Preparation and Evaluation of a New High Performance Diverting Acid

Carbonate rock reservoirs have plenty of micro fractures. Unidirectional fngering of acid solution in acidizing carbonate reservoirs always results in diffculties in communicating fractures and low effciency of acidizing fracturing job. To improve the job effciency, a new high performance diverting acid, which is sensitive to CO₂, has been developed. The diverting acid has a formulation as follows:3.96%SDS+1.09% MPDA+24% HCl+0.5% Z-1 (a corrosion inhibitor). This acid, although not viscoelastic, can acquire viscoelasticity through the reaction of TMPDA with SDS at the presence of CO₂, because the reaction of TMPDA with SDS produces a surfactant Gemini which had superior viscoelasticity. The diverting acid resumed its original state as soon as CO₂ disappeared. Laboratory study has shown that this diverting acid had good high temperature stability, good shearing performance, and superior diverting ability. In core experiment, several groups of cores were displaced with the new diverting acid. It was found that the permeability of the acid-flooded cores increased remarkably, even after removing the biggest permeability increases of two groups of cores. The effciency of acidizing fracturing job can be improved with the new diverting acid, and recycling of the diverting acid may also be realized.