractal fitting curve of the shale samples of Chang 7 Member,the fractal dimension can be divided into two segments,the fractal dimension of the first segment（D₁） is 2.029 4-2.501 5,with an average of 2.271 0,which corresponds to the larger micron-scale fractures in the shale of Chang 7 Member,and the fractal dimension of the second segment（D₂） is 2.489 3-2.622 3,with an average of 2.555 0,which corresponds to the nano-scale pores,and its pore structure is more complex,the inner surface of the pores is relatively rough,and it has strong heterogeneity. In the shale of Chang 7 Member,the nano-scale pores are the main reservoir space for adsorbed gas,while larger micron-scale fractures are the reservoir space and flow path for free gas.

The depositional environment of Chang 7 Member of the Triassic Yanchang Formation in Ordos Basin is mainly semi-deep and deep lacustrine facies,in which the deep water gravity flow deposition exists widely. In-depth analysis of these depositional characteristics and their spatial distribution regularities is of great significance for guiding oil and gas exploration. Based on Chang 7 Member in the southwest of Ordos Basin,the specific types and reservoir characteristics of deep water gravity flow deposition in this interval are clarified by means of fine core description,log data analysis and laboratory microscopic observation of cored wells. The sedimentary microfacies of deep water gravity flow in Chang 7 Member mainly include three typical types： sliding-slumping,sandy debris flow and turbidity current,which can be subdivided into eight types of lithofacies combinations. According to the well logging data,Chang 7 Member is divided into six types of representative electrofacies combinations. In terms of reservoir sand bodies,the sandy clastic flow and turbidity current deposits are dominant,and the sliding-slumping deposits are secondary,but they cannot be ignored. These reservoir sand bodies generally have low maturity,complex pore throat structure and poor physical properties. Different types of diagenesis show significant differences in the transformation effects on reservoir pores. This finding is of great significance for understanding the reservoir performance and evolution of deep water gravity flow deposition.

In order to deeply understand the geological characteristics and reservoir characteristics of He 8 Member reservoirs from the Upper Paleozoic in Su 49 block,a systematic study of the reservoirs of it has been carried out from the perspectives of petrologic characteristics,pore types,pore-throat characteristics,and diagenesis by using core observation descriptions,casting thin sections,scanning electron microscope, cathodeluminescence and other experimental analysis data. The results show that the main rock types in He 8 Member reservoirs are lithic quartz sandstone and quartz sandstone,and the reservoir clast composition is mainly quartz（including quartz and flint）,followed by cuttings components,and there are some trace amounts of feldspar particles in some areas. The pore type in the study area is secondary pore,and the primary intergranular pore occupies a secondary position,and mainly characterized by the development of small pore throats. The lower sub-member of He 8 Member has good physical properties,with an average porosity of 8.15% and an average permeability of 0.58 mD. The physical properties of the upper sub-member of He 8 Member are second,indicating that the reservoirs of He 8 Member in the study area belong to tight ultra-low permeability sandstone reservoirs. The main diagenesis in He 8 Member includes compaction,cementation,and dissolution,of which the dissolution-formed kaolinite intercrystal pores and dissolution pores have a significant improvement effect on the reservoir physical properties. Micro-fractures have greatly improved the physical properties of reservoirs in the central and eastern parts of the block. The results of this study will help us better understand the natural gas storage rule in the area,provide scientific basis for reservoir stimulation and efficient development,and thus support the productivity construction and efficient development of the block.