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Abstract
Value addition via real-time reservoir monitoring and optimisation is one of the main drivers for the increasing implementation of intelligent (I-)well completions. The benefits
from these more expensive completions will be realized through increased reserves generated by increased drainage efficiency and reduction in well numbers and intervention frequency. A more rigorous exploitation of the real time production data is necessary to fully achieve this objective.
We previously showed that water influx time and source could be detected in horizontal wells in real time1. Extension of this technique will be shown to allow confident detection of water influx in vertical or deviated, multi-zone and/or multi-lateral I-well completions. The source of water influx into the well and the zonal fluid contribution will be quantified, allowing this unwanted fluid's production to be reduced. Knowledge of the influx time and source permits both production optimisation and improved reservoir sweep efficiency; processes that increase the well's productive life and reserves.
It will be demonstrated that monitoring of the pressure drop, called dP trending in this paper, across multiple pressure sensors correctly located within a multi-zone vertical or
deviated I-completion can identify the time and location of the water influx into the well. We will discuss the necessary conditions to ensure clear identification of these parameters.
The concept of “Normalised Pressure Drop Signatures" will be introduced. It has proven to be particularly valuable for water influx detection and zonal flow rate monitoring purposes. The concept will be tested with data generated from a synthetic model of a 4-zone, deviated, I-well completion and with realfield data from an instrumented North Sea well.
Introduction
Reservoir Management includes the tasks of monitoring subsurface and surface data in order to control a fluid flood front’s movement within a reservoir to maximize reserves and reduce production risks2. The installation of advanced, complex completions has added a further dimension to the Reservoir Management process. Such I-completions provide the platform for real-time reservoir monitoring and reservoir control via both active 3 and proactive 4 management of the influx of unwanted fluids.
Early water or gas breakthrough due to uneven fluid-front advance towards the well is observed in the higher permeability zones of heterogeneous and layered reservoirs. The need to reduce a well’s excessive gas production includes the maintenance of the reservoir energy and the avoidance of exceeding the gas disposal capacity. The consequences of excessive water influx include1, 2:
• Reduced well outflow performance as the increasing required tubing intake requirement reduces the well’s outflow performance.
• Reduced well productivity index due to early onset of multiphase flow in the reservoir;
• Early installation of artificial lift, resulting in increased Capital and Operating Expenditure;
• Production problems with their associated increased well and surface facility costs from corrosion, scale formation, sand management issues, etc.;
• Environmental issues from the need to dispose of unnecessarily large, produced water volumes;
• Reduced well productive life and reserves.
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