Use of Partial Perforations in Oseberg Horizontal Wells

Abstract

Abstract This paper describes the planning, implementation, and results of partial perforations in Oseberg horizontal wells completed with cemented liners. Partial perforations are used primarily to achieve sufficient areal sweep, drain multi-formation systems, delay gas and water breakthrough, and to control the watercut. The perforation strategies are determined utilizing simulation models. The well trajectory and the permeability variation are obtained from measurement-while-drilling logs. The effects of the horizontal well trajectory modelling, permeability, structural dip, interlayer permeability, and factional pressure drop on the inflow profiles are discussed in the paper. Detailed well and reservoir modelling are necessary to arrive at a successful partial perforation strategy in horizontal wells. Incorrect parameters such as the permeability profile may result in selected perforation intervals that yield non-uniform inflow, lack of multi-formation drainage, and in some cases lift problems. This paper demonstrates the importance of knowing the permeability profile along the horizontal well section prior to determining the perforation intervals. The influence of the factional pressure drop in the producing well section on the uniformity of the horizontal well inflow profile is important in highly-permeable formations. Matching of the actual inflow observed utilizing production logging allows for estimating the horizontal and vertical permeability profiles, and the permeability profiles determined from M WD logs and geological permeability maps appear to be confirmed. However, unique estimates of the permeabilities cannot be obtained. Production logging in the Oseberg horizontal wells shows that the inflow profile can be controlled by use of selective perforations. The field data also indicate that the partial perforation strategies have provided acceptable results. The Oseberg field examples yield new and useful information regarding perforating horizontal wells completed with cemented liners.