The Evaluation Method And Its Application Of Shale Gas Resource Of Es₃^x In The West Of Langgu Depression

In this paper,we take the shale in Es₃^x section of shahejie formation which in the west of Langgu depression as an object of study.The segment,developing huge thick-dark shales,with gas logging abnormal phenomenon,is a potential favorable area for exploration of the shale gas.On the basis of the comprehensive results of previous studies,through core observation,indoor experimental analysis to make sure the distribution characteristics of the shale and to evaluate organic and inorganic heterogeneity,as well as to establish the adsorbed gas and free gas evaluation model,we conduct systematic research on the shale gas content and its variation.Through the above research contents,we preliminarily estimate the potential shale gas resource.To carry out the study of the evaluation method of shale gas resource,can provide the evaluation method of shale gas content,which has an important guiding significance for the development and utilization of unconventional gas resources.We have achieved the following results and understanding:Es₃^x section of Langgu depression develops two main types sedimentary facies:nearshore subaqueous fans and deep or semi-deep lake.The main types of shale is black shale,its cumulative thickness is huge,which thickest can amount to thousands of meters and the average thickness is 534.5m.The organic matter abundance?TOC?of the shale in Es₃^x section is mainly distributed between 0.6%to 1.5%and its average percentage is 0.75%;the organic matter type is?₂,the organic matter maturity?R_o?is mainly distributed in the range of 0.5%to 0.9%,with a low mature moisture stage of evolution.The shales has high content of clay mineral and low content of brittleness mineral.Under the formation temperature and pressure,the adsorption capacity of TOC,clay minerals and other minerals of shale?gugu1 well?respectively are 30m³/t,1.25m³/t and0.28m³/t.Take Gugu1 well as an example?TOC=1.5%?,the gas content variation of the shale gas as follows:?1?When the depth increasing,adsorbed gas content decreases,while the decreasing trend will gradually slow down with the depth increasing;the free gas content increases too;the total gas content increases first,between 1200m and 2000m,the total gas content decreases,when the depth greater than 2000m,the total gas content increases again.?2?The free gas content,adsorbed gas content and total gas content will decrease with the decreasing pressure,while the size of the free gas content decreased is more noticeable.?3?The adsorbed gas content and the total gas content decrease with the increasing temperature,and the free gas content will increase with the increasing temperature,while the size of the adsorbed gas content decreased is more noticeable.The average adsorbed gas content of the shale in Es₃^x section of shahejie formation which in the west of Langgu depression is 0.88m³/t,and the average of free gas content is0.69m³/t.By using the volume method,we can estimate the total geological reserves of shale gas is 125.48�10⁸m³.