The Effects of 5" Slotted Linear Extensions on Production and Reinjection Wells

Abstract

This report investigates the eflects of using small diameter (5ö) slotted liner extensions on the injection capacity and discharge capacity of standard size injection and production wells.

There have been quite a number of instances at Philippine National Oil Conipany Energy Development Corporation (PNOC-EDC) where changes to the prograinmed well configuration have been made during the course of drilling deep wells. This is due to a variety of hole problems encountered before reaching the progronrmed total depth. In tlie worst cases, this necessitates drilling of a smaller diameter hole extension to reach the progranrmed total depth where the major geological structure is projected to be intersected. The well then consists of hvo sizes of slotted liner, a 7-5/8ö liner and a 3 IÆ slotted liner extension with the major permeable horizon intersected by the siitaller size liner. The eflect of using the 5 ÆÆ slotled liner extension has been investigated using the PNOC-EDC injection capacity estimation method for injection wells and the Wellsini Wellbore Simulator for production wells. A significant drop inflow capacity of the well is identijied as a result of using the hvo liner (7-5/8 and 5 ÆÆ slotted liner extension) conjguration against the standard 7-5/8 ÆÆ slotted liner. Cnpacity loss is more severe in high pernieabili[v wells, and depends on the length of the small diameter slotted liner.

A simple correlation is provided to detennine the percentage of capaciv loss in reinjection wells, based on iiljectivity data obtained afler drilling. An attenipt was also made to correlate productivity losses to initial injectivities but this I~WS unsuccessftil. probably becnuse of tlie more complex nature of two-phase fluid in tlie wellbore.