This paper discusses the design and application of an alkaline-surfactant-polymer (ASP) system for the West Salym field in West Siberia. The discussion in the paper focuses on surfactant selection, and less on polymer selection. The optimum surfactant system for the West Salym crude is a combination of IOS 24-28 (internal olefin sulfonate with a tail length of 24-28 C-atoms) and IOS 15-18 and also includes an alcohol as co-solvent. The IOS surfactants are manufactured commercially by Shell Chemicals as the ENORDET™ O series. In an accompanying paper1 the properties of the IOS family of surfactants are discussed in more detail. For optimum performance, the surfactant needs to be tailored to the crude oil. Although the oil is not too heavy (API density is 30), and has a near-zero TAN, it contains a significant fraction of heavier components such as asphaltenes and resins, which are surface active and can interfere with the surfactant in the oil-brine interfacial layer. It is discussed in the paper how the crude oil composition affects the surfactant selection process. From test results and theoretical considerations, it was concluded that these types of crude require a surfactant with a long alkyl tail, such as an IOS 24-28. Further optimisation of the surfactant formulation was based on phase behaviour, surfactant solubility and core flow tests. To adjust optimal salinity, and to improve solubilisation, a co-surfactant (IOS 15-18) and an alcohol (2-butanol) were also added. Polymer tests were performed as part of the ASP design program. The purpose was to optimise the ASP/oil mobility ratio. Based on filtration and rheology tests, a hydrolysed poly-acrylamide polymer with a molecular weight in the range 5-8 million was selected. The optimised ASP system was tested in the field in a single well chemical tracer (SWCT) test. The test design, execution and result will be discussed in the paper. The goal of the SWCT test was to measure -under field conditions- the ability of the ASP system to reduce the residual oil saturation. A tracer test was performed, to measure remaining oil saturation (ROS), before and after ASP injection. The test was executed successfully. Analysis of tracer response indicated that 90% of the ROS after waterflood was mobilized by the ASP flood.
This paper discusses the design and application of an alkaline-surfactant-polymer (ASP) system for the West Salym field in West Siberia. The discussion in the paper focuses on surfactant selection, and less on polymer selection. The optimum surfactant system for the West Salym crude is a combination of IOS 24-28 (internal olefin sulfonate with a tail length of 24-28 C-atoms) and IOS 15-18 and also includes an alcohol as co-solvent. The IOS surfactants are manufactured commercially by Shell Chemicals as the ENORDET TM O series. In an accompanying paper 1 the properties of the IOS family of surfactants are discussed in more detail.For optimum performance, the surfactant needs to be tailored to the crude oil. Although the oil is not too heavy (API density is 30), and has a near-zero TAN, it contains a significant fraction of heavier components such as asphaltenes and resins, which are surface active and can interfere with the surfactant in the oil-brine interfacial layer. It is discussed in the paper how the crude oil composition affects the surfactant selection process. From test results and theoretical considerations, it was concluded that these types of crude require a surfactant with a long alkyl tail, such as an IOS 24-28. Further optimisation of the surfactant formulation was based on phase behaviour, surfactant solubility and core flow tests. To adjust optimal salinity, and to improve solubilisation, a co-surfactant (IOS 15-18) and an alcohol (2-butanol) were also added.Polymer tests were performed as part of the ASP design program. The purpose was to optimise the ASP/oil mobility ratio. Based on filtration and rheology tests, a hydrolysed poly-acrylamide polymer with a molecular weight in the range 5-8 million was selected.The optimised ASP system was tested in the field in a single well chemical tracer (SWCT) test. The test design, execution and result will be discussed in the paper. The goal of the SWCT test was to measure -under field conditions-the ability of the ASP system to reduce the residual oil saturation. A tracer test was performed, to measure remaining oil saturation (ROS), before and after ASP injection. The test was executed successfully. Analysis of tracer response indicated that 90% of the ROS after waterflood was mobilized by the ASP flood.
The Champion field is a large offshore oil field in Brunei Darussalam, which has been on production since 1972. The field is complex both geologically and in terms of the production system. The reservoir has over 500 stacked sandstone reservoirs across 15 fault blocks. Over time production facilities have increased to 40 surface structures supporting production and processing from over 1300 completion intervals. Although the field is considered a mature field and with aging facilities, there is a clear long-term vision to rejuvenate the field to sustain production for another 30 years through re-development and expansion of the water injection scheme.Ongoing maturation of the waterflood project is supported by continuous Reservoir Performance Reviews (RPRs). The RPRs bring together the reservoir understanding, hydrocarbon saturations and production data. The purpose of the RPRs is to identify opportunities -restoration, acceleration and reserves addition and compile them in an integrated development plan covering the short, mid and long term. RPRs are carried out at the flow unit level -a small group of commingled reservoirs within a single fault block.Top Quartile Recovery Factor (TQ RF) analysis is an integral part of the RPR. With the Top Quartile Estimated Ultimate Recovery (TQ EUR) tool, Shell developed a benchmarking tool which provides a conceptual framework that probes the performance of each field in a consistent manner. Basic geological and fluid properties as well as economic parameters are used to determine a complexity factor for each flow unit. The current and expected ultimate RF of the unit is then compared to the TQ RF (from reservoirs of the same complexity).A systematic approach is taken to bridge the gap to TQ RF. Closed-in well reviews identify restoration and water injection candidates. Deterministic analysis of sweep patterns and high remaining oil saturations are compared with streamlines in the NFA forecast model. Potential gains are quantified by the simulator. The outcomes are near-, mid-and long-term surveillance and development plans to move the recovery up to TQ and beyond to the technical limit (TL).By applying this systematic RPR/TQ process per flow unit across the whole field, a detailed reservoir understanding of this giant, complex field is achieved. This approach enabled the integrated WRFM team
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