Publications

Rapid water breakthrough due to water coning in high permeability sandstones has a negative impact on oil recovery. Development wells in PN Field, which is located in the Central Sumatra Basin of Indonesia, has experienced rapid water breakthrough in oil producing wells. The reservoir unit under development is thick, blocky, high permeability sand has with very strong aquifer support. Despite many years of production in more than 50 wells, the reservoir pressure has declined no more than 400 psi from original pressure. The current water-cut is 93%, but the recovery factor is less than 30%. The main reason for the low recovery factor is premature water breakthrough resulting in by-pass oil. Production behaviour for typical vertical / directional wells is characterized by high rate, dry oil production, followed by water-cut increase to 85% within a month after initial production. To mitigate the rapid water breakthrough, horizontal wells have been proposed to mitigate effects of water coning. However, water coning and rapid increase in water-cut is still expected for the horizontal wells given that drawdown is typically concentrated in the heel section of the well and/or in high permeability intervals. Thus, Inflow Control Devices (ICD) have been added as an additional mitigation against water coning and rapid water breakthrough. In practice, wells are dived into segments in the producing interval with a separate ICD completion in each segment, which adds ability to control the segment pressure draw down. This in turn allows a balance of drawdown to be distributed over the length of the completion interval, which helps to avoid localized high drawdown that leads to water coning. Pilot well PN-R1 is the first test of a horizontal well with an ICD completion in PN Field. As part of the design phase, a simulation model was used to compare well performance in a horizontal with and without ICD, the results of which indicated economically viable incremental reserves with use of ICD. Simulation was also used for ICD design (e.g. numbers of ICD, nozzle size, and swell packer placement), and to identify the optimum operating well condition. Actual well performance has demonstrated successful results from ICD application, including: 1. Reduced initial water production and gentle water-cut incline compares to vertical / directional wells. 2. Increased early recovery compared to vertical / directional wells given higher fluid rate enabled by the horizontal well