With further exploration and development , it has become difficult to exploit the oil and gas reservoir , more and more complex reservoir using conventional fracturing and acidizing effect is not obvious. In recent years, using the pre-positioned acid fracturing technology in some blocks fracturing has achieved good stimulation effect. Because the pad acid can improve the connectivity of reservoir and crack and cracks inside, form the effective flow conductivity, enlarge the drainage area, reduce the fluid flow resistance, improve the single well production. According to the statistics the pre-positioned acid fracturing effect in the acid sensitive reservoir is unsatisfactory. How to improve the reconstruction effect of complex reservoir, my company's technical personnel study found that due to the low acid corrosion capacity, the pad acid generate cracks and the connectivity of cracks inside is poor in the acid sensitive reservoir. At the same time the pad acid produce a large amount of acid slag, reduce the effective permeability of fracture face, and do not significantly increase the effective conductivity as a whole.

The acid sensitive pad acid fluid system is formed by optimization and compound experiments, it has the features of multi-stage flow speed retardance, strong corrosion,

maintain a low pH ,inhibit secondary precipitate, reduce acid slag and rapid flowback, and improve the damage rate of acid sensitive reservoir. The different types of acid sensitive reservoir conditions is simulated and inversed by our company, optimized and formed proper process parameters of pre-positioned acid fracturing in acid sensitive reservoir, combined with our company in pre-positioned acid fracturing measures empirical correction in recent years, the complex reservoir pre-positioned acid fracturing technology is produced.The technology in the domestic oil field's applications are more than 50 well times, compared with the similar measures, and has obvious yield-increasing effect.

Characteristics:

①Good acid retarding performance, improve the drainage area

②Strong corrosion performance, increase the fracture connectivity

③Good resistance to acid sensitivity, inhibit secondary precipitate, reduce acid slag, improve the effective                 permeability of fracture face, prolong period of validity of measures

④Simulation and inversion on acid sensitive reservoir, increase the purpose of acidizing fluid, improve the                   development efficiency of oil wells in some blocks.

                                      Centrealoil