Abstract

The Offshore sandstone reservoirs in Saudi Arabia are characterized by high production potential due to the nature of the reservoir, consisting of clean coarse sand with active bottom water aquifer and in some areas, a gas cap as drive mechanisms.

In recent years, horizontal wells have replaced conventional wells due to their improved deliverability and recovery efficiency. The initial completion method selected by Saudi Aramco for the horizontal wells was mainly cased hole cemented with selective perforation strategy. This completion method was troubled by non-uniform flow profiles, which drastically shortened the well production life reducing the benefit associated with the planned horizontal wells.

This paper will describe the concept of an innovative openhole completion strategy that has increased well productivity and recovery compared to past horizontal completion methods. The paper will show the evolution starting with the use of openhole completions completed with passive Inflow Control Devices (ICD) allowing production optimization by delivering uniform inflow along the entire horizontal section. The paper continues to discuss the benefits associated with the integration of the passive inflow control system with artificial lift (In situ gas lift and Electrical Submersible Pump (ESP) and finally reveals plans to couple passive inflow control with active intelligent well completion technology for multilateral wells. Actual field data will be presented to validate findings and support conclusions.

Background

Three major offshore fields, Z, M and S, in Saudi Arabia, are sandstone reservoirs with good petrophysical properties. These fields have been producing since the mid-fifties, and the production mechanism is a strong water drive. Natural depletion and proximity of the water created a new challenge for sustained production. Horizontal wells were introduced in the early 90s to optimize new well completions.

Prior to 2003, most horizontal wells drilled in the sandstone offshore reservoirs were completed as cemented and perforated liner completions. This methodology would allow a selective perforation strategy; however, the method proved to be less then optimal as only a small fraction of the net pay encountered produced. This resulted in early water or gas break through and lost well productivity. In addition, the associated water production resulted in the initiation of sand production from the wells.

In 2002 Saudi Aramco introduced two completion technologies in order to increase completion efficiency. The new completion methodology would have to be open hole. One completion would be an expandable sand screen while the other would be a stand alone premium screen with passive inflow control devices and mechanical openhole packer.

The introduction of these new open hole completion technologies has reduced the time required to complete the well with an overall cost reduction, mainly due to saving rig time.

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