| Title | Development of Wellbore Simulator and Verification Test of High Temperature PTS+FLUID Sampler Logging System for a Highly Deviated Geothermal Well |
|---|---|
| Authors | Masashi KATO, Takashi OKABE, Satoshi UJYO, Koshiro TAKANASHI, Russell KUNZMAN |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | Ministry of the Environment, National Park, Highly deviated well, Wellbore simulator, GFLOW, Drift flux model, PTS tool, downhole sampler tool, roller centralizer |
| Abstract | Development of geothermal energy has been restricted in Japan because approximately 80% of the abundant resources are located in national parks. To promote the energy diversification and utilize the resources in the national parks efficiently, an R&D (Research and Development) project funded by the Ministry of the Environment on geothermal well drilling technology is under way in Japan. The project purpose is to develop an environment-friendly low-cost drilling technology for a highly deviated well (HDW, 2,500m deviation, 70° inclination) to access the high-temperature geothermal resources from the outside the national parks. The goal is to keep power generation cost as-is, even if a highly deviated well is drilled. To achieve the goal, there are concrete targets of the project such as 10% drilling cost reduction and 50% productivity increase through technology developments, including cutting-edge technologies to increase ROP (Rate of penetration), optimal CSG design, logging and so on. In the course of the project, a wellbore simulator and PTS+fluid sampler system with roller centralizers were developed. A wellbore simulator applicable for a HDW was developed to compare steam flow rates with drilling costs for different well deviations. The drift-flux correlation was identified as most suitable for these wells, and integrated into the existing GFLOW wellbore code to simulate the HDW. We confirmed applicability of this correlation by the model calculation and the comparison with the actual logging result. The wellbore simulator was used to estimate the optimal drilling direction that maximized the economic return from the well. In order to evaluate productivity of the HDW, roller centralizers were added to a PTS/two-phase sampler logging tool. The tool can acquire simultaneously PTS data and collect fluid samples. The pressure and temperature specifications are maxima of 34.5MPa and 350 deg.C, respectively. The capacity of the sample chamber is 500 mL and the sampler can acquire brine, vapor and/or two-phase fluid. The tool was applied to geothermal production wells for the first time in Japan, and PTS data and downhole fluid samples were successfully collected simultaneously. Because the roller centralizer was effective in centering the tool in the hole, the tool up-and-down behavior was very smooth and the spinner data were of excellent quality. In this paper, outlines of the project, the development of a combined wellbore simulator and the PTS+fluid sampler system are presented in detail. |