Water Injection Completion Philosophy in A Deepwater Subsea Environment Requiring Sand Control: A Case Study of 29 Injection Wells West Of Shetland.

Abstract

Water Injection completion selection in a deepwater subsea environment requiring sand control is currently an inexact science with lack of a proven track record for life of field solutions. The West of Shetlands (WoS) fields Foinaven, Schiehallion and Loyal have been on injection since 1997 and are starting to develop a substantial track record of injection performance. This case study will provide a performance comparison of the 2 main completion types installed to date, namely Cased and Perforated (C&P) and standalone Wire Wrap Screens (WWS), along with a subset of a three zone Smart well completed with premium sand screens. The comparison focuses on 4 main areas;Well LongevityCompletion Efficiency (skin)Injection Conformance (Near Wellbore)Performance of single and multi-zone injectors The WWS screen performance is further subdivided by clean-up technique of which there are currently five;Backflow Oil Based Mud (OBM)Bullhead Oil Based MudBullhead Water Based Mud after spotting BreakerToe Fracture using External Casing PackerDisplace OBM to Solids Free OBM and bullhead A variety of data will be presented as part of the comparison including, PLT Data, MDT Data, PFO Results, Hall Plots, UCS Data. A simple set of criteria is presented to select when C&P or sand screens are viable completion solutions. Introduction Water Injection (WI) completions in a sand control environment have recently gained a higher profile within the West of Shetlands, in particular, and the industry in general. No clear concensus would appear to have been reached as to what the optimum completion design should be and a variety of completions have been installed throughout the industry. Areas causing particular concern are well longevity and near wellbore injection conformance, both of which are directly linked to producer performance and maximizing reserves recovery. This study presents the range of injection completions that have been installed in the 29 injection wells drilled to date in the WoS fields. Areas that will be examined are completion design parameters and how they are derived, completion selection, impact of drilling fluid conditioning, formation damage, well clean-up and completion performance in terms of completion efficiency, injection conformance and life of well. Background to WoS Fields and Area The Foinaven, Schiehallion and Loyal fields are located in blocks 204/19 and 204/24a (Foinaven) and 204/20, 204/25a, 204/25b, 205/16 and 205/21b (Schiehallion and Loyal) which lie approximately 190kms West of Shetlands, in water depths ranging from 350 – 510m.

Optimization of Well Performance in a Selective Subsea Sand-Control Completion, Offshore Nigeria

“…6). Production rates had to be adjusted to prevent catastrophic sand-control failure, as any subsequent intervention would be at significant expense (King et al 2003;Roy et al 2004;Price-Smith et al 2003) It appeared that productivity and well-integrity issues were interlinked, and that the initial LCM system had to be modified.…”

Optimization of Well Performance in a Selective Subsea Sand-Control Completion, Offshore Nigeria

“…However, considering that the LCM damage was plugging the screen area, the filtering medium erosion rate was greatly exceeded for the most damaged zone ( Figure 6). Production rates had to be adjusted in order to prevent catastrophic sand control failure, as any subsequent intervention would be at significant expense 5,6,7 .…”