Horizontal shale gas well fracturing is mostly carried out by pumping bridge plugs.In the case of casing deformation,the bridge plug can not be pumped down to the designated position,so the hole sections below the def...Horizontal shale gas well fracturing is mostly carried out by pumping bridge plugs.In the case of casing deformation,the bridge plug can not be pumped down to the designated position,so the hole sections below the deformation could not be stimulated according to the design program.About 30%of horizontal shale gas wells in the Changning and Weiyuan Blocks,Sichuan Basin,suffer various casing deformation after fracturing.Previously,the hole sections which could not be stimulated due to casing deformation were generally abandoned.As a result,the resources controlled by shale gas wells weren't exploited effectively and the fracturing effect was impacted greatly.There are a lot of difficulties in investigating casing deformation,such as complex mechanisms,various influencing factors and unpredictable deformation time.Therefore,it is especially important to seek a staged fracturing technology suitable for the casing deformation sections.In this paper,the staged fracturing technology with sand plugs inside fractures and the staged fracturing technology with temporary plugging balls were tested in casing deformation wells.The staged fracturing technology with sand plugs inside fractures was carried out in the mode of single-stage perforation and single-stage fracturing.The staged fracturing technology with temporary plugging balls was conducted in the mode of single perforation,continuous fracturing and staged ball dropping.Then,two kinds of technologies were compared in terms of their advantages and disadvantages.Finally,they were tested on site.According to the pressure response,the pressure monitoring of the adjacent wells and the microseismic monitoring in the process of actual fracturing,both technologies are effective in the stimulation of the casing deformation sections,realizing well control reserves efficiently and guaranteeing fracturing effects.展开更多
In the Southeastern Sichuan Basin,the deep shale reservoirs(with vertical depth over 2800 m)are complicated and diverse in reservoir mineral compositions and pore structural characteristics,with the obvious rock plast...In the Southeastern Sichuan Basin,the deep shale reservoirs(with vertical depth over 2800 m)are complicated and diverse in reservoir mineral compositions and pore structural characteristics,with the obvious rock plasticity and nonlinear fracturing features and the high absolute difference between maximum and minimum principal stresses,due to the effect of geological setting and diagenesis.Consequently,staged fracturing operations often suffer from high fracturing pressure and propagating pressure,small fracture width,low sandefluid ratio and fracture conductivity and difficult formation of volume fractures,which seriously influence the post-fracturing shale gas productivity.In this paper,a new combined fracturing mode(pretreatment acid+gelled fluid+slickwater+gelled fluid)and its supporting technologies were developed after a series of analysis and studies on deep rocks in terms of mechanical property,earth stress characteristics,fracturing characteristics and fracture morphology characteristics.Field application shows that geologic breakthrough was realized in Longmaxi Fm of Lower Silurian in Well Dingye 2HF,with absolute open flow(AOF)of 10.5×10^(4)m^(3)/d after fracturing.And it was expected to reach commercial breakthrough in Qiongzhusi Fm of Lower Cambrian in Well Jinye 1HF,with AOF of 10.5×10^(4)m^(3)/d after fracturing.Finally,the following conclusions are reached.First,it is hard to form complex fractures in deep shale and the fracturing technologies applicable for it should be different from those used in midedeep zones.Second,the established fracturing pressure model can provide an effective way for deep-zone fracturing pressure prediction.Third,reducing operation pressure is one of the key measures to ensure successful deep-zone fracturing.Fourth,besides good material basis,it is crucial to increase the complexity of induced fractures and generate high-conductivity fractures in order to guarantee successful fracturing in deep shale.展开更多
When horizontal well staged cluster fracturing is applied in shale gas reservoirs,the cluster spacing is essential to fracturing performance.If the cluster spacing is too small,the stimulated area between major fractu...When horizontal well staged cluster fracturing is applied in shale gas reservoirs,the cluster spacing is essential to fracturing performance.If the cluster spacing is too small,the stimulated area between major fractures will be overlapped,and the efficiency of fracturing stimulation will be decreased.If the cluster spacing is too large,the area between major fractures cannot be stimulated completely and reservoir recovery extent will be adversely impacted.At present,cluster spacing design is mainly based on the static model with the potential reservoir stimulation area as the target,and there is no cluster spacing design method in accordance with the actual fracturing process and targets dynamic stimulated reservoir volume(SRV).In this paper,a dynamic SRV calculation model for cluster fracture propagation was established by analyzing the coupling mechanisms among fracture propagation,fracturingfluid loss and stress.Then,the cluster spacing was optimized to reach the target of the optimal SRVs.This model was applied for validation on site in the Jiaoshiba shale gasfield in the Fuling area of the Sichuan Basin.The key geological engineering parameters influencing the optimal cluster spacing intervals were analyzed.The reference charts for the optimal cluster spacing design were prepared based on the geological characteristics of south and north blocks in the Jiaoshiba shale gasfield.It is concluded that the cluster spacing optimal design method proposed in this paper is of great significance in overcoming the blindness in current cluster perforation design and guiding the optimal design of volume fracturing in shale gas reservoirs.展开更多
Due to downhole complexities,shale-gas horizontal well fracturing in the Sichuan Basin suffered from casing deformation and failure to apply the technique of cable-conveyed perforation bridge plug.In view of these pro...Due to downhole complexities,shale-gas horizontal well fracturing in the Sichuan Basin suffered from casing deformation and failure to apply the technique of cable-conveyed perforation bridge plug.In view of these problems,a new technique of staged volume fracturing with temporary plugging by sand filling is employed.Based on theoretical analyses and field tests,a design of optimized parameters of coiled tubingconveyed multi-cluster sand-blasting perforation and temporary plugging by sand filling was proposed.It was applied in the horizontalWell ZJ-1 in which casing deformation occurred.The following results are achieved in field operations.First,this technique enables selective staged fracturing in horizontal sections.Second,this technique can realize massive staged fracturing credibly without mechanical plugging,with the operating efficiency equivalent to the conventional bridge plug staged fracturing.Third,full-hole is preserved after fracturing,thus it is possible to directly conduct an open flow test without time consumption of a wiper trip.The staged volume fracturing with temporary plugging by sand filling facilitated the 14-stage fracturing in Well ZJ-1,with similar SRV to that achieved by conventional bridge plug staged fracturing and higher gas yield than neighboring wells on the same well pad.Thus,a new and effective technique is presented in multi-cluster staged volume fracturing of shale gas horizontal wells.展开更多
Horizontal well intensive fracturing is a critical technology used to stimulate unconventional oil and gas reservoirs.Accurate prediction of wellbore breakdown pressure is conducive to optimal fracturing design and im...Horizontal well intensive fracturing is a critical technology used to stimulate unconventional oil and gas reservoirs.Accurate prediction of wellbore breakdown pressure is conducive to optimal fracturing design and improvement of the reservoir stimulation effect.In this work,the three-dimensional displacement discontinuity method(DDM)is used to characterize fracture deformation and fracture closure after the pumping pressure relief.The influences of key parameters such as the minimum horizontal principal stress,fracture spacing,the Young's modulus,the Poisson's ratio and pumping pressure on the breakdown pressure are analyzed.The results show that,assuming that the fracture half-length is a,the breakdown pressure outside the fracture surface area increases significantly within 2a in the direction of the minimum horizontal principal stress and a in the directions of the vertical stress and maximum horizontal principal stress before pressure relief.The breakdown pressure of the modified zipper-type fracturing in the later stage is lower.When the fracture spacing is small,the fracture breakdown pressure decreases after the modified zipper-type fracturing of two horizontal wells.The fracture breakdown pressure of the first fractured well reaches a maximum when the fracture spacing is a-1.5a,and the breakdown pressure decreases with increasing well spacing.展开更多
The carbonate gas reservoir of the fourth Member of Upper Sinian Dengying Formation(hereinafter referred as“Deng 4 Member”)is characterized by deep burial,high temperature,low porosity,low permeability and strong he...The carbonate gas reservoir of the fourth Member of Upper Sinian Dengying Formation(hereinafter referred as“Deng 4 Member”)is characterized by deep burial,high temperature,low porosity,low permeability and strong heterogeneity in the Gaoshiti-Moxi area of the central Sichuan Basin.In order to effectively enhance the well productivity and gas reservoir development benefits,this paper defines the reservoir stimulation factor by comprehensively considering the drilling,logging and well type characteristic parameters,to carry out quantitative reservoir evaluation.Then,the refined segmentation method was developed by fully considering the reservoir stimulation factor,in-situ stress and borehole condition.In addition,the differential acid fracturing technology was prepared for different types of reservoirs.On this basis,the specified staged acid fracturing technology of horizontal well for strong-heterogeneity carbonate reservoirs was developed and then applied in the field.And the following research results were obtained.First,the reservoir stimulation factor(y)can be used to accurately evaluate the reservoir characteristics.The high quality reservoir has y≥1.0,the moderate reservoir has 0.5≤y<1.0,and the low quality reservoir has y˂0.5.Second,the specified staged acid fracturing technology considering the influence of reservoir stimulation factor,in-situ stresses and borehole condition comprehensively is formed.Stimulation measures are applied specifically in different types of reservoir intervals to give full play to the resource potential in each stimulation segment of a long horizontal section,so as to improve the production rate of natural gas reserves in strong-heterogeneity reservoirs.Third,the acid fracturing technology suitable for different types of reservoirs is also different.It is recommended to adopt acid fracturing with gelled acid or diverting acid in high quality reservoirs,acid fracturing with self-generating acid prepad in moderate reservoirs,and acid fracturing with 2–3 stages alternate injection of self-generating acid prepad and gelled acid in low quality reservoirs.Fourth,69 wells in the production area of the platform margin of Deng 4 Member gas reservoir in Gaoshiti-Moxi area are stimulated with specified staged acid fracturing.The average absolute open flow is 127.6×10^(4)m^(3)/d,which is 46.5%higher than that in the early stage of gas reservoir development.In conclusion,the research results provide remarkable stimulation effects,increase the single well gas production greatly and effectively support the efficient development of Deng 4 Member gas reservoir in the Gaoshiti-Moxi area.展开更多
The strike-slip fault system in the central Tarim Craton controls a complex petroleum system with estimated reserves exceeding 1×10^(9)t,the fault-related fractures are important for hydrocarbon accumulation.In t...The strike-slip fault system in the central Tarim Craton controls a complex petroleum system with estimated reserves exceeding 1×10^(9)t,the fault-related fractures are important for hydrocarbon accumulation.In this paper,the basic parameters such as density and width of fractures are counted and classified,and the effects of fractures on reservoirs are analyzed.The results show that:(1)Structural fractures and stylolite were widely developed in Halahatang area and experienced at least three stages of activity based on the infilling materials and crosscutting relationship.(2)Fracture density,width,aperture,and dip angle vary in different wells,but the relationship between the above parameters and the distance to the fault core indicates the fracture differences in the fault damage zone and further provides a method to divide the inner units in the fault damage zone.In addition,oil and gas wells with high production mainly concentrate in the inner unit.(3)The infilling materials and degree of fractures vary.Fractures formed in the early stage are more filled and less open,while the fractures formed in the late stage are relatively less filled and more open.(4)Fractures improve porosity to a certain extent but greatly increase permeability,especially in the inner zone of fault damage zone with large quantity,multiple inclinations,less filling and large width.These features contribute to the formation of a higher-quality reservoir,further improving oil and gas production.This paper provides a quantitative characterization method for the study of strike-slip fault-related fracture-caved reservoirs,and points out that fault damage zone,especially the inner zone of the fault damage zone,is the potential goal for oil and gas exploration.展开更多
Determining reasonable fracturing stage spacing is the key to horizontal well fracturing.Different from traditional stage spacing optimization methods based on the principle of maximum stimulated reservoir volume,in t...Determining reasonable fracturing stage spacing is the key to horizontal well fracturing.Different from traditional stage spacing optimization methods based on the principle of maximum stimulated reservoir volume,in this paper,by considering the integrity of the wellbore interface,a fracture propagation model was established based on displacement discontinuity method and the competition mechanism of multifracture joint expansion,leading to the proposal of an unequal stage spacing optimization model.The results show that in the first stage,the interfacial fractures spread symmetrically along the axis of the central point during that stage,while in the second and subsequent stages,the interfacial fractures of each cluster extend asymmetrically along the left and right sides.There are two kinds of interface connectivity behaviour:in one,the existing fractures first extend and connect within the stage,and in the other,the fractures first extend in the direction close to the previous stage,with the specific behaviour depending on the combined effect of stress shadow and flow competition during hydraulic fracture expansion.The stage spacing is positively correlated with the number of fractures and Young’s modulus of the cement and formation and is negatively correlated with the cluster spacing and horizontal principal stress difference.The sensitivity is the strongest when the Young’s modulus of the cement sheath is 10-20 GPa,and the sensitivity of the horizontal principal stress difference is the weakest.展开更多
It is difficult to build an effective water flooding displacement pressure system in the middle section of a horizontal well in an ultra-low permeability sandstone reservoir.To solve this problem,this study proposes t...It is difficult to build an effective water flooding displacement pressure system in the middle section of a horizontal well in an ultra-low permeability sandstone reservoir.To solve this problem,this study proposes to use packers,sealing cannula and other tools in the same horizontal well to inject water in some fractures and produce oil from other fractures.This new energy supplement method forms a segmental synchronous injection-production system in a horizontal well.The method can reduce the distance between the injection end and the production end,and quickly establish an effective displacement system.Changing the displacement between wells to displacement between horizontal well sections,and point water flooding to linear uniform water flooding,the method can enhance water sweeping volume and shorten waterflooding response period.The research shows that:(1)In the synchronous injection and production of horizontal well in an ultra-low-permeability sandstone reservoir,the water injection section should select the section where the natural fractures and artificial fractures are in the same direction or the section with no natural fractures,and the space between two sections should be 60?80 m.(2)In addition to controlling injection pressure,periodic water injection can be taken to reduce the risk of re-opening and growth of natural fractures or formation fracture caused by the gradual increase of water injection pressure with water injection going on.(3)Field tests have verified that this method can effectively improve the output of single well and achieve good economic benefits,so it can be widely used in the development of ultra-low permeability sandstone reservoirs.展开更多
Fracturing operations in shale gas reservoirs of the Sichuan-Chongqing area are frequented by casing deformation,failures in delivery of mechanical staging tools and other down-hole complexities.In addition,limitation...Fracturing operations in shale gas reservoirs of the Sichuan-Chongqing area are frequented by casing deformation,failures in delivery of mechanical staging tools and other down-hole complexities.In addition,limitation in volumes of tail-in proppant in the matrix area significantly restricts the conductivity in the near zones of the wellbore.Eventually,flowback performance and productivity of shale gas horizontal wells are negatively affected.With consideration to the limitations in the implementation of the mechanical staging technique with bridge plug for shale gas development in the Sichuan-Chongqing area,the technique of multi-stage sand filling stimulation in horizontal wells was proposed to solve the above-mentioned problems.By filling sands in fractures,it is possible to divert fluids to maintain long-term high conductivity of fractures,which is the key to satisfactory EOR performances.By introducing the Hertz contact and fractal theory in the analysis of sand plug strength,and in combination of lab engineering simulation test results,the mechanical model for sand plugs in fractures with proppant was constructed.In terms of strength criteria and friction,the stability criteria of sand plug were put forward.Thus,the permeability fractural model for sand plugs in fractures was perfected.Test results show that the stability of sand plug in the earlier stage of production is mainly affected by fluid washing during flowback,so it is necessary to control the flowback rate strictly.In the later stage of production,the stability is mainly affected by fracture closure stress and flow pressure,so it is necessary to enhance the yield strength of proppant to maintain high conductivity of fractures.In conclusion,the multi-stage sand filling stimulation provides a new technique for multi-stage clustering fracturing operations in shale gas horizontal well development.展开更多
As the excavation of roadway, new fractures will be formed and the pre-existing fractures extend with the redistribution of stress in surrounding rocks. Eventually, fracture zone and bed separation are formed in rocks...As the excavation of roadway, new fractures will be formed and the pre-existing fractures extend with the redistribution of stress in surrounding rocks. Eventually, fracture zone and bed separation are formed in rocks because of the developed fractures. Therefore, mastering the fracture evolution of surrounding rocks is very important to maintain the stability of roadway. The surrounding rocks of main haulage road- way in a certain coal mine is so broken and loose that the supporting is very difficult. Based on compre- hensive anal[ysis of the engineering geological conditions, a sight instrument was used to observe the fractures of internal surrounding rocks, Four indices, i.e., the width of fracture zone W, the number of fractures n, the width of fractures d and rock fracture designation RFD, are put forward to evaluate the fracture dewelopment. According to the evolution rules of the soft rock roadway from this paper, control principles by stages and by regions are presented through the research. At the same time, the best time of grouting reinforcement is determined on the basis of fracture saturation. Field practice shows that the roadway can satisfy normal production during service periods by suitable first support and grouting reinforcement.展开更多
In this study,acid fracturing treatments were simulated for a tight limestone reservoir within a shale formation using FRACPRO software.The purpose was to investigate the optimum acid fracturing design that leads to a...In this study,acid fracturing treatments were simulated for a tight limestone reservoir within a shale formation using FRACPRO software.The purpose was to investigate the optimum acid fracturing design that leads to a higher fracture etched length and width,and higher fracture conductivity.Moreover,the impact of the rock-acid contact time and whether to consider a post-flush or fluids flowback,on the acid fracturing outcomes were also investigated.A simple geological model was constructed which consists of different lithological layers.Different acid fracturing design scenarios were considered starting from a single stage of acid injection to multi-stage treatment.In multi-stage acid treatment,alternate acid-slickwater injection was considered.Plain HCl acids with different concentrations and other acids that are already included in FRACPRO database were used.The results showed that the acid loss during post-flush is among the main problems of the acid fracturing in tight carbonate shale reservoir.For the single stage of acid injection,it is recommended to flow back the acid after well shut-in instead of considering a post-flush stage.The multi-stage alternate acid slickwater injection reduces or even eliminated the acid loss.However,it is recommended to inject a slickwater before well shut-in to reduce the rock-acid contact time,thus reducing the formation damage.The results also showed that the created fracture etched width decreases and the fracture etched length increases as the fracturing stages increase.In this study,because of the low carbonate layer permeability and compressive strength,a two-stage alternate 28%HCl and slickwater injection with a post-flush stage is recommended.展开更多
Although shale gas resources are abundant in China,commercial discoveries have not been made before the discovery of Fuling Shale Gas Field.SINOPEC has done lots of theoretical and technological studies on marine shal...Although shale gas resources are abundant in China,commercial discoveries have not been made before the discovery of Fuling Shale Gas Field.SINOPEC has done lots of theoretical and technological studies on marine shale gas development in China.Research shows shale gas has dynamic accumulations with early preservation and late reconstruction and proposes high-quality shale developed in deep-water shelf as the base and good preservation conditions as the key factor for shale gas accumulation.Key technologies and facilities were developed for geophysical survey of shale gas,design and optimization of shale gas development,drilling and completion of horizontal wells,and fracturing stimulation.As the first and largest shale gas field in China,the discovery and successful development of Fuling Shale Gas Filed has made China the first country to achieve large-scale development of shale gas after North America.By August 2017,Fuling Shale Gas Field had declared 6008.14×10^(8)m^(3) proven reserves,76.8×10^(8)m^(3) production capacity and 133.9×10^(8)m^(3) cumulative production.The construction of Fuling Shale Gas Field with high level,high speed and high quality has been a good example of shale gas development in China.Its successful experiences can be used to other fields and play an important role in optimizing energy structure and improving environment.展开更多
基金Project supported by the National Key Basic Research and Development Program(973 Program)“Theory and Technology Adaptability of Shale Gas Development in Typical Marine Blocks in South China”(No.2013CB228006).
文摘Horizontal shale gas well fracturing is mostly carried out by pumping bridge plugs.In the case of casing deformation,the bridge plug can not be pumped down to the designated position,so the hole sections below the deformation could not be stimulated according to the design program.About 30%of horizontal shale gas wells in the Changning and Weiyuan Blocks,Sichuan Basin,suffer various casing deformation after fracturing.Previously,the hole sections which could not be stimulated due to casing deformation were generally abandoned.As a result,the resources controlled by shale gas wells weren't exploited effectively and the fracturing effect was impacted greatly.There are a lot of difficulties in investigating casing deformation,such as complex mechanisms,various influencing factors and unpredictable deformation time.Therefore,it is especially important to seek a staged fracturing technology suitable for the casing deformation sections.In this paper,the staged fracturing technology with sand plugs inside fractures and the staged fracturing technology with temporary plugging balls were tested in casing deformation wells.The staged fracturing technology with sand plugs inside fractures was carried out in the mode of single-stage perforation and single-stage fracturing.The staged fracturing technology with temporary plugging balls was conducted in the mode of single perforation,continuous fracturing and staged ball dropping.Then,two kinds of technologies were compared in terms of their advantages and disadvantages.Finally,they were tested on site.According to the pressure response,the pressure monitoring of the adjacent wells and the microseismic monitoring in the process of actual fracturing,both technologies are effective in the stimulation of the casing deformation sections,realizing well control reserves efficiently and guaranteeing fracturing effects.
基金Project supported by Sinopec Science and Technology Project“Optimized stimulation of shale gas zones in Fuling block”(Grant No.P14091).
文摘In the Southeastern Sichuan Basin,the deep shale reservoirs(with vertical depth over 2800 m)are complicated and diverse in reservoir mineral compositions and pore structural characteristics,with the obvious rock plasticity and nonlinear fracturing features and the high absolute difference between maximum and minimum principal stresses,due to the effect of geological setting and diagenesis.Consequently,staged fracturing operations often suffer from high fracturing pressure and propagating pressure,small fracture width,low sandefluid ratio and fracture conductivity and difficult formation of volume fractures,which seriously influence the post-fracturing shale gas productivity.In this paper,a new combined fracturing mode(pretreatment acid+gelled fluid+slickwater+gelled fluid)and its supporting technologies were developed after a series of analysis and studies on deep rocks in terms of mechanical property,earth stress characteristics,fracturing characteristics and fracture morphology characteristics.Field application shows that geologic breakthrough was realized in Longmaxi Fm of Lower Silurian in Well Dingye 2HF,with absolute open flow(AOF)of 10.5×10^(4)m^(3)/d after fracturing.And it was expected to reach commercial breakthrough in Qiongzhusi Fm of Lower Cambrian in Well Jinye 1HF,with AOF of 10.5×10^(4)m^(3)/d after fracturing.Finally,the following conclusions are reached.First,it is hard to form complex fractures in deep shale and the fracturing technologies applicable for it should be different from those used in midedeep zones.Second,the established fracturing pressure model can provide an effective way for deep-zone fracturing pressure prediction.Third,reducing operation pressure is one of the key measures to ensure successful deep-zone fracturing.Fourth,besides good material basis,it is crucial to increase the complexity of induced fractures and generate high-conductivity fractures in order to guarantee successful fracturing in deep shale.
基金Project supported by the National Natural Science Foundation for Young Scientists of China(No.51404204)National Science and Technology Major Project(No.2016ZX05060)Sinopec Research Project(No.31400026-16-ZC0607-0013).
文摘When horizontal well staged cluster fracturing is applied in shale gas reservoirs,the cluster spacing is essential to fracturing performance.If the cluster spacing is too small,the stimulated area between major fractures will be overlapped,and the efficiency of fracturing stimulation will be decreased.If the cluster spacing is too large,the area between major fractures cannot be stimulated completely and reservoir recovery extent will be adversely impacted.At present,cluster spacing design is mainly based on the static model with the potential reservoir stimulation area as the target,and there is no cluster spacing design method in accordance with the actual fracturing process and targets dynamic stimulated reservoir volume(SRV).In this paper,a dynamic SRV calculation model for cluster fracture propagation was established by analyzing the coupling mechanisms among fracture propagation,fracturingfluid loss and stress.Then,the cluster spacing was optimized to reach the target of the optimal SRVs.This model was applied for validation on site in the Jiaoshiba shale gasfield in the Fuling area of the Sichuan Basin.The key geological engineering parameters influencing the optimal cluster spacing intervals were analyzed.The reference charts for the optimal cluster spacing design were prepared based on the geological characteristics of south and north blocks in the Jiaoshiba shale gasfield.It is concluded that the cluster spacing optimal design method proposed in this paper is of great significance in overcoming the blindness in current cluster perforation design and guiding the optimal design of volume fracturing in shale gas reservoirs.
基金supported by the National Major Science and Technology Project“Experimental study on shale gas production in Zhaotong County,Yunnan Province”(No.:2012ZX0518-006)Major Project of CNPC“Field test of shale gas drilling and production engineering technology in Zhaotong demonstration zone”(No.:2012F-47-02).
文摘Due to downhole complexities,shale-gas horizontal well fracturing in the Sichuan Basin suffered from casing deformation and failure to apply the technique of cable-conveyed perforation bridge plug.In view of these problems,a new technique of staged volume fracturing with temporary plugging by sand filling is employed.Based on theoretical analyses and field tests,a design of optimized parameters of coiled tubingconveyed multi-cluster sand-blasting perforation and temporary plugging by sand filling was proposed.It was applied in the horizontalWell ZJ-1 in which casing deformation occurred.The following results are achieved in field operations.First,this technique enables selective staged fracturing in horizontal sections.Second,this technique can realize massive staged fracturing credibly without mechanical plugging,with the operating efficiency equivalent to the conventional bridge plug staged fracturing.Third,full-hole is preserved after fracturing,thus it is possible to directly conduct an open flow test without time consumption of a wiper trip.The staged volume fracturing with temporary plugging by sand filling facilitated the 14-stage fracturing in Well ZJ-1,with similar SRV to that achieved by conventional bridge plug staged fracturing and higher gas yield than neighboring wells on the same well pad.Thus,a new and effective technique is presented in multi-cluster staged volume fracturing of shale gas horizontal wells.
基金supported by the National Natural Science Foundation of China,China(No.52074250).
文摘Horizontal well intensive fracturing is a critical technology used to stimulate unconventional oil and gas reservoirs.Accurate prediction of wellbore breakdown pressure is conducive to optimal fracturing design and improvement of the reservoir stimulation effect.In this work,the three-dimensional displacement discontinuity method(DDM)is used to characterize fracture deformation and fracture closure after the pumping pressure relief.The influences of key parameters such as the minimum horizontal principal stress,fracture spacing,the Young's modulus,the Poisson's ratio and pumping pressure on the breakdown pressure are analyzed.The results show that,assuming that the fracture half-length is a,the breakdown pressure outside the fracture surface area increases significantly within 2a in the direction of the minimum horizontal principal stress and a in the directions of the vertical stress and maximum horizontal principal stress before pressure relief.The breakdown pressure of the modified zipper-type fracturing in the later stage is lower.When the fracture spacing is small,the fracture breakdown pressure decreases after the modified zipper-type fracturing of two horizontal wells.The fracture breakdown pressure of the first fractured well reaches a maximum when the fracture spacing is a-1.5a,and the breakdown pressure decreases with increasing well spacing.
基金supported by China National Petroleum Corporation's major scientific and technological project“Research and Application of Reservoir Stimulation Technology for Deep HPHT Sour Gas Reservoirs in the Sichuan Basin”(No.:2016E-0609).
文摘The carbonate gas reservoir of the fourth Member of Upper Sinian Dengying Formation(hereinafter referred as“Deng 4 Member”)is characterized by deep burial,high temperature,low porosity,low permeability and strong heterogeneity in the Gaoshiti-Moxi area of the central Sichuan Basin.In order to effectively enhance the well productivity and gas reservoir development benefits,this paper defines the reservoir stimulation factor by comprehensively considering the drilling,logging and well type characteristic parameters,to carry out quantitative reservoir evaluation.Then,the refined segmentation method was developed by fully considering the reservoir stimulation factor,in-situ stress and borehole condition.In addition,the differential acid fracturing technology was prepared for different types of reservoirs.On this basis,the specified staged acid fracturing technology of horizontal well for strong-heterogeneity carbonate reservoirs was developed and then applied in the field.And the following research results were obtained.First,the reservoir stimulation factor(y)can be used to accurately evaluate the reservoir characteristics.The high quality reservoir has y≥1.0,the moderate reservoir has 0.5≤y<1.0,and the low quality reservoir has y˂0.5.Second,the specified staged acid fracturing technology considering the influence of reservoir stimulation factor,in-situ stresses and borehole condition comprehensively is formed.Stimulation measures are applied specifically in different types of reservoir intervals to give full play to the resource potential in each stimulation segment of a long horizontal section,so as to improve the production rate of natural gas reserves in strong-heterogeneity reservoirs.Third,the acid fracturing technology suitable for different types of reservoirs is also different.It is recommended to adopt acid fracturing with gelled acid or diverting acid in high quality reservoirs,acid fracturing with self-generating acid prepad in moderate reservoirs,and acid fracturing with 2–3 stages alternate injection of self-generating acid prepad and gelled acid in low quality reservoirs.Fourth,69 wells in the production area of the platform margin of Deng 4 Member gas reservoir in Gaoshiti-Moxi area are stimulated with specified staged acid fracturing.The average absolute open flow is 127.6×10^(4)m^(3)/d,which is 46.5%higher than that in the early stage of gas reservoir development.In conclusion,the research results provide remarkable stimulation effects,increase the single well gas production greatly and effectively support the efficient development of Deng 4 Member gas reservoir in the Gaoshiti-Moxi area.
基金supported by the Natural Science Foundation of China-Youth Foundation(42402163)Natural Science Foundation of Sichuan Province of China(2024NSFSC0814)Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(2020CX010101).
文摘The strike-slip fault system in the central Tarim Craton controls a complex petroleum system with estimated reserves exceeding 1×10^(9)t,the fault-related fractures are important for hydrocarbon accumulation.In this paper,the basic parameters such as density and width of fractures are counted and classified,and the effects of fractures on reservoirs are analyzed.The results show that:(1)Structural fractures and stylolite were widely developed in Halahatang area and experienced at least three stages of activity based on the infilling materials and crosscutting relationship.(2)Fracture density,width,aperture,and dip angle vary in different wells,but the relationship between the above parameters and the distance to the fault core indicates the fracture differences in the fault damage zone and further provides a method to divide the inner units in the fault damage zone.In addition,oil and gas wells with high production mainly concentrate in the inner unit.(3)The infilling materials and degree of fractures vary.Fractures formed in the early stage are more filled and less open,while the fractures formed in the late stage are relatively less filled and more open.(4)Fractures improve porosity to a certain extent but greatly increase permeability,especially in the inner zone of fault damage zone with large quantity,multiple inclinations,less filling and large width.These features contribute to the formation of a higher-quality reservoir,further improving oil and gas production.This paper provides a quantitative characterization method for the study of strike-slip fault-related fracture-caved reservoirs,and points out that fault damage zone,especially the inner zone of the fault damage zone,is the potential goal for oil and gas exploration.
基金This work was supported by the Natural Science Foundation of Heilongjiang Province of China(YQ2021E005)the National Natural Science Foundation of China(No.51774094)+2 种基金the Youth Fund Project of National Natural Science Foundation of China(52004065)the Heilongjiang Natural Science Foundation Project(excellent youth project)(YQ2021E006)"Reveal the top"Science and Technology Project of Heilongjiang Province(2021ZZ10-04).
文摘Determining reasonable fracturing stage spacing is the key to horizontal well fracturing.Different from traditional stage spacing optimization methods based on the principle of maximum stimulated reservoir volume,in this paper,by considering the integrity of the wellbore interface,a fracture propagation model was established based on displacement discontinuity method and the competition mechanism of multifracture joint expansion,leading to the proposal of an unequal stage spacing optimization model.The results show that in the first stage,the interfacial fractures spread symmetrically along the axis of the central point during that stage,while in the second and subsequent stages,the interfacial fractures of each cluster extend asymmetrically along the left and right sides.There are two kinds of interface connectivity behaviour:in one,the existing fractures first extend and connect within the stage,and in the other,the fractures first extend in the direction close to the previous stage,with the specific behaviour depending on the combined effect of stress shadow and flow competition during hydraulic fracture expansion.The stage spacing is positively correlated with the number of fractures and Young’s modulus of the cement and formation and is negatively correlated with the cluster spacing and horizontal principal stress difference.The sensitivity is the strongest when the Young’s modulus of the cement sheath is 10-20 GPa,and the sensitivity of the horizontal principal stress difference is the weakest.
基金Supported by the China National Science and Technology Major Project(2016ZX05050)
文摘It is difficult to build an effective water flooding displacement pressure system in the middle section of a horizontal well in an ultra-low permeability sandstone reservoir.To solve this problem,this study proposes to use packers,sealing cannula and other tools in the same horizontal well to inject water in some fractures and produce oil from other fractures.This new energy supplement method forms a segmental synchronous injection-production system in a horizontal well.The method can reduce the distance between the injection end and the production end,and quickly establish an effective displacement system.Changing the displacement between wells to displacement between horizontal well sections,and point water flooding to linear uniform water flooding,the method can enhance water sweeping volume and shorten waterflooding response period.The research shows that:(1)In the synchronous injection and production of horizontal well in an ultra-low-permeability sandstone reservoir,the water injection section should select the section where the natural fractures and artificial fractures are in the same direction or the section with no natural fractures,and the space between two sections should be 60?80 m.(2)In addition to controlling injection pressure,periodic water injection can be taken to reduce the risk of re-opening and growth of natural fractures or formation fracture caused by the gradual increase of water injection pressure with water injection going on.(3)Field tests have verified that this method can effectively improve the output of single well and achieve good economic benefits,so it can be widely used in the development of ultra-low permeability sandstone reservoirs.
基金Project supported by the National Major Science and Technology Project“Demonstrative shale gas exploration and development project in Zhaotong”(No.2017ZX05063004).
文摘Fracturing operations in shale gas reservoirs of the Sichuan-Chongqing area are frequented by casing deformation,failures in delivery of mechanical staging tools and other down-hole complexities.In addition,limitation in volumes of tail-in proppant in the matrix area significantly restricts the conductivity in the near zones of the wellbore.Eventually,flowback performance and productivity of shale gas horizontal wells are negatively affected.With consideration to the limitations in the implementation of the mechanical staging technique with bridge plug for shale gas development in the Sichuan-Chongqing area,the technique of multi-stage sand filling stimulation in horizontal wells was proposed to solve the above-mentioned problems.By filling sands in fractures,it is possible to divert fluids to maintain long-term high conductivity of fractures,which is the key to satisfactory EOR performances.By introducing the Hertz contact and fractal theory in the analysis of sand plug strength,and in combination of lab engineering simulation test results,the mechanical model for sand plugs in fractures with proppant was constructed.In terms of strength criteria and friction,the stability criteria of sand plug were put forward.Thus,the permeability fractural model for sand plugs in fractures was perfected.Test results show that the stability of sand plug in the earlier stage of production is mainly affected by fluid washing during flowback,so it is necessary to control the flowback rate strictly.In the later stage of production,the stability is mainly affected by fracture closure stress and flow pressure,so it is necessary to enhance the yield strength of proppant to maintain high conductivity of fractures.In conclusion,the multi-stage sand filling stimulation provides a new technique for multi-stage clustering fracturing operations in shale gas horizontal well development.
基金provided by the National Natural Science Foundation of China (No. 50974118)the Program for New Century Excellent Talents in University (No. NCET-09-0727)+1 种基金the Program for Post graduates Research Innovation in Universities of Jiangsu Province (No. CX10B_149Z)the Priority Academic Program Development of Jiangsu Higher Education Institutions and the State Key Laboratory of Coal Resources and Mine Safety (No.SKLCRSM08X04)
文摘As the excavation of roadway, new fractures will be formed and the pre-existing fractures extend with the redistribution of stress in surrounding rocks. Eventually, fracture zone and bed separation are formed in rocks because of the developed fractures. Therefore, mastering the fracture evolution of surrounding rocks is very important to maintain the stability of roadway. The surrounding rocks of main haulage road- way in a certain coal mine is so broken and loose that the supporting is very difficult. Based on compre- hensive anal[ysis of the engineering geological conditions, a sight instrument was used to observe the fractures of internal surrounding rocks, Four indices, i.e., the width of fracture zone W, the number of fractures n, the width of fractures d and rock fracture designation RFD, are put forward to evaluate the fracture dewelopment. According to the evolution rules of the soft rock roadway from this paper, control principles by stages and by regions are presented through the research. At the same time, the best time of grouting reinforcement is determined on the basis of fracture saturation. Field practice shows that the roadway can satisfy normal production during service periods by suitable first support and grouting reinforcement.
文摘In this study,acid fracturing treatments were simulated for a tight limestone reservoir within a shale formation using FRACPRO software.The purpose was to investigate the optimum acid fracturing design that leads to a higher fracture etched length and width,and higher fracture conductivity.Moreover,the impact of the rock-acid contact time and whether to consider a post-flush or fluids flowback,on the acid fracturing outcomes were also investigated.A simple geological model was constructed which consists of different lithological layers.Different acid fracturing design scenarios were considered starting from a single stage of acid injection to multi-stage treatment.In multi-stage acid treatment,alternate acid-slickwater injection was considered.Plain HCl acids with different concentrations and other acids that are already included in FRACPRO database were used.The results showed that the acid loss during post-flush is among the main problems of the acid fracturing in tight carbonate shale reservoir.For the single stage of acid injection,it is recommended to flow back the acid after well shut-in instead of considering a post-flush stage.The multi-stage alternate acid slickwater injection reduces or even eliminated the acid loss.However,it is recommended to inject a slickwater before well shut-in to reduce the rock-acid contact time,thus reducing the formation damage.The results also showed that the created fracture etched width decreases and the fracture etched length increases as the fracturing stages increase.In this study,because of the low carbonate layer permeability and compressive strength,a two-stage alternate 28%HCl and slickwater injection with a post-flush stage is recommended.
基金The work was supported by the National Science and Technology Major Project of China(No.2016ZX05060).
文摘Although shale gas resources are abundant in China,commercial discoveries have not been made before the discovery of Fuling Shale Gas Field.SINOPEC has done lots of theoretical and technological studies on marine shale gas development in China.Research shows shale gas has dynamic accumulations with early preservation and late reconstruction and proposes high-quality shale developed in deep-water shelf as the base and good preservation conditions as the key factor for shale gas accumulation.Key technologies and facilities were developed for geophysical survey of shale gas,design and optimization of shale gas development,drilling and completion of horizontal wells,and fracturing stimulation.As the first and largest shale gas field in China,the discovery and successful development of Fuling Shale Gas Filed has made China the first country to achieve large-scale development of shale gas after North America.By August 2017,Fuling Shale Gas Field had declared 6008.14×10^(8)m^(3) proven reserves,76.8×10^(8)m^(3) production capacity and 133.9×10^(8)m^(3) cumulative production.The construction of Fuling Shale Gas Field with high level,high speed and high quality has been a good example of shale gas development in China.Its successful experiences can be used to other fields and play an important role in optimizing energy structure and improving environment.
