Clastic reservoirs characteristics and its control of Mesozoic in Jiyang depression

On the basis of core observation, thin section arbitration, scanning electron microscope and X-diffraction analysis, the reservoir characteristics and control factors of clastic reservoir of Mesozoic in Jiyang depression were researched. The reservoir sandbodies of alluvial fan, fan delta, fluvial and delta were developed. The clastic reservoirs mainly went through strong compaction and pressure solution, cementation, metasomasis and dissolution. The analysis results of reservoir characteristics and its control factors of clastic reservoirs show that solution pores and fractures are main reservoir spaces, and sedimentation, tectonization and diagenesis control the porosity and permeability of clastic reservoirs. Sedimentation is the most important control factor, among other things, the porosity and permeability of delta sandbody are the highest, of the fluvial sandbody take second place, and of the alluvial fan, fan delta and shore-shallow lake are poor. The influence of tectonization on clastic reservoirs properties includes the fault activities and unconformities. Many fractures are formed because of fault moving, and the porosity and permeability of reservoirs locating about 100 m under unconformity interfaces increase obviously. Dissolution is controlled by both sedimentation and tectonization, and the converted degree on reservoirs is closely related to sedimentary facies and the distance from unconformity interfaces. Comprehensively considering the control of sedimentation, tectonization and diagenesis on reservoirs, the clastic reservoirs are divided into four categories, of which, type I is high porosity and medium permeability reservoir, type II₁ and II₂ are medium porosity and low permeability reservoir, type II₃ is low porosity and permeability reservoir, and type HI and IV are the lowest porosity and permeability reservoir.