Success Story of Optimization Low-Quality Reservoir in “R” Field at WK Rokan by Deliver Inclining Field Production Performance

Abstract

Improving recovery in complex multilayer reservoirs of the mature oil field is one challenging task, particularly for those comprising various reservoir qualities with lateral heterogeneity characterization. Rigorous evaluation is required to define the best approach for production from the reservoir level into wellbore completion strategy. The sand with high quality would have significantly distinct flow performance compared to low quality with low permeability, which impacts artificial lift and perforation strategy design.

Some common issues found were low rates, crossflow due to commingling perforation of contrast reservoir quality, where low-quality one could not contribute fluid production that sometimes by pressure difference block or permeability contrast. This paper undertakes this issue and discusses a case study of "R" field optimization strategy to improve production in the low-quality reservoir.

“R” field is in primary recovery and characterized by two types of sand, high quality-permeability sand (HQ) and low quality-permeability sand (LQ). Most of its production comes from the HQ ("MT_R" and "BT340") and currently contributes to high water cut. On the other hand, oil from LQ with lateral permeability variations is unable to be produced optimally, especially when LQ is comingle with HQ, and opening LQ itself will be difficult to deliver fluid production. Lookback show LQ has low PI and is only able to produce with fracturing methods or commingled with HQ Sand.

The full-field subsurface evaluation was conducted including detailed rates by reservoir perforation to acquire and confirm alignment between production and geological data, for instance, pay and permeability data. It has resulted in a new workover strategy to optimize "R" field including commingling several LQ, and reactivation of LQ at long-term closed wells.

Pilot tests of commingling several layers of LQ usefully added fluid production with a low-rate pump and proved to successfully deliver a good workover result. Pilot tests were conducted at R#07, R#17, and R#39 with average fluid production of ~550 BFPD. The 1st batch workover produced oil gain ~300 BOPD and reduced fluid by 1,800 BFPD. The strategy has gradually been applied throughout the “R” field following lessons learned and success workover.

The new strategy has been implemented in three perforations and six reactivations. The collaborative effort successfully improves underperforming wells and puts the long-term closed wells back to life. It delivers inclining field production performance with incremental oil up to 943 bbl/day, water shut-off ~4,500 BFPD from active wells with >70% success ratio.

Bypassed oil from the LQ reservoir can be optimally produced by commingle several layers of LQ using a low-rate pump. Added value not only optimizes the underperformed wells but also better utilizes idle wells by unlocking the reactivation opportunities. This strategy has the advantage of delivering R2R2P through simple workover with cost-effectiveness.