Evaluation Of Water Resources Carrying Capacity Based On Fuzzy Model In Shale Gas Exploitation Area

Shale gas is an unconventional natural gas and its exploitable reserves are far greater than conventional natural gas in China,the exploitation of shale gas is an effective way for China to adjust the current energy use structure to match the carbon emission reduction plan.At present,hydraulic fracturing is still the main way as shale gas exploitation is still in its infancy,thus water consumption is the bottleneck restricting shale gas exploitation.Whether large-scale development of shale gas will cause pressure on water resources has not been comprehensively and properly quantitatively studied and analyzed.There is no clear conclusion as to whether the influencing factors of water used for shale gas exploitation and other environmental,production and domestic water distribution are serious or not.The applicability of current water usage patterns also needs to be verified.Therefore,the evaluation of water resources carrying capacity is the key.However,the selection of evaluation indicators,evaluation method and evaluation range of water resources carrying capacity will strong depend on differences of region geological conditions and resource exploitation process.Based on the karst hydrological characteristics,the environmental,social and economic indicators have been studied according to the whole life cycle of water consumption during shale gas exploitation,and indicators system has been proposed to evaluate water resources carrying capacity in Sichuan Changning shale gas exploration based on the fuzzy evaluation model by using Matlab software,which will enhance the level of water resources management for the exploitation of shale gas in China.The research results show that:?1?Based on fuzzy evaluation model,a three-layer fuzzy evaluation indicators system of pressure-state-response has been proposed,including 12 population growth,GDP per capita,water consumption for shale gas exploitation,state system of water environment and the corresponding social and economic indicators,among them,the proportion of local shale gas water consumption,proportion of water consumption cycle,proportion of water reinjection and water consumption per unit capacity are the characteristic indexes for the evaluation of water resources carrying capacity in shale gas mining areas.The indicator system can integrate the whole life cycle water resource consumption of shale gas exploitation,karst geology and landform,hydrological characteristics,ecological carrying capacity evaluation and sustainable development indicators system.?2?The established pressure-state-response fuzzy evaluation method was used to evaluate the water resources carrying capacity of the Changning shale gas exploration area,according to the results of Changning shale gas exploration area from 2012 to2016,the level of evaluation is V₄ grades,it is under a strong pressure state,whereas the water resources carrying capacity can meet the requirements of local water resources supply and demand.The evaluation result is consistent with the fact,which proves that the indicators,weight and membership degree in evaluation process are reasonable and the evaluation method is effective.?3?The total water consumption in 2020,2025,2030,2035 and 2040 in Changning shale gas area are predicted by using established fuzzy evaluation model.The results show that the water resource carrying capacity in 2020 and 2025 belongs to the V4 level,and to a certain extent it belongs to the bearing state,which can support the large-scale development of shale gas in the research area.The carrying capacity of water resources in 2030,2035 and 2040 is not in harmony with the supply and demand of water resources.Therefore,it is very important to reasonably plan the scale of shale gas development,improve the level of science and technology,and control and balance the water use in all aspects.?4?Based on the indicators system of shale gas exploitation,the fuzzy evaluation method can quantify the impact of shale gas exploitation process on water consumption through weight,and take county-level administrative region as the evaluation unit,the result is more objective and evaluation method is easy to apply to manage water resources.This model is not only suitable for the evaluation of water resources carrying capacity in karst areas,but also can be used in other areas with insufficient water resources.