Research On Reservoiring Patterns And Enrichment & High-Production Rules Of Coalbed Methane In Surat Basin,Austrilia

The Walloon Coal Measures(WCM)in Surat Basin is a low rank coal which has thin layer,low gas content and high production with high permeability and it is the main coalbed methane production formation of Australia.It is believed that the reservoiring conditions have not been researched systematically and the reservoiring patterns of the WCM were studied weakly.And the enrichment & high-production rules have not been understood clearly.So the high efficiency development of the WCM is limited.This paper has systematically studied the reservoiring patterns and enrichment & high-production rules of the WCM basing on seismic data,well log data,core experiment data and well production data.Main achievements and knowledge obtained in this paper as fllows:(1)The distribution,source,reservoir and preservation conditions of the WCM have been studied systematically.The WCM is buried shallow and formed by multiple thin coal layers which has low maturity and low permeability and the methane of WCM is mainly consisted of secondary biogenic gas.The top and bottom of the WCM is tight rocks and the direction of the groundwater in the WCM is opposite to the methane diffusion direction,which form a vertical and horizontal sealed system to the methane in the WCM.(2)The reservoiring processes of the WCM have been restored and the reservoiring patterns of the WCM have been established.The WCM has experienced the processes of tectonic subsidence,tectonic uplift,bacteria entering into the coal,methane generation and preservation and reservoiring,which formed the coalbed methane reservoir with mixed origin methane sealed by hydrodynamic and lighology on the monocline structure.The reservoiring patterns of the WCM can be divided into anticline pattern,syncline pattern and slope pattern and the anticline pattern,syncline pattern is of more enrichment than the slope pattern.The Walloon coalbed methane reservoir is unique in the world because it has a combination of dual carbon source,super thin layer,dual sealed system and medium class hydrodynamic.(3)The main factor of the production of WCM has been identificated and the enrichment& high-production rules of the WCM have been concluded.The gas content is the main factor of production in the high permeability area while the permeability is the main factor in the low permeability area.The biomethane and thermogenic methane provide abundant gas source and which is enriched in the local anticline and syncline structure.High permeability guarantees high production and the gas content controls the amount of the well production.(4)The quantitative evaluation method of the enrichment & high-production advantage of the WCM has been proposed and the enrichment & high-production prospective areas of WCM have been predicted.The WCM in the study area can be divided into three areas and Area I has the best enrichment & high-production advantage while Area II is worse than Area I and Area III is the worst.Area I contains the center and southern part of Central Development Area,the small part area of southern part of Northern Development Area and the small part area of southeast part of Southern Development Area,which is the enrichment &high-production prospective area of the study area.The research results of this paper doesn’t only provide guide to the development of the low-production area of the study area but also give reference case to the low rank coal exploration and development in China or the other countries.