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  Latest Printed Issue  

2008  Vol.29 Number 5
Sept. 25, 2008

Content is this issue
  PETROLEUM EXPLORATION
  OIL FIELD DEVELOPMENT
  PETROLEUM ENGINEERING
 
 
 
 
PETROLEUM EXPLORATION
 
 


633
JIANG Youlu LI Zongliang TAN Yuming CHANG Zhenheng ZHUO Qingong
  Research on history of gas migration and accumulation in fault basin：
Taking Wen 23 Gas Field of Dongpu Depression as an example
    The history of gas migration and accumulation includes the origin, migration pathways, charging process, charging history of natural gas and the matching relations of the main factors for hydrocarbon accumulation. Taking Wen23 Gas Field in Dongpu Depression as a case, the dynamic processes of hydrocarbon generation, migration, accumulation and preservation of natural gas were discussed based on the comprehensive research of petroleum geology and test data. The natural gas in this area is mainly from the coalsource rocks of the PermoCarboniferous system in Qianliyuan subdepression. The coalformed gas migrated along the Wendong fault firstly to the sandstone in the fourth member of Shahejie Formation and then along the high porosity and highpermeability zone of sand body towards the northwest. The coalformed gas continuously accumulated in the favorable place of the fourth member of Shahejie Formation reservoir in the period from the first member of Shahejie Formation depositional stage to the late of Dongying Formation. The original gaswater interface is about 10 m lower than that of gas reservoirs at present, which indicates that natural gas in the fourth member of Shahejie Formation reservoir of Wen23 Gas Field dissipated in the last stage of the Dongying movement to some extent.
    2008 Vol. 29 (5): 633-638 [Abstract ] ( 172 ) [HTML 0KB] [PDF 0KB ]( 14 )


639
WU Fuli WANG Bianyang ZHAO Jingzhou LIU Haibo LI Guangtao CHEN Mingqi
  Origin and characteristics of oil pool sequence in Ordos Basin
    The Mesozoic Ordos Basin developed the special oil pool sequence, which contains lithologic oil pool, lithologic-structural combination oil pool and structural oil pool from down to up. The comprehensive analyses on the different type of reservoir-forming condition and exploration status showed that the formation of oil pool sequence was controlled by many factors
including source rock, oil-gas migration, and reservoir-cap rock combination. The source rock is the main controlling factor for generation of oil pool sequence. The vertical distance between trap and source rock is the vital index, which determines oil source condition. The quality of cap rock has significance for oil pool sequence.
    2008 Vol. 29 (5): 639-642 [Abstract ] ( 146 ) [HTML 0KB] [PDF 0KB ]( 14 )


643
HU Anping CHEN Hanlin YANG Shufeng LIU Quanyou
 

Origin of natural gas and main controlling factors of reservoirs in Wolonghe Gas Field
    Wolonghe Gas Field is the first gas field discovered in China and has the multiple source rocks, multiple reservoirs and multiple traps. According to the component and carbon isotopic compositions of gases from three main reservoirs including the Lower Triassic Jialingjiang Formation, the Middle Carboniferous Huanglong Formation and the Lower Permian, the origin of
natural gas and the main source rocks were determined in combination with the distribution of source rocks. The gases in the Lower Triassic Jialingjiang Formation are mainly composed of coalformed gases from the Upper Permian humic source rocks and a slight mixture of oil-type gases from Silurian sapropelic source rocks. The gases in the Middle Carboniferous Huanglong
Formation are mixture of gases from Silurian sapropelic source rocks with different maturity. The gases in the Lower Permian are dominated by oil-type gases, which derived from Silurian source rocks mixed with a little gas from the Lower Permian carbonates. Besides, there are a lot of oil-cracked gases in Wolonghe Gas Field. Moreover, the main controlling factors of Wolonghe Gas Field include the high quality source rocks lying in the gas-generating center and surrounding area, the excellent reservoirs, traps related to the paleo-uplifts, and late-period accumulation.
    2008 Vol. 29 (5): 643-649 [Abstract ] ( 138 ) [HTML 0KB] [PDF 0KB ]( 13 )


650
DING Zengyong WANG Liangshu HU Wenxuan ZHANG Peng LIU Shaowen MI Ning
  Reconstruction of Cenozoic thermal history of Bohai Bay Basin with a transient heat flow model
    A model of one-dimensional transient heat flow was established by using the BasinMod software. Calibrated by the porosity, thermal conductivity, temperature of borehole and vitrinite reflectance, the thermal history of the Cenozoic sediments of nine deep wells in Bohai Bay Basin was reconstructed with the transient heat flow model, which considered the compaction of
sediments, heterogeneous conductivity structure, radioactive heat production in the upper crust and sediments, and thermal effects of sedimentary fillings and erosion. The simulation results of the heat flow history predicted by two-layer rift model and the constant current heat flow indicate that the present subsurface temperature of the Cenozoic sediments is the highest temperature attributed to deep burial, except local areas where the eroded thickness of Dongying Formation is large. However, the present heat flow value is not the highest ever experienced. The highest heat flow is 9%~23 % higher than the current value and occurred at the end of erosion of Dongying Formation before present 16~20 Ma. The radioactive heat generation is neglected in the rift heat flow model, which cannot reflect the thermal history by recorded temperature at the paleothermometry and present bottom hole. The transient heat flow model contains more geological information and influential factors than the rift heat flow model. The thermal history predicted by the transient heat flow model is likely the actual thermal evolution process experienced by the lithosphere and sediments in Bohai Bay Basin during the Cenozoic period.
    2008 Vol. 29 (5): 650-656 [Abstract ] ( 154 ) [HTML 0KB] [PDF 0KB ]( 14 )


657
CHEN Zhuxin JIA Dong WEI Guoqi LI Benliang LEI Yongliang LI Yuegang
  Characteristics of thrust structures in the northern Longmenshan front belt
   

The northern Longmenshan front belt extends along Guangyuan to Anxian and includes the typical anticlines such as Kuangshanliang, Tianjingshan, Qinglinkou and Zhongba. Field investigations and seismic interpretation ascertained two episode tectonic deformations in the Late Triassic and the Cenozoic periods in this front belt. The Kuangshanliang and Tianjingshan
structures show a duplex comprising of a shallow fault-bend fold in the Late Triassic period and a deep buried stacking anticline imbricated by several thrust sheets in the Cenozoic period. The Qinglinkou and Zhongba structures show a imbricate structure in the Late Triassic and a buried faultbend fold and fault-propagation fold, which may be created or altered in the Cenozoic period. The front belt of the northern Longmenshan exhibits a double-layer structural style characterized by shallow thrust structures and deep buried ones. The buried thrust structures are the frontier fields for hydrocarbon
exploration in the northern Longmenshan area.
    2008 Vol. 29 (5): 657-662，668 [Abstract ] ( 146 ) [HTML 0KB] [PDF 0KB ]( 15 )


663
GAO Xiaohui FANG Jie ZHANG Jing ZHAO Xia
  Control factors for structure of stratigraphic and lithologic reservoirs in the
Lower Cretaceous of Erlian Basin
    On the basis of seismic, logging and drilling information, the property of the stratigraphic and lithologic reservoirs in the Lower Cretaceous of Erlian Basin were analyzed with the sequence stratigraphy. Three factors for controlling the structure of those reservoirs include the rift structures, the sand control patterns of slope break and the faulttransfer zones, which influence petroleum accumulation in this area. The rift structure can be divided into three types of single fault overlap, single fault trough and complex type. The slope break has six patterns, including steep slope fault scrap and nearshore
subaqueous fans, steep slope fault ramp and nearshore subaqueous fans and turbidite fans, steep slope fault bench and fan-delta and turbidite fans, gentle slope and braided river delta and fan-delta, gentle slope flexure and fandelta and turbidite fans, and gentle slope fault bench and braided river delta or fan-delta and turbidite fans. There are four types faults-transfer zones in Erlian Basin, such as fault bend type, fault fracture type, fault intersection type and fault trace rift type. The analyses of different factors for controlling the structures can provide some information for exploring of stratigraphic and lithologic reservoirs in Erlian Basin.
    2008 Vol. 29 (5): 663-668 [Abstract ] ( 146 ) [HTML 0KB] [PDF 0KB ]( 15 )


669
SUN Yonghe QI Jiafu L Yanfang HAN Huajun
 

Characteristics of fault structure and its control to hydrocarbon in Bozhong Depression
    The characteristics of development and activity of fault in Bozhong Depression were analyzed. The control of fault on hydrocarbon reservoir was investigated. Four types of fault were developed in Bozhong Depression, including the early extensional faults, middle strike-slip extensional faults, late strike-slip faults and long-term active faults. There were three periods of fault activity in Bozhong Depression. In the Late Eocene period, there formed the extensional faults in NNE, NE and closely EW directions. In the sediment period of Dongying Formation, the right strike-slip extensional faults in NNE direction superposed the left strike-slip extensional faults in NW-NWW direction. During the period from the Late Pliocene to the Quaternary, a right strike-slip movement occurred in the faults of NNE direction under the influence of the strike-slip displacement in Tanlu fault zone. The formation and evolution of fault controlled generation, migration and accumulation of hydrocarbon. The slope zone and central salient with growing long-term active faults are the favorable areas of hydrocarbon migration and accumulation.
    2008 Vol. 29 (5): 669-675 [Abstract ] ( 129 ) [HTML 0KB] [PDF 0KB ]( 14 )


676
ZHAO Bangliu SHI Yumei LIU Ying QI Li
  Prediction of hydrocarbon distribution using multicomponent seismic data
    The multicomponent seismic technology can provide more seismic and physical parameters information used for predicting hydrocarbon distribution. The seismic data are of some illegibility and indeterminacy for description of object under the influence of acquisition and processing errors and noise. A fuzzy-evidential fusion method was presented to make the best
information. On the basis of the fuzzy theory, the Gauss subordinate functions of P-wave and S-wave velocities and Poisson ′s ratio were calculated. Taking the log subordinate function as model, the probable function was designed, then basic confidence level for the three parameters was obtained from seismic inversion. Three total basic confidence levels were obtained by fuzzy-evidential fusion and used to describe reservoirs with hydrocarbon or without hydrocarbon and indeterminacy area respectively. According to the maximal principle of total basic confidence level, the hydrocarbon distribution could be predicted. This method was applied to a gas field in Sichuan area. The predictions are consistent with the drilling results.
    2008 Vol. 29 (5): 676-679 [Abstract ] ( 134 ) [HTML 0KB] [PDF 0KB ]( 14 )


680
ZHANG Wenchao JIANG Shuanqi CHEN Yanjun DUAN Meng WU Qingya
  “Facies-potential-transport” reservoir model and formation of reservoirs in fault basin
   

According to the reservoir-formation mechanism, exploration situation and potential hydrocarbon resources, the geologic distribution of reservoirs in the fault basins of Jizhong Paleocene and Erlian Early Cretaceous periods were analyzed. In the course of complex geologic evolution, three elements of the fault basin including “sedimentary evolution-sedimentary facies-reservoir facies”, “structural zone-temperature-pressure field-hydrocarbon potential” and “transporting system” were gradually adjusted from the dynamic variation to the static equilibrium. Under the particular geologic condition and 3- dimensional space, six types of relative independent “complex transporting system” were constituted, including fault，ladder-shape, grid, plane, sitting chair and fissure types. Various complex reservoirs or complex reservoir zones were generated in fault basin. This reservoir model is the facies-potential-transport ternary reservoir model. The ternary reservoir model controlled rigorously the regular distribution, enrichment degree and exploration prospect of hydrocarbon in the rich oil trough.

    2008 Vol. 29 (5): 680-687，693 [Abstract ] ( 145 ) [HTML 0KB] [PDF 0KB ]( 17 )


688
LI Shuifu HE Sheng ZHANG Gangqing ZHANG Dongmei HU Shouzhi
  Determination of relative source proportion of mixed oils by grey correlation
analysis on distribution curves of n-alkanes
    The methods for calculating the relative source contribution proportion of the mixed oils at home and abroad were analyzed. A new method for determining the relative source proportion of mixed oils was proposed by using the grey correlation analysis on the n-alkanes distribution curves of the simulative mixed oils and the experimental mixed oils. When the degree of relevance between the simulative mixed oils and the experimental mixed oils is maximum, the proportion is considered to be the relative source contribution proportion of the mixed oils. The method was tested with the natural mixed oils in Daerqi Oilfield of Erlian Basin. The application result indicates that the useful results can be obtained using this method. The proportion of the simulative mixed oils can be altered optionally by using the new method, which is simple and favorable to be popularized.
    2008 Vol. 29 (5): 688-693 [Abstract ] ( 152 ) [HTML 0KB] [PDF 0KB ]( 14 )


694
LI Pengchun LIU Chunxiao ZHANG Yuan LONG Liping ZHANG Lihong REN Shufang
 

Characteristics and origins of fractures developed in Ordovician reef-
bank complex in Shunxi area of central Tarim Basin
    The observation and measurement of cores, thin slices, casting body slices, cathode luminescence and FMI well logging interpretations indicate that fracture systems with clear cyclicity in vertical direction are developed in the Ordovician reef-bank complex in Shunxi area of the central Tarim Basin and divided into vertical fracture, high-angle fracture and horizontal fracture in the morphology. According to the multi-period composite and superimposed characteristics of fracture origin, the fracture systems can also be divided into non-structural genetic fracture and structural genetic fracture. The later can be mechanically classified into tensile fracture, tensile-shear fracture and shear fracture. Some fractures are filled by sparry calcite, some ones are half-filled, and some ones are unfilled. The unfilled and half-filled fractures are well developed and have significant role for hydrocarbon storage and accumulation. According to filling characteristics and incised relationships between fractures as well as regional tectonic evolution history, the
structural genetic fracture can be further divided into three stages, including the late Caledonian-early Hercynian stage, late Hercynian-Indosinian stage and Yanshanian-Himalayan stage. The development of fracture is mainly controlled by mechanical property of limestone, tectonic stress field, tectonic movement, fault activity and volcanism.
    2008 Vol. 29 (5): 694-700 [Abstract ] ( 149 ) [HTML 0KB] [PDF 0KB ]( 15 )


701
WANG Yanzhong CAO Yingchang SONG Guoqi SUI Fenggui WANG Shuping
  Application of production test data to evaluation of the effective reservoir in deep clastic of Bonan Sag
    The production test data and petrophysical parameter were used to determine the lower limit values of porosity and permeability, which are 7.45% and 0.6×10-3μm2 respectively in the effective clastic reservoir of the buried depth from 3500m to 3700m in Bonan Sag. The results coincide well with the values obtained by the distribution function curve method. The precision ratio checked by production test data is 95.2%. Based on the daily fluid production rate， the porosity difference, the permeability difference, sedimentary facies, lithology and reservoir pressure, the deep clastic reservoir in Bonan Sag was divided into four categories. Type-Ⅰ,type-Ⅱand type-Ⅲ reservoirs are effective ones, and type-Ⅳ reservoir is the non-effective ones. In type-Ⅰ reservoir, the distributary channel and mouth bar of fan-delta front and middle fan braided channel of sublacustrinefan are the main sedimentary facies, sandstone and pebbled sandstone are the main rock types. The overpressure is popular in the formation. The conventional daily fluid production rate is over 5t. For type-Ⅱ reservoir, the distributary channel of fandelta plain and the
middle fan braided channel of near shoresubaqueousfan are the main sedimentary facies, and the pebbled sandstone is the
main rock type. The reservoir has normal pressure. The conventional daily fluid production rate is from 1t to 5t, and the unconventional daily fluid production rate is more than 5t. For type-Ⅲ reservoir, the inner fan mainstream channel of nearshore-subaqueous-fan and the distributary channel of fan-delta plain are the main sedimentary facies, and the conglomerate and pebbled sandstone are the main rock types. The reservoir has normal pressure. The
conventional daily fluid production rate is lower than 1t, and the unconventional daily fluid production rate is from 1t to 5t. For type-Ⅳ reservoir, the main stream channel of nearshore-subaqueousfan inner fan and middle fan braided channel of proluvial-fan are the main sedimentary facies, and the conglomerate and pebbled sandstones are the main types of rock. The pressure of reservoir is normal. The conventional and unconventional daily fluid production rates are lower than 1t.
    2008 Vol. 29 (5): 701-706，710 [Abstract ] ( 129 ) [HTML 0KB] [PDF 0KB ]( 13 )


707
BAO Youshu ZHANG Linye ZHANG Shouchun LIU Qing KONG Xiangxing
 

Compact-expulsion characteristics of source rocksin Shahejie Formation of Dongying Depression using percolation method
    On the basis of oilwater twophase percolation theory and factual materials, the compactexpulsion characteristics of source rocks were studied in the upper forth member and the lower third member of Shahejie Formation in Dongying Depression. The variation curves of oil expulsion concentration in source rocks were given, which indicated that oil expulsion concentration was controlled by viscosity of oil, saturation and relative permeability of oil and water in the source rocks. The critical oil saturation for oil expulsion of source rocks was related to those factors. In the early stage, oil expulsion concentration was much less than oil saturation of source rock. The expulsion material was mainly water, despite of the fact that oil saturation was rather high. Oil concentration increased with the burial depth of source rocks. When the burial depth of source rock reached a certain depth, the water saturation in source rocks was nearly equal to the irreducible water saturation, and the oil expulsion concentration was close to 1. The main oil expulsion stage could appear.
    2008 Vol. 29 (5): 707-710 [Abstract ] ( 173 ) [HTML 0KB] [PDF 0KB ]( 13 )
OIL FIELD DEVELOPMENT
 
 


711
SONG Ziqi TANG Changjiu LIU Xiaojuan PANG Zhenyu WANG Ruifei
 

Determination of favorable oil-bearing areas with extra low-permeability reservoir by “dessert” of petro-physical facies
    The extra low-permeability reservoirs in the middle part of Shaanbei slope are affected by many factors, such as sedimentary environment, diagenesis and structure. Both macroscopic physical property and micropore types of these reservoirs have strong heterogeneity， so the quality and percolation structure of the reservoir have a large difference. The flow zones are complex in the extra low-permeability reservoirs of the middle part of Shaanbei slope. A determination method was presented for favorable oil-bearing areas in the extra low-permeability reservoir using flow units of petrophysical facies. A comprehensive evaluation system of “dessert” of petro-physical facies was developed using various parameters for describing geologic features of porous medium, including flow zone indicator, energy storage parameters, diagenetic synthetical coefficient, thickness of single-permeability sandstone, effective thickness of oil layers, the ratio of sand body to formation thickness, permeability, porosity, shale content, and distribution frequency and density of inter-players. Above various parameters including permeability and storage capability, oil and gas bearing features and heterogeneity of reservoirs were integrated and synthesized by gray theory. The locations and distribution of favorable oilbearing area were effectively determined by using “dessert” of Type Ⅰ and Type Ⅱ petro-physical facies. The results could fully reflect geological features of the favorable oil-bearing areas in the extra low-permeability reservoirs.
    2008 Vol. 29 (5): 711-716 [Abstract ] ( 127 ) [HTML 0KB] [PDF 0KB ]( 12 )


717
LIU Yongjian HAO Chunlei HU Shaobin ZHAO Fajun WEN Shoubin WANG Dawei
  Capability and mechanism of microbe action in polymer-flooding reservoir
    A kind of polymer degrading microbe JHW-31 was selected from Daqing Oilfield. The microbe was inoculated and cultured in the culture medium confected with polymer and a little sucrose for 7 days under the condition of pH 7.2 and temperature 45℃. The viscosity reduction rate of the polymer reached 92.1%，and the molecular weight of the polymer decreased from 18×106 to 0.5×106. The gross of the polymer decreased a little bit. Nuclear magnetic resonance test result indicated that the content of the amide group in the polymer decreased from 74.6% to 60.8%, while the carboxylic acid group increased obviously. This kind of microbe could be confected with the surfactant microbe T11 and was compatible with the stratum water. The physical simulation indicated that the oil recovery increased by 5.4% when the microbe was used after polymer flooding. If the ASP flooding was used after microbe flooding, oil recovery could increase by 9.7%. In the heterogeneous core, this microbe can mobilize more remaining oil in the low-permeability zone and clean out the resorted polymer.
    2008 Vol. 29 (5): 717-722 [Abstract ] ( 130 ) [HTML 0KB] [PDF 0KB ]( 13 )


723
CAI Mingjin JIA Yonglu WANG Yongheng BAI Yu NIE Renshi
 

Dynamic pressure analysis on wells with vertical fractures in low-permeability dual-porosity reservoir
    The wells with finite conductivity vertical fractures would be formed after fracture treatment in the low-permeability double-porosity reservoirs. Based on the Warren-Root model, the mathematical models for wells with finite conductivity vertical fractures in low-permeability reservoirs were developed using the mass conservation law and elliptical flow method, considering the influences of threshold pressure gradient. The equations for bottom pressure of vertical fractured wells could be achieved using the Laplace transformation. The analysis on the affecting factors of dynamic pressure indicated that the threshold pressure gradient had a remarkable influence on the typical curves of the low-permeability wells with vertical fractures. The curves of dimensionless pressure and pressure derivation climb up at the later stage. The curves get up earlier with the more increase of the threshold pressure gradient. A real build-up testing explanation example of a fractured well in low-permeability reservoir was given.
    2008 Vol. 29 (5): 723-726，733 [Abstract ] ( 124 ) [HTML 0KB] [PDF 0KB ]( 15 )


727
YANG Xiaosong LIU Chuanxi YAN Jin WANG Weihong SHI Zhiliang JIA Ying
  Research on productivity law of herringbone multilateral gas well
    A three-dimensional pseudopressure distribution model for horizontal gas wells was developed in an unbounded reservoir. The pressure distribution equations in the formation of the herringbone multilateral gas wells were constructed on the basis of pressure superposition and mirror image reflection theory. The equations of gas flow in the multilateral well bore were constructed in consideration of friction loss, acceleration loss, and mixture loss and gravitation effects. A complete model for gas productivity of the herringbone multilateral well was obtained. The effects of physical property of reservoir, pressure loss of well bore and well configuration on gas productivity of the herringbone multilateral well were analyzed with the gas productivity model. The gas productivity laws of the herringbone multilateral well were obtained.
    2008 Vol. 29 (5): 727-733 [Abstract ] ( 136 ) [HTML 0KB] [PDF 0KB ]( 14 )


734
JI Guang XIA Jing LUO Kai JIAO Yuwei BIE Aifang
  Determination of natural gas deviation factor of ultra-high pressured gas reservoir
    Based on the theory of gas molecule movement and the equation state for fluid, it is proved theoretically that gas deviation factors under the ultra-high pressure are linearly dependent on pseudo-reduced pressure. The calculation result of Dranchuk-Abou-Kassem fitting equation was compared with that of the other fitting equations for high pressure and extra-pressured conditions. The performance of the DAK equation was also identified by experimental data of field gases under ultra-high pressure and by Standing-Katz correlation. The results show that it is possible and practical to generate the deviation factors of gas in ultra-pressure gas reservoirs by extending the application region of DAK equation and linearly extrapolated Standing-Katz correlation when the pseudoreduced pressure is over 15 in the same area. Furthermore, this linear extrapolation method of Standing-Katz correlation could be applicable to calculate the deviation factors for dry gas, wet gas and gas condensate reservoirs.
    2008 Vol. 29 (5): 734-737，741 [Abstract ] ( 130 ) [HTML 0KB] [PDF 0KB ]( 13 )


738
GUO Lanlei LI Zhenquan LI Shurong SHAN Liantao LI Feifei
  Optimization of oil-to-polymer viscosity ratios in the primary and secondary polymer flooding
    The influences of oil-to-polymer viscosity ratios in the primary and secondary polymer flooding on the enhanced oil recovery (EOR) in thin or heavy oil reservoirs were researched systematically. The reasonable range of oil-to-polymer viscosity ratio was optimized. The result shows that the increment of EOR gets larger with the increase of the oil-to-polymer viscosity ratio under the condition of the same crude oil viscosity, and the increment of EOR is unconspicuous while the viscosity ratio reaches to a certain value. The increment of EOR in the secondary polymer flooding is obviously lower than that in the first polymer flooding under the condition of same oil-to-polymer viscosity ratio. Higher oil-to-polymer viscosity ratio would be needed to reach the value of the primary polymer flooding. The earlier injection of polymer would get the better effect in the secondary polymer flooding. A theoretical plate could be used to check rationality of the injection parameters in the field and to provide basis for designing the reasonable injection parameters in the primary and secondary polymer flooding.
    2008 Vol. 29 (5): 738-741 [Abstract ] ( 142 ) [HTML 0KB] [PDF 0KB ]( 15 )


742
ZHA Wenshu LI Daolun LU Detang KONG Xianhui
  PEBI grid division in inter-well interference area
    Considering well spacing density and inter-well interference in some old oilfields of China, an algorithm for dividing PEBI grid of oil wells was proposed on the basis of the streamline equation. The stimulation results of PEBI grid were compared with that of the fine grid and the other coarse grids,which indicated that PEBI grid could reduce the computing time and also achieve the same accuracy as the fine grid.
    2008 Vol. 29 (5): 742-746 [Abstract ] ( 133 ) [HTML 0KB] [PDF 0KB ]( 15 )


747
PAN Kejia TAN Yongji WANG Caijing
  Inversion algorithm of differential equation for automatically identifying
water influx of reservoir boundary
    An automatic history matching method for identifying boundary water influx in a reservoir containing a single-phase fluid of incompressibility was developed on the basis of numerical simulation of water-displacing oil. This method is mathematically called boundary control inverse problem to identify water fluxes in a reservoir by using the dynamic observation data of production wells. Based on the differential equation inversion theory, this problem can be transformed to a nonlinear optimization problem that can be solved by conjugate gradient method (CGM). The search direction and step-length at each step were determined by corresponding adjoint problem and sensitivity problem, respectively. Some problems such as instability, slow convergence and dependence on initial value for general inversion methods in time-space domain can be avoided. The numerical results of theoretical model and practical application show that this method not only richens the differential equation inversion theory but also has applicable value in practice.
    2008 Vol. 29 (5): 747-751 [Abstract ] ( 142 ) [HTML 0KB] [PDF 0KB ]( 15 )
PETROLEUM ENGINEERING
 
 


752
YE Yan YAN Jienian ZOU Shengli LI Zaijun WANG Shuqi
  A novel method for evaluating damage of drilling fluid
to fractured carbonate reservoir
    A series of simulated fractured core samples made of stainless steel with a given width of fracture were used to evaluate the damage of drilling fluid to fractured carbonate reservoirs in laboratory. The width of artificial fracture was estimated by virtue of the image well log information. The relative error of the width of tested core with artificial fractures decreased to 1%. A series of tests for reservoir damage were conducted by using the simulated stainless steel core samples flushed with different drilling fluids such as the sulfonatepolymer drilling fluid and the solid-free drilling fluid with or without ideal packing bridging materials. On the basis of experimental results using this kind of simulated core, a novel approach to control the damage of fractured carbonate reservoirs was presented. The experimental results show that the effective temporary plugging ring on the end face of the simulated core sample can be observed clearly and the simulated stainless steel fractured cores make it possible to visualize the solid and filtrate invasion. The new evaluation method could be used to measure the feasibility of the idealpacking theory for the fractured reservoir, and it can also be applied to evaluate the sealing effectiveness by adding the temporary sealing particles in the drilling fluid.
    2008 Vol. 29 (5): 752-756 [Abstract ] ( 126 ) [HTML 0KB] [PDF 0KB ]( 15 )


757
L Kaihe QIU Zhengsong WEI Huiming LI Xianfeng SONG Yuansen
  Study on techniques of auto-adapting lost circulation
resistance and control for drilling fluid
    Lost circulation of drilling fluid is ubiquity in the drilled formation with severe heterogeneity, wide distribution of pore radius and unpredictability of pore radius. A kind of drilling fluid for auto-adapting lost circulation resistance and control was developed,which can rapidly generate thin and tight plugged zones in the drilled formation with wide distribution of pore radius. The laboratory evaluation shows that the auto-adapting drilling fluid system has the auto-adapting sealing effect, and the sealing ratio is over 90%. The pressure strength of sealing belt is above 9 MPa, and the sealing thickness is less than 1cm. The restored permeability in core achieves above 90%. Field application shows that the auto-adapting drilling fluid for lost circulation resistance and control can effectively increase the pressurebearing capacity of the formation. The effect of lost circulation resistance and control for drilling fluid is good.
    2008 Vol. 29 (5): 757-760，765 [Abstract ] ( 124 ) [HTML 0KB] [PDF 0KB ]( 12 )


761
MA Hai WANG Yanjiang WEI Maoan HU Rui
  A novel method for predicting formation drillability
    After the relationship between well-log data and formation drillability was analyzed,a novel method for predicting formation drillability based on particle swarm optimization and support vector machine (PSO-SVM) was proposed. A prediction model for formation drillability was established using the data of well-log acoustic velocity, formation density, fraction of shale and formation depth by training the SVM optimized by PSO algorithm. The proposed method was applied to Zhuang 2 Well in Junggar Basin. The experimental results show that it has higher prediction precision, faster convergence speed and better generalization effect than BP neural network.
    2008 Vol. 29 (5): 761-765 [Abstract ] ( 133 ) [HTML 0KB] [PDF 0KB ]( 14 )


766
HAN Laiju NI Hongjian ZHAO Jinhai LIU Zhihe WU Zhonghua
  Development of mechanical tool for automatic vertical drilling
    In order to effectively improve the penetration rate and quality in vertical drilling, a mechanical tool for automatic vertical drilling was developed by using the current technologies. The mechanical tool can timely respond to the gravity signal of drilling tool while well deviation happens. The actuator can be driven by the gravity of drilling tool and push the piston towards the borehole wall on the higher side under the created pressure difference inside and outside the rotating drill string resulted from the circulation of drilling fluid. The periodic lateral force was acted on the lower side of the borehole in the drilling bit. The deviation of well bore can be timely modified during drilling. Field test results show that the mechanical tool for a