Study On Polymer Weak Gel For Deep Profile Control In Reservoir

With the development of oil production technology, depth portion profile control technology of weak gel obtained the obvious effects in enhancing oil recovery. Commonly used polyacrylamide weak gel would degrade in high temperature and precipitate under high salinity to lost effectiveness while applicated in some special conditions of reservoirs. Therefore, molecules structure design and optimization of polymer to develop its viscosity, heat resistance, salt resistance and shear resistance is becoming research hotspot in oilfield chemistry.Currently, even the preparation of crosslinked polymer of polyacrylamide improved deficiency of temperature and salt resistance, cross linking agents used such as formaldehyde, phenol or potassium dichromate, citric acid aluminum would pollute the environment. Therefore, a kind of new depth profile control material owned special properties and sources of environmental friendly need to be created to further improve salt and temperature resistance to expand the use scope. Natural polymer with multi-function can be modified to become the new material, besides,natural polymer are widely used in daily chemical, food additives, building materials and other fields. In recent years, modified natural polymer characterized with rigid structure and water solubility and high pseudoplastic, the application of in the oil field profile received the widespread attention.The main research of this article is based on research trend the above. Under the influence of initiator system(NH4)2S2O8—Na2SO3 and crosslinking agent(BIS), using CMC and XG as macromolecular monomer to copolymerize with acrylamide(AM) to prepare CMC/AM/BIS and XG/AM/BIS weak gel copolymer. Discusses the reagent dosage, reaction time and reaction temperature on the viscosity of gel system, the structure of the copolymer is verified by IR, TG test, the weak gel properties of salt resistance, temperature resistance, resistance to shear and breakthrough pressure gradient are tested and evaluated under simulate formation conditions, the main results are as follows:(1) The contrast analysis of nfrared spectrum of CMC with CMC/AM/BIS copolymer and contrast analysis of the trend of curve and weightlessness area of CMC/AM with CMC/AM/BIS copolymer, verified the crosslinked structure of CMC/AM/BIS copolymer. The contrast analysis of nfrared spectrum of XG with XG/AM/BIS copolymer and contrast analysis of the trend of curve and weightlessness area of XG/AM with XGAM/BIS copolymer, verified the crosslinked structure of XG/AM/BIS copolymer;(2) The optimum experiment conditions of CMC/AM/BIS copolymer are as follows: CMC concentration is 1.0×104mg/L, AM concentration is 4×104mg/L, the initiator concentration is 650 mg/L, mole ratio of(NH4)2S2O8 and Na2SO3 is 1:1, BIS concentration is 25 mg/L, distilled water is 250 ml, reaction temperature is 40 ℃, reaction time is 8 h; The optimum experiment conditions of XG/AM/BIS copolymer are as follows: XG concentration is 1.0×103mg/L, AM concentration is 2.0×104mg/L, the initiator concentration is 420mg/L, mole ratio of(NH4)2S2O8 and Na2SO3 is 1:1, BIS concentration is 630mg/L, distilled water is 250 ml, reaction temperature is 50 ℃, reaction time is 8 h;(3) Both CMC/AM/BIS and XG/AM/BIS copolymer don’t dehydrate in high salt concentration 25×104mg/L. The applicable salinity of these systems is ranging from 0~ 25×104mg/L;(4) The applicable ambient temperature of CMC/AM/BIS copolymer system is 120 ℃, which is suitable for high temperature reservoir. The applicable ambient temperature of XG/AM/BIS copolymer system is 140℃, which is suitable for super high temperature reservoir;(5) With the increase of shear rate, the viscosity of CMC/AM/BIS system and XG/AM/BIS system decrease, which present its pseudoplastic after high speed shearing, both of them have strong ability to resist shear,viscosity retention rate at 90.3% and 91.6% respectively;(6) The breakthrough pressure gradient simulation experiment shows that strength and adhesive ability of XG/AM/BIS system is relatively strong, the value of breakthrough pressure gradient is 0.172 MPa·m-1, CMC/AM/BIS weak gel strength is relatively weak, the breakthrough pressure gradient value is 0.0355 MPa·m-1, compared with the high-strength gel, the value of breakthrough pressure gradient of these systems is relatively small, both systems own good injectivity.