Acidizing Offshore Sandstone Reservoir with a Single Slug Active Acid System

In offshore oil and gas development in China, particle migration, clay particle blocking and inorganic salt blocking during mixed water injection for sewage cleaning have caused damage to unconsolidated sandstone reservoirs. Conventional acidizing jobs in an effort to stimulating the wells drilled were restricted by those adverse factors such as limited work space on well platform, repeated acidizing jobs and short effective production time of the acidized wells, etc. In a study to solve these problems, the synergy of different additives is exploited. In laboratory experiments, HCl, three polyprotic acids, a corrosion inhibitor, a fluorocarbon surfactantand a cationic polymer are mixed in a certain ratio and order to produce a compound, the HX-01 active acid system, which is further concentrated for the ease of job. HX-01 is injected with water in a single slug into the well, greatly simplify the acidizing job. In field acidizing work, HX-01 shows those advantages such as strong scale dissolution, low surface tension, strong clay dissolution, low damage to formation matrix, reduced advancing speed deep in reservoir formations, low corrosion and high dynamic displacing capacity etc. The use of HX-01 has solved the problems encountered in offshore well acidizing jobs, and changed the operation techniques of the conventional acidizing process presently in use.