Case study: High temperature DBB valves for steam injection - A common enhanced oil recovery method

Mature oil fields use enhanced oil recovery (EOR) to boost production. Steam injection is an EOR technique widely used in the Middle East. High temperature steam is injected into the well to heat up the subsurface oil. The oil production from a heated well increases due to the effects of lower viscosity, vaporization and thermal expansion.

Metal-to-metal seated ball valves have traditionally been used for this high temperature application. These valves can be difficult to procure as they are made from special alloys and require a specialized coating process.

Steam injection a common enhanced oil recovery method

Boosting?recovery?from aging?oil fields?is a?major challenge?in oil production. As production starts to taper off, oil companies must employ?enhanced oil recovery (EOR) techniques.?Using EOR technology, production can be increased to keep the field economically viable.

EOR can help?extract up to 60% of a reservoir’s oil, compared to 40% using primary and secondary extraction methods.

In the Middle East,?steam injection?has been?successfully used as an EOR technique?for the recovery of heavy viscous oil. Steam is injected into the reservoir to?heat up the subsurface oil.?The process boosts recovery due to?viscosity reduction,?vaporization?and?thermal expansion?of the oil.

Traditional method of steam generation

Traditionally,?natural gas?is burned to produce the EOR process steam. The oil and gas industry, however, is under?increasing public and regulatory pressure.?Worsening?climate change?blamed on greenhouse?gas emissions?from the use of its products.?The additional use of?fossil fuel, during the?extraction process, exacerbates the?environmental?concerns.

Solar thermal energy for steam generation

Solar thermal energy for steam generation?is a?clean and environment-friendly alternative?to burning natural gas. This?method uses mirrors?to?reflect and concentrate solar radiation?on to receivers that convert solar energy to heat. The?clean energy?is then used for the?EOR process steam generation.

The?solar thermal approach?not only reduces the carbon footprint of the extraction process but also?lowers the cost of extraction.

An increasing number of gulf state oil companies are working on?replacing natural gas-based steam generation.?A?solar steam process?is part of their?environmental agenda.

Solar steam generator at the Miraah Solar Plant in Oman

A prime example is the?solar steam generator?at the?Miraah Solar Plant in Oman?which is one of the?largest solar plants?in the world. Boasting a?solar thermal capacity of 1,021 MW, the plant has a daily?steam output of up to 6,000 tons.?That translates into annual?gas savings of 1.6 TWh?and annual?CO2?emission savings of 300,000 tons.

The?6,000 tons of solar steam?generated daily at Miraah constitutes a substantial portion of the?EOR steam requirements?at the?Amal oilfield?operated by?Petroleum Development Oman?(PDO).

The steam EOR increases the well productivity at Amal by 300%.

High temperature requirements for steam injection

The?design temperature for steam injection?wells is typically in?excess of 400° C.?At these high temperatures, the?hardness of the valve material is reduced?and its?fatigue-resistance is compromised.

Small?cracks?may?appear?which can propagate across the section?causing failure. Valves with O-rings and thermoplastic seals are unsuitable for use in this temperature range.?High-temperature, high-pressure applications?demand that valves have a?specialized design and construction.

Metal-to-metal seated ball valves, with a?larger bore?and?fire safe graphite sealing, are generally?used as isolation valves?in?steam EOR application. These valves are constructed from?special alloys?and are?protected with a heat, corrosion?and?wear-resistant coating/cladding, applied using a specialized process.

Some valve manufacturers can take several weeks to supply such valves. A ball-set (ball + seat) must?be ordered?from third-party suppliers.

?In the event of an?unplanned shutdown, procurement and replacement?of these special purpose valves can?become a challenge for the maintenance team. The cost of using these valves can be high both, in terms of the?procurement cost, and the?production loss?suffered while?waiting for a replacement?to arrive.

High temperature Double Block and Bleed valves for steam injection

Maintenance and safety protocols?demand?periodic service and replacement of critical valves. In?steam injection?wells,?pressure transmitter / pressure gauge?(PT/PG)?isolation valves?are of critical importance.

Based on customer demand, AS-Schneider has developed a?bigger bore?globe type needle valve?in?Double Block and Bleed?(DBB)?configuration?that is ideally suited to this application.

High temperature DCZ series of DBB valves

For?high temperature?and?pressure applications, such as?steam EOR, AS-Schneider offers the?DCZ series of DBB valves. The valves are designed with a?large 14mm bore,?needle type block in DBB configuration?that is rated up to 550° C.

It is a?compact and tough design?built to last in?extreme applications. The?innovative design?of the?valve head allows smooth low-torque operation?and gives the valve a?long service life. The?standard rating?of AS-Schneider DBB valves is?420 bar?but valves can also be produced with a?689 bar rating for high-pressure applications.

DCZ series contains monoflange and dual flange models

The?series contains monoflange and dual flange models?with specialized process and instrument designs. The valves are readily available from the company as they are?faster to produce?and?do not require special third-party components.

High temperature DCZ series at the Amal oilfield

AS-Schneider?valves have been installed at the Amal oilfield?which?uses steam?from the?Miraah solar thermal facility for steam enhanced oil recovery.

The valves have been in service for more than?2 years?and have?received excellent reviews?from?site and field engineers. In the word of one happy engineer:

This is one of the best products we have ever used.

Happy field engineer

Image Source: ??Wikipedia,?PDO,?Matrivgraphics (Fivver) & AS-Schneider