This paper presents a production log which revealed, for the first time in Husky's experience with horizontal wells in the Rainbow Area, the existence ofcrossflows along an openhole horizontal wellbore. The production log indicatedthat the occurrence of crossflows along the wellbore effectively reduced theproducing well length to less than 25% of the total length. The thrust of thispaper describes how a sound understanding of pool geology and reservoirheterogeneity, adequately transcribed to a numerical simulation model todetermine the effect on fluid flow, is required to investigate and account forthe crossflow phenomena. A horizontal well simulation model was constructed totest a number of hypotheses on how the crossflow was created. Through the veryprocess of re-creating (history-matching) the observed crossflow behaviour withthe model, a comprehension of the most likely factors causing the crossflow wasderived. A number of sensitivity runs was then made with the crossflow- matchedmodel to determine ways of countering the crossflow. Based on the modelpredicted results, a field strategy was ultimately developed with the potentialto eliminate the crossflow and restore the horizontal well to its truecapability.


The Rainbow Keg River "A" Pool is one of the seven mature verticalhydrocarbon miscible floods operated by Husky Oil Operations Ltd. in the Rainbow Field as shown in Figure 1. These mature floods are typified by a thinoil sandwich overlain by solvent/gas and underlain by water. Under such adverseexploitation conditions, Husky has successfully redeveloped these reservoirsthrough an aggressive program of horizontal drilling with the objectives ofminimizing gas coning and/or channeling, increasing oil productivity anddrainage area, and maximizing oil sandwich recovery. The technical aspects ofdrilling the first horizontal well into the "A" Pool has been described.

Even though the eleven horizontal wells drilled to date by Husky havesignificantly improved pool productivities and economics, there is no definablecorrelation of well productivity to total producible openhole length. One ofthe technical challenges in horizontal well application is to understand thefactors which cause non-uniform inflow along a horizontal wellbore, and wherepossible, eliminating those deterrents to the ideal of uniform inflow.

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