Research On The Heterogeneity Of Chang 8 Reservoir In Heshui Area Of Xifeng Oil Field

Research on the reservoir heterogeneity is very important in the fundamental work of oilfield prospecting and development geology, especially in the condition that many oilfields have already taken the low-porosity and low-permeability, even extra low-porosity and low-permeability reservoir as the main territory of oilfield prospecting and development in China.Aiming at the regional geologic background, deposition condition and diagenesis, using the strata correlation method, high-resolution sequence stratigraphy and conterminous wells correlation, Chang8 reservoir is layered into six sublayers. Additionally, under the theoretic guidance of petroleum geology, reservoir geology, reservoir and physics well log, by means of many laboratory analysis methods and data, sedimentatal microfacies, diagenesis, microstructure and fluid flowing characteristics is in depth study, and the two main factor, sedimentation and diagenesis, which influencs reservoir heterogeneity are clarified.The reservoir heterogeneity of six sublayers in study area are clarified in both macroscopic and microscopic respect. In the research on the reservoir macroscopic heterogeneity, aggregative index is inducted, and fuzzy cluster analysis is used; In the research on the reservoir microscopic heterogeneity, the advanced experimental method, such as water driving experiment and rate-controlled Hg penetration is adopted.The main conclusions are in the following:1. Chang8 reservoir is layered into six sublayers:Chang8₁¹,Chang8₁², Chang8₁³, Chang8_<sup>1, Chang8₂² and Chang8₂³.2. Base on core observation and grain size analysis, and under associated consideration of logging trace characteristics, Chang8 reservoir in study area is classified into three sedimentatal microfacies, subsea river, mouth bar and river flank.3.The mian diagenesis in study area are: mechanical compaction, cementation, metasomasis and denudation in late diagenetic phase.4. In allocation of reservoir macroscopic heterogeneity, more heterogeneticer reservoir, class 1 and class 2, mainly locate in the center of subsea river or crook and divaricate of the river; class 3 and class 4 mainly locate in river flank, and the physical property of these locality are better.5. Diagenesis of reservoir have influence on the pore structure which influences the reservoir microscopic heterogeneity. The better the pore structure is, the slighter the reservoir microscopic heterogeneity is; on the contrary, the reservoir microscopic heterogeneity is serious.