Study On Acidification Technology Of Limestone Reservoir In D Oilfield

Matrix acidizing is one of the common means of plug removal and stimulation for limestone reservoir, and its stimulation mechanism is closely related to the formation of wormhole. Conventional hydrochloric acid system is the only acid type used in D oilfield; conventional acid acidizing effect is poor when used to long reservoir interal with strong heterogeneity; acid with reservoir rock reaction mechanism is unclear; acid design is blind and merely rely on past experience, whether form the effective wormhole or improve near wellbore permeability or not is not clear. The above factors limit the economic efficiency and effective of D Oilfield acidizing.To solve the above problems, this thesis takes D Oilfield Baturaja limestone reservoir as research object, analysis reservoir core, damage factors and previous acid system; launch acid system single-dose screening and comprehensive experiment evaluation of the performance of acid; conduct acid rock reaction kinetics and reservoir core wormhole development verification experiment; deduce and establish the radial dual scale model which can descript wormhole growth and development during carbonate matrix acidizing, and carry out Matlab programming simulation study, analysis and discuss some factors which can influence the wormhole formation, expansion and dissolution form; provide acid injection rate and strength optimizing recommendations for typical oil wells and predict the effect of acidizing.The main results obtained in this thesis are as follows:(1)Target reservoir’s porosity and permeability is mainly high, but also with some low porosity and permeability layers, physical difference is large, heterogeneity is strong, reservoir damage is mainly caused by fluid loss during drilling and completion, matrix acidizing can removal damage and increase productivity effectively.(2) Screen out three acid system (conventional acid, gelled acid and self-diverting acid) and provide formulations of the three acid system under three temperatures (60℃,90℃and120℃), systematically evaluate the indoor comprehensive performance of acid, conduct self-diverting acid special feature experiment study, evaluation result turn out to be good.(3) Reacted-acid concentration of different acid study shows that20%conventional acid,20%gelled acid,20%self-diverting reacted-acid concentration is1.49%,2.73%,4.87%in divided, there is some difference with previous view which is10%of the initial concentration; obtain acid rock kinetic parameters of the three acid types, providing key parameters for the acidizing simulation, to predict acidizing effect accurately.(4) Verify that reservoir core is easy to form wormhole, forming wormhole can significantly improve the core flow capacity; analysis and discuss injection rate, amount of acid, reservoir temperature, acid concentration and acid type influence about the wormhole formation, expansion and dissolution form; among which injecting rate and temperature impact most.(5) Conduct case study of actual target oil wells, make clear that acid injection rate and damage radius are the determining factor affecting acid strength, put forward method to design key construction parapmeters such as acid injecting rate and acid strength.