Research on the Mechanism of Damage to Casing Pipe in Oil and Water Wells of Uneven Sandstone Oilfield and Preventive Technical Countermeasures

Oil and water wells are the basic conditions for oilfield production. Once the casing is damaged, it will not only cause huge waste of investment costs, but also bring serious impacts on oilfield development. To this end, the A Development Zone of Daqing Changyuan Oilfield has deeply studied causes and mechanisms of casing damage according to the actual situation of casing damage, absorbed the experience and lessons from the B Development Zone where the casing damage is more serious, clarified that the non-oil layer part of the casing damage is mainly concentrated at the bottom of the Nen II segment, and the reason for the damage is that the oilale with a thickness of about 10 m enters water to produce stratum sliding, resulting in the damage of the casing of the oil and water wells in the block; damage in the oil layer part is mainly concentrated at the top of the shot hole, and the reason for the damage is that the overpressure water injection, high-intensity water injection other super pressure cause the damage. On this basis, targeted prevention and control measures have been implemented, and the monitoring and early warning system for damaged wells has been established, the census method of the water-soaked area at the bottom of the Nen II segment has been created, and the corresponding prevention and control measures such as preventing water channeling and pressure relief have been taken to ensure that the old damaged area does not expand and the new one does not occur; In the oil layer part, the method of inventory and treatment of abnormal pressure layer has been established. The implementation of a series of supporting technologies and methods for the prevention and treatment of casing damage has effectively controlled the speed of casing damage, and annual casing damage rate has declined year by year, and it has been controlled within 1% for 30 consecutive years, which is more than 3 percentage points lower that of the same type of development zone, and the casing damage rate of 100 operation wells is controlled within 2.0%. The effective control of the of casing damage has laid a good foundation for the deep adjustment of the injection and production structure in the development zone, and the A development zone has achieved orderly and efficient development the period of extremely high water cut.