New High Temperature Heavy Oil Testing Cell
Heavyoilinfo.com spoke to Tara Engel, fluid analysis product champion at the Schlumberger Oilphase-DBR technology center in Edmonton, Alberta, about a new heavy oil PVT laboratory testing cell that has improved mixing capabilities and is rated for temperatures up to 250 degC. Tara Engel is a petroleum engineer, currently focused on the Schlumberger RealView live solids deposition cell and heavy oil flow assurance measurement services.
Figure 1. New high temperature heavy oil PVT cell developed at the Oilphase-DBR technology center in Edmonton
Understanding heavy oil fluid properties is fundamental for deciding the best extraction, production, and processing methods for an asset. Laboratory testing of fluid samples can provide valuable information about the thermodynamic and physical properties of a company’s heavy oil reserves. However, the laboratory equipment must be able to recreate pressure, volume and temperature (PVT) conditions that are representative of the subsurface environment during recovery. In the case of heavy oil, this may involve high temperatures and pressures related to recovery processes such as the injection of steam.
Until recently, Schlumberger laboratory testing systems were capable of handling temperatures up to 175 degC and mixing fluid samples with viscosities around 300 – 500 cP. This was insufficient to simulate the real-world production conditions of many heavy oil reservoirs.
In December 2008, Schlumberger commercialized a new high temperature heavy oil PVT cell, developed at the Oilphase-DBR technology center in Edmonton. The new equipment is rated to 250 degC. No other system has a higher temperature rating. It also has a strong mixer cap that can handle viscosities up to 5,000 cP at test temperature. The new cell also has the benefit of being fully visual, enabling better analysis of gas liberation volumes.
Some conventional PVT cells mix the fluid too slowly to mix the whole test volume, leading to underestimation of the bubble point. The better mixing provided by the new equipment reduces test time and enables more accurate measurement of saturation pressures. In addition, several conventional systems use mercury for the mixing process, which in some circumstances can create an emulsion and encourage asphaltene dropout. The mixing system in the new Schlumberger heavy oil testing cell is mercury free.
In addition to the Edmonton facilities, Schlumberger has installed new heavy oil testing cells in Brazil, Houston, Dubai and, later in 2009, Mexico.
The oil cell itself is only part of a complete service. Many field samples are contaminated by water and solids, leading to incorrect bubble points and viscosity measurements. The Schlumberger testing service starts with cleaning of the samples to more realistically represent the heavy oil in the reservoir.
The new heavy oil cell is used to test both stock-tank and live samples. Schlumberger offers services to collect live homogenous, single-phase heavy oil samples in both openhole and cased-hole environments. Acquisition systems use pressure-compensating technology to assure sample integrity and no loss of gas. Dissolved gas can dramatically affect the behavior of oil, so live samples are generally much more representative of subsurface conditions than stock-tank samples.
Assuring the flow of produced fluids can represent a major share of the cost of a heavy oil production system. Asphaltene precipitation, wax, hydrates and emulsions can block or slow production, requiring expensive and time consuming intervention. Schlumberger provides services to predict the conditions under which solids are likely to precipitate, when emulsions will form, and ways to break them up. Studies can also simulate the effectiveness of adding solvents to reduce oil viscosity.
Accurate testing with representative fluid samples and subsurface conditions can improve recovery efficiency and improve flow assurance. Tara Engel is confident that heavy oil operators will recognize the value of the new PVT testing equipment and collecting live samples.
Author's Bio
Tara Engel graduated from the University of Alberta with a bachelor’s degree in petroleum engineering. Since 2000, she has worked as research project assistant, software support engineer, and later as product and service engineer for Oilphase-DBR Technology Center. Tara has experience in PVT equipment and software sales and support, and is now fluid analysis product champion for Schlumberger.
