Recently, a major breakthrough has been achieved in lithologic reservoirs in the eastern slope of Fukang Sag—Well
Kangtan 1, a risk exploration well of PetroChina, which obtained high yield oil flow of more than 100 tons from each of the two
layers in the Permian. The favorable conditions for hydrocarbon accumulation have been systematically discussed based on understandings of Well Kangtan 1 to evaluate the exploration potential and prospects in Fukang Sag. Results show that there are two sets of large-scale source rocks in the Permian and Carboniferous in Fukang Sag, which provide promising hydrocarbon source
potential. Controlled by the paleo-geomorphology, two sets of thick and large-scale reservoirs in the Middle and Upper Permian
are developed in the eastern slope and sag area with similar distribution pattern, providing favorable conditions for the formation
of lithologic-stratigraphic oil and gas reservoirs. The well-matched time-space configuration of thermal evolution of source rock
and tectonic evolution, and the late sealing conditions in the updip direction result in the differential accumulation and orderly
distribution of two-stage oil and gas reservoirs. The sag area is the main field for late accumulation of oil and gas. The three
sub-sags in the slope are favorable exploration targets in Fukang Sag, which show great potential for large-scale exploration of
lithologic reservoir in slope and sag areas.

Buried hill has become an important field for oil and gas exploration in sea areas of China and the depth of exploration is extended to greater than 3500 m. After the major discovery of Bozhong 19-6 Gasfield in Archaeozoic single-layer metamorphic buried hill, hydrocarbon accumulation potential of buried hill with multi-layered structures is another geological problem to be clarified urgently. Regional geological and tectonic evolution have been studied and hydrocarbon accumulation conditions analyzed
by well, seismic and geochemical data. The result shows that the development of buried hill and reservoir is controlled by
regional tectonic activities and their induced fracturing. The discovery of Bozhong 13-2 Oil and Gasfield (proven geological reserves
of 100 million tons of oil equivalent) confirms that the Archaeozoic multi-layered metamorphic granite buried hill has excellent
hydrocarbon accumulation conditions. Further analysis on accumulation elements of Bozhong 13-2 Oil and Gasfield and
comparison with those of Bozhong 19-6 Gasfield indicate that the multi-stage stereoscopic fracture network and effective connection with hydrocarbon supply window are the key to reservoir development and hydrocarbon accumulation in buried hill. The “short-axis discontinuous reflection” associated with fault is a marker of Archaeozoic high-quality buried hill reservoir. The combination of overpressure and wide hydrocarbon supply window, and multivariate migration pathway promotes the accumulation in double-layered buried hill, and the well-connected cavity-fractured system provides sufficient space for hydrocarbon migration and accumulation inside the buried hill. In conclusion, oil and gas discovery in Bozhong 13-2 double-layered buried hill confirms the validity of exploration in non-sedimentary buried hill dominated by fractured reservoirs, which has great significance to buried hill exploration in China sea area.

In January 2021, Well Taiye 1, the first shale oil and gas exploratory well targeting at the Jurassic Lianggaoshan Formation,
was deployed in the Bashansi Syncline in the northern part of Fuling area in the Sichuan Basin, and obtained oil and gas flow rate of 9.8 m3/d and 7.5×104 m3/d respectively, by multi-staged fracturing and testing of the horizontal section, indicating a major breakthrough in lacustrine shale oil and gas exploration. Based on drilling results of Well Taiye 1, hydrocarbon accumulation
conditions and enrichment rules of lacustrine shale oil and gas in the Jurassic Lianggaoshan Formation were analyzed in detail.
Results indicate that the producing layer in Well Taiye 1 is organic rich shale in the 2nd member of Lianggaoshan Formation
(Liang 2 member) developed in semi-deep lake facies. In this layer, the 4th sub-layer is about 25.20 m in thickness, with the average TOC greater than 1.5%, organic matter type predominated by Type II, Ro ranging from 1.01%?1.41%, gas content of 1.81 m3/t, and an average porosity of 3.52%. Inorganic pores are dominant (clay mineral interlayer pores, intergranular pores, intragranular pores, etc.), and organic pores are developed locally, with pore diameter mainly of mesopores (2?50 nm) and macropores(>50 nm). Compared with other thin layers, the 4th sub-layer has the largest continuous thickness, the highest TOC, porosity, and gas content, representing a self-generation and self-storage shale oil and gas reservoir of “pure shale type”. The high-quality semi-deep lacustrine shale are widely developed in the northern part of Fuling area, which is favorable for shale oil and gas enrichment.The area with good preservation conditions, high formation pressure, and well-developed micro-fractures are conducive to the high production of shale oil and gas. Key technology of volume fracturing with characteristics of “few stages and multi cluster + temporary plugging and diversion + high pumping rate + medium to coarse sand proppants and high intensity sand injection” has been researched and developed, which enables effective stimulation on lacustrine shale. In conclusion, breakthrough of Well Taiye 1 is of great significance to the commercial development of lacustrine shale oil and gas in China.

Ordovician marine shale gas in the Ordos Basin has its unique geological characteristics. Proper evaluation of hydrocarbon
generation and storage capacities of shale, and accurate prediction of sweet spot distribution will provide guidance for marine
shale gas exploration in the Ordos Basin. Study of sedimentary paleo-bottom shape and tectonic-sedimentary evolution has
been carried out, which indicates that the sedimentary framework of Wulalike Formation in the western Ordos Basin is characterized by “local low-lying areas on the slope, deep water environment in the west and shallow in the east” with a sedimentary system of deep-water slope—open marine shelf—basin. A set of thick and widely distributed source rocks is developed in Wulalike Formation with the characteristics of “low TOC, low gas content, low porosity, low pressure, high maturity, high brittleness, high permeability and great burial depth”. Although the organic carbon content is low, it can effectively generate hydrocarbons and enrich locally, which is different from the high-abundance shale gas in the Sichuan Basin. Integrated logging and geological research have developed a technology of neutron-resistivity composite index for sweet spot prediction specially for marine shale gas in the western Ordos Basin. The sweet spot interval is at the bottom of Wulalike Formation with a thickness of 3-5 m and four sweet spot areas have been identified in the central-north section of western Ordos Basin. At the same time, gas enhanced energy fracturing test has been conducted to increase formation pressure and solve the problem of “low pressure and low abundance”,achieving breakthrough in marine shale gas exploration, which has great significance for the replacement of natural gas exploration in the Ordos Basin.

In recent years, Chinese government has relaxed restrictions on oil and gas exploration and production, and implemented
more stringent relinquishment strategy for exploration blocks. Competitive transfers have been promoted, and diversified
market participants cultivated. State-owned oil companies have faced greater pressure from external competition and internal reforms.Therefore, a comprehensive understanding of the reform trend, and a profound dissection of current problems and challenges are of great significance for the state-owned oil companies on their reform and management, giving full play to their own advantages and achieving high-quality development. Based on systematic summary of the history of oil and gas resource management in China since its establishment, and clarification of reform direction, this paper discusses in detail that PetroChina actively adapts to the reform, innovates management practice, and develops six mechanisms including linkage between reserves and deployment, internally dynamic allocation of mining rights and reserves, evaluation of new areas and competitive acquisition of new blocks, benefit reserve growth, reserve value evaluation, and foreign cooperation. Based on the practice of state-owned oil
companies, this paper also proposes five suggestions for areas reduction of mining rights, i.e., highlight on the principle of encouraging exploration and discovery, optimization of the location and limit of the transfer block, improvement of the dynamic
management of reserves and integrated management of exploration and development, establishment of market service system for
oil and gas reserves, and institutional arrangements for state-owned oil companies, in order to better support the development of
domestic oil and gas business and ensure the national energy security.

Seismic geophones are sensors collecting earth vibration signals. It is one of the key instruments for oil and gas seismic
exploration, which directly relates to the quality of seismic data. Due to the limitations of equipment manufacturing technology
and surface conditions, geophysists have been using multi-geophone arrays both in analog and digital seismic acquisition to
achieve high signal-to-noise ratio and continuous seismic events in structural exploration. However, as the oil and gas exploration
targets are shifted from structural to subtle targets such as stratigraphic-lithologic traps, carbonate rocks and tight oil and gas reservoirs,the fidelity and resolution of seismic data have become the research hotspots, in which selecting the appropriate geophone is an important link. Single point seismic acquisition technology has attracted much attention owing to its advantages in fidelity improvement, high resolution and imaging accuracy. However, this technology has not been widely applied due to the low signal-to-noise ratio and weak energy of raw data. Since 2010, PetroChina has carried out a series of pilot tests in plain, valley, desert,mountains and loess tableland using high sensitivity broadband single point geophone and improved coupling quality of geophones.In doing so, energy of single shot reaches the same level as that of traditional geophone array receiving, and the single
point receiving data record much more information, which shows obvious advantages in data processing, such as static correction,
resolution and imaging precision improvement. In addition, it evidently reduces labor intensity in the field. As a result, the single-
point geophone acquisition technology should be vigorously generalized as a key technology of high-resolution exploration.

As the main pathway of hydrocarbon migration, the fault-sandstone configuration transport system controls the distribution
of oil and gas reservoirs. In this paper, the dominant migration pathway of faults and the distribution of interconnected
sand bodies are depicted based on 3D seismic and well data, and the rule of oil and gas distribution of the 2nd and 3rd members of Dongying Formation (Ed2+3) in Liuchu area are studied. From the relationship between hydrocarbon transport system of
fault-sandstone configuration of Ed2+3 members and the underlying source rock of 1st member of Shahejie Formation (Es1), hydrocarbon transport capacity of fault-sandstone configuration and its relationship with oil and gas enrichment is studied combined with oil and gas distribution in Ed2+3 members. The result shows that a large number of sand bodies are developed on both sides of the faults of Ed2+3 members in Liuchu area, and only the proper configuration of faults and the interconnected sand bodies can form fault-sandstone transport system for hydrocarbon migration from source rock of Es1 member to reservoirs of Ed2+3 members.The fault-sandstone configuration with strong hydrocarbon transport capacity in Liuchu area is relatively developed, mainly distributed in the northern area, and followed by the fault-sandstone configuration with poor hydrocarbon transport capacity, which is mainly in the southeastern region. The fault-sandstone configuration with medium hydrocarbon transport capacity is the least developed and distributed in the middle, eastern and western regions.

In order to understand the provenance of Cretaceous Yageliemu Formation in the Yangta 11 well block, comprehensive
analysis is carried out by the petrology, cathodoluminescence mineralogy, and seismic attribute analysis techniques. As a result,
the provenance direction is confirmed and sedimentary facies identified. Detail analysis of rock composition and cathodoluminescence (CL) characteristics of Cretaceous Yageliemu Formation in the Yangta 11 well block reveals that there are many granitic textures in lithics, the CL of quartz is mainly purple, and the CL of potash feldspar is mainly bright blue, which are consistent with the CL characteristics of metamorphic granite in Well Qiman 1, but different from those of metamorphic rock in Well Wencan 1 and basalt rock in Well Yingmai 35-1. It is concluded that the provenance of Yageliemu Formation in the Yangta 11 well block is the Proterozoic metamorphic granite from the Luntai Bulge in Tabei Uplift. According to the analysis of seismic attributes,it is further clarified the east-westward spatial distribution of sand body and braided river delta sedimentary facies in the
Yangta 11 well block.

Although the producing degree of proven geological reserves is generally high on the plane in the Yanchang oil region which is located in the southeastern part of Yishaan Slope, there are still nearly 270 million tons of geological reserves that have not been produced effectively. Stratigraphically, they are mainly in the oil layer groups of Chang 2 and Chang 6 members of the Triassic Yanchang Formation, accounting for 34.4% and 41.4% of the total amount, respectively. In order to reasonably and orderly
build production capacity and increase the producing rate of proven geological reserves, taking the proved undeveloped
geological reserves in the Yanchang oil region as study object, this paper analyzes the plane and vertical distribution, and the reasons for undeveloped geological reserves, identifies the distribution and volume of proven geological reserves with favorable
geological conditions, or allowed by environmental protection and surface conditions. Then strategies, producing procedures and
technical research directions for efficient producing of proved undeveloped geological reserves are put forward. The results show
that the proved undeveloped geological reserves can be classified into three categories in the Yanchang oil region: recently
planned producing reserves, temporarily undevelopable reserves and long-term undevelopable reserves. Through classification
and adjustment of development strategies combined with further research, it is estimated that the newly increased proved developable geological reserves are 20237.59×104 t and the newly-built oil production capacity is (107?155)×104 t/a, which will make a positive contribution to coping with low oil price, realizing efficient oilfield development and maintaining long-term stable production.

During the deposition period of Zhujiang and Zhuhai Formations in Huizhou Sag of the Pearl River Mouth Basin, several types of low-medium permeability sandstone reservoirs were developed in the target layer influenced by mother rock types and sedimentary environment. The pore structure, flow capacity and rock-electric properties are significantly different for different
types of reservoir. The traditional zoning and layered modeling methods have problems in application such as poor pertinence
of selected models and low interpretation accuracy. In order to improve the interpretation accuracy of reservoir parameters, this
paper starts with the reservoir classification by petrophysical facies. Based on core analysis data, parameters such as the average
grain size, mineral content, porosity, permeability and pore structure are optimally selected to characterize reservoir petrophysical
properties. The reservoir is accordingly classified into four petrophysical facies: feldspar quartz medium-fine sandstone facies,
clayey feldspar quartz fine sandstone facies, clayey feldspar quartz siltstone facies and calcareous quartz medium-fine sandstone
facies. Furthermore, sensitive log curves are extracted according to logging response characteristics of different petrophysical facies,and logging identification criteria for different types of petrophysical facies are established using the discriminant analysis
method. On this basis, fine interpretation model of reservoir parameters for each type of petrophysical facies is established and
calibrated by experimental data. The practical application results show that the accuracy of calculated porosity, permeability and
water saturation using petrophysical facies classification is significantly improved compared with the traditional method, which
meets the requirements of reserves calculation, and the logging interpretation conclusion is in good agreement with DST test result for new wells.

Well group platform has become a popular way of shale gas development. Relying on scientific research and field test,
shale gas resources with burial depth shallow than 3500 m have been commercially developed in a large scale in the southern Sichuan Basin. In order to improve the overall benefit, a series of development technology strategy adjustments have been implemented,such as shortening the well spacing, increasing the intensity of stimulation, etc., during which frac hits occurred frequently.The pressure conduction model for synchronous operation of fracturing and production on the same platform is established,and the factors affecting frac hit are clarified, including (1) natural fracture development; (2) well spacing; (3) cluster
spacing; (4) fracturing operation parameters; (5) hydraulic fracture geometry. Based on the development concept of integrated geology and engineering, this paper puts forward technical measures for prevention and control the frac hit, which has achieved remarkable results. This will provide support for the further deep research and the strategic adjustment of development technology.

Artificial intelligence technology has been used in well logging interpretation for a long time, but there are more researches
on single model interpretation and less on application of system integration. Nowadays, large-scale application of cloud
computing, big data and artificial intelligence technology has promoted the intelligent development of logging interpretation once
again. Based on the data lake of multidisciplinary data fusion, intelligent interpretation module is developed in the logging interpretation software. That is, the intelligent logging interpretation method is introduced into the traditional interpretation process to assist logging analysts to quickly mine the hidden high-value information. Big data governance tools are used to connect data lake to intelligent model, so that big data and intelligent algorithm are integrated. The system integrates intelligent interpretation model based on big data with traditional professional software and builds an intelligent logging interpretation environment based on geological map navigation, realizing intelligent logging interpretation working mode with integration of geology and reservoir,strengthening the ability of complex reservoir evaluation, and improving the working efficiency.

Lost circulation brings great challenges to petroleum engineering. Bozhong 34-9 Oilfield has experienced high frequency
and large-scale lost circulation in fractured formation, which seriously reduced development progress and increased operation
cost. In this paper, the characteristics, types of leakage channel, causation and dynamics of lost circulation in Bozhong
34-9 Oilfield are studied, and the mechanisms of lost circulation in fractured formation analyzed. The result shows that the existence of weak plane texture inevitably leads to lost circulation and the positive pressure differential is the main driving force of
well leakage. On the whole, lost circulation is the rebalance of wellbore pressure-stress-strain in the process of over-balanced
drilling operation. In addition, supporting measures for preventing lost circulation are proposed. Practice indicates that one of the
effective measures in fractured formation is to control the bottom hole pressure differential. Formation with weak plane texture
should be regarded as a heterogeneous geological model, and well structure, drilling fluid and other drilling parameters be optimized and constrained by pressure bearing strength and stress sensitivity of the weak plane, to avoid and prevent well leakage in advance.