Centrealoil--Viscoelastic surfactant acid acidizing technology
The main purpose of the carbonate reservoir fracturing acidizing is to remove the pollution of near wellbore area, and generate new flow path (acid wormhole)around the pollution zone in order to increase the connectivity of reservoir and wellbore, improve the production capacity of oil and gas wells or the injectivity of injection wells. For strong heterogeneity of carbonate reservoir, the key to success of fracture acidizing lies in whether can make acid in the whole production layer reasonable placement, make all interval can be inhaled enough acid to remove pollution near wellbore area, so as to achieve the purpose of restore or increase oil and gas production. Due to the reservoir heterogeneity is very strong, injection acid will mainly into high permeability layer or less polluting interval, but for the low permeability layer or high pollution zone, efforts to transform are smaller or has not been transformed, especially oil and gas wells in the late stage of water flooding development. Water flood recovery make each layer permeability increases further, so that uniform acid distribution is very difficult, even the relatively homogeneous reservoir, due to differences in the degree of pollution that can also cause acid to reasonable place.
For heterogeneous reservoir, the conventional steering acid system is usually preferred to penetrate some high capacity channels or high permeability zone of the reservoir, that is, from the high capacity channels or high permeability zone of the reservoir occurs fingering, acid is difficult to effect in low permeability reservoir zone, while the low permeability reservoir is the need to be transformed. Acidizing on carbonate reservoir by ordinary hydrochloric acid, some of the main channels are formed by acid dissolution in the bedrock, the acid liquid can flow along these channels, rather than on other rock stratums of acidification treatment. Then, if you add the diverting agent to the general acid, the diverting agent will be temporarily blocked the channels, change acid injection flow profile, make the acid fluid into the relatively low permeability zone, and react with non-acidified reservoir zone. Through the high capacity channels or high permeability zone of the reservoir for temporary plugging, forcing the acid to low permeability zone, in order to transform the reservoir high permeability zone and low permeability zone at the same time, this is the steering acidizing technique.
Viscoelastic surfactant self-diverting acid acidizing technique is a kind of new technology of heterogeneous reservoir transformation. Its preparation is simple, easy to gel breaking, small damage to reservoir, and has a retarding effect and filtrate value is about 2, under the effect of free Ca2+, Mg2+, the viscoelastic surfactant arrangement structure changed to make the viscosity of system increased, forcing the acid liquid turned into low permeability zone from the high permeability zone. The technology in the application of oil and gas wells is more than 10 wells, and has obvious yield-increasing effect.
Characteristics:
①It shows that has good viscoelasticity and slow performance, than ordinary gelling acid delay 3-5 times.
②It has obvious friction reduction, good the stability performance of anti-clay-swelling, can automatically break.
③It can effectively ensure the selective distribution of acid liquid, delay the speed of the reaction between acid fluid and rock, and is conducive to deep dissolution modification of the deep reservoir.
④The gel breaking liquid of system has no residue, little influence on fracture conductivity.
⑤The system in the reservoir can be automatically diverting and steering
⑥It is suitable for within 120℃carbonate reservoir acidizing reconstruction.
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