The Relative Importance of Drawdown and Depletion in Sanding Wells: Predictive Models Compared With Data From the Statfjord Field

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractExperience of sand production from the Statfjord field has been systemized to be able to predict the effect of drawdown and depletion on sand production. The aim of the study is to determine how reservoir pressure depletion will influence the sand production and to determine how sand production will influence the maximum liquid production rates. Most wells produce according to a maximum acceptable sand production criterion. Field data based on more than 300 maximum acceptable sand rate tests have been systemized by fitting those to an empirical criterion. For a better determination of the parameters, sand production histories of four wells have been analyzed in detail.To understand more about the mechanisms underlying the sand production, the field results are compared with four different models. This work concludes that the behaviour of sanding wells at Statfjord can be described by a concept of two sand production regimes, one controlled by shear failure and the other controlled by rate.Finally the empirical model is used to extrapolate the field experience to low reservoir pressures related to the planned deep depressurization. The results show that sand production will limit well production rates unacceptably for most formations and that downhole sand control is needed to secure high production rates during the late-life development of the field. IntroductionThe Statfjord field is a large oil field located in the Northern part of the Viking Graben and straddles the border between the Norwegian and UK sectors. The field has been in production since 1979 and has utilized both water flooding and gas injection for secondary recovery. To date over 65% of the STOOIP has been recovered. The producing reservoirs (Brent and Statfjord) consist of weak to intermediate strength

Drilling and Completion Challenges of the Statfjord Late Life Project

“…If sanding volumes were to increase and significantly limit well offtake rates, this would have large consequences on the economics of the late life project. The operator performed an extensive rock mechanical study and this concluded that liquid production rates from C&P wells would likely need to be reduced to unacceptable levels during the pressure depletion in order to maintain acceptable sanding volumes and erosion rates 10 . This led the operator to the conclusion that some form of mechanical sand control was required for the late life wells; with the understanding that this strategy would lead to an increased sensitivity to downhole scaling 9 and a requirement for preventative scale treatments.…”

Predicting Deepwater Well Behavior

“…This limit may vary depending on well completion size and design, and is different for a subsea well to that of a TLP well. 2 Well failure Scenario…”