The Study Of Characteristics And Controlling Factors Of Low Permeability Reservoir Of He8 Section In Sulige Region

Under the guidance of the theories and technologies of Sedimentology, Reservoir Geology and Geochemistry, researches are carried out on several aspects such as diagenesis and micro-pore structure of He 8 Section reservoir in Sulige region. And then the controlling effects of sedimentary environment and diagenesis on reservoir distribution and reservoir physical property are explored. Based on the above researches, the rules of good reservoir distribution are settled up. The obtained main conclusions and views are as followed:1. According to the researches on sedimentary facies and sequence stratigraphy, the good reservoir distributes in favorable sedimentary microfacies such as braided channel and subaquatic braided channel. The combination factors of sedimentary facies and basal level cycles control the horizontal distribution and vertical evolution of the sandstone.2. The reservoir characteristics of He 8 Section in Sulige region suggest that its sedimentary facies is braided delta, which is near the sediment source. The reservoir lithology characteristics show low texture maturity and low compositional maturity, appearing as high debris content, middle-low particle classification, and angular particles. The cement types mainly are authigenic clay mineral and siliceous cement, sometimes ferrocalcite and tuffaceous cement and chlorite.3. The diagenesis types are compaction, cementation and denudation, with diagenesis history divided into three phases, and the diagenesis reaches middle diagenesis phase B period. According to clastic constituents, diagenesis mineral, interstitial matter and diagenesis type and pore evolution characteristics, He 8 Section of Sulige Region are divided into four diagenetic facies types and three types of diagenetic facies combination. With the analysis of the relationship between diagenetic facies and electrofacies, logging curves favorable for identifying diagenetic facies are summarized, which are SP, AC, DEN,combination of RLLS and RLLD. And their quantitative logging curves models are settled up.4. Both the sedimentation and diagenesis contribute to the forming of good reservoir, whereas diagenesis is the leading factor. Through the quantitative assessment of diagenetic intensity, the impacts of diagenesis on the reservoir physical property are analyzed thoroughly, reaching the result that intense compaction and cementation are the critical factors for low porosity and permeability, whereas denudation improves the physical property greatly.5. Based on the comprehensive reservoir evaluation of priority wells, in combination with the analysis of reservoir type, diagenesis and reservoir physical property, the He 8 reservoirs are divided into three types, that is type I, type II and type III. With the knowledge that the reservoir pore type mainly is secondary pore and its forming has close relationship with hydrocarbon injection, we draw the conclusion that the good reservoirs distribute in the favorable sedimentary facies, where is adjoined to oil source depression or is on the route of oil migration, such as braided channel and subaquatic braided channel.