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AlAbbad, Mohammed A. (Saudi Aramco) | Sanni, Modiu L. (Saudi Aramco) | Kokal, Sunil (Saudi Aramco) | Krivokapic, Alexander (Institutt for Energiteknikk) | Dye, Christian (Institutt for Energiteknikk) | Dugstad, Øyvind (Restrack) | Hartvig, Sven K. (Restrack) | Huseby, Olaf K. (Restrack)
Summary The single-well chemical-tracer test (SWCTT) is an in-situ test to measure oil saturation, and has been used extensively to assess the potential for enhanced oil recovery (EOR) or to qualify particular EOR chemicals and methods. An SWCTT requires that a primary tracer be injected and that a secondary tracer be generated from the primary tracer in situ. Typically, a few hundred liters of ester is injected as primary tracer, and the secondary tracer is formed through hydrolysis in the formations. The ester is an oil/water-partitioning tracer, whereas the in-situ-generated alcohol is a water tracer. During production, these tracers separate and the time lag of the ester vs. the alcohol is used to estimate oil saturation in the near-well region. In this paper, we report a field test of a class of new reacting tracers for SWCTTs. In the test, approximately 100 cm of each of the new tracers was injected and used to assess oil saturation. In the test, ethyl acetate (EtAc) was used as a benchmark to verify the new tracers. This paper reviews the design and implementation of the test, highlights operational issues, provides a summary of the analyzed tracer curves, and gives a summary of the interpretation methodology used to find oil saturations from the tracer curves. Briefly summarized, we find the Sor measured by each of the novel tracers to compare with that from a conventional SWCTT. To validate stability and detectability of the tracers, a mass-balance assessment for the new tracers is compared with that of the conventional tracers. A benefit of the new tracers is the small amount needed. Methodological advantages resulting from using small amounts include the possibility to inject a mix of several tracers. Using several tracers with different partitioning coefficients enables probing of different depths of the reservoir. In addition, the robustness of SWCTTs can be increased by using several tracers, with different reaction rates and temperature sensitivity. The field trial also demonstrated that the new tracers have operational advantages. One benefit is the possibility to inject the new tracers as a short pulse of 10 minutes. Other benefits are that the small amounts needed reduce operational hazards and ease logistical handling.
Al-Ajmi, Moudi (KOC) | Pathak, Ashok (KOC) | Al-Otaibi, Basel (KOC) | Al-Mufarej, Mishal (KOC) | Ashkanani, Fatma (KOC) | Abdullah, Waleed (KOC) | El-Doushy, Ahmad (KOC) | Al-Hamer, Mohamad (KOC) | Al-Anzi, Ealian (KOC)
Abstract Front-tracking and monitoring of pattern water-flooding are crucial reservoir management activities in the Mauddud (MA) carbonate reservoir. This depletion drive reservoir has been on water flooding since 2000. To help understand the complex water movement that has been observed following implementation of the water floods, it is essential that water tracers be employed in MA injection wells. The use of tracer technology is becoming increasingly important to the petroleum industry and it has proven to be an efficient tool to investigate reservoir flow performance and reservoir properties that are controlling fluid displacement processes. Inter-well tracer has proven to be successful in identifying direct communication between the injection and production wells, flow patterns within the reservoir, thief zones, swept pore volume, reservoir layering, and flood performance. Tracer studies have also been used to complement the information provided by other reservoir characterization methods such as pulse and interference testing. Water tracers were employed in MA since 2007 at a pilot level, which is gradually expanding to full-scale implementation. Monitoring tracer breakthough information have provided invaluable information concerning the influence of faulting and stratigraphy on fluid migration within the reservoir which has been used to guide calibration/updating MA model and planning more tracer projects. The tracer data have been used to reduce the uncertainty attributed to well-to-well communications, and vertical and horizontal flow barriers. The study presented in this paper includes two injection wells which have been on waterflood since 2000. Different water tracers were injected in this field since 2007. Produced water samples were collected for tracer detection. This paper includes discussions on the implementation of tracers in a carbonate reservoir presenting detailed analysis and interpretation of the results.
Abstract This paper sheds light on the design of a Partitioning Interwell Tracer Test (PITT) for a normal 5-spot chemical EOR pilot targeting the Sabriyah Mauddud (SAMA) carbonate reservoir in Kuwait. This pilot is currently going through the water pre-flush phase which will be followed by chemical injection in the near future. Due to recent improvements in the synthesis of partitioning tracers, water-based partitioning tracers can now be utilized to evaluate variations in oil saturation pre and post EOR applications as well as interwell connectivity for chemical EOR pilots. A PITT is planned to take place in support of a normal 5-spot chemical EOR pilot in the SAMA reservoir. Four unique passive tracers will be injected into the pilot injectors prior to better understand reservoir conformance. This will be followed by the co-injection of four passive-partitioning tracer sets to evaluate oil saturation before and after chemical injection. A fit-for-purpose facility set-up has been installed to perform quasi-simultaneous injection of different tracer packages into the four EOR pilot injectors and a robust sampling strategy was developed to analyze the produced fluids from the pilot producer and sampling observation well in addition to other offset producers surrounding the pilot area. Periodic lab analyses involving techniques such as Gas Chromatography coupled with Mass Spectroscopy (GC-MS) will be performed to analyze tracer breakthrough times, peaks, dispersion and partitioning-passive tracer relationships. The findings from this PITT will be used to develop a comprehensive understanding of oil distribution and inter-well connectivity within the pilot area to assess the techno-economic feasibility of multi-pattern chemical EOR deployment. This PITT in a major carbonate reservoir is one of the first reported field cases to evaluate variations in oil saturation and interwell connectivity for subsurface chemical EOR applications in a normal 5-spot pattern pilot area.
Abstract A proposal to carry out a well to well chemical tracer test in the pilot area of a field with possibilities to implant an enhanced oil recovery (miscible CO2 injection) with two primary objectives:Detect injecting wells that cause salted water leak at 200 meters deep in well C1001. Monitoring the injected water front behavior in each injecting well inside pilot area to define if there is vertical communication between two reservoirs. Additional information could be possible to obtain with this tracer test as to identify the source of produced water in each producing well associated to each injecting well tagged, moreover, to measure irruption time, to identify channels or barriers that affect the fluid movement, to fix the main direction of front movement, to evaluate the front distribution inside each injection pattern in tested area and give support to field characterization in the pilot area. To achieve these objectives, it was necessary evaluate the tracers program proposed that start with selection of injection scheme with six injecting wells tagged (one in reservoir A, four in reservoir B and one in both reservoirs) with six different chemical tracers. We show the results of revision and analysis of each test include in tracers program and the investigation ratio adjustment used to monitoring protocol design, in which there were added several producing wells to be sampling and analyzing located inside the investigation ratio of each injecting well tagged with chemical tracer. Introduction In CO2 injection pilot area in this field, is being planning a tracers test with two objectives:Identify which injecting wells cause salted water leak at 200 meters deep in well C1001. Monitoring the injected water front behavior inside pilot area to obtain additional information: To identify vertical communication between two reservoirs in the field. To detect influence of each injecting well on each producing well in pilot area. To calculate irruption time. To identify channels or barriers in fluids movement. To recognize the main flux direction inside pilot area. To calculate swept efficiency. To be support in reservoir characterization. These two objectives are the base of proposal strategy to use well to well tracers in pilot area. Many field information help to make the design of the tracer test like previous tracer test in other areas in the field, pressure and production history data and behavior of the wells inside pilot area 1, 2, 3, 4, 5, 6. With clear objectives, next step in tracer test design is evaluation and optimization of tracer program, is necessary to fix different activities to assure data quality and results reliable in time. Tracer tests have three basic stages: Design, Execution and Interpretation. This work made the first stage, review and adjust original program, which was approached only to identify injecting well that cause salted water leak in well C1001(objective one)7, in such a way will be possible to reach objective two. The program adjusts was carried out in three phases: Injection proposal, Test upscaling and Monitoring protocol. Selection of injection scheme First injection proposal in pilot area was made for design area and tracers specialist Contractor Company, and suggest two possible injection schemes, both with 6 chemical tracers of Fluor benzoic acids family (FBA´s).
This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 94898, "Evaluation of Polymer-Injection Projects in Brazil," by M.A. de Melo, C.R.C. de Holleben, I.P.G. da Silva, A. de Barros Correia, G.A. da Silva, A.J. Rosa, A.G. Lins, and J.C. de Lima, Petrobras, prepared for the 2005 SPE Latin American and Caribbean Petroleum Engineering Conference, Rio de Janeiro, 20-23 June. Petrobras has implemented three polymer-injection pilot projects during the last 2 decades in the Canto do Amaro, Carmópolis, and Buracica onshore fields. The first one is in the middle of the operation, and the last two are finished. The main objective of the pilot projects was to gain practical knowledge of the process for possible future expansion to other reservoirs and even to offshore fields. Introduction The objective of polymer-injection projects is to increase the oil-recovery factor by reducing the mobility ratio between the water and the oil. The reduction in mobility ratio is achieved by increasing the viscosity of the aqueous phase, which increases the sweep efficiency and, hence, the oil recovery. Depending on the type of polymer used, this increase in viscosity also can cause a reduction in the effective permeability to water in the swept areas. This reduction in permeability has a secondary effect of restoring part of the reservoir pressure after polymer passage. The technical and economic success of the process depends on the correct selection of the reservoir and the specification and design of the polymer bank to be injected. Reservoirs and Pilot Areas The selection of Carmópolis, Buracica, and Canto do Amaro reservoirs was based on the criteria defined in the literature. By comparing average reservoir properties with the adopted screening guide, it can be seen that they fit all the criteria except for heterogeneity and clay content. Temperature and water salinity are two important process parameters. If the temperature and water salinity are greater than the specified values, the polymer can degrade. Oil saturation has to be above a minimum value for the process to be economically feasible. High clay content can increase adsorption of the polymer in the rock. This problem can be eliminated or minimized through laboratory tests to find a polymer compatible with rock conditions. The worst problem is the presence of faults, fractures, and preferential-flow channels. These heterogeneities can be identified by use of a tracer before using the polymer. After identification, these channels can be plugged by use of blocking polymers. Mobility ratio is the most important parameter to be considered because it will be affected directly by the polymer solution to increase the sweep efficiency and oil recovery. Polymer Selection In this phase, market research was performed to verify available products for this application. Synthetic and natural polymers were analyzed, and on the basis of cost, a partially hydrolyzed polyacrylamide was selected. After selection of the polymer, laboratory tests were performed to select the proper molar mass and degree of hydrolyzation on the basis of rock/fluid-interaction parameters. These parameters should be defined for each reservoir through specific laboratory tests. These tests were performed to evaluate compatibility of the polymeric solution with the reservoir rock and fluids and to deter-mine the parameters of rock/fluids interaction [e.g., adsorption, resistance factor (RF), and residual resistance factor (RRF)].