, Volume 40 Issue 1

    

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油气勘探
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  Large-scale accumulation and distribution of medium-low abundance hydrocarbon resources in China

  Zhao Wenzhi; Hu Suyun; Wang Hongjun; Bian Congsheng; Wang Zecheng and Wang Zhaoyun

  . 2013, 40(1): 2-0.

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  This paper analyzes the large-scale accumulation conditions and distribution characteristics of medium-low abundance hydrocarbon resources in China. Large-scale development of accumulation elements and their change in scale are the material basis of large scale oil and gas accumulation, determining the regional nature of oil and gas distribution. Liquid hydrocarbon dispersed in marine source rocks being cracked to form a large volume of gas and coal measure source rocks expelling gas during uplift are two important factors for the formation of large-scale hydrocarbon accumulation, which control the scale of source rocks that enter the main gas-generating stage. Volume flow and diffusive flow are the main migration-accumulation mechanism for the large-scale hydrocarbon accumulation, which ensures the sufficiency of hydrocarbon supply. Pancake, layer-like, and cluster are three main accumulation forms of large-scale hydrocarbon accumulation, which ensure the scale of hydrocarbon accumulation. Middle to low abundance hydrocarbon resources are characterized by near-source distribution, main-body play, late accumulation stage and single accumulation type. The periclinal area of palaeo-highs in marine craton basins, the lower slopes and sags in an intra-continental depression basin, and the gentle slopes of foreland basins are the most likely areas for the development of large-scale hydrocarbon accumulation, and they have two types of accumulation, large area and large scope. The proposal of the large-scale accumulation of middle to low abundance hydrocarbon resources in China improves the hydrocarbon discovering potential in middle to deep layers of superimposed basins and in the lower slopes and sags in depression basins, enlarges the exploration scale, and extends the hydrocarbon exploration from local second-order structure zones to the whole basin with the main source rock as the center, and from middle layers to deep, even super-deep, layers.
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  Formation mechanism, geological characteristics and development strategy of nonmarine shale oil in China

  Zou Caineng; Yang Zhi; Cui Jingwei; Zhu Rukai; Hou Lianhua; Tao Shizhen; Yuan Xuanjun; Wu Songtao; Lin Senhu; Wang Lan; Bai Bin and Yao Jingli

  . 2013, 40(1): 2-0.

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  As an important type of “conventional–unconventional orderly accumulation”, shale oil is mature oil stored in organic-rich shales with nano-scale pores. This paper analyzes and summarizes elementary petroleum geological issues concerning continental shale oil in China, including sedimentary environment, reservoir space, geochemical features and accumulation mechanism. Mainly deposited in semi-deep to deep lake environment, shale rich in organic matter usually coexists with other lithologies in laminated texture, and micron to nano-scale pores and microfractures serve as primary reservoir space. Favorable shale mainly has typeⅠand ⅡA kerogens with a Ro of 0.7% –2.0%, TOC more than 2.0%, and effective thickness of over 10 m. The evolution of shale pores and retained accumulation pattern of shale oil are figured out. Reservoir space, brittleness, viscosity, pressure, retained quantity are key parameters in the “core” area evaluation of shale oil. Continuously accumulated in the center of lake basins, continental shale oil resources in China are about 30×108–60×108 t by preliminary prediction. Volume fracturing in horizontal wells, reformation of natural fractures, and man-made reservoir by injecting coarse grains are some of the key technologies for shale oil production. A three step development road for shale oil is put forward, speeding up study on “shale oil prospective area”, stepping up selection of “core areas”, and expanding “test areas”. By learning from marine shale breakthroughs in North America, continental shale oil industrialization is likely to kick off in China.
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  Detailed assessment of a single-combination oil-gas accumulation zone in a mature exploration basin, China

  Niu Jiayu; Jiang Xuezhu; Liu Haitao; Jiang Lingzhi and Wu Xiaozhou

  . 2013, 40(1): 2-0.

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  As some basins or blocks in China, especially old oil and gas fields, have already entered the mature or highly mature stage in exploration, the old traditional assessment method that treats “complex horizons” as a whole part can not meet the high resolution and precision requirements for detailed exploration in these areas. By comparing oil-gas evaluation systems at home and abroad and considering the evaluation method for “play” abroad, a single-combination assessment method for oil and gas accumulations in high matured exploration basins were put forward. The new method, composed of geological evaluation, resources estimation and target selection, focuses on conducting a division of the assessment horizon based on a combination of a regional/sub-regional seal and its corresponding reservoirs and hydrocarbon-supplying area, confirms the test results of drilled wells and the distribution of known reservoirs, and depicts boundaries of every key geological element. Finally, these preliminary maps of key elements are overlapped to figure out the scope and type of favorable exploration targets, hydrocarbon-supplying system, channel types, charge capacities, and the most favorable prospective traps. Detailed exploration practices in Qikou depression, Bohai Bay Basin, show this evaluation method works well.
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  Medium-deep clastic reservoirs in the slope area of Qikou sag, Huanghua depression, Bohai Bay Basin

  Pu Xiugang; Zhou Lihong; Wang Wenge; Han Wenzhong; Xiao Dunqing; Liu Haitao; Chen Changwei; Zhang Wei; Yuan Xuanjun; Lu Yi and Liu Sa

  . 2013, 40(1): 2-0.

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  To get a better understanding of the distribution pattern of favorable reservoir belts in the medium-deep clastic rocks in the Qikou sag of the Huanghua depression, and find out premium reservoir zone, the characteristics and controlling factors of the medium-deep reservoirs in the Qikou sag were analyzed. Comprehensive study into the structural setting, provenance, depositional system, and reservoir properties shows that the Paleogene in the Qikou sag has multi-sags and multi-slopes, with slopes accounting for over 70% of the total sag area. A number of large braided river (fan) delta front - gravity flow sand bodies matching with multi-slope zones lay a good material foundation for the formation of medium-deep effective reservoirs there. Generally buried at over 2500 m, the medium-deep clastic rocks are mainly lithic feldspathic sandstone, with secondary pores and cracks as major reservoir space. Being in the medium diagenesis evolution stage, the medium-deep clastic rocks in the Qikou sag span over a large depth. Nine major factors affecting reservoir properties have been identified by mathematical geology. Although the medium-deep clastic rock interval is poor in physical properties and complex in pore structure, high sedimentation rate, medium geothermal field, high fluid pressure, high feldspar content, relatively high dissolution rate and early oil and gas charge have given rise to three to four belts with abnormally high porosity in it, which are all favorable hydrocarbon reservoir zones.
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  Low-amplitude structures and oil-gas enrichment on the Yishaan Slope, Ordos Basin

  Wang Jianmin and Wang Jiayuan

  . 2013, 40(1): 2-0.

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  Considering the geological and tectonic characteristics and based on drilling data and production test results, a drawing method with a dense well pattern and large scale was used to analyze the low-amplitude structures and oil-gas enrichment in the Yishaan slope, Ordos Basin. Low-amplitude structures are developed regionally and intensively, extended directionally in array folding, and evolved inheritedly. Based on geometry, coverage and genesis, the structures are divided primarily. With tectonic stress as the driving factor, the low-amplitude structures contain basically nose-like units, in nearly E-W trend. The fluctuating attitude of strata at the break affects the driving force, speed and direction of oil-gas migration along the updip of the slope, making oil/gas/water differ in sections and oil/gas dissipate or cluster locally, so that the alternating oil-gas areas and the oil-water areas with more water are formed. A series of composite traps (lithologic-structural, structural-lithologic or stratigraphical-structural) are defined by combination of the endpoint connecting line of hinge zone in low amplitude tectonic slope break with the lithology or property pinch-out line of sedimentary facies belt side parts, or with local strata pinch-out line. In such traps, the hydrocarbons are accumulated. The advantageous configuration of low-amplitude structures and large sedimentary systems as well as favorable facies controls the oil and gas distribution in Mesozoic – Paleozoic formations in the Yishaan slope.
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  Microstructural characteristics of the Cretaceous Qingshankou Formation shale, Songliao Basin

  Huang Zhenkai; Chen Jianping; Xue Haitao; Wang Yijun; Wang Min and Deng Chunping

  . 2013, 40(1): 2-0.

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  To research the characteristics and petroleum geological significance of micro pores, this paper uses Second Electron Microscope (SEM) and secondary SEM imaging capability in Field Emission SEM (FE-SEM) to characterize shale from the first member of the Cretaceous Qingshankou Formation, Songliao Basin. There are five major pore types in the shale, including matrix intercrystal, organic, dissolution, interparticle, and intracrystalline pores. In addition, there are a mass of micro-fractures of micron-submicron (nano-) scale, including dissolution, filled and interlayer fractures. The existence of complex fracture-pore systems provides an effective pathway for primary migration and it also provides ample storage space for the residual petroleum in shale, which is important for the primary migration and storage for shale oil and gas resources.
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  Kinematic classification, structural modeling and prospective fields of the foreland thrust belts in Midwest China

  Guan Shuwei; He Dengfa; Lei Yongliang and Chen Zhuxin

  . 2013, 40(1): 2-0.

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  According to the distribution and transfer directions of thrust displacements under which the size, shape and pattern of thrust belt are controlled, the foreland thrust belts are classified into four types in middle and western China: (1) Type I, all the fault displacements in the thrust belt transfer from the mountain front to the basin along detachment. This type is the most popular in central and western China and can be divided into three subtypes: Kuche type, southwestern Sichuan type and Jiuquan type. (2) Type II, represented by southern Junggar Basin, in which there are fault displacements transferring to both basin and orogenic belt directions. (3) Type III, represented by Fusha thrust belt in southwestern Tarim Basin, in which all the fault displacements transfer toward the mountain front as deep structural wedges propagating toward the basin direction. (4) Type IV, represented by southwestern and northern Qaidam Basin, in which the transfer of fault displacements is restrained by the size, shape and boundary of the basin, and the stable foreland part and typical wedge sedimentary structure not produced. On basis of the above four types and the modeling of complicated structures, four new exploration areas are identified: the deep imbricate structural wedges in southern Junggar Basin, late Paleozoic passive continental margin sequence under the reverse Cambrian nappe in northwestern Sichuan, under-coal structures in middle and eastern Kuche, and footwall covered structures in northwestern Junggar Basin.
油气田开发
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  Well type and pattern optimization technology for large scale tight sand gas, Sulige gas field

  He Dongbo; Jia Ailin; Ji Guang; Wei Yunsheng and Tang Haifa

  . 2013, 40(1): 2-0.

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  Sulige gas field is a typical tight sand gas field in China. Well type and pattern optimization is the key technology to improve single well estimated reserves and recovery factor and to achieve effective field development. In view of the large area, low abundance and high heterogeneity of Sulige gas field, a series of techniques have been developed including hierarchical description for the reservoir architecture of large composite sand bodies and well spacing optimization, well pattern optimization, design and optimization for horizontal trajectory and deliverability evaluation for different types of gas wells. These technologies provide most important technical supports for the increases of class I and II wells proportion to 75%–80% with recovery factor enhanced by more than 35% and for the industrial application of horizontal drilling. To further improve individual well production and recovery factor, attempts and pilot tests in various well types including side tracking of deficient wells, multilateral horizontal wells, and directional wells, and horizontal well pattern and combined well pattern of various well types should be carried out throughout the development.
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  Current development and application of chemical combination flooding technique

  Zhu Youyi; Hou Qingfeng; Jian Guoqing; Ma Desheng and Wang Zhe

  . 2013, 40(1): 2-0.

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  Great success has been achieved in the fundamental study and field test of chemical combination flooding in recent years. In China, a low concentration ASP formula is employed to achieve ultra-low interfacial tension by the synergistic effect of alkali and surfactant. The viscosity of polymer solution made from produced water can meet the technological requirement when salt tolerance polymer is applied. ASP or SP flooding can increase oil displacement efficiency and enlarge the sweep volume simultaneously. ASP pilot test and industrial field test in Daqing Oilfield have resulted in an oil recovery ncrease of 18.5%-26.5%. The chemical combination flooding has entered into the industrial promotion and application stage, with a series of supporting techniques formed in the field tests. The main challenges in this technique include short pump-checking period and difficulty in produced liquid handling and high cost. Micelle-polymer flooding as the major chemical flooding technique was applied abroad in the early stage of chemical flooding test. However, the micelle-polymer flooding has not been applied widely due to its high cost. With the rise of oil price in recent years, low concentration chemical combination flooding has drawn more attention. Because of high temperature and high salinity in most reservoirs abroad where chemical combination flooding is used, high performance temperature and salt tolerance oil displacement agents are the bottleneck for future chemical flooding.
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  Horizontal well, nitrogen and viscosity reducer assisted steam huff and puff technology: Taking super heavy oil in shallow and thin beds, Chunfeng Oilfield, Junggar Basin, NW China, as an example

  Wang Xuezhong; Wang Jinzhu and Qiao Mingquan

  . 2013, 40(1): 2-0.

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  Chunfeng Oilfield in the Junggar Basin has shallow burial depth (400–570 m), low formation temperature (22–28 ℃), thin reservoirs (2–6 m, averaging 3.5 m), high underground crude oil viscosity (50 000–90 000 mPa·s), but high sensitivity to heat, it is suitable for thermal recovery. In view of these features, a development method for this oilfield combining horizontal well, viscosity reducer, nitrogen and steam flooding (HDNS) was put forward, and pilot test was carried out in Northern Pai 601 sand body. The results show: injecting nitrogen through annulus can insulate thermal, high expansibility of nitrogen works to compensate formation energy, and nitrogen overlapping in reservoir has insulation effect. The combination effect of all parts of HDNS significantly increased steam sweep volume, oil displacement efficiency and crude oil flow ability, and reduced oil viscosity. Thanks to this technique, Chunfeng Oilfield has built up a production capacity of 40×104 t, with an oil recovery rate of 3%, marking the successful high-speed and high-efficiency development of low-grade shallow thin super heavy oil.
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  A new method for calculating volumetric sweep efficiency in a water-flooding oilfield

  Hu Gang

  . 2013, 40(1): 2-0.

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  On the basis of Zhang Jinqing’s water drive characteristic curve and the basic principle of material balance, and using displacement efficiency expressions of water flooding, volumetric sweep efficiency expressions of water drive and the relationship between average water saturation and exit-end water saturation, this paper deduce the theoretical relationship formulae between displacement efficiency, volumetric sweep efficiency and water cut in a water-flooding oilfield, and puts forward a new method to calculate displacement efficiency and volumetric sweep efficiency with dynamic data in a water-flooding field. A case study shows when water cut is 100%, the volumetric sweep efficiency calculated with Zhang’s water drive characteristic curve is 99.7%, and that calculated with Sipachev’s water drive characteristic curve is 100%, which proves that the method with Zhang’s water drive characteristic curve can more accurately reflect the actual field situation, and is more rational. Study shows the method is simpler, more efficient and cost-saving than conventional core test, reservoir engineering and numerical simulation methods, moreover, it overcomes the narrow application scope of the aforementioned methods.
石油工程
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  Research and preparation of ultra-heavy slurry

  Zhou Shiming; Li Gensheng and Wang Qichun

  . 2013, 40(1): 2-0.

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  In order to resolve the technical problem of cementing when drilling super high-pressure gas layers or saltwater layers of Guandu structure in Chishui region, Guizhou province, an ultra-heavy slurry was developed by optimizing weighting materials and designing particles, and applied to well Guanshen1 for liner cementing. According to the needs of preparing ultra-heavy slurry, the weighting additive MicroMAX in spherical particles was selected and combination of weight additives—reduced iron powder, iron powder, MicroMAX—was chosen for optimization. The particle size-distribution of the slurry was designed on the basis of the theory of tight packing, and the actual particle size-distribution is close to the ideal condition of tight packing. The ultra-heavy slurry with a density of 2.70-3.00 g/cm3 was designed, which is good in basic performance, flow ability and stability. In the simulated mixing test on the ground, a slurry with an average density of 2.71 g/cm3 was prepared by using conventional one-time cementing process. In the liner cementing of well Guanshen 1, the slurry with a density of 2.80 g/cm3 was used to successfully seal the super high-pressure saltwater layer: the average density of the slurry pumped into well was 2.78 g/cm3 and the maximum density was 2.82 g/cm3; amplitude log showed that the cementing quality was good; the well bore kept stable in follow-up drilling when the density of drilling fluid was reduced from 2.77 g/cm3 to 2.00 g/cm3.
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  Impacts of ocean current and seabed friction on the picking-up and laying-down processes of oil and gas pipelines

  Lun Guande; Liu Yancong; Yi Peng; Li Chengkai; Ma Xiaoli and Qu Yang

  . 2013, 40(1): 2-0.

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  Based on engineering practice of the picking-up and laying-down processes of offshore pipelines, a finite element model was established. On the basis of the model, methods and steps of the picking-up and laying-down operations were determined, and the impacts of currents and seedbed friction on the two operations were studied. The shape and stress distribution of the pipeline under the influences of longitudinal current, lateral current and seabed friction when picked up and laid down were analyzed using finite element analysis software. The results show that the longitudinal current has almost no effect on the pipeline shape and stress distribution in the picking-up and laying-down processes, while the lateral current results in significant deformation of the pipeline in the horizontal plane and raises the overall stress level of the pipeline. The friction between the seabed and the pipeline impedes the lateral displacement of the pipeline when it is laid down. The rougher the seabed, the smaller the overall lateral displacement of the pipeline is. When the pipeline reaches the equilibrium state after it is laid down, the friction between the pipeline and the seabed becomes larger with the increase of the friction coefficient.
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  Vibration test and assessment for an ocean drilling rig derrick: Taking the ZJ50/3150DB drilling rig as an example

  Hu Jun; Tang Yougang and Li Shixi

  . 2013, 40(1): 2-0.

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  The rig derrick of a ZJ50/3150DB drilling rig in an offshore jacket platform located in the Bohai bay vibrates obviously when drilling. In order to assess the safety of the derrick when drilling, vibration test for the derrick was carried out and a finite element model of the derrick was built to analyze the impact of vibration on the derrick’s structure safety, in combination of the field test data with the calculation results got using the model. Natural frequency, amplitude-frequency response when drilling, vibration amplitude and vibration acceleration of the derrick were tested. Based on the derrick drawing and field situation, the finite element model of the derrick structure was built using ANSYS software. The first-order natural frequency of the derrick calculated using the model was 0.555 8 Hz, which coincided with the filed test data and proved the validity of the model. The analysis of the field test data and the calculation results, show, the derrick is resonance-prone when the rotation speed of the top drive is 36 r/min, the derrick C-style opening has low torsional strength, the two front brace rods of the derrick substructure are crucial components that concern the derrick safety, and derrick vibrations under different working conditions and shock vibration happening when the top drive passing by the monkey board meet safety requirements.
综合研究
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  Prediction of apparent viscosity of non-Newtonian water-in-crude oil emulsions

  Wang Wei; Wang Pengyu; Li Kai; Duan Jimiao; Wu Kunyi and Gong Jing

  . 2013, 40(1): 2-0.

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  On the basis of the effective medium theory and the classical viscosity prediction model proposed by Pal et al, the apparent viscosity and rheological properties of the water in crude oil emulsion with natural surface active components such as asphaltene and resin are predicted. The adsorption and entrainment of continuous phase by the surfactants molecular, which leads to the increment of effective water fraction, is the inducement of Non-Newtonian behavior in the bulk emulsion. The two actions of promoting and counteracting effects on the effective water fraction are considered separately and represented by Water Fraction Factor and Particle Reynolds Number Factor respectively. The Water Fraction Factor takes into account the positive effect of water fraction and drop size distribution in microscope, while the Particle Reynolds Number Factor reflects the negative effect of shear rate at different drop size. A new prediction model taking the influence of nearly all factors such as drop size distribution, shear rate, water fraction into consideration was built. Measured viscosity of emulsion of the crude oil and water from an oilfield was used to verify the predicted results of the model, which proves that the new model is high in accuracy with a maximum relative error of 11.44%.
学术讨论
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  About origin of tight sandstone gas: To discuss with Academician Dai Jinxing

  Yin Feng; Liu Ruobing and Qin Hua

  . 2013, 40(1): 2-0.

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  Tight sandstone gas belongs to unconventional natural gas. There is no unanimous agreement about the source of tight sandstone gas source. Both the Yuanba and Tongnanba gas fields in the Sichuan Basin produce tight sandstone gas from Xujiahe Formation gas reservoirs. The geochemical data such as the carbon and helium isotopes of the 14 gas samples from the Xujiahe Formation of 9 wells in the Yuanba gas field show that the gas mainly consists of coal-derived gas from the self-source type, oil-type gas from other source, and a small amount of abiogenic gas, suggesting combination gas sources. The similar geochemical data of 5 gas samples from the Xujiahe Formation of 5 wells in the Tongnanba gas field indicate that the gas consists of oil-type gas from other source, accompanied by a small amount of abiogenic gas, also being of mixed origins. Therefore the Xujiahe Formation tight sandstone gases of the Yuanba and Tongnanba gas fields do not come from coal measure alone. They have a variety of sources, mainly the coal-derived gas or oil-type gas of organic origin or the mixture of them.