Abstract
The Wen Chang oil field in the South China Sea is exploited mainly with horizontal wells completed with a sand screen and equipped with an electrical submersible pump (ESP) plus Y-tool for the production string. The water cut in one well has reached 74%, making diagnosis of the water entrance critical for a success remedial operation in the well.
Because flow regimes in highly deviated and horizontal wells are quite different from those in vertical wells, the velocity and holdup distribution are required for accurate flow rate and fluid entry determinations in multiphase flow. In addition to the sand screen completions and variation in the well trajectory, the presence of annulus flow makes the measurements even more complex. Production logging in horizontal wells can be challenging. An array of mini-spinners with optical gas and resistivity water holdup sensors was conveyed by an electrically powered tractor in the well along a 730-m horizontal interval. Two difficulties in conveying the tool string to TD were that the 5½-in. screen liner is directly hung inside 9 5/8-in. casing without entry guide and that the minimum restriction of the Y-tool bypass tubing is only 2.313 in, so the tool can easily be stuck inside the tubing. These difficulties were overcome by using a specially designed tool string. The operation was successful and high-quality logging data was acquired. Comprehensive interpretation shows that 74.7% of the water comes from the bottom 50-m interval. Recirculating water was also observed in the deviated interval.
Based on the production log analysis and reservoir permeability distribution from logging-while-drilling data, a two-stage annulus chemical packer (ACP) was designed, with one stage to shut off the current bottom water entry and the other prepared for future water control. A production tubing string with flow control nozzles was installed after water shutoff to optimize fluid distribution along the interval. Water was successfully shut off in this horizontal well.
