A Study On The Diagenesis Of Paleogene System Based On Sequence Framework In DongYing Sag

On the guidance of the theories of sequence stratigraphy, diagenesis and geochemistry,and by reference to previous research, the systemic diagenetic studies based on sequencestrata are carried out in Dongying Sag, a representative of continental fault basins, by takingthe self-similarity of sequence strata, sequence--controlling sand and sequence diagenesis inepisodic sedimentation as the base for reservoir study's macroforecast and micro description.The obtained main conclusions and views are as follows:.1. Different sequence's formation has different variables such as tectonic subsidence,geologic climate, deposit source and base level fluctuation. These variables define theoriginal sedimentary diagenesis environment and diagenetic dynamic conditions byinfluencing the diagenetic parameters such as original components of clastic rocks, originalwater medium conditions and early pore water's components. According to the method ofgeochemical environmental analysis, the original sedimentary diagenesis environment'srebuilding by calculation shows that the property of sedimentary diagenesis medium with acharacteristic of growth and decline change in section has an important influence on theevolution of burial diagenesis.2. Paleogene System's ES4 and ES3x-S2x II sequence in Dongying Sag consist of fivediagenetic facieses and eight parfacieses. Its sandstone reservoir diagenesis stage can fall intoearly diagenesis stage A, B and middle diagenesis stage A, B. The distribution of dominantdiagenetic facies is diverse in sequence and along landscape orientation. Furthermore, thediagenesis near the boundary of sequence is ferrocarbonatite cementation predominatingly.3. Subject to syndeposit faults and sedimentary source, the diagenetic facies' styles insequence framework have major difference which totally shows the characteristic of sequencecontrol and facies control in different petrogenic zone of Dongying Sag. And the styles can bedivided into three sequence diagenetic facies configurations such as cliff fault slope model,sedimentary slope model and gentle slope model. In sequence diagenetic facies configuration,the occurring succession of parfacies depends on standard reaction's free energy that shouldmeet demands of diagenesis. Moreover, the regularity distribution of parfacies in sequenceframework results from fluidic heat convection in the Sag.4. The diagenetic evolutionary series and the sequence diagenetic integrated modelhave been built up in Dongying Sag. Also the diagenetic evolution's characteristic of thedifferent petrogenic zone and the sequence diagenetic route under different water media havebeen summarized.5. A study on the relationship between different diagenesis, diagenetic facies, abnormalpressure and reservoir property has been conducted. The value of diagenetic strength hasbeen quantified. Therefore, the diagenetic strength's distribution rules of different sequenceand the physical property's change disciplines have been summarized. Based on the aboveresearch, combined with evaluation criterion of reservoir property, the reservoir evaluationmethod and standard depending on diagenesis, which adapts to target strata, have been settledup. According to the method and standard, different sequence's reservoirs have beenevaluated, and its distribution rules have been summarized. Consequently, in verticaldirection, ES4s and ES3x sequence generally develop middle porosity, middle permeabilityor low porosity, low permeability reservoir. However, the reservoir with middle--highporosity, middle--high permeability generally occurred in the ES3z and ES3s- ES2x sequence.In horizontal direction, the gentle slope area is dominated by the high--quality reservoir withhigh porosity and permeability. The stiff slope area was a place for the better quality reservoirwith middle porosity and permeability. And bad quality reservoirs with lower porosity andpermeability occurred in the depressed area and the central uplift area.