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Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Natural Gas Geoscience is the property of Natural Gas Geoscience and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Natural Gas Geoscience is the property of Natural Gas Geoscience and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on the data of more than 40 wells( 12 drainage wells) in East Yunnan-Western Guizhou area,the influencing factors of drainage dynamic in Enhong, Laochang and Tucheng blocks are discussed through the ex-traction of drainage dynamic typical indexes of CBM wells and the comprehensive analysis of geological and engineering factors, combined with numerical simulation and the primary drainage rate optimization steps are finally put forward. The results show that there is a great difference in the drainage dynamic of CBM wells in the study area. The producing resource abundance and permeability determine the gas production capability of CBM wells as basic factors. The higher the producing resource abundance and the permeability are, the higher gas production is. Meanwhile, the reservoirs with coal body structure Type 1 and II have a higher gas production compared to that with coal body structure Type III. The primary drainage rate is the key controlling factor of drainage dynamics of CBM wells. When the primary drainage rate is relatively high, even with the permeability and the producing resource abundance being high, the gas production is still relatively low. Controlling the primary drainage rate has two meanings;one is to slow down the reduction of absolute permeability( stress-sensitive), and the other is to delay the occurrence of two-phase flow, both having objective to extend the depression cone to maximum. Based on the above understanding, it is pointed out that slow drainage should be key in the study area. A low rate-ladder type pressure reduction, during primary drainage, is proposed. This pressure reduction regime has a certain practical significance for co-production from multiple-coalbeds in East Yunnan-Western Guizhou area. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Coalbed methane (CBM) exploitation feasibility is determined by both hydrogeological conditions and hydraulic fracturing conditions of coal seams.Exploitation feasibility evaluation and reservoir evaluation constitute two important aspects of coalbed methane recoverability.In this paper,through the drainage efficiency comparison between Shouyang and Shizhuang CBM blocks in Qinshui Basin,CBM exploitation feasibility evaluation was discussed from four aspects,including coal measures aquosity,faulting,in-situ-stress state and the lithology combination of coalbed with adjacent rocks.An evaluation flow chart for CBM exploitation feasibility evaluation was finally proposed.The study shows that coal measures aquosity plays an important role in the CBM exploitation feasibility of whole CBM Block.The hydraulic communication between coal seams and surrounding aquifers through faults weakens the closeness of wellbore-fracturing coal system,leading to lower exploitation feasibility of CBM resources near the faults.The stronger the coal measures aquosity is,the greater risk of high water production in wells near faults will take place and the lower exploitation feasibility will be.The in-situ stress state of coalbed and lithology combination of coal seams with adjacent rocks constitute the objective conditions of CBM exploitation feasibility,and a comprehensive evaluation of exploitation feasibility should be done through combining in-situ stress state,the strength of horizontal stress and fracturing volumes.The qualitative/semi-quantitative evaluation method of CBM exploitation feasibility,based on hierarchy analysis considering coal measures aquosity,faults,the in-situ stress state and the lithology combination of coal seams with adjacent rocks,can be applied to CBM block selection and well/coalbeds selection through the whole process of CBM exploration and development. [ABSTRACT FROM AUTHOR]

The characteristics of a CBM well performance is complex due to multiple influencing factors. It is beneficial for well site/layer selection and fracturing design to diagnose the performance of single CBM well. Based on the geological conditions and well performance data of 30 CBM wells producing from No.3 coal seam of Permian Shanxi formation in Shizhuang block，this paper studies the characteristics of CBM Wells performances and the relationship between gas production and water production. A negative enveloping relationship between gas production and water production is revealed，with high water production generally inhibiting high gas production. From a point of view of closeness of system borehole-stimulated coal interval，the mechanism of high water production due to outside water supply from sandstone aquifers is discussed and a hierarchical performance diagnostic method for single CBM well is proposed. The performance of some typical well are diagnosed using this hierarchical method，showing the method provides a tool for understanding the performance of single CBM well in Shizhuang CBM block and the application of this method can be extended to other CBM blocks. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Identification of aquifers influencing the drainage of coalbed methane wells are essential for diagnostic of well performance，selection of well sites/coalbeds for development operations and for fracturing design. Facing to the high water production problem in Shouyang CBM Exploration Area，In this article，regional hydrodynamic head and energy distribution characteristics，aquosity of snadstones and limestones in the coal measures，lithological association surrounding the target coals，hydraulic communication of coals with the surrounding aquifers and detailed analysis of water sources of typical wells were comprehensively studied. It is recognized that regional hydrodynamics and permeabilities of coalbed reservoirs control the average water production level，while the difference of water productions among wells are mainly controlled by local geological and engineering conditions (faults，hydraulic fractures types and height，and lithological assemblage surrounding the target coals) and hydraulic fractures are one mode，besides faults，of hydraulic communication between target coals and their surrounding aquifers. It is finally concluded that the sandstones in coal measures are the main water source layers and the limestones in Taiyuan formation has weak influence on the well drainage and water production. It is suggested that the selection of well sites/coalbeds for CBM development operations and fracturing design should be relied on the vertical combination of target coals and surrounding sandstone aquifers. [ABSTRACT FROM AUTHOR]

Fracturing curve of coalbed methane (CBM) wells offers lots of dynamic information of fracture extension,which is able to reflect fracturing effect.Based on the fracturing data of 45 CBM wells where coal seam 3 was only fractured and drained in Shizhuang CBM block,fracturing curve types were classified and the relationship between fracturing curve types and gas production of CBM wells were discussed.Most importantly,the formation mechanism of fracturing curve types were first time discussed.The study shows that the fracturing curves of coal seam 3 in Shizhuang CBM block can be divided,according to the morphological characteristics during sand-bearing stage,into four types including stable,descending,rising and fluctuating.The stable and descending curves always lead to high gas productions.However,the rising and fluctuating curves are usually corresponding to low gas productions.The in-situ stress types and related hydraulic fracture types have a controlling effect on fracturing curve types.In a field of in-situ stress type II (σH >σh >σv),horizontal hydraulic fractures accompanied with “T”-shape or “工”-shape complex fractures are developed and results in rising and fluctuating fracturing curves.However,in a region where the in-situ stress type is either type III(σH >σv >σh)or type I (σv >σH >σh),vertical hydraulic fractures or vertical hydraulic fractures accompanied with “T”-shape or “工”-shape complex fractures are developed and results in stable and descending fracturing curves.The distribution of fracturing curve types in Shizhuang CBM block shows a certain regularity.In the eastern part of the block where in-situ stress type II (σH >σh >σv) or type III(σH >σv >σh)was identified,the stable,descending,rising and fluctuating fracturing curve types were observed.In the western part of the block where in-situ stress type I (σv >σH >σh) were identified,only the stable and fluctuating fracturing curve types were observed. [ABSTRACT FROM AUTHOR]