Case+Studies

==__Case Study with SAGD__ [1] ==

SAGD is one of the most commercialized in-situ unconventional oil sands technologies. This report focuses its attention towards SAGD and using it as a case study to compare it with the THAI process. A strong similarity between SAGD and THAI use horizontal well technology and heating viscous bitumen to extract heavy oil that is too deep for conventional open pit mining. This case study shows how THAI technology is really helpful in "greening" Alberta's oil sands. Three main aspects that are to be analysed in this comparative section are recovery, economic, and environmental benefits

**Recovery: [1][2] **

**Improved Recovery Rates** In Athabasca Oil Sands, conventional methods used for extracting heavy oil often have recovery factors less than 10%. Unconventional thermal method like SAGD has a recovery between 20% and 50%. However, THAI technology has demonstrated a recovery of 70-80% through computer simulation, physical modeling and its pilot project in the Whitesands.

**Broader Reservoir Compatibility than SAGD** THAI process can produce oil from reservoirs that are not suitable for SAGD or any other thermal recovery methods. Moreover, THAI process can be used in reservoirs where SAGD or any other thermal recovery methods limited due to factors such as limited gravity drainage, low permeability, and reservoir sizes.

**Used for Enhanced Recovery Methods** THAI can be used as a primary, secondary or even tertiary recovery method. Essentially, THAI can either be used as a combination with other in-situ recovery techniques or used as a primary recovery technique unlike SAGD which is conventionally used as a primary recovery method.

**Economic:[1][2] **

**Economic Benefits** Experimental evidence shows the THAI process is fairly simple to operate and control and more efficient relative to SAGD. "The technology was designed to use ‘off-the-shelf' equipment and facilities – making facilities quicker to build, less costly and easier to maintain."

In larger scale THAI projects, the volume of combustion gases containing a high enough residual energy value that has proved to compensate the start-up and operation costs making it an economically sustainable option. This adds significant benefit over SAGD in its economic and environmental aspects.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">The pilot project in the Whitesands testify the fact that the THAI process consistently produces upgraded oil with substantial decrease in viscosity (light oils with high API gravity) as compared to conventional bitumen (see table 3-1 below). Therefore, less diluents such as Naptha are required to achieve pipeline specifications and less refining is necessary at the surface to transform the oil into final products. As a result, THAI process has a higher value barrel at the wellhead as opposed to SAGD.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 80%;"><span class="wiki_link_ext">Image courtesy of: []

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">**Operating Costs** <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Relative to SAGD, the THAI process requires minimum water (in the form of steam) and natural gas. Since THAI only uses nominal volume of steam at the beginning of the heating process, it is no longer required once air injection has begun. Therefore, by minimizing the use of water handling facilities and the variable costs associated with burning natural gas, THAI projects require smaller capital investment and have lower operating costs than SAGD. As shown in the figure, the production and maintenance cost accrued by SAGD outweighs that of the THAI process. This cost is broken down into the cost associated with steam production, air compression, pipeline transportation and upgrading. <span style="font-family: 'Times New Roman',Times,serif; font-size: 80%;"><span class="wiki_link_ext">Image courtesy of: [|http://s3.amazonaws.com/zanran_storage/nws.chem.uu.nl/ContentPages/2465797051.pdf#page=47]

<span style="color: #0000ff; font-family: 'Times New Roman',Times,serif; font-size: 140%;">**Environmental: <span style="color: #0000ff; font-family: 'Times New Roman',Times,serif; font-size: 80%;">[1][2] **

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">**Environmental Benefits** <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">THAI has several environmental benefits when compared with proven thermal production technologies like SAGD. The main resource in SAGD is water and its is "net water user"; however, THAI process produces water which is in fact clean enough for industrial use or immediate re-injection. As a mater of fact, THAI does not directly consume water, but actually produces it from otherwise unsuitable sources (such as steam generated from groundwater and aquifers). Also, as shown in table and figure energy required for energy invested (denoted as ERE in table 3-2 and figure 3-2) and CO2 emissions are less in case of THAI process. This has significant benefits in both the environmental and economic aspects.

<span class="wiki_link_ext" style="font-family: 'Times New Roman',Times,serif; font-size: 12.8px;">Image courtesy of: [|http://s3.amazonaws.com/zanran_storage/nws.chem.uu.nl/ContentPages/2465797051.pdf#page=47]

<span class="wiki_link_ext" style="font-family: 'Times New Roman',Times,serif; font-size: 12.8px;">Image courtesy of: [|http://s3.amazonaws.com/zanran_storage/nws.chem.uu.nl/ContentPages/2465797051.pdf#page=47] = = =<span style="background-color: #ffffff; color: #3dc93d; font-family: 'Times New Roman',Times,serif; font-size: 120%; vertical-align: baseline;">__ Comparison to a Steam Flooding __ [3] =

<span style="background-color: transparent; color: #000000; display: block; font-family: 'Times New Roman',Times,serif; font-size: 120%; text-align: justify; text-decoration: none; vertical-align: baseline;"><span style="background-color: transparent; color: #000000; text-decoration: none; vertical-align: baseline;">“Upgrading Athabasca Tar Sand Using Toe-to-Heel Air Injection”, is a research paper that provides information about the lab tests done on the investigation of THAI. To investigate dry and wet combustion performance, experiments were done on 3-D physical models that were designed in the lab. The results obtained from THAI and a steam flood test (followed by pure air injection) were compared. These results indicate that excellent ignition and very stable combustion propagation was achieved with THAI as opposed to steam flooding. THAI was also found to be superior to the steam flood test by upgrading the oil to nearly 10 API. Further upgrading of the oil was achieved using CAPRI. The catalyst used in the THAI-CAPRI extension uses the Co-Mo HDS catalyst which boasts the advantage of reducing sulphur and heavy metals content in the produced oil making the THAI environmentally sustainable. <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">The concept of the THAI process is described and illustrated in this paper. To gain a further understanding of the THAI process, Figure 3-3 and 3-4 illustrate this topic.

<span style="background-color: transparent; color: #000000; display: block; font-family: 'Times New Roman',Times,serif; font-size: 120%; text-align: justify; text-decoration: none; vertical-align: baseline;">The main limitations to the steam flood test was that a very large fraction of oil can remain immobile which can only be mobilized and extracted by thermal cracking at higher temperatures (>500 ˚C). This explains why steam injection/flooding did not have high recovery factors like THAI.

Figure 3-3: The concept of toe to heel air injection (THAI) process, image courtesy of reference [2]

Figure 3-4: Mobilised oil draining from narrow zone into exposed section of the horizontal well, image courtesy of reference [2]

<span style="background-color: transparent; color: #000000; display: block; font-family: 'Times New Roman',Times,serif; font-size: 120%; text-align: justify; text-decoration: none; vertical-align: baseline;">Other important conclusions that can be drawn from the laboratory tests are:
 * <span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 120%; text-decoration: none; vertical-align: baseline;">The THAI process allows for controlled stable combustion and faster ignition rates when tested with Athabasca Tar Sand's bitumen in the 3D model test (carried out by Greaves et. al.)
 * <span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 120%; text-decoration: none; vertical-align: baseline;">Very high recovery factors were achieved utilizing the THAI method. Up to 80% of the initial oil in place was recovered. High recoveries were also achieved when THAI was used as a follow up to the steam flood test (that is; cases were THAI was used as a secondary recovery technique).
 * <span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 120%; text-decoration: none; vertical-align: baseline;">The steam flood test required a long period of preheating and was only able to recover 23% of the original bitumen while using a steam to oil ratio of 3. This is a downside of steam flooding, since it uses significant amount of steam. It is also environmentally and economically unfavorable to generate the steam and if the water is not mostly recyclable.
 * <span style="background-color: transparent; color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 120%; text-decoration: none; vertical-align: baseline;">Further upgrading of the produced oil was achieve utilizing CAPRI by 4 API point, as compared to the thermal upgrading alone using THAI.



<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Image courtesy of reference [2].

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Overall, the results from this research paper are a great indications of THAI being successful in the lab which means that it has a great potential of performing well on the field. Mr. M. Greaves and and his colleague has done many other great contributions into researching and introducing THAI.

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<span style="background-color: #ffffff; color: #000000; font-family: Arial; text-decoration: none; vertical-align: baseline;">[1] <span style="background-color: #ffffff; color: #000000; font-family: 'Times New Roman',Times,serif; text-decoration: none; vertical-align: baseline;">Greaves, M.; Xia, T. X., University of Bath, England; Turta, A. T.; Ayasse, C., Petroleum Recovery Institute: Canada, 2000 SPE/DOE Improved Oil Recovery Symposium, Tulsa, Oklahoma, 3–5 April 2000; [Online] http://www.onepetro.org.ezproxy.lib.ucalgary.ca/mslib/app/pdfpurchase.do?itemChronicleId=090147628008958b&itemSocietyCode=SPE (accessed Oct 4, 2011).
 * <span style="background-color: #ffffff; color: #000000; font-family: Arial; font-size: 14.66px; text-decoration: none; vertical-align: baseline;">References: **

[<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">2] Archon Technologies Ltd. Technology & Process. The Benefits of THAI. <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">http://www.archontechnologies.ca/technology-process/thai/the-benefits-of-thai (Accessed November 11, 2011).

<span style="background-color: #ffffff; color: #000000; font-family: Arial; text-decoration: none; vertical-align: baseline;">[3] <span style="font-family: 'Times New Roman',Times,serif;">Greaves, M.; Xia, T. X. Upgrading of Athabasca Tar Sand Using Toe to Heel Air Injection. Society of Petroleum Engineers. 2000, pp1-38.