Reservoir Protection Technology Applied During Drilling And Completions Of2th Member Of Shanxi Formation In150Area Of Yanchang Gas Field

’I"he low permeability sandstone oil formation has the common characteirstic with lowporosity, low permeability, rfacture exist, severe heterogeneity, which is very easy to bedamaged duirng dirlling and completions influencing the timely production and exactevaluation of oil formation. Theerfoer，the research of formation damage is of significance inthe drilling and completions of this reservoir.The specific object of ersearch is2th member of Shanxi Formation in150area ofYanchang Gas ifeld. By means of scanning electron microscope. X-ray diffraction? cast bodychip and intrusive mercury data analysis arc applied to study the reservoir characteirstics.Thereservoir lithologic property of2th member of Shanxi Formation is conglomeratic mid-coarsequartzose sandstone, the next is lithic sandstone and individual for arkosc sandstone. The typeof clay mineral is very different in different team.the content of illile is biggest and that ofChloirte, illite/smectite mixed layer mineral and kaolinite is bigger in2th member of ShanxiFormation. The average porosity of formation is6.02%, the average permeability is3x.8610’32jim, Maximum R50is rfom0.52lfim to2.824, the avearge R50is1.32^m. Medianpressure is rfom1.43MPa to139.55MPa, the average Median pressure is17.23MPa. Mediumthroat size is rfom0.054|im to0.144^m, the average is O.llfim, On the whole reservoir porethroat size is tiny, for low permeability and low porosity. The stress sensitivity of reservoir issevere.The mainly potential damage factors include solid invasion, water lock, sensitivitymineral, rfacture and so on. The result of sensitivity evaluation shows that the damage level ofvelocity sensitivity is weak to medium. The damage of water sensitivity and salt sensitivity istotally weak. The level of damage of alkaline sensitivity is zero to weak. There is weakdamage of acid sensiitvity. The stress sensitivity of reservoir is severe. Liquid entrap in narrowpore throat of reservoir is strong. The result of static damage expeirment of drilling lfuidshows the severe damage of additive and dirll-in lfuids in ifeld. In a word, the major damagemechanisms contain liquid entrap, sediment of solid grain, stress sensitivity and particlemigration as a result of invasion of solids and liquids.At last，the necessity of using shield temporary plugging technology is identified.Theresults of expeirments at home and performance of oil ifled prove that the piror dirlling fluids is characteirstic of strong seveirty of formation damage. The MMH dirll-in lfuid system isselected through temporary plugging laboratory experiment, so that the project of formationcontrol technique is brought forward. The Temporary Plugging dirlling lfuids can reduce theinvasion of solid particles and filtrates> increase production rate of gas and accelcrateappearance of high product well to some extent.