Research and Application of Integrated Technology of Chemical Sand Control and Stratified Water Injection in Offshore Oilfields Injection Well

Abstract

ABSTRACT: This paper proposes an integrated technology of chemical sand control and stratified water injection in water injection well, which enlarge the inner diameter of injection well and achieve flexible stratification. The technology realizes completion by chemical sand control. The ceramsite whose surface has been treated by crosslinking agent is injected into the well and form a cement layer with a thickness of 3-5 cm. This layer can be used as a barrier to retain sand and provide channels for fluids. Then, the stratified injection string is run to realize the stratification of the injection reservoir. The position and quantity of the stratification are designed can adjust flexibly. This technology has been successfully applied in the Bohai Oilfield. The conventional sand control and injection technology makes it difficult for the actual injection rate to reach the target value. After applying the integrated technology, for a directional well with a bore diameter of 9.625 in, the maximum inner diameter can reach 7 in. The number of injection layers exceeds 5, and the actual injection volume meets the designed rate. Besides, the water cut of the beneficiary well decreases, and the oil production rate increases. 1. INTRODUCTION Stratified water injection is an important measure to improve the overall oil recovery, and it is very important to achieve sufficient water injection in the target reservoir. The sand control method of water injection wells in offshore oilfields is mainly mechanical sand control. The plug-in seal on the water injection pipe cooperates with the sealing cylinder to realize stratified water injection, which the number of layers is generally 3-4. For reservoirs with strong vertical heterogeneity, there may be problems such as large differences in water absorption profiles in the same injection layer, small longitudinal sweep coefficient of water flooding, and overall water injection rate that does not meet the design requirements. It is difficult to change the number and the location of layers, and it is impossible to adjust the layers according to the water injection system. In addition, the inner diameter of mechanical sand control is small, and the downhole testing and other operations are difficult, which also limits the injection rate.