Study On Reservoir Characteristics And Damage Mechanism Of The Kepingtage Formation Of The Silurian In The 12 Well Area Of ??Tazhong

With the improvement of the exploration and development technology,more and more low permeability oil resources was found and mining.Deepen the understanding of low permeability reservoir's geological characteristics,for further exploration and development of this kind of reservoir is of great significance.With the characteristics of poor physical properties and sensitivity mineral enrichment,the low permeability oil reservoir is vulnerable to damage in each link of development work,which lead to the low yield or no production for oil wells.So the research of reservoir's damage mechanism and protection measures paly an important role in the development of low permeability oil reservoirs.In this paper,the object of study is the Silurian kepingtage group low permeability reservoir in TZ 12 wellblock.On the basis of in-depth analysis of reservoir's characteristics,the research analyzes the potential damage factor of reservoir and the main damage type and mechanism of reservoir in which the process of drilling and fracturing,while put forward the corresponding protection suggestions.The understanding and the conclusions are as follows:(1)the main oil resevoir of TZ 12 wellblock's Sulirian formation is the up 3 submember of kepingtage group that sedimentary facies is tidal flat facies and that lithologic character are medium-grained to fine-grained lithic sandstone;interstitial material are clay mineral and carbonate cement;the average content of clay mineral(X-ray diffraction)is 6.32%that main is kaolinite and that following are ilite and ilite/montmorillonite mixed-layer mineral;the reservoir's average porosity is 11.81%and average permeability is 18.22×10-3?m,which belongs to low porosity an permeability reservoir.(2)Through the sensitivity experiment evaluation concluded that the reservoir exists medium to high speed sensitivity damage and the critical flow rate is 1.0 ml/min,that weak-medium weak water/salt sensitivity and the critical salinity is 30000 mg/L,that no-weak alkali sensitivity damage and critical pH value is 8.(3)Under the condition of underbalanced drilling,the use of oil-base drilling fluid system currently has good protecting effect to the reservoir whose damage type is solid phase jammed,oil-water emulsify,wettability reversal and stress sensitivity.(4)Through dynamic experiments evaluation concluded that xanthan gum fracturing fluid system will cause medium to strong-strong damage just coming into the reservoir,that will reduce damage degree to reservoir and achieve good effect on reservoir protection which due to the natural degradation of polymer polymer in the later fracturing period.The damage mechanism to reservoir's matrix by this system is that high polymer adsorption/retention plugging in reservoir seepage channels,jamin effect produced by the oil/water emulsion,etc.The damage mechanism to fracture is that concentrated residue,polymers,such as broken proppant plug cracks and seam face after fracturing fluid gel breaking;Filter cake in the late fracturing,aggravate the fracture stress sensitivity damage.(5)Through the research of TZ 12wellblock's Silurian kepingtage group reservoir,formed damage mechanism and protection technology research methods in the drilling and reservoir reconstruction operation,while it in the low permeability reservoir characteristics.This research has the reference significance for similar oil field reservoir protection technology application.