Changes

Sandstone is the best known petroleum reservoir rock with an average porosity of about 15% and permeability of 25-100 Darcies which are mainly depend on the depositional environment, the character of the minerals forming the matrix and diagenesis. Diagenesis significantly reduces the porosity and permeability of sandstone reservoirs as illustrated in the case study below:

Sandstone is the best known petroleum reservoir rock with an average porosity of about 15% and permeability of 25-100 Darcies which are mainly depend on the depositional environment, the character of the minerals forming the matrix and diagenesis. Diagenesis significantly reduces the porosity and permeability of sandstone reservoirs as illustrated in the case study below:

A case study of reconstruction of the diagenesis of the fluvial-lacustrine deltaic sandstones and its influence on the reservoir quality evolution<ref>Luo Jinglan, Morad, S., Zhang Xiaoli, Yan Shike, Wufuli, Li Yuhong and Xue Junmin, 2002, Reconstruction of the Diagenesis of the Fluvial-Lacustrine deltaic Sandstones and its Influence on the Reservoir Quality Evolution. (7th edition), Vol 45. Science in China, pp. 615-634.</ref>

A case study of reconstruction of the diagenesis of the fluvial-lacustrine deltaic sandstones and its influence on the reservoir quality evolution<ref name=Jngln>Luo Jinglan, Morad, S., Zhang Xiaoli, Yan Shike, Wufuli, Li Yuhong and Xue Junmin, 2002, Reconstruction of the Diagenesis of the Fluvial-Lacustrine deltaic Sandstones and its Influence on the Reservoir Quality Evolution. (7th edition), Vol 45. Science in China, pp. 615-634.</ref>

===Location of study area===

===Location of study area===

===Stratigraphy===

===Stratigraphy===

[[File:Sandstone-Fig-10.png|thumb|300px|{{Figure number|Figure 10}}Typical stratigraphic section of the Lower-Middle Jurassic and Upper Triassic fluvio- deltaic facies showing general lithostratigraphy and sedimentary structures 1). 1, [[Oil shale]]; 2, trough [[cross-bedding]]; 3, tubular cross-bedding; 4, parallel bedding; 5, ripple cross-bedding; 6,contorted bedding; 7, [[conglomerate]]; 8, gravel sandstone;; 9, sandstone; 10, silt; 11, muddy sandstone; 12, muddy silt; 13, silty mudstone; 14, mudstone. (Modified after Luo Jinglan et al, 2002).]]

[[File:Sandstone-Fig-10.png|thumb|300px|{{Figure number|10}}Typical stratigraphic section of the Lower-Middle Jurassic and Upper Triassic fluvio-deltaic facies showing general lithostratigraphy and sedimentary structures. 1, [[Oil shale]]; 2, trough [[cross-bedding]]; 3, tubular cross-bedding; 4, parallel bedding; 5, ripple cross-bedding; 6,contorted bedding; 7, [[conglomerate]]; 8, gravel sandstone;; 9, sandstone; 10, silt; 11, muddy sandstone; 12, muddy silt; 13, silty mudstone; 14, mudstone. (Modified after Luo Jinglan<ref name=Jngl/>.]]

The Yanchang Formation of the Upper Triassic is a suit of terrestrial fluivolacustrine-deltaic sequence, consisting one of the main hydrocarbon-producing intervals in the area. The Upper Triassic Yanchang Formation can be divided into three facies from the bottom to the top ([[:File:Sandstone-Fig-10.png|Figure 10]]).

The Yanchang Formation of the Upper Triassic is a suit of terrestrial fluivolacustrine-deltaic sequence, consisting one of the main hydrocarbon-producing intervals in the area. The Upper Triassic Yanchang Formation can be divided into three facies from the bottom to the top ([[:File:Sandstone-Fig-10.png|Figure 10]]).