| Tight sandstone gas reservoir in Tuha oil field has the characteristic of low permeability,small pore throat,high capillary pressure,and strong water lock damage;high clay ratio,strong water sensitivity and clay expansion as well.Some well even got a negative effect in the previous stimulation treatment as a reason of the water lock effect and water sensitivity by normal water base treatment fluid.So treatment fluid needs to be anti-water lock and anti-water sensitivity except for normal requirements in order to protect the formation on this type of reservoir.At the same time,as a reason of low gas contents,high anisotropy,treatment on vertical well cannot get to a result good enough.The author confirmed the critical damage mechanism and potential damage of reservoir by researching the reservoir character of Tuha sandstone tight gas formation.Research on anti-damage and water lock method and comparisons on several anti-water lock agents have been done so as to find an appropriate anti-water lock method for Tuha tight sandstone gas.Based on this,anti-water lock fracture fluid and acidizing fluid have been developed.Based on core analysis,HCOOH and other additives ratio has been optimized.Multihydra acid +alcohol acidizing system has been invented,and the concentration for different acid type has been recommended.Fracture initiating model has been founded based on horizontal wellbore stress distribution rule and rock damage principle.Fracture initiating and generating principle have been confirmed.Effects on horizontal well post treatment production by stages,stage gap,well survey and fracture angle,fracture placement,length,etc.New techniques on open hole stage frac.and abrasive perforation stage frac.in recent years have been researched and stated in this issue.24 wells success have been made based on this paper in Tuha oilfied.Researches in this study have improve the subsection fracturing technique on tight sandstone gas to a new level. |
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