Application of acid and sand fracturing in carbonate reservoirs

The Tahe carbonate reservoirs are marine facies reservoirs on land buried over 5000 m deep. The formations are featured by high pressure and high temperature, and the reservoirs are fractured and vuggy ones. Most wells only produce after acid fracturing. But some wells achieve productivity by acid refracturing not long after completion due to high closure pressure. In recent years, Tahe oilfield improved fracture conductivity by sand-adding acid fracturing. But the high pressure during sand-adding may cause dangers, and the success ratio of sand-adding is low. By research and exploration, injecting pre-acid during sand-adding acid fracturing achieved good effects.