Volume 20,Issue 4,2013 Table of Contents
2013, 20(4):1-4.
Abstract:
There were violent magma activities which have caused rich and abnormal petroleum with chemical properties in igneous rocks region of rift basins.In order to further study the natural gas origin，we did systematic analysis on geochemical characteristics of gas and source rocks in Gubei area.It is shown that，some source rocks are over-matured，and there were more inorganic CO2 and H2S in the gas with heavy alkane carbon isotopes and significant variable properties.Based on the theory of natural gas origin and isotope fractionation，we thought that the source rocks are subjected not only to normal thermal evolution by burial，but also to frequent heating by magma，which have led to the multistage evolution of organic matter，hydrocarbon generation，and decomposition of carbonate rock.In addition，the interfusion of magma liquid also made the gas compositions more complex.Finally，we indicated that the gas possessed the characteristics of universal mixture and multifold mixtures（that is multi-source gas，multi-stage evolution，multi-times hydrocarbon generation，hydrocarbon and non-hydrocarbon mixture），and the difference of mixing types or mixing proportion led to the variability of the gas chemical compositions of intrusive rocks region.
There were violent magma activities which have caused rich and abnormal petroleum with chemical properties in igneous rocks region of rift basins.In order to further study the natural gas origin，we did systematic analysis on geochemical characteristics of gas and source rocks in Gubei area.It is shown that，some source rocks are over-matured，and there were more inorganic CO2 and H2S in the gas with heavy alkane carbon isotopes and significant variable properties.Based on the theory of natural gas origin and isotope fractionation，we thought that the source rocks are subjected not only to normal thermal evolution by burial，but also to frequent heating by magma，which have led to the multistage evolution of organic matter，hydrocarbon generation，and decomposition of carbonate rock.In addition，the interfusion of magma liquid also made the gas compositions more complex.Finally，we indicated that the gas possessed the characteristics of universal mixture and multifold mixtures（that is multi-source gas，multi-stage evolution，multi-times hydrocarbon generation，hydrocarbon and non-hydrocarbon mixture），and the difference of mixing types or mixing proportion led to the variability of the gas chemical compositions of intrusive rocks region.
2013, 20(4):5-9.
Abstract:
As a result of confusion about the reservoir sedimentary microfacies and the distribution rule of sand body in early the development of Li151 oilfield，the core，thin section，logging data and well performance definitely indicate the conclusion of division of microfacies，the spatial distributing of sedimentary facies and the relationship between sedimentary facies and oil-gas enrichment，which provide guidance for subsequence development.The results show that the Yan8-Yan9 layers are developed in sedimentary system of delta plain with 1-3 from SW to NE distributary channel（s），which laterally swung，as well as the number and dimension of distributary channel（s）at different periods changed along with the fluctuation of base level.The Yan10 layer is developed in sedimentary system as braided river with developed channel bar and thick sand body.The distributary channels，sand bar in channels，channel bar of braided river are favorable for the oil-gas enrichment.These achievements are of valuable significance to direct the progressive develop? ment of the reservoir.
As a result of confusion about the reservoir sedimentary microfacies and the distribution rule of sand body in early the development of Li151 oilfield，the core，thin section，logging data and well performance definitely indicate the conclusion of division of microfacies，the spatial distributing of sedimentary facies and the relationship between sedimentary facies and oil-gas enrichment，which provide guidance for subsequence development.The results show that the Yan8-Yan9 layers are developed in sedimentary system of delta plain with 1-3 from SW to NE distributary channel（s），which laterally swung，as well as the number and dimension of distributary channel（s）at different periods changed along with the fluctuation of base level.The Yan10 layer is developed in sedimentary system as braided river with developed channel bar and thick sand body.The distributary channels，sand bar in channels，channel bar of braided river are favorable for the oil-gas enrichment.These achievements are of valuable significance to direct the progressive develop? ment of the reservoir.
2013, 20(4):10-16.
Abstract:
The Zhujiang formation in Dongsha uplift of the Pear River Mouth Basin develops three sedimentary facies：littoral facies，carbonate platform，shallow sea continental shelf facies，among which，the carbonate platform is the main sedimentary facie which is consisted of reef，bioclast bank and plate.This paper thoroughly studied the carbonate reservoir of the Zhujiang formation from reservoir sedimentology based on core observations by applying various measurements，such as analyses of normal thin-section，cast thin-section，scanning electron microscope，X-ray diffraction of clay minerals，and this paper indicates that the main reservoir spaces are secondary pores，followed by primary intergranular pore，biological coelom hole and other primary porosity.By combining the measurement results with sedimentary evolution and diagenetic characteristics of basin，this study indicates that the reservoir’s development is influenced by the change of the sea-level，sedimentary facies and diagenesis.The platform edge and bioclast bank in Liuhua area are the favorable reservoir belt，and，the reef and bioclast bank of platform edge or platform point reef and bioclast bank of internal platform in Huizhou and Lufeng area are the less favorable reservoir.
The Zhujiang formation in Dongsha uplift of the Pear River Mouth Basin develops three sedimentary facies：littoral facies，carbonate platform，shallow sea continental shelf facies，among which，the carbonate platform is the main sedimentary facie which is consisted of reef，bioclast bank and plate.This paper thoroughly studied the carbonate reservoir of the Zhujiang formation from reservoir sedimentology based on core observations by applying various measurements，such as analyses of normal thin-section，cast thin-section，scanning electron microscope，X-ray diffraction of clay minerals，and this paper indicates that the main reservoir spaces are secondary pores，followed by primary intergranular pore，biological coelom hole and other primary porosity.By combining the measurement results with sedimentary evolution and diagenetic characteristics of basin，this study indicates that the reservoir’s development is influenced by the change of the sea-level，sedimentary facies and diagenesis.The platform edge and bioclast bank in Liuhua area are the favorable reservoir belt，and，the reef and bioclast bank of platform edge or platform point reef and bioclast bank of internal platform in Huizhou and Lufeng area are the less favorable reservoir.
2013, 20(4):17-19.
Abstract:
In Neogene meandering stream channel sand bodies in Jiyang depression，the petroleum usually concentrates in a given pay bed，and only several given sand bodies are filled with petroleum in the given pay bed.The reasons causing these phenomena are discussed in this paper.Firstly，the differentia of fault activity and reservoir-cap assemblage result in the differential distribution of petroleum in meandering stream channel sandstone in different pay beds of different prolific zones.Secondly，the contact relationship between channel sand bodies and transforming faults and structural settings have caused that only several given sand bodies are selectively filled with petroleum in a given pay bed of a given prolific zone.Thirdly，the reservoir characteristics of channel sandstone also influence the selective injection of petroleum into channel sand bodies.Generally，under the same reservoir-forming conditions，the major river channel sand bodies have advantages in reservoir quality and are more easily to concentrate petroleum.The analyses of the reasons of petroleum selective injection have great significance in the zone and play selection，as well as practical well location in the process of petroleum exploration.
In Neogene meandering stream channel sand bodies in Jiyang depression，the petroleum usually concentrates in a given pay bed，and only several given sand bodies are filled with petroleum in the given pay bed.The reasons causing these phenomena are discussed in this paper.Firstly，the differentia of fault activity and reservoir-cap assemblage result in the differential distribution of petroleum in meandering stream channel sandstone in different pay beds of different prolific zones.Secondly，the contact relationship between channel sand bodies and transforming faults and structural settings have caused that only several given sand bodies are selectively filled with petroleum in a given pay bed of a given prolific zone.Thirdly，the reservoir characteristics of channel sandstone also influence the selective injection of petroleum into channel sand bodies.Generally，under the same reservoir-forming conditions，the major river channel sand bodies have advantages in reservoir quality and are more easily to concentrate petroleum.The analyses of the reasons of petroleum selective injection have great significance in the zone and play selection，as well as practical well location in the process of petroleum exploration.
2013, 20(4):20-24.
Abstract:
According to heat-press simulation experiment of source rock and phase diagram，we studied the phase type of hydrocarbon and its evolution characteristics during the stage of generation-discharge and migration-accumulation in Wenliu area，Dongpu depression.The results show that the Es3 source rock hydrocarbon phase stages are varying in different depth attribute to the difference in thermal evolution degree，the phase stages are heavy oil，conventional oil，ethereal oil，condensate oil and wet gas-dry gas.The changes during generating and transporting including gas ex-solution，oil thickening，oil cracking，oil inverse evaporating into gas.Controlling by temperature，pressure and composition，the middle and upper layer major transform is gas ex-solute from oil，and the lower layer transform is oil cracking dominated by temperature and pressure.Based on the former information，combining with the GOR data and hydrocarbon phase state，the law of phase state in vertical sequence is studied，reservoirs in the deeper layer are mainly gas pool，while reservoirs in the middle and upper layer are mainly oil reservoirs and the critical state of oil and gas reservoirs.
According to heat-press simulation experiment of source rock and phase diagram，we studied the phase type of hydrocarbon and its evolution characteristics during the stage of generation-discharge and migration-accumulation in Wenliu area，Dongpu depression.The results show that the Es3 source rock hydrocarbon phase stages are varying in different depth attribute to the difference in thermal evolution degree，the phase stages are heavy oil，conventional oil，ethereal oil，condensate oil and wet gas-dry gas.The changes during generating and transporting including gas ex-solution，oil thickening，oil cracking，oil inverse evaporating into gas.Controlling by temperature，pressure and composition，the middle and upper layer major transform is gas ex-solute from oil，and the lower layer transform is oil cracking dominated by temperature and pressure.Based on the former information，combining with the GOR data and hydrocarbon phase state，the law of phase state in vertical sequence is studied，reservoirs in the deeper layer are mainly gas pool，while reservoirs in the middle and upper layer are mainly oil reservoirs and the critical state of oil and gas reservoirs.
2013, 20(4):25-29.
Abstract:
Through the group composition analysis of the oils in Chepaizi area，it is found that the asphalene components are absent not only in the light oil without degradation，but also in some heavy oils，obviously different from the common heavy oil with higher asphaltene content.According to the asphaltene content，the crude oils in Chepaizi area are divided into four types：the first is the light oil without asphaltene，accumulated lately with high maturation；the second is the heavy oil rich in asphaltene，left from the native heavy oil dissolved by the light oil；the third is the heavy oil without asphaltene，dissolved and migrated with the light oil；the fourth is the heavy oil with medium content of asphaltene，diluted and migrated with the light oil in early stage.The main reason accounting for major asphaltene content difference is the different properties of oil at different migration stage.The normal mature oil developed the heavy oil rich in asphaltene and nonhydrocarbon at early stage，and the dissolving capability of light oil infused at later stage for asphaltene is low，and there is no dissolving and migration at later infusing stage.The regulating function of light oil is the intrinsic factor for the tremendous divergence of the oil character in Chepaizi area.The light oil emerged portrait transformational migration at deep fault in Sikeshu sag，and entered into migration pathway including the heavy oil early stage or without heavy oil separately.The main migration is along the layers at slope place.The selective adjustment of the light oil in migration pathway with heavy oil formed the special phenomenon that the oil distributing is light oil on top and heavy oil down in Chepaizi area.
Through the group composition analysis of the oils in Chepaizi area，it is found that the asphalene components are absent not only in the light oil without degradation，but also in some heavy oils，obviously different from the common heavy oil with higher asphaltene content.According to the asphaltene content，the crude oils in Chepaizi area are divided into four types：the first is the light oil without asphaltene，accumulated lately with high maturation；the second is the heavy oil rich in asphaltene，left from the native heavy oil dissolved by the light oil；the third is the heavy oil without asphaltene，dissolved and migrated with the light oil；the fourth is the heavy oil with medium content of asphaltene，diluted and migrated with the light oil in early stage.The main reason accounting for major asphaltene content difference is the different properties of oil at different migration stage.The normal mature oil developed the heavy oil rich in asphaltene and nonhydrocarbon at early stage，and the dissolving capability of light oil infused at later stage for asphaltene is low，and there is no dissolving and migration at later infusing stage.The regulating function of light oil is the intrinsic factor for the tremendous divergence of the oil character in Chepaizi area.The light oil emerged portrait transformational migration at deep fault in Sikeshu sag，and entered into migration pathway including the heavy oil early stage or without heavy oil separately.The main migration is along the layers at slope place.The selective adjustment of the light oil in migration pathway with heavy oil formed the special phenomenon that the oil distributing is light oil on top and heavy oil down in Chepaizi area.
2013, 20(4):30-32.
Abstract:
The sedimentary characteristics of Neogene Shawan formation reservoirs are subtle and complex.Based on the regional geological condition，existing core，logging and other various geological material，we analyzed the sedimentary characteristics of Shawan formation.The Shawan formation mainly developed braided river fan sedimentary system，which can be divided into three parts including proximal subfacies，middle subfacies，and distal subfacies.The middle subfacies，and proximal subfacies are developed with wide range of braided river sedimentation，and can be divided into braided river，channel bar，and distributary between sedimentary microfacies.The content of sandy conglomerate is high，and the lithologic is coarse，which has less fine grained suspended sediment.The logging curve feature in study area is apparent.The Shawan reservoir is made up of the channel sand body which is from the southwest and northwest，and formed the large complex lithology reservoir distribution.
The sedimentary characteristics of Neogene Shawan formation reservoirs are subtle and complex.Based on the regional geological condition，existing core，logging and other various geological material，we analyzed the sedimentary characteristics of Shawan formation.The Shawan formation mainly developed braided river fan sedimentary system，which can be divided into three parts including proximal subfacies，middle subfacies，and distal subfacies.The middle subfacies，and proximal subfacies are developed with wide range of braided river sedimentation，and can be divided into braided river，channel bar，and distributary between sedimentary microfacies.The content of sandy conglomerate is high，and the lithologic is coarse，which has less fine grained suspended sediment.The logging curve feature in study area is apparent.The Shawan reservoir is made up of the channel sand body which is from the southwest and northwest，and formed the large complex lithology reservoir distribution.
2013, 20(4):33-36.
Abstract:
The reservoir characteristics and major controlling factors of reservoir quality of the Paleogene in the southern Tarim basin are analyzed by means of massive drilling data，well logging and test data.This study shows that the reservoir of the Paleogene in the study area shows high compositional maturity and middle textural maturity，which has the characteristics that the main lithologies of the reservoir are feldspar quartz sandstone and lithic arkose，the high matrix contents and medium roundness and sorting.Types of pores of the sandstone reservoir are mainly intergranular pores，dissolved pores between grains，intragranular dissolved pores，all kinds of microporous and cracks and so on.Denudation pore is the major type，and then intergranular pore.The reservoirs are extra low porosity and permeability with the porosity ranging from 4.5% to 17.5% and permeability ranging from 0.1×10-3 μm2 to 10×10-3 μm2.The reservoir in research area is mainly affected by combined factors of depositional environment and diagenesis.The main diagenesis types are cementation and dissolution.By comprehensive analysis，the result shows that the favorable reservoir is mainly distributed in sheet sand and underwater distributary channel.
The reservoir characteristics and major controlling factors of reservoir quality of the Paleogene in the southern Tarim basin are analyzed by means of massive drilling data，well logging and test data.This study shows that the reservoir of the Paleogene in the study area shows high compositional maturity and middle textural maturity，which has the characteristics that the main lithologies of the reservoir are feldspar quartz sandstone and lithic arkose，the high matrix contents and medium roundness and sorting.Types of pores of the sandstone reservoir are mainly intergranular pores，dissolved pores between grains，intragranular dissolved pores，all kinds of microporous and cracks and so on.Denudation pore is the major type，and then intergranular pore.The reservoirs are extra low porosity and permeability with the porosity ranging from 4.5% to 17.5% and permeability ranging from 0.1×10-3 μm2 to 10×10-3 μm2.The reservoir in research area is mainly affected by combined factors of depositional environment and diagenesis.The main diagenesis types are cementation and dissolution.By comprehensive analysis，the result shows that the favorable reservoir is mainly distributed in sheet sand and underwater distributary channel.
2013, 20(4):37-41.
Abstract:
The physical properties，micro-structure，mechanism of water and oil flow in porous media and nuclear magnetic resonance movable water saturation are systematically studied by means of constant-rate mercury injection technique，nuclear magnetic resonance，centrifugal experiment and waterflood experiment suitable for the poor quality of Jiangsu ultra-low-permeability oilfield.Meanwhile，the reservoir quality of different regions is also evaluated based on the five element classification method herein.The experimental results indicate that the physical property of Taizhou formation is better than that of Funing formation.The characteristic of porethroat distribution of different permeability is different.However，the pore distribution is less variable.The lower the reservoir permeability，the smaller porehroat.Between the main stream pore-throat and the reservoir permeability，there has a perfect relationship between the exponential function.The NMR experiment results demonstrate that the movable water saturation of Taizhou and Funing formation is 67.2%and 32.9%，respectively.During the waterflood process，the oil relative permeability drastically decreased as the increase of the water saturation but the water relative permeability increased slightly.The waterflood efficiency of the south-fault ultrapermeability was 54.1%on average.The multiphase flow experiment suggests that a certain amount of oil is still located in the large pores after the waterflood.The reservoir evaluation results using the five element classification method indicate that the physical quality of different oil regions ordered from good to bad is Taizhou formation，Chen2，Xuzhuang，Zhudun，Fangxiang and Xu31 Funing formation.
The physical properties，micro-structure，mechanism of water and oil flow in porous media and nuclear magnetic resonance movable water saturation are systematically studied by means of constant-rate mercury injection technique，nuclear magnetic resonance，centrifugal experiment and waterflood experiment suitable for the poor quality of Jiangsu ultra-low-permeability oilfield.Meanwhile，the reservoir quality of different regions is also evaluated based on the five element classification method herein.The experimental results indicate that the physical property of Taizhou formation is better than that of Funing formation.The characteristic of porethroat distribution of different permeability is different.However，the pore distribution is less variable.The lower the reservoir permeability，the smaller porehroat.Between the main stream pore-throat and the reservoir permeability，there has a perfect relationship between the exponential function.The NMR experiment results demonstrate that the movable water saturation of Taizhou and Funing formation is 67.2%and 32.9%，respectively.During the waterflood process，the oil relative permeability drastically decreased as the increase of the water saturation but the water relative permeability increased slightly.The waterflood efficiency of the south-fault ultrapermeability was 54.1%on average.The multiphase flow experiment suggests that a certain amount of oil is still located in the large pores after the waterflood.The reservoir evaluation results using the five element classification method indicate that the physical quality of different oil regions ordered from good to bad is Taizhou formation，Chen2，Xuzhuang，Zhudun，Fangxiang and Xu31 Funing formation.
2013, 20(4):42-45.
Abstract:
In order to enhance the advantageous region forecast accuracy of the reservoir of the third member of Liushagang formation in Fushan sag，and considering the low quality of the seismic data and abundant information of the well drilling and logging data，this paper analyzes the lithological properties，physical properties，electrical properties and oiliness by means of core and logging data and confirms the reservoir of third member of Liushagang formation belonging to the medium porosity and medium-low permeability reservoir.The hydrocarbon enrichment is mainly controlled by the quality of the physical and lithological properties.The log interpretation models of lithological properties，physical properties and oiliness are set up with the logging data of natural gamma，interval transit time and resistivity，and these models are verified to be suitable for the study area.Finally，this paper determines the identifying standard of the effective thickness.The lower limit of the porosity and permeability is 6.3% and 0.202×10-3 μm2 respectively，and the lower limit of the resistivity and interval transit time are 10 Ω?m and 230 μs/m respectively.
In order to enhance the advantageous region forecast accuracy of the reservoir of the third member of Liushagang formation in Fushan sag，and considering the low quality of the seismic data and abundant information of the well drilling and logging data，this paper analyzes the lithological properties，physical properties，electrical properties and oiliness by means of core and logging data and confirms the reservoir of third member of Liushagang formation belonging to the medium porosity and medium-low permeability reservoir.The hydrocarbon enrichment is mainly controlled by the quality of the physical and lithological properties.The log interpretation models of lithological properties，physical properties and oiliness are set up with the logging data of natural gamma，interval transit time and resistivity，and these models are verified to be suitable for the study area.Finally，this paper determines the identifying standard of the effective thickness.The lower limit of the porosity and permeability is 6.3% and 0.202×10-3 μm2 respectively，and the lower limit of the resistivity and interval transit time are 10 Ω?m and 230 μs/m respectively.
2013, 20(4):46-48.
Abstract:
The fractured-cavity carbonate reservoir spaces，including pores，caves and fractures，have varied scales，irregular shapes and discontinuous distribution.Quantitative characterization of effective reservoir space is difficult，and the accurate calculation of petroleum geological reserves of the reservoir is the key to technical difficulties.Therefore，the probability method based on 3D geological model was studied and discussed.Based on the single well fractured-cavity reservoir identification and reservoirs prediction between wells，a series of geological models of equal probability were established by methods of deterministic modeling and stochastic modeling combined.According to the 3D geological model of grid data，the effective fractured-cavity reservoir volume was calculated.On the basis of pores，caves and fractures of the 3D geological model，the petroleum geological reserves were computed separately，as well as the statistical probability distribution of petroleum geological reserves.The most likely petroleum geological reserves of Tahe-IV district is 5 665×104 t，the most pessimistic is 5 470×104 t，the most optimistic is 5 914×104 t，and the calculation reserves results and the Tahe oilfield production situation is basically the same.The results show that，by means of the probability method based on 3D geological model considering the heterogeneity of reservoir，the oil geological reserves calculation is more accurate，and it can detail the composition of petroleum geological reserves，and can point out the favorable petroleum geological reserves accumulation area.
The fractured-cavity carbonate reservoir spaces，including pores，caves and fractures，have varied scales，irregular shapes and discontinuous distribution.Quantitative characterization of effective reservoir space is difficult，and the accurate calculation of petroleum geological reserves of the reservoir is the key to technical difficulties.Therefore，the probability method based on 3D geological model was studied and discussed.Based on the single well fractured-cavity reservoir identification and reservoirs prediction between wells，a series of geological models of equal probability were established by methods of deterministic modeling and stochastic modeling combined.According to the 3D geological model of grid data，the effective fractured-cavity reservoir volume was calculated.On the basis of pores，caves and fractures of the 3D geological model，the petroleum geological reserves were computed separately，as well as the statistical probability distribution of petroleum geological reserves.The most likely petroleum geological reserves of Tahe-IV district is 5 665×104 t，the most pessimistic is 5 470×104 t，the most optimistic is 5 914×104 t，and the calculation reserves results and the Tahe oilfield production situation is basically the same.The results show that，by means of the probability method based on 3D geological model considering the heterogeneity of reservoir，the oil geological reserves calculation is more accurate，and it can detail the composition of petroleum geological reserves，and can point out the favorable petroleum geological reserves accumulation area.
2013, 20(4):49-52.
Abstract:
Currently，the simulation results of most cyclic water flooding reservoirs are better than the observation of the practical cyclic water flooding reservoir.To solve this problem，the capillary hysteresis and cyclic water flooding mechanism considering capillary hysteresis are analyzed by numerical simulation.It is concluded that the water saturation direction in the cyclic water flooding is changed periodically，this means that the reservoir displacement mode alternates the drainage process and imbitition process，and the phenomenon of capillary hysteresis prevail in the reservoir.The capillary hysteresis will generate a new capillary pressure curve which lies in the drainage capillary pressure curve and imbitition capillary pressure curve.The capillary pressure is the main force in cyclic water flooding.When considering the capillary hysteresis，the liquid flux between high permeable layer and low permeable layer and the oil flux between high permeable grid and low permeable grid are less than that of the case not considering the capillary hysteresis （drainage capillary pressure curve is used）.With the consideration of capillary hysteresis，the simulation results correspond to that of the practical reservoir.
Currently，the simulation results of most cyclic water flooding reservoirs are better than the observation of the practical cyclic water flooding reservoir.To solve this problem，the capillary hysteresis and cyclic water flooding mechanism considering capillary hysteresis are analyzed by numerical simulation.It is concluded that the water saturation direction in the cyclic water flooding is changed periodically，this means that the reservoir displacement mode alternates the drainage process and imbitition process，and the phenomenon of capillary hysteresis prevail in the reservoir.The capillary hysteresis will generate a new capillary pressure curve which lies in the drainage capillary pressure curve and imbitition capillary pressure curve.The capillary pressure is the main force in cyclic water flooding.When considering the capillary hysteresis，the liquid flux between high permeable layer and low permeable layer and the oil flux between high permeable grid and low permeable grid are less than that of the case not considering the capillary hysteresis （drainage capillary pressure curve is used）.With the consideration of capillary hysteresis，the simulation results correspond to that of the practical reservoir.
2013, 20(4):53-56.
Abstract:
The well pattern infilling is one of the important measures to improve the development performance of the complicated faultblock reservoirs at high water cut stage.And，the determination of reasonable injection-production well spacing is a critical factor affecting the development performance of well pattern infilling.Taking the well group of one injection well and two production wells for example，a new method，based on the non-steady oil-water two-phase flow theory to calculate reasonable well spacing，is constructed to achieve the equilibrium displacement for the complicated fault-block reservoirs at high water cut stage with the influence of such typical factors as reservoir parameters，remaining oil distribution and formation dip.And，it’s verified by the reservoir numerical simulation.The results indicate that this method can achieve the equilibrium displacement and improve the developing performance greatly.The research is of important guiding significance to the determination of reasonable well spacing for the complicated fault-block reservoirs at high water cut stage.
The well pattern infilling is one of the important measures to improve the development performance of the complicated faultblock reservoirs at high water cut stage.And，the determination of reasonable injection-production well spacing is a critical factor affecting the development performance of well pattern infilling.Taking the well group of one injection well and two production wells for example，a new method，based on the non-steady oil-water two-phase flow theory to calculate reasonable well spacing，is constructed to achieve the equilibrium displacement for the complicated fault-block reservoirs at high water cut stage with the influence of such typical factors as reservoir parameters，remaining oil distribution and formation dip.And，it’s verified by the reservoir numerical simulation.The results indicate that this method can achieve the equilibrium displacement and improve the developing performance greatly.The research is of important guiding significance to the determination of reasonable well spacing for the complicated fault-block reservoirs at high water cut stage.
2013, 20(4):57-61.
Abstract:
Aiming at the development contradiction of severe water breakthrough in Anpeng area of Zhao’ao oilfield，the gel foam is selected，including the high temperature resistance foam bubbling agent and the gel foam stabilizing system which is made up of 0.2%-0.3% foaming agent，0.25%-0.35% comb polymer and 0.6%-0.8% phenolic resin crosslinker.The gel foam profile control system is developed，the injection mode，gas-liquid ratio and injection rate are optimized by the physical simulation methods and the high temperature resistance gel foam system adaptable to the high temperature reservoir of Zhao’ao oilfield is developed.The results indicated that the phenolic resin cross-linked polymer has good effect for stabilizing foam as the stabilizing system of the gel foam and could increase the half-life period substantially.Compared to the slug injection mode，the gas-liquid mixed injection mode has better plugging performance；the best gas-liquid ratio is 1∶1，and higher or lower all has an adverse effect on the plugging performance of the gel foam；the best injection rate is 0.5 mL/min，higher or lower also has the same adverse effect on the resistance coefficient and plugging performance of gel foam.The displacement experiment shows that the gel foam profile-control system has good selective plugging performance，which could increase the profile improving rate to 99%，and could increase the oil production by 44.6%.
Aiming at the development contradiction of severe water breakthrough in Anpeng area of Zhao’ao oilfield，the gel foam is selected，including the high temperature resistance foam bubbling agent and the gel foam stabilizing system which is made up of 0.2%-0.3% foaming agent，0.25%-0.35% comb polymer and 0.6%-0.8% phenolic resin crosslinker.The gel foam profile control system is developed，the injection mode，gas-liquid ratio and injection rate are optimized by the physical simulation methods and the high temperature resistance gel foam system adaptable to the high temperature reservoir of Zhao’ao oilfield is developed.The results indicated that the phenolic resin cross-linked polymer has good effect for stabilizing foam as the stabilizing system of the gel foam and could increase the half-life period substantially.Compared to the slug injection mode，the gas-liquid mixed injection mode has better plugging performance；the best gas-liquid ratio is 1∶1，and higher or lower all has an adverse effect on the plugging performance of the gel foam；the best injection rate is 0.5 mL/min，higher or lower also has the same adverse effect on the resistance coefficient and plugging performance of gel foam.The displacement experiment shows that the gel foam profile-control system has good selective plugging performance，which could increase the profile improving rate to 99%，and could increase the oil production by 44.6%.
2013, 20(4):62-64.
Abstract:
In order to understand the interaction rule between alkali and crude oil，the Gudong crude oil is separated into acidic components，resin and asphaltene，saturated hydrocarbons，aromatic hydrocarbons.The Gudong crude oil as the study object has high acid value.The interfacial tension between the aqueous solution of alkali and simulated oil is investigated through changing the alkali type and value of pH.The result shows that the rule of organic alkali decreasing interfacial tension is different from that of inorganic alkali.With the increase of pH，the interfacial tension between organic alkali and Gudong crude oil decreases at first and then increases.When the organic alkali concentration is 1%，the interfacial tension is lowest.The dynamic interfacial tension between acidic component simulation oil and the aqueous solution of organic alkali varies with time，and the interfacial tension-time curve shows the shape of“V”or “U”.Through the variation of interfacial tension between aqueous solution of organic alkali and resin simulated oil and asphaltene simulated oil，it can be seen that the organic alkali can react with the acidic components in resin and asphaltene.However，the organic alkali can’t react with saturated hydrocarbons and aromatic hydrocarbons.
In order to understand the interaction rule between alkali and crude oil，the Gudong crude oil is separated into acidic components，resin and asphaltene，saturated hydrocarbons，aromatic hydrocarbons.The Gudong crude oil as the study object has high acid value.The interfacial tension between the aqueous solution of alkali and simulated oil is investigated through changing the alkali type and value of pH.The result shows that the rule of organic alkali decreasing interfacial tension is different from that of inorganic alkali.With the increase of pH，the interfacial tension between organic alkali and Gudong crude oil decreases at first and then increases.When the organic alkali concentration is 1%，the interfacial tension is lowest.The dynamic interfacial tension between acidic component simulation oil and the aqueous solution of organic alkali varies with time，and the interfacial tension-time curve shows the shape of“V”or “U”.Through the variation of interfacial tension between aqueous solution of organic alkali and resin simulated oil and asphaltene simulated oil，it can be seen that the organic alkali can react with the acidic components in resin and asphaltene.However，the organic alkali can’t react with saturated hydrocarbons and aromatic hydrocarbons.
2013, 20(4):65-68.
Abstract:
In view of the present commonly used fuzzy theory integrated well-to-well interporosity flow evaluation method，the ratings appear contradictory of each single index，and the accuracy of the discriminant method of the fuzzy theory is greatly affected.This paper tries to apply extension theory to the researches on cross-flow between the wells assessment.According to the characteristics and influences of water-flood in fracture reservoir，and on the basis of matter-element theory，the extension set theory and dependent function calculation，the characteristics of cross-flow between the wells are analyzed by means of qualitative and quantitative method.By determining cross-flow field matter，classical field matter，elements and segment field matter，weight coefficient and correlation function，which applied extension decision method，cluster analysis and gravity method，the Extenics theory fully considers the various factors that are interrelated and interdependent，and it can turn the evaluation results incompatibility of interaction characteristics of the single index into compatibility，and then it is distinguished by extension theory method，it is proved to be feasible by a practical application in Yangjiaba reservoir with 86% accuracy，and it is promising in application.
In view of the present commonly used fuzzy theory integrated well-to-well interporosity flow evaluation method，the ratings appear contradictory of each single index，and the accuracy of the discriminant method of the fuzzy theory is greatly affected.This paper tries to apply extension theory to the researches on cross-flow between the wells assessment.According to the characteristics and influences of water-flood in fracture reservoir，and on the basis of matter-element theory，the extension set theory and dependent function calculation，the characteristics of cross-flow between the wells are analyzed by means of qualitative and quantitative method.By determining cross-flow field matter，classical field matter，elements and segment field matter，weight coefficient and correlation function，which applied extension decision method，cluster analysis and gravity method，the Extenics theory fully considers the various factors that are interrelated and interdependent，and it can turn the evaluation results incompatibility of interaction characteristics of the single index into compatibility，and then it is distinguished by extension theory method，it is proved to be feasible by a practical application in Yangjiaba reservoir with 86% accuracy，and it is promising in application.
17 Conversion calculation of reservoir permeability from laboratory data based on 3D strata stresses
2013, 20(4):69-71.
Abstract:
The permeability transformation between the laboratory and formation condition is an important research in reservoir engineering.The compression of the rock will lead to the decrease of the pore size and the permeability reduction，which results in the problem that the permeability of rocks measured at laboratory condition is higher than that at reservoir condition.Therefore，it is necessary to do the conversion calculation of permeability from laboratory condition to the reservoir one.According to the difference stress state between laboratory and reservoir，a study was conducted in this paper about the conversion method of laboratory permeability to reservoir condition.The conversion formula presented in this paper utilizes the three dimensional stresses to overcome the problem taken from using the overburden pressure only.The case calculation result shows that the reservoir permeability calculated with overburden pressure only is quite smaller than that with three dimensional stresses.Meantime，the conclusion can be draw that the low permeability from the new method is about 10% larger than the initial method.
The permeability transformation between the laboratory and formation condition is an important research in reservoir engineering.The compression of the rock will lead to the decrease of the pore size and the permeability reduction，which results in the problem that the permeability of rocks measured at laboratory condition is higher than that at reservoir condition.Therefore，it is necessary to do the conversion calculation of permeability from laboratory condition to the reservoir one.According to the difference stress state between laboratory and reservoir，a study was conducted in this paper about the conversion method of laboratory permeability to reservoir condition.The conversion formula presented in this paper utilizes the three dimensional stresses to overcome the problem taken from using the overburden pressure only.The case calculation result shows that the reservoir permeability calculated with overburden pressure only is quite smaller than that with three dimensional stresses.Meantime，the conclusion can be draw that the low permeability from the new method is about 10% larger than the initial method.
2013, 20(4):72-74.
Abstract:
The reservoir condition after the water flooding is different from the initial state，so the steam flooding mechanism becomes more complicated.Through the water drive after the steam drive，the physical model experiments can be utilized for the further understanding on the mechanism of oil increase，so as to guide the steam flooding plan design of the water drive oilfield.In this paper，on the basis of the water flooding and the steam flooding physical model experiment，the link between the physical model experiment similar criteria of water flooding and steam flooding has been established.By this criteria，some actual water flooding sandstone reservoirs have been modeled，with the establishment of reliable physical model of two dimension and triaxiality proportion.Based on that，two groups of experiment of the plane homogeneous reservoir steam flooding after water flooding and the vertical non-homogeneous reservoir steam flooding after water flooding have been conducted.Some parameters，like the development of steam flooding temperature field，the degree of reserve recovery，the variation of water content and the steam zone formation time under different experiment condition，have been obtained.The result shows that for the steam distillation，the displacement effect is the main mechanism in the steam zone，and the reasonable steam flooding pressure conversion is the key to steam flooding and the reservoir heterogeneity has some influence on the effects of steam flooding.
The reservoir condition after the water flooding is different from the initial state，so the steam flooding mechanism becomes more complicated.Through the water drive after the steam drive，the physical model experiments can be utilized for the further understanding on the mechanism of oil increase，so as to guide the steam flooding plan design of the water drive oilfield.In this paper，on the basis of the water flooding and the steam flooding physical model experiment，the link between the physical model experiment similar criteria of water flooding and steam flooding has been established.By this criteria，some actual water flooding sandstone reservoirs have been modeled，with the establishment of reliable physical model of two dimension and triaxiality proportion.Based on that，two groups of experiment of the plane homogeneous reservoir steam flooding after water flooding and the vertical non-homogeneous reservoir steam flooding after water flooding have been conducted.Some parameters，like the development of steam flooding temperature field，the degree of reserve recovery，the variation of water content and the steam zone formation time under different experiment condition，have been obtained.The result shows that for the steam distillation，the displacement effect is the main mechanism in the steam zone，and the reasonable steam flooding pressure conversion is the key to steam flooding and the reservoir heterogeneity has some influence on the effects of steam flooding.
2013, 20(4):79-82.
Abstract:
Permeability and porosity of the sandstone reservoir will change during the waterflooding process which is of great importance to the development of the reservoir.In this paper，we establish a pore scale network modeling method to simulate the formation parameter variation by taking different microcosmic particle variation mechanisms into account such as particle release，particle capture and particle migration in pore-throats.The simulations are conducted to study the formation parameter variation patterns under various conditions.The simulation results indicate that，after a long period of waterflooding，the pore-throat radius distribution has a small change，and the mean pore-throat radius will increase for the reason that part of particles would release from the pore-throat surface and flow out of the formation.During the waterflooding process，the permeability and porosity of the model increase gradually and stays almost steady after a long period.The water injection intensity and bond strength of clay particles will have an influence on the amplitude of variation by affecting the release rate of particles.
Permeability and porosity of the sandstone reservoir will change during the waterflooding process which is of great importance to the development of the reservoir.In this paper，we establish a pore scale network modeling method to simulate the formation parameter variation by taking different microcosmic particle variation mechanisms into account such as particle release，particle capture and particle migration in pore-throats.The simulations are conducted to study the formation parameter variation patterns under various conditions.The simulation results indicate that，after a long period of waterflooding，the pore-throat radius distribution has a small change，and the mean pore-throat radius will increase for the reason that part of particles would release from the pore-throat surface and flow out of the formation.During the waterflooding process，the permeability and porosity of the model increase gradually and stays almost steady after a long period.The water injection intensity and bond strength of clay particles will have an influence on the amplitude of variation by affecting the release rate of particles.
2013, 20(4):83-87.
Abstract:
The Daqing oilfield has entered an extra high water-cut stage.In response to the production situations of sand bodies at late high water-cut stage under dense pattern condition in Daqing oilfield，and based on five core drilling observation wells with close spacing in Beierxi for major research object，the key technology was applied in quantitative characterization of intra-formational bed of channel sandbody on the basis of development demand and technical bottleneck of current intra-formational potential finding.The study defines some essential characteristics of core size heterogeneity，the main contents of which are intra-formational bed of the typical channel sand body.Different types of channel sand body internal sandwich lithology，thickness，sandwich distribution site，dip angle and residual oil distribution are different obviously.The proportion of inter-beds unidentified by logging to total inter-beds is 69.6%.The braided fluvial channel sediments of intra-formational bed in the stability of the sandwich are good，and the meandering channel is the worst.The study of distribution characteristics of intra-formational bed provides a reliable geological basis for releasing the internal remaining oil out of fluvial channel.
The Daqing oilfield has entered an extra high water-cut stage.In response to the production situations of sand bodies at late high water-cut stage under dense pattern condition in Daqing oilfield，and based on five core drilling observation wells with close spacing in Beierxi for major research object，the key technology was applied in quantitative characterization of intra-formational bed of channel sandbody on the basis of development demand and technical bottleneck of current intra-formational potential finding.The study defines some essential characteristics of core size heterogeneity，the main contents of which are intra-formational bed of the typical channel sand body.Different types of channel sand body internal sandwich lithology，thickness，sandwich distribution site，dip angle and residual oil distribution are different obviously.The proportion of inter-beds unidentified by logging to total inter-beds is 69.6%.The braided fluvial channel sediments of intra-formational bed in the stability of the sandwich are good，and the meandering channel is the worst.The study of distribution characteristics of intra-formational bed provides a reliable geological basis for releasing the internal remaining oil out of fluvial channel.
21 Research of remaining oil distribution rule of Funing formation，the sixth block of Gaoji oilfield
2013, 20(4):88-92.
Abstract:
At present，the Gaoji oilfield has gone into middle and later stage of exploration.In order to enhance the oil recovery，it is necessary to study the potential of remaining oil.The sixth block is the main block of stable production in Gaoji oilfield.On the basis of fine reservoir description of the sixth block，the Funing formation，based on the research of sedimentary micro-facies，interbeds and flow units in Funing formation of the sixth block，combined with dynamic data，the controlling factor and distribution modes of remaining oil in this area，is analyzed thoroughly herein.The results show that in the vertical section，different combinations of flow units and space allocating relation of interbeds can form different remaining oil enrichment modes；while，on the plane，the remaining oil distribution is mainly determined by sedimentary micro-facies，distributing feature of flow units and plane heterogeneity.On the basis of the identification and distribution on formation mechanism of remaining oil，4 remaining oil types are distinguished in this area，which are micro-facies differential remaining oil，small barrier remaining oil，interlayer remaining oil and flow units oil.Within the sand body of small barrier and interlayer，the overflow shore sand deposition on the wing and space ofⅡ，Ⅲflow unit is enrichment area of remaining oil.On the remaining oil distribution research，it can improve the effect of sixth block by means of injection and ensure Gaoji oilfield’s production.
At present，the Gaoji oilfield has gone into middle and later stage of exploration.In order to enhance the oil recovery，it is necessary to study the potential of remaining oil.The sixth block is the main block of stable production in Gaoji oilfield.On the basis of fine reservoir description of the sixth block，the Funing formation，based on the research of sedimentary micro-facies，interbeds and flow units in Funing formation of the sixth block，combined with dynamic data，the controlling factor and distribution modes of remaining oil in this area，is analyzed thoroughly herein.The results show that in the vertical section，different combinations of flow units and space allocating relation of interbeds can form different remaining oil enrichment modes；while，on the plane，the remaining oil distribution is mainly determined by sedimentary micro-facies，distributing feature of flow units and plane heterogeneity.On the basis of the identification and distribution on formation mechanism of remaining oil，4 remaining oil types are distinguished in this area，which are micro-facies differential remaining oil，small barrier remaining oil，interlayer remaining oil and flow units oil.Within the sand body of small barrier and interlayer，the overflow shore sand deposition on the wing and space ofⅡ，Ⅲflow unit is enrichment area of remaining oil.On the remaining oil distribution research，it can improve the effect of sixth block by means of injection and ensure Gaoji oilfield’s production.
2013, 20(4):91-93.
Abstract:
Multi-layer heterogeneous reservoir is commonly of interlayer interference，and therefore leading to low producing degree，low sweep efficiency and low recovery of waterflooding.The vertical heterogeneity seriously affects efficient development of low permeability reservoirs.The waterflooding experiment of single core and core combined model are carried out in this paper.The average permeability to water of core combined model is similar，so the influence of permeability ratio to the law of the waterflooding sweep is studied as well.The results show that the measured water absorption of core combined model corresponds to the theoretical formula of multi-layer heterogeneous reservoir.The displacement experiment of core combined model can accurately reflect the rule of the waterflooding sweep.As the permeability ratio is larger，the percentage of water absorption in high permeability gradually increases.When the permeability ratio is larger than 9，the injected water can hardly sweep the low permeability layer.
Multi-layer heterogeneous reservoir is commonly of interlayer interference，and therefore leading to low producing degree，low sweep efficiency and low recovery of waterflooding.The vertical heterogeneity seriously affects efficient development of low permeability reservoirs.The waterflooding experiment of single core and core combined model are carried out in this paper.The average permeability to water of core combined model is similar，so the influence of permeability ratio to the law of the waterflooding sweep is studied as well.The results show that the measured water absorption of core combined model corresponds to the theoretical formula of multi-layer heterogeneous reservoir.The displacement experiment of core combined model can accurately reflect the rule of the waterflooding sweep.As the permeability ratio is larger，the percentage of water absorption in high permeability gradually increases.When the permeability ratio is larger than 9，the injected water can hardly sweep the low permeability layer.
2013, 20(4):94-98.
Abstract:
Casing damage has been frequently occurring in the oilfield development process，especially in the late period of the development.Casing is damaged by various causes，including both geological and engineering factors.To understand the causes of casing damage，and to take effective measures to protect the casing，a comprehensive analysis is carried out on the formation geology and down-hole conditions.Firstly，the mathematical-physical models are established corresponding respectively to the elastic，plastic and fluid-solid coupling medium under the perforating conditions，by considering the combination of casing，cement and formation as an elastic or plastic medium.Secondly，a simulation analysis is conducted on the casing forces impact by perforating，cement and formation lithology and stresses.The cement elastic property and thickness may reduce the casing load.The formation plastic property and rheology have considerable influences on the casing stresses.The formation pressure changes may cause the changes of casing stresses.It might be possible to take some measurements to prevent the occurrence of casing damage，such as improving cementing quality，optimizing perforating direction，reasonable selecting injection pressure.
Casing damage has been frequently occurring in the oilfield development process，especially in the late period of the development.Casing is damaged by various causes，including both geological and engineering factors.To understand the causes of casing damage，and to take effective measures to protect the casing，a comprehensive analysis is carried out on the formation geology and down-hole conditions.Firstly，the mathematical-physical models are established corresponding respectively to the elastic，plastic and fluid-solid coupling medium under the perforating conditions，by considering the combination of casing，cement and formation as an elastic or plastic medium.Secondly，a simulation analysis is conducted on the casing forces impact by perforating，cement and formation lithology and stresses.The cement elastic property and thickness may reduce the casing load.The formation plastic property and rheology have considerable influences on the casing stresses.The formation pressure changes may cause the changes of casing stresses.It might be possible to take some measurements to prevent the occurrence of casing damage，such as improving cementing quality，optimizing perforating direction，reasonable selecting injection pressure.
2013, 20(4):99-101.
Abstract:
The heavy oil wells are faced with problems such as high temperature and corrosion in the process of development of ISC in Xinjiang oilfield.This article optimally designed a set of cement system of resistant CO2 corrosion in the high temperature conditions.The indoor evaluation test results showed that the compressive strength of cement stone is 13.8 MPa after the high temperature and CO2 corrosion maintenance，the strength corresponded to the security of analysis of the stress state.The permeability and porosity of cement stone suffered little change，the morphology of cement stone was density and the structure was homogeneous after the stone cement corrosion.It also had good strength and toughness and properties，so it could meet the requirements of high temperature cementing project.This cement system used in 9 wells in Xinjiang oilfield，the results showed that the cementing quality achieved 100%，it ensured the cement quality and production safety and provide vast space to improve heavy oil recovery for Xinjiang old oilfield.
The heavy oil wells are faced with problems such as high temperature and corrosion in the process of development of ISC in Xinjiang oilfield.This article optimally designed a set of cement system of resistant CO2 corrosion in the high temperature conditions.The indoor evaluation test results showed that the compressive strength of cement stone is 13.8 MPa after the high temperature and CO2 corrosion maintenance，the strength corresponded to the security of analysis of the stress state.The permeability and porosity of cement stone suffered little change，the morphology of cement stone was density and the structure was homogeneous after the stone cement corrosion.It also had good strength and toughness and properties，so it could meet the requirements of high temperature cementing project.This cement system used in 9 wells in Xinjiang oilfield，the results showed that the cementing quality achieved 100%，it ensured the cement quality and production safety and provide vast space to improve heavy oil recovery for Xinjiang old oilfield.
2013, 20(4):102-104.
Abstract:
The accurate prediction of fracture geometry parameters is the base for compound perforation optimization design and production evaluation.The deflagration gas filtration and multi-fracture will affect fracture propagation in the implementation of compound perforation.Combined with the theory of fluid mechanics，elastic mechanics and linear elastic fracture mechanics，the model of fracture propagation is developed overall considering the effect of deflagration gas filtration and multi-fracture.A function with multiple variables describing gas pressure distribution in crack is proposed herein to realize the numerical resolution of the model using the iteration method，and the dynamic change law of fracture geometry with time is obtained.The results of example show that，the formation permeability and the number of fractures have high influence on the fracture propagation.Ignoring deflagration gas filtration and multi-fracture will result in higher calculation values of fracture length and the relative errors will amplify with the increase of the formation permeability and the number of fractures.
The accurate prediction of fracture geometry parameters is the base for compound perforation optimization design and production evaluation.The deflagration gas filtration and multi-fracture will affect fracture propagation in the implementation of compound perforation.Combined with the theory of fluid mechanics，elastic mechanics and linear elastic fracture mechanics，the model of fracture propagation is developed overall considering the effect of deflagration gas filtration and multi-fracture.A function with multiple variables describing gas pressure distribution in crack is proposed herein to realize the numerical resolution of the model using the iteration method，and the dynamic change law of fracture geometry with time is obtained.The results of example show that，the formation permeability and the number of fractures have high influence on the fracture propagation.Ignoring deflagration gas filtration and multi-fracture will result in higher calculation values of fracture length and the relative errors will amplify with the increase of the formation permeability and the number of fractures.
2013, 20(4):105-110.
Abstract:
In the process of Hydraulic fracture in fractured formation，the interaction between hydraulic fracture and natural fractures made the natural fracture open or shear slip，which leads to the fluid loss in fractured reservoirs dramatically，at the same time，the hydraulic fracturing risk increased greatly.However，at present most of the leak-off models aims at homogeneous formation only.On the basis of natural fracture dynamic loss process，this paper builds a natural fracture leak-off physical model.Based on the combined pressure continuation and volume conservation，we proposed the leak-off mathematical model which is originated from microscopic understanding of the fluid leak-off mechanization of the fractured formation.We programed in the light of the idea and method shown above in this paper.The calculated results of model shows fracturing fluid，the natural fractures and construction parameters can affect fluid loss.Through calculating and analyzing the affecting factors，the conclusion is that the model can fit to practical project，and it has a strong engineering significance.
In the process of Hydraulic fracture in fractured formation，the interaction between hydraulic fracture and natural fractures made the natural fracture open or shear slip，which leads to the fluid loss in fractured reservoirs dramatically，at the same time，the hydraulic fracturing risk increased greatly.However，at present most of the leak-off models aims at homogeneous formation only.On the basis of natural fracture dynamic loss process，this paper builds a natural fracture leak-off physical model.Based on the combined pressure continuation and volume conservation，we proposed the leak-off mathematical model which is originated from microscopic understanding of the fluid leak-off mechanization of the fractured formation.We programed in the light of the idea and method shown above in this paper.The calculated results of model shows fracturing fluid，the natural fractures and construction parameters can affect fluid loss.Through calculating and analyzing the affecting factors，the conclusion is that the model can fit to practical project，and it has a strong engineering significance.
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