Research On Sedimentary Facies And Reservoir Of Chang 2 Formation In Yu Jiaping Area

Yu Jiaping is located in the middle east of the Shanbei slope of Ordos basin, is subjection to Zichang oil field of Yanchang group corporation. In recent years, with the decrease of new blocks and the high exploition of good reservoir of old blocks, the remained oil layer are characteristiced with bad physical property and thin sand. For the prolong of exploition and long-term stable production, the study of sedimentary facies and reservoir evaluation of slight oil layer is put on the agenda.Basised on the research of previous and the data of exploration, with the guidance of basic theory and methods of sedimentology, combining with the analysis of tectostratigraphic, geophysics, stratigraphy, reservoir sedimentology, oil geology, the formation is divided and compared, analysising the sedimentation volume and types of sedimentary facies in the study area, recovering the sedimentary facies and distribution rule of sand body, based on which the pore structure, diagenesis, physical property are studied deeply, summarizing the classification of reservoir of the aim formation.Combining with the analysis of core and well log,the development characteristic of depositional system of Chang 2 formation in Ordos basin, making the conclusion that the sedimentary facies in the study area is mainly braided river, the distributions of channel sand bodies are controlled by sedimentary facies, present a band sharp of northeast-southwest trend, the distribution of flood plain present moniliform.By the analysis of sorts of test data, the conclusion followed are maked, the sandstone types of Chang21 and Chang22 are both feldspar-porphyry sandstone, the grain grade is mainly middle-under size, the compositional maturity is low, the separation is good, the degree of roundness is mainly subangularity, the texture maturity is high-middle. The pore type are mainly remains intergranular pore and corrosion intergranular pore and, the corrosion intragranular pore and moldic pore are little. The distribution of pore throat is mainly wide-middle pore throat which has poor separation.The aim formation of the study area undergone four periods of epidiagenetic stage, early diagenic A, early diagenic B and middle diagenic A, the diagenesis are mainly compaction, cementation and dissolution, the metasomasis is visible accidentally, the compaction and cementation are the main reasons of lose of pore, the average percentage of porelosing they make are 23.8 ranged from 14 to 26 and 9.1 ranged from 6 to 14. In the cement, the clay mineral and carbonate cement mainly result the physical property became worse. The dissolution is the main reason which make the physical property became better, especially entering the middle diagenetic stage.Basised on the above analysis, this study is mainly depend on the physical property which get from the well logging interpretation, referring to the outcome of predecessors, the Chang22 reservoir is divided into four types:I a,â…¡a,II b andâ…¢a, in which the II a,â…¡b andâ…¢a are the main types; the Chang21 reservoir is divided into four types:I b,â…¡a,â…¡b andâ…¢a, in which theâ…¡a,â…¡b andâ…¢a are the main types.