Case Study: How the Newest Generation of Autonomous Inflow Control Device Helps to Control Excessive Wells Water Production within a Major Sultanate of Oman Oilfield

Abstract

The field is located in the south of Sultanate of Oman and was discovered in 1980 The field produces from sandstone reservoirs a heavy crude with high viscosity (up to 2000 cP) value that contains no appreciable solution gas. Production is supported by a bottom active water drive aquifer. An unfavourable mobility contrast between the oil and formation water results in rapid water breakthrough and a large portion of a well's reserves are produced at high water cuts. The average economic limit of wells in the field is about 98% water cut. Thus, water management plays a key role in well economics. The new horizontal producer wells target is to drain by-passed oil with only 30 ~ 80 m spacing. Injectors are at the flank and are injecting deep into the aquifer. Water breakthrough occurs at high sand permeability and once happened; water will dominate well production due to unfavourable mobility ratio. Some of the new producer wells are completed with Wire-Wrapped Screen (WWS) – Stand Alone Screen, and swellable packers to isolate higher water-saturated zones. However, most of these wells start typically with a 60% water cut (BSW) or more and rapidly reach +90%. To overcome current reservoir/production challenges; The operator has used the latest Autonomous Inflow Control Device (AICD) Technology called Autonomous Inflow Control Valves (AICV). ICD's and previous generation Autonomous Inflow Control Devices (AICD) has shown in many cases increased oil production and higher recovery with better fluid influx balance along the well. However, neither ICD nor AICD can shut off the water production completely without well intervention. The AICV can restrict unwanted water significantly and autonomously. The AICV are based on different flow behaviour for laminar and turbulent flow that is utilized in a pilot flow to actuate a piston position to restrict unwanted fluids. The design with two parallel flow paths ensures the AICV is open for oil, and close for water autonomously. The AICV technology is based on Hagen-Poiseuille and Bernoulli's principles and is truly autonomous as it can identify the fluid flowing through it based on fluid properties such as viscosity, density and flowrate. For unwanted fluid such as water and Gas, AICV can generate enough force that will shut off the device if required. This makes it more robust than any other commercially available AICDs. AICV effect is reversible i.e. when the saturation of unwanted fluid (Sg or Sw) around the wellbore reduces, AICV will re-open for the oil production, thus draining all possible oil around the wellbore. In this paper, AICV performance will be discussed and comparative analysis with production performance of wells completed with WWS completed in the same reservoir will be presented. Based on the regular well testing and production analysis, it is evident that AICV technology has helped the operator in managing/shutting off the unwanted water production autonomously. This new AICV technology has the core application principles of ICD completions but the additional benefit of improved control/complete water shut-off without intervention; zero cost water shut-off operation and helps drain by-passed oil and thus maximizes recovery factors.