Study On The Multi-Superimposed Aquifer System Of Coal Seams And Source Discrimination Of Commingling CBM Produced-Water

Based on the regional hydrogeology and the achievement of CBM exploration,Multiple Superposed CBM Systems,existed in Zhuzang syncline of western Guizhou province,were regarded as the research object in this paper. Applying the methods of field observation and samples’ tests as well as subjects of Mineralogy,Coalbed Methane Geology,Hydrology,Geochemistry,Isotope Hydrology,Trace Element Geochemistry,Statistics and other points of view,the Multiple Superposed Aquifer Systems of Coal Reservoirs were divided. Systematic study of occurrence law of clay minerals,groundwater chemistry,ion-combination,environment isotope,radioactive isotope and soluble trace elements were accomplished. The distribution characteristics of water dynamic field of research area were discussed while strontium isotope mixing model of different aquifer systems and discrimination model of water sources identification during the process of commingled drainage were built. The research area was divided into three sets of coal reservoir superposed aquifer system named the upper aquifer system,the middle aquifer system and lower aquifer system respectively. The relationships between occurrence and distribution of Clay minerals and reservoir’s porosity and permeability as well as the underground fluid are closely. The concentration of mineralization,hydrogen and oxygen isotopes,strontium isotope,iodine isotope of groundwater in each aquifer system increased with the increase in buried depth. The age of water of upper and middle aquifer system were less than 2Ma and the lower aquifer system was 17.28 Ma while the aquifer systems were evolved from tiny amount of ancient meteoric water and high proportion of modern meteoric water. Fuzzy Comprehensive Evaluation of Entropy Weight and Extension Identification Method identified the sources of produced water and reflected that the high pressure CBM-bearing system influenced the other system’s drainage. Taking element set including Ca,K,Mg,Na,Sr,Li,Rb and Ba as the eigen elements,in which Ca,Mg,Na,Li were calibration elements,CBM well’s produced water could be identified. The results of this paper could make contribution to orderly development of CBM in the Multiple Superposed CBM System.