Research And Application Of Fault Sealing Quantitative Evaluation Technique

Fault sealing is one of the important factors to develop structure reservoir.It has attracted increasing interest to do quantitative evaluation research on fault sealing ability through specific formula.However,it is difficult evaluate the fault sealing ability in areas with no well information.Based on extensive literature and researching,we proposed that the mechanism of fault sealing is caused by the difference in permeability between faults and the surrounding stratum lithology.There are four reasons that will cause fault sealing:(1)Juxtaposition,the juxtaposition of the sandstone reservoir and the formation unit with high displacement pressure(such as shale);(2)Smear,which is,the continuous and low permeable fault mudstone zone caused by mudstone’s moving into fault zone after its deformation;(3)Cataclasm,the broken and friction of sandstones cause the reducing of grain size and porosity,which lead to the increasing of capillary displacement pressure of fault zones;(4)Diagenism,fault rocks are affected by mudstone content,buried depth/temperature condition and other factors.It will partly or entirely generate cementation and pressolution in quartz along the fault plane,which makes a contribution to liquid sealing.The premise condition of quantitative evaluation of the lateral sealing capacity of faults is to make top and foot wall lithology juxtaposition in the fault surface.This paper is based on 3D modeling to constract the fault plane and formation plane.Besides,it used Delaunay triangle surface subdivision to perform surface gridding.Then,it makes the fault plane and the formation plane intersect precisely.Afterward,we can input lithology data to make the lithology juxtaposition,and figure out lithology juxtaposition ability qualitatively.Furthermore,we can map out the fault SSF seal index,and evaluate fault sealing ability quantitatively through calculating Clay Smear Potential(CSP),Shale Gouge Ratio(SGR),and Shale Smear Factor(SSF).Finally,we will make a comprehensive evaluation to fault sealing ability through both qualitative and quantitative evaluation.