The Synthesis And Characterization Of Non-invasive Drilling Fluid Additive

Non-invasive drilling fluid is a new kind of drilling fluid which is concerned both in and abroad, and it is usually made of ordinary drilling fluid by adding non-invasive drilling fluid additive. "non-invasive" means there is no liquid or solid to invade into or harm the well. Non-invasive drilling fluid additive could stabilize sandstone and shale, reduce the thickness of mud cake by reducing infiltration, and then the efficiency and possibility of success in drilling well. And it can also reduce the pollution to the terrane by mud to protect the oil and gas formation.In this paper, cellulose and waste rubber powder are modified by grafting to became non-invasive drilling fluid additive.Initiated by cerium sulfate and potassium persulfate, acrylic acid and acrylamide can graft onto the surface of cellulose. The feasibility of the modification and the results are discussed. The FTIR and standard API test are used to characterize the grafted polymer. The results show that both of the two initiators can initiate the grafting reaction, but initiated by potassium is much better. The modified cellulose initiated by potassium has a very good non-invasive performance. Through standard API test, under the same conditions, the filtration loss of the product(4.5ml) is less than that of FLC2000(11.0ml). When it comes to 120℃in the same test, its filtration loss(9.0ml) is also less than that of FLC2000(26ml).The abundance double bond inside rubber powder provide a new idea—graft to the rubber powder to prepare a new functional material. By emulsion method, the acryacid etc. can be grafted onto the rubber powder. similar to modified cellulose,It can avoid water inside the mud to penetrate into stratum, so it can protect the oil well and the oil and gas formation. Through Wijs method the feasibility of this experiment is investigated. The pretreatment of waste rubber powder is very important. It must be pretreat by acetone,NaOH solution and HCl solution. The grafted waste rubber powder was characterized by FTIR and SEM. The results show that acrylic acid and acrylamide could be grafted onto rubber powder. And the effection of time, temperature and initiator are discussed. The optimum conditions for this system are like this : reaction time: 4 hours; reaction temperature: 65℃;initiator concentration: 2.5%; Then the grafting ratio is 40%.Through API test, the results show that its property as low permeability additive is excellent. It could greatly prevent the fluid invasion, even better than the same kind of product FLC2000 purchased from USA. Through standard API test, under the same conditions, the filtration loss of the product(20 ml) is less than that of FLC2000(36ml). Through TGA test,it is shown that its stabilization under usage condition is good. The thermal loss is limited from room temperature to 120℃, during this temperature period its thermal stabilization is good.