Optimal Inflow Control Devices Configurations for Oil Rim Reservoirs
Authors: Mojaddam Zadeh Ali , Slotte Per Arne , Gyllensten Atle J. , Aasheim Robert , Årland Kristine 
Published: April 2012

Abstract
Judicious selection of intelligent completions will increase oil recovery andconstrain unwanted water and gas production from the reservoir.
Field experience, and results from extensive simulation studies, shows that thewater, oil and gas production are highly dependent on the type of inflowcontrol devices (ICDs) and the ICD configuration. Therefore, choosing the bestICD configuration is a key point to maximize the total oil production. In along horizontal well the primary objective is to maximize oil production fromthe whole completion interval and avoiding early breakthrough of gas or waterin parts of the well. In particular there is a need for compensating for thefriction induced pressure drop in the well which unchecked will result insignificantly higher production and early break through from the heel sectionsthan from the toe. The secondary objective is to limit flow from sections that, due to for instance heterogeneities, still suffer from early break through. Devices with autonomous valves should be especially suited for meeting thissecondary objective.
Traditionally, optimal ICD configurations have been selected using a trial anderror approach simulating different configurations. This time consumingapproach may result in non-optimal configurations since it is impossible totest all of the possibilities.
We have developed a semi-analytical mathematical model for calculating theoptimal ICD strengths for long horizontal wells in high permeable oil rimreservoirs. The mathematical model is utilized in a computer program whichfinds the optimal ICD configuration selecting ICDs from a pre-defined set ofoff-the shelf devices. The optimal configuration can be found in a fraction ofa second, and no flow simulations are needed.
Optimized ICDs with RCP valves (autonomous control devises) is compared withoptimized spiral control devices, and benefits and restrictions arepresented.

Introduction
The nature of oil rim reservoirs makes long horizontal wells an attractiveoption for increasing well-reservoir contact and reducing drawdown. However, increasing the horizontal wellbore length leads to some production challenges. In a long horizontal well with open hole completion, the drawdown in the heelsection of a well is much higher than the drawdown in the toe section. This isbecause of the higher cumulative frictional pressure loss in the heel sectionthan the toe. Thus, higher production in the heel than the toe section isexpected. Consequently, the inflow from the reservoir to the well and water/gasbreakthrough are non-uniform. This phenomenon gives partial water or gasbreakthrough and lower oil recovery and sweep efficiency.
Advanced completions in horizontal wells have been applied in recent years toavoid mentioned problems. Utilizing advanced completion gives the chance ofcontrolling unwanted fluid and optimizing of the oil production from a longhorizontal well. Inflow Control Devices (ICDs) as a type of advanced completionhave been used in producing wells to enhance oil production and restrictunwanted fluid from the reservoir to well. ICDs are passive control valveswhich are not adjustable or retrievable. Therefore, it is crucial to choose the best type andconfiguration for a single well before starting the production.