An Implementation of Reservoir Connectivity Study to Increase Oil Performance in Petani Waterflood Expansion Project

Abstract

Petani field is located in Central Sumatera Basin was discovered in 1964 and operated by PT. Chevron Pacific Indonesia (PT. CPI). Petani field initially developed as primary production since 1968. This field reached peak production with 101MBOPD (Million Barrel Oil per Day) in 1971. By over the time, since 2008 with purpose to maintain the production rate and maximize the recovery of this field, the Asset Optimization Team executed a waterflood pilot project to inject a single sand. After looking the look back for this pilot project, the good performance from this pilot waterflood project was trigger waterflood expansion project to inject other reservoirs started in 2015. Petani field has complex stratigraphy and structural framework that leading to the compartmentalization. Lookback of pilot waterflood has been used to identify the room for improvement of the execution phase on expansion waterflood. It’s identified that reservoir connectivity as the critical factor of waterflood performance. Injector and producer wells need to have good alignment strategy. An increased understanding on facies and fault behavior framework have shown that flow of injection follows newly-defined flow units in estuarine environment reservoir. The implementation of integrated subsurface and engineering analysis is expected will lead to good performance of the expansion waterflood field. The biggest challenges during waterflood implementations are minimize the declining production and managing injectivity at the reservoir level since the field has declare zero water discharge. Go-forward the optimization strategy focusses on better reservoir management to maximize the recovery. This paper focus on the technical analysis of defining the vertical and lateral connectivity practically applied for injector-producer alignment. Detailed study has been done as an efficient approach to evaluate waterflood connectivity performance in complex compartmentalized reservoir. The objectives are to increase oil production and manage mature fields, and also to enhance ultimate recovery. It is also robust approach to get better understanding of detail reservoir characterization, reservoir internal architecture, reservoir distribution, pressure monitoring, and water flood sweep peripheral efficiency. The evaluation of reservoir engineering involved surveillance data such as spinner, pressure, injectivity test and cased hole log to minimize subsurface uncertainty. Enhanced performance has been achieved by implementation of integrated reservoir connectivity study. This study led to a robust understanding of injector-producer alignment. The results have shown significant increase oil field performance leading to an additional reserve about 2.2 MMBO since waterflood expansion started, improve decline rate from 16% to 14%, and increase production of 1,300 BOPD from the baseline. This study is beneficial for further field development of waterflood pseudo pattern and enhance strategy for reservoir management e.g. workover potential and future infill well candidates (vertical and horizontal wells). By having the creative and diligent integrated subsurface and engineering analysis provide an excellent alternative optimization strategy for the complex waterflood field. This methodology can be applied for other waterflood field that has similar conditions. Integrating subsurface assessment, surveillance and engineering data proven improved performance and recovery of Petani field. The extensive application of the reservoir connectivity appears to be an important tool to economically extend life of this mature field, achieve high recovery, and maintain production decline.

AAPG Datapages/Search and Discovery Article #90354 © 2019 AAPG Asia Pacific Technical Symposium, The Art of Hydrocarbon Prediction: Managing Uncertainties, Bogor, (Greater Jakarta), Indonesia, August 7-8, 2019