To improve the rate of penetration(ROP) in drilling deep and hard formations, this paper proposes a new drilling method called coiled tubing partial underbalanced drilling(CT-PUBD). As a preliminary investigation into...To improve the rate of penetration(ROP) in drilling deep and hard formations, this paper proposes a new drilling method called coiled tubing partial underbalanced drilling(CT-PUBD). As a preliminary investigation into the new drilling method, this paper presents predictions of hole cleaning efficiency, drilling speed, cuttings migration and pressure loss in the drilling process with CT-PUBD. Based on numerical simulation and full-scale experimental studies, we conclude that using CT-PUBD, an underbalanced drilling condition can be achieved near the bit while maintaining wellbore safety at the same time. This condition can be achieved using a cuttings discharge device, a rotary packer and a backflow controller.According to the numerical simulations performed in this study, CT-PUBD can achieve high efficiency of hole cleaning.Along the cuttings migration process, the fluid velocities can reach the maximum values in the backflow holes. A full-scale laboratory experimental system was used to test the hydraulic characteristics and obtain the drilling performance of the new technology. The result shows that CT-PUBD significantly improves the ROP compared to the conventional drilling method.展开更多
Underbalanced drilling(UBD) is defined as a drilling operation in which circulating drilling fluid pressure is maintained to be lower than reservoir pore pressure.Underbalanced drilling may improve drilling efficiency...Underbalanced drilling(UBD) is defined as a drilling operation in which circulating drilling fluid pressure is maintained to be lower than reservoir pore pressure.Underbalanced drilling may improve drilling efficiency and enhance well productivity. Approximately 90%of the discovered fields in Iran are in carbonate reservoirs putting Iran as one of the largest carbonate producers in the world.Under-展开更多
For decades,some geological formations have been drilled with a drilling fluid that exerted a bottom-hole pressure less than the formation pressure,allowing formation fluids-oil,gas and water-to flow from the reservoi...For decades,some geological formations have been drilled with a drilling fluid that exerted a bottom-hole pressure less than the formation pressure,allowing formation fluids-oil,gas and water-to flow from the reservoir into the well bore while drilling proceeds.A growing number of Iranian case histories have shown that when UBD is applied in the right reservoir with the proper planning,well productivity can be orders of magnitude greater than with a conventional well drilled into the same formation.Wells drilled underbalanced have been proven to add展开更多
Foam is used widely in underbalanced drilling for oil and gas exploration to improve well perfor-mance.Accurate prediction of the cutting transport and pressure loss in the foam drilling is an important way to prevent...Foam is used widely in underbalanced drilling for oil and gas exploration to improve well perfor-mance.Accurate prediction of the cutting transport and pressure loss in the foam drilling is an important way to prevent stuck pipe,lost circulation and to increase the rate of penetration(ROP).In foam drilling,the cuttings transport quality may be defined in terms of cuttings consistency and downhole pressure loss,which are controlled by many factors.Therefore,it is very difficult to establish the mathematical equation that reflects nonlinear relationship among various factors.The field and experimental measurements of these parameters are time consuming and costly.In this study,the authors suggest a cuttings transport mathematical modeling using BPN(back propagation network),RBFN(radial basis function network)and GRNN(general regression neural network)based on various experiment data of cuttings transport of previous researchers and compared the result with experiment data.Results of this study show that the GRNN has a correlation coefficient of 0.99962 and an average error of 0.15 in training datasets,and a correlation coefficient of 0.99881 and an average error of 0.612 in testing datasets,which has higher accuracy and faster training velocity than the BP network or RBFN network.GRNN can be used in many mathematical problems for accurate estimation of cuttings consistency and downhole pressure loss instead of field and experimental measurements for hydraulic design in foam drilling operation.展开更多
The damages of different drilling modes to reservoirs are different in types and degrees.In this paper,the geologic characteristics and types of such damages were analyzed.Then,based on the relationship between reserv...The damages of different drilling modes to reservoirs are different in types and degrees.In this paper,the geologic characteristics and types of such damages were analyzed.Then,based on the relationship between reservoir pressure and bottom hole flowing pressure corresponding to different drilling modes,the experimental procedures on reservoir damages in three drilling modes(e.g.gas drilling,liquid-based underbalanced drilling and overbalanced drilling)were designed.Finally,damage simulation experiments were conducted on the tight sandstone reservoir cores of the Jurassic Ahe Fm in the Tarim Basin and Triassic Xujiahe Fm in the central Sichuan Basin.It is shown that the underbalanced drilling is beneficial to reservoir protection because of its less damage on reservoir permeability,but it is,to some extent,sensitive to the stress and the empirical formula of stress sensitivity coefficient is obtained;and that the overbalanced drilling has more reservoir damages due to the invasion of solid and liquid phases.After the water saturation of cores rises to the irreducible water saturation,the decline of gas logging permeability speeds up and the damage degree of water lock increases.It is concluded that the laboratory experiment results of reservoir damage are accordant with the reservoir damage characteristics in actual drilling conditions.Therefore,this method reflects accurately the reservoir damage characteristics and can be used as a new experimental evaluation method on reservoir damage in different drilling modes.展开更多
基金the National Natural Science Foundation of China (Grant No. 51474232)the National Science and Technology Major Project (Grant No. 2016ZX05022)
文摘To improve the rate of penetration(ROP) in drilling deep and hard formations, this paper proposes a new drilling method called coiled tubing partial underbalanced drilling(CT-PUBD). As a preliminary investigation into the new drilling method, this paper presents predictions of hole cleaning efficiency, drilling speed, cuttings migration and pressure loss in the drilling process with CT-PUBD. Based on numerical simulation and full-scale experimental studies, we conclude that using CT-PUBD, an underbalanced drilling condition can be achieved near the bit while maintaining wellbore safety at the same time. This condition can be achieved using a cuttings discharge device, a rotary packer and a backflow controller.According to the numerical simulations performed in this study, CT-PUBD can achieve high efficiency of hole cleaning.Along the cuttings migration process, the fluid velocities can reach the maximum values in the backflow holes. A full-scale laboratory experimental system was used to test the hydraulic characteristics and obtain the drilling performance of the new technology. The result shows that CT-PUBD significantly improves the ROP compared to the conventional drilling method.
文摘Underbalanced drilling(UBD) is defined as a drilling operation in which circulating drilling fluid pressure is maintained to be lower than reservoir pore pressure.Underbalanced drilling may improve drilling efficiency and enhance well productivity. Approximately 90%of the discovered fields in Iran are in carbonate reservoirs putting Iran as one of the largest carbonate producers in the world.Under-
文摘For decades,some geological formations have been drilled with a drilling fluid that exerted a bottom-hole pressure less than the formation pressure,allowing formation fluids-oil,gas and water-to flow from the reservoir into the well bore while drilling proceeds.A growing number of Iranian case histories have shown that when UBD is applied in the right reservoir with the proper planning,well productivity can be orders of magnitude greater than with a conventional well drilled into the same formation.Wells drilled underbalanced have been proven to add
文摘Foam is used widely in underbalanced drilling for oil and gas exploration to improve well perfor-mance.Accurate prediction of the cutting transport and pressure loss in the foam drilling is an important way to prevent stuck pipe,lost circulation and to increase the rate of penetration(ROP).In foam drilling,the cuttings transport quality may be defined in terms of cuttings consistency and downhole pressure loss,which are controlled by many factors.Therefore,it is very difficult to establish the mathematical equation that reflects nonlinear relationship among various factors.The field and experimental measurements of these parameters are time consuming and costly.In this study,the authors suggest a cuttings transport mathematical modeling using BPN(back propagation network),RBFN(radial basis function network)and GRNN(general regression neural network)based on various experiment data of cuttings transport of previous researchers and compared the result with experiment data.Results of this study show that the GRNN has a correlation coefficient of 0.99962 and an average error of 0.15 in training datasets,and a correlation coefficient of 0.99881 and an average error of 0.612 in testing datasets,which has higher accuracy and faster training velocity than the BP network or RBFN network.GRNN can be used in many mathematical problems for accurate estimation of cuttings consistency and downhole pressure loss instead of field and experimental measurements for hydraulic design in foam drilling operation.
基金Project supported by the Scientific Research and Innovation Team Fund of Universities Affiliated to Sichuan Province(No.2014TD0006)“Research on downhole safety risk and control methods of gas drilling”in Sichuan outstanding young academic technology leader training plan(No.2014JQ0045)Device and software development for quantitative evaluation of low-permeability gas reservoir damages(No.2016ZX05021-004-005).
文摘The damages of different drilling modes to reservoirs are different in types and degrees.In this paper,the geologic characteristics and types of such damages were analyzed.Then,based on the relationship between reservoir pressure and bottom hole flowing pressure corresponding to different drilling modes,the experimental procedures on reservoir damages in three drilling modes(e.g.gas drilling,liquid-based underbalanced drilling and overbalanced drilling)were designed.Finally,damage simulation experiments were conducted on the tight sandstone reservoir cores of the Jurassic Ahe Fm in the Tarim Basin and Triassic Xujiahe Fm in the central Sichuan Basin.It is shown that the underbalanced drilling is beneficial to reservoir protection because of its less damage on reservoir permeability,but it is,to some extent,sensitive to the stress and the empirical formula of stress sensitivity coefficient is obtained;and that the overbalanced drilling has more reservoir damages due to the invasion of solid and liquid phases.After the water saturation of cores rises to the irreducible water saturation,the decline of gas logging permeability speeds up and the damage degree of water lock increases.It is concluded that the laboratory experiment results of reservoir damage are accordant with the reservoir damage characteristics in actual drilling conditions.Therefore,this method reflects accurately the reservoir damage characteristics and can be used as a new experimental evaluation method on reservoir damage in different drilling modes.
