| Abstract |
When a reservoir is sufficiently permeable, it is able to supply fluid at a greater rate than that which the well is able to deliver to the surface. Under such conditions, reservoir pressure drawdown is usually insignificant and variations in wellhead pressure during discharge are associated with changes in the wellbore frictional pressure drop. This phenomenon is commonly termed "wellbore controlled flow" as it occurs when friction effects in the wellbore are substantial in relation to the available pressure drop from the reservoir to the wellhead and in relation to reservoir pressure drawdown. Apart from reservoir permeability and its effect on pressure drawdown, the other factor that influences wellbore controlled flow is the static reservoir pressure. When well inflow pressures are low the effects of friction in the wellbore are comparatively more restrictive as the fictional pressure drop becomes significant with respect to the overall pressure difference from the reservoir to the wellhead. It follows that when wellbore controlled flow occurs, increasing the wellbore diameter should greatly improve well output characteristics. This study is aimed at assessing the effects of wellbore diameter on the output of wells in the Eburru Geothermal Field, Kenya. Measured well dimensions and estimated reservoir parametersat Well One were used to assess the improvement in well output expected from large diameter wells. The calculations were repeated for several assumed values of reservoir permeability-thickness product in order to investigate its importance in controlling well output improvement. |