Research On Hydraulic Pulse Wave Assisted Deep Acidification Technique Of Decreasing Pressure And Increasing Injection In Low Permeability Reservoir

With the constant increasing development to the low permeability reservoirs in China,how to realize the effective treatment to the injection wells is becoming one of the key factorsto assure the reservoirs efficiently developed. Due to the special geological conditions of lowpermeability reservoirs, general hydraulic fracturing prones to water channeling in singledirection and matrix acidizing could not reach the expected effect, while hydraulic pulsecomposite acidizing technique has high adaptability to such reservoirs. Hydraulic pulse waveactions could improve the chemical reacting rate and effect of plug-release agent as well asextend the chemical action distance; meanwhile, tamper around the wellbore or bullet holethat could not form or be inhibited by vibration effect functioned as "dynamic plug-releasing"engineering, is advantageous to the seepage, and can reduce or inhibit the plug secondforming, improve the chemical treatment effects, and extend the function period.This technique has received a certain scope of applications and effective responses in theoil fields, but the lack of theoretical research and empirical or blindness factors inconstructions, have restricted its further promotion. On this basis, in the paper, effectsbetween hydraulic pulse composite deep acidizing technique and solo-measures are evaluated,optimization work way of side pulse side acidizing composite technique is obtained, and thehydraulic pulse composite deep acidizing kinetics reaction mechanism for reducing pressureand increasing injection is revealed. Then the multi-wave stacking motion equation of isdeduced, acidification as well as acid rock reaction models of various acid systems areestablished; then acidification model of acid system under the hydraulic pulse wave conditionare deducted and resolved and a software for hydraulic pulse wave aided acidizing andplug-release is developed. Acid rock reaction law under hydraulic pulse wave is analyzed; theeffects of partial key factors as frequency, amplitude, distance, time etc. to the acid flowvelocity and concentration distribution is considered; hydraulic pulse wave aided acidificationeffect by taking injection quantity as an index is forecasted. On the above foundations, highpower hydraulic pulse generator suitable for downhole operation is developed. Simulationgenerator device indoor experiments are carried out and the case pipe safety in its implementation is determined and the optimum injection pressure and maximum vibrationsource output power of the equipment is optimized. Finally, using Gasi low permeabilitysandstone reservoir as an example, this paper made a deep research about the damagemechanism to the injection well of Gasi low-permeability reservoir; static/dynamic acidsystem evaluation experiments and hydraulic pulse composite deep acidizing experiments arecarried out, and two multi-hydrogen acid systems—suitable for deep acidizing andplug-releasing to Gasi reservoir injection well—are optimized; eventually, the hydraulic pulsewave aided deep acidizing pilot test is carried out, and in site construction technique and wellchoose conditions are further optimized. The pilot test verifies the advantages of good effectand long validity etc. of hydraulic pulse wave aided deep acidification. Theory support forfurther promoting the application of this technology in Gasi and similar low permeabilityoilfields is provided.