Polymer flooding is a mature EOR technique successfully applied commercially in sandstone reservoirs and at the pilot stage in carbonate reservoirs. However, all previous pilots in carbonates reservoirs were implemented in relatively low temperature and low salinity conditions. No field application of polymer in carbonate was implemented in the last 25 years. In recent EOR screening studies for carbonate reservoirs in Abu Dhabi, polymer based EOR techniques were identified to target by-passed oil in heterogeneous/layered reservoirs The main challenges for polymer based EOR processes in ADNOC reservoirs is to find a stable polymer under the extreme conditions of high temperature/high salinity/high content of divalent cations which can be injected in carbonate reservoirs. An extensive laboratory program initiated 10 years ago led to the development of a polymer rich in Sodium Acrylamido tertiobutyl Sulfonate (ATBS). Thermal stability, bulk and in-situ rheology, adsorption and injectivity performed and the polymer was found suitable for the harsh conditions of ADNOC reservoirs. A de-risking strategy was designed in which a polymer injectivity test (PIT) followed by a multi well pilot are performed before the full field implementation of polymer based EOR for a number of ADNOC reservoirs. This paper describes in details the main steps of the successful PIT recently carried out including: the selection of the candidate well and the injection skid, the test design, its execution, the polymer solution quality management and the operational challenges faced during the pilot. The polymer Injectivity Test was conducted for 4 months and concluded by February 2020. A total of 150,000 barrels of viscous solution was successfully injected into the reservoir. This paper also details the real time surveillance and injection monitoring plans implemented during the test period for real time assessment of the skid delivery and the well response. This Injectivity test achieved the designed Key Performance Indicators related to polymer solution quality, viscosity, concentration, injection rate and skid running time. The dedicated surveillance and injection monitoring plan designed and implemented during this pilot, enables to confirm the good performance of the polymer during PIT period. Furthermore, PIT results showed good performance of Polymer in terms of viscosity, Injectivity at target rate and concentration. This paper also addresses the impact of water quality on polymer viscosity and skid operation. This paper presents field results for a new polymer developed for carbonate reservoirs at HT/HS. This successful Polymer Injectivity test qualified the new polymer for field application at harsh carbonate reservoir conditions. Results from this world first Injectivity test opens a new area of possibilities to improve recovery in giant heterogeneous carbonate reservoirs in ADNOC and in the Middle East.
Production planning and performance management imply diverse challenges, mainly when dealing at corporate level in an integrated operating company. Production forecast considers technical capacities, available capacities, and operationally agreed target capacities. Such complex process may hinder taking advantage of market opportunities at the right time. Proactive scenario management and information visibility across the organization are key for success. This paper intends to share the lessons learned while rolling out a countrywide integrated capacity model solution supporting corporate production planning and performance management. The rollout processes aimed at digitizing the monthly and yearly production forecasting. In addition, these processes shall enable formulating proactive scenarios for avoiding shortfalls, maximizing gas throughput, production ramp up, and minimizing operating cost from existing capacity. Abu Dhabi's Integrated Capacity Model is an integrated production planning and optimization system relying on a large-scale subsurface-to-surface integrated asset model system; in this paper, we focus on the incremental progress of the challenges derived from the various rollout efforts. The rollout of such a complex solution relies on basic tenets for managing the change across a large organization. The first tactic is about continuous stakeholder engagement through value demonstration and capabilities building. Engagement is achieved by continuously providing information about proactive shortfall and opportunity identification within the installed asset capacity. Monthly asset reviews provide the basis for user interaction and initiate the basis for establishing ad-hoc production maximization scenarios. Establishing a data governance and performance metrics were also key for embedding the solution in the business processes. The solution delivers tangible and intangible value. From the tangible point of view, it contributes to production efficiency gains by compensating during specific proactively identified shortfalls and after-the-fact events. As a result, our solution has been instrumental in deriving cost reduction scenarios and profitability gains due to optimum GOR management. In addition, the system use has reported various intangible gains in terms of better data utilization, enhanced corporate database quality and reduced overall human load in managing production capacity. The solution described in the paper implements a simpler way the production planning and performance management at corporate level in a large integrated operating company. The in-house developed tool and its implementation is a novel approach in terms of integration, complexity, and practical application to the fields in Abu Dhabi.
In this paper, we investigate the potential for applying miscible nitrogen injection as an enhanced oil recovery (EOR) method for a high-temperature, low-permeability carbonate reservoir, which contains a volatile oil with some H2S and CO2. The field, which is located onshore Abu Dhabi, is still in its early development phases but suffers from relatively low throughput rate because of low permeability. Various gas injection schemes are being considered, with different source gases. At the prevailing reservoir pressures, extensive phase behavior studies confirm that the reservoir fluids develop miscibility with nitrogen, carbon dioxide, and hydrocarbon gas. The simulation studies involve a number of sensitivity runs performed on sector models, which are sufficiently fine-gridded to capture the compositional transition zone propagating between injector and producer pairs. Miscible nitrogen injection comes out as a viable option with the potential to increase recovery by 10 to 20% above the current water flood development scheme. The significantly improved sweep and displacement efficiency are due to N2 miscibility with reservoir oil under reservoir conditions, possibility of increased PV injected in a N2 WAG scheme, and the ability to maintain a higher reservoir pressure (at initial reservoir pressure). From a surface facilities point of view, techniques for N2 capturing is mature, tried and tested. N2 being inert does not pose corrosion risks to well completion and surface facilities. However, capital costs for N2 rejection units – if utilised in a N2 WAG EOR scheme – will need to be taken into account. Although N2 WAG EOR is seen to be very attractive for the reservoir under study, alternative EOR schemes are also being actively evaluated. The aim is to arrive at an optimum EOR project for the reservoir in line the achieving the 70% oil recovery aspiration.
Development of giant offshore carbonate field with more than 400 oil producers and 300 water injectors are very complex without proper production optimization tool to reach sustainable production and optimize the cost of the investment for future development. Construction of IAM model for short term optimization purposes brings vital outcomes which can identify the short and long term optimizations scenarios and as a consequences reduce the investment with the maximum outcome of production within the reservoir management guidelines of the field. Integrated asset modelling tool (PSO-production system optimization tool Prosper+Gap) is ideal tool which can provide the best production optimization results to develop the giant field with all reservoir guidelines and production system bottleneck. One of the main achievement of integrated asset model (PSO) for a giant carbonate oil field is the fact that its fully compositional model which allows to track oil composition change at any point of the surface facility, which is critical for fields under secondary recovery mechanisms with water and gas injection.
Miscible gas injection EOR is a well-established and proven recovery mechanism. There are a large number of miscible gas injection EOR developments worldwide. Some of these developments achieved relatively high recoveries. ADNOC is a leader in miscible gas injection EOR in carbonate reservoirs - with a number of developments within its portfolio contributing substantially towards ADNCO overall production. For miscible gas injection EOR developments, especially in relatively low permeability carbonate reservoirs, the following are recognised as key field development planning and reservoir monitoring/management areas: Development pattern, number and location of injectors in relation to producersSufficient injection rate and volume, to maintain reservoir pressure and optimise sweepReservoir monitoring and production management, to ensure adequate data acquisition and studies to support field development and production decisions in a timely manner. In relatively tight carbonate reservoirs, injection well injectivity is a critical factor when addressing the above three key areas. Water injection injectivity is fairly well understood, but gas injection injectivity in a miscible setting can be very complex. The complexity can be attributed to a combination of factors, for example: The dependence of injection gas property parameters on downhole injection pressure and temperatureDevelopment of the miscible oil bank via either vaporising or/and condensing mechanismVapour phase being significantly more mobile than reservoir liquid oil and waterWhere applicable, gravity segregation in areas surrounding the injectorReservoir wettability and hysteresis. An assessment into miscible gas EOR injection injectivity for relatively low permeability carbonate reservoirs has been performed. Actual field injection data (both water injection phase and gas injection phase) from 3 reservoirs were analysed. A compositional sector model was also used. Injectivity evolution trends were discussed, and potential influencing factors identified. Recommendations on best practices for WAG injector injectivity monitoring, reservoir voidage replacement calculations are provided.
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