酒泉盆地酒东坳陷下白垩统储层特征及有利勘探方向研究

Jiuquan basin, located in the middle of the Hexizoulang, is one of the major important Mesozoic、cenozoic oil-gas bearing basin in the west of China. Jiuquan basin is composed of Jiuxi depression、Huahai-jinta depression and Jiudong depression. Basement of Jiudong depression is Silurian shallow metamorphic rock. Ying-er sag , focus of this study, is the biggest sag in Jiudong depression and the targeting study object is cretacic strata. Structure evolution and geological background were carefully studied in this research. A series of methods were applied to this research: values of oxygen and carbon isotope and trace elements analysis were used to recover salinity of the palae-lake water of the sag. The evolution and distribution of sedimentary faces were carefully studied. Also, various analysis and tests were made to study the diagenesis of the reservoir sandstones、porosity evolution and porosity distribution. All the studies indicate that sedimentary faces are main macroscopic factor controlling the reservoir quality; Compaction is the main factor destroying reservoir property. Carbonate cements greatly preserved the porosity in eodiagenesis because it had prevented significant early mechanical compaction and its dissolution in the late diagenesis generated secondary pores. Carbonate cements in the late diagenesis occluded primary porosity and played a negative role in the porosity preservation. Source of the carbonate cements were also preliminarily discussed. Feldspar grains and lithic fragments were dissolved by acid fluid and formed a great amount of secondary pores and developed the reservoir quality. Also, sedimentary-diagenesis zones were identified. On basis of these studies, Reservoir forming factors were studied. Keywords: Jiudong depression, sedimentary faces，reservoirs diagenesis reservoir evaluation，secondary pores