Tracer Injection

Purpose

Tracers can be used to track the leading edge of the water front in order to identify breakthrough in other wells. Tracer programs can also indicate residual oil saturation. Sampling is carried out at a regularly defined interval until (and after) it is identified at a production well. Produced water injection operations are not affected by tracer injection and monitoring, with the exception of extra time required for testing the produced water.

Benefits

Reservoir tracers are substances added to the injection fluid (normally water) and collected by sampling at production wells (single well tracer tests can also be carried out). Inferences on the fluid path may be obtained by analyzing the tracer output. Directional flow trends, flow barriers and communication between reservoirs are examples of relevant qualitative information, which may be extracted from well-to-well tracer tests. Quantitative information, such as sweep efficiency, may be estimated by matching tracer well data against a mathematical prediction.

Tracers can be used for:

• Characterization of reservoir continuity. You can infer continuity by monitoring different tracers produced into different wells. Alternatively, if you do not produce tracers or if recovery of a specific tracer is delayed, you can draw conclusions about the effectiveness of barriers.
• Characterization of reservoir transmissibility. Transmissibility can be estimated from tracer transit time.
• Identification of reservoir-scale fracturing, faulting and other directional features. For example, directional reservoir features cause preferential short transit times, and may lead to high concentrations of recovered tracer.
• Identification of areally widespread gas caps or more limited gas saturated intervals. For example, water can move preferentially through gas-saturated zones and may delineate a thin zone at the bottom of gas zones.
• Preferred injection paths. With tagged water, there is often a rapid, sharp, intense tracer pulse. For gas tracers, tracers injected at different times may be sensed at a producer at the same time, indicating an accumulation of gas in the injector-producer pathway.

Modeling

Well-to-well tracer technology applied during water/gas injection programs provides information on the flood pattern in the reservoir. This information reduces many uncertainties about the flow paths, reservoir continuity and directional features in the reservoir. In order to improve identification and determination of the scale and location of these heterogeneities, it is essential to be able to simulate the flow of tracers inside the reservoir and match the outcome with measured tracer data. Tracer flow between an injector-producer pair gives definitive information about the section of the reservoir between these wells. Single well tracer testing can also be modeled to infer oil saturation.

Take a step back. You know that there is continuity when injected tracer is observed at a producer. History matching can quantify the transmissibility. It has, for example, been successfully used to represent WAG injection on Snorre (Central Fault Block). Tracers were injected in three wells. The tracers (in water) used were HTO (tritiated water), S¹⁴CN (14C labeled thiocyanide), SCN (thiocyanide) and 4-FBA (4-fluoro benzoic acid). Tracer production was analyzed in the producing well water cut. Analysis of the Snorre data considered:

• Breakthrough time of each tracer in each producer where it appeared, giving the water velocity at the time that the tracing was moving in the reservoir.
• The general shape of the tracer profile (peaks etc) provided information on the flow paths connecting wells.
• The tracer concentration indicated the amount of water flowing.

In certain cases, inability to match measured behavior suggested different in-reservoir features than had been previously inferred.

Tracers

The choice of a tracer requires:

• The selected tracer needs to be nonexistent in the reservoir, or present in very low concentrations,
• Stable and non-reactive with target formations at reservoir conditions,
• Amenable to quantitative analysis at very low concentrations,
• Have good solubility in the aqueous phase,
• Be safe and easy to use, and,
• Have a low cost

Tracers used in the petroleum production industry may be classified into three main groups; radioactive, fluorescent and chemical. Radioactive tracers are frequently used (their detection level is low, injected quantities are consequently small). Chemical tracers (particularly halogens) are effective (stable) but have a relatively high detection level. Fluorescent tracers are inexpensive and safe. They can be detected without laboratory evaluation but are they are known to adsorb on formation material. These latter tracers are consequently used only when the residence time is adequately short (e.g., flow along a fault).

A suite of different tracers has been used in the Carmopolis field in the Segipe/Alagoas Basin (onshore, oil accumulation in Brazil). Waterflooding is ongoing and final recovery is estimated at 24% OOIP. There is a large mobility ratio and there is a significant variation in the vertical permeability, leading to a nonuniform vertical distribution of the injected water. Polymer injection has been considered because of the large mobility ratio and interwell tracer testing was implemented to optimize this.

• Tritium was injected first, followed by a small polymer slug. Tritiated water (³H) has an extremely low detection level, has a half-life of 12.26 years and is low cost. It was analyzed with a liquid scintillation counter (for emitters).
• Fluoroscein was then injected to sense any change in sweep efficiency. Fluoroscein sodium (Ca₂₀H₁₀Na₂O₅) is an organic pigment and was detected with a spectrophotometer.
• Iodide was then injected with polymer (continuously). Anionic ions are generally most suitable because they can be less adsorption-prone. Possibilities include chloride, bromide, and iodide. Nitrogen compounds (thiocyanate and nitrate) are also options. Chloride and bromide ions are common in petroleum reservoirs and the nitrogen compounds biologically degrade. Petrobras selected iodide as the best option and detected it with ionic chromatography.

Radioactive tracer was handled by a government agency since Petrobras is not authorized to handle radioactive material.

Petrobras observed that pulse techniques (an extremely short slug) were more favorable than slug injection because the analysis is less dependent on unknown dispersivity values. Tracer testing was used in conjunction with available interference data.

At the request of the Sponsors, description of tracer technologies was provided by Synetix (e-mail to John Shaw from Raymond Lovie, July 2001). This document is included largely as received. Some commercial content has been removed.

Single Well Chemical Tracer Test (SWCT)

The Single Well Chemical Tracer (SWCT) test is a method for measuring residual oil saturation (S_or). An SWCT test is carried out by injecting, and then producing back into the same well, a volume of reservoir brine labeled with appropriate chemical tracers. A volume of brine containing about 1% by volume of a partitioning ester is injected into the target zone of the test well. The ester-containing brine is then displaced by a larger volume of brine without ester, until the ester bank reaches ten to fifteen feet into the reservoir. The oil-water partitioning coefficient of the ester is measured in the laboratory at reservoir conditions. The total volume injected is typically labeled with a suitable alcohol, the non-partitioning (material balance) tracer.

During a shut-in period of one to ten days, a portion of the ester reacts with the reservoir water and forms the secondary tracer. This secondary tracer is an alcohol that is soluble only in water.

After the shut in period, the well is produced. The produced fluid is periodically sampled and analyzed for content of the unreacted ester, the secondary alcohol tracer, and the material balance tracer. The partitioning of the unreacted ester between the immobile residual oil phase and mobile brine delays production of the ester by an increment of volume directly related to the residual oil saturation. The secondary tracer flows back to the well at the same speed as the brine. Since the ester spends part of its time in the oil phase, it is produced later than the secondary tracer. This chromatographic separation of the ester and the secondary tracer is observed in profiles of tracer concentrations vs. produced volume.

The amount of separation between these two tracers is used to calculate residual oil saturation. In ideal cases, the S_or results can be calculated directly from field-measured concentration versus produced volume profiles. In more typical cases, the profiles must be mathematically modeled and simulated to obtain best-fit results for S_or.

Various references on Single Well Chemical Tracer Technology are available.

Pre-Placement of Tracers in Production Wells

A patented tracer application has been developed by ICI TRACERCO (http://www.synetix.com/services/tracercoservices-main.htm) and Norsk Hydro a.s.a., for flow verification during cleanup and initial production. The principle of the technology involves the positioning of a number of different tracer materials, each at specific locations along the tubulars before running into the hole. The tracers are selected to be soluble only in crude oil. On well startup, oil samples are taken at the surface over a short period of time. The samples are analyzed for tracer. The presence of one or a combination of unique tracers within the oil and the known location of each tracer downhole allows qualitative information to be generated.

Tracer Attachment

Immediately before running perforation guns or screens, a suitable tracer is irreversibly attached to the outside of a number of individual shaped charges or the inside wall of a pup joint. The tracer selected has a lifetime of approximately one year so that it can be readily detected in production fluids following lengthy downhole operations. It is soluble in crude oil and insoluble in water. Each of several different tracers may be attached to specific perforation guns or pup joints to be used at the production intervals of most interest to the operator. The specific tracers used can be easily differentiated from one another due to their unique energy spectra. In the case of perforated liner completion arrangements, when the perforating guns are fired, the tracer is carried with the explosive pressure wave into the formation. The tracer, due to its insolubility in water, will remain in the formation until first oil production. For pre-packed screen completions, the tracer is added to an oil soluble wax and irreversibly attached to the inside of a number of completion joints.

Flow Verification

On clean-up and first oil flow, tracer is carried to the surface from the perforations containing tracer or from wax. Samples of oil are taken and analyzed for the presence of all the tracers that have been used. The presence of specific tracer types enables determination of whether all tagged positions within the wellbore are contributing to overall oil production.

Interwell Waterflood and Injection Gas Tracers

The application of tracers in waterflooding, water injection and injection gas operations allows (http://www.synetix.com/services/tracercoservices-processdiagnostics-waterflood.htm):

• Determination of injection water or gas communication pathways to a number of producing wells.
• Determination of injection water or gas flow rate through a reservoir.
• Determination of volumetric sweep efficiency..
• Assessment of vertical sweep..
• Determination of the presence of high permeability channels.
• Determination of the presence of communication across fault blocks and between formation zones.
• Determination of the preferred directional communication trends.
• Determination of the interwell residual oil saturation.
• Assessment of the effectiveness of formation chemical or biological blocking operations.
• For injection gas operations, determination of whether the flood is first contact miscible or two phase flow.

Waterflood Tracer Technology

• Chemical and low energy radioisotopes can be used to eliminate external radiation considerations both during injection and sampling operations.
• A number of unique tracer types can be used to establish injector to producer relationships throughout a field.
• The technique may be combined with downhole logging or sampling to allow vertical as well as horizontal mapping of the field.
• Ability to measure extended breakthrough times up to ten years and beyond.
• Chemical and radioactive species that can be used are stable under reservoir conditions of temperature, pressure, resist biodegradation and are passive to formation and fluids within the reservoir.
• Analytical techniques capable of resolving multi-tracer breakthrough into one production well with sensitivities capable of detecting high tracer dilutions.
• Safe and on-line injection procedures avoid interruption of normal injection operations.

Gas Tracer Technology

Injection gas monitoring involves introduction of one or more compatible species into injection gas at the wellhead or downhole at the zone of interest. These tracers are unique to the reservoir system, and are monitored at potential target producing wells throughout the field. Analysis of the resulting tracer concentration versus time curves from individual producing wells enables determination of interwell flow in order to increase injection gas sweep efficiency.

The tracers used need to be passive within the reservoir, thermally stable at reservoir temperatures, stable to bacterial activity downhole, chemically unreactive with other species present, unique to the system and must be easily detectable in order that practical quantities need only be used. In order to gain useful information regarding interwell flow they must also have similar properties to injection gas at conditions within the system under investigation. There are a limited number of proven tracers that fulfill these criteria, including radioisotopically tagged gases – tritium as methane, ethane or propane and perfluorinated sulphur and hydrocarbon compounds.

In the majority of injection gas operations, the produced natural hydrocarbon gas is re-injected and consists of a mixture of gas components with different partitioning and diffusion properties. It therefore follows that no tracer is ideal for this mixture. However, tritium as methane has more or less the same chemical and physical properties as methane and as such may be considered as an ideal tracer. Under reservoir conditions of temperature and pressure, it has been demonstrated that sulphur hexafluoride and PFC compounds have similar physical properties to methane and ethane.

Chemical Treatment

“A variety of [specialty] chemicals such as corrosion and scale inhibitors are added to wells either by continuous or batch injection methods. TRACERCO have developed and field-tested a method that allows the chemical position to be monitored in order to achieve the most effective treatment conditions. The tracer is manufactured by the attachment of a gamma-emitting isotope in the TRACERCO laboratories to the unsaturated hydrocarbon tail of the molecule. This allows the material to be traced whilst maintaining its chemical properties. Following the addition of the tagged material to a batch of chemical, a downhole logging tool or surface sampling of production fluids can be used to determine parameters such as chemical drop time in batch treatments, chemical erosion rates from production tubing, position and distribution of chemical within production tubing and mass balance of chemical following squeeze operations.”

Other Vendors:

Some of ICI (Synetex)’s tracer products were described above. There are certainly other vendors. For example, FLUTEC^TM TG-TRACERS (http://www.fluoros.co.uk/flutec/tracer/index.htm) can be used in the monitoring and development of fields undergoing gas injection.

FLUTEC^TM TG-TRACERS are injected with the injection gas and will trace the path of the injection-gas to a production well in the subsurface environment. This means that definitive information can be obtained regarding injector/producer communication, partitioning characteristics and cycle times.

“Traditional gas tracer techniques have involved the use of various combustible radionuclides injected at high pressure into injection wells. Although valuable information has been collated there are obvious safety and environmental issues with the continued use of these tracers. FLUTECTM TG-TRACERS have excellent toxicological profiles and are not ozone depleters. They also offer similar detection limits to radioisotope tracers, have transport characteristics comparable to methane and ethane at reservoir conditions and exhibit excellent chemical and thermal stability within the reservoir.”

“Unlike radiotracers FLUTEC^TM TG-TRACERS do not occur naturally within the reservoir, eliminating the chance of receiving spurious information by masking, and offer the advantage of a wider tracer portfolio enabling multi-well tracer operations to be performed. FLUTECTM TG-TRACERS can be simultaneously deployed, sampled and analyzed with the same instrumentation.”

Another vendor, ProTechnics, (http://www.protechnics.com/) provides SPECTRAFLOOD^TM tracers. The reported applications include:

• Identify directional heterogeneity.
• Evaluate Sweep Efficiency and EUR.
• Identify multiple porosity permeability systems and their respective fractional volumes.
• Gather design parameters during a pilot flood.
• Evaluate the need for and design parameter for conformance control.
• Evaluate early water breakthrough Improve design for anticipated tertiary recover projects.

ProTechnics provided a case study:

“This field example illustrates the information that can be obtained from an interwell tracer test. The unit concerned had shown poor response to water injection with little oil response and high water cut. Some of the high water cut wells were distant from injection wells. Tracers were thiocyanate ion, radioactive cobalt, and tritiated water. Breakthrough time was as short as 4 days and produced tracer concentrations were high. While tritiated water injected at well 11 showed at well 9 in 4 days, wells 8 and 12 did not show tracer even as long as 18 months after tracer injection. Tracer appears in wells that are closely aligned in an ENE direction to the original tracer injection points. The rapid breakthrough, high produced concentration, and rapid decline in tracer level point to closely aligned fractures as the most probable explanation for the tracer behavior. Tracer appeared quickly to the east of tracer injection wells but only very slowly to the west. Aligned fractures are not expected to terminate at the injection well. The strong eastward flow then suggests a pressure gradient across the reservoir with continuing loss of injecting fluid in an easterly direction. Changes in the injection pattern plus control of water loss to the east are suggested as

There are various other geographically local vendors and service organizations. For example, you might refer to the Cardinal Surveys website (http://www.cardinalsurveys.com/default.asp). There is information on operational issues, and safety/regulatory considerations for radioactive service.

Single Well Chemical Tracer Test References

1. http://www.chemtracers.com/single.htm
2. Tomich, J.F., Dalton, R.L., Deans, H.A., and Shallenberger, L. K.: "Single-Well Tracer Method to Measure Residual Oil Saturation," JPT (February 1973) 211-218.
3. Deans, H. A.: "Method of determining Fluid Saturations in Reservoirs," U.S. Patent #3,623,842 (Nov. 1971).
4. Deans, H. A. and Majoros, S., "The Single-Well Chemical Tracer Method for Measuring Residual Oil Saturation," Final Report, DOE/BC20006-18, (October 1980).
5. O'Brien, L. J., Cooke, R. S., Willis, H. R., "Oil Saturation Measurement at Brown and East Voss Tannehill Fields," JPT (January 1978) 17-24.
6. Sheely, C. Q., "Description of Field Test to Determine Residual Oil Saturation by Single-Well Tracer Method," JPT (Feb. 1978) 194-202.
7. Thomas, E. C. and Ausburn, B. E.: "Determining Swept-Zone Residual Oil Saturation in a Slightly Consolidated Gulf Coast Sandstone Reservoir," JPT (April 1979) 513-24.
8. Nute, A. J.: ""Design and Evaluation of a Gravity-Stable, Miscible CO2-Solvent Flood, Bay St. Elaine Field," paper SPE 11506 presented at the 1983 Middle East Oil Tech. Conf. of SPE, Manama, Bahrain, March 14-17.
9. Chang, M.M., et al.: "Evaluation and Comparison of Residual Oil Saturation Determination Techniques," SPE Formation Evaluation (March 1988) 251-262.
10. Donaldson, E.C.: "Comparison of Methods for Measurement of Oil Saturation," paper SPE 10298 presented at the 1981 SPE Annual Technical Conference and Exhibition, San Antonio, TX October 5-7.
11. Energy Information Administration, Annual Report, 1980,p.16; 1981, p.22; 1982, p.3 -3.
12. Salathiel, R.A.: "Oil Recovery by Surface Film Drainage in Mixed-Wettability Rocks," JPT (October 1973) 1216-24; Trans., AIME, 255.
13. Deans, H.A., Shallenberger, L.K.: "Single -Well Chemical Tracer Method to Measure Connate Water Saturation," paper SPE 4755 presented at the 1974 SPE Improved Oil Recovery Symposium, Tulsa, April 1974.
14. Cooke, C. E. Jr.: "Method of Determining Residual Oil Saturation in Reservoirs," U.S. Patent No. 3,590,923, July 6, 1971.
15. Deans, H.A., Carlisle, C.T.: "Single-Well Tracer Tests in Complex Pore Systems," paper SPE/DOE 14886 presented at the Fifth Symposium on EOR Tulsa, April 20-23, 1986.
16. Carlisle, C.T. et al.: " Development of a Rapid and Accurate Method for Determining Partition Coefficients of Chemical Tracers Between Oils and Brines (for Single-Well Tracer Tests)," Contract No. DOE/BC/10100 -4 U.S. DOE (Dec. 1982).
17. Sheely, C.Q. and Baldwin, D.E.: "Single -Well Tracer Test for Evaluating Chemical Enhanced Oil Recovery Processes," JPT (Aug. 1982) 1887-96.
18. Holland, K.M., and Porter, L.T.: "Single -Well Evaluation Program for Micellar/Polymer Recovery, Main and 99 West Pools, West Coyote Field, California," paper SPE 11990 presented at the 1983 SPE 58th Tech. Conference and Ex. San Francisco, CA. October 5-8.
19. Edinga, K.J., McCaffery, F.G., Wytrychowski, I.M.: "Cessford Basil Colorado A Reservoir-Caustic Flood Evaluation", JPT (Dec. 19880) 203-2110.
20. Bragg, J.R., H.A. Deans, and Shallenberger L.K.: "In-Situ Determination of Residual Gas Saturation by Injection and Production of Brine," paper SPE 6047 presented at the 1976 SPE 51st Tech. Conference and Ex. New Orleans, LA. October. 3-6.
21. Deans, H.A., Mut, A. D., "Chemical Tracer Studies to Determine Water Saturation at Prudhoe Bay"; SPE Reservoir Engineering, Feb. 1997, page 52-57.

Other References/Abstracts

SPE 69474 – Petrobras Tested Radioactive, Chemical and Fluorescent Tracers

de Melo, M.A., de Holleben, C.R., and Almeida, A.R.: “Using Tracers to Characterize Petroleum Reservoirs: Application to Carmópolis Field, Brazil,” SPE 69474, SPE Latin American and Caribbean Petroleum Engineering Conference, Buenos Aires, Argentina, (25-28 March 2001).

Abstract

A specific area under water injection in the Carmópolis field, Brazil, is being considered a candidate area for a polymer pilot project for mobility control. A reservoir characterization and an evaluation of the polymer performance in this highly heterogeneous reservoir were required. For this purpose, radioactive, fluorescent and chemical tracers were applied associated with polymer in a reduced area.

The tracer technology has an enormous potential use in Petrobras scenario and this Carmópolis field application was an opportunity to obtain know-how. This paper describes the basic steps from the laboratory tests to the final application including design and programming of field operation. The interpretation of the results using a new approach is also addressed.

SPE 68051 – SWCT and Miscible Gas Flood at Prudhoe Bay

Cockin, A.P., Malcolm, L.T., McGuire, P.L., Giordano, R.M., and Sitz, C.D.: “Analysis of a Single-Well Chemical Tracer Test To Measure the Residual Oil Saturation to a Hydrocarbon Miscible Gas Flood at Prudhoe Bay,” SPE 68051.

Summary

"In 1990, a single-well chemical tracer (SWCT) test was performed in Prudhoe Bay to measure the effective waterflood and miscible gas flood residuals over a 12 ft reservoir interval. This is believed to be the first such use of this technology for a hydrocarbon miscible gas. This paper describes how the usual SWCT design was modified to accommodate the miscible gas, the results of the SWCT, which indicate significantly higher residual oil saturation for miscible gas flood than expected from coreflood experiments, and the subsequent simulation of the test, which has provided good agreement with the observed results. The paper shows, with compositional simulation support, that the high apparent residual oil saturation was a consequence of incomplete volumetric sweep by the miscible gas and draws on the experiences of this test to make recommendations for the design of future SWCT tests measuring residuals to gasflooding.”

Synopsis

“In 1990, a single-well chemical tracer (SWCT) test was carried out on a producing well which first measured the effective residual to waterflood and then to miscible gasflood. The attraction of the SWCT was that it investigated a much larger volume of rock than a coreflood and native wettability, away from the wellbore, should be assured. However, it should be recognized that this still only represents a small sample, which may not represent the average performance on a broader scale.”

SWCT

Reservoir brine, with approximately 1% by volume of a partitioning chemical (soluble in oil and water) is injected. After “adequate” radial penetration the well is shut-in to allow reaction of the partitioning chemical with the brine and formation of a new nonpartitioning chemical that is almost entirely water-soluble. On backflow, the nonpartitioning tracer, flowing with the water, arrives early while the partitioning tracer is delayed by the presence of immobile oil. The delay is proportional to the oil saturation. An ideal test assumes radial flow and a stationary front on shut-in. Some of the specifics of this technology are:

• Ethyl acetate is an ester. It can be used as a partitioning tracer. It will react with water to form ethanol and an acetate anion.
• Ethanol has very low solubility in oil. It is the nonpartitioning tracer.
• Shut-in time depends on reservoir temperature. Premature backflowing will produce little ethanol. If you wait too long to backflow, little ester will be left.
• What happens as the ester is injected? It will partition into any oil that it encounters. If the oil saturation is low, the ester will penetrate more. The ester front governs where alcohol is formed.
• A cover tracer is usually injected with the partitioning tracer. This marks the water that contained the ester in the first place.
• A material balance tracer is also used. This is commonly another alcohol. One is added only to the water with the partitioning tracer. Another is added to that water and the push water. These tracers can indicate the influence of offset wells.
• You backflow until the material balance tracer is recovered and establish whether or not the process is reversible and to ensure recovery.
• It is better to test thin intervals (interpretation is easier).
• Quantitative conclusions require some degree of laboratory calibration.

SPE 65135 – (describes using tracers in the Sleipner East Field)

Helga Hansen, H. and Westvik, K.: “Successful multidisciplinary teamwork increases income. Case study: The Sleipner East Ty Field, South Viking Graben, North Sea,” SPE 65135, 2000 SPE European Petroleum Conference held in Paris, France, 24-25 October 2000.

Abstract

Seismic and well data, such as cores, logs and production tests are the vital input data used to build geological models for exploration and development of hydrocarbon fields. However, once a field is put on stream, production data itself gives valuable and important additional knowledge that improves geological insight and understanding. In particular, pressure observations, tracer data, together with production logs provide essential information about recoverable hydrocarbon volumes, communication routes, flow barriers, and drainage pattern within the reservoir.

A multidisciplinary team consisting of geophysicists, geologists, petrophysicists, reservoir and production engineers, together with drilling and completion engineers, cooperated for the last three years evaluating the Sleipner East Ty Field, which is a gas-condensate reservoir situated in the South Viking Graben, North Sea. During the work process, there has been a continuous feedback loop from the production data to the geological model. Changes of the geological model were carried out in order to match the dynamic reservoir model with actual production data. The resulting new models have been the basis for accelerated gas sales commitments and for increased condensate production from the reservoir. The integration of production and well engineers in the reservoir modeling team has lead to valuable focus on alternative drainage strategies, including drilling of new, challenging wells and more economically viable well interventions.

Synopsis:

The Sleipner East Ty Field is a gas condensate reservoir in the South Viking Graben.There has been dry gas injection since 1994 (one year after the start of production). Lighter hydrocarbon components have been accumulating in the uppermost reservoir zones and reservoir evaluations have been undertaken to plan intervention and new access. Chemical gas tracers were injected and monitored at producers.

SPE 64796 – Describes Using Tracers on Snorre

Ali, E., Chatzichristos, C., Aurdal, T., and Muller, J.: “Tracer Simulation to Improve the Reservoir Model in the Snorre Field,” SPE 64796, SPE International Oil and Gas Conference and Exhibition, Beijing, China (7-10 November 2000).

Abstract:

This paper presents the application of water tracer flow simulations as a means for better characterization of the Central Fault Block (CFB) reservoir in the Snorre field in North Sea. The simulations of the tracer flow were carried out using a numerical model, developed by the Institute for Energy Technology for modeling of tracer flow in porous media, coupled to CMG-STARS chemical/thermal simulator. The tracer data were first analyzed to establish reservoir continuity between three injectors and six producers in the fault block. Then, tracer flow simulation results were matched with measured tracer field data in order to improve the history match of the water cut in the reservoir model.

History matching of tracer production profiles is presented together with history matching of water cut before and after the consideration of tracers to highlight the improvement of the reservoir model.

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