Our database tracking of USA water usage per well indicates that traditionally shale operators have been using, on average 3 to 6 million gallons of water; even up to 8 million for the en- tire life cycle of the well ...Our database tracking of USA water usage per well indicates that traditionally shale operators have been using, on average 3 to 6 million gallons of water; even up to 8 million for the en- tire life cycle of the well based on its suitability for re-fracturing to stimulate their long and lateral ho- rizontal welis. According to our data, sourcing, storage, transportation, treatment, and disposal of this large volume of water could account for up to 10% of overall drilling and completion costs. With in- creasingly stringent regulations governing the use of fresh water and growing challenges associated with storage and use of produced and flowback water in hydraulic fracturing, finding alternative sources of fracturing fluid is already a hot debate among both the scientific community and industry experts. On the other hand, waterless fracturing technology providers claim their technology can solve the concerns of water availability for shale development. This study reviews high-level technical issues and opportunities in this challenging and growing market and evaluates key economic drivers behind water management practices such as waterless fracturing technologies, based on a given shale gas play in the United States and experience gained in Canada. Water costs are analyzed under a variety of scenarios with and without the use of （fresh） water. The results are complemented by surveys from several oil and gas operators. Our economic analysis shows that fresh water usage offers the greatest economic return. In regions where water sourcing is a challenge, however, the short-term economic advantage of using non-fresh water-based fracturing outweighs the capital costs required by waterless fracturing methods. Until waterless methods are cost competitive, recycled water usage with low treatment offers a similar net present value （NPV） to that of sourcing freshwater via truck, for in- stance.展开更多
With the increasing demand for energy,traditional oil resources are facing depletion and insufficient supply.Many countries are rapidly turning to the development of unconventional oil and gas resources.Among them,sha...With the increasing demand for energy,traditional oil resources are facing depletion and insufficient supply.Many countries are rapidly turning to the development of unconventional oil and gas resources.Among them,shale oil and gas reservoirs have become the focus of unconventional oil and gas resources exploration and development.Based on the characteristics of shale oil and gas reservoirs,supercritical CO_(2) fracturing is more conducive to improving oil recovery than other fracturing technologies.In this paper,the mechanism of fracture initiation and propagation of supercritical CO_(2) in shale is analyzed,including viscosity effect,surface tension effect,permeation diffusion effect of supercritical CO_(2),and dissolution-adsorption effect between CO_(2) and shale.The effects of natural factors,such as shale properties,bedding plane and natural fractures,and controllable factors,proppant,temperature,pressure,CO_(2) concentration and injection rate on fracture initiation and propagation are clarified.The methods of supercritical CO_(2) fracturing process,thickener and proppant optimization to improve the efficiency of supercritical CO_(2) fracturing are discussed.In addition,some new technologies of supercritical CO_(2) fracturing are introduced.The challenges and prospects in the current research are also summarized.For example,supercritical CO_(2) is prone to filtration when passing through porous media,and it is difficult to form a stable flow state.Therefore,in order to achieve stable fracturing fluid suspension and effectively support fractu res,it is urge nt to explo re new fracturing fluid additives or improve fracturing fluid formulations combined with the research of new proppants.This paper is of great significance for understanding the behavior mechanism of supercritical CO_(2) in shale and optimizing fracturing technology.展开更多
The CO_(2)/sand dry-frac process is a waterless fracturing technology in which CO_(2)instead of water is used as fracturing fluid.The application of the technology abroad(in the USA and Canada)shows that it works well...The CO_(2)/sand dry-frac process is a waterless fracturing technology in which CO_(2)instead of water is used as fracturing fluid.The application of the technology abroad(in the USA and Canada)shows that it works well in stimulating low-pressure,low-permeability,strong water-locking/water sensitive reservoirs.Thus,a series of experimental studies were carried out on its production increase mechanism,fracturing fluid system,pressurized air-tight sand blender,and fracturing process.Some conclusions were made.First,the CO_(2)viscosity enhancement technology can raise the critical CO_(2)viscosity by 240–490 times,significantly improving the sand-carrying and fracture-making capacities of CO_(2)fracturing fluid,so it is a key technique in CO_(2)/sand dry-frac process.Second,with the development of CO_(2)pressurized air-tight sand blender,a complete set of key devices for the CO_(2)/sand dry-frac process can be made in China,meeting the requirements of the fracturing operation.Third,fully automatic flowback is also realized.Fourth,CO_(2)instead of water is used in this fracturing operation,saving a large amount of water consumed in fracturing,and lowering cost.Fifth,the CO_(2)/sand dry-frac process is feasible and suitable for the stimulation of low-pressure,low-permeability and strong water-locking reservoirs,with substantial production increase.展开更多
文摘Our database tracking of USA water usage per well indicates that traditionally shale operators have been using, on average 3 to 6 million gallons of water; even up to 8 million for the en- tire life cycle of the well based on its suitability for re-fracturing to stimulate their long and lateral ho- rizontal welis. According to our data, sourcing, storage, transportation, treatment, and disposal of this large volume of water could account for up to 10% of overall drilling and completion costs. With in- creasingly stringent regulations governing the use of fresh water and growing challenges associated with storage and use of produced and flowback water in hydraulic fracturing, finding alternative sources of fracturing fluid is already a hot debate among both the scientific community and industry experts. On the other hand, waterless fracturing technology providers claim their technology can solve the concerns of water availability for shale development. This study reviews high-level technical issues and opportunities in this challenging and growing market and evaluates key economic drivers behind water management practices such as waterless fracturing technologies, based on a given shale gas play in the United States and experience gained in Canada. Water costs are analyzed under a variety of scenarios with and without the use of （fresh） water. The results are complemented by surveys from several oil and gas operators. Our economic analysis shows that fresh water usage offers the greatest economic return. In regions where water sourcing is a challenge, however, the short-term economic advantage of using non-fresh water-based fracturing outweighs the capital costs required by waterless fracturing methods. Until waterless methods are cost competitive, recycled water usage with low treatment offers a similar net present value （NPV） to that of sourcing freshwater via truck, for in- stance.
文摘With the increasing demand for energy,traditional oil resources are facing depletion and insufficient supply.Many countries are rapidly turning to the development of unconventional oil and gas resources.Among them,shale oil and gas reservoirs have become the focus of unconventional oil and gas resources exploration and development.Based on the characteristics of shale oil and gas reservoirs,supercritical CO_(2) fracturing is more conducive to improving oil recovery than other fracturing technologies.In this paper,the mechanism of fracture initiation and propagation of supercritical CO_(2) in shale is analyzed,including viscosity effect,surface tension effect,permeation diffusion effect of supercritical CO_(2),and dissolution-adsorption effect between CO_(2) and shale.The effects of natural factors,such as shale properties,bedding plane and natural fractures,and controllable factors,proppant,temperature,pressure,CO_(2) concentration and injection rate on fracture initiation and propagation are clarified.The methods of supercritical CO_(2) fracturing process,thickener and proppant optimization to improve the efficiency of supercritical CO_(2) fracturing are discussed.In addition,some new technologies of supercritical CO_(2) fracturing are introduced.The challenges and prospects in the current research are also summarized.For example,supercritical CO_(2) is prone to filtration when passing through porous media,and it is difficult to form a stable flow state.Therefore,in order to achieve stable fracturing fluid suspension and effectively support fractu res,it is urge nt to explo re new fracturing fluid additives or improve fracturing fluid formulations combined with the research of new proppants.This paper is of great significance for understanding the behavior mechanism of supercritical CO_(2) in shale and optimizing fracturing technology.
文摘The CO_(2)/sand dry-frac process is a waterless fracturing technology in which CO_(2)instead of water is used as fracturing fluid.The application of the technology abroad(in the USA and Canada)shows that it works well in stimulating low-pressure,low-permeability,strong water-locking/water sensitive reservoirs.Thus,a series of experimental studies were carried out on its production increase mechanism,fracturing fluid system,pressurized air-tight sand blender,and fracturing process.Some conclusions were made.First,the CO_(2)viscosity enhancement technology can raise the critical CO_(2)viscosity by 240–490 times,significantly improving the sand-carrying and fracture-making capacities of CO_(2)fracturing fluid,so it is a key technique in CO_(2)/sand dry-frac process.Second,with the development of CO_(2)pressurized air-tight sand blender,a complete set of key devices for the CO_(2)/sand dry-frac process can be made in China,meeting the requirements of the fracturing operation.Third,fully automatic flowback is also realized.Fourth,CO_(2)instead of water is used in this fracturing operation,saving a large amount of water consumed in fracturing,and lowering cost.Fifth,the CO_(2)/sand dry-frac process is feasible and suitable for the stimulation of low-pressure,low-permeability and strong water-locking reservoirs,with substantial production increase.
