Practical Transient Multilayer Test Design, Implementation, and Analysis of Gas Wells in the North Sea Southern Basin

Abstract

ABSTRACT Traditional pressure drawdown and build-up analysis of well tests in layered reservoirs has in many cases proven inadequate to describe layer parameters. Without a proper layer description which includes, pressure (Pe or Pr), permeability-thickness (KHl), Darcy skin (Sl), and non-Darcy skin (Dl), future well performance cannot be accurately described. An innovative procedure was developed for gas wells in the North Sea Southern Basin to provide individual layer parameters in commingled, layered reservoir systems. The procedure incorporates pressure Transient Multi-layered Testing (TMLT) within the procedural framework of a Flow-After-Flow (FAF) test, utilising both wellbore pressure and layer rate transients. The TMLT technique has been successfully performed using a personal computer on 4 wells producing from the Rotliegendes sands in the Virgin condition 4V-Field wells, Vanguard 49/16 -Q03/08 and Vulcan 49/21-R06/06, and from the mature producing Victor field, wells 49/22-JD03/03Z and 49/22-JD05/05. Furthermore, the procedures and analysis for TMLT have been successfully executed in these wells despite layer boundaries, differential layer pressures, and problems/uncertainties inherent in spinner-determined flowrates.