Existing evaluation methods used for the development area selection for commingled production of tight gas and coalbed methane(CBM)are poorly universal and their parameters(e.g.reserves and reservoir physical properti...Existing evaluation methods used for the development area selection for commingled production of tight gas and coalbed methane(CBM)are poorly universal and their parameters(e.g.reserves and reservoir physical properties)cannot reflect the production rate difference during commingled production of tight gas and CBM.In this paper,an integrated evaluation coefficient used for evaluating favorable commingled production areas of tight gas and CBM was defined so as to establish a universal quantitative evaluation index system.Then,by means of orthogonal design together with numerical simulation,the key parameters influencing the commingled production rate and their influence degree on the production rate were determined by taking the commingled production rate as the evaluation target.Finally,a new quantitative evaluation method for the development area selection for commingled production of tight gas and CBM was established.And the following research results were obtained.First,by virtue of the new quantitative evaluation method,the geological occurrence model of tight gas and CBM,the key evaluation parameter and the orthogonal experiment design are established,and the influence degree of evaluation parameters on production rate and the integrated evaluation coefficient of favorable commingled production area of tight gas and CBM are determined.Second,the quantitative evaluation results on the development areas of commingled production of tight gas and CBM in KNW Block based on 12 selected key parameters show that the southern KNW Block and the Well block KNW-37 in the north of KNW Block are the favorable areas for single production of tight gas,Well blocks KNW-10,KNW-33 and KNW-9 are the favorable areas for single production of CBM,and the central and southwestern areas are the favorable areas for the commingled production of tight gas and CBM.In conclusion,this new quantitative evaluation method is universal and can be used as reference for the development area selection for commingled production of tight gas and CBM.展开更多
Gas drainage is carried out based on output from each coal bed throughout commingling production of coalbed methane(CBM).A reasonable drainage process should therefore initially guarantee main coal bed production and ...Gas drainage is carried out based on output from each coal bed throughout commingling production of coalbed methane(CBM).A reasonable drainage process should therefore initially guarantee main coal bed production and then enhance gas output from other beds.Permanent damage can result if this is not the case,especially with regard to fracture development in the main gas-producing coal bed and can greatly reduce single well output.Current theoretical models and measuring devices are inapplicable to commingled CBM drainage,however,and so large errors in predictive models cannot always be avoided.The most effective currently available method involves directly measuring gas output from each coal bed as well as determining the dominant gas-producing unit.A dynamic evaluation technique for gas output from each coal bed during commingling CBM production is therefore proposed in this study.This technique comprises a downhole measurement system combined with a theoretical calculation model.Gas output parameters(i.e.,gas-phase flow rate,temperature,pressure)are measured in this approach via a downhole measurement system;substituting these parameters into a deduced theoretical calculation model then means that gas output from each seam can be calculated to determine the main gas-producing unit.Trends in gas output from a single well or each seam can therefore be predicted.The laboratory and field test results presented here demonstrate that calculation errors in CBM outputs can be controlled within a margin of 15%and therefore conform with field use requirements.展开更多
Hydraulic fracturing and commingle production of multiple layers are extensively adopted in unconventional tight gas reservoirs.Accurate determination of parameters of individual layers in multilayered tight gas reser...Hydraulic fracturing and commingle production of multiple layers are extensively adopted in unconventional tight gas reservoirs.Accurate determination of parameters of individual layers in multilayered tight gas reservoirs is essential for well performance evaluation and development strategy optimization.However,most analytical models for fractured vertical wells in stratified gas reservoirs focus on fully penetrated hydraulic fractures,neglecting the influence of partial penetration of hydraulic fractures.This paper presents a semi-analytical model to investigate the transient pressure behavior of vertically fractured wells in dual porosity multi-layered tight gas reservoirs.The partial penetration of hydraulic fracture,the vertical heterogeneities of layer properties,the differences between hydraulic fracture lengths in each layer and the stress sensitivity are all incorporated in the proposed model.The point-source solution,Laplace transformation,Fourier transformation,Pedrosa's transformation,perturbation technique,and the superposition principle are applied to obtain the analytical solution of transient pressure responses.The proposed model is validated against a commercial software,and the transient pressure behavior of vertically fractured wells in multi-layered tight gas reservoirs are analyzed.Based on the characteristics of the type curves,seven flow regimes can be identified,including wellbore storage,transitional flow period,reservoir linear flow period,vertical pseudo-radial flow in fracture system,inter-porosity flow period,late-time pseudo-radial flow period,and the boundary-dominated flow period.Sensitivity analyses reveal that the penetration ratio of hydraulic fracture has primary influence on early-time transient pressure behavior and production contribution,while the stress sensitivity mainly affects the late-time transient pressure behavior.Gas production at the initial stage is mainly contributed by the high-pressure/high-permeability layer,and gas backflow will occur during initial production stage for obviously unequal initial formation pressures.Finally,two field cases are conducted to illustrate the applicability of the proposed model.The model and corresponding conclusions can provide technical support for performance analysis of tight gas reservoirs.展开更多
The existing models for calculating the water breakthrough time of gas wells in gas reservoirs with edge water ignore the effects of reservoir's interlayer heterogeneity,so their calculation results are more devia...The existing models for calculating the water breakthrough time of gas wells in gas reservoirs with edge water ignore the effects of reservoir's interlayer heterogeneity,so their calculation results are more deviated from the actual water breakthrough time of gas wells.As a result,they cannot accurately and effectively guide the adjustment of gas well production system and the formulation of technical water control measures.In this paper,a water-flooding seepage experiment of parallel core was conducted by taking the gas reservoir with edge water of Lower Triassic Feixianguan Formation in the Puguang Gas Field of the Sichuan Basin as an example.Then,the effects of edge water inrush caused by the interlayer heterogeneity of reservoir on water breakthrough time of gas wells was analyzed by means of reservoir numerical simulation.Based on this,the inrush coefficient was introduced to characterize the interlayer heterogeneity of reservoir,and a model for calculating the water breakthrough time of gas wells in the commingled gas reservoir with edge water considering the influence of interlayer heterogeneity was established.Finally,five wells in the gas reservoir of Feixianguan Formation in the Puguang Gas Field were selected for case calculation.And the following research results were obtained.First,the interlayer heterogeneity of gas reservoir results in edge water burst.And the stronger the interlayer heterogeneity,the more severe the edge water coning and the sooner the water breakthrough.The water breakthrough time of gas wells depends on the water breakthrough time in the reservoir with the highest permeability.Second,a model for calculating the water breakthrough time of gas wells in the gas reservoirs with edge water considering the influence of reservoir interlayer heterogeneity is established based on the seepage theory.And the relative errors of its calculation results are in the range of 3.43e4.70%,which can satisfy the accuracy requirement of engineering errors.In conclusion,this newly established model can provide an effective method for accurately calculating the water break-through time of the gas well in the commingled gas reservoir with edge water.Furthermore,it is conducive to the adjustment of the production system of gas wells in the gas reservoir with edge water and the formulation of technical water control measures.展开更多
基金supported by the Comprehensive Research Project of CNOOC Research Institute“Overseas Shale Oil and Gas Productivity Evaluation Technology and Method”(No.:YXKY-2016-ZY-03).
文摘Existing evaluation methods used for the development area selection for commingled production of tight gas and coalbed methane(CBM)are poorly universal and their parameters(e.g.reserves and reservoir physical properties)cannot reflect the production rate difference during commingled production of tight gas and CBM.In this paper,an integrated evaluation coefficient used for evaluating favorable commingled production areas of tight gas and CBM was defined so as to establish a universal quantitative evaluation index system.Then,by means of orthogonal design together with numerical simulation,the key parameters influencing the commingled production rate and their influence degree on the production rate were determined by taking the commingled production rate as the evaluation target.Finally,a new quantitative evaluation method for the development area selection for commingled production of tight gas and CBM was established.And the following research results were obtained.First,by virtue of the new quantitative evaluation method,the geological occurrence model of tight gas and CBM,the key evaluation parameter and the orthogonal experiment design are established,and the influence degree of evaluation parameters on production rate and the integrated evaluation coefficient of favorable commingled production area of tight gas and CBM are determined.Second,the quantitative evaluation results on the development areas of commingled production of tight gas and CBM in KNW Block based on 12 selected key parameters show that the southern KNW Block and the Well block KNW-37 in the north of KNW Block are the favorable areas for single production of tight gas,Well blocks KNW-10,KNW-33 and KNW-9 are the favorable areas for single production of CBM,and the central and southwestern areas are the favorable areas for the commingled production of tight gas and CBM.In conclusion,this new quantitative evaluation method is universal and can be used as reference for the development area selection for commingled production of tight gas and CBM.
基金This research was funded by grants from the Natural Science Foundation in Hubei(2018CFB349)the National Natural Sciences Foundation of China(41672155,61733016)Open Research Fund Program of Key Laboratory of Tectonics and Petroleum Resources Ministry of Education(No.TPR-2018-10).
文摘Gas drainage is carried out based on output from each coal bed throughout commingling production of coalbed methane(CBM).A reasonable drainage process should therefore initially guarantee main coal bed production and then enhance gas output from other beds.Permanent damage can result if this is not the case,especially with regard to fracture development in the main gas-producing coal bed and can greatly reduce single well output.Current theoretical models and measuring devices are inapplicable to commingled CBM drainage,however,and so large errors in predictive models cannot always be avoided.The most effective currently available method involves directly measuring gas output from each coal bed as well as determining the dominant gas-producing unit.A dynamic evaluation technique for gas output from each coal bed during commingling CBM production is therefore proposed in this study.This technique comprises a downhole measurement system combined with a theoretical calculation model.Gas output parameters(i.e.,gas-phase flow rate,temperature,pressure)are measured in this approach via a downhole measurement system;substituting these parameters into a deduced theoretical calculation model then means that gas output from each seam can be calculated to determine the main gas-producing unit.Trends in gas output from a single well or each seam can therefore be predicted.The laboratory and field test results presented here demonstrate that calculation errors in CBM outputs can be controlled within a margin of 15%and therefore conform with field use requirements.
基金supported by the National Natural Science Foundation of China(Grant Nos.52174036,52234003)the Sichuan Province Science and Technology Program(Grant No.2024NSFSC0199)the Joint Fund for Innovation and Development of Chongqing Natural Science Foundation(Grant No.2023NSCQ-LZX0184).
文摘Hydraulic fracturing and commingle production of multiple layers are extensively adopted in unconventional tight gas reservoirs.Accurate determination of parameters of individual layers in multilayered tight gas reservoirs is essential for well performance evaluation and development strategy optimization.However,most analytical models for fractured vertical wells in stratified gas reservoirs focus on fully penetrated hydraulic fractures,neglecting the influence of partial penetration of hydraulic fractures.This paper presents a semi-analytical model to investigate the transient pressure behavior of vertically fractured wells in dual porosity multi-layered tight gas reservoirs.The partial penetration of hydraulic fracture,the vertical heterogeneities of layer properties,the differences between hydraulic fracture lengths in each layer and the stress sensitivity are all incorporated in the proposed model.The point-source solution,Laplace transformation,Fourier transformation,Pedrosa's transformation,perturbation technique,and the superposition principle are applied to obtain the analytical solution of transient pressure responses.The proposed model is validated against a commercial software,and the transient pressure behavior of vertically fractured wells in multi-layered tight gas reservoirs are analyzed.Based on the characteristics of the type curves,seven flow regimes can be identified,including wellbore storage,transitional flow period,reservoir linear flow period,vertical pseudo-radial flow in fracture system,inter-porosity flow period,late-time pseudo-radial flow period,and the boundary-dominated flow period.Sensitivity analyses reveal that the penetration ratio of hydraulic fracture has primary influence on early-time transient pressure behavior and production contribution,while the stress sensitivity mainly affects the late-time transient pressure behavior.Gas production at the initial stage is mainly contributed by the high-pressure/high-permeability layer,and gas backflow will occur during initial production stage for obviously unequal initial formation pressures.Finally,two field cases are conducted to illustrate the applicability of the proposed model.The model and corresponding conclusions can provide technical support for performance analysis of tight gas reservoirs.
基金Project supported by the National Science and Technology Major Project“Research on Gas-Water Two-Phase Flow Characteristics of Deep Reef-Shoal Reservoirs”(No.2016ZX05017-001-HZ02)Chongqing Graduate Research and Innovation Project“Water Invasion Mechanism and Prediction Model of Water Breakthrough Time of Ultra-Deep Carbonate Gas Reservoirs”(No.CYS19351)。
文摘The existing models for calculating the water breakthrough time of gas wells in gas reservoirs with edge water ignore the effects of reservoir's interlayer heterogeneity,so their calculation results are more deviated from the actual water breakthrough time of gas wells.As a result,they cannot accurately and effectively guide the adjustment of gas well production system and the formulation of technical water control measures.In this paper,a water-flooding seepage experiment of parallel core was conducted by taking the gas reservoir with edge water of Lower Triassic Feixianguan Formation in the Puguang Gas Field of the Sichuan Basin as an example.Then,the effects of edge water inrush caused by the interlayer heterogeneity of reservoir on water breakthrough time of gas wells was analyzed by means of reservoir numerical simulation.Based on this,the inrush coefficient was introduced to characterize the interlayer heterogeneity of reservoir,and a model for calculating the water breakthrough time of gas wells in the commingled gas reservoir with edge water considering the influence of interlayer heterogeneity was established.Finally,five wells in the gas reservoir of Feixianguan Formation in the Puguang Gas Field were selected for case calculation.And the following research results were obtained.First,the interlayer heterogeneity of gas reservoir results in edge water burst.And the stronger the interlayer heterogeneity,the more severe the edge water coning and the sooner the water breakthrough.The water breakthrough time of gas wells depends on the water breakthrough time in the reservoir with the highest permeability.Second,a model for calculating the water breakthrough time of gas wells in the gas reservoirs with edge water considering the influence of reservoir interlayer heterogeneity is established based on the seepage theory.And the relative errors of its calculation results are in the range of 3.43e4.70%,which can satisfy the accuracy requirement of engineering errors.In conclusion,this newly established model can provide an effective method for accurately calculating the water break-through time of the gas well in the commingled gas reservoir with edge water.Furthermore,it is conducive to the adjustment of the production system of gas wells in the gas reservoir with edge water and the formulation of technical water control measures.
