Abstract
This paper presents a novel alcoholic acid system to remove the damage caused by frac fluid in tight gas reservoir. Damage resulting from hydraulic fractures takes two distinct forms: damage inside the fracture itself because of inadequate breaking of the fracturing fluid polymer; and fracture-face damage because of excessive leak-off. The objectives of laboratory experiments are to identify potential damage and aid selection of the optimum treatment fluid and design. A novel alcoholic acid flow tests illustrated the permeability increased because of pore & throat enlarged by using mercury intrusion experiments. It was critical in addressing issues of selection of fracturing fluids, polymer concentrations and breakers. Improved breaker systems show even greater benefit when used in conjunction with the lower loading polymer systems. The newer fluid systems enhance load recovery and reduce formation exposure to potentially damaging polymer residue.
DB gas reservoir is a low porosity, low permeability reservoir in the northwest of China. Large scale of hydraulic Fracturing has been carried out as effective method to get high gas production rates. However, the gas production rate after treatment increased to 335,683m3/d, and then declined to 34,875m3/d rapidly. The skin factor from well testing after hydraulic fracturing was 112, which indicated fractures and formation may appear damaged seriously because of more than 60% of the load fluid can be invaded and trapped in the formation by entering the smaller capillary pores during higher injection pressures. The gas production rate recovered from 32,383m3/d to 301,374m3/d and kept constantly by using treatment method of a novel alcoholic acid system.