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Technical characteristics and development changes
⑴ Optimization design technology goals are different from the past
——Due to the fact that closed crack acidification technology can greatly improve the effective flow capacity of cracks, the optimization goal of multi-stage injection technology is mainly to obtain long acid etched cracks (requiring high displacement construction, which is conducive to achieving long cracks).
——No longer considering the optimal match between crack length and flow capacity in the optimization design of simple acid fracturing technology, the improvement of flow capacity is achieved through closed crack acidification.
⑵ The cycle yield increase effect has become the main optimization objective of the preferred acid fracturing technology method. Multi stage injection technology is no longer simply an acid fracturing technique for low-permeability tight reservoirs. In medium high permeability reservoirs, multi-stage injection closure fracture acidification technology still remains the mainstream technology, but the optimization of scale and injection stages is different from that of low-permeability reservoirs.
(3)The construction scale is relatively large. The acid strength is mostly between 6-9m3/m, and with the addition of non reactive pre solution injected alternately, the total liquid volume is larger.
⑷ Multiple injection stages and small segmented liquid volume. The maximum injection level is 8-12 levels, and the segmented liquid volume is generally 20-40m3.
(5) The liquid system for multi-stage injection is more abundant – the preflush has developed from pure gel water (guanidine gel, etc.) to oil-based preflush, or alternatively injected by emulsified acid, self rotating acid and gelled acid—— Conversion acid, alcohol acid, etc. have also been put into use—— On site practice of combining multi-stage injection of emulsified acid or self rotating acid+gelling acid with closed acidification and layered acid pressure during ball throwing.
(6)The liquid system is relatively stable, but the overall performance of the liquid has been improved – the deep acid pressing technology uses liquid systems mainly composed of gelling acid, emulsifying acid, and rotational acid. The dosage of gelling acid decreases, but the viscosity significantly increases—— Emulsified acid has achieved microemulsification technology, forming a microemulsion acid system with relatively low friction—— Underground cross-linking acid (filtration control acid) and other acid systems are preferred for use under certain geological characteristics and conditions;