Application of green selfdegradable crosslinked gel for plugging of Geothermal Well DR2024 in Xining City

Abstract:

The problem of lost circulation occurs frequently during geothermal well exploration and development， especially the irreversible loss of geothermal reservoir， seriousely affecting the wellbore stability and drilling efficiency. Geothermal Well DR2024 is located in Xining City， Qinghai Province， which is a geothermal producting well. When drilling to the non-target geothermal reservoir well section of 714~759m， the irreversible loss occurred， where the water gushing and lost circulation exist at the same layer. The drilling fluid while drilling containing composite plugging material fails to plug. After the green self-degradable crosslinked gel was used for 3 times for plugging， the slurry can return to the wellhead and good plugging effect was obtained. Furthermore， the application feasibility and practicability of green self-degradable crosslinked gel for geothermal reservoir plugging was preliminarily verified. The gel is composed of gelling agent， retarder and crosslinker， which has the characteristics of simple formula， self-degradation， environmental friendly， controllable gelation time， adjustable self-degradable time and strong water insulation property. It has broad application prospects in geothermal reservoir plugging. The successful experience in this paper can provide reference for similar geothermal drilling project.