Abstract: The reservoir size sequential method is an important method for petroleum resource estimation. However, with this method irrational predicted results are often gained by selecting value k in terms of minimum standard error as principle. This paper proposes an improved algorithm in terms of k-line chart concept and "1-2-2 principle" for determine value k. The numerous testing results indicate that "1-2-2 principle" combined with k-line chart will be more reasonable to give value k, and more helpful to improve the predicted precision.

Key words: reservoir size, resource estimation, reserve, sequential method