Development of Wellbore Simulator and High Temperature PTS+fluid Sampler Logging System for a Highly Deviated Well

Abstract

An R&D project funded by the Japanese Ministry of the Environment on geothermal well drilling technology is under way. The purpose of the project is to develop an environmentally-friendly low-cost drilling technology for highly deviated wells (approximately 2,500m deviation and 70 degree inclination) in order to access high-temperature geothermal resources inside national parks in Japan, where they are often found, from well-pads outside the parks. 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 highly deviated well (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 compared this correlation with one developed for nearly vertical wells (Orkiszewskicorrelation). We found that the Orkiszewski-correlation overestimated pressure losses and underestimated flowrates for the HDW. 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 tested with the roller centralizers in a geothermal well in Japan. PTS data and fluid samples were successfully collected simultaneously. Because of the roller centralizer, we found that the tool up-and-down behavior was very smooth and the spinner data quality was excellent because the tool was properly centralized in the hole. In this paper, the development of a combined wellbore simulator and the PTS+fluid sampler system are presented in detail.