Rejuvenating Late Life Field Opportunitiies at the Greater Sirikit Oilfied: Effective Produced Water Management and Facility Upgrades at the Lan Krabue Well Site L Processing Facility
Authors: Charoensuk Pacharapol , Watanapanich Supaluck , Lertrojanachusit Nattapong , Nitayaphan Saranee 
Published: February 2023

The Greater Sirikit Oilfield (GS1) is an onshore asset located in Kamphaeng Phet, Thailand. Waterflooding accounts for over 64% of the crude output in this field. Consequently, the water cut at GS1 continue to escalate rapidly with the current level approaching 70%. To unlock additional processing capacities, the Lan Krabue Well Site L (LKU-L) Processing Facility is being upgraded with primary and secondary water treatment units to adequately manage and dispose the rising produced water volumes.

The LKU-L Processing Facility upgrades include the following primary/secondary water treatment units:

Desander & deoiler hydrocylones to remove solid particles and recover free-oil droplets. Dissolved Gas Flotation (DGF) package to reduce suspended solid/oil concentrations in produced water used for waterflooding.

Throughout the execution, project requirements were continuously refined to value past design and operational pain-points through multiple, collaborative feedback sessions with the end-user operations team. Lessons learned from the successful pilot DGF/DAF units at GS1 were also methodically scrutinized to improve equipment design, process scheme, and operation/control philosophy ensuring the new unit consistently achieve performance specifications.

The new desander and deoiler hydrocyclones at the LKU-L Processing Facility will condition the produced water stream for secondary treatment by reducing the solid and free-oil concentrations to below 200 mg/L (&gt;95% removal for particles &gt; 20 microns) and 100 ppm,v respectively. The DGF unit will then further decrease the total suspended solids and oil-in-water contents below 20 mg/L (&gt;80% removal for particles &gt; 5 microns) and 25 ppm,v respectively. Improvements in the quality of disposal water used for waterflooding will mitigate injectivity concerns in up to 72 injection wells resulting in a cost-savings of $7.2 million. Moreover, gross production entering the LKU-L facility can also be increased by 18,400 bpd (+134%) which will generate an additional 5,520 bpd of crude (+$98.4 million/year revenue).

Several technical enhancements were also contrived to tackle existing operational concerns and brownfield modification challenges:

Revamp existing process design and control schemes to improve the deoiler hydrocyclone performance. Unique partitioning of the desander & deoiler hydrocyclones to allow flexible turndown capacities. Revisit the retention time of the DGF unit to improve solid and oil removal efficiencies. Online weir adjustment functionality in the DGF vessel to facilitate performance optimization. Installation of sand-jetting system in an existing separator without hot work

The design enhancements for the primary/secondary water treatment units at the upgraded LKU-L Processing Facility are being liberally replicated and implemented at three other similar processing facilities in GS1. Furthermore, the design improvements of the DGF unit can serve as a best-practice guideline for similar units in PTTEP and for other oil and gas operators. Prioritizing operational challenges is also an excellent practice that help cater requirements to actual end-user needs.