Geological characteristics and co-exploration and co-production methods of Upper Permian Longtan coal measure gas in Yangmeishu Syncline, Western Guizhou Province, China

Coal measure gas(also known as coal-bearing unconventional gas)is the key field and development direction of unconventional natural gas in recent years.The exploration and evaluation of coal measure gas(coalbed methane,coal shale gas and coal measure tight sandstone gas)from single coalbed methane has greatly expanded the field and space of resource evaluation,which is of positive significance for realizing the comprehensive utilization of coal resources,maximizing the benefits and promoting the innovation of oil and gas geological theory and technological advances in exploration and development.For the first time,in Yangmeishu Syncline of Western Guizhou Province,the public welfare coalbed methane geological survey project of China Geological Survey has been carried out a systematic geological survey of coal measure gas for the Upper Permian Longtan Formation,identified the geological conditions of coal measure gas and found high quality resources.The total geological resource quantity of coalbed methane and coal shale gas is 51.423×109 m3 and the geological resource abundance is up to 566×106 m3/km2.In this area,the coal measures are characterized by many layers of minable coal seams,large total thickness,thin to the medium thickness of the single layer,good gas-bearing property of coal seams and coal measure mudstone and sandstone,good reservoir physical property and high-pressure coefficient.According to the principle of combination of high quality and similarity of key parameters of the coal reservoir,the most favorable intervals are No.5-2,No.7 and No.13-2 coal seam in Well YMC1.And the pilot tests are carried out on coal seams and roof silty mudstone,such as staged perforation,increasing hydraulic fracturing scale and"three gas"production.The high and stable industrial gas flow with a daily gas output of more than 4000 m3 has been obtained,which has realized the breakthrough in the geological survey of coal measure gas in Southwest China.Based on the above investigation results,the geological characteristics of coal measure gas in the multi-thin-coal-seam-developed area and the coexploration and co-production methods,such as the optimization method of favorable intervals,the highefficiency fracturing and reservoir reconstruction method of coal measures,and the"three gas"drainage and production system,are systematically summarized in this paper.It will provide a reference for efficient exploration and development of coal measure gas in similar geological conditions in China.

Industrial production of unconventional gas in coal-measure of Well HJD1 in Jixi Basin,Eastern Heilongjiang Province,China

1.Objective The coalbed methane(CBM)exploration in the Jixi Basin began with the gas control in the coal mine(Fig.1).The object is mostly the main minable coal seams shallower than 1000 m.The coalbed methane and unconventional gas in coal-measure deeper than 1000 m are rarely concerned(Bi CQ et al.,2018).The coal measure“three gas”referred to as coalbed methane,coal-measure shale gas,and tight sandstone gas is the main part of the unconventional gas in coal-measure.Since 2015,China Geological Survey(CGS)has carried out a systematic geological survey and evaluation of unconventional gas in coal measure of the Chengzihe Formation of Lower Cretaceous in this area.The favorable areas and target areas have been optimized.This study is to obtain the coal-measure reservoir parameters and gas-bearing parameters of mid-deep layers of the Chengzihe Formation(1000-1500 m),to ascertain the development of gas-bearing layers.It is also to search for new methods and technologies,such as the production layer optimization methods,the reservoir reconstruction process,and the joint production of coal measure“three-gas”of the thin interbedded coal-measure composite reservoir,to obtain high industrial production,and to evaluate the technical recoverability of unconventional gas in coal-measure.

A major breakthrough in geological survey of coal measure gas in Southern Sichuan, China

1.Objectives Southern Sichuan is located in Xuyong-Junlian superimposed fold belt in the southern margin of Sichuan Foreland Basin,with an area of about 15000 km^2.The coal measures of Upper Permian Xuanwei Formation and Longtan Formation are characterized by mudstone,clayey mudstone,fine sandstone,siltstone,and coal seams interbedded.The coal seams and carbonaceous mudstone have good hydrocarbon generation potential.The coal measure“three gas”includes coalbed methane(CBM),coal shale gas and coal measure tight sandstone gas coexist.There was a breakthrough in the CBM survey in Junlian,Gulin,and other areas in Southern Sichuan(Yin ZS et al.,2019).But it lacks a comprehensive and systematic evaluation of coal measure gas resource potential.