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New ISC Processes


THAI Process

Novel Process: Toe To Heel Air Injection (THAI) brochure

Combines ISC process with horizontal wells in a Short Distance Oil Displacement (SDOD) process. Therefore, similar to Steam Assisted Gravity Drainage (SAGD) process, THAI is an SDOD process.

Short history:  THAI was discovered in 1992 via a cooperation by Prof. Malcolm Greaves of University of Bath, UK and Dr. Alex Turta, formerly of the Petroleum Recovery Institute (PRI); later on PRI was incorporated in Alberta Research Council / Alberta Innovates-Technology Futures, Alberta, Canada
USA patent: 5,626, 191/May 6, 1997; expired in 2015
Canadian patent 2,176, 639/August 2, 2000; expired in May 2016  

As seen in the bird's-eye view (picture 1 and picture 2), specific to the process is the location of the vertical injector in the proximity of the toe of the horizontal producer. As seen in the section view (picture 3), the ISC front is upright, leaning forward and propagates from the toe to the heel of horizontal producer. Upgrading of the oil occurs because the oil displaced by the in-situ combustion front is flowing through a relatively high temperature region called Mobile Oil Zone (MOZ).
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Toe-To-Heel Air Injection: Simplest Well Configuration, Staggered or Direct Line Drive Schematic of Toe-to-Heel Air Injection
Picture 1. Schematic of Toe-To-Heel Air Injection in a Direct Line Drive Configuration. Bird’s Eye View. Picture 2. Schematic of Toe-to-Heel Air Injection in a Staggered Line Drive Configuration. Bird’s Eye View.

An important feature of the process is its self-healing feature as far as the complete oxygen consumption is concerned. This is related to the existence of a local blockage (coke-plug) at the intersection of the ISC front with the horizontal section of the horizontal producer.  This local intensive coking of the borehole of horizontal producer (inside and around it), occurs on a limited distance; it moves along with the ISC front (picture 4). This feature was confirmed in the laboratory, by three organizations, independently. However, the existence of the coke-plug is not a condition “sine qua non” for the process, as the gravity segregation (gravity over-ridding of the ISC front) also plays an important role as a self-healing feature.  The effect of this local blockage on the advancement of the ISC front, close to the horizontal well and laterally, away from it, needs more investigations.

Related information from the attempts to apply the steamflooding in a toe-to-heel (TTH) configuration tends to confirm that although both direct line drive and staggered line drive gave good results in the laboratory 3-D THAI tests, in the field, the application in a staggered line drive is strongly recommended; this is related to its  considerably better chances for a better areal sweep efficiency (otherwise expressed, for a better lateral development of the ISC front). This seems to be even more important in case of TTH application of ISC as compared to TTH application of steamflooding.  THAI application in a staggered line drive will requires more preparatory work for the generation of an appropriate initial hot communication tightly correlated with ignition operations in order to create an initial large burning area; that preparatory work is a crucial condition for success. 

 

The Self-healing Feature for Thermal Front Advancement The Self-healing Feature for Thermal Front Advancement
Picture 3. Schematic of Toe-to-Heel Air Injection.

Picture 4. The Self-healing Feature for Thermal Front Advancement.

MOZ = Mobile oil zone

Oil is heated and mobile inside the MOZ, flowing down in the borehole of horizontal well (HW); some oil flows through the hot zone (thermal upgrading). MOZ itself moves along the HW towards the heel.

 

The THAI process is the first EOR process in which a consistent upgrading of  the oil (by 4-7 API degrees in the laboratory tests) is obtained. 
So far, more than 100, 3-D model laboratory tests have been conducted at University of Bath, UK. Also, numerical simulations were conducted by at least seven different organizations/companies.  

THAI Field testing:

1) WhiteSands Pilot, Conklin, Alberta, Canada
Athabasca, oil sands region
Three patterns, all of them in direct line drive (DLD) configuration; 5 years of testing (2006-2011)
Easy initiation and sustaining of the process; no oxygen breakthrough occurred. Easy to resume after a very long air injection interruption.
There has been in situ upgrading of the produced oil (approx. 4 API degrees). Also, hydrogen production was recorded.
Some operational problems:

  • Sand influx
  • Some oil lifting problems
  • Horizontal producers re-drilled

Note: Oil rate lower than in SAGD

Based on this pilot a commercial operation (May River Project) was planned. Later on, it was cancelled.

2) Kerrobert Pilot and Semi-Commercial Project, Saskatchewan, Canada
Conventional heavy oil (oil viscosity - 33,000cp); reservoir underlain by bottom water with thickness of oil layer approximately equal to the thickness of the bottom water zone.
The pilot: Two pairs (modules) using the direct line drive (DLD) configuration; 3.5 years of testing (2009-2012) with good results; no premature oxygen breakthrough and oil production up to 22 m3/day/well (average 10 m3/day/well).

Semi-commercial project consisted in the extension to 12 pairs (24 wells). It started at the end of 2011, beginning of 2012; as of January 2018 it is ongoing. It also uses the direct line drive (DLD) configuration; the performance is slightly lower than that of the pilot. After 8 years of THAI operation, in principle, the mechanisms of THAI application in the presence of bottom water (of this kind) have been deciphered and the knowledge necessary for the optimization of the process in similar situations has been obtained.

The presence of the bottom water precluded the increase of the air injection rate towards the projected values (this way the oil production remained at a corresponding lower level). There has been substantial day-by-day upgrading of the produced oil (3-4 API degrees) and hydrogen production.

3) THAI Pilots outside Canada
There are 4 more THAI pilots, with 2 in China and 2 in India.  In China the pilot Shuguang has been completed, while the Fengcheng Pilot in Xinjiang Province is under way, and this is the only pilot for which there are some data in the public domain. The THAI pilot (one pattern-pilot) in India has been taking place on the Balol heavy oil reservoir since December 2016;  given the results of the first THAI pattern, during 2017 the piloting in Balol was extended to three more patterns. At the end of 2017 a second THAI pilot on the second heavy oil reservoir (Lanwa reservoir) was initiated. At this time the results are confidential.

THE 4 CRITICAL CONDITIONS FOR SUCCESSFUL APPLICATION OF THAI (or a kind of generalized process similar to THAI):
1. Existence of a high permeability pathway at the bottom of the layer (horizontal well,  horizontal-disk fracture, extremely thin bottom water layer, etc).

2. Successful anchoring of the ISC front at the extremity of the high permeability pathway at the bottom of the layer (or toe of horizontal producer).

3. Existence of a hot region of high fluid mobility behind the displacement front and a relatively low temperature region of low fluid mobility ahead of displacement front (along or parallel to the high permeability pathway).

4. Controlled gas over-ride involving the tilting forward of the ISC front (with or without a ‘self-healing’ feature“ associated with a coke local blockage during progression of the displacement front along the high permeability pathway).

 

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CAPRI Process

An enhanced upgrading can be obtained by applying the catalytic version of THAI, named CAPRI.

In CAPRI, the horizontal section of the THAI horizontal producer is surrounded by a catalyst-activated gravel packing (picture 5). Therefore, CAPRI is a THAI-add-on process.

All the phenomena (thermal, hydrodynamic, etc) are the same for THAI and CAPRI; the only difference is the second upgrading occurring when oil is flowing into the bottom-hole of the horizontal producer.  In laboratory testing, the process was able to achieve an upgrading of up to 14 API degrees.
 
Compared to THAI, CAPRI is much less investigated and developed.  In addition, there are many challenges in the simulation of the process; at this time it is practically impossible to reflect the upgrading process in its entirety.

Short history: CAPRI was discovered in 2002 by Dr. Conrad Ayasse and Dr. Alex Turta, formerly of the Petroleum Recovery Institute (PRI), with PRI later incorporated in Alberta Innovates-Technology Futures, Calgary, Canada.  Prof. Malcolm Greaves of University of Bath, UK is also a co-author of this novel process.

  • USA patent: 6,412,557/July 2, 2002                      
  • Canadian patent  2,176,639/July 8, 2003  

Current status:  So far, CAPRI process has seen just a very limited testing in the field; it has not been extensively piloted.

Catalytic THAI – CAPRI Process

Picture 5. Catalytic THAI – CAPRI Process.

 

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COSH/COGD Process

COSH Combustion Override Split-Production Horizontal Well) is intended for application in reservoirs containing oil with some mobility at reservoir condition. COGD (combustion overhead gravity drainage) is a version of COSH intended for the application in oil sands. In addition to COSH it specifies the means for obtaining the initial communication between injectors and producers, therefore is intended for higher viscosity oil reservoirs, even without mobility at reservoir conditions.  

Both processes combine the ISC with horizontal wells in a short distance oil displacement (SDOD) process for most of the their project life. As seen in the general schematics (picture 6) and crossection views (picture 7), there are several vertical injectors located immediately above the horizontal producer, which is located at the bottom of the thick oil layer.  Laterally, there are some vent wells for gas production, mainly.

Short history:  COSH was proposed in 1994 by Ken Kinsman, Edmund Lau and Bill Good of AOSTRA, Alberta, Canada
Canadian patent 2096034;  see Journ of Can Petr. Techn, March 1994  

The most important feature of both processes is the existence of vent wells; their role is to produce most of the combustion gases.  My comments on these processes:

  • The control of several ISC fronts intercepting the same horizontal producer well is extremely difficult
  • Requires special gas collection wells (more expensive)

Current status:  COSH and COGD processes have not been field tested.

Schematic of COSH process Schematic COSH Process Diagram

Picture 6. Schematic of COSH process (After Kisman and Lau,1994).

 

Picture 7. Schematic COSH Process Diagram.

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Top-Down ISC Process

The process was directly inspired from the peripheral (top-down), line drive commercial ISC exploitation at Suplacu de Barcau.

To some extent, the process is similar to COSH process. However, unlike COSH, the process does not have any vent wells (picture 8); the process is not completely defined yet.

There are two versions of top-down ISC: one is intended for application when there is some mobility of oil, and the second one is intended for application in oil sands; second one assumes the existence of a man-made initial communication.  The first one was studied in more detail by simulation, while the second one was investigated in the laboratory. 

Short history: The process was proposed in 1993 by David Redford of AOSTRA and later on investigated by Roy Coates and John Ivory of Alberta Research Council (ARC); ARC later became Alberta Innovates - Technology Futures (AITF).

Current status:  the process has not been field tested.

Conceptual application of a TD-ISC process

Picture 8. Conceptual Application of a TD-ISC Process (late phase of the process).

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