, Volume 36 Issue 4

    

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油气勘探
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  Distribution of petroleum enriched areas, Changling Sag, southern Songliao Basin

  Li Ming; Zhao Yimin; Liu Xiao; Zhang Yunmian and Wang Yushan

  , 2009, 36(4): 1730-0.

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  Changling Sag of the southern Songliao Basin is a terrestrial hydrocarbon-rich depression, and according to the “sag-wide oil-bearing theory”, oil and gas can be found in its whole effective source rock area. But prolific oil and gas areas that are usually called “sweet spots” are still controlled by several main factors in distribution. Fault belts above low uplifts and basement faults not only are the pathways allowing for hydrocarbon migration, but can form the lateral barriers of reservoirs, they are the main boundaries of oil and gas enriched areas. On the other hand, the fracture zone developed in the vicinity of the faults has improved the reservoir connectivity and increased the chances to obtain high production. These make the fault-developed zone itself become a “sweet spots” belt rich in oil and gas that should be paid more attention in exploration.
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  Distribution of hydrocarbon traps in volcanic rocks and optimization for selecting exploration prospects and targets in Junggar Basin： Case study in Ludong-Wucaiwan area, NW China

  Yang Hui; Wen Baihong; Zhang Yan; Zhang Guangya; Liu Zhizhou; Wu Fengcheng; Wei Yanzhao; Dai Xiaofeng and Hu Qinghui

  , 2009, 36(4): 1731-0.

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  Based on petrophysical, magnetic, gravity, electric, seismic and drilling data, combined with geological regularities, this paper proposed an integrated approach for the distribution prediction and lithology recognition of volcanic rocks, as well as the exploration prospect and target optimization of hydrocarbon deposits. The exploration technology was improved in the application to exploration in the Ludong-Wucaiwan area in Junggar Basin. Some important viewpoints are concluded as follows: aeromagnetic abnormal gradient belts correspond to volcanic faults, faults control the distribution of volcanic rocks and accordingly their local structures, aeromagnetic abnormal gradient belts correspond to highly-developed fracture zones and are prospective areas for volcanic reservoirs. The proposed integrated approach is proven effective by the exploration drilling results with high-flow gas wells.
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  Origin of Upper Triassic formation water in middle Sichuan Basin and its natural gas significance

  Li Wei; Yang Jinli; Jiang Junwei; Liu Jimin and Liu Zongcheng

  , 2009, 36(4): 1732-0.

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  The formation water of Upper Triassic Xujiahe Formation in the middle Sichuan Basin is of high salinity in most areas and of low to medium salinity locally. All the formation water lack sulphate ion implying good reducing and sealing conditions, but are rich in barium ion. The forming environment of the Xujiejhe formation water is similar to that of the Jurassic formation water, but very different from that of the underlying marine formation water. The Xujiejhe formation water has lower sodium (potassium) chloride coefficients and higher metamorphism coefficients. The water shows the characteristics of original continental sedimentary formation water reworked by later marine water of high salinity. In reworking the reservoirs, surface water of high sulphate ion content should be avoided, and also quick changes of formation temperature, pressure and chemical equilibrium should be avoided to prevent precipitates from blocking pores and throats.
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  Palaeogeomorphologic prediction of favorable zones: Take Fault ② of Qiongdongnan Basin as an example

  Jiang Hua; Wang Hua; Xiao Jun; Lin Zhengliang and Cai Jia

  , 2009, 36(4): 1733-0.

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  Palaeogeomorphology plays an important role in the development of sequences in the later filling stage of a sedimentary basin, and it also controls the pattern of the sedimentary system and its distribution. Using the measure of palaeogeomorphologic analysis, this paper identifies the types of slope breaks and paleo-ravines that are developed near the fault ② of the Qiongdongnan Basin, and classifies the types of the sedimentary systems controlled by the slope breaks. In the study area of Songtao High, a great amount of incised valley sedimentation is identified, from which the provenance is determined. The faults ② and ②-1 control the sediments infill in the area, and according to control pattern, the slope breaks can be divided into two types, bend slope break and fault slope break. Lowstand fans controlled by the slope break are the most favorable zone for oil and gas accumulation.
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  Development of mm-level mud-films and significance for reservoirs in Yingtai area, Daqing Oilfield

  Wang Haiqiao; Liu Guozhi and Chen Guoxun

  , 2009, 36(4): 1734-0.

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  Based on core observation, there are a lot of mud laminae (called mud-films, with thickness of 0.5-3 mm) developed in the Cretaceous siltstone in the western Yingtai area, Daqing Oilfield. Surfaces of most mud-films are not smooth, but grow with some sorts of micro-deformation structure, and some of them are penetrated by the silt up and down. The mud-films have strong vertical isolation due to their poor permeability. Therefore, under ideal circumstances, a steady mud film can isolate the upper and lower sandstone in its coverage entirely, and divide a set of sand body into two independent oil-water systems. The growth of many steady mud-films can increase the complexity of local oil-water distribution. Some frequently-developed small-scale or penetrated mud-films can obstruct the oil-water migration route inside a reservoir, playing a role in lowering the sandstone permeability. The main factor of the abundant growth of mm-level mud-films is the sedimentary background of the shallow delta with low angle in study area, and the development frequency of mm-level mud-films is closely related to the sedimentary microfacies and single-layer sand-body thickness. The mud-film development status in nearby area can be predicted by mud-film statistics from local corings.
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  Application of high-resolution sequence stratigraphy in improving the precision of reservoir prediction

  Li Jinsong; Zheng Xiaodong; Gao Zhiyong; Li Yonggen; Liu Ying and Li Xingli

  , 2009, 36(4): 1735-0.

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  On the basis of high-resolution sequence stratigraphy, this paper establishes a sequence stratigraphic frame, and predicts reservoirs by analyzing velocity field, seismic inversion, and seismic attributes. In the case study of the Jurassic Toutunhe Formation braided river delta reservoir of Shinan 21 well block, middle of the Junggar Basin, space variant velocity field inversion and reservoir prediction were carried out based on the sequence stratigraphic frame and the reservoir prediction accuracy was improved. Comparing the prediction results with the real drilling shows that, when the burial depth of bed of interest is 2 500 m, the maximum prediction error of depth is only 10 m, and the average relative prediction error is 0.16%; for appraisal wells with an average effective sandstone of 13 m, the maximum prediction error of sandstone thickness is only 5 m. The structure mapping and reservoir prediction constrained by the sequence stratigraphic frame achieved success.
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  Development and formation of Paleogene kaolinite, Bonan subsag

  Chen Xin; Zhong Jianhua; Yuan Jing; Nie Keke and Yang Yuping

  , 2009, 36(4): 1736-0.

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  In sandstone reservoirs, the development degree of kaolinite is related to reservoir properties and accumulation of oil and gas. Through core observation, thin section analysis, SEM, X-ray of clay mineral, core properties and oil-level test in Es3+ Es 4 of Bonan sub-sag, we studied the development characteristics and formation mechanism of kaolinite in deep clastic rocks. Kaolinite in deep clastic reservoirs is generated by corrosion of feldspar, and the kaolinite development is an important mark of good reservoirs and oil-saturated layers. Reservoirs of high kaolinite content have a good relationship with industrial oil layers. The formation of kaolinite in the study area has four stages, transformation from depositional kaolinite to illite, production of a large amount of authigenic kaolinite, kaolinite in oil layer being surrounded by oil and gas, and kaolinite being particularly high. The kaolinite in deep clastic reservoirs was formed in an acidic diagenetic field where acidic fluid and feldspar interacted, was kept in an inert diagenetic field formed by oil and gas filling, and was quickly transformed into illite and chlorite in an alkalescent diagenetic field.
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  Quantitative analysis of variation of organic carbon mass and content in source rock during evolution process

  Zhou Zongying

  , 2009, 36(4): 1737-0.

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  According to the mass conservation principle of organic carbon, a mathematical model of organic carbon mass compensation coefficient is established to indicate the variation of organic carbon mass. Considering the influence of organic carbon hydrocarbon generation, hydrocarbon expulsion and rock weight loss, a mathematical model for calculating changes in organic carbon content is also established. Forward method is used to simulate the compensation coefficient of organic carbon mass and the organic carbon content value of source rocks in different evolution stages and hydrocarbon expulsion efficiency. The compensation coefficient variation depends on organic matter type, maturity degree and expulsion efficiency. The maximum compensation coefficients of types Ⅰ, Ⅱ1 , Ⅱ2 and Ⅲ organic matter are 2.104, 1.360, 1.169 and 1.099, respectively. There exists a threshold value in hydrocarbon expulsion efficiency in source rocks, type Ⅰ is 20%, type Ⅱ1 is 30%, type Ⅱ2 and type Ⅲ is 60%. When the expulsion efficiency is less than this threshold value, the residual organic carbon content of the source rock is generally higher than the original organic carbon content; when the expulsion efficiency is greater than the value, the residual organic carbon content is generally lower than the original organic carbon content. Under the conditions of full expulsion, the maximum organic carbon reduction of types Ⅰ, Ⅱ1 , Ⅱ2 and Ⅲ muddy source rocks is roughly 43%, 20%, 10% and 10%.
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  Application of diplog data in sandstone reservoir architecture

  Liu Taixun; Xu Huaimin; Jiao Cuihua; Wang Haigeng; Chang Lunjie and Niu Yujie

  , 2009, 36(4): 1738-0.

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  Different-order reservoir architectures are identified by using the processing results of the diplog of long and short window lengths, which improves the accuracy of reservoir architecture research. Processing methods and parameters of diplog are discussed in the research on reservoir architecture. The diplog processing parameters of the Donghe sandstone in the HD4 oilfield are determined: window length is 0.2 m, step length is 0.02 m, and search angle is 35°. On the basis of diplog tadpole plot, the Donghe sandstone of coast deposit is classified into four kinds of 4th-order reservoir architectures, and twelve kinds of 3rd-order reservoir architectures, and twenty-four kinds of lithofacies units. The response characteristics on diplog of reservoir architecture interfaces and reservoir architecture elements are analyzed in detail. In the diplog tadpole plot, lithofacies units show as single vector model or vector combination, 3rd-order reservoir architectures correspond to a series of different vector groups, and the architecture bounding surfaces represent the interface of two different vector models. The research provides an accurate three-dimensional geologic model for numerical reservoir simulation.
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  Tectonic origin and structural styles in Tokar area, Red Sea Basin Wang Guolin

  Wang Guolin

  , 2009, 36(4): 1739-0.

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  As a younger rift basin developed from late Oligocene, Red Sea Basin possesses all necessary geological elements for hydrocarbon generation and accumulation concluded by integrated geological evaluation, though it has a low-degree of exploration and no commercial production. The Tokar area lies in the southern Sudanese Red Sea and is a part of the west flank of the middle section in Red Sea Basin. It experienced three tectonic evolution stages of rifting, stable and rifting, caused by twice large-scale tectonic movements. The early movement occurred in the end of Oligocene and generated basement-involved structures. The later one occurred in the end of Miocene and formed fault-slipped and salt-related structures. Totally seven structural styles have been identified as buried hill, drape anticline, pre-salt primary anticline, post-salt rollover anticline, post-salt drag anticline, salt-arched anticline and salt-sealed trap. According to the comparison of source, reservoir and seal rock as well as the traps’ size and reliability of all seven structural styles, the pre-salt primary anticline and post-salt drag anticline are the most favorable exploration targets.
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  Tectonic geology and exploration in the western escarpment of Fula sub-basin, Sudan

  Zhang Zhiwei; Pan Xiaohua; Wang Wangquan and Li Zhi

  , 2009, 36(4): 1740-0.

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  Fula sub-basin is a passive rift sag formed by the extensional stress resulted from Central Africa Shear Zone. It is an asymmetric half-graben, which develops fault steps to the west and is overlapped to the east. The western escarpment is a long and narrow structure of about 400 km2, controlled by a long-lived boundary fault. Due to complicated structure, steep stratum and varied sedimentary facies, there are many challenges for exploration in the escarpment, such as the seismic data acquisition and processing, integrated G&G study, drilling technology, etc. The integrated G&G study and exploration practice proved that the strategy of early deployment of 3D seismic acquisition and applying progressive exploration and development can efficiently decide reserves, reduce risks and enhance exploration benefits. Optimizing the seismic acquisition parameters and infilling shot points to improve the local fold times in the main part of the structure according to the conditions of subsurface and surface is beneficial to enhancing the seismic data quality. Timely adjusting the drilling technology can improve the drilling efficiency and the quality of borehole condition, which is helpful to discover pay zones and protect reservoirs.
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  Abnormally high pressure and hydrocarbon accumulation in the lower Kura Sag, South Caspian Basin

  Duan Haigang

  , 2009, 36(4): 1741-0.

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  South Caspian Basin is a backarc rift and foreland combination basin developed in the Mesozoic and Cenozoic. The lower Kura Sag in the basin is characterized by great thickness and rapid sedimentation, abnormally high formation pressure, widespread mud volcanos, and low heat flow and formation temperature. This paper studies the forming condition and distribution feature of the abnormally high pressure in the lower Kura Sag and its effects on hydrocarbon accumulation. Its formation is related to tectonic compression; mud volcanism; widely thick, rapid, plastic sedimentation; and massive clays with smectite. Thermal expansion, hydrocarbon generation and clay dehydration contribute little to the high pressure formation. Formation pressure is universally higher in Lower Kura than that in China’s basins, with pressure coefficient up to 2.14 in 2 412 m. Compaction trend lines of under-compaction clay in different structures are various because of different lithology, according to which the abnormal clay compaction is divided into 3 types. Abnormally high pressure is favorable for reservoirs preservation and formation of structures and traps, controls hydrocarbon distribution, but also causes severe engineering problems.
油气田开发
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  Laboratory researches on deep fluid diversion agent with high strength and retarding swelling characteristics

  Pan Xiaohua; Luo Man; Zhang Chunlei; Tang Xiaofen; Liu Yuzhang; Yang Limin; Wei Falin; Ma Tao and Ma Hongwei

  , 2009, 36(4): 1742-0.

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  Macromolecule networks were introduced into the networks of normal sopping swelling materials by redesigning the materials molecule structure, and thus forming materials with the characteristics of retarding swelling, high strength and the structure of interpenetrating networks. The microscopic structure of the materials was analyzed by TEM and SEM, and the homogeneous structure of interpenetrating networks was observed from TEM and SEM images. Its static water absorption performance and mechanical performance after water absorption indicate that the total swelling time of the retarding swelling particles, which can be suspended and dispersed in water, is more than 20 days. After swelling, the modulus of elasticity (G′) of the sample is over 104 Pa, higher than that of the general swellable particle diversion agent. The excellent deep part injection and plugging performances were confirmed by physical simulation experiments. These performances overcome the shortcomings of quick swelling, low strength and less placement depth.
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  Simulation of fluid-solid coupling during formation and evolution of high-permeability channels

  Feng Qihong; Qi Junluo; Yin Xiaomei; Yang Yong; Bing Shaoxian and Zhang Benhua

  , 2009, 36(4): 1743-0.

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  A fluid-solid coupling mathematical model is established to describe the evolution of high-permeability channels. The model consists of the dynamic evolving model of permeability and the fluid flow equation. The dynamic evolving model of permeability, indicating the relationship of cumulative liner flow rate and permeability, reflects the evolution process of high-permeability channels. On this basis, corresponding solution software was developed. Through simulation and calculation of a positive rhythm conceptual model, conclusions are as follows: high-permeability channels gradually develop with the increase of water cut; high-permeability channels exist mainly in areas close to well bores and along the main stream lines, and develop at the bottom of positive rhythm reservoir; high-permeability channels can develop more easily if permeability differential increases; the unbalance between injection and production leads to the development of high-permeability channels. The developing process and characteristics of high-permeability channels were simulated practically for Ng35 channels in well site 30NB20 in Gudao Oilfield, Shengli, and the effect of profile control on the corresponding injection wells testified the existence of high-permeability channels and also the reliability of this method.
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  A calculation of cuttings lag time for foam drilling

  Xu Hanbing; Li Xiangfang; Li Yunbo; Lei Zhengdong and Sui Shengli

  , 2009, 36(4): 1744-0.

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  The calculation accuracy of cuttings lag time is an essential factor for reservoir information reflection accuracy when drilling with foam. A cuttings lag time calculation model is established based on principles of foam rheology and the liquid-solid two-phase flow theory. Sectionalized integration method and multiple iteration method are introduced into this issue, based on which a calculation method of cuttings lag time for foam drilling is formed. With this method, some key factors’ sensitivities are simulated and analyzed. It is revealed how gas injection rate, foam quality and cuttings equivalent diameter influence the cuttings lag time. Under high foam quality condition, the sensitivity of the cuttings lag time to gas injection rate is large when gas injection rate keeps a small value, while the sensitivity of the cuttings lag time to cuttings equivalent diameter is small when the cuttings equivalent diameter keeps small. The results also show that there is a critical value for the effect of foam quality on the cuttings lag time.
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  Technologies for improving producing degree of low permeability carbonate reservoirs

  Zhao Lun; Fan Zifei; Song Heng; Li Jianxin and Cai Dongmei

  , 2009, 36(4): 1745-0.

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  Zanarol is a giant carbonate oil field with low permeability and high heterogeneity reservoirs. The reservoir pressure drops quickly and the production declining rate increases due to the previous depletion development and fast production after CNPC engaged in. Based on producing tests, the reservoirs can be classified into four types according to producing and injection intensities, better producing, good producing, lower producing and no producing, and over 50% reservoirs have no or lower production. Improving producing degree and water flooding effect is the orientation for next development adjustment. Several measures for improving producing degree are implemented, including separate zone producing, separate zone fracturing stimulation, separate zone water injection, well pattern infilling, and gas lift, as well as increasing plane sweep efficiency by ameliorating correlation between injection and production and increasing vertical sweep efficiency by stimulating zones with lower production. After 3 years of application, the production declining rate of main pools decreases by 10%, the producing degree increases by 12%, the recovery factor increases by 4.3%, and the water flooding development improves greatly.
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  Streamline numerical well-testing interpretation model and pressure response for partially perforated wells

  Yao Jun and Wu Minglu

  , 2009, 36(4): 1746-0.

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  A streamline numerical well-testing interpretation model for partially perforated wells was established that includes a filtration mathematical model of production period and a streamline mathematical model of testing period. Pressure response characteristic curves for partial perforated wells were obtained by solving the models of the two periods using streamline method and finite difference method, respectively. Pressure response characteristics for partially perforated wells were obtained by analyzing synthetically the streamline distribution and the pressure response characteristic curves. Two horizontal straight line segments will emerge in the derivative curve. The influence of permeability ratio, perforation thickness ratio and perforation location on pressure response was investigated. The larger the permeability ratio is, the earlier the second horizontal straight line segment will emerge. The less the perforation thickness ratio is, the greater the distance between the two horizontal straight line segments will be. The impact of perforation location on pressure response is little. Permeability ratio and perforation thickness ratio have significant effects on the pressure response and they must be taken into account in well-testing interpretation for partially perforated wells.
石油工程
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  Application and prospect of bionic non-smooth theory in drilling engineering

  Gao Ke; Sun Youhong; Gao Runfeng; Xu Liang; Wang Chuanliu and Li Yumin

  , 2009, 36(4): 1747-0.

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  Bionics is a subject which can interact with many disciplines including the drilling engineering. On the basis of analyzing the properties of bionic non-smooth surface, the non-smooth theory is applied in the bit design to develop the bionic diamond bit. The dung beetle is selected as bionic prototype in this paper to design the working layer of an impregnated diamond bit, which makes the bottom surface always keep the same non-smooth shape and makes the bionic bit maintain a high penetration rate and long-life to underline their high efficiency, wear and resistance reduction properties. Tests show that the bionic bit improves the drilling speed and lifetime by 44% and 74%, respectively, compared with a common bit. In addition, the bionic non-smooth surface structure has an extensive application prospect in drilling engineering, due to its properties of wear, anti-sticking and resistance reduction. It can be applied to improve the wear performance of bit, pipe joint, cylinder liner and piston of mud pump, and to solve the bit balling and reduce the resistance of spiral drills and impact spearhead.
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  Influential factors for the design of ultra-deepwater drilling risers

  Chang Yuanjiang; Chen Guoming; Xu Liangbin and Liu Jian

  , 2009, 36(4): 1748-0.

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  Environmental and operational factors are the main factors affecting the design of ultra-deepwater drilling risers. The former includes water depth, wave, current, and the latter includes drilling fluid density, hang-off mode after disconnection, buoyancy modules distribution, and vortex-induced vibration (VIV) suppression devices. This paper described the factors affecting the design of the ultra-deepwater drilling risers, identified the influential mechanism of these factors, and analyzed the influences qualitatively or quantitatively. Water depth and current are the most significant influencing factors. The material, structure and configuration of the drilling riser change with the increase of water depth. Current can cause vortex-induced fatigue in the riser, and cause difficulty in drilling riser installation and retrieval. Hangoff mode affects the buoyancy factor and the distribution of buoyancy modules. VIV suppression device causes difficulty in riser operation, and the density of drilling mud affects the flex joint angle and effective tension, and thus affecting the stability of the drilling riser system.
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  Fracturing control method for deep volcanic rock gas reservoirs in Daqing exploration area

  Zhang Guoliang; Lan Zhongxiao and Liu Peng

  , 2009, 36(4): 1749-0.

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  Pores, cavities and fractures are well-developed in deep volcanic reservoirs. The simultaneous break and extension of multi-fractures in treatment caused early stage sand-block, low fracturing success ratios, small treatment scales, and bad stimulation results. Based on the geologic characteristics of the deep volcanic rocks, this paper establishes a fracturing break and extension model of volcanic rocks, introducing with time-relevant leaking factor, peak factor and modulus factor. The model is used to better describe the process of initiation and extension of major fractures and micro-fractures. On this basis, the evaluating method for the “three highs” of pump off pressure gradient, near well friction resistance and leakoff coefficient is studied, and through field practices, integrated processing measures are formed: use rubber plugging to deal with near-well high friction resistances, use silts to seal natural fractures, adjust prepad fluid ratios, and inject multi-section silt slugs. The success ratio of volcanic rock gas reservoir fracturing is raised to 90.0% from the past 36.0%.
资源评价与管理
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  Investment optimization in oil and gas plays

  Zheng Yuhua and Luo Dongkun

  , 2009, 36(4): 1750-0.

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  A model was established to illustrate the relation between cumulative exploration investment and growth of total proved reserves on the basis of growth model of total proved reserves. The Data Envelopment Analysis (DEA) theory was used to give an optimal solution of the function of constructed productivity and development investment, and, together with an exponential oil & gas operational cost function, a model of the relation between development investment and oil & gas output was deduced. Based on the models of investment-exploration-development relations, and considering maximum profit, yield component, reserves-to-output ratio and production rate, an optimal function of multi-stage investment was established, which can result in multi-stage investment structure under given conditions with genetic algorithms. The method can provide scientific basis for oil companies to make a long-term strategic program and investment plan in oil and gas exploration and development, decrease the subjective blindness in the investment and bring about a reasonable and orderly exploration and development of oil and gas resources.