川南地區(qū)龍馬溪組孔隙特征與頁巖氣賦存
發(fā)布時間：2018-07-22 14:51
【摘要】：下志留統(tǒng)龍馬溪組是我國頁巖氣勘探開發(fā)的有利層系之一,認識龍馬溪組頁巖孔隙演化與頁巖氣賦存具有理論意義。論文以川南地區(qū)龍馬溪組為研究對象,就頁巖孔隙特征與頁巖氣賦存等進行了較深入的研究。研究區(qū)位于四川盆地南緣,構造相對簡單,地層分布穩(wěn)定。研究目的層龍馬溪組頁巖有機碳含量較高,平均2.44%;有機質熱演化程度高,平均2.90%,處于過成熟階段。龍馬溪組頁巖組分以石英、黏土礦物及斜長石占主體;黏土礦物以伊蒙混層與伊利石為主。研究區(qū)龍馬溪組頁巖孔隙以基質孔隙為主,不同礦物組分對頁巖孔隙的貢獻程度不同,其中單位質量的有機質產生孔隙體積最大,黏土礦物其次,脆性礦物最小。龍馬溪組頁巖孔隙發(fā)育相對穩(wěn)定,頁巖總孔隙體積平均0.0081cm3/g;比表面積平均1.58m~2/g;頁巖介孔孔隙優(yōu)勢孔徑2~25nm;微孔優(yōu)勢孔徑0.3~0.9nm。龍馬溪組頁巖孔隙符合分形規(guī)律,具有自相似性,宏孔孔隙結構較介孔、微孔更為復雜。川南地區(qū)馬溪組頁巖層理發(fā)育,平行層理方向頁巖初始孔隙度高于垂直層理方向頁巖,頁巖單位密度層理提供的初始孔隙度約0.14%。隨埋深增大,層理對頁巖孔隙度的影響逐漸減小,當埋深足夠大時(3000m),頁巖孔隙度主要是由基質孔隙度提供。龍馬溪組頁巖平行層理方向初始滲透率總體高于垂直層理方向頁巖,且頁巖滲透率隨有效應力增加呈遞減趨勢,根據應力敏感程度不同,滲透率變化可分為敏感區(qū)、過渡區(qū)和不敏感區(qū)三個階段。壓力對頁巖孔隙變化起到壓縮作用,孔隙體積隨壓力增大總體呈減小趨勢。隨著埋深增大,頁巖吸附氣含量整體呈先增大后減小的變化趨勢,但在實際地層中埋深較淺的頁巖儲層由于容易導通地表,形成逸散通道,含氣量較低;頁巖游離氣含量隨埋深增大呈先增大后平穩(wěn)的變化趨勢,且儲層壓力系數越高,游離氣含量越大;頁巖總含氣量隨埋深增大總體呈先增大后逐漸減小的變化趨勢,相同埋深下,儲層壓力系數越高,總含氣量越大且下降速率越小。在埋深較淺時頁巖氣以吸附氣占主導,埋深較大時,則以游離氣占主導。儲層壓力系數越大,頁巖游離氣占主導的臨界深度越淺。
[Abstract]:The Lower Silurian Longmaxi formation is one of the favorable strata for shale gas exploration and development in China. It is of theoretical significance to understand the evolution of shale pores and the occurrence of shale gas in Longmaxi formation. Taking Longmaxi formation in south Sichuan as the research object, the pore characteristics of shale and the occurrence of shale gas were studied in this paper. The study area is located in the southern margin of Sichuan basin with relatively simple structure and stable stratigraphic distribution. The content of organic carbon in shale of Longmaxi formation is relatively high, with an average of 2.44, and the thermal evolution of organic matter is high, with an average of 2.90, which is in the over-mature stage. The main shale components of Longmaxi formation are quartz, clay and plagioclase, and the clay is mainly composed of Illite and Illite. The shale pores of Longmaxi formation in the study area are dominated by matrix pores, and the contribution of different mineral components to the shale pores is different, in which the pore volume per unit mass of organic matter is the largest, the clay mineral is the second, and the brittle mineral is the least. The shale pore size of Longmaxi formation is relatively stable, the average total pore volume of shale is 0.0081 cm 3 / g; the average specific surface area is 1.58 mm2 / g; the dominant pore size of shale mesoporous is 225 nm; the dominant pore size of micropore is 0.30.9nm. The shale pores of Longmaxi formation accord with fractal law and have self-similarity. The macropore structure is more complex than mesoporous pore and micropore structure. The shale bedding of Maxi formation is developed in south Sichuan. The initial porosity of shale in parallel direction is higher than that in vertical direction, and the initial porosity provided by shale unit density bedding is about 0.14. With the increase of buried depth, the effect of bedding on shale porosity decreases gradually. When the buried depth is large enough (3000m), shale porosity is mainly provided by matrix porosity. The initial permeability in parallel bedding direction of Longmaxi formation is generally higher than that in vertical bedding direction, and the shale permeability decreases with the increase of effective stress. According to the stress sensitivity, the change of permeability can be divided into sensitive areas. Transition zone and insensitive region are three stages. The pore volume decreases with the increase of pressure. With the increase of buried depth, the adsorption gas content of shale increases first and then decreases, but the shallower shale reservoir is easy to lead to the surface of the ground in the actual formation, forming an escape channel and low gas content. The content of shale free gas increases first and then steadily with the increase of buried depth, and the higher the reservoir pressure coefficient, the greater the content of free gas, and the total gas content of shale increases firstly and then decreases gradually with the increase of buried depth. The higher the reservoir pressure coefficient, the larger the total gas content and the smaller the decreasing rate. When the buried depth is shallow, the adsorption gas dominates the shale gas, and the free gas dominates when the buried depth is larger. The greater the reservoir pressure coefficient, the shallower the critical depth dominated by shale free gas.
【學位授予單位】：中國礦業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：P618.13
[Abstract]:The Lower Silurian Longmaxi formation is one of the favorable strata for shale gas exploration and development in China. It is of theoretical significance to understand the evolution of shale pores and the occurrence of shale gas in Longmaxi formation. Taking Longmaxi formation in south Sichuan as the research object, the pore characteristics of shale and the occurrence of shale gas were studied in this paper. The study area is located in the southern margin of Sichuan basin with relatively simple structure and stable stratigraphic distribution. The content of organic carbon in shale of Longmaxi formation is relatively high, with an average of 2.44, and the thermal evolution of organic matter is high, with an average of 2.90, which is in the over-mature stage. The main shale components of Longmaxi formation are quartz, clay and plagioclase, and the clay is mainly composed of Illite and Illite. The shale pores of Longmaxi formation in the study area are dominated by matrix pores, and the contribution of different mineral components to the shale pores is different, in which the pore volume per unit mass of organic matter is the largest, the clay mineral is the second, and the brittle mineral is the least. The shale pore size of Longmaxi formation is relatively stable, the average total pore volume of shale is 0.0081 cm 3 / g; the average specific surface area is 1.58 mm2 / g; the dominant pore size of shale mesoporous is 225 nm; the dominant pore size of micropore is 0.30.9nm. The shale pores of Longmaxi formation accord with fractal law and have self-similarity. The macropore structure is more complex than mesoporous pore and micropore structure. The shale bedding of Maxi formation is developed in south Sichuan. The initial porosity of shale in parallel direction is higher than that in vertical direction, and the initial porosity provided by shale unit density bedding is about 0.14. With the increase of buried depth, the effect of bedding on shale porosity decreases gradually. When the buried depth is large enough (3000m), shale porosity is mainly provided by matrix porosity. The initial permeability in parallel bedding direction of Longmaxi formation is generally higher than that in vertical bedding direction, and the shale permeability decreases with the increase of effective stress. According to the stress sensitivity, the change of permeability can be divided into sensitive areas. Transition zone and insensitive region are three stages. The pore volume decreases with the increase of pressure. With the increase of buried depth, the adsorption gas content of shale increases first and then decreases, but the shallower shale reservoir is easy to lead to the surface of the ground in the actual formation, forming an escape channel and low gas content. The content of shale free gas increases first and then steadily with the increase of buried depth, and the higher the reservoir pressure coefficient, the greater the content of free gas, and the total gas content of shale increases firstly and then decreases gradually with the increase of buried depth. The higher the reservoir pressure coefficient, the larger the total gas content and the smaller the decreasing rate. When the buried depth is shallow, the adsorption gas dominates the shale gas, and the free gas dominates when the buried depth is larger. The greater the reservoir pressure coefficient, the shallower the critical depth dominated by shale free gas.
【學位授予單位】：中國礦業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：P618.13
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