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Abstract Background Tumor regression grade (TRG) is a measure of histopathological response to neoadjuvant therapy (NAT). Post‐therapy lymph node (ypN) metastasis was reported as a prognostic factor. However, the evaluation of the treatment effectiveness of NAT has not been well studied. Here, we explored whether TRG combined with ypN status could be a prognostic factor for gastroesophageal junction (GEJ) and gastric cancer (GC). Besides, we aimed at making clear the association of different neoadjuvant regimens with different TRG and ypN status. Methods 376 patients with GEJ or GC accepting NAT in Peking University Cancer Hospital were retrospectively collected from January 1, 2003 to June 30, 2021. According to TRG and ypN status, patients were innovatively categorized into four groups: TRG0N0, TRG1‐3N0, TRG0‐1N+, and TRG2‐3N+. We applied Kaplan–Meier method and log‐rank test to testify the differences in disease free survival (DFS) and overall survival (OS) among four groups. Univariate and multivariate analyses were performed to examine the relationships between TRG combined with ypN status and prognosis. Results We observed significant survival differences among the four groups (p

According to the theory of sequence stratigraphy based on continental transgressive-regressive (T-R) cycles, a 500 m continuous core taken from the second member of Kongdian Formation (Kong 2 Member) of Paleogene in Well G108-8 in the Cangdong Sag, Bohai Bay Basin, was tested and analyzed to clarify the high-frequency cycles of deep-water fine-grained sedimentary rocks in lacustrine basins. A logging vectorgraph in red pattern was plotted, and then a sequence stratigraphic framework with five-order high-frequency cycles was formed for the fine-grained sedimentary rocks in the Kong 2 Member. The high-frequency cycles of fine-grained sedimentary rocks were characterized by using different methods and at different scales. It is found that the fifth-order T cycles record a high content of terrigenous clastic minerals, a low paleosalinity, a relatively humid paleoclimate and a high density of laminae, while the fifth-order R cycles display a high content of carbonate minerals, a high paleosalinity, a dry paleoclimate and a low density of laminae. The changes in high-frequency cycles controlled the abundance and type of organic matter. The T cycles exhibit relatively high TOC and abundant endogenous organic matters in water in addition to terrigenous organic matters, implying a high primary productivity of lake for the generation and enrichment of shale oil.

The Banqiao area in the Bohai Bay Basin has experienced three stages of extensional deformation, leading to the formation of numerous fault-bound traps. Faults, acting as boundary conditions for these traps, play a crucial role in hydrocarbon accumulation. In this study, we conducted a 3D structural modeling of the area using high-resolution 3D seismic data and established a fault-reservoir database based on previous research. Our findings reveal four levels of faults in the Banqiao area: basin-controlling faults, boundary faults, derivative master faults, and secondary adjusting faults. The structural units can be categorized into subsag areas, slope areas, stress tran-sition zones, bifurcation and main incised fault zones, and southern block areas. The segmented growth of the main boundary faults controls the evolution of the subsags, with the subsidence center gradually shifting eastward from Rift Phase I to Rift Phase II, aligning with the distribution of source rocks. Fault-bound traps in the Banqiao area include single faults, intersecting faults, and side faults. Faults primarily act as barriers to lateral hydrocarbon migration during the process of hydrocarbon accumulation, while also providing pathways to a lesser extent. By integrating the fault-reservoir database with the fault system classification, we identified four types of fault-controlled hydro-carbon accumulation models: like-dipping fault barrier model, oppositely-dipping fault barrier model, intersecting fault barrier model, and reactivation-controlled secondary hydrocarbon ac-cumulation model. This structural geological model effectively demonstrates the spatial configura-tion of faults and their role in hydrocarbon accumulation in the Banqiao area. The fault control mechanisms presented in the model can also be applied to other blocks in the Bohai Bay Basin, laying a foundation for future petroleum exploration in continental rifted basins and facilitating the ap-plication of big data algorithms in various geoscientific research fields.

Dioctyl phthalate, commonly known as bis(2-ethylhexyl) phthalate (DEHP), is a widely used plasticizer in various industries and has been shown to directly or indirectly impact human health. However, there is a lack of comprehensive studies evaluating the potential health risks associated with DEHP accumulation in different organs across various age groups. This study aimed to assess the effects of low (50 mg/kg·bw) and high (500 mg/kg·bw) doses of DEHP on five different organs in mice at young (4-week-old) and aged (76-week-old) life stages. Our findings revealed that both low and high doses of DEHP exposure led to significant dose-dependent inflammation in the liver, spleen, and kidney. Furthermore, regardless of age, DEHP exposure resulted in elevated activity of alanine aminotransferase (ALT) and alkaline phosphatase (ALP) in the liver, as well as increased levels of creatinine (Cr) and urea in the kidney. Moreover, analysis of the fecal microbiota using 16S rRNA sequencing demonstrated that DEHP exposure disrupted the homeostasis of the gut microbiota, characterized by an increased abundance of pathogenic bacteria such as Desulfovibrio and Muribaculum, and a decreased abundance of beneficial bacteria like Lactobacillus. This study provides compelling evidence that DEHP at different concentrations can induce damage to multiple organs and disrupt gut microbiota composition. These findings lay the groundwork for further investigations into DEHP toxicity in various human organs, contributing to a better understanding of the potential health risks associated with DEHP exposure.

As the main factors affecting stable and high production and the production regularity of lacustrine shale oil are unclear, the theoretical understandings, key exploration and development technologies, development effect and production regularity of lacustrine shale oil have been analyzed and summarized based on 700 m cores taken systematically from Paleogene Kong 2 Member of 4 wells in Cangdong sag, over 100 000 analysis data and formation testing data. Three theoretical understandings on shale oil enrichment and high production have been reached: (1) High-quality shale with “three highs and one low” is the material base for shale oil enrichment. (2) Medium—slightly high thermal evolution degree is the favorable condition for shale oil enrichment. (3) Laminar felsic shale is the optimal shale layer for oil enrichment in semi-deep lake facies. Key exploration and development technologies such as shale oil enrichment layer and area evaluation and prediction, horizontal well pattern layout, shale oil reservoir fracturing, optimization of shale oil production regime have been established to support high and stable shale oil production. Under the guidance of these theoretical understandings and technologies, shale oil in Cangdong sag has achieved high and stable production, and 4 of them had the highest production of over 100 tons a day during formation testing. In particular, Well GY5-1-1L had a daily oil production of 208 m3. By April, 2022, the 28 wells combined have a stable oil production of 300–350 tons a day, and have produced 17.8×104 t of oil cumulatively. It is found that the shale oil production of horizontal well declines exponentially in natural flow stage, and declines in step pattern and then tends stable in the artificial lift stage. Proportion of light hydrocarbons in produced shale oil is in positive correlation with daily oil production and decreases regularly during production test.

A negative tectonic area refers to the relatively lower tectonic area from slope to deep depression in a basin. The theoretical understanding of oil and gas accumulation in the negative tectonic area is based on three accumulation models of "lithologic and stratigraphic reservoirs in the area of sag, lacustrine shale oil in deep depression, and coalbed methane in syncline area". Integrating with previous studies on reservoirs in negative tectonic area, a systematic knowledge system of oil and gas accumulation mechanisms and distribution laws in negative tectonic areas has been formed. The key points are as follows: (1) From the center to the margin of basin, oil and gas reservoirs are distributed in a circular order in the transverse direction, and enrich radially along dominant petroleum migration pathways in the longitudinal direction. (2) Due to different tectonic backgrounds, the sedimentary characteristics, hydrocarbon accumulation conditions, accumulation mechanism and distribution laws of negative tectonic area are greatly different from those of the positive tectonic area. (3) In deep depression and low slope, in situ hydrocarbon accumulation is dominant, and unconventional oil and gas distribution ring (inner ring) is formed. On medium and high slopes, passing oil and gas are captured, and lithologic and stratigraphic oil and gas distribution ring (central ring) is formed. While in positive tectonic area, oil and gas accumulate in high locations, and tectonic oil and gas distribution ring (outer ring) is developed. (4) An exploration idea based on the theory of oil and gas accumulation in negative tectonic area was proposed as follows. The target area should be integrately considered and exploration should be carried out from ring to ring. Migration pathways must be reguarded as a clue to seize oil and gas targets. The theory of oil and gas accumulation in negative tectonic area has effectively guided the discovery of a large number of subtle and unconventional oil and gas reservoirs in the slopes and deep sags of Jizhong and Huanghua depressions, and enriched the modern theory of oil and gas accumulation. It has an important practical guiding value for the exploration of deep complex subtle reservoirs and unconventional reservoirs in the negative tectonic area of basins.

To evaluate the lateral sealing mechanism of extensional fault based on the pressure difference between fault and reservoir, an integral mathematical-geological model of diagenetic time on diagenetic pressure considering the influence of diagenetic time on the diagenetic pressure and diagenetic degree of fault rock has been established to quantitatively calculate the lateral sealing ability of extensional fault. By calculating the time integral of the vertical stress and horizontal in-situ stress on the fault rock and surrounding rock, the burial depth of the surrounding rock with the same clay content and diagenesis degree as the target fault rock was worked out. In combination with the statistical correlation of clay content, burial depth and displacement pressure of rock in the study area, the displacement pressure of target fault rock was calculated quantitatively. The calculated displacement pressure was compared with that of the target reservoir to quantitatively evaluate lateral sealing state and ability of the extensional fault. The method presented in this work was used to evaluate the sealing of F1, F2 and F3 faults in No.1 structure of Nanpu Sag, and the results were compared with those from fault-reservoir displacement pressure differential methods without considering the diagenetic time and simple considering the diagenetic time. It is found that the results calculated by the integral mathematical-geological model are the closest to the actual underground situation, the errors between the hydrocarbon column height predicted by this method and the actual column height were 0–8 m only, proving that this model is more feasible and credible.

In order to study the distribution law of oil and gas above and below the regional mudstone caprocks damaged by fault in petroliferous basins, based on the study of the sealing mechanism and degree of regional mudstone caprocks damaged by fault during the hydrocarbon accumulation period, the paleo-juxtaposition thickness of regional mudstone caprock was calculated by determining the paleo-fault throw of faults and the paleo-thickness of regional mudstone caprocks during the hydrocarbon accumulation period. According to the relation between the paleo-juxtaposition thickness of regional mudstone caprocks at known well points in the study area and the distribution of oil and gas above and below the regional mudstone caprock, the maximum juxtaposition thickness required for the upper and lower connection of the fault-associated fracture zone in the regional mudstone caprock was determined. On this basis, a set of prediction methods for the sealing capacity of regional mudstone caprocks damaged by fault during the hydrocarbon accumulation period was established. Then, this method was applied to the prediction of the damage degree distribution of the Zhangdong Fault to the regional mudstone caprock of the middle sub-member of the first member of the Shahejie Formation in the middle and late depositional periods of the Minghuazhen Formations in Qikou Sag of the Bohai Bay Basin during the hydrocarbon accumulation period. The results show that the damage degree of the Zhangdong Fault to the regional mudstone caprock of the middle sub-member of the first member of the Shahejie Formation during the hydrocarbon accumulation period is large. The largest damage appears in the east, with an a-value greater than 1, followed by the west, with an a-value between 0.5 and 1. The relatively minor damage occurs in the middle west part, with an a-value less than 0.5. The middle part is conducive to the accumulation and preservation of oil and gas generated from the source rock of the underlying third member of the Shahejie Formation, which is consistent with the fact that oil and gas discovered in the lower sub-member of the first member of the Shahejie Formation near the Zhangdong Fault are mainly distributed in its middle part. It shows that this method is feasible to predict the damage degree distribution of regional mudstone caprocks during the hydrocarbon accumulation period.

Compared with marine facies shale strata, lacustrine shale strata are more complicated in geological conditions, and thus more difficult to explore and develop. To realize economic exploration and development of lacustrine shale oil, the geological regularities of accumulation and high yield of retained movable petroleum in shale should be understood first. In this work, taking the shale strata of Kong 2 Member and Sha 3 Member in the Paleogene of Huanghua depression in the Bohai Bay Basin as examples, based on the previous joint analysis results of over ten thousand core samples and the latest oil testing, production test and geochemical data of more than 30 horizontal wells, accumulation conditions and models of retained movable petroleum in lacustrine shale were studied comprehensively. The study shows that at moderate organic matter abundance (with TOC from 2% to 4%), shale strata have the best match between oil content and brittleness, and thus are rich in oil and good in fracability. Moderate ancient lake basin size and moderate sediment supply intensity are the internal factors leading to best coupling of organic matter abundance and brittle mineral content in the shale formation. Moderate thermal evolution maturity of Ro of 0.7%–1.0% (at burial depth of 3200 to 4300 m) is the interval where oil generation from thermal evolution and oil adsorption by kerogen in shale layers match best, and retained movable petroleum is high in proportion. Moderate diagenetic evolution stage (3200 to 4300 m in the middle diagenetic stage A) is conducive to the formation of a large number of dissolved pores and organic matter pores, which provide storage space for shale oil enrichment. Moderate development degree of natural fractures (without damaging the shale oil roof and floor sealing conditions) is conducive to the storage, seepage and preservation of shale oil. The research results have overthrown the general understanding that high organic matter abundance, high maturity, and high development degree of natural fractures are conducive to shale oil enrichment, and have guided the comprehensive evaluation of shale oil and gas sweet spots and well deployment in the second member of the Kongdian Formation in the Cangdong sag and the Shahejie Formation in the Qikou sag. Industrial development of the shale oil in Kong 2 Member of the Cangdong sag has made major breakthrough, and important signs of shale oil have been found in Sha 3 Member of the Qikou sag, demonstrating huge exploration potential of lacustrine shale oil.

Based on detailed core description and systematic joint test data, enrichment laws of continental shale oil have been examined deeply. Key technologies such as the identification and quantitative evaluation method for sweet spot, precise design and tracking of horizontal well trajectory, and the low-cost horizontal well volume fracturing technology of the whole process “slick water + quartz sand” for continental shale oil have been formed. The research results show that the enrichment of pure continental shale oil of the Paleogene Kong 2 Member in Cangdong Sag is controlled by predominant fabric facies and cross-over effect of retained hydrocarbons jointly; and there are four modes of shale oil enrichment, i.e. laminar felsic, laminar mixed, thin-layer limy dolomitic, and thick-layer limy dolomitic shales. The identification and evaluation method for shale oil sweet spots can predict sweet spots accurately. The precise trajectory design for sweet spot layer and tracking-trajectory optimization while drilling by considering geological and engineering factors have been proved effective by field application, with drilling rate of sweet spots reaching 100% and drilling rate of type I sweet spots reaching over 75%. The whole process “slick water + quartz sand” low cost volume fracturing has been proved effective in creating multi-stage fracture network in the horizontal section, and improved productivity greatly. It can lower the comprehensive engineering cost by 26.4%.

High-yielding oil wells were recently found in the first member of Paleogene Shahejie Formation, the Binhai area of Qikou Sag, providing an example of medium- and deep-buried high-quality reservoirs in the central part of a faulted lacustrine basin. By using data of cores, cast thin sections, scanning electron microscope and physical property tests, the sedimentary facies, physical properties and main control factors of the high-quality reservoirs were analyzed. The reservoirs are identified as deposits of slump-type sub-lacustrine fans, which are marked by muddy fragments, slump deformation structure and Bouma sequences in sandstones. They present mostly medium porosity and low permeability, and slightly medium porosity and high permeability. They have primary intergranular pores, intergranular and intragranular dissolution pores in feldspar and detritus grains, and structural microcracks as storage space. The main factors controlling the high quality reservoirs are as follows: (1) Favorable sedimentary microfacies of main and proximal distributary gravity flow channels. The microfacies with coarse sediment were dominated by transportation and deposition of sandy debris flow, and the effect of deposition on reservoir properties decreases with the increase of depth. (2) Medium texture maturity. It is shown by medium-sorted sandstones that were formed by beach bar sediment collapsing and redepositing, and was good for the formation of the primary intergranular pores. (3) High content of intermediate-acid volcanic rock detritus. The reservoir sandstone has high content of detritus of various components, especially intermediate-acid volcanic rock detritus, which is good for the formation of dissolution pores. (4) Organic acid corrosion. It was attributed to hydrocarbon maturity during mesodiagenetic A substage. (5) Early-forming and long lasting overpressure. A large-scale overpressure compartment was caused by under-compaction and hydrocarbon generation pressurization related to thick deep-lacustrine mudstone, and is responsible for the preservation of abundant primary pores. (6) Regional transtensional tectonic action. It resulted in the structural microcracks.

As the hydrocarbon vertical migration pathway, fault and its relationship with reservoir extremely affect the distribution and accumulation of oil and gas in the non-hydrocarbon generating layers. On both sides of the fault, there are frequently various sand bodies with different oil and gas enrichment. However, previous researches on this differential charging are mostly based on empirical formulas or physical simulation experiments instead of fluid seepage mechanism. This paper proposed a quantitative evaluation method on the basis of Darcy's law to analyze the difference in hydrocarbon lateral diversion capacity through the oil-source fault. It can be seen that in the process of hydrocarbon migrate along the oil-source fault, hydrocarbons could divert laterally into sand bodies through the fault when there is a downward pressure gradient. Conversely, hydrocarbons can only migrate upward along the fault. Furthermore, among the four normal fault-sand body configuration types, the opposite fastigium type is most favorable for hydrocarbons laterally charging whereas the fastigium type is the least beneficial. The ratio of resistance in the sand body to in the fault was proposed as the evaluation index ( F s ) to quantitatively evaluate the hydrocarbon lateral diversion migration capacity, on the assumption that hydrocarbons in different sand bodies are sourced from the same source rocks. The index ( F s ) is directly proportional to the lateral diversion capacity of hydrocarbon, and is complex controlled by many geological factors including the reservoir permeability, fault-sand body contact length and dip angles of sand body and fault. And the higher the value of F s, the stronger the hydrocarbons laterally divert ability of the sand body. In addition, the calculation result of well GG16102 in the Beidagang buried hill coincide well with the oil and gas interpretation result indicating that the method is practical to quantitatively evaluate the laterally diverting hydrocarbons of sand bodies under the condition of fault-sandstone configuration.

Accurate identification of land use conflicts is an important prerequisite for the rational allocation of land resources and optimizing the production–living–ecological space pattern. Previous studies used suitability assessment and landscape pattern indices to identify land use conflicts. However, research on land use conflict identification from the perspective of ecological security is insufficient and not conducive to regional ecological, environmental protection, and sustainable development. Based on ecological security, this study takes Shandong Province as an example and comprehensively evaluates the importance of ecosystem service function and environmental sensitivity. It identifies the ecological source, and extracts ecological corridors with a minimum cumulative resistance model from which ecological security patterns are constructed. It identifies land use conflicts through spatial overlay analysis of arable land and construction land. The results show that: (1) Shandong Province has formed an ecological security pattern of “two ecological barriers, two belts, and eight cores” with an area of 15,987 km2. (2) The level of arable land–ecological space conflict is low, at 39.76%. The proportions of serious and moderate conflicts are 13.44% and 26.97%, respectively, distributed primarily on the Jiaodong Peninsula and the low hill areas of Ludong. (3) Construction land–ecological space conflict is reasonably stable and controllable, at 76.39%, occurring mainly around urban construction land, with serious and moderate conflict concentrated in the eastern coastal areas, mainly between rural settlements and ecologically safe space in the region. This study has important theoretical and practical reference values for identifying land use conflicts, protecting regional ecological security, and optimizing land use patterns.

In recent years, several wells in the Qibei and Wumaying buried hills of Dagang Oilfield tapped oil in the Carboniferous–Permian and Ordovician strata. This major breakthrough reveals that the deep Paleozoic in the Bohai Bay is a new petroleum system. Through re-evaluating the Paleozoic source rock, reservoir-cap combinations and traps, it is found the oil and gas mainly come from Carboniferous–Permian source rock. The study shows that the Paleozoic strata are well preserved in the central-south Huanghua Depression and developed two kinds of reservoirs, Upper Paleozoic clastic rock and Lower Paleozoic carbonate rock, which form favorable source-reservoir assemblages with Carboniferous–Permian coal measure source rock. The Carboniferous–Permian coal-bearing source rock is rich in organic matters, which are mainly composed of type II2 and III kerogens, and minor II1 kerogen in partial areas. Multi-stage tectonic movements resulted in two stages of hydrocarbon generation of the source rocks. The period from the deposition of Kongdian Formation to now is the second stage of hydrocarbon generation. The matching between large-scale oil and gas charging, favorable reservoir-cap combinations and stable structure determines the enrichment of oil and gas. According to the new comprehensive evaluation of Paleozoic petroleum system, the primary oil and gas resources of the Paleozoic in the Bohai Bay Basin are over 1×1012 m3. The exploration breakthrough in Paleozoic petroleum system, especially Carboniferous–Permian petroleum system in Huanghua Depression is inspirational for oil and gas exploration in similar provinces of Bohai Bay Basin. Key words: Paleozoic, primary oil reservoirs, secondary hydrocarbon generation, oil and gas source, Huanghua Depression, Bohai Bay Basin

Under the general trend of stepping-up oil and gas exploration and development in China, the unconventional oil and gas resources such as shale oil and gas have become an important alternative. Abundant continental shale oil resources are developed in Member 2 of Kongdian Formation (Ek2) of the Cangdong sag in the Huanghua depression of the Bohai Bay Basin which has complex structure, strong heterogeneity, and large buried depth, thus, the geological characteristic of shale oil accumulation and key exploration technologies are investigated on base of the system coring of 635.8 m, centimeter-level fine description and analysis of over ten thousand samples, therefore, the “four accurate” technologies have been developed, including the accurate selection of sweet spot areas, accurate drilling of sweet spot layers, accurate fracturing of sweet spot layers and accurate measure of fracture-rich sections. The results show that the continental shale strata in Member 2 of Kongdian Formation can be divided into three types: felsic shale, limy dolomitic shale and mixed shale. The Member 2 of Kongdian Formation is characterized by diverse mineral components, abundant laminae, good source rocks and medium thermal evolution degree, tight reservoir with rich micropore and microfractures, high oil saturation and brittle mineral content, indicating good prospect of shale oil exploration. Through sedimentological study, TOC and Ro evaluation, brittle mineral calculation, and seismic fusion inversion, a total of 126 km2 of Class I sweet spots in Member 2 of Kongdian Formation was delineated comprehensively, which guides horizontal well deployment (Well GD1701H and Well GD1702H). The drilling rate of sweet spot of these two horizontal wells is up to 96% by tracing thin layer through fine calibration, locating compartment through fine inversion, ensuring window entry through precise positioning, and tracking sweet spot through adjustment. The ''one-excellent and five-highs” criterion is used to select perforation points to realize differential designs of fracturing intervals and clusters. Micro-seismic and potentiometry monitoring show that the artificial fractures formed by volumetric fracturing are 300–400 m long and 120 m high, and control a volume of about 0.07 km3. The maximum daily oil production of two horizontal wells is 48 t and 66 t respectively to realize the economic exploitation of shale oil reserves controlled by fractures. The shale oil exploration in Member 2 of Kongdian Formation shows that the continental shale oil has great potential of exploration and development, and the above technologies are critical and effective for shale oil efficient recovery. Keywords: Shale oil, Sweet spot evaluation, Fracturing intervals and perforation clusters, Member 2 of Kongdian formation, Cangdong sag, Bohai Bay Basin

Summary: Infectious endophthalmitis is a growing concern that causes irreversible intraocular tissue and optic nerve damage. Here, we report a theranostic nanoplatform based on UiO-66-NH2 to combine photodynamic therapy (PDT) and lipopolysaccharide (LPS) targeting through polypeptide (YVLWKRKRKFCFI-NH2) modification. Toluidine blue (TB), serving as a photosensitizer (PS), is loaded into UiO-66-NH2 nanoparticles (NPs) for both self-imaging and PDT functions. The accelerated TB release at pH 5.5 compared to pH 7.4 demonstrates the responsive drug release feature. In vitro antibacterial tests, including contact incubation-agar plate counting, bacterial live/dead staining, and scanning electron microscopy observations, confirm the utility of the TB@UiO-66-NH2@PEP&PEG NPs (UTPP NPs) in biofilms removal and sterilization of Pseudomonas aeruginosa and Staphylococcus epidermidis. Furthermore, the UTPP NPs also show good biocompatibility toward human retinal pigment epithelial cells, as well as in situ self-imaging property. Finally, an in vivo infectious endophthalmitis model supports the application of the UTPP NPs in infectious endophthalmitis treatment.

Based on the merged 3D seismic data, well logging, formation testing, analysis and testing data, the structural evolution, sedimentary reservoirs, thermal evolution of source rocks were investigated of Paleogene Kongdian Formation in the trough area of Cangdong sag, Bohai Bay Basin. A conventional-unconventional hydrocarbon accumulation pattern in the trough area of rifted basin was revealed. The reservoir forming elements in the trough area of Cangdong sag have a zonation feature in terms of reservoirs and source rocks. There are two types of reservoir forming models, primary trough and reformed trough. The formation and evolution of trough controlled the orderly distribution of conventional oil to unconventional oil in the trough. Particularly, structural reservoirs occur in the upper part of the trough, stratigraphic-lithologic reservoirs are likely to form in the delta front deposits at the outer ring of trough, the middle ring transitional belt is the favorable site for tight oil reservoirs, while the fine grain deposits zone in the inner ring is shale oil and gas exploration area. The study has pointed out the new domains and directions for searching reserves in the secondary exploration of mature oilfields. Key words: rifted basin, trough hydrocarbon accumulation, stratigraphic-lithologic reservoir, shale oil, orderly accumulation, Bohai Bay Basin, Cangdong sag, Paleogene Kongdian Formation

It is an important research direction for the prediction of hydrocarbon phase in the reservoir during the deep exploration of rift basins in eastern China. The typical lacustrine crude oil of Shahejie Formation in Qikou Sag was used for oil cracking to gas simulation experiment by the gold tube in this paper. Then, the kinetic parameters obtained from the experimental data were studied during the cracking reactions and the hydrocarbon phase conversion process under geological conditions. The results showed that the activation energy of the oil cracking to gas from the BH-28 lacustrine crude oil ranged from 250 kJ/mol to 270 kJ/mol with an average of EO = 255.47 kJ/mol, and the frequency factor was about A = 1014 s−1. It is higher than that of typical marine oil EO = 246.97 kJ/mol. Using these kinetic parameters, the simulated cracking process of the lacustrine oil of Shahejie Formation was far different from that of marine oil from western China under the same geological heating rate (3 °C/Ma). And the simulated oil cracking degree in Well Niudong-1 is 73.9%, almost the same with the conversion cracking degree (60%–75%) by concentrations of 3,4-dimethyldiamantane. The kinetics of oil cracking gas could be used to investigate the oil cracking degree easily, then to get the theoretical separate oil phase depth limit. By using this model, oil in Qikou Sag, as a theoretical separate phase destruction, occurs above 5700 m depth limit (RO is about 2.0%, reservoir temperature = 209 °C, with cracking transition C of 62.5%), and condensate gas destruction occurs above 6700 m depth limit (RO is about 3.2%, reservoir temperature = 240 °C, with C to 99%) under the geological conditions from Qikou Sag. Actually, the hydrocarbon phase is affected by many factors. For example, migration and changes of temperature and pressure conditions have great influence on phase conversion behavior. The injection of gas, originated from kerogen cracking gas and oil cracking gas in deeper, could increase GOR and the real separate phase depth would reduce.

The fault-reservoir displacement pressure differential method, as a quantitative evaluation method of fault sealing which considering diagenetic time of fault rock, was improved based on the study of fault sealing mechanism and its influencing factors. A geology and mathematical model of quantitative evaluation of fault sealing considering diagenetic time was established. First, the depth of surrounding rock which has the same shale content and diagenetic degree as the fault rocks at the target was determined using the method of successive approximation at the given step length. Second, the displacement pressure of target fault rocks was calculated based on the relationship between the displacement pressure and the product of shale content and burial depth that was established for the study area. And third, the sealing states and capacity of the faults were quantitatively evaluated by comparing the calculated displacement pressure with that of the target reservoir. By the actual data of reservoirs at Banqiao Fault in Qikou sag and the result comparison between fault rock shale content method (SGR) and fault-reservoir displacement pressure differential method without considering the diagenetic time, it is verified that this method is more feasible and credible. Key words: Qikou Sag, fault rock, lateral sealing ability, sealing ability quantitative evaluation, displacement pressure

Based on observation of cores and thin slices and analysis of drilling, log and test data, the gravity flow deposits characteristics and formation conditions and characteristics of tight oil in lower first member of Shahejie Formation (Es1x) were systematically analyzed in Qikou Sag, Huanghua depression, Bohai Bay Basin. There mainly developed sandy debris flow, muddy debris flow and classical turbidity flow in the study area, and sandstone with boulder-clay is mostly sandy debris flow origin, muddy debris flow deposits are mudstone or silty mudstone with sandy lumps, the normal graded bedding is a reliable sign of classical turbidite. Affected by multi-source supply, slope break, different trigger mechanism and fluctuation of lake level, multi-gravity flows formed multi-level fans in mid-low slope to main sag, which can be divided into five micro-facies including submerged main channel, submerged distributary channel, lateral channel margin, mud between channels and turbidite sheet sand. Multi-level and multi-stage gravity flow sediments provide material foundations for tight oil and gas in the deep mud and sand-rich lake, where wide spread tight reservoirs and high quality source rocks contact closely vertically, forming multiple sets of sandwich-like source-reservoir-seal assemblages. Exploration shows that the submerged distributary channel and turbidite sheet sand of sandy debris flow are two main exploration facies of gravity flow in Es1x and important area of scale reserve increase in slope zones of Qikou Sag. Key words: gravity flow sedimentation, tight oil, Shahejie Formation, slope area, Qikou Sag, Bohai Bay Basin