Reservoir Protection Technology Used in Cementing Horizontal Wells in Chenghai Xinqu, Bohai Bay

The Shahejie Formation sandstone is a proven shallow heavy oil reservoir located in the Chenghai Xinqu area, Bohai Bay. Eight horizontal wells have been planned to drill in this area and completed with screen pipes. The φ244.5 mm technical casing is used to case the horizontal section drilled into the Shahejie Formation. In early stage exploration, the sandstone reservoir was highly contaminated because of mud losses into the high porosity high permeability sandstone, invasion of cement slurry filtrates, and edgebottom water channeling caused by casing string eccentricity. To protect the reservoir from damaging, a low-density low filter loss nanoparticle cement slurry of 1.5 g/cm³ was used to cement the well. The cement slurry had no free water and no density difference between the top and the bottom. The strength of the set cement was at least 17.9 MPa after aging for 24 hours, and the filter loss of the cement slurry was 38 mL at most. These two parameters are 24% better than standard requirements for cement slurry. A new type of φ244.5 mm all-in-one elastic centralizer was used with casing. This all-in-one elastic centralizer has no stress weak point, and compared with conventional centralizers, this new type of centralizer has restoring force that is 25% higher, starting force that is 27% lower, the centrality of the casing string can be enhanced by at least 57%. These technologies have been proved suitable for use in cementing horizontal wells drilled in Chenghai Xinqu. Six wells have been cemented with these technologies and no slurry losses and water channeling have occurred during well cementing. High quality cement job and high oil production rate were obtained. These technologies are beneficial to the development of oil and gas resources in Chenghai Xinqu area.