Study and Application of Low-permeability Reservoir Protection Techniques in Shengli Shallow Sea Area

Study has been conducted on reservoir characteristics and fluid property in low-permeability reservoir of Dongying formation in the eastern slope area of Chengdao oil-field in Shengli shallow sea area. Through laboratory study on reservoir sensitivity, the reservoir damage mechanism and damage degree were understood. On the basis of the study results, drilling fluid and completion fluid were optimized. In addition, high quality sea water drilling fluid has been developed. Through basic characteristic comparison with other drilling fluid systems, evaluation on the anti-pollution property and analysis of dynamic filtration results, it is indicated that this kind of drilling fluid system has good result in oil reservoir protection, with 90% core permeability retrieving. This kind of drilling fluid system has been applied in 19 wells, and testing has been conducted in 6 wells. Among these six wells, the performance of five wells has been improved, with skin factor less than zero. One well was slightly damaged. The improvement efficiency of these six tested wells is 83.3%, which indicated that kind of drilling fluid system has good result in oil reservoir protection.