Four main areas of uncertainty can be described in polymer-injection projects:1. Are we able to deliver the polymer solutions at the required quality to the wellhead? 2. Are we able to inject polymers at the required quantity and quality? 3. Are we producing sufficient incremental oil? 4. Are we able to separate and treat oil and water cost-effectively after polymer breakthrough? The monitoring program that was developed for the polymerinjection pilot aims to reduce the uncertainty and quickly identify operational difficulties, as described in the following:• Polymer quality at the wellhead: The polymer concentration and viscosity of the "source" solution and injected polymer solution were measured at various locations in the surface facilities. A quality check of the delivered polymer (including a filter ratio test of the dissolved polymer) was performed, the biological activity monitored, iron content measured, and polymer solution investigated for "fish eyes." The monitoring program enabled us to identify challenges related to shearing the polymers after changing the operating envelope, to identify problems related to biological activity, and to ensure data quality for interpretation of the pilot. • Injectivity and degradation: Monitoring involved wellheadand bottomhole-pressure measurements, repeated falloff tests, and visual observation of the polymer solutions in the well. The results showed the mobility reduction of the polymer solutions and an indication of induced fractures. Combining the various measurements led to identification of an operational issue-the injectivity decreased more than expected from polymer rheology and prepilot water-quality assessment. The reason was the combination of fines and small oil droplets existing in the injection water with polymer-and biologicalgenerated mass that plugged the pores during injection.
Polymer injection pilot projects aim at reducing the uncertainty and risk of full-field polymer flood implementation. The interpretation of polymer pilot projects is challenging owing to the complexity of the process and fluids moving out of the polymer pilot area. The interpretation is increasingly more complicated with the heterogeneity of the reservoir.In the polymer pilot performed in the 8 TH reservoir of the Matzen Field in Austria, a polymer injection well surrounded by a number of production wells was selected. A tracer was injected one week prior to polymer injection. The tracer showed that the flow-field in the reservoir was dramatically modified with increasing amounts of polymers injected. Despite short breakthrough times of 4-10 weeks observed for the tracer, polymer breakthrough occurred only after more than 12 months although injection and production rates have not been substantially changed.The tracer signal indicated that the reservoir is heterogeneous with high flow velocities occurring in high permeable layers. By injecting polymers, the mobility of the polymer augmented water was reduced compared with water injection and lead to flow diversion into adjacent layers. The tracer response showed that the speed of the tracer moving from injection to production wells was reduced with increasing amount of polymers injected.This response was used to assess the changes of the amount of water flowing from injection to production well. After a match for the tracer curve was obtained, adsorption, residual resistance factor and dispersivity were calculated. The results showed that even for heterogeneous reservoirs without having good conformance of the pilot, the critical parameters for polymer injection projects can be assessed by analyzing tracer and polymer response. These parameters are required to determine whether implementation of polymer injection at field scale is economically attractive.Along the flow path, an incremental recovery of about 8 % was achieved. The polymer retention and inaccessible pore volume in the reservoir was in the same range as in core floods. Incremental oil recovery owing to acceleration along the flow path was estimated at contributing to about 30 % to the overall incremental oil production due to polymer injection and 70 % to improved sweep efficiency.
Phase experiments were performed to determine an Alkali Surfactant Polymer solution leading to low interfacial tensions for oil produced from the 16 TH reservoir of the Matzen field in Austria. Core flood experiments with the ASP solution were conducted to investigate the incremental oil recovery. Experimental data was history matched utilizing numerical simulation. Results show that at laboratory scale, the various chemicals travel at different speeds owing to the different retardation. Owing to the short distance travelled, the location of the various chemical fronts is close together. Hence, the conditions in the core floods resemble the conditions in the phase experiments. At reservoir scale, however, even after only 0.2 Pore Volumes (PV) injected, a significant separation of the species is seen. Owing to the difference of the reservoir and core scale, chemical compositions need to be used which are leading to sufficient incremental oil for a wide range of compositions. The incremental oil production from ASP flooding can be substantially overestimated if the separation of the chemicals owing to retardation is not accounted for in the design of the chemical flood. In case that pseudo components are used in reservoir simulation, the components should have similar retardation characteristics to ensure that incremental recovery is not overestimated.
Four main areas of uncertainty can be described in polymer injection projects:1. Are we able to deliver the polymer solutions at the required quality to the wellhead? 2. Are we able to inject polymers at the required quantity and quality? 3. Are we producing sufficient incremental oil? 4. Are we able to cost-effectively separate, and treat oil and water after polymer breakthrough?The monitoring program which was developed for the polymer injection pilot aims at reducing the uncertainty and at fast identification of operational difficulties -details are described below:interpretation of the pilot related to conformance of the pilot could be resolved using this data. 4. Polymer, oil, water treatment: the surface facilities are constantly monitored for separation efficiency and plugging owing to back produced polymers. Operating challenges are seen in all treatment steps for full field polymer injection implementation due to separation but also handling of the polymers in water treatment facilities.
A compositional dynamic simulation model is fully implicitly integrated with a gas injection surface network model, to study the effects of CO2 injection into a depleted gas field. Multiple prediction scenarios are evaluated, under uncertainty, to reduce risk and improve decision making. We propose a workflow, composed of a geological sensitivity clustering step followed by a dynamic calibration step. The aim of this workflow is to decrease the objective function and improve the reliability of a probabilistic forecast, to model the CO2 storage potential of an onshore depleted gas field. Each run, containing all parameters and its objective function was exported and introduced into an inhouse R Script. Within this script we train a random forest tree to predict the objective function for various parameter combinations. This random forest is then used to generate 1 million models with the initial distribution from the simulation runs and will predict their objective function. The idea here is to get to a posterior distribution that can be used in the second simulation iteration. This method achieves a better history match within the ensemble, in a vastly reduced timeframe. History matched models were taken forward to predict CO2 injectivity. Injection variables, facilities and well completions for several wells have been included in the analysis, and numerical reservoir simulation models have been integrated with a surface network.
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.