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 review and research on comprehensive characterization of microscopic shale gas reservoir space

In this paper,substantial domestic and foreign research results of microscopic shale reservoir space were systemically reviewed,the research history consisting of simple observation and qualitative classification,quantitative research,the combination of qualitative and quantitative research successively as well as the characteristics of each research stage were summarized.In addition,the current problems existing in the characterization methods of shale reservoir space were also analyzed.Furthermore,based on massive actual detection of typical core samples obtained from more than 50 global shale gas wells and relevant practical experience,a comprehensive characterization method of combining qualitative with the semiquantitative characterization was put forward.In detail,the indicators of the qualitative characterization include pore combination type and organic-matter microscopic morphology type,while the core elements of the semi-quantitative characterization include the percentage of the organic-matter area and the plane porosity of the pores of different types.Based on the reference of the naming and classification of rocks,the three-end-member diagram method was used to characterize microscopic shale reservoir space.This is achieved by plotting the three end-member diagram of 3 kinds of first-order critical reservoir spaces,i.e.,organic-matter pores,matrix pores,and micro-fractures,in order to intuitively present the features of the microscopic pore combination.Meanwhile,statistic histograms of organic-matter microscopic morphology type and the plane porosity of different types of pores were adopted to characterize the development degree of second-order pores quantitatively.By this comprehensive characterization method,the importance of both pore combination and the microscopic morphology of organic matter were emphasized,revealing the control of organic-matter microscopic morphology over the organic-matter pores.What is more,high-resolution FE-SEM was adopted to obtain semi-quantitative statistics results.In this way,the features of pore development and pore combination were quantified,not only reflecting the types and storage capacity of the microscopic shale reservoir space,but also presenting the hydrocarbongenerating potential of organic matter in shale.Therefore,the results of this research are capable of providing in-depth microscopic information for the assessment and exploration and development of shale gas resources.

Deposition rate of hafnium crystal bar by iodide process

Single variable and deposition weight methods were adopted in the experiment. The hafnium crystal bar was fabricated by the iodide process. Influence of hafnium filament temperature（K value）, temperature controlling method, types of feed, and the loading methods on the deposition rate were studied. The results show that the K value, temperature control method, types of feed, and the loading methods have obvious effects on the deposition rate of the hafnium crystal bar. The deposition rate increases with the K value rising in the range of certain temperature;the salt bath controlling temperature method could effectively obtain the better deposition rate; the greater the contact areas of the feeds are, the faster the deposition rate is.So, the optimal iodide deposition techniques of preparing hafnium crystal bar are as follows： hafnium turnings as feed,molybdenum feed retainer charging, salt bath temperature controlling under the higher K value.

Technological conditions for purification of hafnium by iodide process

In nuclear industry,the purity of hafnium control rod is usually significant,and the process parameters will affect the impurity contents.In this study,the four key factors(filament temperature,retort materials,feeds,and iodide reaction time)were investigated.It is found that the impurity contents of Fe,Ni in the hafnium crystal bar decrease with the K value rising.Both the retort materials and feed types have obvious influence on the impurity contents of hafnium crystal bar.The iodide reaction time has little effect on the impurity contents of hafnium crystal bar.