Study On Improvement Of Injection Of Mobei Low Permeability High Temperature Reservoir

The low-permeability oil reservoirs always had the injection problems that were the lower injection water and higher injection pressure. The "Oligomer" is the cationic organic polymer with low molecular, which is used to improve the injection problem that belongs to the low-permeability reservoirs. Of course, it should also mixes with the inorganic salt or the nanometer materials to improve the reservoir better. The Mobei oil field is the typical low-permeability and high-temperature reservoir, and the average porosity of the formation is about 11.93% and the permeability is about 1.82mD. At the same time, the average porosity of the oil layer is about 13.57% and the permeability is about 3.19mD of the Mobei oil field. On the other hand, the pressure of this reservoir is about 38.45MPa, the temperature is about 103℃and the pressure coefficient is 0.97.This thesis based on the large investigation through the home and aboard, which gives a comprehensive summary and introduction about the definition of the low-permeability reservoir, the formation characteristics, the production problems and the improving technologies in the typical reservoir. It gives the result that the "Oligomer" and the nanometer materials having the greater potentiality to improve the injection problem, which maybe has the largest market in the future. However, there is also a problem that the researches about the nanometer materials, especially used in the petroleum industry, is poor and have a higher price. So we choose the "Oligomer" mixing with a spot of the other materials as the goal in this research, which will be used to improve the injection and decrease the injection pressure.This thesis was based on the relation research theory to search the reason of the lower injection and higher pressure. And the analysis included the production performance, the characteristics of the injection water and crude oil, the feature of the microcosmic pore structure, the feature of the clay mineral and the harmful effect in the formation, and the formation sensibilities and so on. The research results told us that the poor reservoir physical properties; strong water-sensitive and the low mineralization of the injection water were the main reasons of the poor injection in this field. Further more, the higher content clay minerals; the clay minerals swelling, dispersion and migration were the key reasons. So, researching the clay minerals was a very important work in this project.After researching the electric characteristics of the clay, the deeper work about the formation sensitivity of this oil field was worth. Based on the theory of the "swelling" and "shrinking", there had a large and significant work about the evaluation of the 11 chemical systems matching with the formation fluids. At the same time, the work that weather they had a good effect to the four clay minerals were done, and evaluated the effect of preventing swelling and the shrinking work. We prepared the simulate clay minerals, which based on the Mobei oil field, and evaluated the shrinking effect of the systems as the standard to choose the chemical system. At the beginning, we choosed the AY6 and GY6 as the candidates, and the anti-expansion rate of the AY6 was about 70.48% and the shrinking rate was about 62.04%; and the anti-expansion rate of the GY6 was about 73.33% and the shrinking rate was about 19.23%. Further more, we also complexed these two systems as the different ratio, and evaluated the shrinking and anti-expansion effect. It can take a good work to the next flow-testing.At last, we choosed the optimal system through the physical simulation (flow-test) to evaluate the effect of the system. Here we choosed the AY6, BY1 and GY6 as the basic to choose the optimal system. The work had been done with the single system, binary system and ternary system to test the displacement pressure decreasing and augmented injection of the formation core from the Mobei oil field. The results of the test told us that the systems of A:B:G=3:1:3 and A:G=3:1 had a good, effect to decrease the injection pressure and increase the injection. After injecting the A:B:G=3:1:3, and using the 20PV injection water to displace the nature core, the drop of the pressure was about 65.78%; and if used the system of the A:G=3:1, then used the 10PV injection water washing the nature core, the drop of the pressure is about 68.50%. The next was choosing the optimal slugs of the two systems, and the result that the system of A:B:G=3:1:3 with 0.5PV and the system of A:G=3:1 with 1.0PV were the optimal slugs, and the former was the best.