The Study On Rheological Properties Of Visco-Elastic Surfactant Diverting Acid And The Kinetics Of Its Acid-Rock Reaction

There are a large amount of heterogeneous carbonate reservoirs in China. Whencarbonate hydrocarbon bearing formations are acidized by hydrochloric acid, a fewdominating channels in the carbonate matrix are created and the majority of thetreatment acid will flow along these channels, leaving the rest of the rock untreated.Therefore, a diverting agent is often needed. Polymer gels, foams or rock salts arecommonly used as diverting agents during matrix acidizing of carbonates. Thesematerials can not allow the acid to reach its full stimulation potential and may causedamage due to residue precipitation, saturation alteration, or solid invasion. TheSelf-Diverting-Acid (SDA) using a Visco-Elastic Surfactant (VES) is a new divertingagent for carbonate reservoirs, which is no damage to the formation, no need for across-linker and a breaker and can reduce the acid-rock reacting rate at the same time.Although it has been used in some oil fields, the study on its rheological properties isbehind its application. In this doctoral dissertation, rheological properties of the agentare studied systematacially, which include the relationships of the agent viscosity withthe VES content, pH, temperature, ion type, etc. In the thesis, the acid-rock reactionkinetics in the condition of a changing viscosity is investigated for the first time andthe important parameters such as the reaction rate constant, reaction order andreaction rate control stages are given out. Furthermore, the reaction rates of differentacids and at different temperature were comparatively studied. Efficiency has beentested by both the methods of multi-core flow test and applications in three wellslocated in the west of China.