| With the reducing of conventional oil and gas production and recoverable reserves, the development of low permeability is becoming more and more important, and the water flooding is the main method to enhance the oil recovery rate, therefore to improve the stimulation of low permeability reservoir is the main task that we face.Since Niu25 block of Shengli oilfield has low permeability and clay mineral content is high,this paper researched for the augmented injection mainly from two aspects:on the one hand, to improve water quality in order to reduce the water damage to stratum,the modification of injected water was studied,such as injection water for fine filtering processing, anti-scaling agent, corrosion inhibitor agents; on the other hand, the matrix acidizing changes the pore structure,dissolves the formation of cement, expands the formation pore,and improves the formation permeability,so as to realize increasing water injection,which can provide the necessary basis for water injection wells in the injection site.First of all, through the analysis of reservoir and water quality, corrosion and scaling tendency prediction, selected for the block of the corrosion inhibitor, 2 % anti-swelling agent SL, which anti swelling rate was 86.3 %, 30 mg/L inhibitor 1, which inhibition rate was 96 %and 20 mg/L scale inhibitor 4, which anti fouling rate was 89.8 %,can be taken as the additives of water treatment of this block. To analysis the damage of different water to the reservoir, the dynamic scattering analyzer was used to measure the median particle diameter of suspended in different water and core flooding experiments were made to evaluate the damage of different water to the core. The experimental results show that: after a microporous membrane filtration of different water,the particle size of the suspension were significantly reduced; the treatment effect through the additives and microfiltration membrane is so obvious that the damage rate decreases from 96 % down to 23 %. Therefore fine filtration treatment of sewage and the addition of corresponding reagent again for reinjection, can significantly improve the effect of water injection development.Secondly, three kinds of acidizing recipe were developed,including formula fluoboricacid, acetic acid and citric acid formula formula, the indicators are qualified, control the core dissolution rate around 30 %;adding medicament to acidizing formula were: 4 % inhibitor 1with he corrosion rate of 3.47 g·m-2·h-1, which reaches the standard, 0.5 % surface active agent1, 1 % EDTA as the iron ion stabilizer; to verification acidizing effect, core displacement experiment was made.After the acidification of acetic formulation, core permeability increased from 13×10-3?m2to 255×10-3?m2, the effect is so obvious that the permeability increased by 19.61 times.Finally, acidification mechanism of different acidizing fluid formula were studied through the analysis of acidizing reaction, XRD and SEM, the acidification mechanism of acetic acid acidification is that: framework mineral composition of clay minerals increased, so as to reduce the harm to the reservoir, the pore diameter is increased after acidification and there was no secondary precipitation produced after acidification,thus the reservoir permeability was improved; the acidification mechanism of citric acid formulation is that::after acidification clay mineral is dissolved, the pore diameter is increased after acidification,so the core permeability increased, but due to acidification produced iron dolomite and anhydrite, secondary precipitation was caused, so that the acidification the effect is not ideal. |
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