In recent years, many operators in the oil and gas industry have moved in the direction of horizontal drilling, as horizontal drilling has proven to be a more efficient production method than trying to move hydrocarbons into vertical wellbores. For the last several years, a major Middle East operator has been leveraging horizontal drilling technology to maximize oil recovery. Although the use of horizontal drilling technology has resulted in significant production increases, this operator saw that recovery efforts were somewhat hampered by water breakthrough in the horizontal openhole section of some wells. Unwanted water production is a problem for many operators, not just because of water content and reduced lift efficiency, but also because of the cost of water handling facilities and the cost of disposing of or re-injecting the unwanted water.

This paper describes how the problem of water breakthrough is being alleviated by solid expandable tubular technology. This paper also describes the development of the solid expandable tubular technology solution for openhole water isolation from the initial conception and preliminary development, through the first remedial applications, to the extension of the solution for deployment during the drilling phase of the well. The paper cites case histories of each of the stages of this development and discusses future enhancements of the technology to further optimise this solution.

Mechanism and Impact of Water Breakthrough

Water breakthrough presents a major challenge in the production management of reservoirs relying on aquifer support or water injection to sustain reservoir production pressures. The ideal of a completely homogeneous and consolidated reservoir still requires careful placement and production management of well bores to maintain a uniform sweep of the desired reservoir fluids into the wellbore without water bypassing the hydrocarbons and flowing into the well in preference.

In heterogeneous, fractured formations, the problem becomes substantially more complex. Water is far less viscous than oil and flows more easily through the formation. If high permeability channels are encountered, these are quickly swept of oil and subsequently provide a conduit for direct communication between the aquifer, or the injection point, and the production face. It is far easier for the low viscosity water to flow through the swept high permeability channel than it is for the water to push the higher viscosity oil through the surrounding low permeability matrix. Once water has broken through, a disproportionate volume of fluid flows in through the water zone, relative to the oil leg, so that, for a given production rate, the recovery of oil is now substantially reduced. The higher density of the water, in comparison to the oil, increases the effective density of the produced fluid, and so reduces the natural drawdown available on the formation. This can result in either a reduction in gross production volumes, or a requirement for increased artificial lift to maintain production.

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