Abstract

The gaint oilfield offshore Abu Dhabi was discovered in 1963 and came online in 1967. Horizontal drilling was introduced in 1989 to enhance recovery efficiency, leading to a large stock of horizontal wells to date. With the maturation and depletion of the field, areas of high, non-associated gas saturation have developed, and subsequent breakthrough to the horizontal production wells have resulted in high GOR that is above the shareholder's guideline. Many wells have been shut in due to high GOR.

Controlling uneven production and early gas breakthrough are the main challenges to achieving target production and maximum hydrocarbon recovery. Inflow control devices (ICDs) create additional pressure drop to balance the production flux, but cannot restrict unwanted effluents ‘gas/water’ once they break through.

The Autonomous Inflow Control Device (AICD) is an active flow control device that delivers a variable flow restriction in response to the properties (viscosity) of the fluid flowing through it. Gas flowing through the device is restricted more than oil. When used in an oil well segmented into multiple compartments, this design prevents excessive gas production when gas breakthrough occurs in one or more compartments.

An evaluation of remedial advanced completion methods was conducted to select the best method of recompleting the shut-in wells and restoring oil production while controlling gas breakthrough. The solution must not only control gas production from zones of the well with high gas saturation now, but must be able to react to future increase in gas saturation in other zones as depletion continues.

The "levitating disk" style AICD is ideally suited to this challenge, with the ability to greatly restrict the production from zones with high gas volume fractions. Modeling has indicated that total GOR can be reduced by 40% and total gas production reduced by over 60% compared to an open hole completion.

This paper illustrates how AICD technology can enable operators to re-activate wells shut-in due to high GOR. This paper also describes a systematic approach for modelling flow in horizontal wells with AICD's, and presents an evaluation comparing different completion technologies used to control excessive gas production and maximize oil recovery.

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