Diagenetic characteristics and quantitative porosity estimation of tight sandstone reservoirs：a case from the 8<sup>th</sup>Member of Permian Xiashihezi Formation in the Gaoqiao region, Ordos Basin

Zhang Xingliang; Tian Jingchun; Wang Feng; Chen Rong; Zhang Jinquan

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Diagenetic characteristics and quantitative porosity estimation of tight sandstone reservoirs：a case from the 8^thMember of Permian Xiashihezi Formation in the Gaoqiao region, Ordos Basin
Vol. 35, Issue 2, Pages: 212-217(2014)
Online First：08 April 2014，

Published：2014
DOI：
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DOI：

Zhang Xingliang, Tian Jingchun, Wang Feng, et al. Diagenetic characteristics and quantitative porosity estimation of tight sandstone reservoirs：a case from the 8^thMember of Permian Xiashihezi Formation in the Gaoqiao region, Ordos Basin[J]. 2014, 35(2): 212-217. DOI：

摘要

运用铸体薄片鉴定、扫描电镜、X-衍射等测试方法，系统研究了鄂尔多斯盆地高桥地区二叠系盒8段储集砂岩的成岩作用类型及其对储层的控制作用。研究区致密砂岩储层沉积后经历了复杂的成岩作用，压实作用导致原生粒间孔大量丧失，胶结作用在降低原生粒间孔的同时增加了骨架颗粒的强度，有利于残余原生粒间孔的保存，交代作用表现为高岭石交代长石以及铁方解石交代石英碎屑，溶蚀作用使砂岩中不稳定的碎屑颗粒及胶结物溶解，改善砂岩储层的储集性，破裂作用形成微裂缝。通过对不同成岩作用在储集砂岩的孔隙生成和损失方面的定量评价研究后认为，压实作用使孔隙度减小最多，达22.40%~33.17%，平均降低27.166%；其次为胶结作用和交代作用，使孔隙度损失5.5%~17%，平均损失为10.01%；而溶蚀作用使孔隙度增加6.86%~8.41%，平均增加8.586%。正是上述多种成岩作用改造的最终造成了研究区致密砂岩储层的孔隙特征。

Abstract

Based on the thin section examination

SEM

X-ray diffraction

this paper studied the diagenetic types and their control on reservoirs in the 8

Member of Xiashihezi Formation(He8)tight sandstone in Gaoqiao region.The He8 reservoir has experienced complex diagenesis after deposition.Compaction resulted in the loss of primary intergranular pores.And cementation reduces the primary intergranular pores while increasing the strength of the skeleton particles

which is conducive to the preservation of residual primary intergranular pore.Replacement in the study area features in feldspar replacing kaolinite and iron calcite replacing quartzes debris.Dissolution improves the reservoir physical properties by dissolving the unstable detrital grains and cements.Fracturing causes the formation of micro-fractures.Quantitative evaluation of the increase and decrease of the porosity caused by different diagenesis reveals that compaction is the most significant in porosity reduction

being about 22.40%-33.17%

with an average of 27.166%

followed by cementation and replacement

bing about 5.5%-17%

with an average of 10.01%.In contrast

dissolution increases porosity about 6.86%-8.41%

with an ave-rage of 8.586%.The porosity of the tight sandstone is the final result of the different diagenesis.