Abstract
Horizontal well and acid stimulation are the essential technologies for the development of complex carbonate reservoir. However, it is extremely difficult to conduct effective stimulation in horizontal wells with a long interval because the traditional acid systems without diverting performance can only flow into the high permeable formations, leaving the damaged formation untreated. That is why the long interval wells with high heterogeneity need to be stimulated by diverting acid system. Many diverting acid systems or diverting agents have been developed in recent decades. Whereas, last generation diverting systems always cause serious damage to formation, such as gelled acid based on polymer. In addition, many systems will lose their diverting performance at high temperature.
This paper studied some kind of residual-free fluid systems for both acid treatment and fracturing in order to develop no-damage/reduced-damage and high effective stimulation techniques for long interval wells. It is designed to conduct uniform stimulation in a long distance wellbore with the assistance of diverting performance of some special chemical agents, which can work at high termperature and leave no damage in formation. No-damage stimulation includes: Temperature-controlled deep-diverting acid system (TCA); pH-controlled self-diverting acid system (DCA), and Fracture reorientation technology based on degradable fiber (RDF). This series of technologies can generate fracture networks to enhance the stimulated reservoir volume through fracture reorientation and diverting acidizing with the help of special residual-free fluid system, leaving no damage in formation.
This series of techniques had been applied on 921 wells from 10 oil/gas fields in China and 7 oil/gas fields in Kazakhstan, Iran, Iraq, Syria and Turkmenistan.
