Study On Acidification And Yield Increasing In Horizontal Well Of M Oilfield

Matrix acidizing for carbonates is mainly used in damage removal caused in the drilling and workover process to improve the formation permeability, restore and enhance well productivity. With the further development of M oilfield, production rate of several oil wells were found to decrease, or no yield was encountered after drilling as a result of severe damage formed in the drilling process. It is necessary to carry out stimulation treatment for horizontal wells to improve the productivity. Due to the long drilling time involved for horizontal drilling, formation damage tend to be much more severe than vertical wells. It is of great significance to identify the damage type and select the appropriate and effective measures based on the consideration of practical situation of the targeted reservoir. The main research content of this paper can be summarized as:(1) The problems and technical difficulties existed in the horizontal well acidizing was analyzed first. M oilfield was carbonate with deep burial depth, low pressure coefficient, and can be classified as high temperature formation. The critical challenge was to find an acid system with good retardation and corrosion inhibition, efficient in damage removal, and in the meanwhile, can flow back easily. Therefore, to achieve uniform acid distribution and optimization design.(2) The damage characteristics and models of horizontal wells were studied. Predicted simulation of the distribution of damage radius and skin factor indicated that the damage degree and skin factor decrease from the heel to toe gradually, and the damage zone was an elliptic cone shape big in the heel end and small in the toe end.(3) There set of acid systems were selected:conventional acid, gelled acid and self-diverting acid. Dissolution test, performance evaluation, acid rock reaction kinetics and core-flood experiments were conducted to optimize these there acid systems. A type of environmentally friendly fluid system for damage removal in carbonates was presented. Wormholes can be formed efficiently to achieve the purpose of damage removal. This novel system was low in corrosion and friendly to the environment.(4) Mathematical model for acidizing with self-diverting acid in horizontal wells was established based on the reaction characteristic between self-diverting acid and rock. Acid distribution simulation was conducted in convectional general acidizing and self-diverting acidizing. Simulation results showed that self-diverting acid can achieve uniform distribution with less acid volume, and the simulation performance of self-diverting acidizing was better than convectional general acidizing.