Analysis and measures for coring difficulties in Well Yongye-2 in Yongshun of Hunan province

Abstract:

In order to solve the problem of insufficient core recovery in broken formation in Yongshun， Hunan Province， this paper investigates the geological structure characteristics of the exploration area with respect to Well Yongye-2， and analyzes the stratum characteristics based on the core samples from different strata. On the premise of strictly following the drilling design and quality requirements， different drilling fluids were adopted for each section to eliminate collapse and leakage. To deal with insufficient core recovery in broken formations， we developed and used a bladder multi-section bundled wireline core drilling tool. The unique bladder structure， equipped with a leading side jet drill bit， can protect the core from erosion by drilling fluid. Field results showed that when drilling deeper well sections with the well depth from 1055.76m to 1108.96m， core recovery increased to more than 90% from the existing lowest 79%， and the cores were well protected. The author believes that the above method can effectively solve the problem of insufficient core recovery in broken formations， and can provide guarantee and reference for follow-up work and similar projects.