Study On High Temperature Plugging Agent Suitable For Sudan Unity Oilfield

There are mainly low-permeability reservoir block-based multi-storey complex of 90~120℃high temperature in Sudan UNITY oilfield. There are lots of complex block-based reservoir in JiangHan oilfield and ShengLi oilfield and any other oilfield, for example, in Ma25 of JiangHan oilfield and ShengLi oilfield. This high-temperature water shutoff agent has reference affection to high-temperature reservoir of our country oilfield.The paper mainly studies the synthesis of new high-temperature water shutoff agent, investigates different factors of effecting the course of reaction, evaluates systematacially gelatin properties of high-temperature water shutoff agent, tests core blocking rate in different permeability. Reading a lot of papers and experiments, we define sulfonated tannin as the main agent, polyformaldehyde as the cross-linking agent, urea as the thickening agent, hydroquinone as stabilizer. from the mechanism, we analyse course of reaction of the high-temperature water shutoff system and present new water shutoff system, which is viscosity-tough-tough high-temperature water shutoff system. We get the affection law of every component and external environment to water shutoff gelation time and gel intensity after gelation. Finally, we get the typical formula for the blocking agent: HPAM500mg/L, sulfonated tannin 50000mg/L, hydroquinone 5000mg/L, urea 4000mg/L, polyformaldehyde 4000 ~10000mg/L, a adjustable plastic time 3~92h.We evaluate quantitatively the gel intensity of high-temperature water shutoff system using the breakthrough vacuum degree method. We analyse systematacially the affection of the addition of every component, the pH value and mineralization to the high-temperation water shutoff system and investigate the affection of the adding urea to breakthrough vacuum degree after the system gelation. The breakthrough vacuum gelation is about 80KPa, and it has favourable water shutoff intensity.When the concentration of NaCl is 4000mg/L, the breakthrough cacuum degree of the high-temperature water shutoff system can still get to 31KPa. When the concentration of CaCl2 is 4000mg/L, the breakthrough cacuum degree of the high-temperature water shutoff system can still get to 29KPa, and it has perferable salt-persisting property. Therefore, the developed high-temperature water shutoff system is suitable for high mineralization degree reservoir.The experimental results showed that: the blocking system has a good thermal stability. We didn't see serious dehydration in the 120℃after15 days. The dehydration rate is lower than 6%. We scan the stress after the gelation of high-temperature water shutoff agent using TA-AR2000ex rheometre appratus. In 1Hz, storage modulus G'is higher than 50KPa, loss modulus G''is lower than 10KPa, G'﹥G'', which illustrates that the gel is powerful gel , and the gel has good viscoelasticity and shear-resisting ability. The blocking rate to the core with different permeability is higher than 98%. The initial viscosity is lower than 100mPa.s.The gelation viscosity is higher than 5000mPa.s. It has good pump ability. The integrated performance can meet operational requirements of the water shutoff of the complex high-temperature reservoir.