Abstract

Discovered in 1944 and placed on production in 1952, Minas is a world class field that has produced 4.27 billion barrels of oil to date, a recovery of ~51% of OOIP. Current production average is 130 MBOPD and 5600 MBWPD (97.7% water cut). Primary production was supported by a weak aquifer until the early seventies when Caltex Pacific Indonesia (CPI) initiated the peripheral water flood (PF) for pressure maintenance purposes. Following the peripheral flood CPI initiated pattern water flood (PWF) in 1993 using a 71 acre inverted 7-spot pattern program. The initial results of the pattern water flood were encouraging.

Recently Minas started to experience a steeper production decline and higher operating costs raising questions about the waterflood operation. Minas strategic business unit (SBU) initiated a waterflood optimization study to identify, field-test and develop a comprehensive reservoir management strategy that will improve recovery, stabilize production and reduce the field operating cost. The main challenges facing Minas today are: increasing water production, high water cut, escalating power requirement and cost, water disposal, capacity of existing facilities, increasing reservoir pressure, inadequate vertical and horizontal sweep efficiencies and steep production decline.

This paper outline the asset management strategy developed to address the above challenges with creative solutions:

• Shift from commingled to single zone completion to improve vertical sweep efficiency, reduce water recycling and eliminate cross-flow. Water production was reduced by 40% from a single gathering station.

• Water shut-off efforts over the past 10 months resulted in $10 million saving in annual operating costs

• Build a fine-scale geostatistical model to support a flow simulation model used to test various alternatives to improve areal sweep efficiency through pattern realignment.

• Improve completion efficiency through application of saturation logs, under-balanced perforations, washing perforations and dual down hole pumping system.

• Reduce the reservoir pressure from 550 to 325 psi to improve flood efficiency.