Ensuring long-term optimum completion performance is important for the economic development of any field. As fields are now developed with fewer wells and in more technically challenging environment, new technologies are required to provide guidance and quantify the impact of completion design. This paper presents a new methodology in coupling ExxonMobil's reservoir simulator and a detailed well hydraulics simulator that simulates reservoir, wellbore tubing and wellbore annulus flow simultaneously. Case studies indicate that unique completions opportunities in optimizing completions options, especially inflow control devices, are captured by using the modeling capabilities
Completion strategies frequently include provisions tomaintain a uniform production profile along the wellbore,manage future risks (early water or gas breakthrough) and mitigate the potential for sand production, andimprove reservoir recovery.
Completion options include open hole, cased hole, inflow regulation devices (inflow/flow control devices and inflow valves), sand screens, or pre-drilled liners. Different from nodal based wellbore simulation in a conventional reservoir simulator, the proposed coupled well and reservoir simulation provides not only detailed information on the tubing and annulus flow and associated pressure drops in and throughout all completion types, but also the impact of completions on short and long term reservoir flow and recovery. Studies have shown the importance in utilizing the coupled model in both history matching and model prediction when advanced completions are applied. The significance of this new coupled approach is its ability to capture both flow dynamics through various completion options and reservoir performance
Introduction
In the past, top performing fields produced thousands of barrels a day from each of dozen of wells with completions lengths spanning tens to hundreds of feet. Today, we are using far fewer wells, each producing tens-of-thousands of barrels a day, from much longer and more complex completions often spanning thousands of feet, and all of this in more technically challenging environments. Obtaining superior well performance requires both a better understanding of the physics that controls well production as well as new technologies that take advantage of physics-based knowledge. ExxonMobil develops unique, physics-based modeling capabilities that can be applied during well planning, design, and production to deliver optimized well performance over a well's life-cycle 1.
Well completions are important means to optimize well performance throughout the entire well life, especially for challenging and remote environments. Commonly available completions options include open hole, cased hole perforated, slotted liner, inflow control devices (ICD), perforated liner, wire wrapped screen, gravel pack, frac pack, etc. For example, in ExxonMobil's Sakhalin-1 development, a combination of external isolation packers, inflow control devices, sand screens, and pre-drilled liners were used and the factors that were considered to configure the completions include rock strength, sand particle size, reservoir deliverability, reservoir description, etc.3 The challenging part from a completion design point of view is the understanding well inflow and outflow performance as a result of pressure drops due to multiphase flow in and throughout all completion types. More importantly, how the well inflow and outflow performance change over time. All these are the fundamentals for completion optimization - physics-based completion design, practices, and procedures for optimizing the selection, design, execution, and operations of wells in consideration of lifecycle risks and costs.
