Rearch In Reservoir Characteristic And Reservoir Sensitivity Of The Member8in Zhao30Wellblock, Ordos Basin

Zhao30wellblock in Ordos Basin is located in the eastern part of the Sulige gasfield, and it is the potential exploration areas, especially the member8of lowerShihezi formation is the important gas productive reservoir in Sulige gas field. Theclastic rocks of investigative area is mainly tight reservoir with low porosity andpermeability, high compositional maturity, strong anisotropism and so on. Therefore,The thesis is guided by sedimentology, reservoir mineralogy, reservoir geology andpetroleum geology, combined with a large number of casting lamella,cathodoluminescence, scan electron microscope and X-ray diffractions of clayminerals, the experimental data of physical property, porosimetry analysis and so on，systematically researched the lithological characteristics, physical characteristics, theevolution of diagenesis, pore structure types and characteristics of the member8inzhao30wellblock. But beyond that, we put forward a series of protection measure ofthe reservoir on the basis of evaluation and analysis on reservoir sensitivityexperiments. Through the study of sedimentary facies, characteristics, diagenesis andsensitivity of reservoir of the member8in Zhao30wellblock, we can draw thefollowing conclusions:The member8formation in Zhao30wellblock developed mainly alluvial plaindepositional system which had a banding distribution along the north-south direction.The upper member8formation developed mainly the phase of meandering river,and the effective sand bodies had developed in point bar with good physical character.Their distribution on the plane is beaded, and their extension of the scope is a small,and the shape of sand bodies is convex lenticular in profiles. Thickness of the sandbodies is small, and transverse connectivity is poor; The lower member8formationdeveloped mainly the phase of braided river, and the effective sand bodies had developed in diara. Their distribution on the plane is sheet Multistage contraposedphenomenon of diara increases continuity and connectivity of the effective sandbodies.The lithological characteristics of reservoir indicate: The layer rock is mainlylithic sandstone, the lithic quartz sandstone and less quartz sandstone. Detritalcomponents include mainly quartz and lithic, but feldspar content is extremely low, soit can show high compositional maturity of sandstone. Interstitial material includesmainly mudstone matrix and kaolinite, chlorite, calcite, ferriferous calcite andsiliceous. Chlorite thin film and tuffaceous are distributed in a few wells.The pore types of the member8reservoir in Zhao30wellblock iclude mainlyresidual original intergranular pore, intergranular dissolved pore, intragranulardissolved pores and microcracks. As a whole, the pore connectivity of the member8reservoir in Zhao30wellblock is poor, and it is tiny pore throat based. Reservoirproperties is relatively poor, and there are significant positive correlations between theporosity and permeability.Dissolution and fracturing of the member8reservoir in Zhao30wellblock arethe main constructive diagenesis, and compaction, pressure solution, cementation andmetasomatic alteration are the main destructive diageneses. Diagenetic evolution canbe divided into stage A and stage B of early diagenesis phase, stage A and stage B ofmiddle diagenesis phase and late diagenetic phase. Research has entered the reservoirinterval of diagenetic B, partially to late diagenesis.Investigative area had enteredinto stage B of middle diagenesis phase, and most had entered into late diageneticphase.Reservoir sensitivity analysis by experimental data show that, the sensitivity ofthe member8reservoir in Zhao30wellblock overall was medium to strong–stronglevel: the reservoir has medium velocity sensitivity, strong–superstrong watersensitivity, strong–superstrong stress sensibility. The degree of water sensitivity andvelocity sensitivity builds on content and distributed state of chlorite and illite. Andstress sensibility except that it is related to rigid quartz particles and cementitious way,and it is related to pore structure of reservoir. The throat types of the member8reservoir in Zhao30wellblock are mainly lamellar, and when the effective stress offormation had changed, lamellar throat would easily be compressed. Therefore, it alsodetermines stress sensitivity of the study area on the strong side.