Taribani Field Unit
The Taribani Field, situated within the Taribani Field Unit Complex alongside the Kila Kupra, Iori and Baida fields (click here to learn more about these fields), is a large over-pressured oil field covering an area of approximately 80 km2 with productive horizons situated in Miocene and Pliocene age reservoirs that have been deposited in fluvio-deltaic to nearshore marine environments. Reservoir and regional mapping, along with extensive surface geological work undertaken by the Company indicate that the reservoir facies are well developed and, in some cases, their permeability is enhanced by fracture systems associated with regional strike-slip faulting that is found throughout the Upper Kura Basin. These reservoirs are situated at depths of between 2,200 m and 3,500 m.
The Taribani Field was penetrated by forty-one wells during the Soviet era, drilled between 1962 and 1981 and all clustered in the down-dip portion of the field. The Taribani Field has to date produced a total of approximately 550,000 barrels of oil from eight of the forty-one wells. Oil taken by Frontera from the Taribani Field has been tested and found to be 36 degree API with a low sulphur content (0.23 per cent). Frontera believes that the limited production was due to poor historic drilling and completion practices, and a policy decision taken by the government authorities in the 1970s to focus on the development of the Samgori Field, located close to Block 12. Frontera believes that significant reserves from the Taribani Field are commercially recoverable by utilising conventional technologies, and drilling and completion methods.
Since acquiring its interest in Block 12 in 1997, Frontera has undertaken detailed field and operational studies at the Taribani Field in order to determine how to bring the field into commercial production. Druing this time, Frontera has specifically:
- completed the acquisition, processing and interpretation of a new 3D seismic survey covering 150 km2;
- digitized and integrated all historical well logs from the Taribani Field;
- created new time and depth structure maps, as well as new associated sand isopach maps, for twelve productive reservoirs;
- conducted static and dynamic reservoir engineering studies;
- conducted fracture and well-bore-hole stability analysis;
- performed new geologic field work that has enabled the integration of surface observations into the subsurface areas of the Taribani Field
- completed new reservoir engineering studies; and
- acquired 60 km of new 2D seismic to compliment the 3D survey and validate the southwestern portion of the Taribani Field structure.
In addition to the geological, geophysical and reservoir engineering studies, many of the existing wells were re-entered and checked for casing integrity, mechanical problems and obstructions, with the intention of using them for future workover or sidetrack operations. Workovers were attempted in seven of these wells with limited success due to the previous Soviet era drilling practices that resulted in skin damage to the well-bores. Detailed core pressure analysis was conducted to prepare for future new well-bore design, mud and completion programs.
Furthermore, in 2000 Frontera drilled, tested and completed the Niko #1 well at the Taribani Field. This well was the first post-Soviet era well drilled into the field using modern drilling practices and provided results that confirmed the effectiveness of modern drilling applications. Specifically, the well provided much needed subsurface information that permitted Frontera to calibrate field-wide well logs to conventional core and the reservoirs. It gave critical understanding regarding the fluid properties from the field and established an understanding of the field’s depletion drive mechanism.
Niko #1 also provided important velocity information with which to tie the subsurface information to the 3D seismic survey. This information established that most of the structural potential of the field exists west and approximately 200 meters up-dip of the Niko #1 location. Finally, the results from the well established the deeper marine intervals (Zones 18 to 25) as being hydrocarbon bearing with the ability to flow at commercial rates. The well flowed at a peak rate of 960 bpd, producing 5,345 barrels during its forty day production test. However, production was suspended as a result of sediment flow believed to be from the open hole and from behind the casing due to a poor cement job and a failed lower packer. The Niko #1 well remains a candidate for re-entry as part of future full-field development operations.
Based on its experience with previous production operations, Frontera expected that the previously encountered issues related to the challenges of sediment flow at Niko #1 and other wells in the field could be managed and overcome. Following the completion of drilling and testing operations at the Dino #2 well in August 2006, Frontera conducted detailed analysis of the extensive coring, logging and production data obtained from the well, in order to customize new well-completion designs for future wells and prioritize plans for developing four target reservoir horizons; Zones 9, 14, 15, 19. These new engineering designs applied industry-standard solutions to the specific reservoir properties of the Taribani Field in order to overcome sediment obstruction in future wells and ensure sustainable flow from the field’s reservoirs.
Based on analysis of Zone 9 reservoir data, a new well-completion design for this horizon was engineered in order to control possible sediment flow during production operations. Analysis of data obtained during coring and logging operations of the Dino #2 well not only revealed a fractured reservoir, but also demonstrated that this reservoir’s rock properties are particularly well suited for the artificial inducement of fractures to further enhance permeability. As a result, Frontera evolved its development well design for Zone 9 from drilling short-reach horizontal wells to drilling conventional vertical wells with the addition of fracture stimulation completions. (“Frac completions” are designed to enhance well flow rates and ensure sustainability of production by creating artificial fractures in the productive zones.)
The re-completion of Dino #2, the first well in the Taribani Zone 9 development program, concluded in September 2007. In December, the T-#45 well, the second of three wells in the initial program, was drilled to a depth of approximately 2,400 meters. Zone 9 was encountered at approximately 2,300 meters and was found to be oil bearing.
In April and May 2008, frac completions were applied in Zone 9 in both the Dino #2 and T-#45 wells in order to enhance the flow-rates, eliminate sediment production and ensure the sustainability of production. Results of long term production from both wells confirmed sediment-free, sustainable production. Thus, the application of frac completions validated two important elements for Frontera’s future field development plans: 1.) The ability to eliminate sediment flow is now conclusive, and; 2.) The ability to sustainably produce long term with minimal decline has been decisively demonstrated.
Frontera placed the Dino #2 and T-#45 wells into production at initial rates of approximately 200 barrels per day and 130 barrels per day, respectively. However, rates declined to approximately 25 barrels per day from each well, but have produced sustainably with minimal decline at this level for well over one year.
Associated reservoir engineering analysis determined that while frac completions could successfully eliminate sediment flow and enhance sustainable production performance from the reservoir formations present at Taribani, it was discovered that the applied fracs were not as effective as originally planned. As a result, Frontera has redesigned future frac completions in order to optimize their performance. Frontera believes that this will result in increased sustainable production volumes from individual reservoir horizons. Analysis of results has also determined the viability of commingling horizons 9, 14 and 15 in future wells into single well completions to further enhance individual well productivity and recovery.
Based on long term production performance and the associated analysis described above, Frontera believes that the Dino #2 and T-#45 wells, as well as future wells drilled at Taribani, are capable of producing at optimized rates substantially higher than the presently observed production levels.
Frontera is currently considering options for a redesigned schedule for continued development drilling work at Taribani in order to bring the field into commercial production.
Future Work Program
Based on Frontera’s work in the Taribani Field, twelve productive horizons have been identified for potential exploitation and development. Frontera’s near term strategy is to focus on establishing commercial production from four of these twelve horizons: Zones 9, 14, 15 and 19.
Frontera believes that it can produce approximately 118 million barrels of reserves from Zones 9, 14, 15 and 19 at commercial rates. These reserves have been independently evaluated by Netherland Sewell & Associates Inc.and have been classified as possible (P3) gross (8/8ths) reserves. Netherland Sewell & Associates Inc. has indicated that, provided Frontera can demonstrate commerciality, a significant portion of the P3 reserves in the Taribani Field could be recategorized as P2 and P1 reserves.
Plans are also underway to continue the assessment of the other eight horizons in the field. Frontera believes that these other horizons will define additional significant recoverable reserves within the field. In addition, the western portion of the field is believed to contain significant potential that has yet to be exploited. No oil-water contacts have been found in the Taribani Field, which indicates that the field limits have yet to be fully determined.