Abstract  Based on the analyses of over 310 sandstone samples from 53 well, the Taizhou Formation reservoir in the Subei Basin experienced burial (pressolution) , cementation and dissolution process, while the diagenesis showed different characteristics at different locations. The Haian Sag located in eastern part of Subei Basin is dominated by cementation and dissolution, with nonobvious burial and pressolution. The burial extent in the Gaoyou Sag is stronger than that in the Haian Sag. The reservoir porosity of the Taizhou Formation in Gaoyou Sag was about 10% at depth of 2400～2800 m, while was about 10% ～20% in Haian Sag. Currently, the Taizhou Formation in the Haian Sag and Gaoyou Sag is at the age A of mid-diagenetic stage. The reservoir quality is mainly controlled by comprehensive influence of the initial sedimentary environment and diagenesis. Burial and cementation both can reduce the pore space, but when the carbonate cements content is lower than 15%, ementation has smaller influence on the reservoir quality. The carbonate cements and feldspar grains created a great deal of intergranular pores. The favorable reservoir in the Haian Sag in mainly distributed in the northwestern and eastern delta front sandbodies and turbidity fan sandbodies, while in the Gaoyou Sag, it is distributed in southern fan delta front sadnbodies.

Abstract  Based on the studies of reservoir diagenesis types and their characteristics of the Members 4 and 2 of Upper
 Triassic Xujiahe Formation in Xinchang Gasfield, it is concluded that the reservoir diagenesis mainly includes the pressolution, the authigenic mineral cementation and the dissolution. The diagenetic-reservoir facies is divided into 5 types, namely as, the intense dissolution diagenetic-reservoir facies, the chlorite lape intergranular pore diagenetic-reservoir facies, the pressolution diagenetic-reservoir facies, the carbonate cementation diagenetic-reservoir facies and the quartz secondary overgrowth diagenetic- reservoir facies. The formation conditione of the relic primary intergranular pores and secondary dissolution pores in the reservoirs are different due to tneir different diagenetic evolutionary sequences. The preservation of pores in reservoir is mainly controlled by the burial, compaction, filling of authegenic minerals and the multi-stages dissolution, as well as the chlorite laping developed in the pores. The effective diagenetic-reservoir facies in the 5 types are respectively the intense dissolution diagenetic-reservoir facies and chlorite lape intergranular pore diagenetic-reservoir facies. They play an important role in the formation of the reservoir of Members 4 and Member 2 of Xujiahe Formation , while the other diagenetic facies are ineffective for the high quality reservoir formation.

Based on the theory of fluvial sandbody architecture, the single beach bar was identified and its architecture was analyzed, then the 3D architecture model was built. The discrepancy of the hydrocarbon distribution was present from the angle of sandbody architecture, and the contradiction of oil and water distribution was resolved. In the single depositional time unit in which the thick sandbodies were widely deposited, independent fluid systems may exist in the overlaying sandbodies due to the lateral migration of the channel. Also, in the single channel, the incomplete connectivity and the discrepancy of oil-bearing grade of different sandbodies were caused by the bounding surfaces between the beach bar and the channel fillings sandbodies. Furthermore, the oil saturation and the oil-water interface had considerable difference between wells even in the single mid-channel bar due to the internal bounding surface of the sandbodies.

The primary factor quantitative reservoir assessment method was used in this paper to precisely evaluate the clastic reservoir property of the Shahejie Formation in Dongying Sag. The reservoir capacity parameters (porosity and permeability), grain sorting, matrix content, granularity, extent of being buried and pressed, solution and cementation degree were chosen as the reservoir quality assessment parameters. Weight coefficients of other factors related to porosity which is the primary factor are obtained by grey correlation analysis. Then, the reservoir assessment classification is determined by the comprehensive reservoir quality assessment gene “Q” . When there are short of porosity and permeability data, the relevant weight coefficients of other factors are obtained by their correlations with porosity as well, and the comprehensive reservoir quality assessment gene Q1 is obtained by the similar method as Q. The result of reservoir assessment of the samples given by  “Q” and Q1 is consistent with that by the clastic reservoir classification criterion which was offered by CNPC. The method was used to classify and evaluate the Shahejie Formation clastic reservoir and the result was compared with the oil testing result, the two results were highly consistent with each other. The analyses show that this method is practical in reservoir comprehensive assessment. According to the value of Q or Q1, the reservoir quality of some interval in some area can be quickly predicted.

There is abundant Oil and gas in the western sag. According to the statistical analysis of the geological factors of 773 reservoirs discovered, it is considered that there are various reservoir types in the sag, with structural and lithological reservoirs dominating and composite reservoirs developing. The statistics data show that nearly 90% of reservoirs are related to faults. The types of reservoir are significantly controlled by structural belt. There are mainly anticlinal and lithological-structural reservoirs in gentle belt, anticlinal and fault block reservoirs in central anticlinal belt, and lithological reservoirs in steep slope belt. Reservoirs are obviously controlled by sedimentary facies, and mainly distribute in fan delta facies, delta facies and turbidite fan facies. The spatial distribution of oil and gas resources follows “the model of the total oil and gas resources balance”, and shows obvious complementary characteristic on both the plane and the stratigraphic horizon. According to research, the distribution of reservoirs is jointly controlled by hydrocarbon generation sag, faults, abnormal pressure and facies in the western sag. Firstly, the active source rock in Sha 3 Member and Sha 4 Member are well development and the resource quantity is very large. So they form the base of hydrocarbon enrichment and control the distribution of reservoirs in Western Sag; Secondly, oil-bearing sand bodies of each Formation and Member are overlapped and continuous plane distribution, which is favorable to lateral migration; Thirdly, the development of pressure relief faults led by the strike-slipping at the end of Dongying phase, which makes the oil and gas large scale and far-distance vertical migration possible.

The Zhongwei area of Helan Mountains is a new prospecting area that was registered by the Shengli Oilfield Company of SINOPEC in August 2002. So far, no drilling data concerning the Zhongwei prospecting area has been obtained and the exploration degree is quite low as a whole. To study the hydrocarbon-generating capability of the Upper Triassic source rocks in Zhongwei prospecting area, the Upper Triassic dark mudstones in Rujigou area in the north of Zhongwei prospecting area have been collected and analyzed. The results indicates: 1) The content of organic carbon is 3.03%, and the total HC content is 0.0025% ; 2) The kerogen maceral are mainly vitrinite, and the type of organic matter in the mudstones is type-Ⅲ kerogen whose index is -72.5. The vitrinite reflectivity of the samples is 0.93%, and the thermal evolution of the organic material has reached maturity degree. Compared with the Yanchang Formation and the Carboniferous - Permian coal measures in the Ordos Basin, the organic matter of the Upper Triassic dark mudstone samples in Rujigou area has a higher abundance and has reached a high maturity, which can become better gas source rocks. The Zhongwei prospecting area and Rujigou area was dominated by the shore-shallow lacustriine facies during the Late Triassic, and Zhongwei prospecting area is closer to the lake center, and thus the sedimentary facies is more favorable. The Upper Triassic source rocks in Zhongwei prospecting area have higher gas generating ability, and the gas exploration in this area should be strengthened on the basis of the source rock evaluation.

Abstract  For a long time, there have been heated arguments concerning the sedimentary environment of the Upper Ordovician Wufeng Formation in southern China. There are two opposite viewpoints: the deep water origin theory and the shallow water origin theory. It seemed that these two viewpoints both can negate the other one with ample evidence. The focus of the problem is related with the Guanyinqiao Member. According to the depositional characteristics of the Wufeng Formation, it should belong to a deep water deposition. But the Guanyinqiao Member at the top of the Wufeng Formation contained abundant fossils of Brachipodas, Trilobites, Corals and so on, thus it was considered as a “shallow water shelly facies” for a long period. Through measuring and detailed observation of tens of profiles in the Mid-Upper Yangtz area, it is concluded that the Guanyinqiao Member was deposited in a deep water allogenic environment. The evidences mainly include: the typical shallow water biologic fossils being contained in the Guanyinqiao Member such as the corals, echinoderms and brachiopods were preserved in the bioclastic calcirudite limestones in broken pieces. The overlying and underlying strata of the limestones were black graptolite shales, which was obviously transported by the clastic debris from other places and its sedimentary environment was not a shallow water environment but a deep water one. The Guanyinqiao Member is widespread with a very small thickness, which is not characterized by any shallow water deposition. The boundaries between the Guanyinqiao Member and its overlying Lower Ordovician Longmaxi Formation and underlying Wufeng Formation shales were inconsistent and changed sharply indicating the inharmonious deposition and was the characteristic of allogene deposition.. The Guanyinqiao Member only existed in the events deposition affecting range, in other areas, the Wufeng Formation can connect continuously with the overlying Longmaxi Formation. The deep water allogence deposition includes debris flow deposition(calcirudite), turbidite deposition(slity grain limestone) and internal-tide deposition(laminated siltstone). Regardless of the interpretation of the environment, the Wufeng Formation was determined as a deep water deposition due to its own characteristics.

Abstract  The Mesoproterozoic Wumishan Formation at the Jixian section in Tianjin is a set of more than 3000 m-thick stromatolitic carbonate succession. In this seccession, several lithofacies units, i.e. the subtidal stromatolitic biostrome, the thrombolitic bioherm, tidal-flat micritic dolomite and lagoon facies dolomitic mudstone and shale, make up many meter- scale cycles of the peritidal carbonate type that are nominated as the Wumishan cyclothem. The microdigital stromatolites developed in the lower part of the Wumishan Formation, is defined as the “ Pseudogymnosolen mopanyuensis-Scuphus-Yangzhuang columnaris” assemblage by palaeontologists. This category of stromatolites has still been interpreted as the aroganite (tufa) sea floor precipitates by sedimentologists, and has further been thought as the special products during the transitional period from the stromatolites made up of the sea-floor aroganite precipites of the Archean to the stromatolites made up of the clastic and muddy carbonates of the Neoproterozoic. Therefore, an important horizon for the ending of the microdigital stromatolites was recorded in the Mesoproterozoic Wumishan Formation, which provides useful information for understanding the geologic and historical evolution of microbial carbonate rocks of the Precambrian which is characterized the stromatolites.

The sedimentary model of the Upper Member of Guantao Formation on the northern slope of Kengdong uplift in Bohai Bay Basin was established by analyses of core observation, granularity data, parameter calculation, drilling and logging data, combining with the domestic foreign river research result. The investigation indicated that the Upper Member of Guantao Formation in the study area was fluvial deposition, and it could be determined as the transitional fluvial type between braided fluvial and meandering fluvial according to the sediment characteristics and the planar distribution. The average curvature of the channel is more than 1.7, and the vertical sequence is characterized by meandering fluvial deposits with higher content of mudstone and lower content of sandstone.The top of the sequence usually directly overlied the flood plain deposits, especially the channel distributed fluvial was formed due to the development of the sandbar in the interior of the channel. The granularity characteristic of the sandbar sediments showed great difference from the meandering fluvial facies, that is, it is controlled by flood. In this paper, the sedimentary model for the Upper Member of Guantao Formation was established in terms of the anabranched river concept which is used widely in hydraulics and topography. The subfaices includes fluvial bed, bank, floodplain, abandoned channel which constituted a fining upward positive cycle. The channel sandbar is the main sandbody and is usually directly overlied by floodplain deposits. The crevasee fan sandbodies are seconly favorable to the channel sandbar.

Huaxi area of Guiyang was located in the transitional belt from shallow-water carbonate platform to deep-water basin during the Early–Middle Triassic, and each sedimentary systems tract has its own characteristics especially the carbonate breccia wedge of lowstand systems tract(LST). The field investigation indicates that there are four times of carbonate breccia wedge of LST, which reflect this area experienced at least four significant sea level changes in the Early –Middle Triassic. The migration of carbonate breccia wedge also reflects the shifting of the platform margin and the relative sea level changes. Among them, the Guli breccia  wedge extended the farest distance to the platform, which represents that the platform margin shifted to the platform for the farest distance. The Zhangjiawan breccia wedge represents the fast sea level falling in the Early Anisian. In addition, this paper reconstructed the evolution of cabonate platform margin based on the analyses of  the depositional characteristics of the breccia wedge and the geometric relationship of each lithostratigraphic unit: ramp platform margin→depositional platform margin→reef by-pass margin.

Abstract Abundant trace fossils Chondrites were found in the Lower Carboniferous Shiguaizi Formation in Shiguaizi section at the toes of the Qimantage Mountains and the Upper Carboniferous Di’aosu Formation near Qinghua iron mine of Wutumeiren area in the south margin of Qaidam Basin. Three ichnospecies were identified: Chondrites fenxiangensis Yang，1984; Chondrites  filifalx Volk，1964; Chondrites maqianensis Yang，1988. It is considered that the Early Carboniferous in Shiguaizi area was dominated by syneclise environment and the Upper Carboniferous of Qinghua iron mine was a restricted carbonate platform according to the trace fossils characters and the lithological characteristics as well as other body fossils information. Bioturbated reworking on reservoir, which is an essential influence in the reservoir quality, was also investigated. The investigation has a great reference significance in reconstructing the sedimentary environment and appraising the reservoir quality in the south  margin area of Qaidam Basin.

Abstract The Chengbei fault slope of Huanghua Depression lies in the slope belt between the Qikou Sag and the Chengning Uplift, and develops many unconformities. These unconformities are very important for the hydrocarbon accumulation in this area. By analyses of seismic data, the unconformity can be divided into fold unconformity distributing in the basement, faulted-fold unconformity distributing in the downthrown block of the large rift, truncation unconformity distributing in the upthrown block, onlap unconformity distributing in the slope area of the uplift and parallel unconformity distributing in the sagging area. According to the log data, the unconformities are divided into three parts vertically: rocks developed above the uncoformity, weathered clay layer and semi-weathered clay layer. Because of the differences in thickness and lithology, the vertical textures of unconformity include four patterns of lithology configuration, namely ACE, ADE, BCE and BDF. The unconformities in the Chengbei fault slope are not only the important paths for the oil and gas lateral migration, but also the good places for the petroleum accumulation. Onlap unconformity petroleum reservoirs can be formed above the unconformity, and truncation unconformity petroleum reservoirs can be formed below the unconformity due to the weathered clay layer. The exploration has proved that a lot of petroleum display and petroleum reservoirs are deposited in the 50 m range above and below the unconformities. The researches of relationship between unconformity and petroleum accumulation will broaden the exploration area of subtle reservoirs in the Huanghua Depression and have important academic and practical significances for the further exploration in eastern China basins.

Abstract  Based on the interpretation results of seismic data and structural maps, the structural transfer zones and their significances hydrocarbon in the Bohai Bay area is discussed. The structural transfer zones are divided into regional transverse accommodation zones and local transfer zones. The former is the large-scaled NW-striking faults, where intense earthquake activities exist, and which divided the offshore area of the Bohai Bay Basin into the northern, the central and the southern segments. The local transfer zones are located in the overstepping area wherein which normal faults interact each other. According to the dips and assemblage characteristics of the normal faults, three types of local transfer zones have been classified in the Bohai Bay area, including the relay ramps, oblique anticlines and horsts. The hydrocarbon significance of the structural transfer zones involves their controlling influence in the traps formation, in the high quality reservoir development and in hydrocarbon migration.