A New Sludge Shale Low Temperature Slow Acidification System

Acidification is an effective method of increasing well production and stimulation of injection well. acidizing is an improtant technology for well broken down and stimulation in the mud shale reservior. Because of the high content of clay mineral in the mud shale formation, the reaction of mud acid system and hydrosialite is over fast, which cause acid fluid short distance penetration and lowly acidification efficiency, also can not efficiently inhibit the expansion and migration of clay, at the same time, generating secondary precipitation.By introducing the Additive PSA-2 to acidizing fluid,using the effective ionogen P-O-C band in the molecular structure,P can chelate much H,and H can become H+in certain circumstances,and H+releasing by multistage, so which can effectively extend the active acid s duration of action.The study of a new pattern of low-temperature retarded acid system specifically for mud shale formation, which not only can improve the performance of retarding but also can inhibit the clay swelling or migration,and will not cause secondary damage to the reservoir.PSA-2 is synthesised by the polymerization between home-made monomer SA-1 and diallyldimethylammonium chloride (DMDAAC).Optimal conditions of the polymerization are:the mass ratio of SA-1 and DMDAAC is 5:4, initiator H202 dosage is 2.5%,the polymeric temperature is 85℃, the polymeric time is 2h.After purified,infrared analysis for PSA-2,the product is consistent with the expected product.The proformance of retarded dissolution,including retarded acid on mud shale, marble and caly,which all be better than mud acid system.The antiswelling rate of the retarded acid system can get to more than 90%, which can aviod the secondary damage caused by the clay swelling and migration.The acid system also has good corrosion inhibition effect, the corrision inhibituin rate of the retarded acid sysytem on N80 steel can get 96.4%.By microscope analysis for mud shale core,we got that the retarded acid system can effectively spread reservoir pore,increasing acid etching distance,effectively inhibiting clay swelling and migration and no secondary damage for the formation.Especially at 50℃, the effect is well,construction time can get 4h;at 70℃,dissolution for 2h,no precipitation produced,indicating that the mud shale low-temperature retarded acid system has definite performance of anti-temperature.