The eastern segment of Alkin piedmont, northern Qaidam Basin, contains poor reservoir-seal assemblage and no effective source rocks, which are unfavorable for reservoir formation, making the oil and gas exploration very challenging in this basin. In this circumstance, deeper basic geological study was conducted and oil/gas reservoir forming conditions were re-analyzed. The results show that the eastern segment of Alkin piedmont exists under a background of paleo-uplift - paleo-slope structure, and has a composite conducting system of deep major faults and bedrock unconformity surfaces which connects the adjacent Lower Jurassic high - over mature source rocks. Moreover, the gneiss and granite in the basement with fractures and dissolution pores and vugs can serve as reservoirs, forming good reservoir-seal assemblage with the overlying Paleogene Luluhe Formation gypsum mudstone. Based on this understanding, a number of oil-bearing formations and blocks have been found by using proper logging, seismic and fracturing technologies, and the Dongping bedrock gas reservoir was discovered at the end of 2013 in the eastern segment of Alkin piedmont.

To analyze diagenesis of clastic rock in upper part of the 4^th member of Shahejie Formation (Es₄ ^s) in Bonan sag of Jiyang depression and its quantified influence on porous development and find favorable reservoirs, casting slices, scan electronic microscope and X-ray diffraction are used to study the relevant data. The results indicate that compactness, cementation, dissolution and metasomatism occurred in the clastic rock reservoir of Es₄ ^s in Bonan sag. Influenced by alkali fluid from early–stage gypsum and organic acid from latestage hydrocarbon source rock, the gypsum reservoir experienced the alkali and acid diagenetic environment. Controlled by the diagenetic environment, there were mainly cementing pores in the clastic rock reservoir in the early diagenesis and dissolving pores occurred in the middle diagenesis. Based on a large amount of analytic and testing data about different depths and horizons, the quantitative characterization method of pore development is established for the time being. The clastic rock reservoir in the low-level system domain, with development of secondary pores, is distributed in the southern and northern delta frontal area and eastern fan delta plain of Bonan sag, while the clasitc rock reservoir with development of primary pores is distributed on sandstone beach bar. The clastic rock reservoir in the high-level system domain, with development of secondary pores, is distributed in the end of the northern near-bank underwater fan and southern fan delta plain of Bonan sag, while the clastic rock reservoir with development of primary pores is distributed in the frontal area of fan delta.

As the 4th Member of Shahejie Formation(E₂s₄) shale in Damintun sag has got breakthrough in shale oil, this region has become the study hotspotfor shale oil.To analyze the influence factors for shale oil contents in E₂s₄ in Damintun sag is helpful forexploring accumulation conditions and distribution regularity of shale oil. On the base of core experiments, we analyzed geochemical, reservoir and oil content characteristics of E₂s₄ shale. By characterizing the ancient environment using trace elements, we proposed that the “warm and moist-occlusivelacustrine transgressive” ancient environment model was important condition forforming organic-rich shalein E₂s₄. Warm and moistclimate, occlusive deposit environment and rising water level promoted organic matter generation, accumulation preservation, respectively. By utilizing Rock-Eval method, we got shale oil contents. The results show that E2s4 shalehas high oil contents (0.08%-0.99%, average 0.43%). According to our studies, shale oil contents are influenced by hydrocarbon generation condition, reservoir condition and preservation condition. High organic matter abundance, appropriate high maturity, high brittleness mineral content, high quality of roof and floor, and formation overpressure are favorable conditions for shale oil enrichment and high oil contents.

A same reservoir may be repeatedly drilled in a vertical well in complex reverse fault-block reservoirs, making the geological modeling of these reservoirs one of the most troublesome modeling activities. Conventional reservoir geological modeling is incapable of characterizing the superimposed structures and reservoirs in reverse fault-block reservoirs, which will lead to an imprecise and unreliable reservoir geological model with distortion and reserve loss. Actual reservoir cannot be characterized by upscaled model due to formation and reserve losses. Accordingly, a series of technologies are developed to solve this technical problem, which principally include multiboundary technology, fault-isolation technology, rectangular corner-point grid system with full coverage of superimposed reservoir area and other reservoir numerical simulation upscaling technologies. An efficient solution is established to complete structure modeling and numerical simulation upscaling and other problems in the geological modeling of complex reverse fault-block reservoirs. Seismic structure interpretation, sedimentary facies, strata correlation, well and other data are comprehensively used in this solution to establish an precision Yingdong-1 reservoir geological model and the performance forecast model that is used to perform reservoir numerical simulation. Practical applications indicate that the matching rate between forecast production and 2-year actual production exceeds 95%.

The acquired seismic data are required to have high signal-to-noise ratio and resolution because the domestic exploration areas have large surface fluctuations, small deployment area, large buried depth of target layer, and thin layer. Based on the characteristics that the signal excited from the controllable vibrator is controllable, the research and test is conducted on single onshore controllable vibrator high-density acquisition. Meanwhile, it is also the first block for field test of low frequency multi-channel onshore seismic acquisition system. Based on the test results, this technology can effectively solve the problem that the channel capacity of present instruments and peripheral equipment are inadequate. Industrialized production by means of single controllable vibrator high-density acquisition is carried out for the first time at home. Meanwhile, this technology helps complete 3D seismic acquisition work in a number of blocks, achieving good geological results.

Wide application of high density and wide azimuth seismic acquisition technology has significantly improved the seismic exploration precision. High coverage density, small bin and point collection have become the development directions of seismic acquisition technology to obtain more accurate data. However, as for actual production, it is impossible to unlimitedly increase acquisition strength under the limitations of acquisition cost. How to obtain the optimized acquisition effect under the condition of limited cost is a widely-studied problem in the industry at the present time. With the analysis of acquisition bin of 3D high-density seismic data based on PSTB in a certain area of West China, it is considered that the accuracy of seismic data improved by small bin is based on the condition of high coverage density. Overemphasis on small bin size cannot necessarily obtain the data of a higher resolution under the condition of high coverage density. Appropriate increase of bin size can help improve the uniformity wave field and amplitude fidelity of data imaging, acquiring the data of higher precision.

In view of the poor complementation of frequency spectrum notch of OBC dual-sensor data, the differences in ghost and reverberation recorded by hydrophone and geophone have been analyzed from the perspective of receiving wave fields of OBC hydrophone and geophone, and it is recognized that reverberation is the cause of poor complementation of frequency spectrum notch between hydrophone data and geophone data. At the same time, analysis of hydrophone and geophone wavelet contaminated by reverberation at the different sea bottom reflection coefficients shows that when the sea bottom reflection coefficient increases, the hydrophone data frequency spectrum notch gets sharper, while the geophone data frequency spectrum notch gets weaker, therefore, the higher the sea bottom reflection coefficient, the poorer the complementation of frequency spectrum notch between hydrophone data and geophone data of the OBC dual-sensor data. For OBC data with poor complementation of frequency spectrum notch between hydrophone data and geophone data, dual-data combining method selected to attenuate ghost reflection of receiver points should not affect reverberation, the reverberation can be attenuated through deconvolution method after the combination of the hydrophone and geophone data. Simulated data and real data have proved that the processing method above is right.

In order to acquire seismic data as complete as possible and further improve the quality of cable-based seismic survey in offshore shoal area, the modes of acquisition, construction and line transfer have been adjusted depending on local conditions in offshore shoal areas. The results show that selective adoption of the improved and optimized modes can effectively mitigate the impacts of shoal area on cable-based seismic data acquisition. It is concluded that the new series of methods worked out through systematic study and innovation of the traditional acquisition, construction and line transfer modes can acquire more complete and higher quality data in offshore shoal area.

Well stimulation is necessary for the production of continental Yanchang shale gas in Ordos Basin in view of its low content of brittle minerals and high content of clay minerals. This paper discusses the feasibility of network fracturing based on the analyses of the technique, shale gas reservoirs, stress field and natural fractures. Taking Chang 7 Member of Yanchang Formation in Well J1 as an example, mini frac and net pressure matching are used for fracturing design and operation, and numerical simulation is used for parameter optimization. Microseismic monitoring shows that all perforation intervals have been effectively connected by the fracture network.

Based on the analysis of geological and accumulation characteristics, exploration & development history and single-well production of Vaca Muerta shale oil in the Neuquen Basin, Argentina, and the comparison with shale oil plays in North America, it is concluded that Vaca Muerta Formation is a set of high quality shale oil accumulation with wide distribution, large thickness, over pressure, good geochemical indexes, and moderate maturity. But its strong heterogeneity, big lithology change in vertical and lateral directions, intercalation of hard layers and weak layers, and lower quartz content, carbonate content of more than 40% in general, and medium reservoir quality would affect the fracturing effect to some extent, making the rock mechanics more complex. For the Vaca Muerta reservoir, the production and estimated ultimate recovery (EUR) of wells in structurally stable areas are significantly higher than those of wells in strike slip extensional areas, and it is inferred that the production of wells in condensate areas are higher than those of wells in oil generation areas. Still in the initial stage of exploration & development, Vaca Muerta Formation has much worse indexes of drilling cost, single-well production and EUR than North American shale oil plays. Its economical efficiency is poorer, but tends to be better through possible and proper treatments. The development of shale oil and gas in Argentina is still facing a series of challenges in aspects such as politics, economy, and supply of raw materials. Under the circumstances of low oil price, its commercial development will not be started for some time.