PREDICTING WELL PRODUCTIVITY FROM GRAIN-SIZE ANALYSIS AND LOGGING WHILE DRILLING

Grain size analysis of drill cuttings and Logging While Drilling (LWD) are used to predict permeability-height (KH) in high-angle wells. In the Sherwood Sandstone reservoir, Wytch Farm Field, permeability is co ntrolled by porosity and grain size. These can be measured using LWD d ensity logs and sieve analysis of cuttings. KH and Productivity Index (PI) are estimated using permeability-bulk density transforms for each grain size class. A PI of 60 (-35/+120) STB/day/psi was predicted for the first extended reach well on Wytch Farm. The initial PI was 100 S TB/day/psi. This test result calibrated the model for subsequent wells . The predicted PI of the second well was 42 (+/-15) STB/day/psi. The initial PI was 40 STB/day/psi. The KH plot is used to geosteer the wel l; optimize perforation intervals, and to estimate PI in wells plugged -back for water shut-off.