Preparation And Properties Of Polyvinyl Alcohol Products Used In Pipeline Blocking

With the increasing depletion of global land oil and gas resources,the exploration and development of deep-sea oil and gas resources is the development trend of the world’s offshore oil and gas industry.As the pipeline connecting subsea wellhead,PLEM and PLET in semi submersible subsea production system,the use of spool & jumper pipeline is increasing in deep-sea oil and gas fields.In order to avoid the formation of flammable ice blockage in natural gas hydrate under high pressure and low temperature environment in the deep sea,it is an effective way to use MEG gel to inject the pipeline in advance.The MEG gel injection technology for deep sea spool & jumper pipeline is currently monopolized by European and American oil companies as the core technology of deep sea oil operation.In this paper,the preparation and properties of polyvinyl alcohol(PVA)based MEG gel and welding argon-filled protective plugging materials which can be used for subsea pipeline application are studied.The specific research content is as follows:(1)The preparation and properties of PVA gel was investigated.Ubbelohde viscometer was used to determine the intrinsic viscosity and the viscosity average molecular weight of PVA.The viscosity of PVA solution and gel was measured by rotatory viscometer.The optimal dosage of PVA,p H regulator and organoboron crosslinker was studied by the single factor method.The performance of the gel was tested by the contact angle tester,DSC,TGA and other testing instruments.The optimum proportion for PVA gel is: PVA2488(8 wt%),defoamer(0.5 wt%),water(74 wt%),p H regulator(1 wt%),glyoxal(3 wt%)and organoboron crosslinker(13 wt%).(2)The preparation and properties of PVA elastomer was investigated.The PVA resin was plasticized with glycerol as plasticizer.The water solubility of PVA elastomer was measured at room temperature in water and artificial seawater,respectively.The performance of the PVA elastomer were measured by the contact angle measurement,automatic tablet machine,temperature and humidity tester,hardness meter,TGA,XRD,DSC,electron tensile testing machine,and rheometer.The optimum proportion for PVA elastomer is as follows: The weight ratio of PVA : glycerol is 3:22.The mixture was heated for 3.5 h at 130 ℃ and then solidified for 2 h at room temperature.(3)A kind of water-soluble sealing material with better gas barrier property for argon filling in pipeline welding was prepared.The effects of water soluble polymer concentration on the hydrophilicity,compactness,flame retardancy and water solubility of the sealing materials were studied.The results show that when the concentration of water-soluble polymer is 14 wt%,the sealing material is hydrophilic and the compactness is the best.The flame retardancy and water solubility of the anti burn through film were studied.The results show that when the amount of flame retardant reaches 12 wt%,the anti burn through film can withstand the damage of welding slag at 519 ℃ for 180 s.The film can also be completely dissolved in 5 ℃ water after 3 hours.Relevant technical process have been adopted by China Offshore Oil Engineering limited company(CNOOC)and(HUSKY)as the owner and successfully applied in the welding of PLET “gold welded junction” in Liuhua subsea projects in South China Sea,solving the welding technical problems for the installation of composite pipeline on the side of “Offshore Oil 201” deep water pipe-laying vessel.