Miscible WAG Efficiency Assessment on a Large Mature Carbonate Field

Bourgeois, Marcel; Berrahmoun, Hocine; Attar, Maryam Mohamed Al; Boulenouar, Djilali; Hammadi, Djelloul; Romero, Carolina; Shi, Wen Zhong; Torrez, Maria Fernanda

doi:10.2118/207384-ms

Day 4 Thu, November 18, 2021 2021

DOI: 10.2118/207384-ms

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Miscible WAG Efficiency Assessment on a Large Mature Carbonate Field

Marcel Bourgeois

Hocine Berrahmoun

Maryam Mohamed Al Attar

et al.

Abstract: This paper is based on the analysis of miscible WAG for an onshore Middle-East field, with strongly undersaturated light oil. Water Alternate Gas operations have been ongoing for around 5 years, which is relatively recent compared to more than 40 years of production history. Goal of this work was to assess the efficiency of this miscible hydrocarbon WAG and to optimize it on the different compartments, with respect to miscibility, voidage replacement, and recycling. As this is a large mature fie… Show more

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Cited by 3 publications

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Joint Optimization of Oil Recovery and Carbon Intensity in a Middle-East Oil Field Under Miscible Water Alternating Gas

Blanchet,

Bourgeois,

Guérin

et al. 2023

Day 1 Mon, October 02, 2023

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This work investigates how the green-house gas (GHG) emissions of a producing oil field can be reduced through adaptation of the reservoir management, i.e. the injection and production guidelines. Indeed, the world’s energy production must be decarbonized as far as possible, and this includes minimization of the emissions associated to the oil and gas extraction itself. An additional decision criterion for oil and gas projects is the hydrocarbon carbon intensity, which is the emissions total divided by the production total, expressed in kgCO2eq/boe. The reservoir management strategies now attempt the joint optimization of all the following dimensions: net present value, short-term production, final recovery, and now oil carbon intensity. In some WAG fields, several controls are available even after the development is finalized: flow rates of both gas and water in each injector, duration of injection of each phase, possible conversion from WAG to water injection. A method has been devised to perform the joint optimization: a reservoir simulator is coupled with a surface model containing GHG emissions equations for compressors, pumps, turbines according to their throughputs. In brown fields, this emissions model can be calibrated on historical profiles and energy consumption per machine, while in green fields, a synthetical model can be built from theoretical operating curves and calibrated a posteriori. In this work, the method was applied on a giant Middle-East carbonate oil field under Miscible WAG injection. Numerous reservoir management scenarios were run, resulting in new production and injection profiles, together with their associated GHG emissions profiles, without the need for time-consuming loops between subsurface and development or exploitation teams. All scenarios were ranked in recovery and carbon intensity simultaneously. For the selected field, it was found that reservoir management actions can be strong levers to reduce the carbon intensity of the produced oil, where required – typically by 10% or more. The most efficient reservoir management actions for GHG reduction were those that reduce the gas injection rate and therefore the associated gas compression requirements. The actions did not impact the short- and mid-term oil production but lead to a reduction of one point of ultimate recovery. Reservoir management decisions must consequently be compromises between ultimate recovery, carbon intensity and net present value. The integrated production and emissions prediction tool proves extremely helpful to identify the relevant reservoir management scenarios, perform informed arbitration or enforce hard-fixed carbon intensity constraints.

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Joint Optimization of Oil Recovery and Carbon Intensity in a Middle-East Oil Field Under Miscible Water Alternating Gas

Blanchet,

Bourgeois,

Guérin

et al. 2023

Day 1 Mon, October 02, 2023

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New Possibilities with the Novel Modelling Approaches developed for WAG and FAWAG

Skauge,

Chang,

Sorbie

2023

Day 2 Tue, October 03, 2023

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There has been substantial development of modelling tools for viscous instabilities and multi-phase flow in recent years. This has enabled better opportunities of modelling near-miscible WAG (Water-Alternating-Gas), respecting gas fingers and simultaneously representing more correct phase mobilities. The objectives of this paper are to demonstrate advanced near miscible WAG modelling including WAG three-phase hysteresis, and present cases of Foam Assisted WAG (FAWAG) revisited with several novel modelling approaches. The numerical modelling has been performed using commercial reservoir simulators, STARS and GEM from CMG. The methodology of describing viscous fingering, analogue to Sorbie et al. (2020), is a 4-stage approach: (1) selection of fractional flow to maximize total mobility; (2) derivation of the relative permeability; (3) establishing an appropriate random correlated permeability field; and (4) simulating the process with a sufficiently fine grid. Simulations have been performed in 3D models using fine grid and random Gaussian permeability field. Three-phase fluid flow modeling used the GEM implemented version of Larsen and Skauge WAG hysteresis model, and the CMG foam model. We have used two differentrock permeability models, a standard vertical layered model, and a model with heterogeneous permeability within each layer. The fluid flow functions were either a conventional or a WAG hysteresis model respecting three-phase mobilities and phase trapping. The impact on gas finger development was analyzed and was based on simulation production data, but also on the in-situ fluid distribution. WAG hysteresis dampened to some degree the gas fingers but was able to show oil bank formation and enabled interpretation of in-situ fluid diversion. We have expanded the numerical modeling to include foam and specifically the foam assisted WAG (FAWAG) process. This is a revisit of an earlier study (Skauge et al. 2002 on Foam Assisted WAG, a Summary of Field Experience at the Snorre Field), but now updated with the novel modelling approaches. Many factors influence foam strength, with mobility reduction factor (MRF) as the key factor. We used the GEM version of foam description, with MRF as the main factor defining the foam properties. In this approach we were able to describe the reduction in GOR, but also the oil banking and consequently the extra oil production due to FAWAG injection. Simulation studies show that it is possible to include complex modelling in a commercial simulator. The advanced models enable a more correct history match of production and a more systematic analysis of local diversion of fluid flow due to WAG and FAWAG that would not be possible using a conventional approach. With the new approach, improved decisions for field development can be made.

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Using WAG Laboratory Data to Derisk Water Injection at the Gas-Oil Contact on a Giant Offshore Field

Bourgeois,

Satken,

Goyal

et al. 2024

Adipec

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The current development strategy of this field is focused on the oil rim, it involves downdip water injection and gas injection in the gas cap to maintain the pressure. A co-development of the oil rim with the large gas cap is being tested at pilot scale and considered at large scale, it requires to create a water fence or water barrier by injection water in updip position, near the gas cap, to isolate if possible oil rim and gas cap, and avoid oil movement into the gas cap. This should enable production of gas and condensate from the gas cap, and still continue simultaneous oil production of the oil rim. This co-development program requires drilling of numerous inner ring water injectors, the well count and placement need to be optimized with help of 3D simulation, which requires relevant flow functions (like KRs). This paper is focusing on the laboratory program followed to quantify these 3-phase flow functions, which happened to be very close to the SCAL program used to constrain WAG operations. Interesting findings related to these measures are presented and discussed. It was found that the near-miscible gas flood clearly outperformed waterflood, and the beneficial gas-oil interaction could be quantified. Three-phase flow (water and gas injection successively) clearly outperformed 2-phase flow, and a succession of several short slugs was also better than long slugs. Trapping of gas by water was also rather low, except if several cycles were followed. Water behavior was also quite surprising, as its mobility in presence of gas was measured higher than expected during imbibition, which implies to increase the water injection rates and water treatment facilities in order to maintain the water barrier in the project, but will also have implications on the water cut and eruptivity of oil producers in the oil rim. When water injection ceases, as in WAG operations when switching to gas, or for intermittent water injection, water mobility was found to be very low for the drainage phase, and water trapping was clearly documented despite rate bumps in the gas injection. This could be interpreted by hysteresis affecting also the water phase, and can be explained logically by water being the least wetting phase in an oil-wet near-miscible environment. This mechanism may be of importance, as it may stabilize the updip water fence if water injection rates are reduced.

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Miscible WAG Efficiency Assessment on a Large Mature Carbonate Field

Cited by 3 publications

References 6 publications

Joint Optimization of Oil Recovery and Carbon Intensity in a Middle-East Oil Field Under Miscible Water Alternating Gas

Joint Optimization of Oil Recovery and Carbon Intensity in a Middle-East Oil Field Under Miscible Water Alternating Gas

New Possibilities with the Novel Modelling Approaches developed for WAG and FAWAG

Using WAG Laboratory Data to Derisk Water Injection at the Gas-Oil Contact on a Giant Offshore Field

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