Microscopic Characteristics And Its Effect On The Reservoir Of The Authigenic Kaolinite Of The Eighth Member Of Shihezi Formation In The Zhao 30 Wellblock Of The Northeastern Section Of The Surig Gas Field

Zhao 30 wellblock in Ordos Basin is located in the eastern part of the Surig gas field. In this area, the the Eighth Member of lower Shihezi Formation is the important gas productive reservoir in Sulige gas field.The clastic rocks of investigative area is mainly tight reservoir with low porosity and permeability, high compositional maturity and so on. By adopting a series of means including a lot of rock slice, cathodoluminescence and scanning electron microscopy(SEM), X-ray diffraction analysis of clay mineral and physical property, this thesis has a deep research on the Eighth Member of Shihezi Formation in the petrology characteristics, diagenesis, poroperm characteristics, pore types, diagenesis evolution characteristics. On the basis of above,the paper do the research to state of authigenic kaolinite in the area, distribution characteristics, formation mechanism and its influence on reservoir. We draw the following conclusion:1.In the area of Zhao 30 wellblock in Sulige gas field, the Eighth Member reservoir sandstone of authigenic kaolinite has the content to an average of 2.55%, its content presents the increasing trend from the upper Shihezi Formation to lower Shihezi Formation, and shows a significant negative correlation with feldspar content, the correlation coefficient is R2 = 0.1046.2. In the types of the Eighth Member reservoir sandstone, secondary porosity accounted for 80% of the total porosity and the primary pore is only 20%. Among them, the lithic dissolved hole is more, the second is intergranular pore and intergranular pore and mixed base solution pores, and a small amount of feldspar dissolution pore, intergranular dissolved pore and micro cracks, of which the intergranular pore is given priority to with authigenic kaolinite intercrystal pore.3. The Eighth Member reservoir in Zhao 30 wellblock state of authigenic kaolinite mainly has the following kinds:(1) Fill with the secondary porosity produced by feldspar skeleton particles dissolution;(2) Fill between primary intergranular pores and residual intergranular pore;(3) Fill in the above kinds of pores with authigenic quartz, illite, chlorite and other authigenic mineral. The fringe of authigenic quartz particles formed the shape of a jagged rim or harbor.4. In the study area, the distribution between authigenic kaolinite and feldspar has obvious negative correlation, which illustrates the authigenic kaolinite in the study area is mainly composed of feldspar dissolution, and the necessary Al3+ in authigenic kaolinite is derived from feldspar dissolution of aluminum silicate.5. Through the data analysis and statistical properties to the Eighth Member reservoir in Zhao 30 wellblock, it is concluded that the reservoir porosity is 8.83% on average, the average permeability is 0.67×10-3?m2, the physical property of overall reservoir is bad, which shows " low permeability”. There is a good correlation between porosity and permeability, the correlation coefficient is R2 = 0.5525.6. Although the formation of authigenic kaolinite in the the Eighth Member reservoir in Zhao 30 wellblock occupied part of sandstone reservoir space, but its formation has brought a lot of secondary pore. In general, the Surig gas field Zhao 30 wellblock,the authigenic kaolinite is conducive to the formation of reservoir physical properties.