China Petroleum and Chemical Corporation (“Sinopec”) has been highlighting the resource strategy and transforming the development mode since the initiation of the “12th Five-Year Plan”. In the past period, for purpose of efficient exploration, Sinopec made deeper researches on hydrocarbon accumulation in structures like marine carbonate, foreland thrust belts, vast lithologic-stratigraphic reservoirs, and marine deep gas and shale gas formations. Through continuously working on bottleneck technologies, Sinopec has developed a series of characteristic techniques for data acquisition and processing, optimal and fast drilling of extra-deep wells, and complicated reservoirs and reservoir evaluation. With these supporting technologies, Sinopec achieved great breakthroughs and progress in large-scale petroliferous basins like Sichuan, Ordos, Tarim, Junggar, Bohai Bay and East China Sea, and realized the goal of basically stable development of oil and rapid development of gas. During the 13th Five-Year Plan, under the new normal of economy and the increasingly complicated internal and external environments, Sinopec will have a long way to go for exploration. Currently, Sinopec’s prospects in the eastern China stay in a stable development stage, with an average proven rate of oil resources of 46.4%, and its prospects in the central and western China are still in the early exploration stage, where abundant potential resources provide the basis for sustainable development. By continuing the resource strategy, Sinopec will focus on large-scale basins to make great breakthroughs and discoveries and insist fine exploration in mature blocks to realize large-scale commercial discoveries. Moreover, Sinopec will promote efficient exploration by theoretical, technical and management innovations, so as to make new contributions to the sustainable development of Sinopec and guaranteeing the national energy security.

The Jiyang depression, being explored for over 50 years, has entered a stage of subtle reservoir exploration. During the 12th Five-Year Plan, exploration targets became even more complicated. To enhance efficiencies of explorations, new geologic models were built to tap potentials of mature zones, by assessing available resources, improving quality of seismic data and highlighting bottlenecks in geologic studies on shallow and mid-deep formations. In this way, new breakthroughs were achieved in existing oilfields through reinterpretation of available data. To explore areas with bottleneck challenges, marginal reservoirs, Neogene fluvial channel sandstone reservoirs, deep formations and other potential targets, new models for early oil and gas migration and accumulation, multilevel sequential uncomfortable traps, description of fluvial channel sandstone reservoirs, structure of complex faulting zones, and assessment of sandy conglomerates on steep slopes were established for fine exploration. In addition to the discovery of the Qingnan oilfield and the Sanhecun oilfield, 14 key breakthroughs were made in preliminary exploration. In total, 12 potential reservoirs with reserves of tens of millions of tons each were identified. Explorations during the 12th Five-Year Plan show that there are great potentials in highly explored areas, which can be efficiently through innovation.

Fuling shale gas field is the first shale gas field put into commercial development, with the largest proven reserves and the highest average test production in China. It was discovered on November 28, 2012, by Sinopec Exploration Company based on the theory of “binary enrichments” for highly-evolved marine share gas in complex structural areas in southern China. By the end of 2015, its total proven gas reserves were 3805.98×108m3, and the designed production capacity of 50×108m3 in Phase I was achieved. This gas field is characterized by integration of source and reservoir, intensive layered distribution and general gas endowment, It is a typical self-generation and self-storage shale gas field. As a mid-deep, high-pressure, and high-quality natural gas reservoir, it contains high-quality shales in deep-water continental shelf, with fine roof and floor conditions and weaker structural transformation in later stage, which are the major factors controlling shale gas enrichment and high productivity in this area. Based on the discovery of Fuling shale gas field and the exploration practices in the Sichuan Basin and its periphery, the main controlling factors for shale gas enrichment in complex structural areas in southern China were analyzed. The analysis highlighted the preservation condition as the key factor. Conclusions are drawn in three aspects. First, extra-basin tectonic uplifting time, syncline width, burial depth and fracture are the main parameters to evaluate the preservation conditions in shale gas layers. Second, for areas at the basin margins, the evaluation should focus on the effects of basin-controlling faults on shale gas layers. Third, nature and scale of the faults and development features of high-angle fractures in the basin are critical for evaluating the shale gas preservation conditions. From the discovery of Fuling shale gas field, the following enlightenments can be obtained for shale gas exploration in complex structures in southern China. First, shale gas exploration should be conducted depending on the basic laws of oil and gas generation. Second, several shale gas exploration targets exist in southern China, especially the regions deeper than 4500 m, extra-basin normal pressure regions, and continental shale gas areas. Third, basic information, innovative ideas and critical technologies are essential for making breakthroughs in shale gas exploration.

The Shuntuoguole uplift in the Tarim Basin was formed in the middle stage of Caledonian. In the early stage of Early Cambrian, the Yuertusi Formation slope-shelf facies source rocks were formed. During the Early Cambrian-Middle Ordovician, carbonate sedimentary formations with thickness up to 3000 m were developed, and multiphase sea level fluctuation contributed to the formation of exposed karst reservoirs. Meanwhile, during the Caledonian-Hercynian, multiphase faulting activities occurred, which were favorable for fracture development and fluid reformation to form multiple types of reservoirs. The very thick mudstones deposited during the Late Ordovician can act as regional cap rocks. In the Shuntuoguole uplift, a complete source-reservoir-cap-rock assemblage exists in the Lower Palaeozoic, suggesting it a prospect of hydrocarbon accumulation. The oil and gas exploration at the earlier stage focused on the Shaya and Katake uplifts, while the deeply-buried Shuntuoguole uplift was not thoroughly understood. Further basic studies reveal that the Shuntuoguole uplift is in the low geothermal environment for a long term. During the Himalayan, the Lower Cambrian source rocks were generating condensate oil-natural gas, implying the favorable conditions for the formation of large oil and gas fields with late-stage accumulation. The Cambrian – Middle-Lower Ordovician carbonate rocks are the most important targets. Based on the seismic technology R&D for ultra-deep zones in desert areas, targets were selected for well drilling. Great breakthrough has been made. A giant oil and gas field in the Shuntuoguole uplift is taking shape. It is promising to realize a continuous oil and gas pattern in central and northern Tarim Basin.

Taking the Longfengshan sub-sag in the Changling fault depression, southern Songliao Basin, as an example, this paper discussed the hydrocarbon accumulation conditions, including source rock, reservoir, cap rock, and hydrocarbon migration and preservation. It is considered that the Changling fault depression has the basic petroleum geological conditions for hydrocarbon accumulation, with both vertical and lateral pathway system constituted by fault and sandbodies. Furthermore, deep structure was shaped earlier than the main hydrocarbon accumulation stage, which is favorable for hydrocarbon migration and preservation. There are four main controlling factors for gas accumulation in the Yingcheng Formation clastic rocks in the Changling fault depression. First, quality and thermal evolution degree of the Shahezi Formation and Yingcheng Formation source rocks in deep sags controlled the oil and gas source supply. Second, predominant sedimentary microfacies controlled the distribution of favorable sandbodies while reservoir properties determined the hydrocarbon enrichment degree, and presence of secondary pores significantly contributed to the gas-bearing potential. Third, the stable mudstone cap rock in the upper Yingcheng Formation and the faults developed in late stage controlled the preservation conditions and determined the major hydrocarbon-rich strata. And fourth, the fault-sandbody pathway system formed under the structural setting in hydrocarbon accumulation stage effectively controlled the oil and gas migration direction. Study in this paper suggests that the clastic rocks in the Changling fault depression have a gas accumulation pattern of “source supply from deep sag, conduction via a vertical and lateral fault-sandbody pathway system, and structure-cap- rock controlling hydrocarbon accumulation”.

After 40 years’ operations, the North Jiangsu Basin has been moderately or highly explored. During the 12th Five-Year Plan, a series of exploration results were achieved within the North Jiangsu Basin by strengthening the studies and evaluations on “three new domains” ( new zones, new strata and new types). Larege-scale reserves were discovered in low-permeability deep zones and multiple types of subtle oil reservoirs (e.g. sublacustrine fan, beach bar, and submarine fan glutenites) within the Huazhuang area of Gaoyou sag and the new Qinying area and Funing Formation of Jinhu sag. These discoveries provide a firm resource basis for the stable development of oilfields. Some new geological understandings were obtained in aspects of the formation mechanisms of transtensional faults at slopes, the development mechanisms of high-quality deep reservoirs and the sedimentary modes of various sand bodies of the Dainan Formation in the deep areas of the sags, providing the theoretical basis for exploration planning and the important guidance for practical explorations and incremental discoveries. Moreover, three technologies that were geologically suitable for the North Jiangsu Basin were developed and improved, including seismic data processing and interpretation of igneous rock areas, identification and description of concealed faults, and identification and prediction of various sand bodies in deep areas of sags. They provide grand support for increasing reserves and stabilizing production.

Through efforts in eight years since 2006, a great gas exploration discovery was made in the Pengzhou Leikoupo Formation of the Longmenshan piedmont tectonic belt, western Sichuan Basin, which contributed a new large marine gas field - Pengzhou gas field. Study indicates that the Pengzhou Leikoupo Formation reservoir presents as there is a dissolution-pore type dolomite reservoir under a structural setting of large positive uplift belt, with features of a big thickness, a wide distribution, better lateral continuities, good physical properties, high gas-bearing potentials, and high productivities. The reservoir is suggested as a sour gas field with normal temperature, normal pressure and high sulfur content. It is concluded that the Pengzhou large gas field of Leikoupo Formation was formed under three major conditions. First, multiple source rocks supplied abundant hydrocarbons, providing a good material basis. Second, large-scale dolomite pore type reservoir existed in the 4th member of the Leikoupo Formation, providing sufficient storage spaces. Third, large positive uplift belt provided enough spaces for hydrocarbon accumulation. Meanwhile, it is pointed out that the Leikoupo Formation gas reservoir in the Longmenshan piedmont tectonic belt features high filling degree and great exploration potential.

Sinopec’s licensed block in the western margin of the Junggar Basin is predominantly distributed in the Chepaizi uplift. Since it is far from oil sources and has complicated geologic conditions, the block is less explored with protracted exploration cycle. To clarify the hydrocarbon potential in the block and thereby provide effective guidance for future exploration operations, in-depth researches were conducted based on the distribution of formations and sedimentary facies within the Chepaizi uplift to analyze oil sources, reservoir-cap rock assemblages and other reservoir conditions systematically. Research results show that the study area has favorable petroleum geologic conditions for hydrocarbon accumulation. As the final destination for long-term migration of hydrocarbons, the block has great hydrocarbon potential. Through correlation of oil sources and investigation on accumulation periods, the fault-blanket sandstone conductivity was determined, and the hydrocarbon accumulation model characterized by “hydrocarbons supplied by lateral sources, with faults providing vertical conductivity and blanket sandstones providing horizontal conductivity, and accumulated at blanket margins” was established. In accordance with these conclusions, drilling operations were successfully deployed, and a series of discoveries with commercial values were obtained.

Based on the analysis on sedimentary setting of the lower member of Xingouzui Formation in the Jiangling sag, the Jianghan Basin, and the comprehensive analysis with mud logging, coring and testing data, the sedimentary features and genetic model of shore shallow lake beach bar sands in the lower member of Xingouzui Formation in the southern slope belt of Jiangling sag and their controlling factors were discussed. It is considered that the beach bar sands are characterized by multi-phase development, vertical superimposition, lateral migration and contiguous distribution. They correspond to three types of genetic models, including lake wave, circulation and salt lake density current. The sedimentation of beach bar sands is controlled by paleo-base level cycle, paleogeomorgraphy and paleo-hydrodynamic force.

The Qintong sag in the North Jiangsu Basin is a typical minor faulted basin. Over years of exploration, undiscovered structural oil and gas reservoirs with high abundance have become less and less, but large lithologic reservoirs with low abundance are prospective for exploration. During the 12th Five-Year Plan, some new technologies and methods of sequence stratigraphy and seismic sedimentology were deployed to promote reserve discoveries in the Qintong sag. Among these discoveries, lithologic reservoirs took a relatively high proportion. For example, the overlapping and pinchout lithologic reservoir in the Ed-1 Member of the Shuaiduo-Chenjiashe area on the Western Slope Belt and two structural-lithologic reservoirs with reserves of ten million tons in the Yuduo-Huazhuang are and the Ef-3 Member of the Shuaiduo area were discovered successively. In addition, favorable signs were observed during exploration of lithologic reservoirs related to volcanic formations. Research results show that phase-controlling traps can be seen as the foundation, fault-sand body conductivity system as the key and preservation conditions as the core for the formation of lithologic reservoir in the Ed-1 Member . Moreover, the structural-lithologic reservoir in the Ef-3 Member are characterized by three controlling factors, i.e. near-source accumulation, control of phase belt, and conductivity of faulting systems. The research results may provide necessary guidance for future exploration operations. Exploration findings related to lithologic reservoirs in the Qindong sag made during the 12th Five-year Plan reveal that lithologic reservoirs in the Ed-1 and Ef-3 Members, together with those related to volcanic rocks, will remain as key exploration targets for lithologic reservoirs in the Qintong sag, North Jiangsu Basin.

The Chagan sag is one of sags that are highly explored in the Yingen-Ejina Banner Basin. Affected by volcanic rock and multi-stage tectonic activities, its geological conditions are complex, and its reservoir sands are thin and quickly change in lateral direction, which make it difficult to find high-quality reserves. Through comprehensive analysis of the petroleum geologic features in the Chagan sag, it is believed that the source rock distribution controls the oil and gas distribution – oil and gas are mainly distributed near source and around depression. The structure of the sag controls the dominant migration direction of oil and gas, the long-active faults provide effective channels for oil and gas migration, and the effective reservoir controls the oil and gas enrichment degree. Two hydrocarbon accumulation patterns are formed, i.e. self-generating and self-preserving type, and lower-generating and upper-preserving type. On this basis, fruitful exploration results have been achieved in the Chagan sag. For example, 3 hydrocarbon accumulation associations (upper, middle and lower) and 5 oil-bearing series are found and the Jixiang and Ruyi oilfields are proven.

Vibroseis is widely valued and applied by the industry due to its features of safety, environmental friendly and controllable frequency and energy. This paper presents a target-oriented, high-quality and efficient seismic exploration method, namely, variable slip time sweep (VSTS) and broadband exploration technology of low-frequency energy compensation. According to the special conditions of exploration areas with large-span buried depths of target formations and complex geological structures and surfaces, well-designed distribution and method of vibroseis operation were put forward, which is based on noise interference between vibroseises and surface conditions and for the purpose of high-quality imaging of reflection data. As a result, high-quality and efficient operation with vibroseis has been achieved. Favorable results have been obtained after the application in complex geological targets within some basins in West China.