Title : Aquifer pump off (APO) meter improvement for higher ultimate recovery: An applications of lean approach methodology in a south oil field in oman
In a steam-flooded field in Oman, APO wells are drilled to reduce the influx of cold aquifer water into the reservoir and lower its pressure. The water is softened and used as Boiler Feed Water.
In 2021, APO meters reported a major deviation in meter reading from their design limit due to unknown deposit; resulting in an increase in Corrective Maintenance jobs, oil regrets in missing offtake target and pressure drop for steam-chest development.
To diagnose the root cause of the meter faulty reading and reduce its deviation from the observed (12%) to design limit of (5%); an accelerated lean approach known as Practical problem solving (PPS) was followed. This is a structured framework to understand the causes of a sudden behavior change in a defined step within a process. The analysis included outlining the “SIPOC”, i.e. defining the Suppliers, Inputs, Process, Outputs, Customers of this matter, a Detailed Process Mapping, fishbone analysis, the 5-whys, etc. The PPS findings were piloted on a selected well where Innovative technologies were used to verify the meters.
As part of the PPS countermeasures, several analyses have been taken to define the source of the deposits in the flowmeter internal surfaces:
• Sulphate-Reduced Bacteria Analysis (SRB): Found zero. No sign of bacteria in the water.
• Oil in water analysis (OIW): Found zero. No schmoo generation.
• Solubility test of Solid sample: Found no traces of oil.
• Corrosion Rate Hydro-core Analysis: Found Corrosion rate at 0.8 mm/year
With the absence of Schmoo formation, It was confirmed the reservoir formation was the source of the Sulphide. The iron was inspected in corrosion products. Thus, the Iron Sulphide formation led to the Prob blocking. Several solutions were taken:
1. Short-term Solution: Corrective maintenance crew deployed for frequent cleaning leading to a deviation reduction of 7% and using a portable clamp on meter to further verify the meter reading.
2. Long term Solution:
• Facility improvement proposal (FIP) put in place to upgrade the material selection and avoid the Iron Sulphide deposition in water.
• Replace any defected magnetic flowmeter by a permanent clamp on meter.
To sustain the PPS results and Findings: Visual Management Board (VMB) and Standard Operating Procedure (SOP) lean tools, were put in place for proactive follow-up and attendance.
Achieving more reliable APO meter reading resulted in more accurate flow allocation, hence better reservoir management . The PPS lean approach enabled the analysis to be effective and concise within a timely manner utilizing in-house resources. This is in line with field’s reservoir & facility management (WRFM) strategy.