Mature carbonate reservoirs under waterflood in Kuwait suffer from relatively low oil recovery due to poor volumetric sweep efficiency, both areal, vertically, and microscopically. An Alkaline-Surfactant-Polymer (ASP) pilot using a regular five-spot well pattern is in progress targeting the Sabriyah Mauddud (SAMA) reservoir in pursuit of reserves growth and production sustainability. SAMA suffers from reservoir heterogeneities mainly associated with permeability contrast which may be improved with a conformance treatment to de-risk pre-mature breakthrough of water and chemical EOR agents in preparation for subsequent ASP injection and to improve reservoir contact by the injected fluids. Each of the four injection wells in the SAMA ASP pilot was treated with a chemical conformance improvement formulation. A high viscosity polymer solution (HVPS) of 200 cP was injected prior to a gelant formulation consisting of P300 polymer and X1050 crosslinker. After a shut-in period, wells were then returned to water injection. Injection of high viscosity polymer solution (HVPS) at the four injection wells showed no increase in injection pressure and occurred higher than expected injection rates. Early breakthrough of polymer was observed at SA-0561 production well from three of the four injection wells. No appreciable change in oil cut was observed. HVPS did not improve volumetric sweep efficiency based on the injection and production data. Gel treatment to improve the volumetric conformance of the four injection wells resulted in all the injection wells showing increased of injection pressure from approximately 3000 psi to 3600 psi while injecting at a constant rate of approximately 2,000 bb/day/well. Injection profiles from each of the injection well ILTs showed increased injection into lower-capacity zones and decreased injection into high-capacity zones. Inter-well tracer testing showed delayed tracer breakthrough at the center SA-0561 production well from each of the four injection wells after gel placement. SA-0561 produced average daily produced temperature increased from approximately 40°C to over 50°C. SA-0561 oil cuts increased up to almost 12% from negligible oil sheen prior to gel treatments. Gel treatment improved volumetric sweep efficiency in the SAMA SAP pilot area.
Selecting a proper initial input for Iterative Learning Control (ILC) algorithms has been shown to offer faster learning speed compared to the same theories if a system starts from blind. Iterative Learning Control is a control technique that uses previous successive projections to update the following execution/trial input such that a reference is followed to a high precision. In ILC, convergence of the error is generally highly dependent on the initial choice of input applied to the plant, thus a good choice of initial start would make learning faster and as a consequence the error tends to zero faster as well. Here in this paper, an upper limit to the initial choice construction for the input signal for trial 1 is set such that the system would not tend to respond aggressively due to the uncertainty that lies in high frequencies. The provided limit is found in term of singular values and simulation results obtained illustrate the theory behind.
There are ongoing efforts to assess the techno-ecnomic viability of surfactant polymer (SP) flooding to increase oil recovery by improving microscopic and macroscopic sweep efficiency. This paper sheds light on a methodology to design an appropriate SP formulation for potential deployment in the Ratqa Lower Fars (RQLF) heavy oil reservoir in Kuwait. Besides achieving low residual oil saturation due to SP flooding under typical RQLF reservoir conditions, this study focuses on mitigating surfactant retention. Several injection strategies were investigated using alkali, adsorption inhibitors and a variety of water treatment techniques. For each scenario, a specific SP formulation was designed and evaluated through static adsorption tests using crushed reservoir rock. The two most promising options were then evaluated through coreflood experiments. The best option was selected based on in-depth chemical propagation, oil desaturation and surfactant adsorption. Finally, lab-optimization work was performed through additional corefloods to reduce chemical consumption while maintaining favorable oil recovery. Softened seawater obtained through reverse osmosis was considered as the most appropriate water source to implement the desired SP process. Previous work revealed that the use of unsoftened seawater results in high levels of surfactant adsorption on reservoir rock. Salt addition allows applying an efficient salinity gradient post SP injection. Sodium chloride was used instead of alkali which did not exhibit any benefit in this case. A particular effort was made to reduce the amount of added salt and the corresponding formulation cost. Several injection sequences were investigated to compare polymer and SP flooding. The final coreflood experiment based on SP injection (0.6 PV of surfactant at 4 g/l), followed by a salinity gradient, and involving a polymer drive recovered 80% of the original oil in place. The promising performance of this injection sequence will be further evaluated using the results from a one-spot EOR pilot. This EOR study on the RQLF shallow heavy oil reservoir in Kuwait provides important insights to select an appropriate surfactant-polymer injection strategy to increase oil recovery while maintaining reduced adsorption levels, thereby improving SP techno-economic viability.
Alkaline-Surfactant-Polymer Flooding (ASP) has the potential to unlock massive oil reserves in quest of production sustenance within the bounds of profitable economics. Field results from a successful ASP pilot targeting the massive Sabriyah Mauddud (SAMA) reservoir in Kuwait, using a regular five-spot with five acre-spacing are encouraging. Oil cut post softened water pre-flushing reached 0% and tracer data indicated pre-mature breakthrough at the central producer. This necessitated in-depth conformance gel treatment1-3 to induce flow under matrix conditions and softened water injection resumed thereafter for a period of ~3 months, during which oil cut ranged between 2 to 6%. Oil cut then decreased to 0% again, beyond which polymer pre-flushing was introduced for a period of ~2 months, during which oil cut was increased to up to ~4%. ASP flooding resulted in an unambiguous and sustainable increase in oil cut with an average of ~12% over a period of more than 6 months. Furthermore, daily oil production rate after ASP flooding more than doubled. Effective oil-water separation of produced emulsion has been established and maintained using fit-for-purpose pre-heating, chemical dosing and gravity segregation technologies, thus resulting in relatively low BS&W levels in separated oil (i.e., <5%). Potential in-situ scale risks were effectively managed by injection an innovative scale inhibition package composed of inhibited glacial acetic acid in conjunction with a phosphonate-polymeric scale inhibitor into the capillary tubing string of the central producer, during which 100% production uptime was achieved for several months3. Field data demonstrated that in-situ scale risks due to ASP injection were originally overstated because scale issues were limited even without injecting the adopted scale inhibition package. ASP reservoir simulation forecasts indicate that oil rates and oil cut should continue to increase. ASP flooding is ongoing to date and continues to generate important operational learnings and priceless field data to evaluate the techno-economic viability of phased ASP flooding commercial development.
A regular 5-spot Alkaline Surfactant Polymer (ASP) pilot is planned for a giant carbonate reservoir in Kuwait where a suitable formulation compatible with harsh salinity and temperature conditions was developed. However, it is vital to address uncertainties introduced through historical development schemes that are not necessarily compatible with original EOR plans. This paper sheds light on the importance of incorporating water flooding data and learnings to optimize the design of subsequent EOR deployment. An integrated workflow was adopted involving acquisition and analysis of relevant surveillance data to establish a solid understanding of water flooding preceding EOR deployment. The considered surveillance data covered pressure responses, rates, a variety of passive tracers, injection step rate tests followed by fall off tests, production/injection logs, high precision temperature logs, spectral noise logs and water injection into reservoir cores. The extent of thermal and reservoir depletion effects on reducing fracture initiation pressure was also investigated. The study focuses first on understanding the microscopic and macroscopic aspects underlying overall sweep efficiency due to water flooding, a key requirement to upscale the Pilot results to full field development. The macroscopic sweep efficiency was found to be strongly affected by the native permeability contrast attributed to geological heterogeneities as well as induced fractures. Induced fractures were triggered by different mechanisms related to cold water injection, reservoir pressure depletion, injected water quality and relatively high injection rates targets for a comparatively low permeability carbonate reservoir. The findings related to induced fractures have a well-established impact on the design and operating philosophy of the desired ASP Pilot with relatively short well spacing and active surrounding production/injection wells. Premature breakthrough of chemical injectants will not only impact the sweep efficiency of ASP flooding, but will potentially bring about operational complications due to inorganic scaling and produced fluids separation, thus introducing additional uncertainties in relation to the acquisition and interpretation of the Pilot data. The original Pilot design is being revisited by means of an integrated workflow to better understand and adequately mitigate poor conformance challenges during the softened water injection phase that will be followed by the ASP injection phase using a fit-for-purpose surveillance program. This workflow involves geological characterization and detailed analysis of water flooding performance in pursuit of improved conformance control to pave the way for efficient ASP flooding. The findings of this study underscore the importance of integrated field development planning and comprehensive surveillance to derive important waterflooding insights that can be used to de-risk ASP flooding under harsh reservoir conditions.
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.
hi@scite.ai
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.