Shale gas has realized industrial developing in the Sichuan Basin and its peripheral region, and has become one of the important resources for future natural gas production growth of China. The shale gas in the Sichuan Basin is produced from the Ordovician and Silurian strata which are deeply buried with high thermal evolution and complicated tectonic history, thus bring challenges to the shale gas exploration. Fortunately, the gas-producing black shale is rich in graptolite fossils. Paleontologists used the method of graptolite biostratigraphy to recognize the precise stratigraphic intervals of favorable gas-producing black shale in the Sichuan Basin using well-established high-resolution graptolite biostratigraphy, providing a critical tool to guide the exploration of the shale gas recourse in China.

As an advanced management method, benchmarking management is widely used by famous enterprises at home and abroad, and it provides an enterprise with a goal of struggle and a thought to continuous improvement. Based on benchmarking analysis, shortcomings can be identified and reduced, and the overall competitiveness and management of an enterprise can be improved. For challenges from low oil prices, low grade and high cost, China National Petroleum Corporation strengthened the innovation of benchmarking management, and provides effective methods for improving the overall management and the basis for making effective decisions on exploration and deployment through benchmark analysis. In this paper, the necessity and significance of exploration benchmarking management is analyzed; the methods and implementation steps of benchmarking management are introduced; a systematic and complete index system is established by taking 16 oil and gas field enterprises as research cases, a benchmarking evaluation model is designed; and finally four primary index systems including plan, cost, effectiveness and reserves, and 16 secondary index systems are established. The highlights are an effectiveness index of 3D seismic survey and an index model of reserves evaluation. Demonstration and application in oilfields have proved all indicators good, and exploration and management have been improved continuously. These may ensure new results of oil and gas exploration, and facilitate high-quality exploration to a new level.

In the Qiulitag structural belt, one of the important oil and gas exploration zones in Kuqa depression of the Tarim Basin, early exploration discovered the large Dina 2 condensate gas field, the Chaule 1 reservoir and the Dongqiu 8 shallow reservoir on the east and west sides. Since then, no gas reservoir has been found for 16 years. In the Qiulitag structural belt, the surface condition is difficult with blade-like ridges here and there, and the underground composite salt layer is strongly deformed. Resulting in poor 2D seismic data, it's difficult to accurately identify the structure. In this study, by focusing on the task to break through exploration technology bottleneck in "identifying traps", and strengthening the regional geological research, structural segments were described, especially the Zhongqiu segment of the Qiulitag structural belt; by improving 2D wide-line seismic acquisition and processing, traps were found in batches, and the breakthrough was located; by scientific decision-making, and advanced deployment of Dongqiu 8 mountain 3D seismic survey, the subsalt Zhongqiu 1 structural trap was identified and an exploration well, Zhongqiu 1, was drilled. High-yield industrial oil/gas flow was obtained from the Cretaceous Bashijiqik Formation, proving a strategic breakthrough and indicating a bright future in oil and gas exploration in the Qiulitag structural belt.

According to the hydrocarbon accumulation characteristics and hydrocarbon distribution laws of Upper Permian in the Mahu oil region, the distribution of three types of oil and gas reservoirs were clarified, and the pattern of large-scale hydrocarbon accumulation above the source rock of extensive retrograding fan delta in the stratigraphic setting was established. It was the first time that the Permian stratigraphic systems in the east and west of the Junggar Basin were unified. By petroleum geological analog, a significant petroleum replacement field with the area over 2.5×10⁴ km² was discovered in the middle assemblage in Upper Jurassic of the Central depression. The controlling of palaeogeomorphology on sedimentation and sand was analyzed interactively, and it is indicated that the Upper Permian is controlled by groove systems and 8 major deposits of fan deltas are developed in the setting of stratigraphic overlap. Thus, it is confirmed that 4 major exploration fields and 10 favorable zones are good in hydrocarbon accumulation conditions, and they satisfy the conditions of overall exploration. The west slope of Shawan sag is a favorable destination of long-term hydrocarbon accumulation. In the Upper Wuerhe Formation and Baikouquan Formation, there are favorable reservoirs of fan delta front facies, with good physical properties. There are a great number of broad lithologic trap groups, with abundant resources and low exploration degree. It is revealed that the west slope is a major field of risk exploration with the characteristics of multi-layer stereo hydrocarbon accumulation. In 2018, the lithologic oil reservoir group in the stratigraphic setting of west slope was selected as the breakthrough point for exploration, where Well Shatan 1 was deployed. The significant discovery demonstrates the potential of multi-layer stereo exploration, similar to that in the Mahu sag. And it is expected to be connected with Mahu oil region, forming an other great exploration area.

The deep formation of Bozhong sag in the Bohai sea area has favorable geological conditions for the formation of natural gas fields. BZ19-6 large-scale condensate gas field is the largest natural gas field discovered so far in Bohai Bay Basin, with reserves exceeding 100 billion cubic meters. Based on a large number of core, thin section, well logging and geochemical data, the deep gas reservoir-forming conditions in Bozhong 19-6 structure are systematically analyzed. It is proved that the deep layer of Bozhong sag has great potential for generation of natural gas and is the basis for the formation of large-scale condensate gas fields. The extremely thick overpressure mudstones of Dongying Formation and Shahejie Formation with stable regional distribution provide good sealing conditions for the preservation of large condensate gas fields. It is the first time to discover huge thick fractured-porous sandy conglomerate reservoir in Kongdian Formation of Paleogene in Bohai Bay Basin, which breaks through the forbidden area of searching for thick sandy conglomerate reservoir in depression area and greatly expands the exploration field of Paleogene oil and gas. Based on the analysis of the formation mechanism of high quality reservoirs in Archean deep buried metamorphic rock buried hills, it is proposed that the key to the formation of high quality reservoirs in metamorphic rocks is the development of large-scale fracture systems and dynamic fracture zones in buried hills caused by multi-stage dynamic fragmentation. These results have guided the discovery of large-scale condensate gas fields in Bozhong 19-6 structure, contributed to the breakthrough in natural gas exploration in Bohai Sea, and have important guiding significance for deep gas exploration in Bohai Bay Basin.

Significant achievements have been made in exploring foreland thrust belts, which promoted the exploration process of large oil and gas provinces in foreland basins since the 12^th Five-Year Plan and further consolidated the resource base of the West-East Gas Pipeline. However, the recent exploration progress has become slow. On the one hand, it brought a large potential for increasing reserves, and on the other hand, there are many challenges. There is a good prospect of exploration in this area. Based on references, follow-up of exploration and research progress, the results of the fourth oil and gas resources evaluation and the latest understanding of exploration, the important exploration fields and potential accumulation conditions have been investigated in the foreland thrust belts in Kuqa of the Tarim Basin, the southwestern Qaidam Basin, the northwestern Sichuan Basin, the southern margin of Junggar Basin, and the southwestern Tarim Basin. Source rocks, reservoirs, caprocks, accumulation factors, traps and preservation conditions have been analyzed, potential favorable zone evaluation and optimization has been finished based on exploration targets, favorable areas, resource scales, structures and trap types, expected reserves, favorable factors and geological risks, and finally 7 implementable zones, 6 alternate zones and 9 preparatory zones are proposed, which will provide natural gas geological reserves of 6500×10⁸m³ and oil geological reserves of 3.5×10⁸t in 5 years. Four key geological problems have been analyzed, involving building complex 3D models, predicting favorable belts and good reservoirs, hydrocarbon accumulation difference and factors configuration, and effective evaluation to structural traps, as well as supporting technologies such as precise imaging of complex structures, low SNR, (residual) static correction, safe and efficient drilling. Taking the northern tectonic belt in Kuqa foreland, the foreland thrust belt in southwestern Tarim, and the foreland thrust belt in northwestern Sichuan Basin as examples, exploration strategies and deployment recommendations are proposed.

Located in the western part of the Qaidam Basin, the Yingxiongling structural belt developed many Neogene oil and gas fields such as Shizigou, Huatugou, Youshashan and Yingdong, and so becomes the primary battlefield for oil exploration in the Qaidam Basin. In order to expand the exploration field of Neogene clastic lithologic reservoirs, comprehensive analysis has been carried out on outcrops, cores, particle size test and other data, and based on which two types of sandstones in shallow lake beach and underwater braided river delta were identified. On the background of lacustrine sedimentation, underwater braided river delta sandstone gradually accumulated into the lake basin under the control of western sources, and the NW-SE echelon-like shallow shoal lake beach sandstone migrated into the lake basin. The upper Ganchaigou underwater braided river delta sandstone is developed in the west of the structural belt, and the beach dam sandstone is developed in the west wing and the core of the structural belt. The lower Youshashan underwater braided river delta sandstone is developed in the west wing and the core of the structural belt, and the beach dam sandstone is developed in the east wing and the core of the structural belt. The structural evolution features indicate that the Neogene sandstone reservoirs in the upper Ganchaigou Formation and the lower Youshashan Formation were distributed in the slope area when they deposited, but today's Yingxiongling structural belt is the late inverse structure formed at the end of the Neogene Shizigou Formation. The sandstone deposited in the early stage might form lithologic traps like updipped pinchout and sandstone lens on the background of tectonic inversion. They are favorable exploration targets for finding large-scale lithologic reservoirs.

Low-grade faults are relatively developed in the Gufengzhuang area on the western margin of the Ordos Basin. Their characteristics and sealing capabilities are closely related to hydrocarbon accumulation. It is significant to analyze the characteristics and sealing capacities of the faults for petroleum exploration under the complex tectonic conditions. The characteristics of the low-grade faults was analyzed based on seismic and well data, and the sealing capabilities of the faults were evaluated using the displacement pressure difference between reservoirs and faults, according to the matching relationship between faults and hydrocarbon accumulation and the lithology of the Yanchang Formation. The result indicates that the faults are mainly reversed Late Jurassic to Early Cretaceous faults characterized by small fault throw, large dip and short extension, and in echelon distribution from NW to SE. The Yanchang Formation in the study area is thin interbeds of sandstone and mudstone, which are easy to develop fault rocks, so the sealing capability depends on the displacement pressure difference between the fault rock and related reservoir. The mudstone in the fault rock accounts for 20% to 60%, and the displacement pressure is generally less than 1.5MPa, which is generally smaller than the displacement pressure in the reservoir. Most faults are open, and less are close. During the early time of the Early Cretaceous, the open faults acted as transport systems for hydrocarbon migration, and hydrocarbon accumulated in low-relief traps and high-permeability reservoirs near the faults, controlled by the surrounding rock and sealing faults.

The Leikoupo Formation in the Sichuan Basin developed carbonate platform deposits represented by shoal dolomite and karst reservoirs. Important discoveries have been made in the western Sichuan Basin, such as the Zhongba gas field and the Xinchang gas field, it is the important target for Triassic gas exploration in the Sichuan Basin. Researches have been carried out to clarify the boundary between the Leikoupo Formation and the overlying Ma'antang Formation and the characteristics and distribution of the karst reservoirs in the Leikoupo Formation in the western Sichuan Basin. The results found 4 types of contacts. According to the outcrops, cores, thin slices, logging and seismic data, the boundary between Leikoupo Formation and Ma'antang Formation is redefined:Leikoupo Formation developed weathering crust and karst reservoirs which indicate an exposed environment. While Ma'antang Formation developed deep water deposits without dolomite and exposed top. Controlled by the exposed top and the paleogeomorphology, well-seismic data predict that good reservoirs are distributed in the central and southern parts of western Sichuan Basin, with strong heterogeneity and changing facies. Future exploration targets are proposed in the southern part of the western Sichuan Basin with the relation between the sources and the reservoirs.

As the important marine clastic exploration target in Tazhong area, Tarim Basin, the 3^rd upper sub-member of the Silurian Kepingtag Formation was analyzed using core, logging, seismic and experimental data, and the types and distribution of the sedimentary systems were systematically researched according to the paleo-geomorphology, paleosalinity and hydrodynamic force before deposition. The results show that the Silurian paleo-geomorphology gradually increases from north to south, with multiple narrow and long low sags and underwater bulges. The depositional systems of tidal flat, estuary and tidal delta are developed and controlled by the palaeo-geomorphology in the background of transgression, and the differences in the types and energy of primary activating water forces developed different types of sand and sedimentary formations. In the sedimentary system of the tidal flat, primary types of sand bodies are subtidal channels and intertidal flats. The former show complete three layers and are vertical to the coast in banded distribution. Channels and tidal bars are common in the estuary system. The sandstone has thin mudstone, and the axis of the sandstone extends far and parallel to the axis of the estuary. Underwater distributary channels are developed with silica, flint gravel and large erosion surfaces in the tidal delta system. Finally, the depositional model composed of tidal flat, estuary and delta was established and the distribution of favorable reservoirs was predicted in Tazhong area.

The Middle Permian carbonate rocks in the central Sichuan Basin have experienced multi-stage tectonic deformation and karstification, and accordingly various irregular fault-karst carbonate rocks have been formed along the dissolved fault zone. In order to clarify the forming and development characteristics, and predict where fault-karst carbonate rocks are developed, the type and forming mechanism of fault-karst carbonate rocks have been studied. According to core, thin section, logging and seismic data, three types of fault-karst carbonate rocks were identified, including vug-fracture type, fracture type and fracture-vug type, which depend on the development scales and periods of karst reservoirs and faults. The vug-fracture type is based on the karst vugs from the superposition of syn-depositional fault belts and the exposure of the Maokou Formation. The fracture type is the result of the joint dissolution action among meteoric water, thermal fluids and organic acid on the resurrecting deep and large faults formed in the Caledonian and Hercynian periods. The fracture-vug type is the fault controlling composite formed in the Caledonian and Hercynian Movements, which are formed by the secondary faults and plane fault-karst carbonate rocks as the result of meteoric water and organic acid dissolving the Middle Permian granular beach. As a type of composite reservoir, fault-karst carbonate rocks provide good spaces for oil and gas, and are mainly distributed in the dissolution planes of large and deep faults and its associated secondary fault belts. The fracture-vug type is the most favorable reservoir.

Oil and gas migration and accumulation coefficient, referring to the ratio of oil and gas resources to hydrocarbon generation in a certain geological unit, is a key parameter for oil and gas resources evaluation. With the increasing improvement of exploration and development level over the last decade, more calibrated units and geological parameters have been accumulated, which lay a foundation for further researches on the oil and gas migration and accumulation coefficients. This paper analyzes the geological parameters of 86 calibrated units in 14 major petroliferous basins in China, studies the relationship between the oil and gas migration and accumulation coefficients and geological parameters in different types of basins. The results indicate that the oil and gas migration and accumulation coefficients in different types of basins are correlated with the primary hydrocarbon generation time, the reservoir thickness ratio, the trap area coefficient and the number of regional unconformities. For all types of basins, the number of regional unconformities has the greatest impact on the oil and gas migration and accumulation efficiency. For rift basins in eastern China, the influence of the trap area coefficient on the oil and gas migration and accumulation efficiency is close to that of the reservoir thickness ratio, lower than the impact of the number of regional unconformities. Besides the influence of the number of regional unconformities, craton basins of central China and foreland basins of western China are secondarily affected by the trap area coefficient and the primary hydrocarbon generation time separately. Based on these conclusions, the statistical models of the oil and gas migration and accumulation coefficients in different types of basins are systematically established. The calculation indicates that the forecast of statistical models is accurate. Accordingly, the statistical models can be used to forecast the oil and gas migration and accumulation coefficients in different types of frontier exploration basins quickly and quantitatively.

As an ultra-deep (5,000-7000 m), complex and large-scale carbonate oil and gas field, Tazhong-Ⅰ condensate gas field had heterogeneous reservoirs and difficulties in keep stable gas production because of long well completion period and low drilling success rate, which were caused by long horizontal sections and difficulties in identifying vertical target layers. Previous design of the wellbore trajectory of a horizontal well drilled in carbonate reservoirs only considered the principal stress, but not the comprehensive characteristics of geostress, so it could not ensure that the horizontal wellbore was drilled in good reservoir zones, accordingly it was hard to design a path favorable for wellbore stability. In this study, based on reservoir development law and geostress characteristics, three optimization techniques including comprehensive evaluation of reservoir drill-in rate, prediction of reservoir top stress field and pre & post-stack fracture prediction were proposed for optimizing horizontal well trajectory. Application of these three technologies has significantly increased the drill-in rate to an average of 46.5%, and the drilling success rate to over 85% in horizontal well development. This promoted the effective development of the Tazhong-Ⅰ gas field, and provided basis and support to the optimization design of horizontal wellbore trajectory for developing carbonate reservoirs in the Tazhong-Ⅰ gas field and other similar carbonate oil and gas fields.

By establishing a quantitative model using logging data, it is simple to obtain the geological information of continuous mud shale intervals, and provide basic data for shale gas geological research. In this study, based on the shale gas logging evaluation method, considering the geological characteristics, taking the core data as the correcting standard, and using the △1gR method, the AC method and the porosity -maturity correlation method, logging models were built, involving organic carbon content, porosity and maturity in the Chang 7 Member of the Yanchang Formation in the Xiasiwan-Yunyan area, Ordos Basin. Application of the models in individual wells estimated the organic carbon content from 0.5% to 6.5%, the vitrinite reflectance from 0.65% to 1.25%, and low porosity in the Chang 7 shale. Based on these data, the geological characteristics and the distribution law of the Chang 7 shale are clear, which lays a foundation for future exploration and development of shale gas.