With the introduction of AI and big data technologies, the oil and gas exploration field has realized a paradigm shift in the drilling process from being experience-driven to data-driven. At the same time, geology-engineering integration services also have shifted from "drilling wells successfully" to "drilling wells quickly". However, the integration technology still remains at the optimization and improvement phase of the working mode and operation process. During drilling in complex formations, there are still technical problems such as limited penetration rate, low trajectory control accuracy, and lagging response to downhole risks, which restrict the further development of this field. AI technology provides a new path to break through the bottlenecks： Through dynamic Mechanical Specific Energy （MSE） modeling and real-time optimization, accurate mapping from formation characteristics to engineering parameters is achieved. With this as the core, an intelligent drilling optimization system driven by the three cores of "data, decision and execution" has been built to achieve full-process closed-loop optimization. It has been successfully applied in the on-site drilling construction process, verifying that this system can improve penetration rate, reduce non-production time, and effectively control the deviation of the wellbore trajectory. This study provides theoretical support for the development of the intelligent drilling optimization system, reveals the transformation of digital technology to the traditional drilling optimization working mode, and provides replicable solution at the engineering level.

To improve the precision of reservoir identification by mud logging in oil and gas exploration, a mud logging system based on infrared spectroscopy technology has been developed. The hardware of the system adopts a miniaturized and integrated design with a high-sensitivity infrared detector, realizes the comprehensive identification of gas spectral features through infrared spectroscopy scanning technology, and completes the rapid and automatic analysis of hydrocarbons in drilling fluid. The software of the system has functions such as remote data sharing, software mapping and data analysis, which is used to realize stratigraphic interpretation and evaluation. The field test shows that the infrared spectroscopy gas logging system can quickly find the show of gas and oil, and has obvious technical advantages in the evaluation of thin beds and fracture-type reservoirs. It also has the advantages of high precision, low error, rapid response and good repeatability. It can meet the needs of mud logging operations in different regions and effectively improve the accuracy of reservoir evaluation.

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.

Mud logging technology has the four advantages of "more,faster,better,cheaper",but the development of this industry is still facing the four challenges of "weak basic theory,insufficient advanced technology,shortcomings in technical services,and poor development ecology". It is urgent to grasp the source of "thinking mode" to drive the benign development of mud logging technology innovation. Therefore,this paper puts forward three basic thinking modes of theoretical thinking,system thinking and in-situ thinking that should be followed in the innovation of mud logging technology. Theoretical thinking includes three levels：application of theory,extension of theory and innovation of theory. System thinking includes three levels：technology chain thinking,technology series thinking and technology system thinking. In-situ thinking includes two levels：in-situ thinking of hydrocarbon reservoirs and in-situ thinking of geology-engineering integration. These three thinking modes complement each other and constitute the cornerstone of innovative thinking in mud logging technology. These basic thinking modes have a certain guiding and promoting role in enriching the mud logging theory system,deepening the mud logging technology system,improving the mud logging services system,and perfecting the mud logging ecosystem.

With the improvement of drilling technology,the drilling speed of drilling exploration has been greatly increased,especially in the offshore drilling platforms and shallow well drilling,the drilling time per meter is extremely small （generally 0.1-1.0 min/m）,while the delay time of the gas collection pipeline for mud logging samples is usually the range of 2-10 min. When a single pipe is connected or the pump is stopped for special reasons,the sand return depth in the mud logging acquisition software will stop updating. However,the gas corresponding to the sand return depth in the sample gas pipeline is still being analyzed by chromatograph. The result is that the gas logging data analyzed by the chromatograph cannot correspond to the lagged well depth,and the gas logging data is "lost". The amount of "lost" data is determined by the lag time of the gas pipeline and the drilling time. In order to ensure the complete collection of gas logging data,an automatic control device for mud logging sample gas collection has been developed. The device collects real-time drilling status through RS-232 serial communication,and uses a microcontroller control unit in the integrated circuit to control the electromagnetic valve on the automatic control device to switch the sample gas pipeline,achieving accurate analysis of the sample gas in the pipeline and avoiding the "loss" of gas logging data.

With the deepening of oil and gas exploration and development, the traditional gas logging interpretation methods mainly based on charts are unable to meet the evaluation needs of the relationships between the complex reservoirs and oil, gas and water. In recent years, the rapid development of big data analysis and machine learning has provided a new direction for gas logging interpretation. Based on gas logging interpretation data from multiple wells, data preprocessing and feature engineering methods are applied to process the gas logging data, and five common machine learning models （KNN, NB, SVM, MLP, LightGBM） are used for modeling interpretation,application,comparison and analysis. The results show that the comprehensive performance of SVM and LightGBM models is good with an average prediction accuracy of over 87%, which can meet the actual interpretation needs. The machine learning model solves the problems of the insufficient flexibility of the traditional interpretation charts and the difficulty of extracting deep information due to the dimensional limitations, and significantly improves the interpretation accuracy, which has the practical value of promotion and application.

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.

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.

Regarding the identification of fluid properties in low and ultra-low permeability reservoirs in Liu-2 and Liu-3 Members in Weixinan Sag,Beibuwan Basin,conventional logging techniques and interpretation methods are severely limited under the contamination of oil-based drilling fluid,resulting in insufficient accuracy of fluid property discrimination and difficulties in real-time decision making on site. Using the gas characteristic spectrum discriminant method,original absorption rate spectrum discriminant method,and oil and gas index quantitative discriminant method of the hydrocarbon phase state evaluation technology,the fluid properties of the low-permeability reservoirs in this block are analyzed,and the extended applications of this technology in fracture identification and oil and gas sources are discussed. The results show that the hydrocarbon phase state evaluation technology has played a unique advantage in oil and gas classification and reservoir water content identification. For the identification of fluid properties in more than 20 wells of various well types and reservoirs in different formations in Weixinan Sag,the coincidence rate of the comprehensive interpretation is over 90%. This method effectively solves the problem of fluid property identification caused by the dual factors of oil-based drilling fluid pollution and low-permeability reservoirs in Weixinan Sag,provides reliable technical support for offshore oil and gas field development and has significant value for popularization and application.

Rock hardness and plasticity coefficient are important indicators for oil drilling, and the method of obtaining these indicators by core experiments is limited due to the difficulty and high cost of full scale core coring. Based on this background, the cores of Qingshankou Formation in an oilfield are selected to construct data sets of hardness, plasticity coefficient and element characteristics through conducting static load indentation experiments and XRF element experiments. The Pearson correlation analysis and the algorithm of particle swarm optimization BP neural network （PSO-BP） were used to reveal the main controlling elements of rock hardness and plasticity coefficient, and a method of shale hardness and plasticity coefficient evaluation while drilling based on XRF element logging was established. The predictive results show the major elements for main controlling shale hardness are Fe, Al, K and Ca, and the trace elements are Cr and Rb, shale hardness is positively correlated with Ca element and negatively correlated with other main controlling elements. The major elements for main controlling plasticity coefficient is Ti, and the trace elements are Cd, Nb, Ni and V, plasticity coefficient is negatively correlated with Ti and positively correlated with other main controlling elements. The network error of the shale hardness prediction model is 8.06×10^-8, and the network error of the plasticity prediction model is 3.02×10^-11, both of which are below the preset thresholds. From the application of this method in tracking while drilling shale oil, it can be known that the shale host in the work area belongs to the low-plasticity rock of medium-soft grade 3, so the suitable PDC drill bit is recommended, and a high penetration rate is obtained. The method provides technical support for drilling dynamic optimization.

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.

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.

In order to solve the problem of accurate identification of fluids with different properties in complex reservoirs in oil and gas exploration,based on the application data of infrared spectrum technology in the Bohai Bay Basin,five sensitive wavelengths were optimized and four sets of key parameter combinations were screened by analyzing the spectral absorption efficiency curve characteristics of fluids with different properties. Through constructing the multiparameter fusion charts,the rapid identification and accurate evaluation of oil layers,high-GOR oil layers,gas layers,and oil-bearing water layers have been achieved. Validated by data of on-site testing while drilling in 6 wells,the interpretation coincidence rate of infrared spectrum technology reached 92.3%. This method not only improves the qualitative analysis ability of reservoir fluid,but also provides more efficient technical support for hydrocarbon reservoir exploration and development,and has important engineering application value.

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.

The development of drilling technology has greatly improved drilling efficiency,but it has made it difficult for traditional naked eye debris identification methods to meet efficient logging. In addition,the differences in the technical level of field personnel have seriously restricted the improvement of debris logging quality. Therefore,a digital intelligent identification system for debris that integrates artificial intelligence,image analysis and Internet of things technology has realized automated collection,real-time processing and intelligent interpretation of debris data. This technology integrates high-resolution image acquisition,digital image feature extraction,and an AI lithology classification model based on deep learning. Practical application in Changqing Oilfield shows that the lithology identification accuracy of the debris digital intelligent identification system has been increased to more than 90%,effectively solving the problem of difficulty in naming micro rocks in traditional manual identification. The system not only significantly improves the accuracy and efficiency of cuttings logging,but also provides key technical support for the transformation of logging operations from empirical to intelligent,which has important practical significance and broad application prospects for improving the overall logging quality.

In the exploration of Pearl River Mouth Basin, a large amount of CO₂ gas was found, and its genesis is complex, covering organic origin, inorganic origin and mixed origin. The study on CO₂ formation mechanism in this area is of great significance to judge the source of oil and gas and the mode of accumulation. However, the CO₂ monitored during mud logging while drilling may originate from the added drilling fluid materials, which has a significant influence on CO₂ genesis study. Because CO₂ inherits the geochemical information of maternal materials during its formation, different ${{\delta }^{13}}{{C}_{C{{O}_{2}}}}$ can indicate different biological sources. Through the design of relevant experiments, the ${{\delta }^{13}}{{C}_{C{{O}_{2}}}}$ values of the drilling fluid materials are obtained. Compared with the ${{\delta }^{13}}{{C}_{C{{O}_{2}}}}$ values measured during mud logging while drilling process, the sources of CO₂ can be confirmed. The ${{\delta }^{13}}{{C}_{C{{O}_{2}}}}$ values in the drilling fluid materials from wells A and B are quite different from the ${{\delta }^{13}}{{C}_{C{{O}_{2}}}}$ values while drilling, which indicates that CO₂ originates from formation rather than the drilling fluid materials. According to this, it is confirmed that CO₂ in well A of Enping Sag is the organic origin of organic matter pyrolysis, and CO₂ in well B of Eastern Yangjiang Sag is the inorganic origin of mantle source. This study provides important geochemical basis for oil and gas exploration in Enping Sag and Eastern Yangjiang Sag.

In the field of geologic exploration, density logging curve is of great significance in determining reservoir porosity, identifying gas reservoirs, judging lithology, dividing oil-water interfaces, identifying fluid types, and improving inversion accuracy. However, in practical operation, logs may be lost or distorted due to instrument failures, data transmission errors or external interference. To solve this problem, this paper proposes a density logging curve reconstruction method based on Transformer-LSTM fusion model. This method utilizes Transformer′s self-attention mechanism to effectively capture the long-distance dependency relation in log data, and combines with the recursive characteristics of Long Short-Term Memory （LSTM） to significantly improve the reconstruction accuracy. By preprocessing, model construction and training of log data from Y zone of Ordos Basin, the performance is compared with bidirectional gated recurrent unit （BiGRU）, deep neural networks （DNN）, multiple regression analysis （Logistic）, temporal convolutional network （TCN） and Transformer model. The results show that Transformer-LSTM fusion model performs well in density logging curve reconstruction, especially in terms of reconstruction accuracy and generalization ability. The experimental results verify that the model is capable of reconstructing high-precision density curve data, providing reliable support for geologic exploration.

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.

Gulong shale mainly consists of large suites of clayey felsic shales with many pore types and complex pore structures,and its reservoir performance is the core in shale oil geological research,but conventional logging methods are difficult to effectively evaluate such micro-nano pores. To solve this problem, NMR technique is applied to geophysical logging to full-scale characterize the porosity and pore structure of shale reservoirs. By building the conversion relationship between NMR relaxation time （T₂） and rock pore diameter, the proportion of large pores in Gulong shale was characterized by the specific T₂ spectrum components to evaluate the shale reservoir performance quantitatively, systematically revealing the pore structure differences and distribution law of Gulong shale reservoirs. Based on the results of the reservoir performance evaluation,the target strata with large porosity and good pore structure were selected to optimize the horizontal well trajectory designs. The results show that with the changes of rock mineral compositions, there are differences in the vertical pore structures of Gulong shale reservoirs. Among them, the middle-lower part of Q₉ oil layer has the highest proportion of large pores and the best pore structures. The overall production of horizontal wells in the expanded test area,which is implemented by using this part as the core target window of horizontal wells,has been greatly improved. This technology will provide favourable support for the follow-up efficient development of Gulong shale oil.

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.

The exploration targets of Bohai Oilfield are shifting towards oil reservoir zones with complex geologic conditions, resulting in a significant increase in the difficulty of oil-water layer interpretation and evaluation. The traditional comprehensive evaluation method combining mud logging and well logging technologies restricts the operation efficiency to a certain extent due to the hysteresis of well logging technology. Therefore, a quantitative calculation model of oil saturation based on geochemical logging was established. This model comprehensively considers the distribution laws of oil-gas-water three-phase flow in reservoir pores and the influence of petrophysical properties （crude oil density, reservoir porosity, matrix density, etc.） on oil saturation, providing a new angle of view and tool for accurate assessment of reservoir fluid properties and realizing the real-time evaluation of reservoir fluid properties. Verified by the data of the wells newly drilled in X block of Bohai Oilfield, the accuracy rate of model interpretation was 86.67%.The oil saturation calculation model can provide strong support for oil-gas exploration and development in Bohai Oilfield.

Aiming at the technical problem that it is difficult to quantitatively analyze the contamination degree of wireline formation test samples in oil-based drilling fluid environment due to the miscibility of crude oil and drilling fluid, this paper proposes a comprehensive quantitative evaluation method based on conventional fluid physical comparative analysis and saturated hydrocarbon gas chromatography component comparative analysis. Through the establishment of the sample density analysis chart and the gas chromatographic analysis chart, the calculation software of formation crude oil drilling fluid contamination proportion was developed, and the quantitative evaluation of the effects of oil-based drilling fluid on the contamination degree of the wireline formation test samples was realized. The method has been applied to 14 wells in Weixinan Sag of Beibu Gulf Basin. The analysis results show that the maximum absolute errors are within 5% compared with the laboratory sample analysis results and oil testing productivity analysis data. The field application results show that the method has high analytical accuracy and practicability, and can realize the rapid and accurate evaluation of oil-based drilling fluid contamination rate in wireline formation test samples.

Western oilfields such as Xinjiang Oilfield and Tarim Oilfield cover vast territories. Due to communication signal coverage limitations in traditional transmission networks, data collected at some well sites cannot be transmitted back in a timely manner. This has certain impacts on optimizing drilling operations at the frontier well sites, real-time monitoring of drilling operations at the rear base, and geological interpretation research. To address the challenge of real-time mud logging data transmission caused by insufficient network coverage, this paper proposes a real-time mud logging data transmission system based on Beidou short messages. By analyzing the Beidou 3 satellite navigation system transmission protocol, constructing a Beidou mud logging data transmission test environment, and developing Beidou mud logging data real-time transmission system, an integrated closed-loop transmission system for mud logging data "acquisition-encoding-transmission" has been achieved. This research not only resolves traditional network dependency issues but also reduces energy data security risks through the autonomous controllability of the Beidou protocol. It provides highly reliable, low-cost communication technology support for oilfield digital transformation and offers a practical example for the large-scale application of the Beidou system in the energy sector.

Aiming at the problem of the low coincidence rate of the interpretation of the reservoir fluid properties in gas exploration wells in Ordos Basin, the key influencing factors of NMR logging technology were systematically analyzed. Based on core experimental data, a quantitative evaluation model centered on NMR porosity and the dynamic ratio of the initial state movable water saturation to the initial state irreducible water saturation was reconstructed, breaking through the excessive reliance on data quality by the traditional intuitive identification method of spectra. Field application shows that the model significantly improves the accuracy of reservoir water content discrimination by standardizing data acquisition process and establishing reservoir gradation and classification standards, and the interpretation coincidence rate increases from 79.23% to 85.32%. The research results confirm that the dynamic ratio parameter model can effectively characterize the fluid distribution characteristics of low-porosity and low-permeability reservoirs, thereby providing reliable technical support for the optimization of well completion test intervals and the establishment of reservoir stimulation schemes under complex geologic conditions, and has promotion value for the exploration and development of similar hydrocarbon reservoirs.

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.

The identification of fluid properties in low-contrast reservoirs is a technical bottleneck in the field of oil-gas exploration and development, its core characteristics are manifested in the weak differences in resistivity between oil layers and water layers, which are difficult to effectively distinguish on conventional log response. In response to this problem, taking the shallow low-resistivity oil layers in Hanjiang Formation of Enping Sag and the Paleogene high-resistivity water layers in Lufeng Sag, Pearl River Basin as examples, a "3-axis linkage" mud logging evaluation technology system is constructed: gas logging identifies hydrocarbon anomalies, real-time fluid logging quantitatively characterizes hydrocarbon abundance and geochemical logging identifies the phase states of the fluids （oil or water layers）. On this basis, the multiparameter quantitative interpretation charts have been established, which effectively solve the evaluation difficulties in the reservoirs of thin interbedded layers and low-resistivity oil layers, and the accuracy of regional fluid property identification has been increased to more than 85%. In practice, well A 3H in Enping Sag has obtained a high-yield oil flow of 823 t/d, and in Lufeng Sag, the interfaces of high-resistivity water layers have been successfully identified, which make the identification accuracy of high-resistivity water layers with 55% of the traditional interpretation based on logging resistivity data increase to 82%, and provide a reliable technical support for the high efficiency development of the complex hydrocarbon reservoirs in South China Sea.

With the deepening of oil and gas exploration, it has become an inevitable trend to develop from middle-shallow to deep layers. In particular, major breakthroughs have been made in the deep exploration of the Permian in Mahu Sag and the Carboniferous in Shawan Sag, Junggar Basin, and the deep exploration has become an important replacement field for oil field reserve increase and production increase. However, in the Permian and Carboniferous strata, there are diverse rock types, complex compositions, fine drill cuttings, leading to difficulty in quickly identifying lithology, which restrict the efficiency deep oil and gas exploration. Therefore, X-ray diffraction mineral logging and Gamma spectrometry logging while drilling technologies have been introduced for research on the deep and mainly developed Permian and Carboniferous strata. Combined with thin section identification, the lithology identification charts can be established by dividing blocks and layering positions through the rock-mineral index model and the optimization of typical minerals. This provides a new method for rapid identification of lithology and precise horizon determination, guaranteeing drilling safety and further improving mud logging technology system. At present, a total of 13 wells have been applied, with the coincidence rate of over 82% for lithology identification. In the field of deep oil and gas exploration and development, the application effect is obvious.

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 deepening of exploration and development of oil and gas resources, it is more important to accurately monitor the three pressures of formation （pore pressure, collapse pressure and fracture pressure）. However, although the traditional formation three-pressure monitoring method has been widely used, it has the limitation of relying on human experience and parameter setting. In order to realize the real-time and accurate monitoring of formation three pressures, this paper takes four wells to be monitored in Beidagang buried hill structural belt of Huanghua Depression as an example. Based on the drilling, recording and logging data of completed wells around the wells to be monitored, combined with advanced machine learning algorithms such as Extreme Gradient Boosting （XGBoost）, light Gradient Boosting Machine （LightGBM） and Random Forest （RF）, the drilling and logging data are coupled with the logging calculation pressure based on poroelastic mechanics theory. The results show that the pore pressure prediction average relative error of all measured pressure points in the study area is 6.32%, and the overall monitoring accuracy is over 93%. The multi-parameter coupled formation three-pressure monitoring technology has high prediction accuracy, good generalization performance and feasibility. In view of the fact that this method can achieve accurate monitoring of three pressures while drilling in multi-lithologies, multi-types of reservoirs, and multi-pressure genesis formations, it can be popularized and applied to three pressures while drilling monitoring in other complex oil and gas reservoirs, providing technical support for integrated risk prediction and safe and efficient drilling construction of geological engineering.

Aiming at the problems of complex geological conditions of deep coal rock, easy collapse of target coal rock, difficult logging operation, limited log information, and immature comprehensive evaluation of mud logging reservoir quality, and relying on the key mud logging parameters of more than two new wells in Changqing Oilfield in recent two years, this paper establishes a set of deep coal-rock gas reservoir quality evaluation technology based on mud logging technology from four aspects： rock quality, source rock quality, gas quality and engineering quality. This evaluation technology has been successfully applied to the fracturing layer selection scheme design of 15 deep coal-rock gas wells in Changqing Oilfield, highlighting the technical advantages in comprehensive evaluation of mud logging and achieving deep fusion of geology-engineering integration. This technology effectively meets the exploration and development needs of deep coal-rock gas reservoirs, provides reliable technical support for horizontal well trajectory optimization and fracturing layer optimum selection, and verifies its strong advantages in deep coal-rock gas evaluation.

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.

Pai 612 block of Chunfeng Oilfield is the first block to develop super-extra viscous crude oil reservoirs in western Junggar Basin. Currently,multi-cycle steam injection exacerbates the heterogeneity of the reservoirs,and there are development problems such as frequent inter-well steam channeling and uneven reserve production. In order to deepen the understanding of reservoir heterogeneity,it is urgent to carry out differential lithofacies study and geologic modeling of reservoirs. The reservoirs of Pai 612 block are mainly divided into high-quality sandstone facies and calcareous sandstone facies. On this basis,the seismic data analysis and horizontal well stratigraphic correlation were used to improve the accuracy of structural control,and the structural model was established. Combined with the lithofacies study and the analysis of core data and log information,the linear correspondence between the lithofacies and the gamma curve of horizontal wells was determined,and the lithofacies data of the horizontal wells was quantitatively calculated to establish a differential lithofacies model for the block. The vertical well attribute model was established by regressing interval transit time and physical properties based on the analyzing and rock sample testing data of the cored wells, and the horizontal well attribute model was established based on the correlation between shale content and physical properties. Finally,by comparing the static and dynamic characteristics of different lithofacies reservoirs,as well as analyzing the production capacity,the net to gross ratio of different lithofacies was determined,and the production of calcareous sandstone facies accounted for 66.7% of high-quality sandstone facies. The different lithofacies differentiation net to gross ratio model of the final completion lays the foundation for improving remaining oil recovery efficiency in the later stage.

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.

Liuheying-Daxinzhuang structural belts are second-level oil-bearing structural belts located at the southwestern end of the western zone in Langgu Sag, with low degree of exploration. Due to its complex structure and sparse survey grid, the hydrocarbon accumulation regularities remain unclear. Based on the data of well-seismic combination, actually drilled geology and analytic test, the hydrocarbon accumulation conditions and exploration potential are deeply analyzed. The results are obtained in four aspects. First, The Es₃^l dark mudstone is the dominant source rock beds and has good oil source conditions with a large thickness of 600-1 600 m, high organic matter abundance of TOC 0.64%-1.03%, and main kerogen type Ⅱ₂-Ⅲ. Second, As a whole, Es₃ reservoirs are dominated by medium-high porosity and low permeability, with the best physical properties in Es₃^m of Daxinzhuang arched structural belt, and the reservoir-cap rock assemblage in Es₃ is superior. Third, The structural belts are clamped between the two large oil-generating troughs of western Gu′an and southern Liuheying, the oil and gas enrichment is jointly controlled by the nose-like structural trap, the turbidite sand body distribution, and the dual effects of oil source fault transport and later tectonic uplift, forming the down generated up stored and side generated lateral stored reservoir-forming patterns. Fourth, two reservoir-forming patterns of ridge-type and toothbrush-shaped structures were constructed to reveal the banded enrichment regularity of oil and gas along the structural high parts and faults. G 8 trap and No.2 trap in northern L 1 were selected as the most favorable targets from 49 traps, with the total quantity of oil resources of over 500×10⁴ t and natural gas of nearly 40×10⁸ m³ predicted. The results provide theoretical guidance and technical support for the subsequent research and exploration of oil-bearing traps in the complex structural zones of Langgu Sag.

To tackle the limitations of ultrasonic wave liquid level sensors in drilling fluid outlet buffer tank level monitoring at oilfield drilling sites, which particularly include susceptibility to environmental interference and insufficient measurement accuracy. The improvement plan for 78 GHz Frequency-Modulated Continuous Wave （FMCW） radar liquid level sensor is proposed in this study, which achieves millimeter-level precision （error of ±3.2 mm） with narrow （≤6°） by optimizing beam angle and anti-jamming algorithms. Application to well W 204HX-X in Southwest Oil & Gas Field demonstrated that superior performance: compared to ultrasonic wave sensors, the radar sensor improved measurement accuracy by 79.6% and data stability by 16.2% under severe liquid surface fluctuation conditions. The technology effectively overcomes measurement deviations caused by high-temperature smoke and water mist interference while enhancing monitoring stability.This research reveals and expands the applicability boundaries of high-frequency radar technology in complex industrial environments. Both cost-benefit analysis and functional evaluations confirm its viability as a replacement for traditional ultrasonic wave level sensors. The findings provide a novel technical pathway for intelligent drilling fluid level monitoring equipment development in oil and gas drilling operations.

The Middle Indus Basin is located in the central part of the Indus Basin, which is a foreland basin developed from the passive continental margin. Previous research suggests that the factors controlling the formation of tight gas reservoirs in foreland basins are fault transport of oil and gas and fracture transformation of reservoirs, with oil and gas enriched in fracture developed zones near the faults. However, the drilling results in the local area are different from the previous research results. Not all faults in the area are enriched with oil and gas. Most of the wells successfully drilled in this area are distributed along NS-trending faults, and exploration near the NW-trending faults has not been broken through. Therefore, it is urgent to conduct more in-depth research on the differences in fault-controlled reservoirs, and explore tight gas reservoir formation models suitable for this area. Based on the understanding of regional geology and fine interpretation of seismic data, the characteristics and development stages of faults in M area have been summarized, with a focus on the structural evolution processes and stress conditions that give rise to these fault characteristics. This paper analyzes the sealing ability of these faults, and finally reveals fault controlling regulation on differential hydrocarbon accumulation in this area. The research provides a theoretical foundation for tight gas exploration in the Middle Indus Basin. The results indicate that NW-trending faults suffered compressive stress in Early Cretaceous epoch, leading to significant shale smearing and a certain sealing capability. The nearly NS-trending faults functioned as the main migration pathways for gas, controlling the hydrocarbon migration and accumulation. The tight sandstone reservoirs on both sides of these faults have been transformed by faults and fractures, and have great accumulation potential, which point out the way for the next exploration and development of the gas field.

The source direction, sedimentary facies evolution history and distribution law of oil-bearing series of Shahejie Formation in Wen'an slope, Jizhong Depression, are still unclear. Based on core, well logging, seismic and other geologic information, the provenance system and sedimentary facies characteristics of Shahejie Formation were discussed in depth through paleogeomorphological restoration method and heavy mineral Q type clustering procedure. The results indicate that the sedimentation of Shahejie Formation in Wen′an slope has multi-source characteristics, and the provenance mainly comes from the northwest of Niutuozhen uplift and the southeastern Wen′an slope. Two major source areas developed multiple transport pathways. Sediments have developed several graded sand bodies along the slope topography. Influenced by the steep western and wide-flat eastern paleogeomorphological pattern, Shahejie Formation mainly developed three sedimentary facies during its sedimentary period： fan delta, braided river delta and lake. During Member 3 of Shahejie Formation sedimentary stage, five sedimentary subfacies were mainly developed in the study area： fan delta plain and front, braided river delta plain and front and shore-shallow lacus. Multiple delta lobes were formed along the subaqueous distributary channels. During Member 2 of Shahejie Formation sedimentary stage, the northwest of the study area mainly developed shore-shallow lacustrine mud microfacies, while the southeast mainly developed two sedimentary subfacies of braided river delta plain and front. During Member 1 of Shahejie Formation sedimentary stage, the northwest of the study area mainly developed two sedimentary subfacies of fan delta plain and front. The southeast mainly developed braided river delta plain, with a small amount of braided river delta front sedimentary subfacies. The study results can provide theoretical basis and guidance for the further refined exploration and development of hydrocarbon resources in Shahejie Formation of Wen′an slope in Jizhong Depression.

The shale oil layers of the third member of Shahejie Formation in Qikou Sag has higher clay mineral content, stronger water sensitivity than that of Ek₂ of Cangdong Sag, developed fracture system, and extremely complicated engineering in the drilling process. Since the use of white oil-based drilling fluid in horizontal wells in the third member of Qikou Shahejie Formation in 2023, drilling and development efficiency has been significantly improved, but it has a great impact on gas logging. By comparing and analyzing the response characteristics of gas logging under water-based and oil-based drilling fluids, this paper summarizes the adsorption characteristics of oil-based drilling fluids to total hydrocarbons and hydrocarbon components under different gas kick degrees, and based on the data, the measured relative percentage change rate of each component, the gas logging correction method is studied, and the gas logging interpretation chart and evaluation standard are established, which provide the basis for the evaluation of shale oil sweet spots under oil-based drilling fluid,and have certain guiding significance through the verification of production effect.

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.

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.