This study presents an avant-garde approach for predicting and optimizing production in tight reservoirs,employing a dual-medium unsteady seepage model specifically fashioned for volumetrically fractured horizontal we...This study presents an avant-garde approach for predicting and optimizing production in tight reservoirs,employing a dual-medium unsteady seepage model specifically fashioned for volumetrically fractured horizontal wells.Traditional models often fail to fully capture the complex dynamics associated with these unconventional reservoirs.In a significant departure from these models,our approach incorporates an initiation pressure gradient and a discrete fracture seepage network,providing a more realistic representation of the seepage process.The model also integrates an enhanced fluid-solid interaction,which allows for a more comprehensive understanding of the fluid-structure interactions in the reservoir.This is achieved through the incorporation of improved permeability and stress coupling,leading to more precise predictions of reservoir behavior.The numerical solutions derived from the model are obtained through the sophisticated finite element method,ensuring high accuracy and computational efficiency.To ensure the model’s reliability and accuracy,the outcomes were tested against a real-world case,with results demonstrating strong alignment.A key revelation from the study is the significant difference between uncoupled and fully coupled volumetrically fractured horizontal wells,challenging conventional wisdom in the field.Additionally,the study delves into the effects of stress,fracture length,and fracture number on reservoir production,contributing valuable insights for the design and optimization of tight reservoirs.The findings from this study have the potential to revolutionize the field of tight reservoir prediction and management,offering significant advancements in petroleum engineering.The proposed approach brings forth a more nuanced understanding of tight reservoir systems and opens up new avenues for optimizing reservoir management and production.展开更多
Production decline analysis has been considered as an important method to obtain the flow parameters, reservoir properties and original gas in place. Although advanced Blasingame production decline analysis methods fo...Production decline analysis has been considered as an important method to obtain the flow parameters, reservoir properties and original gas in place. Although advanced Blasingame production decline analysis methods for vertical wells, fractured wells and horizontal wells are widely used, limited study has conducted on Blasingame production decline type curves for multi-fractured horizontal well(MFHW). Based on the perpendicular bisection(PEBI) grids, a numerical model was developed and the solution was obtained using control volume finite element method and the fully implicit method. Blasingame production decline-type curves of the infinitely conductive MFHW were plotted through computer programming. A field case was presented to analyse and verify the model developed. Five flow regimes, including early formation linear flow, early radial flow, compound linear flow, transient flow and pseudo-radial flow, are recognized. Fracture spacing is the main factor that affects early radial flow, compound linear flow and transient flow, the distance from the well to the circular boundary affects the pseudo-radial flow, and the type curves are also significantly affected by the formation permeability, fracture number and fracture half-length. The validation of field case suggests that the Blasingame production decline type curves proposed in this work can be applied to the production decline analysis for MFHW in tight gas reservoirs.展开更多
The production performances of a well with a shale gas reservoir displaying a complex fracture network are simulated.In particular,a micro-seismic cloud diagram is used to describe the fracture network,and accordingly...The production performances of a well with a shale gas reservoir displaying a complex fracture network are simulated.In particular,a micro-seismic cloud diagram is used to describe the fracture network,and accordingly,a production model is introduced based on a multi-scale flow mechanism.A finite volume method is then exploited for the integration of the model equations.The effects of apparent permeability,conductivity,Langmuir volume,and bottom hole pressure on gas well production are studied accordingly.The simulation results show that ignoring the micro-scale flow mechanism of the shale gas leads to underestimating the well gas production.It is shown that after ten years of production,the cumulative gas production difference between the two scenarios with and without considering the micro-scale flow mechanisms is 19.5%.The greater the fracture conductivity,the higher the initial gas production of the gas well and the cumulative gas production.The larger the Langmuir volume,the higher the gas production rate and the cumulative gas production.With the reduction of the bottom hole pressure,the cumulative gas production increases,but the growth rate gradually decreases.展开更多
Currently,most models for multiple fractured horizontal wells(MFHWs)in naturally fractured unconventional reservoirs(NFURs)are based on classical Euclidean models which implicitly assume a uniform distribution of natu...Currently,most models for multiple fractured horizontal wells(MFHWs)in naturally fractured unconventional reservoirs(NFURs)are based on classical Euclidean models which implicitly assume a uniform distribution of natural fractures and that all fractures are homogeneous.While fractal theory provides a powerful method to describe the disorder,heterogeneity,uncertainty and complexity of the NFURs.In this paper,a fractally fractional diffusion model(FFDM)for MFHWs in NFURs is established based on fractal theory and fractional calculus.Particularly,fractal theory is used to describe the heterogeneous,complex fracture network,with consideration of anomalous behavior of diffusion process in NFURs by employing fractional calculus.The Laplace transformation,line source function,dispersion method,and superposition principle are used to solve this new model.The pressure responses in the real time domain are obtained with Stehfest numerical inversion algorithms.The type curves of MFHW with three different outer boundaries are plotted.Sensitivity analysis of some related parameters are discussed as well.This new model provides the relatively more accurate and appropriate evaluation results for pressure transient analysis for MFHWs in NFURs,which could be applied to accurately interpret the real pressure data of an MFHW in field.展开更多
The existing approaches for identifying events in horizontal well fracturing are difficult, time-consuming, inaccurate, and incapable of real-time warning. Through improvement of data analysis and deep learning algori...The existing approaches for identifying events in horizontal well fracturing are difficult, time-consuming, inaccurate, and incapable of real-time warning. Through improvement of data analysis and deep learning algorithm, together with the analysis on data and information of horizontal well fracturing in shale gas reservoirs, this paper presents a method for intelligent identification and real-time warning of diverse complex events in horizontal well fracturing. An identification model for "point" events in fracturing is established based on the Att-BiLSTM neural network, along with the broad learning system (BLS) and the BP neural network, and it realizes the intelligent identification of the start/end of fracturing, formation breakdown, instantaneous shut-in, and other events, with an accuracy of over 97%. An identification model for "phase" events in fracturing is established based on enhanced Unet++ network, and it realizes the intelligent identification of pump ball, pre-acid treatment, temporary plugging fracturing, sand plugging, and other events, with an error of less than 0.002. Moreover, a real-time prediction model for fracturing pressure is built based on the Att-BiLSTM neural network, and it realizes the real-time warning of diverse events in fracturing. The proposed method can provide an intelligent, efficient and accurate identification of events in fracturing to support the decision-making.展开更多
Various mechanisms are employed to interpret the low water recovery during the shale-gas production period,such as extra-trapped water in the fracture network,water imbibition due to osmotic pressure and capillary pre...Various mechanisms are employed to interpret the low water recovery during the shale-gas production period,such as extra-trapped water in the fracture network,water imbibition due to osmotic pressure and capillary pressure.These lead to the difficulty of water flow,which could be described by lowvelocity non-Darcy's law known as threshold pressure gradient(TPG).In this paper we firstly employ the low-velocity non-Darcy's law to describe the water flow and use Darcy flow accounting for slip flow and free molecular flow mechanisms to model gas flow in the shale formation.The sensitive study using numerical simulation shows that the proposed flow model could model the low fracturing liquid recovery and that large pseudo TPG leads to lower fracturing liquid recovery.Thus,the proposed model would give new insight to model the low water recovery in shale formations.展开更多
By systematically summarizing horizontal well fracturing technology abroad for shale oil and gas reservoirs since the “13th Five-Year Plan”, this article elaborates new horizontal well fracturing features in 3D deve...By systematically summarizing horizontal well fracturing technology abroad for shale oil and gas reservoirs since the “13th Five-Year Plan”, this article elaborates new horizontal well fracturing features in 3D development of stacked shale reservoirs, small well spacing and dense well pattern, horizontal well re-fracturing, fracturing parameters optimization and cost control. In light of requirements on horizontal well fracturing technology in China, we have summarized the technological progress in simulation of multi-fracture propagation, horizontal well frac-design, electric-drive fracturing equipment, soluble tools and low-cost downhole materials and factory-like operation. On this basis, combined with the demand analysis of horizontal well fracturing technology in the “14th Five-Year Plan” for unconventional shale oil and gas, we suggest strengthening the research and development in the following 7 aspects:(1) geology-engineering integration;(2) basic theory and design optimization of fracturing for shale oil and gas reservoirs;(3) development of high-power electric-drive fracturing equipment;(4) fracturing tool and supporting equipment for long horizontal section;(5) horizontal well flexible-sidetracking drilling technology for tapping remaining oil;(6) post-frac workover technology for long horizontal well;(7) intelligent fracturing technology.展开更多
This case study reports the successful outcome of horizontal root fractures of two different patients, which took place in permanent incisors. Report 1 describes a case of a 29-year-old patient who suffered a mandibul...This case study reports the successful outcome of horizontal root fractures of two different patients, which took place in permanent incisors. Report 1 describes a case of a 29-year-old patient who suffered a mandibular trauma affecting mainly the lower central incisors, caused by a car accident. A panoramic radiograph was taken right after the accident and showed a horizontal root fracture in the middle third of tooth 42, which went untreated. Report 2 illustrates a case of a 17-year-old male patient who searched for orthodontic therapy and the periapical radiograph showed horizontal root fracture in tooth 11 caused by a previous trauma, which went untreated as well. There was healing through the reestablishment of pulp activity and dental coloration without professional intervention.展开更多
This paper presents the development and application of a production data analysis software that can analyze and forecast the production performance and reservoir properties of shale gas wells.The theories used in the ...This paper presents the development and application of a production data analysis software that can analyze and forecast the production performance and reservoir properties of shale gas wells.The theories used in the study were based on the analytical and empirical approaches.Its reliability has been confirmed through comparisons with a commercial software.Using transient data relating to multi-stage hydraulic fractured horizontal wells,it was confirmed that the accuracy of the modified hyperbolic method showed an error of approximately 4%compared to the actual estimated ultimate recovery(EUR).On the basis of the developed model,reliable productivity forecasts have been obtained by analyzing field production data relating to wells in Canada.The EUR was computed as 9.6 Bcf using the modified hyperbolic method.Employing the Pow Law Exponential method,the EUR would be 9.4 Bcf.The models developed in this study will allow in the future integration of new analytical and empirical theories in a relatively readily than commercial models.展开更多
Often oilfield fractured horizontal wells produce water flowing in multiple directions.In this study,a method to identify such channeling paths is developed.The dual-medium model is based on the principle of inter-wel...Often oilfield fractured horizontal wells produce water flowing in multiple directions.In this study,a method to identify such channeling paths is developed.The dual-medium model is based on the principle of inter-well connectivity and considers the flow characteristics and related channeling terms.The Lorentz curve is drawn to qualitatively discern the geological type of the low-permeability fractured reservoir and determine the channeling direction and size.The practical application of such an approach to a sample oilfield shows that it can accurately identify the channeling paths of the considered low-permeability fractured reservoir and predict production performances according to the inter-well connectivity model.As a result,early detection of water channeling becomes possible,paving the way to real-time production system optimization in low-permeability fractured reservoirs.展开更多
A mathematical model for the gas-water two-phase flow in tight gas reservoirs is elaborated.The model can account for the gas slip effect,stress sensitivity,and high-speed non-Darcy factors.The related equations are s...A mathematical model for the gas-water two-phase flow in tight gas reservoirs is elaborated.The model can account for the gas slip effect,stress sensitivity,and high-speed non-Darcy factors.The related equations are solved in the framework of a finite element method.The results are validated against those obtained by using the commercial software CMG(Computer Modeling Group software for advanced recovery process simulation).It is shown that the proposed method is reliable.It can capture the fracture rejection characteristics of tight gas reservoirs better than the CMG.A sensitivity analysis of various control factors(initial water saturation,reservoir parameters,and fracturing parameters)affecting the production in tight gas wells is conducted accordingly.Finally,a series of theoretical arguments are provided for a rational and effective development/exploitation of tight sandstone gas reservoirs.展开更多
The application of distributed temperature sensors(DTS)to monitor producing zones of horizontal well through a real-time measurement of a temperature profile is becoming increasingly popular.Those parameters,such as f...The application of distributed temperature sensors(DTS)to monitor producing zones of horizontal well through a real-time measurement of a temperature profile is becoming increasingly popular.Those parameters,such as flow rate along wellbore,well completion method,skin factor,are potentially related to the information from DTS.Based on mass-,momentum-,and energy-balance equations,this paper established a coupled model to study on temperature distribution along wellbore of fracturing horizontal wells by considering skin factor in order to predict wellbore temperature distribution and analyze the factors influencing the wellbore temperature profile.The models presented in this paper account for heat convective,fluid expansion,heat conduction,and viscous dissipative heating.Arriving temperature and wellbore temperature curves are plotted by computer iterative calculation.The non-perforated and perforated sections show different temperature distribution along wellbore.Through the study on the sensitivity analysis of skin factor and flow rate,we come to the conclusion that the higher skin factor generates larger temperature increase near the wellbore,besides,temperature along wellbore is related to both skin factors and flow rate.Temperature response type curves show that the larger skin factor we set,the less temperature augmenter from toe to heel could be.In addition,larger flow rate may generate higher wellbore temperature.展开更多
Field evidence indicates that proppant distribution and threshold pressure gradient have great impacts on well productivity.Aiming at the development of unconventional oil reservoirs in Triassic Chang-7 Unit,Ordos Bas...Field evidence indicates that proppant distribution and threshold pressure gradient have great impacts on well productivity.Aiming at the development of unconventional oil reservoirs in Triassic Chang-7 Unit,Ordos Basin of China,we presented an integrated workflow to investigate how(1)proppant placement in induced fracture and(2)non-linear flow in reservoir matrix would affect well productivity and fluid flow in the reservoir.Compared with our research before(Yue et al.,2020),here we extended this study into the development of multi-stage fractured horizontal wells(MFHWs)with large-scale complicated fracture geometry.The integrated workflow is based on the finite element method and consists of simulation models for proppant-laden fluid flow,fracture flow,and non-linear seepage flow,respectively.Simulation results indicate that the distribution of proppant inside the induced cracks significantly affects the productivity of the MFHW.When we assign an idealized proppant distribution instead of the real distribution,there will be an overestimation of 44.98%in daily oil rate and 30.63%in cumulative oil production after continuous development of 1000 days.Besides,threshold pressure gradient(TPG)also significantly affects the well performance in tight oil reservoirs.If we simply apply linear Darcy’s law to the reservoir matrix,the overall cumulative oil production can be overrated by 77%after 1000 days of development.In general,this research provides new insights into the development of tight oil reservoirs with TPG and meanwhile reveals the significance of proppant distribution and non-linear fluid flow in the production scenario design.展开更多
文摘This study presents an avant-garde approach for predicting and optimizing production in tight reservoirs,employing a dual-medium unsteady seepage model specifically fashioned for volumetrically fractured horizontal wells.Traditional models often fail to fully capture the complex dynamics associated with these unconventional reservoirs.In a significant departure from these models,our approach incorporates an initiation pressure gradient and a discrete fracture seepage network,providing a more realistic representation of the seepage process.The model also integrates an enhanced fluid-solid interaction,which allows for a more comprehensive understanding of the fluid-structure interactions in the reservoir.This is achieved through the incorporation of improved permeability and stress coupling,leading to more precise predictions of reservoir behavior.The numerical solutions derived from the model are obtained through the sophisticated finite element method,ensuring high accuracy and computational efficiency.To ensure the model’s reliability and accuracy,the outcomes were tested against a real-world case,with results demonstrating strong alignment.A key revelation from the study is the significant difference between uncoupled and fully coupled volumetrically fractured horizontal wells,challenging conventional wisdom in the field.Additionally,the study delves into the effects of stress,fracture length,and fracture number on reservoir production,contributing valuable insights for the design and optimization of tight reservoirs.The findings from this study have the potential to revolutionize the field of tight reservoir prediction and management,offering significant advancements in petroleum engineering.The proposed approach brings forth a more nuanced understanding of tight reservoir systems and opens up new avenues for optimizing reservoir management and production.
基金Project(2013CB228005)supported by the National Basic Research Program of China
文摘Production decline analysis has been considered as an important method to obtain the flow parameters, reservoir properties and original gas in place. Although advanced Blasingame production decline analysis methods for vertical wells, fractured wells and horizontal wells are widely used, limited study has conducted on Blasingame production decline type curves for multi-fractured horizontal well(MFHW). Based on the perpendicular bisection(PEBI) grids, a numerical model was developed and the solution was obtained using control volume finite element method and the fully implicit method. Blasingame production decline-type curves of the infinitely conductive MFHW were plotted through computer programming. A field case was presented to analyse and verify the model developed. Five flow regimes, including early formation linear flow, early radial flow, compound linear flow, transient flow and pseudo-radial flow, are recognized. Fracture spacing is the main factor that affects early radial flow, compound linear flow and transient flow, the distance from the well to the circular boundary affects the pseudo-radial flow, and the type curves are also significantly affected by the formation permeability, fracture number and fracture half-length. The validation of field case suggests that the Blasingame production decline type curves proposed in this work can be applied to the production decline analysis for MFHW in tight gas reservoirs.
基金This work was supported by the National Natural Science Foundation of China(Grant No.52004237)Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(Grant No.2020CX020202)the Sichuan Science and Technology Program(No.2022JDJQ0009).
文摘The production performances of a well with a shale gas reservoir displaying a complex fracture network are simulated.In particular,a micro-seismic cloud diagram is used to describe the fracture network,and accordingly,a production model is introduced based on a multi-scale flow mechanism.A finite volume method is then exploited for the integration of the model equations.The effects of apparent permeability,conductivity,Langmuir volume,and bottom hole pressure on gas well production are studied accordingly.The simulation results show that ignoring the micro-scale flow mechanism of the shale gas leads to underestimating the well gas production.It is shown that after ten years of production,the cumulative gas production difference between the two scenarios with and without considering the micro-scale flow mechanisms is 19.5%.The greater the fracture conductivity,the higher the initial gas production of the gas well and the cumulative gas production.The larger the Langmuir volume,the higher the gas production rate and the cumulative gas production.With the reduction of the bottom hole pressure,the cumulative gas production increases,but the growth rate gradually decreases.
基金The authors would like to acknowledge the financial support provided by the China Joint Foundation for Petrochemical Industry(A)(No.U1562102).
文摘Currently,most models for multiple fractured horizontal wells(MFHWs)in naturally fractured unconventional reservoirs(NFURs)are based on classical Euclidean models which implicitly assume a uniform distribution of natural fractures and that all fractures are homogeneous.While fractal theory provides a powerful method to describe the disorder,heterogeneity,uncertainty and complexity of the NFURs.In this paper,a fractally fractional diffusion model(FFDM)for MFHWs in NFURs is established based on fractal theory and fractional calculus.Particularly,fractal theory is used to describe the heterogeneous,complex fracture network,with consideration of anomalous behavior of diffusion process in NFURs by employing fractional calculus.The Laplace transformation,line source function,dispersion method,and superposition principle are used to solve this new model.The pressure responses in the real time domain are obtained with Stehfest numerical inversion algorithms.The type curves of MFHW with three different outer boundaries are plotted.Sensitivity analysis of some related parameters are discussed as well.This new model provides the relatively more accurate and appropriate evaluation results for pressure transient analysis for MFHWs in NFURs,which could be applied to accurately interpret the real pressure data of an MFHW in field.
基金Supported by the National Key R&DPlan Project(2022YFE0129900)National Natural Science Foundation of China(52074338).
文摘The existing approaches for identifying events in horizontal well fracturing are difficult, time-consuming, inaccurate, and incapable of real-time warning. Through improvement of data analysis and deep learning algorithm, together with the analysis on data and information of horizontal well fracturing in shale gas reservoirs, this paper presents a method for intelligent identification and real-time warning of diverse complex events in horizontal well fracturing. An identification model for "point" events in fracturing is established based on the Att-BiLSTM neural network, along with the broad learning system (BLS) and the BP neural network, and it realizes the intelligent identification of the start/end of fracturing, formation breakdown, instantaneous shut-in, and other events, with an accuracy of over 97%. An identification model for "phase" events in fracturing is established based on enhanced Unet++ network, and it realizes the intelligent identification of pump ball, pre-acid treatment, temporary plugging fracturing, sand plugging, and other events, with an error of less than 0.002. Moreover, a real-time prediction model for fracturing pressure is built based on the Att-BiLSTM neural network, and it realizes the real-time warning of diverse events in fracturing. The proposed method can provide an intelligent, efficient and accurate identification of events in fracturing to support the decision-making.
基金supported by the National Natural Science Foundation of China(Grant No.1217020361).
文摘Various mechanisms are employed to interpret the low water recovery during the shale-gas production period,such as extra-trapped water in the fracture network,water imbibition due to osmotic pressure and capillary pressure.These lead to the difficulty of water flow,which could be described by lowvelocity non-Darcy's law known as threshold pressure gradient(TPG).In this paper we firstly employ the low-velocity non-Darcy's law to describe the water flow and use Darcy flow accounting for slip flow and free molecular flow mechanisms to model gas flow in the shale formation.The sensitive study using numerical simulation shows that the proposed flow model could model the low fracturing liquid recovery and that large pseudo TPG leads to lower fracturing liquid recovery.Thus,the proposed model would give new insight to model the low water recovery in shale formations.
基金Supported by the National Science and Technology Major Project(2016ZX05023)。
文摘By systematically summarizing horizontal well fracturing technology abroad for shale oil and gas reservoirs since the “13th Five-Year Plan”, this article elaborates new horizontal well fracturing features in 3D development of stacked shale reservoirs, small well spacing and dense well pattern, horizontal well re-fracturing, fracturing parameters optimization and cost control. In light of requirements on horizontal well fracturing technology in China, we have summarized the technological progress in simulation of multi-fracture propagation, horizontal well frac-design, electric-drive fracturing equipment, soluble tools and low-cost downhole materials and factory-like operation. On this basis, combined with the demand analysis of horizontal well fracturing technology in the “14th Five-Year Plan” for unconventional shale oil and gas, we suggest strengthening the research and development in the following 7 aspects:(1) geology-engineering integration;(2) basic theory and design optimization of fracturing for shale oil and gas reservoirs;(3) development of high-power electric-drive fracturing equipment;(4) fracturing tool and supporting equipment for long horizontal section;(5) horizontal well flexible-sidetracking drilling technology for tapping remaining oil;(6) post-frac workover technology for long horizontal well;(7) intelligent fracturing technology.
文摘This case study reports the successful outcome of horizontal root fractures of two different patients, which took place in permanent incisors. Report 1 describes a case of a 29-year-old patient who suffered a mandibular trauma affecting mainly the lower central incisors, caused by a car accident. A panoramic radiograph was taken right after the accident and showed a horizontal root fracture in the middle third of tooth 42, which went untreated. Report 2 illustrates a case of a 17-year-old male patient who searched for orthodontic therapy and the periapical radiograph showed horizontal root fracture in tooth 11 caused by a previous trauma, which went untreated as well. There was healing through the reestablishment of pulp activity and dental coloration without professional intervention.
基金supported by the Energy Efficiency&Resources Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning(KETEP)granted financial resource from the Ministry of Trade,Industry&Energy,Republic of Korea(No.20172510102090).
文摘This paper presents the development and application of a production data analysis software that can analyze and forecast the production performance and reservoir properties of shale gas wells.The theories used in the study were based on the analytical and empirical approaches.Its reliability has been confirmed through comparisons with a commercial software.Using transient data relating to multi-stage hydraulic fractured horizontal wells,it was confirmed that the accuracy of the modified hyperbolic method showed an error of approximately 4%compared to the actual estimated ultimate recovery(EUR).On the basis of the developed model,reliable productivity forecasts have been obtained by analyzing field production data relating to wells in Canada.The EUR was computed as 9.6 Bcf using the modified hyperbolic method.Employing the Pow Law Exponential method,the EUR would be 9.4 Bcf.The models developed in this study will allow in the future integration of new analytical and empirical theories in a relatively readily than commercial models.
文摘Often oilfield fractured horizontal wells produce water flowing in multiple directions.In this study,a method to identify such channeling paths is developed.The dual-medium model is based on the principle of inter-well connectivity and considers the flow characteristics and related channeling terms.The Lorentz curve is drawn to qualitatively discern the geological type of the low-permeability fractured reservoir and determine the channeling direction and size.The practical application of such an approach to a sample oilfield shows that it can accurately identify the channeling paths of the considered low-permeability fractured reservoir and predict production performances according to the inter-well connectivity model.As a result,early detection of water channeling becomes possible,paving the way to real-time production system optimization in low-permeability fractured reservoirs.
基金supported by the China Postdoctoral Science Foundation(2021M702304)and Natural Science Foundation of Shandong Province(ZR2021QE260).
文摘A mathematical model for the gas-water two-phase flow in tight gas reservoirs is elaborated.The model can account for the gas slip effect,stress sensitivity,and high-speed non-Darcy factors.The related equations are solved in the framework of a finite element method.The results are validated against those obtained by using the commercial software CMG(Computer Modeling Group software for advanced recovery process simulation).It is shown that the proposed method is reliable.It can capture the fracture rejection characteristics of tight gas reservoirs better than the CMG.A sensitivity analysis of various control factors(initial water saturation,reservoir parameters,and fracturing parameters)affecting the production in tight gas wells is conducted accordingly.Finally,a series of theoretical arguments are provided for a rational and effective development/exploitation of tight sandstone gas reservoirs.
文摘The application of distributed temperature sensors(DTS)to monitor producing zones of horizontal well through a real-time measurement of a temperature profile is becoming increasingly popular.Those parameters,such as flow rate along wellbore,well completion method,skin factor,are potentially related to the information from DTS.Based on mass-,momentum-,and energy-balance equations,this paper established a coupled model to study on temperature distribution along wellbore of fracturing horizontal wells by considering skin factor in order to predict wellbore temperature distribution and analyze the factors influencing the wellbore temperature profile.The models presented in this paper account for heat convective,fluid expansion,heat conduction,and viscous dissipative heating.Arriving temperature and wellbore temperature curves are plotted by computer iterative calculation.The non-perforated and perforated sections show different temperature distribution along wellbore.Through the study on the sensitivity analysis of skin factor and flow rate,we come to the conclusion that the higher skin factor generates larger temperature increase near the wellbore,besides,temperature along wellbore is related to both skin factors and flow rate.Temperature response type curves show that the larger skin factor we set,the less temperature augmenter from toe to heel could be.In addition,larger flow rate may generate higher wellbore temperature.
基金The authors gratefully acknowledge the financial supports from the National Science Foundation of China under Grant 52274027 as well as the High-end Foreign Experts Recruitment Plan of the Ministry of Science and Technology China under Grant G2022105027L.
文摘Field evidence indicates that proppant distribution and threshold pressure gradient have great impacts on well productivity.Aiming at the development of unconventional oil reservoirs in Triassic Chang-7 Unit,Ordos Basin of China,we presented an integrated workflow to investigate how(1)proppant placement in induced fracture and(2)non-linear flow in reservoir matrix would affect well productivity and fluid flow in the reservoir.Compared with our research before(Yue et al.,2020),here we extended this study into the development of multi-stage fractured horizontal wells(MFHWs)with large-scale complicated fracture geometry.The integrated workflow is based on the finite element method and consists of simulation models for proppant-laden fluid flow,fracture flow,and non-linear seepage flow,respectively.Simulation results indicate that the distribution of proppant inside the induced cracks significantly affects the productivity of the MFHW.When we assign an idealized proppant distribution instead of the real distribution,there will be an overestimation of 44.98%in daily oil rate and 30.63%in cumulative oil production after continuous development of 1000 days.Besides,threshold pressure gradient(TPG)also significantly affects the well performance in tight oil reservoirs.If we simply apply linear Darcy’s law to the reservoir matrix,the overall cumulative oil production can be overrated by 77%after 1000 days of development.In general,this research provides new insights into the development of tight oil reservoirs with TPG and meanwhile reveals the significance of proppant distribution and non-linear fluid flow in the production scenario design.