This paper sheds some light on the emerging EOR recovery mechanism related to modified ionic design of the injected water, sometimes referred to as low salinity or smart water EOR process. Many laboratory water-flooding experiments have been conducted with mixed outcomes on the benefit of the technology. Relative to the existing field applications in sandstones, this technology is less mature in carbonates. Many researchers support the theory that this process is very complex in carbonates and chemical reactions within productions time-scale are not well-understood. The literature lacks the connection between what researchers address in laboratory work and considerations for full-field applications. Therefore, this work aims to bridge some gaps between what is considered in experiments and what is relative to full-field applications. The paper offers a comprehensive review of the risk management framework related to the application of Low Salinity EOR process in offshore carbonates reservoirs in the UAE. Some risks/opportunities related to subsurface, flow assurance, surface facilities and operations will be addressed. The work presents an example of a risk matrix and remedial actions that must be considered during the design phase. For example, the root causes of souring, scaling, anhydrite participation, nepthenate solid precipitation and divalent cation migration will be presented and their possible impact on flow assurance will be addressed during the application of the low salinity flooding on different types of carbonate rocks. Furthermore, uncertainties related to pore-volume contact to reach the threshold salinity, temperature/cooling impact and chemical modelling limitations are addressed and related to the quantifications of the technology benefits as the study evolves from lab work, field trials and eventually to full-field applications. With such visibility of the full spectrum of the technology impact, laboratory experiments can be tuned with the focus to minimize specific risks and maximize benefits to the addressed field.
Over the last several years, improved recovery, especially in depleted reservoirs, has prompted many research projects involving operators, service companies and academicians. Recent work on rock-brinehydrocarbon interactions has demonstrated that carefully designed low salinity water injection in carbonate reservoirs has the potential for enhancing oil recovery as much as 15% compared with conventional treated sea-water or produced water injection. The implementation of this step-changing technology requires studies carried out on in-situ condition cores. Ultra-low invasion drilling fluids must therefore be used during the coring process, to preserve the formation in its original state, without altering its fluids composition, water saturation or wettability properties. This paper outlines the philosophies and criteria brought to reservoir coring fluids design, development and application of an All-Oil synthetic-based coring fluid.An All-Oil coring fluid with ultra-low invasion characteristics was developed after extensive lab testing. The fluid properties were optimized based on reservoir properties and challenging bottomhole conditions, which are presented in this paper along with design criteria, fluid characteristics, fluid development methodology, benefits, benchmarks set initially and field application details. Excellent multi-segments collaboration and team work during core planning, fluid development work and on-site fluid maintenance to achieve planned parameters led to operational success and are described in the paper.For the first time in UAE, a major offshore operator cut the cores with ultra-low invasion All-Oil Coring Fluid, which provided excellent stability to coring parameters and performance. The cores were recovered, processed and preserved in as close in-situ condition as possible, eliminating water contamination and preserving the core integrity, all of which are the basic essentials to achieve successful specialised formation flooding studies leading to the EOR Project. 520 feet of cores were cut in the reservoir section over 9 runs, with 100% recovery of high quality and uncontaminated cores. The cores were slabbed, plugged, photographed, packed, waxed and preserved successfully on site for transportation to lab for flooding studies.The fluids' outstanding performance that helped in achieving the coring objectives in this new coring strategy are discussed in the paper and lessons learned are contrasted with conceptual design for future optimisation. Laboratory test results are also presented which formed the basis of a well planned field application.
Single-well chemical tracer tests (SWCTT) have proven to be a valuable technique for evaluating Enhanced Oil Recovery (EOR) responses in clastic reservoirs. Development of carbonate waterflood EOR technologies are relatively immature in comparison, but the use of SWCTT for providing evidential basis in the field promises to be quick and relatively inexpensive compared with inter-well trials. SWCTTs measure the remaining oil saturation (Sor) to waterflood at a 15-20 feet distance from the wellbore. The technique indirectly measures the Sor by analysing back-produced fluids for partitioning tracers in a well which is producing at 100% water cut. Completing the test pre- and post-EOR treatment quantifies the EOR benefit, at least in that near-well region. Laboratory studies suggest that the use of ionically designed waters for EOR in carbonate reservoirs is temperature sensitive. This makes the design of a single-well test complex as it is essential to understand the thermal behavior of the well and the near-wellbore reservoir during any sequence of SWCTTs. Commercial simulators were used to investigate the thermal characteristics of the well and the near-wellbore reservoir respectively. These simulation results were also benchmarked against a water injection trial in another analogous well. The results showed that to ensure the temperature in the near-well region is kept sufficiently high to trigger an EOR response, it is necessary to pre-heat the injection water to >100°C. This is a complex operation especially offshore where the technical and HSE considerations need to be integrated into a sufficiently-sized heating system where space may be limited. Artificial lifting of produced fluids from a well which is producing at 100% water is also problematic offshore. Benefits and drawbacks of various lift options will be reviewed. The effect that delays during the production phase can have on the quality of data from the SWCTT will be shown as well as the options considered to reduce the likelihood of such problems occurring. The need to test this EOR technique in a controlled manner places stringent requirements on the surface facilities to deliver a test within the design specification. The need for low salinity water injection led to the selection of an integrated water treatment system able to produce desalinated water on-demand. This paper is the first of a series of papers aimed at describing the development of an ionically designed waterflood EOR technology for a giant carbonate oil field.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.