Case Studies

Water Shut-Off for Medium Oil

ICDs and AICDs can delay breakthrough but not stop the production of unwanted fluids completely. The newest generation of inflow control technology, the AICV®, can optimize oil production in both new and old wells and reduce water cut and gas ratio significantly.

Objectives
One of the main challenges for increased oil recovery is major breakthrough of unwanted fluids as water and gas, due to uneven influx along the horizontal section. The problem can be avoided or significantly reduced by deploying novel inflow control technologies. Inflow Control Devices (ICD) and Autonomous Inflow Control Devices (AICD) are able to delay breakthrough, but not stop the production of unwanted fluids completely. The newest generation of inflow control technology, the Autonomous Inflow Control Valves (AICV®) can optimize the oil production, in both new and old wells, and reduce water cut and/or gas oil ratio significantly. The benefit of the AICV® is to provide balanced inflow of oil along a horizontal well, by autonomously choke or close the breakthrough compartments, and still produce from the rest of the reservoir.
 
Approach
The commercial near-well simulation tool, NETool, is used to model a horizontal section with uneven influx along the well. Completion with 16 evenly distributed AICVs in 8 isolated zones is compared to an open hole situation and completion with nozzle ICDs. Simulation of one medium viscosity oil reservoir with water choking, and one light oil reservoir with gas shut-off are performed to demonstrate the increased oil production and recovery by implementing AICV® technology. In NETool several models of different types of inflow control are available, including the model of Statoil’s Rate Controlled Production (RCP). In this study, the RCP function is tuned to fit the experimentally determined flow performance behavior of the AICV® and the function is utilized in the applied simulation.
 
Result
A good correlation of the experimentally flow performance curves and the flow performance behavior of the tuned RCP function is obtained. The tuned RCP function gives a realistic assumption of the functionality of the AICV®, and shows that the potential of increased oil production and recovery is significantly in a range of reservoirs. The simulation result shows that for the medium oil reservoir the water cut (WC) is decreased from 60% with use of open hole completion to 29% for the situation with AICVs installed. The well completed with AICVs increase the oil production with 75%. In the light oil reservoir, the AICV® closes the gas breakthrough compartments completely, and increases the oil production from the other zones. The Gas Oil Ratio (GOR) is dramatically reduced from 1281 Sm³/Sm³ for the open hole situation, to 57 Sm³/Sm³ with AICV® completion. In both cases a simulation of a nozzle ICD is performed, showing that the performance of the ICD is in between the open hole completion and the situation with AICVs installed.

Figure 1

Performance curve comparisons of a passive ICD vs. AICV for oil, water and gas.

Reference page 5, figure 5 of OTC 28860.