Sandstone Reservoir Damage Diagnostic Techniques And Injury Lifting Of Countermeasures

Sandstone acidizing is one of the most widely used stimulation methods for oil or water injection well.For the purpose of the removal of damage caused by drilling, completion, production and water injection operations, the skin factor of well test analysis is usually adopted to evaluate the damage condition of a particular well.However, field practices and some analysises presented in this dissertation suggested some restrictions of well test analysis when a design of damage removal treatment is needed. These restrictions results in that we can't get a detailed information of the damaged well which is critical to the designing of acidizing.To solve this problem, a method of determining the major and minor damage factors of a particular well by quantitative analysis was put forward, which makes up for the defects of well test analysis and ensures the optimization of the design of damage removal treatment.The core of the new method is to determine the respective influence of all damage factors existing in a particular well. On the basis of the analysis of formation damage from both internal and external aspects, several damage mechanisms commonly occurring in a producer or injector were modeled. These mechanisms included the plugging of drilling solids and filtration, particle migration, clay hydration and swelling, organic and inorganic scaling as well as the plugging of solids and bacteria in a water injection well. With these models, the damage skin and the radius of the damage zone caused by various factors could be diagnosed accurately.Besides, the influence of damage on a horizontal well was considered by a study of the calculation of damage skin factor. Comparison of two model indicated that model of Furui-Zhu-Hill is more reasonable.With the knowledge of the major and minor damage factors, various special damage removal techniques for different damaging materials are studied in order to treat the damaged well suiting the remedy to the case. In combination with the optimizing object of the removal of damage zone , the design of acidizing in a sandstone formation is simulated.To gain a better result of stimulation, the potential damage that may be introduced by the treatment must be precautioned or reduced minimally.Based on the models involved, the diagnosis of the damage done to a well and the design of acidizing were programmed. Case studies were given and some instructiveconclusions were drawn.