Coalbed Methane Enrichment And Accumulation Mode & Prospective Area Prediction In Gujiao District

In terms of newer CBM blocks, Coalbed Methane enrichment and accumulation mode as well as prospective area prediction are always theoretical and technical problems which puzzle Coalbed Methane industry. It is not only a theoretic subject, but also a major practical topic need to be solved urgently during Coalbed Methane exploration and development process. Therefore, the CBM from middle-high rank coals in Gujiao district is selected as the study object of this paper. Large amounts of oil and natural gas exploration achievements, CBM exploration and development achievements et al were collectted systematically. Samples of coal, coal bed methane, water produced from coal seam and coal roof and floor were taken from the study area. Based on tests, experiments and previo us study results in terms of coal rock industry analysis, vitrinite reflectance, maceral quantitative, porosity, permeability, gas composition, adsorption isotherm, N2 adsorption and NMR et al, and the previous researches were also referred. M ulti- level and multi- means comprehensive studies have been conducted on Gujiao district’s reservoir conditions, accumulation geological conditions, main controlling factors, enrichment and accumulation mode. Meanwhile, on the basis of assessment of main controlling factors configuration relationship by multi- level fuzzy evaluation method, the favourable blocks were optimized. Finally, the guidance for the efficient development of CBM was provided. The obtained major achievements and conclusions are as follows:1. Coals began to generate moisture in the late Triassic,but they all did not reach the peak of moisture generated. After entering the second stage of generating gases, differentiation appeared in different sections. The eastern area leaded into magmatic metamorphic stage in early Yanshan Period, generating large amounts of moisture. However, the western area steped into the secondary hydrocarbon generation and hydrocarbon peak in middlie- late Yanshan. Hydrocarbon generation factors related to CBM enrichment and accumulation mainly contained three aspects: the first, the geological period of secondary hydrocarbon generation; the second, the generating process that secondary hydrocarbon generation experienced and the stage that it reached; the last, the burial history of coal seams after hydrocarbon generation stoped.2. The CBM enrichment and accumulation mode of Gujiao area is "multi- factor comprehensively affect, one or two main factors control" model. The final ranking according to their significance to enrichment and accumulation is: structure> magmatism>sedimentary environment> hydrogeological conditions. The most important controlling factors are tectonic activity and magmatic activity. Superimposed on a background of magma intrusion seam depth is the main factors controlling the coal seam gas content, gas content increases with increasing depth of the coal seam. The gas content of same coal seam is significantly higher in local area consistent with magma emplacement.3. Based on the study about controlling factors of CBM enrichment and accumulation, resources conditions, saving conditions, development conditions were selected to be the secondary evaluation index, seam thickness and gas content, permeability et.al were as the tertiary evaluation index. No. 2 coal seam bed methane enrichment yielding the most favorable areas(Ⅰ class) mainly located in the east of the well GJ02(Xiaohuigou area); theⅠclass favorable areas of No. 8 coal seam mainly distributed in the south of GJ02 well; theⅠclass favorable areas of No. 9 coal seam mainly distributed in the both sides of the Duerping fault, which is Duerping mine area and Chengjiagou mining area.