Chevron, San Ardo Produced Water Treatment

The Client's Needs

The San Ardo project involves treatment of produced water for the purposes of discharge to recharge basins and production of Once Through Steam Generator (OTSG) make-up water. The raw produced water temperature is 200°F, and it contains about 25 ppm free oil, 80 ppm TOC, 240 ppm silica, 26 ppm boron, 240 ppm hardness and 6,500 ppm Total

Dissolved Solids (TDS). The project goal was to reduce the feed water TDS to less than 510 ppm and boron to less than 0.64 ppm for recharge basins discharge, while achieving 75% water recovery across the treatment system and minimizing the volume of produced water requiring re-injection. For the purpose of OTSG make-up, the project goal was to reduce the feed water hardness to less than 2 ppm as CaCO3.

Our Solution

The treatment process includes a common pretreatment step for free oil removal followed by OPUS® technology to achieve the discharge water quality and a Series Softening System for generation of OTSG make-up water. The free oil removal system consists of an induced gas flotation system and a PowerClean walnut shell filtration system to reduce the free oil to less than 0.5 ppm. The OPUS® technology consists of multiple treatment steps such as heat exchange, degasification, chemical softening, media filtration, ion exchange softening, and a double-pass RO system to meet the effluent water quality requirements. The solids generated from the system are dewatered and disposed in a landfill. The Series Softening System involves two-stage strong acid cation softeners to reduce the hardness in the feed water to achieve the water quality specification.

Scope of Work and Technologies

The San Ardo project involved process design, basic engineering, equipment procurement, and construction management. The advanced water treatment system includes the equipment shown in the process diagram below and is operated by Veolia Water North America.

 

Performance

Constituent Produced Water Double Pass RO Permeate Final Treated Effluent Effluent Specification

TDS, PPM

6,500

 76

120

510

SODIUM, PPM

2,300

 43

 43

85.0

CHLORIDE, PPM

3,400

 Non-Detect

 11

127.5

SULFATE, PPM

133

 Non-Detect

 120

127.5

NITRATE, PPM

10.0

 Non-Detect

 Non-Detect

4.25

BORON, PPM

26.0

 0.24

 0.24

0.64

pH, S.U.

7.5

 10.7

 7.0

6.5 - 8.4

*Based on initial 12 months of operation

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